Introduction to Echocardiography

Transcription

1 5 Introduction to Echocardiography Raymond F. Stainback Historical Perspective Indications Two-Dimensional Imaging Doppler Examination and Hemodynamics Parametric Imaging Methods for Improving Two-Dimensional Imaging Three-Dimensional Echocardiography Summary Key Points Echocardiography is a safe, noninvasive, and widely available method that often provides a definitive anatomic and hemodynamic diagnosis and guides medical management. lthough long viewed as clinically mature, echocardiography has undergone further revolutionary advances during the past 10 years, including not only technologic breakthroughs but also new clinical applications for older techniques. The recent explosion of potential add-on techniques presents echocardiographers with challenging questions about what constitutes real clinical progress and what techniques should be incorporated into the standard examination protocol. y becoming familiar with their clinical indications, echocardiographers can use these techniques selectively, on an as-needed basis, and thus streamline patient care. ecause of increased availability and clinical utility, echocardiography s usage has greatly expanded in recent years. However, echocardiography demands a major commitment in terms of time, personnel, ongoing training, and technology. n understanding of the physics of ultrasound is essential for performing echocardiography examinations and interpreting their results. comprehensive transthoracic echocardiography examination includes systematic acquisition of a set of twodimensional and M-mode views, along with spectral Doppler and color Doppler evaluation of the intrathoracic cardiovascular structures (e.g., the myocardium, cardiac valves, pericardium, and great vessels). Transthoracic and transesophageal echocardiography are frequently used as complementary imaging techniques. ccordingly, the advantages and disadvantages of these two methods should be understood. Newer imaging modalities that are being introduced into the standard examination include contrast echocardiography, harmonic imaging modalities, parametric imaging modes, and selected three-dimensional techniques. Echocardiography examinations using standardized and novel imaging modes are frequently applied to a wide range of new clinical treatments, including assessment of left ventricular assist devices. In this growing field, important quality assurance measures have evolved along with imaging techniques to improve the quality of delivered care. Echocardiography is a safe, noninvasive, and widely available method that often provides a definitive anatomic and hemodynamic diagnosis and guides medical management. The modern echocardiography machine is a highly sophisticated, multimodal device that is an integral part of any cardiovascular care center. Ultimately, however, echocardiography remains operator-dependent and subject to the physical principles of ultrasound. Efficient usage of this technology depends on basic training 1 4 in imaging techniques, machine settings, new technology, continuing education, quality assurance, data storage and retrieval, 5 and reporting standards. 6 9 ccordingly, this chapter discusses the fundamental physical principles of cardiovascular ultrasonography, with an emphasis on classic two-dimensional (2D) and Doppler methods for transthoracic (TTE) and transesophageal (TEE) echocardiography. This discussion will help echocardiographers design protocols for performing TTE or TEE 2D and Doppler examinations and will provide a basis for understanding the more advanced imaging techniques. For certain echocardiography-derived measurements of cardiac mass, volume, area, and dimensions, interested readers should refer to other echocardiography chapters in this book or to a comprehensive echocardiography textbook. Historical Perspective The first clinical cardiac ultrasound examination was performed in 1953 by two Swedish researchers, Inge Edler, a physician, and Hellmuth Hertz, an engineer, who used an 93

2 94 chapter 5 ultrasonic reflectoscope obtained from a shipyard and designed to detect structural defects in boats. 10,11 The first images consisted of -mode signals that were hard to interpret and often misleading. However, the clinical impact of these images and their subsequent refinements was so significant that, in 1970, Elder and Hertz received the Lasker Prize in Medicine. y that time, the clinical aspects of their technique were based primarily on M-mode examination. 12 During the 1970s, cardiology was revolutionized by further advances in surface planar imaging techniques (oscillating mechanical sector scanners, 13 linear array transducers, 14 and phased array transducers 15,16 ) which provided recognizable, moving, cross-sectional images of the cardiac anatomy for the first time. M-mode 17 and then real-time moving-image capability 18 was quickly adapted to TEE probes 17,18 providing new higher-resolution esophageal imaging windows on the heart and aorta. Clinical spectral Doppler echocardiography techniques were introduced in the early 1980s. 19,20 y 1986, the concept of an integrated M-mode, 2D, and spectral Doppler examination for use in clinical practice had fully taken shape. 21 This breakthrough was soon followed by the addition of color-flow Doppler, biplane TEE, and then multiplane TEE imaging techniques. 30,31 Clinical pplications Throughout the 1980s and 1990s, the important role of 2D and Doppler echocardiography in the diagnosis and management of many cardiovascular conditions became clearly established, to the point of essentially replacing interventional hemodynamic testing in many cases. (The echocardiography indications are listed in Table 5.1.) From the late 1980s 32 through the 1990s, a large number of clinical studies established echocardiography as a viable noninvasive means of identifying diastolic dysfunction by analyzing several routinely acquired blood-flow spectral Doppler, color M- mode, 37 and tissue Doppler imaging (TDI) parameters. This led to a widespread realization that echocardiography can readily identify a large, previously unrecognized subset of patients with congestive heart failure resulting from diastolic dysfunction despite a normal or near-normal left ventricular ejection fraction. 38 The comprehensive Doppler examination can frequently help distinguish between certain forms of diastolic dysfunction (e.g., constrictive, 35 restrictive, hypertrophic, 42 and ischemic 43 cardiomyopathies) and can estimate the left atrial pressure, assess disease prognosis, 40,47 53 and follow up the response to therapy Ongoing refinements include the use of increasingly sensitive and specific anatomic and physiologic parameters to assess not only diastolic heart failure but also ventricular mass, 57 systolic function, 58 and valvular heart disease. Technologic reakthroughs and Evolving Clinical pplications lthough long viewed as clinically mature, echocardiography has undergone further revolutionary advances during the past 10 years, including not only technologic breakthroughs but also new clinical applications for older techniques. 59 The hemodynamic assessment of left ventricular assist devices (LVDs) is just one example of an emerging TLE 5.1. Echocardiography indications: general categories Patients with signs or symptoms of cardiovascular disease Valvular heart disease (potentially pathologic murmurs) Endocarditis Ischemic heart disease Chest pain syndromes (suspected to be cardiopulmonary in origin) Congestive heart failure (systolic or diastolic) Cardiomyopathies Pericardial disease Hypertension/hypertensive heart disease trial fibrillation/flutter Cardioembolic disease Disease of the aorta Suspected cardiac neoplasm Congenital heart disease Hemodynamic instability/critically ill patients Suspected device malfunction (prosthetic valve, pacemaker lead, ventricular assist device) Invasive procedures (procedure monitoring, postprocedure assessment) Cardiovascular surgery (intraoperative) Pericardiocentesis Cardiac biopsy Percutaneous SD closure (TEE/ICE) Electrophysiology, selected (TEE/ICE, lead extraction, RF) Percutaneous valve procedures Screening echocardiography Marfan syndrome (asymptomatic family members) Hypertrophic cardiomyopathy (asymptomatic family members) Familial dilated cardiomyopathy (asymptomatic family members) Cardiotoxic chemotherapy exposure (pre- and posttreatment) SD, atrial septal defect; ICE, intracardiac echocardiography; RF, radiofrequency ablation; TEE, transesophageal echocardiography. clinical focus that uses echocardiography for research and patient management In the 1990s, exercise and pharmacologic stress echocardiography came into widespread clinical use for the assessment of myocardial ischemia, myocardial viability, and valvular heart disease The accuracy of stress echocardiography continues to undergo refinement with the incorporation of newer imaging and Doppler techniques (see the sections on Tissue-Doppler Imaging, Contrast Harmonics, and Three-Dimensional Echocardiography, below). With the development of intravascular and intracardiac ultrasonography, the boundary between noninvasive and invasive imaging techniques became blurred. Intravascular ultrasonography (IVUS), 78 uses a shallow, high-resolution radial image display (Fig. 5.1) that is ideal for assessing vascular structures Ongoing technologic refinements include commercially available real-time, three-dimensional (3D) echocardiography (Figs. 5.10C, 5.45, 5.48, and 5.49),* miniature handheld ultrasonic devices (Fig. 5.2), and intracardiac echocardiography (ICE) The latter * To preserve the sequence of a typical TTE or TEE examination, the figures in this chapter are not always numbered sequentially, according to their order of appearance in the text.

3 introduction to echocardiography 95 FIGURE 5.1. Intravascular ultrasound image from within a right coronary artery after deployment of a stent. Luminal dimensions are in millimeters. Submillimeter structures include a bright plaque calcification (arrowhead) and a coronary stent wire in cross section (arrow). technology uses a phased array transducer and a planar imaging-sector display analogous to a small intravascular TEE probe that is inserted into the circulation percutaneously. This small ultrasound catheter has, in fact, been employed as a TEE probe experimentally in tiny subjects. 103 New clinical indications for ICE include guidance of electrophysiologic radiofrequency ablation procedures, 104 deployment of percutaneous atrial septal occluders 101 (Fig. 5.3), and monitoring of other interventional procedures. 102 ecause IVUS and ICE are invasive techniques, they will not be discussed further in this chapter. Novel parametric imaging modes enable rapid depiction and quantitation of intramyocardial functional heterogeneity. Real-time, color-coded TDI 105 (Figs ) and derived strain (Fig. 5.46) and strain-rate image data (Fig. 5.47) are now commercially available because of increased processing speeds. These new Doppler methods for analyzing myocardial motion produce familiar anatomic images with superimposed physiologic data (a color-encoded parametric display). The combined anatomic and physiologic data are stored digitally for either real-time or retrospective off-line analysis. The clinical utility of parametric imaging techniques (myocardial Doppler imaging) will increase as more reference values and validation studies become available for the assessment of cardiomyopathies, coronary artery disease, 113,114 ventricular dyssynchrony 115,116 and other pathologies. Tissue-Doppler-imaging derived outcome indices are being developed 117 to improve candidate selection for cardiac resynchronization therapy (CRT) 115, (Fig. 5.44) or CRT refinement. 117,122 Echocardiography contrast agents (intravenously delivered, highly echoic microbubbles) and harmonic imaging modalities (see below) have greatly improved the diagnostic accuracy of left ventricular functional assessment during routine and stress echocardiography. Microbubbles improve endomyocardial detection by opacifying the blood pool. Currently, two different echocardiography contrast agents (microbubbles) are approved by the United States Food and Drug dministration (FD) for this indication. Left ventricular opacification is possible only when microbubbles persist within the imaging field during imaging. Conversely, another application of microbubbles, myocardial contrast echocardiography (MCE) uses ultrasound energy to burst microbubbles within an area of interest. Intermittent observations regarding the rate of myocardial microbubble replenishment allow myocardial perfusion characteristics to be determined. lthough FD approval is still pending, recent clinical research suggests that MCE is a potentially important emerging clinical modality Experimental studies have also shown that acoustically active intravenous microbubbles with surface ligands may permit targeted pathologyspecific ultrasound imaging. 127,128 dditionally, microbubbles may eventually also become vehicles for the localized delivery of pharmacologic or gene therapy. 129 The recent explosion of potential add-on techniques presents echocardiographers with challenging questions about what constitutes real clinical progress and what techniques should be incorporated into the standard examination protocol. y becoming familiar with their clinical indications, echocardiographers can use these techniques selectively, on an as-needed basis, and thus streamline patient care. FIGURE 5.2. Small handheld echocardiography device (arrow) being used at the bedside.

