Echocardiography is increasingly used as a diagnostic

Transcription

1 Substernal Epicardial Echocardiography: A Recommended Examination Sequence and Clinical Evaluation in Patients Undergoing Cardiac Surgery Colin F. Royse, MBBS, MD, Alistair G. Royse, MBBS, MD, Ajay Bharatula, BMedSci, James Lai, MBChB, FRCA, Michael Veltman, MBBS, FANZCA, Louise Cope, RN, and Ajay Kumar, MBBS, FANZCA Department of Pharmacology, University of Melbourne, Melbourne; Departments of Anesthesia and Pain Management and Cardiothoracic Surgery, The Royal Melbourne Hospital, Melbourne; Department of Anesthesia, Westmead Hospital, Westmead; and Department of Anesthesia, Royal Perth Hospital, Perth, Australia Background. Substernal epicardial echocardiography is a novel echocardiography window, utilizing a modified mediastinal drain incorporating a sleeve for the insertion of a transesophageal echocardiography probe. Methods. Forty-six patients undergoing cardiac surgery from two institutions were evaluated, and an examination sequence was developed. Results. An 11-view examination is presented as a consensus between the two institutions. In clinical usage, there were no major complications attributable to use of the device. Minor air leaks occurred in 6 patients, and 2 cases of sternal wound infection occurring in a cluster of Echocardiography is increasingly used as a diagnostic monitor in the operating room and subsequently in the intensive care unit. Ideally, transthoracic imaging should be used because it is noninvasive, but it is often limited in this setting because of poor image quality. Transesophageal echocardiography (TEE) provides superior image quality but is limited by the need to sedate patients in order to conduct the study. Although it is considered safe, TEE is an invasive procedure and carries a very low risk of mortality (0.01% to %) and serious complications ( 3%) [1]. In the critical care environment, Colreavy and associates [2] reported complications in 1.6% of patient examinations. In its current form, it is difficult to use echocardiography as a continuous monitor of cardiovascular function, but rather, it is used as a diagnostic tool when other measurements of cardiac function, such as the pulmonary artery catheter, alert the clinician to a deteriorating clinical state. Substernal epicardial echocardiography (SEE) is a novel echocardiography window allowing excellent imaging of the heart in the intensive care unit environment [3, 4]. The Medtronic SEEIT cannula (Medtronic, Minneapolis, MN) is a 9-mm mediastinal drain that incorporates a blind-ended sterile 11-mm or 16-mm silicon sleeve into which a TEE probe is inserted (Fig 1). The potential benefits of this approach are that high-quality echocardiography images can be obtained in awake and Accepted for publication Feb 18, Address reprint requests to Dr Royse, PO Box 1022, Research, Victoria, Australia, 3095; colin.royse@mh.org.au. infections are reported, but causation was not attributed to use of the device. There were no significant differences in measurements of the aortic valve area, pulmonary artery diameter, left ventricular outflow tract dimension, or the sinotubular junction between substernal and transesophageal examinations. All 16 wall-motion segments were well visualized in most patients with substernal epicardial echocardiography. Conclusions. Substernal epicardial echocardiography is a safe device for use in the postoperative environment. (Ann Thorac Surg 2004;78:613 9) 2004 by The Society of Thoracic Surgeons extubated patients, and that the probe can be left in situ for continuous monitoring. Postoperatively, awake and extubated patients described dull pressure type pain as the probe is advanced through the rectus sheath, but no discomfort during the examination [4]. The image quality is reported to be excellent and at least equal to that obtained with TEE [3, 4]. The views obtained are quite different in position and orientation from those encountered in either transthoracic or transesophageal imaging. The use of this technology will be enhanced by description of a standardized examination sequence designed to perform a complete echocardiography evaluation. The aims of this study were to produce a standardized examination protocol and to compare anatomical accuracy with TEE. The study represents a collaboration between the Royal Melbourne Hospital and Westmead Hospital investigator groups. Material and Methods After approval from the Royal Melbourne Hospital and Westmead Hospital Human Ethics Committees, written informed consent was obtained from 47 patients undergoing cardiac surgery. One patient was withdrawn from the study because the SEEIT cannula was the wrong size This article has been selected for the open discussion forum on the CTSNet Web site: by The Society of Thoracic Surgeons /04/$30.00 Published by Elsevier Inc doi: /j.athoracsur

