Multidetector CT Angiography. Prosthetic Heart Valve Dysfunction 1

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1 Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at CARDIAC IMAGING 1893 Multidetector CT Angiography in Evaluation of Prosthetic Heart Valve Dysfunction 1 CME FEATURE See /rg_cme.html LEARNING OBJECTIVES FOR TEST 2 After completing this journal-based CME activity, participants will be able to: Discuss types of PHVs and their CT characteristics. Describe acquisition parameters and types of image reconstruction required for PHV evaluation with CT. List CT features of PHV dysfunction that must be reported to referring clinicians. INVITED COMMENTARY See discussion on this article by Mammen (pp ). Jesse Habets, MD, PhD Willem P. T. M. Mali, MD, PhD Ricardo P. J. Budde, MD, PhD Prosthetic heart valves (PHVs) are commonly implanted to replace diseased native heart valves. PHV dysfunction is an infrequent but potentially life-threatening condition. In daily clinical practice, transthoracic and transesophageal echocardiography and fluoroscopy are the imaging modalities used for diagnostic evaluation of suspected PHV dysfunction. These modalities may not allow determination of the cause of PHV dysfunction, mostly because of acoustic shadowing. Multidetector computed tomographic (CT) angiography is a promising complementary technique for evaluation of PHVs, especially in patients with PHV obstruction and endocarditis. The CT image quality of PHVs mainly depends on their composition, with most causing only limited artifacts. Retrospectively electrocardiographically gated acquisition is advisable for PHV imaging because it enables dynamic leaflet evaluation and anatomic assessment in both systole and diastole. For accurate image interpretation, dedicated reconstruction in plane with and perpendicular to the PHV leaflets is mandatory. Besides PHV assessment, CT also provides information on the coronary arteries, the location and patency of bypass grafts, the dimensions of the aorta, and the distance between the sternum and right ventricle, information valuable for planning repeat surgery. To achieve the optimal diagnostic yield in PHV imaging, multidisciplinary cooperation between the departments of cardiology, cardiothoracic surgery, and radiology is crucial. Supplemental material available at /lookup/suppl/doi: /rg /-/dc1. RSNA, 2012 radiographics.rsna.org Abbreviations: ECG = electrocardiography, PHV = prosthetic heart valve, PTFE = polytetrafluoroethylene, TAVI = transcatheter aortic valve implantation, TEE = transesophageal echocardiography, TTE = transthoracic echocardiography RadioGraphics 2012; 32: Published online /rg Content Codes: 1 From the Department of Radiology, University Medical Center Utrecht, PO Box 85500, E01.132, 3508 GA Utrecht, the Netherlands (J.H., W.P.T.M.M., R.P.J.B.); and Department of Radiology, Gelre Hospital, Apeldoorn, the Netherlands (J.H., R.P.J.B.). Received January 16, 2012; revision requested March 5 and received April 16; accepted June 27. Supported by grant 2009B014 from the Netherlands Heart Foundation. For this journal-based CME activity, the authors, editor, and reviewers have no relevant relationships to disclose. Address correspondence to J.H. ( J.Habets@umcutrecht.nl). See also the article by Pham et al (pp ) in this issue. RSNA, 2012

2 1894 November-December 2012 radiographics.rsna.org Introduction Prosthetic heart valves (PHVs) are commonly implanted to replace diseased native valves. In 2003, 290,000 patients underwent PHV implantation worldwide (1). During surgery, the diseased native valve is excised and replaced by a PHV. There are two main groups of PHVs: biologic and mechanical PHVs. Biologic PHVs consist of bovine or pericardial tissue, often supported by a frame. Mechanical PHVs consist of metal alloy or carbon components. Biologic PHVs require no anticoagulation but are prone to wear, whereas mechanical PHVs are designed to last decades but require lifelong anticoagulation. In contrast to mechanical PHVs, biologic PHVs degenerate within years due to degeneration of the valve leaflets (2). To detect this degeneration, routine transthoracic echocardiography (TTE) 5 years after implantation is recommended, according to the guidelines of the American Heart Association and European Society of Cardiology (3,4). The type of PHV that is implanted depends on patient characteristics and surgeon preferences. Mechanical PHV dysfunction