4 96 chapter 5 FIGURE 5.3. () Fluoroscopic image of an intracardiac echocardiography (ICE) device in the right atrium (arrow) just before release of an atrial septal occluder (arrowhead) from its deployment catheter. () ICE ultrasound image obtained in the same patient. L, left atrium; R, right atrium; R, right atrial appendage. Indications The indications for echocardiography are increasingly prominent in evidenced-based clinical practice guidelines lthough these indications are too extensive to review here, Table 5.1 summarizes their general categories. Indeed, echocardiography indications are so numerous that one might more appropriately ask when this method should not be used. ecause of increased availability and clinical utility, echocardiography s usage has greatly expanded in recent years. However, echocardiography demands a major commitment in terms of time, personnel, ongoing training, and technology. It is a valuable resource that must be deployed appropriately. Echocardiography is not indicated for situations in which it would not influence patient care; nor is it indicated for asymptomatic patients in whom detection of mild subclinical lesions or misleading imaging artifacts could cause harm or increase cost because of a need for subsequent confirmatory procedures. No randomized clinical trials assessing the outcome of diagnostic imaging tests are available, 132 so expert opinion is based on summaries of clinical observational studies. 132, Consensus opinion regarding the inclusion of additional new imaging modalities (e.g., contrast, 3D, tissue harmonics, TDI) is not addressed in recent echocardiography guideline statements. However, clinical guidelines do address the frequency with which indicated examinations should be repeated. Clinical research frequently relies on quantitative echocardiography methods 140 that may go beyond the scope of routine clinical protocols. Echocardiography as a Screening Tool Echocardiography is not generally recommended as a screening tool for asymptomatic patients who lack signs (on physical examination, chest roentgenography, electrocardiography, or other imaging procedures) or symptoms of cardiovascular disease. Important exceptions include screening of patients with a family history of genetically transmitted cardiovascular disease. Examples include asymptomatic first-degree relatives of patients with Marfan syndrome, other familial aortic aneurysms, hypertrophic cardiomyopathy, or suspected familial dilated cardiomyopathy. In addition, echocardiography may be used for baseline and follow-up evaluation of left ventricular function in asymptomatic patients who are to receive potentially cardiotoxic chemotherapeutic agents. 132, Transthoracic Versus Transesophageal Echocardiography ecause almost all the imaging modalities available for TTE are also applicable to TEE, some confusion may exist regarding the relative merits of these two methods. In fact, they are complementary approaches, whose advantages and disadvantages vary depending on the diagnosis and imaging conditions. ecause TEE is semi-invasive and typically requires conscious sedation, it is usually preceded and guided by TTE. ecause of numerous possible imaging windows, TTE often provides a superior and more comprehensive Doppler examination. It can also provide a superior analysis of ventricular wall motion, particularly when echocardiography contrast agents are used. Occasionally, a comprehensive surface echocardiogram will obviate the need for TEE. However, even in the best of hands, a surface examination may be technically inadequate or it may raise clinical suspicion concerning an underlying pathologic condition that requires further evaluation by TEE. The transesophageal approach permits superior anatomic evaluation of the posterior cardiac structures in most cases and optimal Doppler evaluation under special circumstances (e.g., assess-

5 introduction to echocardiography 97 ment of periprosthetic mitral regurgitation, left atrial appendage assessment, congenital heart disease; or for aortic valve planimetry). In the intensive care unit (ICU), TEE may be useful when surface echocardiography is not logistically possible (e.g., in an intubated patient whose condition is unstable). ecause TEE does not invade the operative field, it has largely supplanted intraoperative epicardial imaging and is widely used for hemodynamic monitoring during cardiovascular surgery. t the end of cardiopulmonary bypass, TEE may be used to assess congenital cardiac repairs, complex heart valve procedures, left ventricular myomectomies, tumor removals, LVD implants, and aortic dissections involving the aortic root. ccordingly, a separate field of perioperative (intraoperative) TEE has emerged, as practiced by dedicated cardiologists, specially trained cardiovascular anesthesiologists, 141,142 and some cardiovascular surgeons. Two-Dimensional Imaging The Physics of Ultrasound n understanding of the physics of ultrasound is essential for performing echocardiography examinations and interpreting their results. Sound comprises the directional (longitudinal) propagation of compressions and rarefactions of an acoustic medium (air, tissues, fluids). The frequency (number per unit time) of these compressions and rarefactions is reported in cycles per second or hertz (Hz) (1 Hz = 1 cycle/s). The spectrum of sounds audible by the human ear ranges from 20 to 20,000 Hz. The term ultrasound denotes sounds that are higher (>20 khz) than the human audible range. The propagation time (in seconds) required for sound energy to complete 1 cycle of compression and rarefaction is called a period. In diagnostic ultrasonography, a typical period ranges from 0.1 to 0.5 μs, depending on the sound frequency. Period and frequency are inversely related (period = 1/frequency). The wavelength is the propagation length, within a medium, of one complete cycle. Frequency and wavelength are also inversely related. n echograph machine works by electrically stimulating a piezoelectric element, called a crystal or ceramic, that is housed within a transducer (Fig. 5.4). Mechanical deformation of the crystal produces ultrasound waves that are transmitted into the patient s body, where they are scattered, are reflected, or eventually fade (attenuate). The energy from reflected ultrasound (echoes) deforms the transducer s piezoelectric crystal, creating a faint electrical impulse that is amplified, processed, recorded, and displayed in the familiar formats seen throughout this chapter. Echocardiographic image resolution (clarity, or the degree to which adjacent points in an image may be distinguished as separate) is linked to ultrasound frequency. To clearly show thin structures such as the endocardium, the valve apparatus, and small mass lesions, basic surface echocardiograms require an axial and lateral spatial resolution of 1 to 2 mm. n ultrasound wavelength of <1 mm is necessary to achieve that resolution. t all frequencies, the speed of ultrasound (propagation velocity) in soft tissue is approximately 1,540 ms (1.54 mm/ μs). t a frequency of 1 MHz (1 million cycles per second), sound has a wavelength of 1.54 mm in soft tissue. ecause wavelength and frequency are inversely related, the wavelength of a 2-MHz signal is half that of a 1-MHz signal (1.54 mm/2 = 0.77 mm). This wavelength is less than the necessary spatial resolution, which is why a minimum FIGURE 5.4. () roadband combined imaging and Doppler transducer with imaging gel and index mark (arrow). () Nonimaging Pedoff transducer for dedicated continuous-wave Doppler examination.

6 98 chapter 5 TLE 5.2. Cardiovascular ultrasound modalities Practical image xial resolution Modality f (MHz) depth (cm) (mm) TTE TEE ICE IVUS Depth, maximum imaging depth; ICE, intracardiac ultrasound; IVUS, intravascular ultrasound; TEE, transesophageal echocardiography; TTE, transthoracic echocardiography; f = ultrasound frequency. Note: axial resolution is also affected by emitted pulse length and pulse duration. Indicated depth and resolution values are estimates; lateral resolution (not shown) is poorer than axial resolution. frequency of 2 MHz is required for surface echocardiography. Higher ultrasound frequencies (20 40 MHz) produce even finer degrees of spatial resolution, allowing even ultrastructural vascular layers to be measured with IVUS (Fig. 5.1). Reflected soundwaves may produce a wide variety of imaging artifacts that can either be recognized as such or can lead to erroneous interpretation. One reason for these artifacts is that the sound energy gradually attenuates as it becomes more distant from its source. This attenuation eventually makes it impossible for the operator to distinguish reflected ultrasound signals from random background noise at a limiting depth of interrogation. However, signal attenuation is directly related to soundwave frequency, so it is more common at higher frequencies. High-frequency (high-resolution) imaging is possible only at shallower imaging depths (low tissue penetration). This interplay between ultrasound wavelengths, image resolution, and signal attenuation explains why medically useful ultrasonography is constrained to a frequency range of 2 to 40 MHz and to certain imaging depths. Transthoracic echocardiography operates at one end of an imaging depth range of approximately 2 to 24 cm, and IVUS (Fig. 5.1) operates at the other end (<1 cm). Transesophageal echocardiography (Fig. 5.26) and ICE (Fig. 5.3) operate in the middle range (Table 5.2). Two-dimensional images are created from pulses of ultrasound. The pulse repetition frequency (in khz) is inversely related to imaging depth. long with the wavelength, the pulse duration and pulse length also affect image resolution. xial resolution (in which resolving points are aligned or in parallel with the ultrasound beam) is superior to lateral resolution (in which resolving points are perpendicular to the ultrasound beam). Echocardiography machines produced in the 1980s operated with single-frequency transducers (2.5, 4, and 7 MHz) that had to be manually changed, depending on imagingdepth requirements (deep vs. shallow, in an adult vs. a pediatric patient). Modern transducers are broadband, or multifrequency, and can better balance near- and far-field imaging by sending and receiving multiple frequencies simultaneously. Differences in acoustic impedances related to density and stiffness between adjacent media (e.g., tissue planes) determine the extent to which soundwaves are either reflected or transmitted. lood, myocytes, collagen, and adipose tissue differ only slightly with respect to acoustic impedance, and this fact forms the basis for echocardiographic imaging based on subtle reflections at tissue interfaces. However, the heart is surrounded by two strong ultrasound attenuators lung and bone both of which tend to variably reflect, scatter (lung), or absorb (bone) ultrasound energy. This set of circumstances poses a major (and in some patients insurmountable) problem for cardiac ultrasound imaging. The key to optimal imaging is the sonographer s degree of experience and the machine s technologic ability to extract maximal usable information even from highly attenuated signals (see Contrast Harmonics, below). s discussed above, TEE can be used adjunctively when surface echocardiography attenuation artifacts prevent adequate examination. For further details about ultrasound physics, a number of excellent references are available Transthoracic Echocardiography Ordering an Echocardiogram comprehensive TTE examination includes systematic acquisition of a set of 2D and M-mode views, along with spectral Doppler and color Doppler evaluation of the intrathoracic cardiovascular structures (e.g., the myocardium, cardiac valves, pericardium, and great vessels). For ease of communication, ordering a comprehensive examination is sometimes casually called getting an echo. The word echo is potentially confusing for order-entry personnel and sonographers, however, because the necessary extent of the examination may be unclear. n initial comprehensive examination, including 2D imaging and Doppler evaluation, is required for most patients. limited 2D (anatomic-only) exam is reserved for following up certain previously diagnosed pathologic conditions. To ensure that the clinical question is addressed, all orders for an echocardiogram should include the exact indication for the study, pertinent details of the patient s cardiovascular medical and surgical history, and pertinent physical findings when available. The patient s age, sex, height, weight, and blood pressure at the time of the examination should also be recorded. If possible, previous echocardiography exams should be reviewed. 5 Scanning Techniques Without proper scanning procedures and machine settings, even the most advanced imaging devices may prove inadequate. ppropriate patient positioning is an important element of good sonography. In the echocardiography laboratory, optimal results are generally obtained with the subject lying comfortably in the left lateral decubitus position, but this position is not always attainable by intubated, wounded, or otherwise ill patients. s in cardiac auscultation, the left lateral decubitus position allows gravity to decrease the distance from the myocardium to the listening device (transducer) by reducing the amount of interposed lung. To enable full access to apical windows and avoid apical foreshortening of views, one should use a special echocardiography bed with a pull-away section (Fig. 5.5). Extension of the patient s left arm, combined with gentle gravity-induced left lateral thoracic extension, causes the ribs to spread slightly, minimizing acoustic shadowing. Depending on the body habitus,

7 introduction to echocardiography 99 displayed on the right. In predominantly short-axis or crosssectional views, left-sided structures appear to the right of the screen, and right-sided structures appear to the left, as if the viewer were standing at the foot of a supine patient, looking toward the head. ecause the heart lies obliquely in the chest, this is only a rough comparison, but it is consistent with display standards for other types of axial imaging (i.e., computed tomography and magnetic resonance imaging). small icon (index mark), which varies depending on the manufacturer, should appear to the right of the image sector (Fig. 5.6). This icon corresponds to a ridge or groove (Fig. 5.4) placed on one side of the otherwise symmetric imaging transducer. In TTE, anterior structures appear at the top of the screen, and more posterior structures appear toward the bottom (Fig. 5.6). FIGURE 5.5. Sonographer obtaining apical views, using a special echocardiography bed with a pull-away section (bracket), which facilitates proper positioning of the transducer. however, other positions (e.g., supine, semiupright, and right lateral decubitus) may be used to optimize certain views. ecause the typical examination lasts for 30 to 45 minutes (not including the setup time), the sonographer should be seated comfortably and ergonometrically, typically on the patient s left side (Fig. 5.5). lternatively, scanning from the patient s right side has some advantages, but it requires the sonographer to reach around the patient s thorax, and this may be problematic. coupling medium (ultrasonographic gel) (Fig. 5.4) is used to maximize ultrasound transmission between the transducer and the patient s body, in part by eliminating air interfaces. reathing instructions are often crucial. For example, breathe out and hold can transiently eliminate lung attenuation, bringing the heart into full view. Small breath in and hold can elevate the diaphragm and perhaps raise a rib-shadowed inferior left ventricular wall into view (apical two-chamber view). During normal breathing, the heart moves phasically across the otherwise stationary imaging plane. This translational motion causes endocardial segments (and other structures) recorded during systole to be from a different anatomic location than those recorded during diastole, leading to erroneous analyses of segmental wall motion and anatomic volume measurements. The sonographer can often coach a patient to stop breathing at an ideal point in the respiratory cycle. When data are then acquired during a brief breath-hold, the respiratory component of cardiac translation, a common pitfall of real-time planar imaging, can be eliminated. The Planar Image Display The planar image is sector-shaped. Ultrasound emanates from the smallest portion of the displayed sector, which appears at the top of the screen in echocardiograms of adults. The broader, more distant portion of the image, derived from diverging echoes, appears at the bottom of the screen. ecause the transducer position varies greatly throughout an examination, spatial orientation entails a distinct learning curve related to poorly visualized adjacent thoracic anatomic landmarks. In predominantly long-axis views, caudal structures appear to the left of the screen, and cephalad structures are Transthoracic (Surface) Echocardiography Views PRSTERNL LONG-XIS (PSLX) VIEW Left Ventricular Inflow and Outflow Tracts. The surface examination begins with a parasternal long-axis view of the left ventricular inflow and outflow tracts and the aortic root. The transducer is usually placed adjacent to the sternum in the left third or fourth intercostal space, although optimal patient-imaging window positions may vary greatly from one patient to another. n initial highdepth setting is selected to include anatomic features posterior to the left ventricular chamber (Fig. 5.6). Subsequent shallower, optimized views are focused on the left ventricular myocardium and the valves (Figs. 5.7 to 5.9). Important measurements (e.g., left ventricular end-diastolic septal- and posterior-wall thickness; left ventricular enddiastolic and end-systolic internal chamber diameters) are obtained from a carefully selected midline imaging plane that bisects both the aortic and the mitral valve annuli during diastole (Fig. 5.7) and systole (Fig. 5.7). common pitfall is acquisition and measurement of off-axis parasternal views that yield erroneously small ventricular FIGURE 5.6. Parasternal long-axis view at increased depth. n index mark (arrowhead) always appears to the right of the image sector. *, posterior pericardial effusion; **, pleural effusion; ao, ascending aorta; do, descending thoracic aorta; L, left atrium; LV, left ventricle; RVOT, right ventricular outflow tract; Vb, vertebral body.

