© 2014, Wiley Periodicals, Inc. DOI: 10.1111/echo.12854
Echocardiography
REVIEW ARTICLE
Role of Multimodality Imaging in Transcatheter Aortic Valve Replacement Rajesh Ramineni, M.D.,* Ahmed Almomani, M.B.B.S,† Arnav Kumar, M.D.,† and Masood Ahmad, M.D.* *Division of Cardiology, University of Texas Medical Branch, Galveston, Texas; and †Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas
The treatment of aortic stenosis (AS) has reached an exciting stage with the introduction of transcatheter aortic valve replacement (TAVR). It is the treatment of choice in patients with severe AS who are considered very high risk for surgical valve replacement. Multimodality imaging (MMI) plays a crucial role in TAVR patient selection, intra-procedure guidance, and follow-up. With the ever-increasing scope for TAVR, a better understanding of MMI is essential to improve outcomes and prevent complications. (Echocardiography 2015;32:677–698) Key words: transcatheter aortic valve replacement, multimodality imaging, aortic stenosis, echocardiography, multislice detector CT The management of aortic stenosis (AS), the most common stenotic valvular lesion in developed nations,1 has taken an important turn with the introduction of transcatheter aortic valve replacement (TAVR) by Cribier et al.2 TAVR has emerged as a less invasive alternative to surgery in the management of severe AS. This procedure is superior to standard medical therapy in the inoperable cohort due to prohibitive operative risk and the results are comparable to surgery in the high-risk (Society of Thoracic Surgeons [STS] risk score >8) group of patients.3–5 Two valves, Edwards SAPIEN and CoreValve, have been approved by the FDA and are now available for transcatheter implantation (Fig. 1). More than 10 additional valves, currently in use in Europe, are making their way into the arena, with a majority having received Conformit e Europeenne (CE) mark. Hence, the role of TAVR will continue to expand in the near future.6 Success in any procedure is directly linked to careful planning, selecting the right patients, meticulous implementation of clinical protocols, and close follow-up. Multimodality imaging (MMI) plays a crucial role in this process and in determining the success of the implant. There is no single perfect imaging modality which could serve the purpose of preprocedure planning, intra-procedure guidance, and postprocedure follow-up. Each imaging technology has its benefits Address for correspondence and reprint requests: Masood Ahmad, M.D., Division of Cardiology, Department of Internal Medicine, 301 University Blvd, University of Texas Medical Branch, Galveston, TX 77555. Fax: 4097729835; E-mail: [email protected]
and limitations. Incremental data can be obtained from all modalities. Therefore, a better understanding of these technologies is needed to improve outcome, prevent complications, reduce cost of the procedure, and develop less invasive imaging strategies. The applications of MMI can be broadly categorized, according to the timing of their usage, as preprocedural, intra-procedural, and postprocedural. Preprocedural Assessment: Multimodality imaging plays a significant role in the preprocedural assessment. These imaging tools assist in patient selection, optimal prosthesis, and the correct procedural approach. They also provide information that is useful in anticipating complications. Thereby, measures can be taken to prevent or manage them (Table I). Table II summarizes valve specific parameters needed to plan a TAVR. Severity of Aortic Stenosis: The severity of AS is best assessed by transthoracic echocardiography (TTE), and is the imaging modality that marks the beginning of patient evaluation for TAVR. The Doppler signals are well aligned in the apical five-chamber and threechamber views of TTE, and the highest velocities are accurately captured to assess the transvalvular pressure gradient (Fig. 2). These measurements can also be obtained from the deep transgastric view by transesophageal echocardiography (TEE) should TTE be limited due to 677
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Figure 1. A. The Edwards SAPIEN XT valve (Edwards Lifesciences Corporation, Irvine, CA, USA), B. approximate placement of this device in the aortic root, and C. A corresponding cine aortogram. D. The Medtronic CoreValve (Medtronic CV Luxembourg S.a.r.l., Minneapolis, MN, USA), E. approximate placement of this device in the aortic root, and F. A corresponding cine aortogram. Reproduced with permission from van der Boon et al.88
TABLE I Clinical and Imaging Parameters Preprocedural Assessment Severity of AS Associated cardiac conditions which determine outcome (AI, MR, HCM) Overall assessment of patient’s tolerability of procedure (EF, LV size, WMA) Access site determination Annular assessment Aortic root angulation Height of coronary ostia Degree and location of calcification of the valve Procedure planning AS = aortic stenosis; AI = aortic regurgitation; MR = mitral regurgitation; HCM = hypertrophic cardiomyopathy; EF = ejection fraction; LV = left ventricle; WMA = wall-motion abnormality.
window constraints.7 Severe AS is defined by an aortic valve (AV) area of ≤1 cm2 (34 (annulus 18–20)
Dm = diameter; Max = maximum; Min = minimum.