is a rare but potentially life-threatening condition with a reported prevalence of 0.01% 6.0% (5 9). Patients with suspected PHV dysfunction normally present to the outpatient clinic or emergency department. The cardiologist starts with TTE as the first-line screening tool for PHV dysfunction. TTE is a widely available, noninvasive, and fast screening tool for PHV dysfunction and often demonstrates the effects of PHV dysfunction (ie, increased pressure gradient over the PHV in patients with suspected PHV obstruction). However, TTE often fails to demonstrate the exact cause of dysfunction and thus more imaging is required. In daily clinical practice, TTE is therefore often followed by transesophageal echocardiography (TEE) and fluoroscopy (in patients with mechanical PHVs). TEE can have additional diagnostic value in comparison with TTE, especially in patients with mitral PHVs, because of the use of higher-frequency probes, the proximity of the TEE probe to the left atrium, and its capability for multiplanar assessment. In patients with aortic PHVs, however, PHV disease can be missed because of acoustic shadowing caused by the metal content of the PHV. Fluoroscopy provides information on the opening and closing angles of mechanical PHV leaflets but not biologic PHV leaflets. Even with the findings of TTE, TEE, and fluoroscopy combined, results of the diagnostic work-up can be inconclusive and diagnostic dilemmas may arise. Electrocardiographically (ECG) gated or -triggered multidetector computed tomographic (CT) angiography can contribute additional diagnostic value to the routine clinical work-up in patients with suspected PHV dysfunction, especially patients with PHV obstruction or PHV endocarditis, by demonstrating the anatomic substrate and the extent of disease (2). Besides this diagnostic information, CT angiography can also provide relevant preoperative anatomic information about the presence of coronary artery disease, the location and patency of bypass grafts, the dimensions of the aortic root, and the distance between the right ventricle and sternum. In this article, we present the essential aspects of multidetector CT angiography for evaluation of PHVs, including indications for scanning, considerations for optimal image acquisition, image reconstruction and interpretation, and a proposed structured report for reporting imaging findings and communication with referring medical specialists. Other topics discussed are the surgical technique, types of PHVs, imaging characteristics of normal PHVs, and imaging characteristics of PHVs used in transcatheter aortic valve implantation (TAVI). Patient Selection for and Technical Aspects of Multidetector CT of PHVs Surgical Technique In patients selected for PHV implantation, the diseased valve is excised after exposure and the annular tissue is carefully decalcified. After selection of the appropriate PHV size, the PHV is fixed in place by passing approximately sutures through the suture ring of the PHV and

3 RG Volume 32 Number 7 Habets et al 1895 Figure 1. PHV implantation. (a) Drawing shows implantation of a mitral PHV by using sutures with polytetrafluoroethylene (PTFE) pledgets. Each knot of a single suture is tied individually. (b) CT image shows the pledgets as hyperattenuating structures. Figure 2. Different types of PHVs. Photographs show a Medtronic Hall tilting-disk valve with one leaflet (a), a St Jude Medical bileaflet valve with two leaflets (b), and a Carpentier-Edwards Perimount biologic valve with three leaflets (c). the annulus (Fig 1). PTFE pledgets attached to the sutures are commonly used to diffuse the pressure of the sutures on the annulus. The pledgets appear as hyperattenuating structures ( HU) on CT images (Fig 1) (10). Types of PHVs The two main types of PHVs are mechanical and biologic. In the mechanical PHV group, two different types are distinguished: bileaflet and tilting disk (Fig 2). The composition of each type of PHV is different and has important implications for CT image quality (11 13). Mechanical valve leaflets have specific opening and closing angles that are unique for each PHV type. PHVs are available in different sizes (eg, size 19, size 21, size 23); the implanted size depends on the size of the annulus. The size is not equal to the diameter in millimeters. Characteristics of different PHVs including type, composition, normal opening and closing angles, and CT visibility are presented in Table 1.