8 100 chapter 5 FIGURE 5.7. Parasternal long-axis view at a shallower, optimized depth. () Diastolic image with the mitral valve (double arrows) open and the aortic valve (single arrow) closed. o, aortic root; do, descending thoracic aorta; L, left atrium; LV, left ventricle; RVOT, right ventricular outflow tract. () Systolic image with the mitral valve closed and the aortic valve open. *, left ventricular outflow tract; single arrow, mitral valve chordae tendineae; double-headed arrow, left ventricular outflow-tract dimension/diameter for calculating left ventricular outflow-tract flow. Line a indicates the orthogonal image plane shown in Figure Line b indicates the orthogonal image plane shown in Figure Line c indicates the orthogonal image plane shown in Figure diameters and erroneously large myocardial thicknesses. In addition to obtaining a midline image, the sonographer should also scan incrementally toward both the medial and lateral aspects of the aortic and mitral valves to exclude pathology along the extent of each valve s leaflet coaptation zone. Generally, measurements of parasternal diameters should be obtained from 2D views (as opposed to M-mode). lthough M-mode measurements have certain advantages (fast sample rates and improved temporal resolution), their use can be limited by oblique cut planes imposed by patient imaging-window constraints. The ascending aorta should be imaged and measured if possible. This may require a separate parasternal long-axis view at a more cephalad transducer position (Fig. 5.8). Note that aortic measurements distal to the aortic valve leaflets are obtained during diastole. Right Ventricular Inflow Tract (Fig. 5.9). With the transducer in an optimized left-sided, parasternal long-axis position, a subtle leftward and anterior tilting motion often easily produces the right ventricular inflow tract view, which includes the tricuspid valve and right atrium. FIGURE 5.8. Parasternal long-axis view at the level of the aortic root and ascending aorta. The double arrows indicate the mitral valve anterior leaflet. Measurements of the proximal aorta are obtained during diastole (with the aortic valve closed). a, ortic root diameter, sinus of Valsalva level; b, sinotubular junction diameter; c, ascending aortic diameter. FIGURE 5.9. Parasternal long-axis view of the right ventricular inflow tract and tricuspid valve. rrow, coronary sinus., tricuspid valve anterior leaflet; I, inferior vena caval ostium; P, tricuspid valve posterior leaflet; R, right atrium; RV, right ventricle. (Note: With more septal angulation, the tricuspid valve anterior and septal leaflets may be seen in this view.)

9 introduction to echocardiography 101 PRSTERNL SHORT-XIS VIEW Left Ventricle (Fig. 5.10). With the transducer in an optimized left-sided parasternal long-axis position, a 90-degree clockwise transducer rotation will produce left ventricular short-axis views. These breadloaf slices should be obtained in the region of the apex (not shown), at the midpapillary muscle level (Fig. 5.10), and through the basal segments at the chordal and mitral valve leaflet level (Fig. 5.10). This approach will show the basal, middle, and apical coronary artery distributions that correspond to the standard 17-segment model. 6 The left ventricular short-axis view should be perpendicular to the left ventricular long axis. Ideal parasternal left ventricular short-axis views are not obtainable when the left ventricle s major axis within the chest is located in an extreme anterior-to-posterior position ( horizontal heart); in such patients, only limited oblique or oval-shaped shortaxis views are possible, and these may be difficult to interpret. ortic, Tricuspid, and Pulmonary Valve Level (Fig. 5.11). Further cephalad positioning of the imaging plane above the left ventricular level reveals the aortic valve in the short-axis view. With that valve centered in the imaging sector, subtle transducer adjustments will show the three aortic cusps in perfect symmetry during diastolic closure. Color Doppler examination at this level (not shown) will detect aortic regurgitation. Slightly cephalad, when imaging conditions are ideal (in pediatric cases and frequently in adults), the left and right coronary ostial locations within the aortic root can be recorded. The adjacent tricuspid valve, atria, interatrial septum, and right ventricular outflow tract are also visualized in this view. The pulmonary valve s long axis (perpendicular to the aortic valve) is often not optimized at the aortic leaflet level and is best seen in a separate, slightly more cephalad imaging plane just above the aortic valve cusps. ranching of the left and right pulmonary arteries should be documented if possible (Fig. 5.11). This view is important for Doppler evaulation of the right ventricular out flow tract (Fig. 5.12). C FIGURE () Parasternal short-axis view of the left ventricle at the papillary muscle level. L, anterolateral papillary muscle; PM, posterolateral papillary muscle. Line a indicates the orthogonal image plane shown in Figure 5.13 (apical four-chamber view). Line b indicates the orthogonal image plane shown in Figures 5.7 and 5.13E (parasternal long-axis views and apical three-chamber). Line c indicates the orthogonal image plane shown in Figure 5.13D (apical two-chamber view). () Parasternal short-axis view, mitral valve level. 1, anterior segment of the mitral anterior leaflet; 2, middle segment of the mitral anterior leaflet; 3, posterior segment of the mitral anterior leaflet; L, anterolateral commissure; P 1, anterior scallop of mitral valve posterior leaflet; P 2, middle scallop of the mitral valve posterior leaflet; P 3, posterior scallop of the mitral valve posterior leaflet; PM, posteromedial commissure; RVOT, right ventricular outflow tract. (C) Three-dimensional surface-rendering mode from the cut plane shown in Figure 5.10, looking toward the mitral valve. The arrow labels are the same as in. L, anterolateral commissure; PM, posteromedial commissure; RVOT, right ventricular outflow tract; *, left ventricular outflow tract.

10 102 chapter 5 PICL FOUR-CHMER VIEW (Fig. 5.13) This view is a good starting point from which one can easily attain the other apical views by simply rotating the transducer. The cardiac apex and left ventricular major axis should be centered within the imaging sector. The interventricular septum appears on the left side of the sector, with the opposing lateral wall on the right side. The other apical views are obtained by rotating the transducer counter clockwise around the central axis. This view is used for Doppler evaluation of the mitral valve (Fig. 5.14), the pulmonary veins (Fig. 5.15), myocardial tissue Doppler (Fig. 5.16), and trisuspid valve (Fig. 5.17). PICL FIVE-CHMER VIEW (Fig. 5.13) ngling the transducer slightly anteriorly from the fourchamber view position produces the apical five-chamber view, which shows the anterior interventricular septum, the left ventricular outflow tract, and an oblique cut across the aortic valve. PICL FOUR-CHMER VIEW: CORONRY SINUS LEVEL (Fig C) slight inferior angulation of the imaging plane from the apical four-chamber view will show the coronary sinus and the inferior interventricular septum. PICL TWO-CHMER VIEW (Fig. 5.13D) y rotating the transducer 90 degrees counterclockwise from the apical four-chamber view, one can see the left ventricular anterior and inferior walls in opposition, as well as the mitral valve and left atrium (two chambers). FIGURE () Parasternal short-axis view, aortic valve level. rrowhead, interatrial septum; single arrow, pulmonary valve; double arrows, tricuspid valve. L, left coronary cusp of the aortic valve; L, left atrium; N, noncoronary cusp of the aortic valve; R, right coronary cusp of the aortic valve; P, pulmonary artery; R, right atrium. () Parasternal short-axis view, pulmonary artery (P) level. Double-headed arrow, pulmonary annulus dimension for right ventricular outflow-tract flow assessment. o, ascending aorta; L, left P at the pulmonary bifurcation; R, right P at the pulmonary bifurcation; RVOT, right ventricular outflow tract. Note: The right P is directly posterior to the ascending aorta. pical Views (Fig. 5.13) With the patient carefully positioned, placing the transducer over the palpated point of the left ventricular apical impulse is often a good way to start looking for apical windows. If the transducer is not placed exactly over the cardiac apex and properly aligned with the left ventricular major axis, apical foreshortening will occur. ecause this condition impairs ventricular segmental wall-motion analysis and volume assessment, avoidance of apical foreshortening is a crucial aspect of accurate scanning. PICL THREE-CHMER (LONG-XIS) VIEW (Fig. 5.13E) n additional transducer rotation, approximately 30 degrees counterclockwise past the apical two-chamber view, will bring the right ventricular outflow tract, left ventricular outflow tract, and aortic valve (long axis) into view. nalogous to the parasternal long-axis view, the apical threechamber view shows similar anatomic features but focuses on the left ventricular endocardium. This view (along with the apical five-chamber view) is important for spectral Doppler evaluation of the left ventricular outflow tract (Fig. 5.18). Contrast echocardiography for improved endocardial definition (Fig. 5.19) is performed in apical views. Subcostal Views (Figs and 5.21) While the patient lies supine with relaxed abdominal muscles (the knees may be slightly flexed), the flat side of the transducer is placed on the abdomen. The transducer surface is placed in the immediate right subcostal or mid-subxiphoid region, pointing toward the right shoulder. Gentle downward pressure produces the subcostal four-chamber view (Fig. 5.20). Clockwise transducer rotation produces the subcostal short-axis views (Fig. 5.20). The subcostal view is important for evaluating right ventricular function, left ventricular segmental wall motion (of the septum and lateral wall), the interatrial septum, and pericardial effusion. This view may be excellent in patients with obstructive lung disease (hyperexpanded lungs) and can salvage an otherwise technically

11 introduction to echocardiography 103 C FIGURE () Color-flow Doppler image of the right ventricular outflow tract and pulmonary valve: yellow (aliased) color is seen at the pulmonary valve (arrow). () Color-flow Doppler image of the pulmonary trunk, showing a normal pulmonary artery bifurcation. This is an important view for excluding a patent ductus arteriosus or proximal pulmonary artery stenosis (not present in this normal example). L, left pulmonary artery; R, right pulmonary artery. (C) Pulsed Doppler view of right ventricular outflow at the level of the D pulmonary valve annulus. Note the valve-closure artifact (arrow) and absence of an opening artifact, indicating a good sample-volume position. Note the automated time-velocity integral (TVI = m or 14.1 cm, arrowhead) from electronic outlining of the spectral Doppler envelope (dotted curve). (D) Continuous-wave Doppler image, right ventricular outflow tract (pulmonary valve). Note the typical small pulmonary valve opening (left arrow) and closing (right arrow) artifacts. difficult exam because multiple subcostal views can frequently be attained. The inferior vena cava should be imaged along its long axis as it crosses the diaphragm and enters the right atrium (Fig. 5.21). Dynamic motion of the inferior vena cava during normal respiration and while the patient gently sniffs is used to assess the right atrial pressure (Fig. 5.21; Table 5.3). The hepatic vein is also imaged along its long axis for coaxial pulsed Doppler interrogation (Fig. 5.21C). The upper abdominal aorta, lying alongside the inferior vena cava, can be imaged in the short- and long-axis orientations (Fig. 5.22). From this position, pulsed Doppler examination of the descending thoracic aorta is used to assess the severity of aortic regurgitation. The subcostal four-chamber view is used for analyzing feasibility and the needle angle and depth required for percutaneous pericardiocentesis procedures. (Note: Real-time echocardiography guidance of percutaneous pericardiocentesis is from the apical four-chamber view, remote from the sterile needle site.) Suprasternal Notch In most (but not all) patients, the aortic arch may be visualized along its short (not shown) and long axes (Fig. 5.23). lthough a patient s body habitus may cause considerable variation in image quality, this view should be attempted. It can be used to detect an aortic arch aneurysm or dissection. Pulsed Doppler interrogation in the region of the proximal descending aorta is used to assess the severity of aortic insufficiency. Color Doppler and continuous-wave (CW) Doppler in the same region (ligamentum arteriosum) can detect coarctation of the aorta and patent ductus arteriosus, which are important potential incidental diagnoses. Modified Views Sonographers should be familiar with certain modified views (not shown) that are obtained with the patient supine or in the right lateral decubitus position. Such views include the superior right parasternal window (for visualizing the superior vena cava and for CW Doppler evaluation of aortic valve stenosis) and a modified right apical four-chamber view (for accurate assessment of tricuspid regurgitation and for ventricular visualization when apical windows are poor). posterior thoracic window may be useful for visualizing the descending thoracic aorta when a pleural effusion is present as an acoustic medium.

12 104 chapter 5 C D E FIGURE pical views. () pical four-chamber view. rrowhead, apical segment; single arrow, mid-septum; double arrows, lateral wall. () pical five-chamber view. rrowhead, left ventricular outflow tract; double arrows, anterior septum. (C) pical fourchamber view, coronary sinus level. Single arrow, coronary sinus entering the right atrium; double arrow, inferior portion of the septum. (D) pical two-chamber view. *, coronary sinus in short axis; single arrow, anterior wall; double arrows, inferior wall. Line a indicates the orthogonal image plane shown in Figure 5.13 (apical four-chamber view). Line b indicates the orthogonal image plane shown in Figure 5.13 (apical five-chamber view). Line c indicates the orthogonal image plane shown in Figure 5.13C (apical fourchamber, coronary sinus level). (E) pical three-chamber (apical long-axis) view. rrowhead, left ventricular outflow tract; single arrow, anterior septum; double arrows, inferolateral wall. RVOT, right ventricular outflow tract.