decreased despite normal LV ejection fraction. High blood pressure can markedly decrease (up to 40%) the peak-to-peak gradient, which is one of the main measures of AS severity used during cardiac catheterization.12 In this population the LV faces a double afterload: a valvular load, due to the AS, and an arterial load, as a consequence of reduced arterial compliance.13 The LV of patients with moderate AS and concomitant hypertension may face a global hemodynamic load equivalent, or even higher, than patients with severe AS but no hypertension. These patients may develop myocardial dysfunction and symptoms secondary to a combination of moderate AS and some degree of hypertension. The valvuloarterial impedance (Zva) is an index used in assessing the global LV hemodynamic load (i.e. total load) that can be measured by Doppler echocardiography and is associated with LV myocardial dysfunction and worse outcomes. The Zva is defined as the ratio of the estimated LV systolic pressure (i.e., the sum of systolic arterial pressure [SAP] and mean pressure gradient [MPG]) to the stroke volume indexed (SVI) for body surface area (BSA): Zva = (SAP + MPG)/SVI. This index may be useful in evaluating patients with symptomatic AS and concomitant hypertension, especially when planning therapy.14,15 Energy loss index (ELI) is a new and promising index for measuring the severity of AS in patients with a small aorta. It is calculated by the following formula: ELI = [EOA 9 Aa (AA EOA)]/BSA, where EOA = estimated orifice area and Aa = aortic area at the sinotubular junction. The ELI accounts for ascending aortic size with 3+ by LV angiography, was a contraindication in the trials.3,5 Balloon valvuloplasty can worsen any degree of underlying AI. There-
Figure 3. Anatomy of the aortic root. The aortic root with the aortic valve, which is suspended in a crown-like fashion within the root, contains 3 circular rings A. the sinotubular junction, the “surgical” annulus (anatomic ventriculo-arterial junction), and the virtual aortic annulus, which is formed by joining the nadir of each aortic valvular cusp B. VA = ventriculo-arterial junction. Reproduced with permission from Sinning et al.67
fore, in this subgroup of patients, the valve needs to be implanted within a short time frame following valvuloplasty to prevent potential adverse outcomes of acute severe AI. Due to its anatomical relationship and close proximity to the location of the TAVR site, mitral valve structure and function can be significantly impacted during or post TAVR. It has been noted that baseline mitral regurgitation (MR) greater than mild is associated with higher mortality after CoreValve implantation. Moreover, the presence and severity of underlying conditions such as mitral stenosis and regurgitation could be altered, not only due to the reduction in LV afterload, but from a direct impact of the implanted valve prosthesis. Studies have shown that 35– 54% of patients with moderate to severe MR have shown improvement in the severity of MR post TAVR, but this improvement does not independently predict mortality.24,25 A significant improvement in MR was noted in patients with functional MR without severe pulmonary hypertension or atrial fibrillation.25 A small number (6– 8%) of patients did have worsening of MR, the majority of which were progression from none to trivial or trivial to mild. Improvement in MR is generally due to a decrease in valvulo arterial impedance post TAVR.26,27 However, in patients with tethered mitral leaflets, commonly seen in a dilated LV and functional MR, improvement in tethering was noted to play a role in the improvement of MR.27 The CoreValve system, due to its longer intraventricular portion, if implanted below the intended annular plane, has been suggested to impinge on the anterior mitral leaflet causing greater MR. Improvement occurred following repositioning the valve intra-procedurally.23,28 Moreover, severe calcification of the anterior mitral leaflet is reported to be associated with development of mild to moderate mitral stenosis post TAVR.28 Hence, a detailed evaluation of transmitral gradient, leaflet mobility, and calcification of the anterior leaflet is important as part of preprocedural evaluation. Severe MR was a contraindication in the TAVR trials.3,5 In most cases, MR improves due to the decrease in annular size from compression of the implanted AV. The presence of LV thrombus, significant LVOT obstruction by septal hypertrophy, or hypertrophic cardiomyopathy (HCM) represents other contraindications for the TAVR procedure.3,5 The presence of asymmetry with 681
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Figure 4. Biplane echocardiographic imaging is used to identify the sagittal imaging plane that bisects the largest dimension of the aortic annulus. A, B. Biplane transthoracic imaging shows the sagittal (A) and corresponding transverse (B) plane. The blue line shows the appropriate annular measurement in the on-axis sagittal plane. C, D. Biplane transesophageal imaging shows the sagittal (C) and corresponding transverse (D) plane. Blue line in panel C shows the appropriate annular measurement in the onaxis sagittal plane. Ao = aorta; AV = aortic valve; LVOT = left ventricle outflow tract.
thickening of the septum close to the AV annulus may create difficulty in valve implantation. Occasionally, ventricular displacement of the prosthesis may occur.29,30 HCM is also associated with diastolic dysfunction; prolonged pacing during the procedure may result in elevated LV filling pressure leading to pulmonary edema.31,32 682
Assessment of left ventricular ejection fraction (LVEF) is an important step in risk assessment prior to TAVR. A low EF may predict less tolerance to fast pacing for longer periods during the procedure. This evaluation can be carried out with TTE and CMR. Assessment of baseline wall-motion abnormalities (WMA) is essential to
Multimodality Imaging in TAVR
Figure 5. Spatial reconstruction of the aortic annulus with A. the “Turnaround Rule” Scheme and B–D, computed tomographic images. The transverse plane is turned clockwise around its own axis to align one at a time the nadirs of the aortic valve leaflets with the transverse plane in 3 steps (1–3). The distances to the coronary ostia can be measured in the longitudinal axis at a right angle to the hinge point plane (B, C, red arrows). LCC = left coronary cusp; NCC = noncoronary cusp; RCC = right coronary cusp. Reproduced with permission from Kasel et al.43
accurately detect acute coronary ostial occlusions due to the implant causing new WMA. Evaluations of LV size and SVI are important because a smaller SVI, irrespective of LVEF and PG, is associated with poor outcomes post TAVR when compared with patients with normal SVI.33
Figure 6. Measurement of anterior-to-posterior annular diameter in the longitudinal transcaval intracardiac echocardiographic view. Ao = aorta; LV = left ventricle. Reproduced with permission from Bartel et al.61
Access Site Determination: The vascular access site is a major source of complications with rates ranging from 5% to 23.3%.34 Selection of the access site is based on careful preprocedural screening and should be individualized for each patient. Currently, the majority of TAVR procedures are being performed through femoral arterial access. Other options available include transapical, axillary artery, and transaortic approach. However, these routes are reserved for cases where femoral access is not suitable. Assessment of vasculature through direct angiography is limited to evaluation of luminal size. Unlike direct angiography, multislice detector computed tomography (MDCT) can accurately assess complex atheroma, calcification, dissections, and vessel tortuosity, especially in the thoraco-abdominal aorta, femoral, and iliac regions.35 The presence of 683
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Figure 7. Three-dimensional reconstruction of the aortic annulus and aortic valve using three-dimensional dataset from cardiac magnetic resonance (CMR) with MPR (multiplanar reconstruction/reformatting) This dataset was obtained without gadolinium and with the free-breathing (nonenhanced echocardiogram-gated three-dimensional steady-state free-precession magnetic resonance angiography). RCA = right coronary artery. Reproduced with permission from Cavalcante and Schoenhagen.89