2 614 ROYSE ET AL Ann Thorac Surg SUBSTERNAL EPICARDIAL ECHOCARDIOGRAPHY 2004;78:613 9 After application of the sternal wound dressings, 20 ml 0.9% saline was injected through the Luer connector of the SEE cannula. The TEE probe was then inserted into the SEE cannula and advanced until the first view was obtained. We developed a sequence of 11 views based on collaborative experience between the Westmead Hospital and Royal Melbourne Hospital research groups. The SEE drain was left in situ postoperatively and removed on the second postoperative day. The SEEIT cannula is about twice the size of a standard 24-gauge chest drain. It is compressible, but returns to the origional shape after the deforming pressure is removed. Fig 1. The substernal epicardial echocardiography cannula is shown inserted through the left rectus sheath and positioned so that the tip lies over the aortic arch and right brachiocephalic artery. for the adult TEE probe. All patients received a pulmonary artery catheter (834HF75; Baxter Healthcare, Irvine, CA), an indwelling peripheral arterial catheter, and transesophageal echocardiography (Omniplane II transducer, powered by Sonos 5500 machine; Philips Medical Systems, Andover, MA) as part of their routine management. Anesthetic Procedure Patients were anesthetized with a combined regional and general anesthetic technique at the Royal Melbourne site and by general anesthetisia at the Westmead site. All patients were still sedated at the time the study was performed. Operative Procedures The chest was opened through median sternotomy. Before chest wall closure, a 2.5-cm to 3-cm horizontal incision was made through the center of the left rectus sheath to allow insertion of a 16-mm SEE drain (SEEIT cannula). The drain rests over the pericardium so that its blind end is positioned over the aortic arch and right brachiocephalic artery (Fig 1). Echocardiography Before sternal closure, a standard intraoperative TEE examination using an adult multiplane probe was conducted according to published guidelines (Royal Melbourne site only) [5]. The probe was then removed and disinfected before use in the SEE cannula. Comprehensive SEE Examination An important phase in the study was development of a standard SEE examination. Initially, we attempted to replicate the standardized TEE views. However, the axis of the drain is oblique to the axis of the esophagus. Short-axis (SAX) views of the heart had the same leftright orientation as TEE images; the right side of the patient is seen on the left of screen. However, long-axis (LAX) views of the heart had the opposite left-right orientation to TEE views. The SEE views presented anterior structures on the apex of the sector whereas the TEE views presented them on the bottom of the sector. Based on the primary requirement of SEE to monitor postoperative ventricular function, we decided that it was important that SAX views of the ventricles resemble that of transesophageal and transthoracic echocardiographies. Hence the views were not left-right inverted. Most other views require a degree of reorientation for the surgeon or echocardiographer familiar with TEE. The development of images involved recording the angle at which a view was obtained, and the mean angle is presented (the angle may vary 20 to 30 degrees between subjects). This information was used to determine the typical angle required to obtain a good quality view. We recommend that tip of the probe should not be angulated with the flexion or lateral movement controls in order to minimize the possibility of compression of cardiac structures by the probe. The 11 SEE views are shown in Figure 2, and an example of the mid-sax view is shown in Figure 3 to illustrate the fidelity of image obtained. Comparable views for TEE and SEE are shown in Table 1. The views are classified according to probe position within the cannula sleeve and transducer angulation. The recommended sequence is in order 1 to 11. The order of the sequence is based on obtaining anatomical information, followed by left ventricular function information, and finally assessment of the aorta. Assessment of the aorta is performed last because pathology in this area is less likely to be a cause of hemodynamic compromise, compared with the valves or ventricles. There are major probe manipulations within the sheath: first, advancing the probe to the mid position; second, withdrawl to the proximal position, and third, advancement to the distal position. At each position, different views are obtained by altering the angle of insonation with minimal probe manipulation.