13 introduction to echocardiography 105 C FIGURE Mitral valve Doppler interrogation, apical fourchamber view. () Mid-diastole. Small double lines at the open mitral-leaflet tips indicate the proper pulsed Doppler sample-volume position for obtaining mitral E and velocities () and the mitral deceleration time (double-headed arrow, view ). The double-headed arrow () indicates the proper position for measuring the mitral annulus diameter and the appropriate level for pulsed Doppler sample-volume placement when obtaining mitral annulus velocities (C) used for calculating mitral valve forward flow. () Pulsed Doppler image obtained at the mitral valve-leaflet tips. Double-headed arrow, D mitral deceleration time. E, E-wave;, -wave. (C) Pulsed Doppler image, at the mitral annulus level, showing an automated mitral inflow time-velocity integral (TVI = m) used for determining mitral valve flow. lthough the same patient is shown in views and C, the aliased, high-velocity, systolic mitral regurgitation signal (MR, black arrows) appears in view C but not view because the pulsed-doppler sample volume is appropriately placed on the atrial side of the mitral-leaflet closure line in view C. (D) Continuous-wave Doppler examination across the mitral valve detects, in this case, a trivial/mild high-velocity mitral regurgitation lesion (arrow). Standard M-Mode Views M-mode recordings from the parasternal long-axis view (at the aortic valve, mitral valve, and left ventricular levels) and from the short-axis view (at the pulmonary valve level) are a feature of the standard examination (Fig. 5.24). The M-mode display shows data reflected from a single, linear interrogating beam, displayed over time. M mode provides a rapid sample rate [1800 frames per second (fps) versus <100 fps for 2D imaging] and superior axial resolution. This enables detection of small, thin, fast-moving structures (e.g., heart valves, small masses, and endocardial surfaces) and accurate timing of their motion, particularly in the setting of tachycardia. M mode is useful for detecting partial right ventricular free-wall diastolic collapse in pericardial tamponade, as well as ventricular contractile dyssynchrony, 148 paradoxical septal motion, and the independent motion of tiny vegetations. If M mode is to be used for parasternal measurements, the operator and interpreter must ensure that the M-mode beam is exactly tangential to the long axis of the measured structure. ecause this goal is not always technically possible, assessment of ventricular and aortic dimensions frequently relies on the 2D image (Fig. 5.7). Classic M-mode patterns can indicate obstructive lesions of the left ventricular outflow tract and a variety of pathologic valve conditions (see Chapter 21). The mitral anterior leaflet s E-point septal separation distance (Fig. 5.24) can be an important clue to left ventricular dilatation and systolic dysfunction. ecause of its superior sample rate, M mode, combined with color Doppler (color M mode), can assist in the timing of color-flow Doppler phenomena, especially during tachycardia (see Chapter 21).

14 106 chapter 5 FIGURE Color Doppler () and pulsed Doppler () examination of the right superior pulmonary vein from the apical window. The pulsed sample volume is placed approximately 1 cm into the pulmonary vein (arrow, image ). () Normal systolic (S) and dia- stolic (D) pulmonary vein forward flow and late diastolic reverse flow during atrial contraction (). The orange area indicates flow toward the transducer. LV, left ventricle; R, right atrium; RV, right ventricle. Transesophageal Echocardiography Technical spects In size and design, the semiflexible TEE probe is similar to a gastroscope. ecause the TEE probe does not incorporate a fiberoptic visualization system, however, it must be blindly passed into the esophagus. n uncommon but potentially life-threatening complication is esophageal perforation. FIGURE pical four-chamber myocardial tissue Doppler image, with the sample volume placed in the basal lateral wall near the mitral valve annulus. The myocardial velocity is normal, going toward the transducer during systole (S) and away from the transducer in early (E ) and late ( ) diastole. Training and experience with safe probe passage and with conscious sedation are important elements of the examination. ecause imaging windows are available only from the esophagus or stomach, TEE offers less freedom to obtain coaxial Doppler flow signals than does TTE, potentially limiting the amount of hemodynamic data available in certain cases. The desired TEE views are produced by combinations of the following maneuvers: (1) probe-tip deflection in the medial, lateral, antegrade, and retrograde directions by means of hand-operated controls; (2) electronic rotation of the imaging crystal (which is stationary within the probe tip) throughout 180 degrees; (3) advancement and withdrawal of the probe within the esophagus; and (4) clockwise and counterclockwise rotation of the probe within the esophagus (Fig. 5.25). In different patients, available TEE images may vary considerably, depending on the orientation of the heart within the chest and the heart s relationship to the esophagus. Usually, the left atrium lies directly anterior to the esophagus, and that structure s blood pool provides an extremely good acoustic window on the posterior cardiac structures. The left atrium and the mitral valve are generally seen with exceptional resolution, as are the pulmonary veins, interatrial septum, descending thoracic aorta, proximal superior vena cava, and proximal pulmonary veins. Structures positioned more anteriorly (the tricuspid or pulmonary valve) or apically (the left ventricular apex) in the far field may variably suffer from image attenuation or shadowing related to calcifications or prosthetic valves. Image Display The TEE image display can differ from one laboratory to another. Most operators display the small soundemanating portion of the TEE image sector at the top of the screen (Fig. 5.26). ecause the transducer is positioned within a posterior structure (the esophagus), this situation creates a unique display in which the posterior anatomy appears at the top of the screen with the anterior structures toward the

15 introduction to echocardiography 107 FIGURE Tricuspid valve interrogation by continuous-wave Doppler in the four-chamber view, using a combined imaging and Doppler transducer for color Doppler guidance () and a dedicated nonimaging transducer () in the same patient. Note the improved clarity of the spectral Doppler envelope in image. The automated tricuspid-valve regurgitation velocity (VEL) and derived peaksystolic right ventricular pressure gradient (PG) were obtained by placing an electronic caliper on the spectral Doppler peak-velocity position (+). C FIGURE Selected left ventricular outflow-tract Doppler interrogations from the apical window. () Color-flow Doppler image, apical five-chamber view. Note that the color in the left ventricular outflow tract changes from blue to orange (arrow) when the velocity exceeds the Nyquist limit of 53 cm/s, as indicated on the color scale (arrowhead). () Color-flow Doppler image of the left ventricular outflow tract (LVOT) (arrow) in the apical three-chamber view. (C) Pulsed Doppler image of the LVOT, obtained with the sample volume immediately proximal to the aortic annulus. The aortic- D leaflet closure artifact (arrow) and the lack of an opening artifact indicate a good sample-volume position. Note the automated timevelocity integral measurement (TVI, arrowhead) from outlining of the spectral Doppler envelope (dotted curve). (D) Continuous-wave Doppler image across the LVOT and aortic valve. Note the normal, automatically derived low peak-flow velocity (V max ), peak gradient (Pk Grad), and mean gradient (Mn Grad), as well as the aortic valve (ov) TVI obtained by outlining the continuous-wave spectral Doppler envelope (dotted curve).

16 108 chapter 5 C FIGURE pical four-chamber view in fundamental frequency (), tissue harmonic (), and contrast harmonic (C) imaging modes, in the same technically difficult case, with increasingly apparent left ventricular endocardial border delineation. LV, left ventricle. FIGURE Subcostal four-chamber view () and subcostal left ventricular short-axis view (). *, liver; double arrows, inferior wall or diaphragmatic wall; single arrow, anterior wall; L, left atrium; LV, left ventricle; R, right atrium; RV, right ventricle.

17 introduction to echocardiography 109 FIGURE Subcostal view of the inferior vena cava (arrow) entering the right atrium during normal respiration () and with normal collapse during an inspiratory sniff () indicating normal (low) right atrial pressure. (C) Normal pulsed Doppler image of the hepatic vein, via the subcostal window, with predominant antegrade inflow (below baseline) during systole (S) and diastole (D). normal small flow reversal occurs after atrial contraction (). rrowhead, normal augmentation of antegrade inflow velocities during inspiration. x = x-descent; y = y-descent. V, systolic V wave; *, liver. C bottom of the screen [see Fig (TTE) vs (TEE) and Fig (TTE) vs (TEE)]. The caudal anatomy remains displayed on the left and cephalad structures on the right. ccordingly, by convention, there is a potentially confusing up-down inversion of the anatomy in the TEE image relative to the surface image. ll commercial echocardiography machines have an up-down image-inversion mode. Some practitioners intentionally invert the TEE image in up-down fashion (placing the small part of the sector at the bottom) to make the anterior-posterior image display consistent on both surface and TEE images. This inversion is not incorrect, and the choice of TEE display is up to the individual laboratory TLE 5.3. Estimated right atrial pressure IVC, response to Estimated RP IVC, baseline inspiration (mm Hg) Small or slit-like Complete collapse 0 4 Normal ( cm) 50% decrease 5 10 Normal <50% decrease Dilated <50% Dilated No change >20 IVC, inferior vena cava; RP, right atrial pressure. Inferior vena cava observed in the subcostal view during normal respiration or while the patient sniffs gently to decrease intrathoracic pressure. FIGURE Color-flow Doppler image of the suprarenal abdominal aorta in the long-axis view, from the subcostal window, in an imaging plane adjacent to that seen in Figure 5.21.

18 110 chapter 5 C FIGURE The aortic arch in a long-axis, small suprasternalnotch view ()., right pulmonary artery, short axis; arrowhead, left brachiocephalic (innominate) vein; single arrow, left common carotid artery; double arrow, left subclavian artery; ao, ascending aorta; do, descending aorta. () Color-flow Doppler image showing an aliasing phenomenon (aliasing velocity >81 cm/s, white arrows) in the ascending (left black arrow) and descending (right black arrow) thoracic aorta, with complete absence of a color signal when the blood-flow vector is tangential to the interrogating ultrasound vector (black stripe, arrowhead). Solid orange indicates laminar flow toward the transducer; solid blue indicates laminar flow away from the transducer. (C) Pulsed Doppler image of the distal aortic arch, showing normal systolic antegrade flow below the baseline (single arrow) and normal lesser retrograde early diastolic flow (above the baseline, double arrows) related to coronary artery and aortic-arch vessel runoff. or clinician. In all cases, the index mark remains to the right of the sector apex (Fig. 5.26), as in TTE. Sequence of Standard Views Laboratory protocols for TTE (surface) examination should establish a consistent sequence of required views. lthough TEE examination protocols should also define all of the required views or images, the order of image acquisition may vary. For instance, TEE examinations may follow a pathology-directed sequence of views designed to answer the clinical question in a timely fashion in case the patient cannot tolerate the probe or becomes hemodynamically unstable before the exam is completed. fter the chief indication for the examination has been addressed, further views are obtained to complete the study. Obtaining a comprehensive/complete TEE exam (in which all views and appropriate Doppler evaluations are present) is particularly important when evaluating diseases that potentially involve multiple cardiac sites (e.g., rheumatic heart disease, endocarditis, an atypical myxoma with multiple foci, and the cardiovascular source of an embolus). In fact, completeness of examination is important whenever possible because of the high likelihood that TEE will detect unexpected findings that could alter patient care. Transesophageal Views PERICRDIUM ND VENTRICLES (Fig. 5.26) The examination should include a sequence of images obtained at an adequate depth to visualize all ventricular epicardial (pericardial) and endocardial segments, including the cardiac apex. Frequently, a stable imaging window can be found (usually on gentle probe-tip retroflection followed by slight probe withdrawal and rotation) so that the left ventricle s major axis lies in the center of the imaging sector in all of the orthogonal planes. In this case, the transesophageal four-chamber view (near 0 to 30 degrees of transducer rotation), bicommissural view (near 60 degrees), two-chamber view (near 90 degrees), and apical three-chamber view (longaxis view, usually near 120 degrees but up to 160 degrees in older patients) (Fig. 5.26) can all be obtained by electronically adjusting the imaging angle of the transducer. In some patients with relatively vertical hearts (in which the ventricular long axis is relatively parallel to the esophagus), views of the cardiac apex can be difficult or impossible to achieve.

19 introduction to echocardiography 111 C FIGURE () ortic valve M-mode tracing with normal, wide systolic cusp separation (double arrows) and a central diastolic closure line (single arrow). L, left atrium; RVOT, right ventricular outflow tract. () Mitral valve, M mode. Single arrow, posterior mitral leaflet; double arrows, anterior mitral leaflet. E, mitral leaflet early diastolic position;, mitral -wave position; C, mitral closure line; EPSS, E-point septal separation; LV, left ventricle; RV, right ventricle. (C) M-mode tracing of the left ventricle at the papillary muscle level. EDD, left ventricular end-diastolic dimension; ESD, left ventricular end-systolic dimension; LV, left ventricle; RV, right ventricle. TRNSESOPHGEL VIEWS T DECRESED OPTIMIZED DEPTH (Figs to 5.33) fter viewing the big picture, as described above, the examiner may decrease or optimize the depth to view near-field structures in greater detail and at improved (increased) frame rates. The cardiac structures should be viewed in the long-axis, short-axis, and (in many cases) intermediate, oblique imaging planes. ecause of patient variation, standard anatomic views do not always occur at specific transducer angles. Figures 5.26 through 5.33 show the basic TEE views. dditional or modified views may be obtained as appropriate. Doppler interrogations should mirror those performed during TTE examinations. Transverse or horizontal views lie close to a transducer angle of 0 to 30 degrees. Intermediate views (30 to 60 degrees) allow assessment of the aortic valve along its short axis (Fig. 5.28), the left atrial appendage [which is imaged in multiple views (Figs and 5.33)], the mitral bicommissural region (Fig. 5.27), and proper alignment of the pulmonary veins (Fig. 5.32) and pulmonary valve. Vertical or long-axis views of the left ventricle, aortic root, mitral valve, superior vena cava (bicaval view, Fig. 5.31), and descending thoracic aorta are generally obtained from 90- to 120-degree angles. patent foramen ovale may be documented in the TEE bicaval view by using intravenous agitated normal saline (Fig. 5.31). Various strategies may be needed to systematically obtain all the FIGURE Schematic diagram of a transesophageal probe, showing left and right lateral flexion, anteflexion, retroflexion, and rotation of the imaging plane through 180 degrees.