peripheral vascular disease significantly increases the risk of complications.30,35 A greater than 90° curvature in the vasculature is generally associated with difficulties in access and advancement of the valve system.36,37 In addition, accurate assessment of the luminal diameter and vessel characteristics at site of sheath insertion are necessary. Currently the Edwards SAPIEN system is 22–24 Fr in size, requiring a 7–8-mm inner luminal vessel diameter to accommodate it. In comparison, CoreValve is a 18 Fr system, requiring a 6-mm luminal diameter. It is known that, when the sheath stretches the artery >1.05 times its diameter, mortality, and bleeding outcomes increase significantly.38 Moreover, calcification extending more than 180° in the vessel results in poor ability of the vessel to accommodate larger sheaths.38 If both iliac arteries are not suitable for access, based on MDCT, then an axillary artery or transapical approach might be considered.36,39 Clearly, adequate assessment of vasculature helps 684
to determine the ideal route in advance of the procedure. With the newer generation smaller profile valves, a reduction in sheath size is expected, resulting in systems being more accommodative in smaller vessels. Edwards XT will use 18 Fr and 19 Fr sheaths. Annular Assessment: Evaluation of the AV annulus anatomy is extremely important for a successful TAVR outcome. The aortic prosthetic size is dictated by the AV annular diameter, making this measurement a critical one for procedural success. Any errors at this level could result in serious complications. One of the main utilities of MMI is accurate determination of the annular dimensions. True annulus/surgical annulus is measured at the LVaorta junction. However, for TAVR purposes, the annulus is defined by a plane which transects the base of all three cusps of the AV (Fig. 3). This is the narrowest portion in the AV and the
Multimodality Imaging in TAVR
Figure 8. Localization of the LM coronary artery by multidetector computed tomography and 3DTEE. A. Multidetector computed tomography imaging used to acquire the plane of the left main (LM) coronary artery, with yellow arrow indicating the distance from the hinge point of the left coronary cusp to the LM, and red arrow indicating the length of the left coronary cusp. B. Multiplanar reconstruction of a three-dimensional (3D) transesophageal echocardiography (TEE) volume set in the transverse plane. The blue arrow shows the plane of the LM coronary artery. C. Multiplanar reconstruction of a 3DTEE volume set showing the plane of the LM ostium and coronary artery. This plane is used to measure the length of the left coronary cusp (red arrow) and the distance from the hinge point of that cusp to the LM coronary ostium (yellow arrow) in systole. Ao = aorta; LV = left ventricle. Reproduced with permission from Bloomfield et al.37
dimensions obtained at this level determine the size of the device. This measurement can be obtained in the parasternal long-axis view using TTE or mid-esophageal reverse long-axis view at 120° in TEE, from the base of the right coronary cusp to the base of the commissure between left and noncoronary cusps in systole (Fig. 4).23 TTE may slightly underestimate aortic annular size when compared with TEE.40 The aortic annulus is not exactly round but has an oval shape with long and short diameters. Hence, it is recommended to obtain the widest dimensions along the long diameter and in a plane, which transects the base of all three cusps. Even TEE is known to underestimate the true annulus diameter when compared with the cylindrical sizers used in surgery, suggesting the diffi-
culty in identifying the angle with the widest diameter.41 This problem can be overcome by using biplane TEE acquisitions (Fig. 4), multiplanar analysis of 3DTEE, or MDCT,23,40 which allows the assessment of both diameters, the circumference, and area. Three-dimensional TEE planimetry of the annulus has been shown to improve the prosthesis size selection and to predict significant postprocedural AI.42 MDCT plays a significant role in accurately obtaining these measurements because the coronal, sagittal, and transverse imaging planes can be adjusted in 3 dimensions using the turnaround rule. A cross section can then be obtained at the right level to get precise dimensions (Fig. 5).43 With semiautomated quantification, analysis time can be significantly reduced, resulting in a better
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Figure 9. Coronary CT angiogram (CTA) of left ventricular outflow track (LVOT) aortic root angulation (ARA). Measurement of LVOT-ARA is performed using a coronal oblique projection and is defined as the angle between the axis of the first portion of the ascending aorta corresponding to the upper part of the bioprosthesis, and the LVOT axis corresponding the distal portion or landing zone of the prosthesis. This measurement is critical for determining whether the prosthesis will properly sit within the aorta. Patients with an LVOT-ARA >90°are not candidates for TAVI. Courtesy UTMB Department of Radiology.
inter-observer agreement. These advancements can result in significant improvement in the workflow and standardization of the annular measurements in evaluation for TAVR.44 Renal dysfunction places a major limitation on the use of MDCT. Intracardiac echocardiography (ICE) has good correlation with MDCT in obtaining dimensions at the aortic annulus and the sinus of Valsalva, and can be a valuable tool in this group of patients (Fig. 6, movie clip S1).45 In a study by Jabbour et al.22 CMR and cardiac CT measurements of the aortic annulus and the aorta showed close agreement in TAVR
candidates, making CMR a great option in patients with renal dysfunction, as the use of gadolinium-based contrast is not required (Fig. 7). When compared with CT, the use of 3DTEE with post processing (Q-Lab, Philips Healthcare Best, The Netherlands) is reported to have moderate correlation in the measurement of dimensions, with slightly smaller overall measurements including the eccentricity index (1-minimum diameter/maximum diameter).46 Moreover, 3DTEE has comparable sensitivity and specificity to CT in predicting paravalvular regurgitation of moderate or greater intensity, which is superior to 2DTEE, based on the predetermined cutoffs.47 Hence, in patients with limitations for use of contrast, 3DTEE might be a good alternative (Fig. 8). Aortic root angulation is another critical parameter for TAVR success, playing a role in the ability of the deployed valve to sit in the right location. It is obtained in the oblique coronal plane by MDCT and defined as the angle between the axes of the LVOT and the proximal portion of the ascending aorta (Fig. 9).48 An angle greater than 90°is a contraindication for TAVR. A smaller angle facilitates correct positioning of the valve. Height of the Coronary Ostia: It is important to measure the height of the coronary ostia from the annulus for TAVR because the leaflets of the native valve approximate against the aortic wall. In some cases, the stent in which the valve is placed may impede the coronary ostial flow. Moreover, it can make future access of the ostia difficult especially if angiography is needed. This is noted to be more of a concern in balloon expandable valves.49 The recommended annulus to ostia length is >10–11 mm for the
Figure 10. Quantification and characterization of the calcium burden of each calcium nodule and the whole aortic valve with multidetector CT. For each nodule the volume and mass are quantified, and also its situation about the specific cusp and location within the valve (annulus, leaflet, or both) are determined. Aortic valve total calcium burden is obtained by adding the volume and mass of each calcium nodule. A global evaluation of the most calcified cusp and the eccentricity of calcification are finally performed. Mg Ca HA, milligrams of calcium-hydroxyapatite. Reproduced with permission from Azzalini et al.51
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TABLE III Imaging Parameters and Complications Intra-Procedural Assessment Annular size correlation Accuracy of device positioning Immediate device complications Paravalvular leak Device embolization Periprocedural events Coronary ostial occlusion/embolization Worsening AI/MR Pericardial effusion/tamponade LV perforation Aortic dissection AI = aortic regurgitation; MR = mitral regurgitation.