4 1896 November-December 2012 radiographics.rsna.org Table 1 Features of Different PHVs by Type and Their Visibility at CT PHVs by Type Manufacturer Metal Content Opening Angle (degrees)* Closing Angle (degrees)* Visibility at CT Mechanical bileaflet ATS Open Pivot Medtronic, Minneapolis, Minn Titanium alloy ring 85 (AVR) 25 (AVR) Unknown Carbomedics Sorin Group USA, Arvada, Colo Titanium alloy ring 78 (AVR and MVR) 25 (AVR and MVR) Very high Duromedics Baxter Healthcare, Santa Ana, Calif Cobalt-chrome alloy ring 78 (AVR), 73 (MVR) 20 (AVR and MVR) Low St Jude Medical St Jude Medical, St Paul, Minn Nickel alloy ring 85 (AVR and MVR) 30 or 25 (AVR and MVR) High On-X On-X Life Technologies, Austin, Tex Titanium alloy ring 90 (AVR and MVR) 40 (AVR and MVR) Very high Bicarbon Sorin Biomedica Cardio, Milan, Italy Titanium alloy ring 80 (AVR and MVR) 20 (AVR and MVR) Very high Mechanical tilting disk Björk-Shiley Shiley, Irvine, Calif Cobalt-chrome alloy (AVR and MVR) 0 (AVR and MVR) Very low Medtronic Hall Medtronic, Minneapolis, Minn Titanium alloy ring 75 (AVR and MVR) 0 (AVR and MVR) Very high Omniscience Medical Inc, St Paul, Minn Titanium alloy ring 60 (AVR) 0 (AVR) Unknown Allcarbon Sorin Biomedica Cardio, Milan, Italy Cobalt-chrome alloy 60 (AVR and MVR) 0 (AVR and MVR) Very low Biologic Biocor stentless St Jude Medical, St Paul, Minn None NA NA Unknown Extended Biocor St Jude Medical, St Paul, Minn Stainless steel wire NA NA Unknown Bioflow pericardial Biomedical, Glasgow, Scotland Unknown NA NA Unknown Carpentier-Edwards Edwards Lifesciences, Irvine, Calif Elgiloy NA NA Very high bovine Carpentier-Edwards Perimount pericardial Edwards Lifesciences, Irvine, Calif Elgiloy NA NA Very high Hancock I Medtronic, Minneapolis, Minn Stellite band around the polypropylene stent Hancock II Medtronic, Minneapolis, Minn Haynes alloy rings in each stent post tip Ionescu-Shiley Shiley, Irvine, Calif Titanium frame covered with Dacron NA NA Unknown NA NA Unknown NA NA Unknown Freestyle Medtronic, Minneapolis, Minn None NA NA Very high Intact Medtronic, Minneapolis, Minn None NA NA Very high Mosaic Medtronic, Minneapolis, Minn Haynes alloy rings in each stent post tip; Haynes alloy band around the stent NA NA Very high Mitroflow Sorin Group Canada, Burnaby, Canada None NA NA Very high Note. Adapted, with permission, from reference 2. *AVR = aortic valve replacement, MVR = mitral valve replacement, NA = not applicable. 30 for mm valves, 25 for mm valves. 60 for valves manufactured before 1981, 70 for valves manufactured after 1981.

5 RG Volume 32 Number 7 Habets et al 1897 Patient Selection Patients with suspected PHV dysfunction present in the outpatient clinic, emergency department, or ward. Patients can present with widely varying symptoms, such as signs of heart failure (dyspnea, edema), fever, a new murmur, dizziness during exercise, angina pectoris, or nonspecific complaints (eg, palsy in a patient with stroke and a cardiac embolus). Important echocardiographic parameters are the mean and peak pressure gradients over the PHV, the area of the prosthetic orifice, and the pattern of regurgitation. A detailed description of echocardiographic assessment of PHVs is beyond the scope of this article. For the interested reader, Zoghbi et al (14) provide an excellent overview of PHV assessment with echocardiography. PHV obstruction manifests as an increased pressure gradient and decreased prosthetic orifice area (2,14). Fluoroscopy can demonstrate leaflet restriction in patients with mechanical PHV obstruction. Mechanical PHVs have a physiologic regurgitant jet that is necessary to close the valve. After routine evaluation with echocardiography and fluoroscopy, cardiologists and cardiothoracic surgeons may request additional CT evaluation to determine the exact cause of PHV dysfunction. CT evaluation can be requested in patients with inconclusive echocardiography results because of limited echocardiographic windows (eg, due to obesity or pulmonary emphysema) or acoustic shadowing. Several factors are important in determining whether a patient with a PHV is a suitable candidate for multidetector CT angiography. First, the usual contraindications to multidetector CT angiography (ie, contrast material allergy, renal failure, and pregnancy) apply. However, these contraindications are not absolute; CT can be reconsidered if it is likely that it will provide crucial information that cannot be obtained otherwise or is likely to change patient care significantly. Second, it is important to check which PHV type is implanted, as PHV composition influences the CT image quality. Table 1 presents the CT visibility of different types of PHVs. The image quality of most PHVs is good, but PHVs containing cobalt-chrome alloy rings (Björk-Shiley and Allcarbon tilting-disk PHVs) cause severe PHV-related artifacts that prevent diagnostic