20 112 chapter 5 C D E

21 introduction to echocardiography 113 FIGURE Transesophageal views of the left ventricle (at the mid-esophagus level) showing the entire ventricular myocardium and pericardium (at increased depth). Note: The indicated transducer angles may vary considerably among patients. () Fivechamber view (transducer angle approximately 0 degrees in the horizontal plane). Compare with transthoracic echocardiography (TTE) image, Figure rrowhead, left ventricular outflow tract; L, left atrium; LV, left ventricle; R, right atrium; RV, left ventricle. () Four-chamber view (transducer angle approximately 30 degrees). Compare with TTE image, Figure rrow, index mark; arrowhead, left ventricular apex. (C) icommissural view (transducer angle approximately 60 degrees) showing the three pos- terior leaflet scallops of the mitral valve the anterior (P1), middle (P2), and posterior (P3) scallops in the systolic (closed) position. This view is important for localizing posterior-leaflet prolapse or chordal-rupture lesions. Left arrowhead, posteromedial papillary muscle tip; right arrowhead, anteromedial papillary muscle tip. (D) Two-chamber view (transducer angle approximately 90 degrees in the vertical plane). Compare with TTE image, Figure 5.13D. rrowhead, apex; single arrow, anterior wall; double arrows, inferior wall. (E) Three-chamber view (transducer angle approximately 120 to 160 degrees). Compare with TTE image, Figure 5.13E. Single arrow, anterior septum; double arrows, inferolateral wall; o, aortic root; L, left atrium; RVOT, right ventricular outflow tract. necessary views. It is important to maintain both a stationary probe and a stationary transducer angle position while recording complete individual cardiac cycles, so that the same anatomic features can be visualized throughout systole and diastole. The probe can then be manipulated systematically in a logical, incremental fashion to acquire subsequent images according to the examination protocol or in a pathology-directed sequence that reflects the indication for the exam. Transgastric Views This additional imaging window is obtained by advancing the TEE probe into the stomach. During this advancement, one can usually obtain a low transesophageal (gastroesophageal-junction) view (Fig. 5.34), which shows the posteriorly located coronary sinus along its long axis and the lower portion of the tricuspid valve. Though sometimes ignored, this view can be important for detailed tricuspid valve assessment, for guiding coronary sinus catheter placement in the operating room, or for visualizing other pathologic conditions of the coronary sinus. Further probe advancement into the stomach yields a short-axis view of the left ventricle, at the papillary muscle level (Figs and 5.36), which appears inverted relative to the analogous TTE view (Fig. 5.10). Ninety-degree transducer advancement from the left ventricular short-axis position will produce the gastric left ventricular long-axis view (Fig. 5.37). Clockwise probe rotation from the left ventricular long-axis view will produce the right ventricular and tricuspid valve long-axis view (Fig. 5.37). Even if the tricuspid valve was obscured in transesophageal windows, it can often be seen clearly in this view. In most but not all cases, the left ventricular outflow tract can be visualized and evaluated for obstruction or insufficiency with Doppler methods from a horizontal-plane, deepgastric view, obtained by further advancing the probe to the cardiac apex (Fig. 5.38,), or from a more proximal modified left ventricular long-axis view (Fig. 5.38C). Gradual probe withdrawal from the gastric LV short axis view produces the mitral valve short-axis view (Fig. 5.39) just below the gastroesophageal junction. s in surface imaging (compare with Fig. 5.10), this view can be important for determining individual scallop involvement in mitral valve dysfunction. Transesophageal Views: Descending Thoracic orta (Fig. 5.40) ecause of its generally excellent imaging windows, TEE is an important modality for detecting pathologic conditions of FIGURE Transesophageal bicommissural view at decreased depth during systole () and diastole (), showing the mitral valve s posteromedial commissure (left arrowhead) and anterolateral com- missure (right arrowhead). Three posterior mitral valve scallop regions (P 1 to P 3 ) are present.

22 114 chapter 5 FIGURE Transesophageal short-axis view of the aortic valve in diastole () and systole (). *, left atrial appendage; arrowhead, interatrial septum; single arrow, pulmonary valve; double arrows, tricuspid valve; L, left coronary cusp; L, left atrium; N, noncoronary cusp; P, pulmonary artery; R, right coronary cusp; R, right atrium; RVOT, right ventricular outflow tract. For analogous transthoracic echocardiography view (inverted), see Figure Note: The appropriate transducer angle varies from 30 to 90 degrees depending on the patient s age and the left ventricle-aortic root angle. the aorta, for example, dissection (Fig. 5.30), atheroma (Fig. 40,D), and intramural hematoma. The aortic root and ascending aorta should be visualized in the other transesophageal views noted above (Figs. 5.26,E and 5.28 to 5.30). The rest of the thoracic aorta, from the midtransverse arch to the level of the diaphragm, is visualized by rotating the probe leftward, away from the heart, toward the left paravertebral region (transducer position = 0 degrees). The aorta should be centered within the imaging sector. Representative short- and long-axis aortic views are sequentially acquired at 5-cm intervals or whenever important pathology is encountered. The descending thoracic aorta (diaphragm level) is usually seen in the short-axis view when the teeth (incisors) are even with the probe s 35- to 40-cm depth mark, depending on patient size. The curvilinear distal arch is visualized in the short-axis view by using intermediate (30 to 60 degrees) transducer angles as the probe is gradually withdrawn so that the incisors are at approximately the probe s 25-cm depth mark (Fig. 5.40C). The mid-arch is visualized in the short-axis view at a transducer angle of approximately 90 degrees. The distal ascending aorta and proximal aortic arch frequently lie in a TEE blind spot because of interposed airways. Doppler Examination and Hemodynamics When sound is reflected from a stationary target, the returning reflected frequency is the same as the original transmitted frequency. When sound returns from a moving target, however, the reflected frequency is higher than the transmitted frequency if the target is moving toward the receiver. In medical ultrasound, the transducer is both the sound emitter and sound receiver. The reflected sound has a lower frequency if the target is moving away from the receiver. Known as the Doppler shift, FIGURE Transesophageal echocardiogram of the great vessels, in the short-axis view (horizontal plane), at the level of the ascending aorta and right pulmonary artery (RP), showing typical sideby-side short-axis circles of the ascending aorta (ao), superior vena cava (SVC), and right superior pulmonary vein (arrowhead). This view is important for excluding anomalous right superior pulmonary venous drainage into the superior vena cava and for viewing the proximal great vessels. Line a indicates the orthogonal image planes shown in Figures 5.26E and Line b indicates the orthogonal image plane shown in Figure Line c indicates the orthogonal image plane shown in Figure P, pulmonary artery.

23 introduction to echocardiography 115 FIGURE () Long-axis view of the aortic root and ascending aorta in a patient with Type aortic dissection (arrow). The intimal flap extends proximally to the right coronary artery ostium (black arrowhead). Double arrows, pericardial effusion; L, left atrium; R, right atrium. () Short-axis view of the aortic root. *, partial right ventricular outflow-tract collapse indicating associated pericardial tamponade; black arrowhead, left coronary artery ostium; single arrow, dissection flap within the right coronary sinus of Valsalva; double arrows, right atrial compression; FL, false lumen; L, left atrium; TL, true lumen. FIGURE Transesophageal bicaval views. (,) Similar anatomy, but view optimizes tricuspid-valve visualization (downward arrowhead) and is useful for Doppler interrogation. IVC, inferior vena cava; L, left atrium; R, broad-based right atrial appendage; SVC, superior vena cava. View shows the thin fossa ovalis (single arrow) which, in this case, is patent. rrowhead, eustachian valve of the IVC; bracket, patent fossa ovalis (PFO) tunnel. (C) Intravenous agitated saline contrast bubbles transit from the right atrium (R) to the left atrium (double arrows) via the PFO on relaxation of a Valsalva maneuver. The R and superior vena cava (SVC) are completely opacified by intravenous injection of saline contrast. C

24 116 chapter 5 FIGURE Transesophageal view of the superior pulmonary veins. () The right superior pulmonary vein (arrow) with the pulsed Doppler sample volume approximately 1 cm inside the os; adjacent is the right-sided superior vena cava (SVC). L, left atrium; R, right atrium. () The left superior pulmonary vein (arrow) lies immediately posterior to the left atrial appendage (L). L, left atrium; LV, left ventricle. Doppler shift (Hz) = Reflected frequency Transmitted frequency, this physical principle explains why a stationary listener notices an abrupt fall in the pitch of an approaching train s whistle just after the train passes and begins to move away. The velocity of a moving insonated target (e.g., blood cells or the myocardium in motion) can be calculated by using the Doppler equation to analyze the returning sound frequency initially emitted from the transducer: Sound propagation speed Doppler shift Velocity = 2 Transmitted frequency cos If blood is moving parallel (coaxial) to the interrogating sound beam, the complete Doppler shift is measured and an accurate velocity reported (since cos 0 degrees = 1). When the path of a moving insonated target is not parallel to the interrogating sound beam, the reported velocity will be lower than the true velocity, proportional to cos of the intercept angle between the ultrasound beam and the true direction of blood movement: Measured velocity = True velocity cos ecause cos 20 degrees = 0.94, Doppler alignment errors of <20 degrees will result in a velocity measurement error of <6%, which is acceptable without correction in most clinical situations. Note that because cos 60 degrees = 0.5, an intercept angle of 60 degrees will yield only half of the true velocity, and an intercept angle of 90 degrees (cos 90 degrees = 0) will produce no measurable blood-flow velocity (Fig. 5.23). FIGURE Transesophageal view of the left atrial appendage (L). The narrow-based L is imaged in both the horizontal () and the vertical () plane. normal prominent reflection of left atrial tissue (*) is seen between the L and the left upper pulmonary vein (LUPV). o, aortic root; L, left atrium; LV, left ventricle.

25 introduction to echocardiography 117 FIGURE Transesophageal view at the gastroesophageal junction. rrowhead, coronary sinus in long axis, showing entry into the right atrium (R). Compare with TTE image, Figure 5.13C. LV, left ventricle; RV, right ventricle. FIGURE Transgastric image of the left ventricle in the shortaxis view at the papillary muscle level. L, anterolateral papillary muscle; LV, left ventricle; PM, posteromedial papillary muscle; RV, right ventricle. FIGURE Transgastric image of the left ventricle in the shortaxis view at the papillary muscle level. () Fundamental frequency imaging mode: the result is technically poor, with an attenuated image and a low signal-to-noise ratio. () Tissue harmonic imaging mode in the same patient. Intracavitary noise is decreased and endocardial definition improved. Upper arrowhead, inferior wall; lower arrowhead, anterior wall. Line a indicates the orthogonal image plane shown in Figure Line b indicates the orthogonal image plane shown in Figure LV, left ventricle; RV, right ventricle. FIGURE Transgastric long-axis views of the left and right ventricles. () Left ventricle (LV): normal mitral valve chordae tendineae arise from the posteromedial (*) and anterolateral (arrow) papillary muscles. L, left atrium; L, left atrial appendage. () Right ventricle: normal tricuspid valve chordae tendineae arise from the right ventricle (RV) anterior papillary muscle (*). R, right atrium.

26 118 chapter 5 C FIGURE () Deep gastric view of the left ventricle (transducer angle approximately 0 degrees). This view enables coaxial Doppler evaluation of the left ventricular outflow tract by means of transesophageal echocardiography. See Figure 5.13 for the analogous surface echocardiography view. o, aorta; LV, left ventricle; RVOT, right ventricular outflow tract. () Color Doppler image of the left ventricular outflow tract with an appropriately placed pulsed-doppler sample volume (arrow). (C) modified transgastric long-axis view of the left ventricle (LV), often at a transducer angle of >90 degrees, frequently enables Doppler evaluation of the left ventricular outflow tract (arrow) when the deep gastric view is not possible. o, aortic root; LV, left ventricle. FIGURE Transgastric image of the left ventricle, in the shortaxis view, at the mitral valve level. () Mitral valve posterior leaflet: anterior (P 1 ), middle (P 2 ), and posterior (P 3 ) scallops; mitral valve anterior leaflet: anterior ( 1 ), middle ( 2 ), and posterior ( 3 ) segments. This view is important for localizing mitral regurgitation lesions. Compare with TTE image, Figure Line a indicates the orthogonal TEE imaging plane shown in Figures 5.26C and 5.27 (bicommissural view). L, anterolateral commissure; PM, posteromedial commissure; RV, right ventricle. () Obtaining a color-doppler image at this level is important. In this same patient, it shows significant functional regurgitation along the entire zone of mitral leaflet coaptation.