Edwards SAPIEN valve depending on its size.3 For CoreValve, there is no recommended annulus to ostia length. However, it is important to be aware of this measurement and the
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length of the cusps to estimate the risk of coronary occlusion. The height to the right coronary annularostial distance can be measured in the TTE parasternal long-axis view or the reverse longaxis mid-esophageal view by TEE at 120–140° (Fig. 7). Visualization of the ostium of the left main coronary artery is more complex and requires biplane imaging, 3DTEE, or MDCT.30 The origin of the left main needs to be visualized in the short axis of the AV (mid esophageal 30°) and an image 90° to that plane crossing through the ostium of the left main artery needs to be obtained using the biplane technique in 3DTEE. This facilitates visualization of the distance between annulus and the ostium of the left main coronary artery. MDCT, due to its ability to obtain images in multiple planes, has an advantage in providing these measurements with greater ease (Fig. 6). In the case of renal dysfunction, CMR is valuable in determining the distance between the aortic annulus and coronary ostia.21
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Figure 11. 1. Suggested scheme and real-world application of the rule in normal aortic root anatomy. A. Schematic illustration of the “follow the right cusp” rule pointing to the proper alignment in the case of normal aortic root anatomy. B. Example of normal aortic root anatomy: images are provided without (upper images) and with (lower images) a schematic overlay. The white arrow indicates the pigtail catheter. Panels I through III show fluoroscopy-guided alignment of the aortic plane; panel IV shows the final result. CAU = caudal; CRA = cranial; L = left cusp; LAO = left anterior oblique; N = noncoronary cusp; R = right cusp; RAO = right anterior oblique. Reproduced with permission from Kasel et al.57 2. Suggested scheme and real-world application of the rule in horizontal aortic root anatomy. A. Schematic illustration of the “follow the right cusp” rule pointing to the proper alignment in the case of “horizontal” aortic root anatomy. B. Example of horizontal aortic root anatomy: images are provided without (upper images) and with (lower images) a schematic overlay. The white arrow indicates the pigtail catheter. Panels I through IV are as described in (1). Abbreviations as in (1). Reproduced with permission from Kasel et al.57
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mass of the largest calcium nodule, has been found to be an independent predictor of PVR. Other predictors are the number of calcified nodules, severe calcification in the landing area, and annulus area (Fig. 10).51 Certain parameters, including cover index of average annular diameter, obtained from the perimeter using 3DTEE (Q-Lab software) have been noted to have good sensitivity in predicting PVR with effective regurgitant orifice ≥29 mm2. Cover index is defined as 100 9 [(transcatheter heart valve diameter (THV) TEE annular diameter)/THV diameter]. A large aortic annulus size measured by MRI and CT has been reported to predict PVR. These studies suggest that a certain amount of oversizing may prevent PVR. Oversizing the valve by at least 1 mm relative to the mean annular diameter or by >10% of the annular area, as measured by MDCT, has reduced the risk of PVR.52,53 Figure 12. Transesophageal echocardiography biplane imaging to assess annular dimensions and predict aortic regurgitation A. Biplane imaging during balloon inflation. The green arrows identify the waist of the balloon at the level of the annulus. The blue arrow shows asymmetric balloon dilation at the commissure between the left and noncoronary cusps. The yellow arrows depict acoustic shadowing, which prevents adequate visualization of the peri-balloon region. B. The red arrows predict aortic regurgitation at the sites predicted during aortic balloon valvuloplasty. Reproduced with permission from Bloomfield et al.37
Degree and Location of Aortic Valve Calcification: Accurate assessment of calcification of the AV is important. The presence of some calcium is necessary for the valve to sit in place. However, large amounts of eccentric calcification result in inadequate apposition of the valve, leading to paravalvular leaks (PVR). In some cases, fusion of two leaflets with calcium can lead to a functional bicuspid valve, which may pose difficulty in adequate valve expansion. When the balloon is inflated, large calcium deposits noted at the tips of leaflets can potentially embolize into the coronaries, pushing the leaflets close to the coronary ostia.50 In cases with large calcification in the native valve, a smaller prosthesis than suggested by the annular dimension may be advisable. Fluoroscopy may also provide additional measurements at the time of definitive prosthesis sizing decision.30 Predicting Paravalvular Regurgitation: Multimodality imaging has a major role in predicting PVR. Multiple models have been proposed in this regard. Aortic valve calcium nodule score, computed as AV calcium mass x 688
Preprocedural Planning: All the information discussed in the preceding sections helps in: (1) planning the procedure; (2) determining the route of access; size and type of prosthesis; speed of the procedure; and level of pacing; and (3) anticipating problems such as inadequate expansion of valve or possibility of PVR; possibility of device migration; and development or worsening of MR leading to flash pulmonary edema. Being aware of these possibilities ahead of time allows for better planning and the ability to deal with these complications should they arise. Intra-Procedural Use: Intra-procedural use of MMI is an essential final step to correlate with the preprocedural assessment prior to the valve deployment. This step also serves as continuous vigilance in appropriate positioning and identification of early complications following balloon valvuloplasty and valve deployment (Table III). Primarily, intra-operative imaging is carried out by TEE and fluoroscopy. Some centers have used DynaCT or rotational angiography for implant selection and 3D model generation during rapid pacing with all the necessary cardiac landmarks.54,55 Real time CMR has been successfully tested in animal models, which may lead to its use in the near future especially with its benefits in reducing radiation and the lack of contrast usage. Annular Size Correlation: Prior to device placement, a final determination on the size of the device is made from assessing the waist diameter of the balloon used for
Multimodality Imaging in TAVR
Figure 13. Grading criteria for paravalvular AR. A. Schematic and illustrated representation of the short-axis view at the level of the aortic valve by echocardiography. B. Echocardiographic and schematic illustrations of the short-axis view of the aortic valve. Paravalvular aortic regurgitation (AR) can be graded according to the circumferential extent of the regurgitant jet. Paravalvular AR can be graded as mild, moderate, or severe on the basis of a circumferential extent of 20%, respectively. See Leon et al.90 RV = right ventricle. Image credit: CC Patrick J. Lynch and C. Carl Jaffe, Yale University, 2006. Reproduced with permission from Bloomfield et al.37