assessment. These cobaltchrome PHVs are not suitable for CT evaluation (11,12). Third, pacemaker leads may interfere with diagnostic assessment of PHVs and also hamper assessment of other cardiac structures, especially coronary arteries. However, in most patients with cardiac pacemakers, diagnostic assessment of PHVs is possible. Besides these practical issues, it is important to know the indications for CT assessment. In patients with suspected PHV obstruction and endocarditis, multidetector CT angiography can have additional diagnostic value by demonstrating the specific cause of PHV dysfunction and the exact extent of disease. In patients who primarily have regurgitation, multidetector CT angiography may have little additional value besides assessment of the location of the leak in selected patients because of the lack of functional information. However, in patients with suspected PHV endocarditis and regurgitation due to (suspected) mycotic aneurysms, CT definitely has additional value by depicting three-dimensional anatomy. Furthermore, multidetector CT angiography may depict the area of regurgitation, which can be valuable information for surgical planning. Image Acquisition In general, patients with PHV dysfunction are different from patients who undergo CT angiography for coronary assessment. The former often have impaired left or right ventricular function, arrhythmia, and altered thoracic anatomy (previous sternotomy, adhesions). For coronary CT angiography, prospectively triggered volume scanning is preferred to reduce radiation dose, and one diagnostic diastolic imaging phase is often enough for adequate coronary assessment. In patients with suspected PHV dysfunction, information on the anatomy of the valve and the periprosthetic region has to be obtained in both systolic and diastolic phases. Furthermore, dynamic information on the opening and closing of the valve leaflets is required, especially in cases of mechanical PHVs. Therefore, retrospectively ECG-gated image acquisition is preferred (2). Retrospectively ECG-gated acquisition is associated with a higher radiation dose than prospectively triggered scanning. However, the risk of repeat surgery to replace a dysfunctional PHV is high, and overall mortality after aortic PHV repeat surgery is 3.8% 15.3%, depending on the cause of PHV dysfunction (15,16). Patients with congenital valve abnormalities are a relatively young group. Especially in this group, dose reduction methods such as dose modulation, prospective triggering, and iterative reconstruction are evaluated to reduce radiation exposure (17,18). A 64-section or greater CT system is required for optimal imaging. Our 64- and 256-section multidetector CT protocol is based on retrospectively gated coronary CT angiography protocols (Table 2); imaging volume is planned on

6 1898 November-December 2012 radiographics.rsna.org Table 2 Multidetector CT Acquisition Parameters for Imaging of PHVs Nonenhanced CT Retrospectively ECG-gated CTA CT Acquisition Parameters 64-section 256-section 64-section 256-section Section thickness (mm) Increment (mm) Tube potential (kv) Tube current (mas) * 600 or 700 Collimation Pitch None None or 0.18 Rotation time (sec) or 0.33 Field of view (mm) Filter Cardiac B Cardiac B Cardiac B Cardiac B Matrix Reconstruction algorithm FBP FBP FBP FBP Reconstruction phases 75% 75% 10 equally spaced 10 equally spaced Note. CTA = CT angiography, FBP = filtered back projection. *500 mas for patient weight <65 kg, 600 mas for patient weight of kg, 700 mas for patient weight >80 kg. 600 mas for patient weight of kg, 700 mas for patient weight >80 kg. Pitch = 0.16 for heart rate >72 beats per minute; pitch = 0.18 for heart rate <72 beats per minute sec for heart rate >62 beats per minute, 0.33 sec for heart rate <62 beats per minute. the basis of a standard surview or scout image (80 kv, 20 mas). The PHV may be difficult to detect on surview or scout images. Previously obtained chest radiographs may help one identify the PHV by using its relationship with the sternal wires as a reference. For PHV imaging, it is important to evaluate the complete heart, including the ascending aorta. Nonenhanced imaging of the PHV can be added to help differentiate PTFE pledgets (suture material commonly used during PHV implantation) from paravalvular leakage and assess calcifications (Table 2). For contrast material enhanced imaging, we plan the acquisition from 2 cm above the carina (including the ascending aorta) to the bottom of the heart to achieve complete imaging of the heart. If desired, the scanning range can be reduced in the craniocaudal direction to reduce radiation exposure. In cardiac CT angiography, a low heart rate is preferable because it reduces motion-related artifacts, thereby improving image quality. Unfortunately, patients with PHV dysfunction may have contraindications