27 introduction to echocardiography 119 C FIGURE Transesophageal views of the descending thoracic aorta. () Normal aorta. () Grade II calcified atheroma (arrowhead) in the mid-descending thoracic aorta. *, atelectatic lung; **, large left D pleural effusion. (C) Normal left subclavian artery (arrow) at the level of the aortic isthmus. (D) Descending thoracic aorta in long axis, with complex atheroma and mobile atherosclerotic debris (arrow). ecause the exact path of the blood flow cannot be precisely determined, even with anatomic guidance, velocity measurements are determined from several different imaging locations so that the highest values can be used. Spectral Doppler Spectral Doppler imaging comprises two modalities: continuous wave (CW) and pulsed wave (PW). On the spectral Doppler display, Doppler shift derived velocities moving toward the transducer appear as positive deflections above the baseline (see Fig. 5.14). Flow velocities moving away from the transducer are displayed below the baseline (see Fig. 5.18C). Continuous-Wave Doppler asic Concepts. Continuous-wave Doppler uses a dedicated crystal to continuously transmit signals while an adjacent crystal continuously receives the reflected signals. This modality has the advantage of being able to measure the high-frequency shifts and corresponding high-velocities (>7 m/s) created by obstructive or regurgitant orifices. Continuous-wave Doppler examination has the disadvantage of range ambiguity, because velocities anywhere along the interrogating beam are displayed. Range ambiguity can be problematic when serial obstructive lesions occur along the line of interrogation [e.g., in combined dynamic left ventricular outflow-tract (LVOT) obstruction and aortic valve stenosis]. arring the presence of serial stenoses, the highest recorded velocities may be assumed to arise from the obstructive orifice in question. The CW Doppler modality is integrated along with pulsed-wave Doppler in an imaging transducer. This may be useful for positioning the interrogating beam with anatomic and color Doppler guidance. However, the true direction of a jet lesion within the anatomic orifice may be difficult to judge with either anatomic or color Doppler guidance. Superior CW spectral Doppler envelopes are recorded with a dedicated nonimaging transducer (Fig. 5.4), which has a smaller footprint that is more easily brought into coaxial alignment with jet lesions, using a variety of surface windows.

28 120 chapter 5 Continuous-Wave Doppler and the Pressure- Velocity Relationship. When blood crosses a small, restricted orifice (e.g., stenotic valve, incompetent valve, or ventricular septal defect), its velocity increases relative to the pressure difference between the two chambers. The peak instantaneous pressure drop across a narrow orifice is calculated with the simplified ernoulli equation: ΔP = 4V 2 where the peak velocity (V) is derived from the CW spectral Doppler display (Fig. 5.17). Mean pressure gradients are determined by calculating the instantaneous pressure gradient (4V 2 ) at multiple time intervals during the flow period and by averaging the results. Echocardiography machines and off-line analysis programs automatically calculate peak instantaneous and mean pressure gradients in millimeters of mercury (mm Hg) when the CW Doppler spectral envelope is manually outlined with a tracker ball (Fig. 5.18D). With CW Doppler, the spectral display has a characteristically filled-in appearance because of turbulent blood flow; a large number of velocities occur at all points below the peak instantaneous velocities represented by the envelope s outer edge (Figs. 5.12D and 5.18D). Table 5.4 lists the sites routinely used for CW Doppler interrogation. The CW Doppler pressure-velocity relationship is used to measure pressure gradients across obstructed valve orifices, ventricular septal defects, and dynamic left and right ventricular outflow obstructive lesions, as well as to identify and qualitatively assess severity of valve regurgitation lesions. Pulmonary rtery Pressure Calculation. The peak right ventricular systolic pressure (RVSP) is routinely calculated with the simplified ernoulli equation, as this approach yields highly useful information, and up to 80% of individuals have at least trivial tricuspid regurgitation (TR), the velocity of which (V TR ) may be measured by CW Doppler. In the absence of right ventricular outflow obstruction, the peak systolic pulmonary artery pressure (SPP) is the sum of the RVSP and the estimated right atrial pressure (RP) 149 : RVSP = 4V TR 2 SPP = 4V TR 2 + RP The RP can be determined by measuring the degree of inferior vena cava (IVC) collapse approximately 2 cm from the IVC right atrium (R) junction (subcostal view) during normal inspiration or a sniff (Fig. 5.21; Table 5.3). 150 During positive-pressure mechanical ventilation, a small, collapsing IVC indicates a low RP, although an enlarged and noncollapsing IVC does not necessarily indicate an elevated RP under this circumstance. 151 When the TR velocity is faint, its spectral Doppler envelope can be enhanced by intravenous injection of agitated saline solution during interrogation. 152 The peak CW Doppler-derived gradient of the pulmonary valve insufficiency (PI) jet (4V PI 2 ), also measurable in most patients, has been shown to approximate the mean pulmonary artery pressure 153 : Mean PP = 4(V PI ) 2 TLE 5.4. Routine sites for continuous-wave Doppler examination Parasternal long axis, RV inflow tract TV Parasternal short axis (at ov and RVOT TV, PV level) pical four-chamber TV, MV pical five-chamber LVOT pical three-chamber LVOT, MV Subcostal* ov (if S*) Sternal notch Descending orta, ov* (if S) Right parasternal* ov* (if S) Modified apical* Pulsed Doppler TV if difficult TR velocity* * dd if a pathologic condition is detected. It is desirable to repeat the evaluation with a nonimaging probe for accurate V TR and for left-sided valve obstructive lesions (i.e. S, MS). ov, aortic valve; S, aortic stenosis; LVOT, left ventricular outflow tract; MV, mitral valve; PV, pulmonary valve; RV, right ventricular; RVOT, right ventricular outflow tract; TR, tricuspid regurgitation; TV, tricuspid valve. asic Concepts. In pulsed Doppler mode, the piezoelectric crystal alternates between sending and receiving at a defined pulse repetition frequency. fter sending out an ultrasonic pulse, the machine knows when to listen for the returning signal by calculating the send and receive time of flight to the desired depth at which the Doppler frequency shift is to be measured. The sonographer chooses the Doppler depth by placing a sample volume in a desired location, using the image sector for anatomic guidance (Figs. 5.12C, 5.14,C, 5.15,,C, and 5.18). Range discrimination is an inherent property of pulsed Doppler mode because the blood velocity is measured at a known distance from the transducer. The maximum blood speed that can be measured with pulsed Doppler at a given depth is called the Nyquist limit, which is half the pulse repetition frequency. When blood velocities exceed the Nyquist limit, the spectral Doppler display erroneously indicates that blood is moving in the wrong direction. This phenomenon is called aliasing (see Fig. 5.14C for pulsed Doppler aliasing and Figs and 5.18, for color Doppler aliasing). For practical purposes, pulsed Doppler mode can unambiguously measure blood flow velocities of up to about 2 m/s at normal imaging depths. With normal laminar flow, the typical pulsed Doppler spectral envelope has bright edges and a dark center (Fig. 5.18C). This is because all the blood cells within the sample volume are moving in the same direction and at roughly the same velocity, as represented by bright spectral envelope edges. The principal applications for pulsed Doppler mode are assessing cardiac output, regurgitant volumes, shunts, and diastolic function. Table 5.5 indicates standard sites for pulsed Doppler evaluation. Stroke Volume and Cardiac Output. Where laminar flow is present, the instantaneous flow rate is the product of the cross-sectional area (CS) and the instantaneous flow velocity (cm/s) at the same site. Integrating the area under a pulsed Doppler flow-velocity curve yields the time-velocity integral (TVI) distance, reported in centimeters. The TVI

29 introduction to echocardiography 121 TLE 5.5. Routine sites for pulsed Doppler examination Parasternal short axis, RVOT RVOT/PV annulus level pical four-chamber MV leaflet tips and MV annulus, right superior pulmonary vein pical five-chamber LVOT pical three-chamber LVOT Subcostal Hepatic vein, aorta* (if I) Sternal notch Descending aorta at isthmus * dd if a pathologic condition is detected. I, aortic insufficiency; LVOT, left ventricular outflow tract; MV, mitral valve; PV, pulmonary valve; RVOT, right ventricular outflow tract. indicates the distance a volume of blood would travel during the flow period within a conduit that has a certain CS. The flow during a cardiac cycle (stroke volume) can be calculated by multiplying the CS of a conduit by the integrated flowvelocity curve (TVI) distance. Left Ventricular Outflow Tract. Integrating the area under the LVOT pulsed-doppler velocity curve yields the LVOT TVI in centimeters (Fig. 5.18C). It is valid to assume that the normal LVOT is circular (CS = π r 2 = D 2 π/4 = D ) (r = radius). The LVOT diameter (D) is measured in the parasternal long-axis view (Fig. 5.7). The LVOT area, stroke volume (SV), and cardiac output (CO) can be calculated as follows: CS = D SV (cm 3 ) = CS (cm 2 ) TVI (cm) CO = SV HR Right Ventricular Outflow Tract. The right ventricular outflow tract (RVOT) stroke volume and cardiac output are obtained in analogous fashion, using the equations shown above (see Fig for the RVOT diameter and Fig. 5.12C for the RVOT TVI). The RVOT diameter measurement, obtained in the parasternal short-axis view (Fig. 5.11) may be less reliable than the LVOT diameter measurement because of a somewhat retrosternal RVOT location that can cause lateral RVOT image dropout from sternal or rib shadowing. Mitral nnulus. The mitral annulus stroke volume and cardiac output are obtained in analogous fashion (see Fig for mitral annulus diameter and Fig. 5.14C for mitral annulus TVI). The mitral annulus diameter (Fig. 5.14) may be difficult to measure if annular calcification or some other leaflet deformity impairs leaflet motion. lthough the mitral annulus is elliptical and not circular, the four-chamber view places the annulus dimension between the major and minor mitral axes of the valve s ellipse. This may explain why assuming a circular mitral annulus has proved valid when using the four-chamber annulus diameter. Note that pulsed Doppler readings obtained at the mitral leaflet tips cannot be used for calculating mitral valve flow because the leaflettip orifice area (which is smaller than the annular orifice area) cannot be reliably measured. Technical Notes. In sinus rhythm, stroke volumes are ideally calculated from 3 to 5 averaged TVIs. In irregular rhythms (atrial fibrillation), stroke-volume calculations should be derived from 5 to 10 averaged TVI measurements. Premature ventricular contraction (PVC) and post-pvc cycles should be excluded. Precise diameter measurements are essential because this linear variable is squared during flow calculations, so any error is compounded. Ideally, three diameter values are obtained from different cycles to ensure reproducibility. With satisfactory data, comparison of the LVOT and RVOT stroke volumes can be used to calculate right-to-left shunts (QP = pulmonary flow, QS = systemic flow). The CO can be measured at rest or during exercise or pharmacologic interventions. The outflow tract CS and TVI measurements are essential components of valve-area calculations using the continuity equation. In addition, the LVOT or RVOT stroke volume (in the absence of reference valve-insufficiency lesions) may be subtracted from the mitral annular stroke volume to calculate the mitral regurgitant volume. n aortic valve regurgitation volume may be calculated in analogous fashion using the RVOT or mitral annulus forward stroke volume as a reference value (in the absence of significant reference-valve regurgitation). Color-Flow Doppler Color-flow Doppler is a multigated pulsed Doppler technique that is valuable for visualizing overall flow patterns within the heart and great vessels. Instead of measuring the direction and velocity of flow at a specific location (as with spectral Doppler), this method assigns colors to the pixels throughout an anatomic region of interest, depending on the measured flow direction and velocity. Color-flow information is superimposed on the anatomic gray-scale image so that flow patterns can be correlated with the anatomy. Calculating the velocity shift at numerous sites in real time requires considerable computing speed. With older machines, the color-flow sample rate can be unacceptably slow (i.e., <12 fps) when color sectors are too large. With parallel processing, newer machines largely eliminate this concern. color map (Figs and 5.23, upper right of images) is shown alongside the anatomic image, indicating the direction of flow. Typically, blue (at the bottom of the map) indicates flow away from the transducer, and orange/red (at the top of the map) indicates flow toward the transducer ( RT = blue away, red toward). The number at either end of the color map indicates the color-doppler Nyquist limit, which is typically below 1 m/s and generally set in the range of 50 to 60 cm/s for detecting and analyzing regurgitant lesions. Color-Doppler aliasing is extremely common, because normal intracardiac blood velocities often exceed 60 cm/s. When this happens, the color abruptly changes to the hue assigned to flow moving in the opposite direction. This color wraparound effect clearly delineates flow-velocity boundaries, thereby identifying zones of mild acceleration (e.g., at a valve annulus) (Figs and 5.18,) and proximal flowconvergence zones associated with regurgitant lesions (see Chapter 21). When blood flow is exactly tangential to the direction of the interrogating beam, no color (black) is displayed (Fig. 5.23). Color-Doppler mode is highly sensitive in detecting (if not quantitating) regurgitant jet lesions, because