3 Ann Thorac Surg ROYSE ET AL 2004;78:613 9 SUBSTERNAL EPICARDIAL ECHOCARDIOGRAPHY 615 Fig 2. The 11 views are illustrated in the recommended sequence order. The probe drawing to the left of each view illustrates the position of the probe within the cannula. (A anterior; AL anterolateral papillary muscle; Arch aortic arch; AS anteroseptal; Asc-Ao ascending aorta; AV aortic valve; I inferior; IAS interatrial septum; IVS interventricular septum; L lateral; LA left atrium; LAX long axis; LCC left coronary cusp; LPA left pulmonary artery; LV left ventricle; LVOT left ventricular outflow tract; MPA main pulmonary artery; MV mitral valve; NCC noncoronary cusp; P posterior; Pap papillary muscle; PM posteromedial papillary muscle; Pulm-Art pulmonary artery; PV pulmonary valve; RA right atrium; RCC right coronary cusp; RPA right pulmonary artery; RV right ventricle; RVOT right ventricular outflow tract; S septal; SAX short axis; SLTV septal leaflet of tricuspid valve; ST-Junct sinotubular junction; SV sinus of Valsalva; TV tricuspid valve.) 1. FOUR-CHAMBER LAX. The probe is inserted at zero degrees into the midcannula position to identify an image similar in nature to the TEE midesophageal four-chamber view. The probe lies anterior to the right ventricle, with the interventricular septum in the middle of the sector. Minor probe turning and angle rotation (axial rotation of multiplane angle) may be required to view atrioventricular valves and interatrial septum. 2. THREE-CHAMBER LAX. The probe is rotated (10 to 30 degrees) to bring the left-ventricular outflow tract and aortic valve into LAX. This view has features similar to the TEE midesophageal LAX view. Minor rotation allows visualization of the mitral valve. 3. AORTIC ROOT LAX. Advancing (push toward distal tip) the probe and rotating it (30 to 45 degrees) to center the aortic valve produces a view comparable to a TEE midesophageal aortic valve LAX view. Fig 3. The mid-sax (short-axis) view is shown at end diastole. 4. AORTIC VALVE SAX. The TEE probe is rotated forward approximately 90 degrees until the aortic valve is seen in SAX. This view differs from the TEE midesophageal aortic valve SAX view because both atria and part of the right ventricular outflow tract are also seen as opposed to left ventricular outflow tract and pulmonary valve.

4 616 ROYSE ET AL Ann Thorac Surg SUBSTERNAL EPICARDIAL ECHOCARDIOGRAPHY 2004;78:613 9 Table 1. Similar Views for SEE and TEE SEE Four-chamber LAX Three-chamber LAX Aortic root LAX Aortic valve SAX Basal SAX Mid papillary SAX Apical sax Ascending aorta SAX Ascending aorta LAX Arch LAX Pulmonary artery LAX TEE ME 4-chamber ME LAX ME aortic valve LAX ME aortic valve SAX TG basal SAX TG mid SAX UE ascending aorta SAX UE ascending aorta LAX UE arch LAX Part of UE ascending aorta SAX and part of ME RV inflow-outflow LAX long axis; ME mid esophageal; RV right ventricular; SAX short axis; SEE substernal epicardial echocardiography; TEE transesophageal echocardiography; TG transgastric; UE upper esophageal. 5. BASAL SAX. From the aortic valve, withdrawal of the probe captures views of left ventricular myocardial excursion and basal regional wall-motion segments. The probe now lies over the interventricular septum. The left ventricle is seen on the right hand side of the sector, and the right ventricle is seen on the left side of the sector. This view is characterized by the fish-mouth motion of mitral valve leaflets as seen in the TEE transgastric basal SAX. 6. MID SAX. Further withdrawal highlights the posteromedial and anterolateral papillary muscles as seen in TEE transgastric mid SAX. Midventricular regional wallmotion segment excursion is observed. Slight probe angulation may be necessary to compensate for displacement of the heart. 7. APICAL SAX. Further withdrawal from the mid-sax position reveals left ventricular apical regional wall-motion segments. The right ventricle may or may not be seen depending on the degree of axial displacement of the heart and position of the sheath. 8. ASCENDING AORTA SAX. The probe is rotated back to zero degrees and advanced into the distal end of the cannula until the ascending aorta is seen. The probe lies directly over the ascending aorta. This view is similar to the TEE midesophageal ascending aortic SAX. 9. ASCENDING AORTA LAX. The probe is rotated 90 degrees to visualize the ascending aorta in LAX, and is similar to the TEE midesophageal ascending aortic LAX view. 10. ARCH LAX. By advancing the probe toward the distal end of the cannula, a LAX view of the aortic arch, similar to the TEE upper esophageal aortic arch LAX, is obtained. The probe lies over the proximal arch with the distal arch seen in a posterior direction. 