to b-blockers (rhythm disorders in the postoperative phase or impaired left ventricular function). It is advisable to consult the cardiologist before b-blockers are administered. At our institution, 5 20 mg of metoprolol is administered intravenously with a target heart rate of 60 beats per minute in the absence of contraindications to b-blockers. When the referring clinician also requests diagnostic information on the coronary arteries, it is advisable to administer nitroglycerin to dilate the coronary arteries for optimal image quality. We use a triphasic contrast material administration protocol to achieve optimal contrast enhancement in the left ventricle and atrium. A locator is placed in the descending aorta; when the threshold of 100 HU is reached, image acquisition starts after an added postthreshold delay of 8 seconds. Administration of contrast material (iopromide, 300 mg/ml) is performed with a mean flow rate of ml/sec. Contrast agent volume is dependent on the patient s body weight, duration of image acquisition, and the added delay. The iodine flow rate varies between 1.6 (weight < 70 kg), 1.8 (weight = kg), and 2.0 (weight > 85 kg) g/sec. In the first phase, only contrast medium is injected. Second, a mixture of 30% contrast medium and 70% saline is administered, followed by a saline flush. These contrast material administration protocols are performed for left-sided PHV evaluation. Right-sided contrast-enhanced PHV

7 RG Volume 32 Number 7 Habets et al 1899 Figure 3. Imaging planes for PHV evaluation. CT images show a normal functioning Carbomedics bileaflet PHV in three perpendicular planes: in plane (a), parallel with the valve leaflets (b), and perpendicular to the valve leaflets (c). Figure 4. Evaluation of dynamic behavior of a PHV. CT images show closing (a) and opening (b) angles for a Carbomedics bileaflet PHV. (The manufacturer s reference closing and opening angles are 25 and 78, respectively.) A reference line parallel to the valve ring is used for angle measurement. evaluation is more complex because it is difficult to achieve good right-sided contrast enhancement and should be tailored to the individual patient. Image Reconstruction Raw data are reconstructed into 10 equally spaced datasets within the R-R interval of the cardiac cycle and sent to dedicated workstations. All reconstructed datasets are loaded simultaneously into the dedicated cardiac analysis software. The imaging planes are aligned parallel with and perpendicular to the valve leaflets as well as in plane with the valve in three perpendicular imaging planes (Fig 3). For dynamic evaluation, cine images in the plane perpendicular to the valve leaflets are recorded after appropriate alignment and windowing (Movies 1 and 2 [online]). For anatomic assessment, the best systolic and diastolic reconstruction phases are selected. From these phases, data batches in the same three perpendicular imaging planes are saved. Additional reconstruction in echocardiographic views and coronary multiplanar reconstruction can be performed as indicated. Finally, the reconstructed images are sent to the picture archiving and communication system (PACS) for archiving and assessed together with the standard axial images. Image Interpretation PHV assessment starts with evaluation of the cine images, which provide information on the dynamic behavior (opening and closing) of the PHV. For mechanical PHV leaflets, closing and opening angles can be measured and compared with PHV type and size-specific reference values (Table 1, Fig 4). After the dynamic assessment, anatomic

8 1900 November-December 2012 radiographics.rsna.org assessment in both systole and diastole is performed. The reconstructed image batches in three perpendicular directions are evaluated for abnormalities. Mitral PHV evaluation is not different from aortic PHV evaluation. However, CT evaluation of patients with aortic PHVs may have more complementary diagnostic value because acoustic shadowing may more often result in inconclusive TEE results in patients with aortic PHVs. In patients considered for repeat surgery, it is important for the radiologist to report additional relevant preoperative information. First, it is important to report on the presence of coronary artery disease and the patency of bypass grafts. In most patients, these features can be simultaneously assessed (19). Coronary artery assessment is especially important in patients with suspected PHV endocarditis. In these patients, vegetations may embolize into the coronary arteries or aorta due to catheter manipulation during conventional coronary angiography, which is therefore best avoided. Furthermore, it is important to inform the cardiologist and cardiothoracic surgeon about the dimensions of the aorta to allow an appropriate decision on surgery of the aortic root or arch. Moreover, it is important to