Figure 14. Treatment algorithm for PAR after TAVR. Treatment algorithm using a multimodal approach with the use of hemodynamic measurements and imaging modalities to quantify the severity of PAR during the TAVR procedure and to identify patients who will benefit from corrective measures. AR = aortic regurgitation; TEE = transesophageal echocardiography; TTE = transthoracic echocardiography. Reproduced with permission from Sinning et al.67
valvuloplasty. Any significant variations should be addressed at this time.41 This is an important step because reports suggest that balloon valvuloplasty leads to adjustment of prosthesis size in 25% of patients.56 This step can be performed under
fluoroscopic guidance but does come with the intrinsic limitation of obtaining images in a plane that is perfectly perpendicular to the native valve. Newer balloons with surrounding radiopaque circles will likely eliminate the uncertainty when imaging the balloon perpendicular to its position when fully inflated. “Follow the right cusp rule” proposed by Kasel et al.57 simplifies the steps to define the perpendicular annulus plane by fluoroscopy in both the normal and horizontally aligned heart (Fig. 9). This technique can be quickly done at the beginning of the procedure to improve the accuracy of valve placement. The steps of the procedure are (1) with a pigtail catheter in the right cusp, aortogram is carried out in left anterior oblique (LAO) 10° cranial (CRA) 10°; (2) the C-arm is then rotated to right anterior oblique (RAO) or LAO position to have right cusp in the center of aorta; and (3) the C-arm is then rotated in the cranial or caudal direction to bring the base of the right cusp at the annular level. These steps result in obtaining the perpendicular annulus plane. In a horizontal heart the sequence is similar. However, RAO and LAO rotations are intended to get the right cusp at the annular level, and cranial and caudal motion to center the right cusp (Fig. 11).57 TEE can be used to guide positioning of the balloon relative to the AV. It is especially useful when the valve is not very calcified and, 689
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Figure 15. Origin and mechanism of paravalvular aortic regurgitation (PAR). A. Transesophageal echocardiography (TEE) longaxis view of Edwards SAPIEN 23-mm prosthesis with both transvalvular AR and PAR (movie clip S2). B. PAR after deployment of an Edwards SAPIEN XT 26-mm prosthesis because of malapposition with the left annulus. The device was not coaxial to the root (movie clip S3). C. TEE short-axis view of underexpanded oval-shaped waist of a Medtronic CoreValve 29-mm prosthesis. D. TEE long-axis view of an Edwards SAPIEN XT 26-mm prosthesis with diameters of 24–26 mm indicating reasonable expansion in the presence of PAR. E. Color three-dimensional TEE of malposition PAR after low implantation of a Medtronic CoreValve prosthesis. The PAR jet passes from within the aortic portion of the stent frame above the tissue skirt (“supra-skirt” PAR) into the paravalvular space and LVOT (movie clip S4). F. TEE of malposition PAR after the high implantation of a Medtronic CoreValve 29-mm prosthesis. The posterior PAR jet passes from the aortic sinus below the tissue skirt (“infra-skirt” PAR) into the LVOT where the irregular inflow edge rises above the native annulus (movie clip S5). AR = aortic regurgitation. Reproduced with permission from Sinning et al.67
consequently, difficult to image on fluoroscopy. Biplane imaging using TEE during balloon inflation is also useful to identify areas of poor expansion. These areas could be the sites of poor apposition of the valve due to calcification and thereby predispose to PVR (Fig. 12).37 TEE may be used to (1) confirm a stable position during inflation and (2) monitor the behavior of the calcified aortic cusps during inflation as they are pushed back into the sinuses and toward the coronary ostia.23 DynaCT is useful during TAVR: this modality can facilitate exact sizing of the aortic annulus and help to prevent obstruction of the coronary arteries.58 However, this approach often requires a large amount of contrast agent, especially in cases of poor calcification of the annulus or the 690
cusps, which may contribute to postoperative renal failure.59 Accuracy of Device Positioning: A combination of fluoroscopy and TEE is used for accurate positioning of the AV across the annulus during deployment. TEE provides continuous real time 3D visualization of the annulus, valve, and the balloon, thereby aiding device placement, prediction, and immediate detection of AI.37 Depth perspective in live 3D mode provides better visualization for positioning the prosthesis on the balloon relative to the native valve annulus and surrounding structures. It also facilitates appreciation of the guide wire path through the LV and around the mitral valve subvalvular apparatus.23 Higher or lower placement of the valve
Multimodality Imaging in TAVR
TABLE IV Evaluation of Complications Postprocedural Use Assessment of valve hemodynamics Valve area and gradients Patient prosthesis mismatch Monitoring for long-term complications Paravalvular leak Valve thrombosis Endocarditis Device migration Impact on mitral valve Ventricular perforation Effect on concomitant pathologies Systolic and diastolic function Chamber remodeling
may result in supra-skirt or infra-skirt PVR, respectively. In patients with limited native valve calcification or for valve-in-valve procedures where TAVR is used in the setting of another bioprosthesis, TEE may be the main modality used for guidance. The optimal position of the Edwards SAPIEN valve is 2–4 mm below the annular plane in the LVOT. The CoreValve extends 5–10 mm below
the annulus.23 Immediately following deployment, TEE is used to confirm satisfactory positioning and function of the prosthesis. The next generation devices will enable the operator to resheath the device if the position needs to be adjusted during the deployment, making the use of MMI indispensible during the procedure.6 Role of ICE during the TAVR Procedure: ICE has been shown to be effective in reducing contrast use for angiography, resulting in shorter hospital stay, reduced severity, and decreased probability rates of acute kidney injury.60 When compared to TEE, ICE uses less intensive sedation/anesthesia during the procedure, and may reduce the need for probe repositioning. In addition, this technique provides better coaxial Doppler measurements in the ascending aorta leading to superior assessment of intra-procedural pressure gradients (Fig. 11).61 However, true longaxis views of the AV, annulus, and outflow tract are difficult to obtain. Thus, annular and coronary height measurements are not as accurate as those obtained by preprocedure MDCT.45 Immediate Device Complications: The availability of imaging is crucial in monitoring and managing immediate device complications, including device embolization and PVR.