11. PULMONARY ARTERY LAX. The final view is obtained by slight withdrawal and anticlockwise turning of the probe until the pulmonary artery and pulmonary valve are seen in LAX. Regional Wall-Motion Segments Images were used to identify the 16 standard regional wall-motion segments [5]. A positive identification was recorded if an individual wall-motion segment could be tracked from end-diastole to end-systole. The transgastric mid-sax, transgastric basal SAX, midesophageal four-chamber, midesophageal two-chamber, and midesophageal LAX views were used for TEE; and the basal SAX, mid-sax, and apical SAX views were used to identify the segments for SEE. Accuracy of Two-Dimensional Measurements 1. AORTIC VALVE ORIFICE AREA. To measure aortic valve orifice area (cm 2 ) we used planimetry by the triangle approximation method [6] in the midesophageal aortic valve SAX (TEE) and aortic valve SAX (SEE) views. Where valves showed excessive calcification, direct planimetry was used instead. 2. LEFT VENTRICULAR OUTFLOW TRACT DIAMETER. The left ventricular outflow tract diameter (cm) is the distance between the points marking the base of the aortic valve leaflets from midesophageal aortic LAX (TEE) and aortic root LAX (SEE) views. 3. SINOTUBULAR JUNCTION DIAMETER. The sinotubular junction diameter (cm) is the distance between the points marking the transition from aortic sinus to ascending aorta in the midesophageal aortic LAX (TEE) and aortic root LAX (SEE) views. 4. PULMONARY ARTERY DIAMETER. The distance across the main pulmonary artery (cm) was obtained from the midesophageal ascending aortic SAX (TEE) and ascending aortic SAX or pulmonary artery LAX (SEE) views. Statistical Analysis Paired-samples Student s t test was used for comparisons of anatomical dimensions. The correlation coefficient (r) was Pearson s product-moment. A Bland-Altman plot was then constructed to illustrate the limits of agreement, using their formula for small sample size [7]. Significance was defined as p less than Analysis was done using SPSS V11.0 (SPSS, Chicago, IL). Results Clinical Usage In the Royal Melbourne Hospital experience, 21 patients completed SEE examinations (16 coronary artery bypass graft [CABG], 2 aortic valve, 2 mitral valve, 1 double valve [aortic and mitral], and 1 combined mitral valve and CABG operations). Two patients had postoperative sternal wound infections; the infections occurred within a cluster of infections across the surgical unit, and the cause was not ascribed to the use of the SEE cannula. In the Westmead Hospital experience, 25 patients completed SEE examinations. Twenty-one patients had

5 Ann Thorac Surg ROYSE ET AL 2004;78:613 9 SUBSTERNAL EPICARDIAL ECHOCARDIOGRAPHY 617 CABG, 3 patients had aortic valve replacement, and 1 patient had combined aortic valve replacement and mitral valve repair. In 2 patients, the TEE was unable to be passed through the SEE sleeve. Removal and inspection of the cannula revealed no fault or physical blockage of the cannula in either case, and the cause was considered most likely due to inadequate size of the incision (the SEE cannula is thick silicon, but is compressible). There were no major complications reported, but minor air leaks were noted in 6 patients. In both hospitals, the SEE cannula was removed within the first 48 hours after surgery, and there were no cases of tube perforation or blockage. Regional Wall-Motion Segments A description of adequate imaging of left ventricular regional wall-motion segments for SEE and TEE is shown in Table 2. All 16 wall-motion segments were adequately viewed in most patients with both examination methods. The basal septal wall was most likely to be missed by SEE, whereas the apical segments are most likely to be missed with TEE. Accuracy of Two-Dimensional Measurements Differences between TEE and SEE measurements for the aortic valve area, pulmonary diameter, left ventricular outflow tract dimension, and sinotubular junction diameter are shown in Table 3. There were no significant differences between TEE and SEE measurements. Table 2. Adequacy of Wall Motion Segments Analysis for SEE and TEE Wall Motion Segment TEE Not SEE Not Basal Anteroseptal Anterior Lateral Posterior Inferior Septal Mid papillary Anteroseptal Anterior Lateral Posterior Inferior Septal Apical Anterior Lateral Inferior Septal SEE substernal