inform the cardiothoracic surgeon about the distance between the sternum and right ventricle and whether any bypass grafts traverse the retrosternal space. Relevant extracardiac findings need to be assessed and reported as well. Reporting of Imaging Findings Essential for excellent diagnostic care in patients with PHV dysfunction is well-functioning multidisciplinary cooperation between the departments of cardiology, cardiothoracic surgery, and radiology. Diagnostic PHV evaluation is a multifactorial process that includes the clinical history, physical examination, and imaging evaluation (TTE, TEE, fluoroscopy, and multidetector CT). To achieve the optimal complementary value of multidetector CT angiography, it is important for the radiologist to be informed about the details of PHV implantation (surgical report) and previous clinical and imaging findings (postoperative TTE images) and to have a solid understanding of the procedures used by the surgeon. An appropriate CT request including relevant clinical and imaging information increases the value CT can offer. It is best to discuss the case directly with the cardiologist and cardiothoracic surgeon before the imaging evaluation. A proposed standardized report is presented in Figure 5. In addition to use of the standardized report, we believe it is important for imaging findings to be discussed in a multidisciplinary meeting with the Figure 5. Proposed standardized report for CT angiography of PHVs. LVOT = left ventricular outflow tract. cardiologists and cardiothoracic surgeons for appropriate diagnosis and treatment decisions. Imaging Characteristics of Normal PHVs Previous reports demonstrated that most commonly implanted PHVs can be well visualized with multidetector CT angiography (11,12,20). The CT image quality of PHVs largely depends on their composition (11 13,21). PHVs that contain nickel or titanium alloy rings are well visualized with multidetector CT (Table 1). PHVs containing titanium have the best CT image quality (Table 1). The CT characteristics of two commonly implanted normal bileaflet PHVs the Carbomedics and St Jude Medical valves are shown in Figures 6 and 7, respectively. Dynamic assessment of valve

9 RG Volume 32 Number 7 Habets et al 1901 Figure 6. Normal CT appearance of a commonly implanted PHV. In-plane (a, d), parallel (b, e), and perpendicular (c, f) CT images show a Carbomedics bileaflet PHV in the aortic position in systole (a c) and diastole (d f). Figure 7. Normal CT appearance of a commonly implanted PHV. In-plane (a, d), parallel (b, e), and perpendicular (c, f) CT images show a St Jude Medical bileaflet PHV in the mitral position in diastole (a c) and systole (d f).

10 1902 November-December 2012 radiographics.rsna.org Figure 8. Normal CT appearance of a PHV composed of titanium. In-plane (a, d), parallel (b, e), and perpendicular (c, f) CT images show a Medtronic Hall tilting-disk PHV in the mitral position in diastole (a c) and systole (d f). leaflets is possible by using cine images (Movies 1 and 2 [online]). A Medtronic Hall tilting-disk PHV, which is composed of titanium, is shown in Figure 8. The Björk-Shiley and Allcarbon tiltingdisk PHVs and Duromedics bileaflet PHV contain a cobalt-chrome alloy that produces severe PHV artifacts, thus preventing PHV assessment (Fig 9). Most biologic PHVs are well visualized with multidetector CT (11,22) (Fig 10). The valve leaflets may have moderate image quality (11). Chenot et al (22) demonstrated that use of a higher tube voltage (140 kv) for reduction of blooming metal artifacts may improve leaflet visualization of biologic PHVs. Imaging Characteristics of PHVs Used in TAVI Recently, TAVI was introduced as an alternative to open heart surgery in patients with diseased native aortic valves. Valve delivery for TAVI can be performed via the groin (access through the femoral artery) or left ventricular apex (access through a minimally invasive thoracotomy). Two valves are available for TAVI procedures: CoreValve (Medtronic) and Sapien (Edwards Lifesciences). Both consist of a stent-mounted biologic valve. At present, multidetector CT is a valuable imaging modality in preoperative work-up before TAVI to (a) evaluate the potential access routes (vessel diameters, location of calcification and stenosis) and (b) determine the aortic root and

11 RG Volume 32 Number 7 Habets et al 1903 Figure 9. Normal CT appearance of a PHV composed of a cobalt-chrome alloy. In-plane (a, d), perpendicular (b, e), and parallel (c, f) CT images show a Björk-Shiley tilting-disk PHV in the aortic position in systole (a c) and diastole (d f). Note the severe PHV-related artifacts that prevent diagnostic assessment. Figure 10. Normal CT appearance of a biologic PHV. In-plane (a), perpendicular (b), and parallel (c) CT images show a Carpentier-Edwards Perimount PHV in the aortic position in diastole.