Figure 16. Schematic and examples of spectral Doppler flow acceleration in a SAPIEN transcatheter heart valve. A. Schematic presentation of echocardiographic pulse-wave (PW) Doppler patterns when the sample volume is placed prestent, instent but precusps, and continuous wave (CW) through the aortic valve. Due to flow acceleration, it is imperative that the subvalvular velocities used in either Doppler velocity index or effective orifice area be sampled proximal to the stent. B. The PW Doppler pattern of a sample volume placed before stent. White arrows show the extent of the transcatheter heart valve in the aortic root. Red arrow shows the level of the prosthetic aortic cusps. C. The PW Doppler pattern of sample volume placed within the stent but before cusps. D. The PW Doppler pattern of a sample volume placed at the level of the cusps. Reproduced with permission from Bloomfield et al.37
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Device Embolization: Valve placement at the right location is of pivotal importance in TAVR. Any slight misjudgment can lead to serious consequences, including device embolization toward the ventricle or aorta. If transcatheter repositioning is not feasible, surgical removal may be required. This potential complication can be detected by TEE or fluoroscopy during device deployment. Immediate recognition is critical, not only due to the consequences of the embolized device, but to urgently deal with the hemodynamic changes from AI created by balloon valvuloplasty done right before device deployment. Identification of the location of the embolized valve in the aorta is imperative to its capture, withdrawal, and deployment in the descending aorta.62 Paravalvular Leak: PVR, frequently with multiple jets, is commonly seen following TAVR,4 though trace to mild and with a benign stable course in the majority of patients.63 However, severe AI may occur due to incomplete expansion or incorrect device positioning, restricted cusp motion, or inappropriate prosthetic size.53 These complications can be readily identified both by fluoroscopy and TEE. Limitations to fluoroscopy include difficulty in grading the severity of regurgitation due to significant overlap between the grades and the necessary use of additional contrast. Grading PVR determines the next course of action. Moderate to severe PVR needs correction because it has an impact on patient mortality and morbidity.64 PVR is most suitably evaluated by TEE and is seen as a circumferential leak in the short-axis view. PVR is best detected in TEE at 0° in the deep transgastric view. Semiquantitative measurements such as vena contracta, jet width, and pressure half time cannot be used due to the eccentric nature of the jet.65 However, gradation can be easily performed as illustrated in Fig. 13.37 Hemodynamics offer great help in precisely assessing the grade and deciding for intervention. Sinning et al.66 described aortic regurgitation index (ARI), the ratio of the transvalvular gradient between diastolic blood pressure (RRdia) in the aorta and LVEDP, to systolic blood pressure (RRsys) in the aorta, obtained by the formula LVEDP)/RRsys] 9 100, the value of [(RRdia
which holds an inverse correlation to severity of regurgitation and prognosis. A flow diagram (Fig. 14) described by the same group serves as a good guiding tool in making decisions relevant to the intervention.67 PVR may result from poor apposition due to hindrance from calcium, inferior (ventricular) placement, supra-skirt PVR, or superior (aortic) placement, infra-skirt PVR. TEE can differentiate these three forms (Fig. 15, movie clips S2–S5). Poor apposition can be corrected in some cases with balloon post dilatation. If unsuccessful, an interventional closure with Amplatzer device can be performed.68 Supra-skirt PVR can be corrected by snaring the valve into a more aortic position.68 If this fails, a valve-in-valve implantation can be performed. Infra-skirt PVR is usually corrected by valve-in-valve implant.68,69 Rarely is a central jet of AI seen. This represents potential destruction of one of the leaflets or low diastolic pressure, leading to poor coaptation or leaflet malfunction from a design/structural flaw in the valve. The decision to correct this scenario follows the same guidelines as PVR based on the impact on hemodynamics. Periprocedural Events: Intra-procedural TEE plays a crucial role in early detection of important acute events. A new onset WMA following valvuloplasty or valve deployment suggests occlusion and/or embolization into a coronary artery. Although this complication may be fatal, successful management of ostial occlusions with percutaneous angioplasty or bypass surgery has been reported.70,71 Other possible explanations for acute hemodynamic instability during the procedure that can be identified by TEE are cardiac tamponade, secondary to wire perforation of the left or right ventricle, and severe AI.23 An evaluation by color flow and Doppler across the implanted and native valves will demonstrate aortic and mitral insufficiency following valvuloplasty and valve implantation. Worsened AI after valvuloplasty is a strong reason to proceed quickly with valve implantation, as the stiffer ventricles in patients with longstanding AS can precipitate flash pulmonary edema. Aortic dissection, a tear, or rupture of the aortic root may be observed during the procedure following
Figure 17. A. CT multiplanar reconstruction prior to TAVR. Arrows are pointing to aortic annular calcification extending into the outflow tract at the level of the perimembranous interventricular septum. B. CT multiplanar reconstruction after TAVR. Arrows are pointing to the VSD inferior to the lower border of the SAPIEN valve. The previously seen calcification is no longer present. C. CT multiplanar reconstruction after VSD closure. Arrows are pointing to the membranous VSD occluding device with the LV disk overlapping the lower edge of the SAPIEN valve. Ao = aorta; LA = left atrium; LV = left ventricle; MVR = mechanical mitral replacement; RA = right atrium; RV = right ventricle; S = SAPIEN valve; VSD = ventricular septal defect. Reproduced with permission from Levi et al.85
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Figure 18. A. Longitudinal transcaval/transatrial (A) and short-axis transatrial (B) standard intracardiac echocardiographic views for TAVR. AAo = ascending aorta; AC = AcuNav catheter; AVP = aortic valve prosthesis; DAo = descending aorta; IVC = inferior vena cava; LV = left ventricle; RA = right atrium; RV = right ventricle; SVC = superior vena cava. B. Longitudinal transcaval (A) and short-axis (B) intracardiac echocardiographic views of aortic valve prosthesis after deployment and at enddiastole. Ao = aorta; 1 = minimal paravalvular leak; RCA = right coronary artery. C. Intracardiac spectral Doppler analyses of the native aortic valve (A), after predilatation (B), and after deployment of a 23-mm-diameter Edwards SAPIEN transcatheter heart valve prosthesis (C) on the basis of highest signal quality reveal decline of pressure gradient (PG). D. Longitudinal intracardiac echocardiographic view demonstrates both coronary arteries branching off above the opened aortic valve prosthesis. Ao = aorta; LCA = left coronary artery; RCA = right coronary artery. Reproduced with permission from Bartel et al.61