epicardial echocardiography; TEE transesophageal echocardiography. : wall segment tracked from end diastole to end systole; not viewed: wall segment not tracked from end-diastole to end-systole. Table 3. Comparison of Anatomical Structure Measurements Between SEE and TEE Variable Aortic value area (cm 2 ) Pulmonary diameter (cm) LVOTD (cm) ST junction diameter (cm) Comment r Mean Difference Limits of Agreement Lower Upper p Value p Value LVOTD left ventricular outflow tract diameter; SEE substernal epicardial echocardiography; ST sinotubular; TEE transesophageal echocardiography. Difference is the value for TEE SEE. Limits of agreement as per Bland-Altman analysis using the formula for small sample size. The p value is the raw statistical value using paired samples t test, and the p value is the adjusted statistic for four hypotheses using the Ryan-Holm Bonferroni step-down procedure. Our study showed that insertion and use of the SEE cannula is achievable, and that anatomical evaluation with it is equivalent to TEE. We have defined a comprehensive examination comprising 11 standardized views to facilitate ease of use with this technology. Role of SEE The potential therapeutic impact of echocardiography in the intensive care unit is considerable. In patients with abnormal hemodynamics, the use of echocardiography can lead to a change in management in both cardiac and noncardiac intensive care patients in 40% to 70% of diagnostic occasions [2, 8 11]. Echocardiography provides superior diagnostic information to that obtained from pulmonary artery catheter monitoring, allowing anatomical and functional assessment of the hemodynamic status. Additionally, echocardiography allows direct assessment of ventricular volume as opposed to indirect assessment obtained from a pressure-based monitoring system. Although noninvasive echocardiography is preferable to TEE, the image quality during transthoracic imaging may be inadequate to obtain sufficient diagnostic information. However, TEE is at least semi-invasive and also requires sedation in order to perform it, having the potential problem of exacerbating an already unstable hemodynamic state. Colreavy and associates [2] reported the complication rate of 1.6% in critically ill patients undergoing TEE examinations, including hypotension pulmonary aspiration and oropharyngeal bleeding, none of which cause long-term morbidity. The advantages of SEE over TEE relate to the ability to perform repeated examinations without requirement for sedation or intubation, and to allow prolonged examination for the continual assessment of hemodynamic variables such as left ventricular volume and systolic func-

6 618 ROYSE ET AL Ann Thorac Surg SUBSTERNAL EPICARDIAL ECHOCARDIOGRAPHY 2004;78:613 9 tion. There are few data, however, on the use of this technology and whether it compares favorably with TEE [3, 4]. Hanlon and associates [3] described their results of 13 patients studied with the cannula prototype. They used a pediatric probe in most patients and found excellent imaging of the heart in most patients. Of concern, however, is that they reported an incident of sleeve perforation with the TEE probe. Furnary and associates [4] reported a series of 21 patients using the commercially available SEE IT cannula, which has an 11-mm sleeve suitable for a pediatric TEE probe. They compared images obtained with SEE against those obtained with TEE, and found SEE to be superior when imaging anterior and right ventricular structures, and TEE superior when imaging posterior structures such as the left atrium and pulmonary veins. Additionally, they found the probe easy to insert and did not report any complications. In our study, we used the SEEIT cannula, which incorporates a 16-mm sleeve suitable for use with a standard adult multiplane probe. The study concurs with that of Furnary and associates [4] in that the image quality is excellent in most patients, but the limitations of examination relate to posterior structures including the distal arch and descending aorta. The most important benefit of SEE in the intensive care unit is to monitor ventricular function and volume, and to diagnose the cause of hemodynamic instability. The excellent view of the ventricles in cross section makes this echocardiographic window ideal for these purposes. In tamponade, for example, the right ventricle is well visualized, being an anterior structure, and compression by hematoma would be easily seen. Continual monitoring with SEE could lead to early detection of