12 1904 November-December 2012 radiographics.rsna.org Figure 11. Normal CT appearances of TAVI valves. In-plane (a, d), parallel (b, e), and perpendicular (c, f) CT images show the Sapien (a c) and CoreValve (d f) transcatheter aortic valves in diastole. annular dimensions needed for prosthesis sizing. Little is known about the value of multidetector CT in evaluation of patients after TAVI. Postoperative echocardiographic evaluation may be hampered by acoustic shadowing due to the metal contents of the stent-mounted valves. Multidetector CT allows adequate visualization of both types of TAVI valves (23). Figure 11 illustrates the normal multidetector CT appearance of the Sapien valve and CoreValve. Conclusions PHV assessment with CT angiography is a promising cardiac CT application that is of complementary diagnostic value to the clinical routine imaging techniques echocardiography and fluoroscopy and can provide additional relevant anatomic information that can have an impact on patient care. As part of a multidisciplinary team that also includes cardiologists and cardiothoracic surgeons, the radiologist can contribute to the complex diagnostic process in cases of suspected PHV dysfunction. Acknowledgments. We thank Ingrid G. J. Janssen for the design of the illustration in Figure 1 and K. A. van Rijnbach and J. H. de Groot for their help with the final version of the figures and supplemental movies. We thank the members of the research group on PHV imaging, including members of the Departments of Cardiology and Cardiothoracic Surgery of University Medical Center Utrecht and Academic Medical Center Amsterdam, for their help in creating the manuscript. References 1. Yacoub MH, Takkenberg JJ. Will heart valve tissue engineering change the world? Nat Clin Pract Cardiovasc Med 2005;2(2): Habets J, Budde RP, Symersky P, et al. Diagnostic evaluation of left-sided prosthetic heart valve dysfunction. Nat Rev Cardiol 2011;8(8):

13 RG Volume 32 Number 7 Habets et al Vahanian A, Baumgartner H, Bax J, et al. Guidelines on the management of valvular heart disease: the Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology. Eur Heart J 2007;28(2): Bonow RO, Carabello BA, Chatterjee K, et al focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to revise the 1998 guidelines for the management of patients with valvular heart disease). Endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. J Am Coll Cardiol 2008;52(13):e1 e Akins CW, Miller DC, Turina MI, et al. Guidelines for reporting mortality and morbidity after cardiac valve interventions. 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Prosthetic heart valve assessment with multidetector-row CT: imaging characteristics of 91 valves in 83 patients. Eur Radiol 2011;21(7): Konen E, Goitein O, Feinberg MS, et al. The role of ECG-gated MDCT in the evaluation of aortic and mitral mechanical valves: initial experience. AJR Am J Roentgenol 2008;191(1): Symersky P, Budde RP, Prokop M, de Mol BA. Multidetector-row computed tomography imaging characteristics of mechanical prosthetic valves. J Heart Valve Dis 2011;20(2): Zoghbi WA, Chambers JB, Dumesnil JG, et al. Recommendations for evaluation of prosthetic valves with echocardiography and doppler ultrasound: a report from the American Society of Echocardiography s Guidelines and Standards Committee and the Task Force on Prosthetic Valves, developed in conjunction with the American College of Cardiology Cardiovascular Imaging Committee, Cardiac Imaging Committee of the American Heart Association, the European Association of Echocardiography, a registered branch of the European Society of Cardiology, the Japanese Society of Echocardiography and the Canadian Society of Echocardiography, endorsed by the American College of Cardiology Foundation, American Heart Association, European Association of Echocardiography, a registered branch of the European Society of Cardiology, the