balloon valvuloplasty or prosthesis deployment, especially in the presence of extensive annular calcification or prosthesis oversizing. Both complications can be identified and necessary early steps taken using intra-operative TEE.23,39 Postprocedural Use: Multimodality imaging has an indispensible role and multiple applications in the postprocedural period, both short- and long-term (Table IV). Assessment of Valve Hemodynamics: Assessment of the relative AVA and gradients at regular intervals is imperative in identifying valve related problems. A good understanding of the hemodynamics inside a stented valve is required for accurate assessment. The ventricular portion of the stent creates flow acceleration into the prosthetic valve (Fig. 16).72 Hence, a PW Doppler measurement in this zone to assess for LVOT TVI will result in a spuriously high number. Used in the continuity equation, this number would calculate a falsely high prosthetic valve area or a normal Doppler velocity index (DVI). Moreover, the stented portion of the LVOT could be extended by the stent itself to a greater dimension than the regular LVOT. Measurement of the diameter in this segment may lead to erroneous calculations. Hence, the PW velocity in the LVOT and LVOT diameter should always be measured proximal to the stent of the valve in the LVOT.73 This discrepancy in measurements is of greater consequence when consecutive measurements are made in different zones, inside the stent versus outside the stent, leading to concern about valve malfunction. An important concept in prosthetic valves is patient-prosthesis mismatch (P-PM). This is more of a concern in surgically implanted valves with incidence ranging from 20 to 70%.74 An EOA
Echocardiography
REVIEW ARTICLE
Role of Multimodality Imaging in Transcatheter Aortic Valve Replacement Rajesh Ramineni, M.D.,* Ahmed Almomani, M.B.B.S,† Arnav Kumar, M.D.,† and Masood Ahmad, M.D.* *Division of Cardiology, University of Texas Medical Branch, Galveston, Texas; and †Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas
The treatment of aortic stenosis (AS) has reached an exciting stage with the introduction of transcatheter aortic valve replacement (TAVR). It is the treatment of choice in patients with severe AS who are considered very high risk for surgical valve replacement. Multimodality imaging (MMI) plays a crucial role in TAVR patient selection, intra-procedure guidance, and follow-up. With the ever-increasing scope for TAVR, a better understanding of MMI is essential to improve outcomes and prevent complications. (Echocardiography 2015;32:677–698) Key words: transcatheter aortic valve replacement, multimodality imaging, aortic stenosis, echocardiography, multislice detector CT The management of aortic stenosis (AS), the most common stenotic valvular lesion in developed nations,1 has taken an important turn with the introduction of transcatheter aortic valve replacement (TAVR) by Cribier et al.2 TAVR has emerged as a less invasive alternative to surgery in the management of severe AS. This procedure is superior to standard medical therapy in the inoperable cohort due to prohibitive operative risk and the results are comparable to surgery in the high-risk (Society of Thoracic Surgeons [STS] risk score >8) group of patients.3–5 Two valves, Edwards SAPIEN and CoreValve, have been approved by the FDA and are now available for transcatheter implantation (Fig. 1). More than 10 additional valves, currently in use in Europe, are making their way into the arena, with a majority having received Conformit e Europeenne (CE) mark. Hence, the role of TAVR will continue to expand in the near future.6 Success in any procedure is directly linked to careful planning, selecting the right patients, meticulous implementation of clinical protocols, and close follow-up. Multimodality imaging (MMI) plays a crucial role in this process and in determining the success of the implant. There is no single perfect imaging modality which could serve the purpose of preprocedure planning, intra-procedure guidance, and postprocedure follow-up. Each imaging technology has its benefits Address for correspondence and reprint requests: Masood Ahmad, M.D., Division of Cardiology, Department of Internal Medicine, 301 University Blvd, University of Texas Medical Branch, Galveston, TX 77555. Fax: 4097729835; E-mail: [email protected]
and limitations. Incremental data can be obtained from all modalities. Therefore, a better understanding of these technologies is needed to improve outcome, prevent complications, reduce cost of the procedure, and develop less invasive imaging strategies. The applications of MMI can be broadly categorized, according to the timing of their usage, as preprocedural, intra-procedural, and postprocedural. Preprocedural Assessment: Multimodality imaging plays a significant role in the preprocedural assessment. These imaging tools assist in patient selection, optimal prosthesis, and the correct procedural approach. They also provide information that is useful in anticipating complications. Thereby, measures can be taken to prevent or manage them (Table I). Table II summarizes valve specific parameters needed to plan a TAVR. Severity of Aortic Stenosis: The severity of AS is best assessed by transthoracic echocardiography (TTE), and is the imaging modality that marks the beginning of patient evaluation for TAVR. The Doppler signals are well aligned in the apical five-chamber and threechamber views of TTE, and the highest velocities are accurately captured to assess the transvalvular pressure gradient (Fig. 2). These measurements can also be obtained from the deep transgastric view by transesophageal echocardiography (TEE) should TTE be limited due to 677
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Figure 1. A. The Edwards SAPIEN XT valve (Edwards Lifesciences Corporation, Irvine, CA, USA), B. approximate placement of this device in the aortic root, and C. A corresponding cine aortogram. D. The Medtronic CoreValve (Medtronic CV Luxembourg S.a.r.l., Minneapolis, MN, USA), E. approximate placement of this device in the aortic root, and F. A corresponding cine aortogram. Reproduced with permission from van der Boon et al.88
TABLE I Clinical and Imaging Parameters Preprocedural Assessment Severity of AS Associated cardiac conditions which determine outcome (AI, MR, HCM) Overall assessment of patient’s tolerability of procedure (EF, LV size, WMA) Access site determination Annular assessment Aortic root angulation Height of coronary ostia Degree and location of calcification of the valve Procedure planning AS = aortic stenosis; AI = aortic regurgitation; MR = mitral regurgitation; HCM = hypertrophic cardiomyopathy; EF = ejection fraction; LV = left ventricle; WMA = wall-motion abnormality.
window constraints.7 Severe AS is defined by an aortic valve (AV) area of ≤1 cm2 (34 (annulus 18–20)
Dm = diameter; Max = maximum; Min = minimum.