tamponade. There will be variability in the exact orientation of the image, caused by variations in the orientation of the cannula to the heart. In our experience, the cannula was inserted through the left rectus sheath and positioned so that the tip usually lies over the aortic arch and right brachiocephalic artery. This orientation lies over the long axis of the heart and allows imaging of the ascending aorta and proximal arch. The views obtained are quite different in both orientation and positioned to those obtained with TEE. The 11-view examination that we describe allows examination of all valves, all wall-motion segments, the ascending aorta and proximal arch, and Doppler examination of all valves. Safety In the two parallel arms of the study, a total of 46 patients were evaluated with the SEE cannula. There were no problems related to the insertion of the cannula, although the qualitative opinion was that the cannula was large, and the incision required was considerably larger than that required for a standard mediastinal chest drain. In the Westmead Hospital experience, the TEE probe could not be inserted through a rectus sheath in 2 patients, which probably related to inadequate size of the incision (the cannula is compressible). In all other cases, the probe passed easily into the sleeve and was easy to manipulate within the sleeve. The design of the cannula is still in evolution, with the revised version having a rounder and smaller profile that is likely to overcome the problems of large insertion incisions and air leakage. There were no major complications directly attributable to the use of the cannula, or any perforations of the sleeve. Sleeve perforation was reported with the prototype cannula by Hanlon and associates [3], but with the commercially available version, this complication was considered very unlikely by the manufacturer. In our series, there were no reports of tube perforation after inspection of the removed device. Minor air leaks may be attributable to the larger incision required to insert the cannula. In the Royal Melbourne Hospital series, we reported 2 patients who had sternal wound infection. These cases, however, occurred with a cluster of sternal wound infections within our surgical unit, and we believe that the sternal wound infection was an association with the cannula rather than causation. There have been no other sternal wound infections reported in the literature to date with the cannula. We do believe, however, that is prudent to disinfect the TEE probe before use in order to minimize the risk of contamination of the cannula. The study was designed to clinically evaluate the SEE cannula and was not designed to measure the therapeutic impact of it. Although we are confident that the device is easy to insert and to use, and that the information obtained from it is equivalent to that derived from TEE, we do not have data to comment on this clinical utility in the perioperative setting. It is likely, however, to facilitate high-quality echocardiography imaging, which will impact on clinical management. Further research is required to further evaluate the device in the intensive care environment. In conclusion, the SEE cannula is easy to insert and use, and appears safe to use in the perioperative environment. Anatomical assessment is comparable with that obtained by TEE. We thank Karen Groves and Maal Yoganathan for their assistance with data collation and offline analysis; John Ludbrook (Biomedical Statistical Consulting Pty, Ltd) for statistical advice and evaluation of the manuscript; Drs R. Chard, R. Costa, H. Patterson, I. Nicholson, W. Meldrum-Hanna, M. Morris, and H. Leggett; and the nursing staff of the operating theater and intensive care units of the Royal Melbourne and Westmead Hospitals for their support in conducting the study. The study was supported by an educational grant from Medtronic, Inc, and equipment support was from Philips Medical Systems. References 1. Thys DM, Abel M, Bollen BA. Practice guidelines for perioperative transesophageal echocardiography. A report by the American Society of Anesthesiologists and the Society of Cardiovascular Anesthesiologists Task Force on Transesophageal Echocardiography. Anesthesiology 1996;84: Colreavy FB, Donovan K, Lee KY, Weekes J. Transesophageal echocardiography in critically ill patients. Crit Care Med 2002;30: Hanlon JT, Lowe RI, Funary A. Substernal epicardial echocardiography: a new ultrasonic window to the postoperative heart. J Am Soc Echocardiogr 2000;13:35 8.