30 122 chapter 5 turbulent high-velocity flow is labeled with an easily recognizable speckled or mosaic color pattern (Fig. 5.39). Color- Doppler gain and Nyquist-limit settings are easily adjustable; they can markedly affect color-doppler results and their interpretation. Color-Doppler mode is beset by numerous potential artifacts, which cannot be reviewed here. dditionally, its appearance varies, depending on the equipment manufacturer. Tissue Doppler Tissue-Doppler is analogous to pulsed Doppler assessment of blood flow velocity. Instead of being placed in the blood pool, however, the tissue Doppler sample volume is placed in a myocardial segment (Figs and 5.41C). ppropriate filters are applied so that only the high-amplitude but relatively low velocities inherent in myocardial motion are included. Tissue-Doppler studies are usually performed in the apical views because longitudinal myocardial motion is coaxial to the interrogating beam in this situation. Longitudinal descent of the cardiac base is an important indicator of systolic function. growing body of literature has shown that even localized myocardial tissue Doppler can provide important information about diastolic function. Moreover, this information is less affected by loading conditions than are blood flow pulsed Doppler filling patterns. Tissue Doppler can be used to assess left ventricular filling pressures, to detect overt and subclinical cardiomyopathy, and to distinguish constrictive from restrictive cardiomyopathy. 39,45,46,56 Parametric Imaging Tissue Doppler Imaging New ultrasound technology allows extremely high-frequency imaging and measurement of myocardial tissue velocities of >100 fps within the imaging sector. The pixels that represent the anatomic myocardium are color coded to depict the myocardial direction and velocity throughout the cardiac cycle (Figs to 5.44). This type of moving anatomic and functional display (TDI) is a parametric imaging modality. 105 Changing color patterns within the anatomic image can indicate regions of myocardial dysfunction with a sensitivity potentially surpassing that of traditional gray-scale myocardial wall-motion analysis. When one or more sample volumes (Figs and 5.44C) are placed within the myocardium, relatively high-fidelity curvilinear graphs of the average longitudinal myocardial velocity can be generated. Comparison of the time-to-peak longitudinal velocities measured in opposing myocardial segments may be an adequate proxy for identifying dyssynchronous mechanical systole that may be improved by cardiac resynchronization therapy (CRT) in heart failure patients (Fig. 5.44) Curved natomic M-Mode Display Curved anatomic M mode is a newer myocardial Doppler imaging format that can show the timing of myocardial motion (velocity) throughout a selected length of myocardium (Fig. 5.43). Other forms of myocardial physiologic data (e.g., strain, strain rate) can be displayed in anatomic M-mode format so that physiologic conditions within different myocardial segments can be displayed simultaneously (Figs. 5.45, 5.46, and 5.47). Tissue Synchronization Imaging Tissue synchronization imaging (TSI) is a relatively new term for images produced by color coding myocardial pixels with time-to-peak velocity values derived from TDI data. Color values for delayed time-to-peak velocity values are somewhat arbitrarily determined, but this method calls attention to myocardial segments that contract late because of conduction abnormalities or dyssynchrony (Figs. 5.44D and 5.45). Myocardial segments that do not contract or thicken (i.e., scarred or hibernating myocardium) may exhibit considerable translational motion because of tethering by adjacent contracting segments. Thus, one possible pitfall is that TDI will encode tethered nonviable (scarred) segments or noncontracting but viable segments (hibernating myocardium) with velocity information. In this case, TDI erroneous ly gives nonviable segments the appearance of contractility where there is none. nother TDI-based modality that may address this contractility problem is strain-rate imaging. Strain, Strain Rate, and Strain-Rate Imaging Derived from Doppler These additional imaging modes are derived from the myocardial TDI velocity information discussed above. The concepts of strain and strain rate are not new. However, the recent commercial availability of their ultrafast derivation and myocardial parametric display could produce a number of clinically useful applications. Strain is another word for deformation. Strain can be calculated as the change in length (L) between two points within a myocardial segment (L L o ) divided by the original length (L o ). Strain = (L L o )/L o In normal myocardium, L (systolic length) is shorter than the original diastolic length (L o ). Therefore, normal myocardium has negative systolic strain (because of segmental shortening) and positive diastolic strain (because of segmental lengthening) (Fig. 5.46). When regional myocardial deformation does not occur (L = L o ), strain is zero, indicating an absence of contractility regardless of whether the segment is moving through space because of tethering. Strain is expressed as a percentage of L o. The strain rate is the speed at which regional myocardial shortening or lengthening occurs. The strain rate is calculated from the myocardial tissue Doppler velocities (V) obtained from two nearby points (V 1 and V 2 ) separated by a distance L. Strain rate = (V 2 V 1 )/L The strain rate is also called the instantaneous spatial velocity gradient, which is the rate at which two points are approaching each other because of myocardial thickening (during contraction) or moving further apart because of myo-

31 introduction to echocardiography 123 C FIGURE Normal tissue Doppler image in the apical fourchamber view. () Normal, synchronous systolic longitudinal myocardial motion toward the transducer produces a uniform orange-red appearance. Upper right: the upward arrow next to the color scale indicates myocardial motion toward the transducer. Lower left: The upward arrow shows late systolic timing of the acquired image. () Normal, synchronous diastolic longitudinal myocardial motion away from the transducer produces a uniform blue appearance. (Upper right) The downward arrowhead next to the color scale indicates myocardial motion away from the transducer. (Lower left) The downward arrowhead shows early diastolic timing of the acquired image. (C) Tissue Doppler sample volume located in the basal lateral wall (arrowhead), with corresponding tissue spectral Doppler tracing. The arrow and arrowhead depict the direction and timing of the images shown in views and. cardial lengthening. Strain is the time integral of the strain rate (much as TVI is the time-velocity integral of the Doppler flow-velocity curve over time). ecause strain is produced by shortening of the myocardial fibers, strain and strain rate may be better indicators of myocardial contractility than is the tissue-velocity information from which these parameters are derived. One pitfall of Doppler-derived strain measurements of myocardial tissue is that this method can effectively describe only longitudinal strain of the basal and midventricular segments from the apical views. This is because (as explained above) pulsed Doppler imaging is accurate only in a direction coaxial to the interrogating ultrasound signal. Ventricular longitudinal shortening is only one of the three vectors that describe myocardial motion. Inward myocardial motion (radial thickening) and left ventricular torsional motion (circumferential shortening, which is prominent in the apex) may also be described by radial and circumferential strain, respectively, so Doppler-derived longitudinal strain imaging can show only part of the picture. Strain and Strain-Rate Imaging by Means of Speckle Tracking Speckle tracking is a new modality that is still undergoing clinical experimental validation. Discrete, brightly echoic intramyocardial pixels can be recognized by the echocardiography device and tracked during the cardiac cycle. The distance through which nearby speckles approach each other (strain) and the rate at which this is accomplished during the cardiac cycle (strain rate) may be derived from the longitudinal, circumferential (torsional motion), or radial inward motion of myocardial speckles (Fig. 5.48). Though still in the early stages of clinical development, this new modality may become an important tool for evaluating myocardial health.

32 124 chapter 5 FIGURE Tissue Doppler image of opposing segments of the septal wall (yellow circle) and the lateral wall (green circle) in a normal patient. Systolic myocardial motion inward, toward the transducer, appears orange (upward arrow), and diastolic motion outward, away from the transducer, appears blue (downward arrowhead), as in Figure The graph at right indicates the average spectral Doppler velocity pixel intensity displayed over time. Simultaneous display of the septal wall (yellow line) and lateral wall (green line) average velocity curves, which show near-synchronous achievement of peak velocity values (upward arrow) by the opposing segments, as well as a synchronous negative directional peak velocity (downward arrowhead). FIGURE Tissue Doppler image in curved anatomic M-mode format in the same (normal) patient shown in Figures 5.41 and This format shows simultaneous myocardial velocity readings, as defined by the color scale along a defined line of myocardium from the basal to the middle and apical septum. Three cardiac cycles are shown. Uniform timing of the red-to-blue color change from systole (S) to diastole (D) indicates a synchronous myocardial velocity change along the entire septum.

33 introduction to echocardiography 125 C FIGURE Myocardial dyssynchrony, as shown by tissue Doppler imaging (apical four-chamber view) in a patient with left bundle-branch block. () Early systolic septal motion toward the transducer (red), with simultaneous lateral wall motion away from the transducer (blue). () Late systole in the same cardiac cycle, showing septal motion away from the transducer and simultaneous delayed lateral wall motion toward the transducer (red). (C) Simultaneous time plots of the mean tissue velocities within septal (yellow circle) and lateral-wall (green circle) sample volumes confirm an early septal time-to-peak velocity (left arrow, yellow curve) and D a markedly delayed lateral-wall time-to-peak velocity (right arrow, green curve). Ventricular longitudinal motion between the opposing segments is discordant or dyssynchronous. (D) In the same patient, a novel myocardial Doppler imaging format uses an automated time-to-peak delay color scale to effectively show the heterogeneous left ventricular contractile pattern. Segments with delayed time-topeak velocities (>400 ms) are shown in orange (see color scale). utomated time-to-peak velocity calculations of four myocardial segments (+ s) are shown in the table [basal septum (1 S); middle septum (2 MS); midlateral (3 ML); basal lateral (4 L)]. Methods for Improving Two-Dimensional Imaging Tissue Harmonics Fundamental frequency imaging involves creating an image by processing reflections that have the same frequency as the originally transmitted frequency. Until the late 1990s, this modality was the only 2D option that was commercially available. Sound frequencies that are multiples of the fundamental frequency are known as harmonic frequencies. If the fundamental transmitted frequency is 2.5 MHz, the second harmonic frequency is 5 MHz (2 2.5 MHz). ecause soundwaves behave nonlinearly as they pass through tissues, the waves produce harmonic frequencies that, until recently, were not listened for by ultrasound machines. lthough this sound energy is minute, it undergoes less distortion than the fundamental frequencies, so it is used to great effect for distinguishing tissue signals from noise. The tissue-harmonic mode has greatly enhanced endocardial detection and improved both routine and stress echocardiographic surface imaging in patients with previous technically difficult exams (Figs. 5.19, and 5.36,). However, this mode may make valve leaflets and other easily imaged thin structures appear unusually thickened even when they are normal in reality; this illusion is due to the fact that, compared with fundamental frequency imaging, harmonic imaging has an increased pulse length requirement. With experience, echocardiographers have learned to read through this phenomenon and to refrain from calling normal leaflets thickened because of their appearance in this mode. Contrast Echocardiography To clarify the left ventricular endocardial border and improve spectral Doppler signals, the examiner can intravenously administer microbubbles, sometimes called microspheres or

34 126 chapter 5 C FIGURE Three-dimensional tissue Doppler imaging: acquisition of a three-dimensional volumetric data set allows the simultaneous display of apical four-chamber (), two-chamber (), and three-chamber (C) views. In this case, delayed time-to-peak longitudinal velocities are clearly localized to the mid-distal anterior septum and inferior walls (arrows, orange). FIGURE Doppler-derived longitudinal strain rate imaging in the septum (apical four-chamber view) of a healthy 30-year-old man. narrow imaging sector was used to maximize the sample rate (185 fps in this case). () Localized strain-rate analysis within an oval sample volume, middle septum. Negative strain-rate period (myocardial shortening): SR IVCT, strain rate of isovolumic contraction; SRS, systolic strain rate; SR IVRT, strain rate of isovolumic relax- ation. Positive strain rate periods: SRE; early diastolic E strain rate; SR, late diastolic strain rate. () natomic M-mode displays the strain rate throughout the entire septum during a single cardiac cycle. Yellow indicates negative strain (myocardial longitudinal shortening/compression rate), while blue indicates a positive strain rate (myocardial longitudinal lengthening rate).

35 introduction to echocardiography 127 FIGURE Strain rate imaging (SRI) using the speckle tracking method [two-dimensional (2D) strain] in the left ventricular parasternal short-axis view. The circumferential (, arrows), radial (, arrows), and longitudinal (not shown) components of myocardial strain and strain rate can be analyzed with this method. Color-coded dots on the anatomic M-mode display (lower left) correspond to dots placed on discrete myocardial segments of the 2D image (upper left) and the colored lines of the mean strain-rate plot (on right), allowing regional SRI comparison. ultrasound contrast agents as an adjunct to the routine examination. Microspheres (diameter = 2.5 to 4.0 μm) are smaller than red blood cells (diameter, 6 to 8 μm), transit the pulmonary circuit, and variably persist in the circulation, depending on their shells and the physical properties of the contained gas. Microspheres strongly reflect fundamental imaging frequencies and also resonate within ultrasonic fields, producing relatively strong harmonic frequencies. s a result, microspheres are hyperechoic in the bloodstream and light up the cardiac chambers, improving detection of the left ventricular endocardial border. ecause more than half of all echocardiograms are obtained to assess left ventricular function and because 5% to 25% of examinations (depending on a number of factors) are suboptimal for accurately assessing all endocardial segments, the clinical use of contrast agents, particularly for stress echocardiography, has increased dramatically. The first FD-approved agent consisted of an albumen shell containing air. ir is highly soluble in blood, however, so it rapidly leaks out of the microsphere, causing rapid bubble shrinkage and relatively poor microsphere persistence in the circulation. Newer FDapproved contrast agents have less permeable shells that are filled with high-molecular-weight inert gases with low solu- FIGURE pical-window three-dimensional volume data set representation. nyplane two-dimensional images (apical fourchamber, two-chamber, and short-axis views) have been selected retrospectively for simultaneous moving-image display and subsequent volume and segmental wall-motion analysis.