Japanese Society of Echocardiography, and Canadian Society of Echocardiography. J Am Soc Echocardiogr 2009;22(9): Jaussaud N, Gariboldi V, Giorgi R, et al. Risk of reoperation for aortic bioprosthesis dysfunction. J Heart Valve Dis 2009;18(3): Leontyev S, Borger MA, Modi P, et al. Redo aortic valve surgery: influence of prosthetic valve endocarditis on outcomes. J Thorac Cardiovasc Surg 2011;142(1): Habets J, Symersky P, de Mol BA, Mali WP, Leiner T, Budde RP. A novel iterative reconstruction algorithm allows reduced dose multidetector-row CT imaging of mechanical prosthetic heart valves. Int J Cardiovasc Imaging 2011 Oct 15. [Epub ahead of print]. 18. Symersky P, Habets J, Westers P, de Mol BA, Prokop M, Budde RP. Prospective ECG triggering reduces prosthetic heart valve-induced artefacts compared with retrospective ECG gating on 256-slice CT. Eur Radiol 2012;22(6): Habets J, van den Brink RB, Uijlings R, et al. Coronary artery assessment by multidetector computed tomography in patients with prosthetic heart valves. Eur Radiol 2012;22(6): LaBounty TM, Agarwal PP, Chughtai A, Bach DS, Wizauer E, Kazerooni EA. Evaluation of mechanical heart valve size and function with ECG-gated 64-MDCT. AJR Am J Roentgenol 2009;193(5): W389 W Symersky P, Budde RP, Westers P, de Mol BA, Prokop M. Multidetector CT imaging of mechanical prosthetic heart valves: quantification of artifacts with a pulsatile in-vitro model. Eur Radiol 2011;21 (10): Chenot F, Montant P, Goffinet C, et al. Evaluation of anatomic valve opening and leaflet morphology in aortic valve bioprosthesis by using multidetector CT: comparison with transthoracic echocardiography. Radiology 2010;255(2): de Heer LM, Kluin J, Stella PR, et al. Multimodality imaging throughout transcatheter aortic valve implantation. Future Cardiol 2012;8(3): This journal-based CME activity has been approved for AMA PRA Category 1 Credit TM. See

14 Teaching Points November-December Issue 2012 Multidetector CT Angiography in Evaluation of Prosthetic Heart Valve Dysfunction Jesse Habets, MD, PhD Willem P. T. M. Mali, MD, PhD Ricardo P. J. Budde, MD, PhD RadioGraphics 2012; 32: Published online /rg Content Codes: Page 1894 ECG-gated or -triggered multidetector CT angiography can contribute additional diagnostic value to the routine clinical work-up in patients with suspected PHV dysfunction, especially patients with PHV obstruction or PHV endocarditis, by demonstrating the anatomic substrate and the extent of disease. Page 1897 In patients with suspected PHV dysfunction, information on the anatomy of the valve and the periprosthetic region has to be obtained in both systolic and diastolic phases. Furthermore, dynamic information on the opening and closing of the valve leaflets is required, especially in cases of mechanical PHVs. Therefore, retrospectively ECG-gated image acquisition is preferred. Page 1899 For dynamic evaluation, cine images in the plane perpendicular to the valve leaflets are recorded after appropriate alignment and windowing (Movies 1 and 2 [online]). For anatomic assessment, the best systolic and diastolic reconstruction phases are selected. From these phases, data batches in the same three perpendicular imaging planes are saved. Page 1900 Previous reports demonstrated that most commonly implanted PHVs can be well visualized with multidetector CT angiography (11,12,20). The CT image quality of PHVs largely depends on their composition (11 13,21). PHVs that contain nickel or titanium alloy rings are well visualized with multidetector CT (Table 1). PHVs containing titanium have the best CT image quality (Table 1). Page 1902 Most biologic PHVs are well visualized with multidetector CT (11,22) (Fig 10). The valve leaflets may have moderate image quality (11). Chenot et al (22) demonstrated that use of a higher tube voltage (140 kv) for reduction of blooming metal artifacts may improve leaflet visualization of biologic PHVs.