7 Ann Thorac Surg ROYSE ET AL 2004;78:613 9 SUBSTERNAL EPICARDIAL ECHOCARDIOGRAPHY Furnary AP, Siqueira C Jr, Lowe RI, et al. Initial clinical trial of substernal epicardial echocardiography: SEEing a new window to the postoperative heart. Ann Thorac Surg 2001; 72(Suppl):S Shanewise JS, Cheung AT, Aronson S, et al. ASE/SCA guidelines for performing a comprehensive intraoperative multiplane transesophageal echocardiography examination. Recommendations of the American Society of Echocardiography Council for Intraoperative Echocardiography and the Society of Cardiovascular Anesthesiologists Task Force for Certification in Perioperative Transesophageal Echocardiography. Anesth Analg 1999;89: Darmon PL, Hillel Z, Mogtader A, et al. Cardiac output by transesophageal echocardiography using continuous-wave Doppler across the aortic valve. Anesthesiology 1994;80: ; discussion 25A. 7. Bland JM, Altman DG. Measuring agreement in method comparison studies. Stat Meth Med Res 1999;8: Schmidlin D, Schuepbach R, Bernard E, et al. Indications and impact of postoperative transesophageal echocardiography in cardiac surgical patients. Crit Care Med 2001;29: Poelaert JI, Trouerbach J, De Buyzere M, et al. Evaluation of transesophageal echocardiography as a diagnostic and therapeutic aid in a critical care setting. Chest 1995;107: Oh JK, Seward JB, Khandheria BK, et al. Transesophageal echocardiography in critically ill patients. Am J Cardiol 1990;66: Khoury AF, Afridi I, Quinones MA, Zoghbi WA. Transesophageal echocardiography in critically ill patients: feasibility, safety, and impact on management. Am Heart J 1994;127: INVITED COMMENTARY Over the past few decades, the utilization and popularity of intraoperative echocardiography has surged as its impact on surgical and anesthesia decision making has become increasingly more appreciated. The echocardiographic examination of the cardiac surgical patient may also be useful postoperatively in the intensive care unit for evaluating regional or global cardiac performance, the presence of a pericardial effusion, or the integrity of the surgical procedure. However, the echocardiographic evaluation of the postsurgical patient can be challenging. For example, the insertion and manipulation of a transesophageal echocardiographic (TEE) probe in the postoperative patient may be contraindicated or require heavy sedation, which has the potential to further compromise a hemodynamically unstable patient. In addition, transthoracic echocardiographic (TTE) images are often suboptimal due to difficulties in positioning the patient, interference by surgical dressings, hyperinflated lungs, subcutaneous emphysema, or limited access to the patient in the intensive care unit. In this issue of The Annals of Thoracic Surgery, Royse and associates present a novel echocardiographic window, which involves enclosing a standard adult multiplane transesophageal probe in a sleeve and inserting it through a blind-ended mediastinal drain (Medtronic SEEIT Cannula; Medtronic Corporation, Minneapolis, MN) to obtain a substernal, epicardial cardiac anatomic and hemodynamic evaluation. Proposed advantages of this technique compared with TEE include improved imaging of anterior cardiac structures, increased safety, less patient discomfort, and an alternative echocardiographic window when placement of a TEE probe is contraindicated or cannot be performed. In addition, compared with TTE, a substernal epicardial probe can be left in place to permit continuous monitoring. Certain limitations must also be considered including increased cost, requirement for a mediastinal tube, and occasional difficulty in inserting the probe, imaging posterior structures, or obtaining parallel alignment of a Doppler ultrasound beam for accurate hemodynamic evaluation. However, the practicality of this novel echocardiographic technique is noteworthy as it often permits an overall equivalent and perhaps superior anatomic and hemodynamic evaluation compared with conventional approaches. Although it may be somewhat premature for this technology to be routinely adopted for every cardiac surgical patient, substernal epicardial echocardiography should be considered for anticipated high-risk cardiac surgical patients, including those with significant preoperative ventricular dysfunction, hemodynamic instability, or contraindications to TEE, who may benefit from continuous, relatively noninvasive perioperative monitoring of cardiac performance. In addition, if further investigation can lend credibility to the clinical utility and cost effectiveness of substernal epicardial echocardiography, then the recommended views proposed by Royse and colleagues and standardized proposals for training, competency, and quality control should be given the same consideration for formal adoption as conventional TTE and TEE. Stanton K. Shernan, MD Department of Anesthesiology, Perioperative and Pain Medicine Brigham and Women s Hospital Harvard Medical School 75 Francis St Boston, MA shernan@zeus.bwh.harvard.edu 2004 by The Society of Thoracic Surgeons /04/$30.00 Published by Elsevier Inc doi: /j.athoracsur