36 128 chapter 5 bility; these agents persist longer 154 and have greater clinical utility for left ventricular opacification. Technical Notes CONTRST RTIFCTS n ultrasound field with sufficient energy (power) will destroy exposed circulating microspheres. The ultrasound system s power-output setting must be adjusted downward during contrast imaging to avoid apical swirling, which may be particularly prominent with low-flow states such as dilated cardiomyopathy or an apical aneurysm. With local bubble destruction, absence of near-field left ventricular contrast can be mistaken for an apical mural thrombus. On the display screen, the ultrasound system s power output is shown as the mechanical index (MI), which is a unitless indicator of the negative acoustic pressure within an ultrasound field. To achieve relatively uniform blood-pool contrast, the MI should be reduced to 0.5. CONTRST TTENUTION This is another common artifact that occurs when overly concentrated bubbles overreflect the ultrasound signal at shallow depths, obscuring the blood pool at greater depths. ecause of limited contrast persistence and eventual dilution, attenuation is a transient phenomenon. It can be minimized by gradual contrast injection. lternatively, image acquisition can be delayed until the attenuation resolves. Left ventricular attenuation in the parasternal views can occur because of overlying contrast material within the intervening right ventricular chamber, so apical windows are generally superior for left ventricular contrast echocardiography. Other important contrast echocardiography artifacts exist, and they warrant further detailed study. Contrast Harmonics When used with fundamental frequency imaging alone, contrast echocardiography improves left ventricular endocardial-border detection. Modern ultrasonographic systems are also configured to image contrast agents in harmonic mode by transmitting at one frequency (e.g., 2 MHz) and constructing images based only on the returning first harmonic frequency (e.g., 4 MHz for a transmitted frequency of 2 MHz). ecause high-amplitude fundamental frequencies that return from the soft tissue are ignored, the myocardium appears very dark owing to its relative lack of contrast. Conversely, the adjacent blood pool is very bright, as it is populated by high concentrations of microspheres emitting harmonic frequencies. Contrast harmonic mode improves the diagnostic accuracy of endocardial border detection (Fig. 5.19C), including identification of segmental wall-motion abnormalities and assessment of left ventricular volume. This mode can also be used to detect luminal filling defects caused by thrombi. Color-Scale (-Color) Imaging The echocardiograph machine produces a gray-scale image based on the intensity of the returning signal within a defined dynamic range. Whereas the most intense echoes appear almost white, the weakest processed signals are darkest gray. The familiar gray-scale display allows interpreters to roughly distinguish certain tissue types (e.g., scarred or calcified tissue is usually much brighter than normal myocardial or leaflet tissue). Manufacturers routinely provide a colorized gray-scale option, also referred to as pseudocolor or color (not to be confused with -mode imaging). lthough resultant recruitment of the high-resolution retinal cone receptors is theoretically beneficial for recognizing faint structures (endocardial borders, thrombus, etc.), this modality is probably only equivalent to gray-scale imaging, 155 and its use is based mainly on the examiner s choice and the ambient lighting conditions. In our laboratory, selective color is used according to sonographer preference (Figs. 5.14C, 5.16, and 5.19C), although it is not used in combination with color Doppler imaging, since color-flow Doppler information can be obscured. Three-Dimensional Echocardiography The cardiac anatomy is complex, curvilinear, and constantly moving. Throughout the cardiac cycle, its component features change their configuration and position within 3D space. While observing the systematically acquired 2D images described previously in this chapter, experienced echocardiographers, in effect, assemble a 3D construct of the heart within their brain. Recording, measuring, and conveying this construct to others is problematic, however. In the right hands, 2D echocardiography is good enough for many clinical purposes. Nevertheless, realtime 3D echocardiography (sometimes referred to as fourdimensional, given the additional time element) became somewhat of a holy grail for echocardiographers. During the 1990s, static 3D birdcage images utilized spark-gap techniques. This approach was time-consuming and not in real time, although it showed a parity between 3D echocardiography with magnetic resonance imaging (MRI) for determining left ventricular volume, ejection fraction, and important anatomic relationships The first recognizable moving 3D anatomic reconstructions became possible during the early 1990s, using painstaking methods of sequential electrocardiographic and respiratory phasegated linear or rotational, incremental, sequential scanning of planar digital images. 159,160 These images, derived from ordinary 2D imaging transducers, assembled the planar data (pixels) into a 3D volumetric data set (voxels) for off-line reconstructions. ecause the data sets were acquired from numerous different cardiac cycles (as in cardiac MRI or ultrafast computed tomography) the potential for motion artifacts was great. However, this phase of development led to important imaging concepts, such as surface renderings (Fig. 5.10C), and validation of 3D quantitative methods. Recently, after undergoing substantial evolution, realtime 3D pyramidal volume data sets became obtainable at acceptable resolutions and frame rates during single cardiac cycles, without the need for sequential scanning methods. Now available commercially, this technology is a descendant of matrix-array transducer technology, as initially described by Sheikh and associates. 161 Currently, large-

37 introduction to echocardiography 129 FIGURE Parasternal long-axis three-dimensional volume data set representation with simultaneous display of orthogonal two-dimensional image planes: left ventricular long- () and short-axis () views from the same cardiac cycles. volume 3D data sets can be assembled from four cardiac cycles recorded during a single breath-hold. Data from each cycle are assembled, reducing the potential for a motion artifact. Smaller-volume data sets can be acquired from a single cardiac cycle, permitting high-resolution morphologic analysis. Current 3D technology permits the simultaneous display of orthogonal imaging planes selected from within the volumetric data set. The instantaneous display of any-plane 2D images enhances the viewer s appreciation of anatomic relationships and allows optimal 2D planar images (Figs. 5.45, 5.48, and 5.49) to be constructed from a volumetric data set off-line, potentially streamlining image acquisition and avoiding apical foreshortening. Color Doppler data may also be rendered in 3D, thereby potentially improving the quantitation of regurgitant lesions. However, both 3D and 2D imaging remains subject to the same physical principles of ultrasonography, which can result in artifacts. pplication of various echocardiography contrast and harmonic-imaging techniques, including 3D Doppler and 3D parametric imaging, is under clinical investigation. Left Ventricular ssist Device ssessment Several varieties of ventricular assist devices are either under investigation or have been approved for clinical use. The standard echocardiography examination, with certain easy-to-perform modifications, is a viable means of following up both device and native cardiac function. 60,63,64,162,163 Routine anatomic and hemodynamic echocardiography assessment is feasible. M-mode evaluation of the native aortic valve (Fig. 5.50) during routine device speed-change evaluations can be used to determine the cycle rate (pulsatile pusher-plate devices) or impeller rotational speed (axial-flow pumps) at which aortic valve opening ceases, indicating complete device support. Pulsed and CW Doppler studies of the device at both its inlet (Fig. 5.51,) and outlet (Fig. 5.51C,D) cannulas are done to assess pump performance. y subtracting the pulsed Doppler-derived LVOT stroke volume or cardiac output (see Doppler discussion, above) from the RVOT cardiac output (total cardiac output), flow in the ventricular assist device can be determined. lthough few clinical data exist, appropriate pump speed settings may be selected accordingly. The Digital Echocardiography Laboratory ecause an echocardiogram consists of a large volume of moving-image data, super-vhs videotape has traditionally been the most cost-effective review and archival medium. However, thanks to recent advances in computer software and hardware, echocardiography laboratories are rapidly moving from the videotape era to the digital age. With digital technology, the examination is broken up into a series of discrete moving-image loops, each of which can be rapidly retrieved and viewed as often as necessary for interpretation. Digital loops from the current and previous exams may be displayed side by side for comparison. Sharing digital exams with colleagues is easy, causes no degradation in quality, and can be done throughout a hospital or clinic via Picture,

38 130 chapter 5 C FIGURE Left ventricular assist device (LVD) assessment. M-mode imaging of the aortic valve cusps in a patient with a continuous axial flow left ventricular assist device during different pump speed settings: () 8000 rpm; () 9000 rpm; (C) 10,000 rpm; (D) 11,000 rpm. rrows ( C) indicate the period of leaflet opening, D which decreases incrementally as the pump speed is increased, with shared left ventricular output between the device and the native left ventricular outflow tract. In D, the aortic valve does not open, indicating complete LVD support. Note: Device inlet location = LV apex; device outlet location = ascending aorta (not shown). rchiving, and Collection System (PCS). In contrast, videotapes are difficult to retrieve from storage and can be lost or broken. Videotape examinations can be reviewed only by using time-consuming rewind and fast-forward procedures, and video copying degrades the image quality. In addition to its above-mentioned advantages, digital echocardiography permits efficient off-line data analysis, reduces overall physician interpretation times, incorporates standardized reporting tools, and reduces storage needs. digital echocardiography laboratory facilitates quality-assurance measures. For all these reasons, conversion to digital echocardiography is desirable and cost-effective. 5 Summary Since its initial introduction more than 50 years ago, echocardiography has emerged as the most frequently used cardiac imaging technique. In many cases, it provides a definitive anatomic and hemodynamic evaluation of simple and complex cardiac pathology. lthough generally safe, this powerful technique is potentially subject to image acquisition and interpretation errors. ccordingly, a field of professional echocardiography has emerged to address matters of continuing medical education, to establish training, practice, and quality-assurance guidelines, and to research emerging technologies and clinical applications. This chapter has covered basic concepts regarding the physical principles of ultrasound and has presented a spectrum of common clinical applications. It has presented the basic transthoracic and transesophageal echocardiography views as a basis for understanding subsequent echocardiography chapters within this book. This chapter presents the modern echocardiography machine as a potentially complex multimodal device. Many of the newer imaging modes are not yet routinely performed. However, their selected application, when appropriate, may facilitate pathophysiologic diagnosis and thus improve patient care.

39 introduction to echocardiography 131 C FIGURE (,) Left ventricular assist device (LVD) inlet cannula assessment, apical four-chamber view. Color Doppler (arrow, ) indicates exit of blood from the left ventricular apex into a pulsatile, pusher-plate type LVD. pical inlet-cannula flow ceases (arrow, ) during the pulsatile LVD ejection phase (no device filling occurs). (C,D) LVD outlet cannula flow assessment using pulsed Doppler with the sample volume placed within the outlet D conduit in a modified parasternal or modified apical view. (C) Outlet-conduit flow in a patient with a pulsatile, pusher-plate device. Note: Outlet flow is not timed with the cardiac cycle. Forward flow (arrow) can occur during ventricular systole (S) or diastole (D) as timed by the electrocardiographic tracing. (D) In a patient with an axial flow LVD, outlet-cannula flow is phasic with the intrinsic cardiac cycle and unloads the heart continuously. References 1. Quinones M, Douglas PS, Foster E, et al. CC/H clinical competence statement on echocardiography: a report of the merican College of Cardiology/merican Heart ssociation/ merican College of Physicians-merican Society of Internal Medicine Task Force on Clinical Competence. J m Coll Cardiol 2003;41(4): Quinones M, Douglas PS, Foster E, et al. CC/H clinical competence statement on echocardiography: a report of the merican College of Cardiology/merican Heart ssociation/ merican College of Physicians-merican Society of Internal Medicine Task Force on clinical competence. J m Soc Echocardiogr 2003;16(4): Quinones M, Douglas PS, Foster E, et al. merican College of Cardiology/merican Heart ssociation clinical competence statement on echocardiography: a report of the merican College of Cardiology/merican Heart ssociation/merican College of Physicians merican Society of Internal Medicine Task Force on Clinical Competence. Circulation 2003; 107(7): Ehler D, Carney DK, Dempsey L, et al. Guidelines for cardiac sonographer education: recommendations of the merican Society of Echocardiography Sonographer Training and Education Committee. J m Soc Echocardiogr 2001;14(1): Thomas JD, dams D, Devries S, et al. Guidelines and recommendations for digital echocardiography. J m Soc Echocardiogr 2005;18(3): Cerqueira MD, Weissman NJ, Dilsizian V, et al. Standardized myocardial segmentation and nomenclature for tomographic imaging of the heart. statement for healthcare professionals from the Cardiac Imaging Committee of the Council on Clinical Cardiology of the merican Heart ssociation. Int J Cardiovasc Imaging 2002;18(1): Cerqueira MD, Weissman NJ, Dilsizian V, et al. Standardized myocardial segmentation and nomenclature for tomographic imaging of the heart: a statement for healthcare professionals from the Cardiac Imaging Committee of the Council on Clinical Cardiology of the merican Heart ssociation. J Nucl Cardiol 2002;9(2): Cerqueira MD, Weissman NJ, Dilsizian V, et al. Standardized myocardial segmentation and nomenclature for tomographic imaging of the heart: a statement for healthcare professionals from the Cardiac Imaging Committee of the Council on Clinical Cardiology of the merican Heart ssociation. Circulation 2002;105(4): Gardin JM, dams D, Douglas PS, et al. Recommendations for a standardized report for adult transthoracic echocardiography: a report from the merican Society of Echocardiography s Nomenclature and Standards Committee and Task Force for a