decreased despite normal LV ejection fraction. High blood pressure can markedly decrease (up to 40%) the peak-to-peak gradient, which is one of the main measures of AS severity used during cardiac catheterization.12 In this population the LV faces a double afterload: a valvular load, due to the AS, and an arterial load, as a consequence of reduced arterial compliance.13 The LV of patients with moderate AS and concomitant hypertension may face a global hemodynamic load equivalent, or even higher, than patients with severe AS but no hypertension. These patients may develop myocardial dysfunction and symptoms secondary to a combination of moderate AS and some degree of hypertension. The valvuloarterial impedance (Zva) is an index used in assessing the global LV hemodynamic load (i.e. total load) that can be measured by Doppler echocardiography and is associated with LV myocardial dysfunction and worse outcomes. The Zva is defined as the ratio of the estimated LV systolic pressure (i.e., the sum of systolic arterial pressure [SAP] and mean pressure gradient [MPG]) to the stroke volume indexed (SVI) for body surface area (BSA): Zva = (SAP + MPG)/SVI. This index may be useful in evaluating patients with symptomatic AS and concomitant hypertension, especially when planning therapy.14,15 Energy loss index (ELI) is a new and promising index for measuring the severity of AS in patients with a small aorta. It is calculated by the following formula: ELI = [EOA 9 Aa (AA EOA)]/BSA, where EOA = estimated orifice area and Aa = aortic area at the sinotubular junction. The ELI accounts for ascending aortic size with 3+ by LV angiography, was a contraindication in the trials.3,5 Balloon valvuloplasty can worsen any degree of underlying AI. There-
Figure 3. Anatomy of the aortic root. The aortic root with the aortic valve, which is suspended in a crown-like fashion within the root, contains 3 circular rings A. the sinotubular junction, the “surgical” annulus (anatomic ventriculo-arterial junction), and the virtual aortic annulus, which is formed by joining the nadir of each aortic valvular cusp B. VA = ventriculo-arterial junction. Reproduced with permission from Sinning et al.67
fore, in this subgroup of patients, the valve needs to be implanted within a short time frame following valvuloplasty to prevent potential adverse outcomes of acute severe AI. Due to its anatomical relationship and close proximity to the location of the TAVR site, mitral valve structure and function can be significantly impacted during or post TAVR. It has been noted that baseline mitral regurgitation (MR) greater than mild is associated with higher mortality after CoreValve implantation. Moreover, the presence and severity of underlying conditions such as mitral stenosis and regurgitation could be altered, not only due to the reduction in LV afterload, but from a direct impact of the implanted valve prosthesis. Studies have shown that 35– 54% of patients with moderate to severe MR have shown improvement in the severity of MR post TAVR, but this improvement does not independently predict mortality.24,25 A significant improvement in MR was noted in patients with functional MR without severe pulmonary hypertension or atrial fibrillation.25 A small number (6– 8%) of patients did have worsening of MR, the majority of which were progression from none to trivial or trivial to mild. Improvement in MR is generally due to a decrease in valvulo arterial impedance post TAVR.26,27 However, in patients with tethered mitral leaflets, commonly seen in a dilated LV and functional MR, improvement in tethering was noted to play a role in the improvement of MR.27 The CoreValve system, due to its longer intraventricular portion, if implanted below the intended annular plane, has been suggested to impinge on the anterior mitral leaflet causing greater MR. Improvement occurred following repositioning the valve intra-procedurally.23,28 Moreover, severe calcification of the anterior mitral leaflet is reported to be associated with development of mild to moderate mitral stenosis post TAVR.28 Hence, a detailed evaluation of transmitral gradient, leaflet mobility, and calcification of the anterior leaflet is important as part of preprocedural evaluation. Severe MR was a contraindication in the TAVR trials.3,5 In most cases, MR improves due to the decrease in annular size from compression of the implanted AV. The presence of LV thrombus, significant LVOT obstruction by septal hypertrophy, or hypertrophic cardiomyopathy (HCM) represents other contraindications for the TAVR procedure.3,5 The presence of asymmetry with 681
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Figure 4. Biplane echocardiographic imaging is used to identify the sagittal imaging plane that bisects the largest dimension of the aortic annulus. A, B. Biplane transthoracic imaging shows the sagittal (A) and corresponding transverse (B) plane. The blue line shows the appropriate annular measurement in the on-axis sagittal plane. C, D. Biplane transesophageal imaging shows the sagittal (C) and corresponding transverse (D) plane. Blue line in panel C shows the appropriate annular measurement in the onaxis sagittal plane. Ao = aorta; AV = aortic valve; LVOT = left ventricle outflow tract.
thickening of the septum close to the AV annulus may create difficulty in valve implantation. Occasionally, ventricular displacement of the prosthesis may occur.29,30 HCM is also associated with diastolic dysfunction; prolonged pacing during the procedure may result in elevated LV filling pressure leading to pulmonary edema.31,32 682
Assessment of left ventricular ejection fraction (LVEF) is an important step in risk assessment prior to TAVR. A low EF may predict less tolerance to fast pacing for longer periods during the procedure. This evaluation can be carried out with TTE and CMR. Assessment of baseline wall-motion abnormalities (WMA) is essential to
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Figure 5. Spatial reconstruction of the aortic annulus with A. the “Turnaround Rule” Scheme and B–D, computed tomographic images. The transverse plane is turned clockwise around its own axis to align one at a time the nadirs of the aortic valve leaflets with the transverse plane in 3 steps (1–3). The distances to the coronary ostia can be measured in the longitudinal axis at a right angle to the hinge point plane (B, C, red arrows). LCC = left coronary cusp; NCC = noncoronary cusp; RCC = right coronary cusp. Reproduced with permission from Kasel et al.43
accurately detect acute coronary ostial occlusions due to the implant causing new WMA. Evaluations of LV size and SVI are important because a smaller SVI, irrespective of LVEF and PG, is associated with poor outcomes post TAVR when compared with patients with normal SVI.33
Figure 6. Measurement of anterior-to-posterior annular diameter in the longitudinal transcaval intracardiac echocardiographic view. Ao = aorta; LV = left ventricle. Reproduced with permission from Bartel et al.61
Access Site Determination: The vascular access site is a major source of complications with rates ranging from 5% to 23.3%.34 Selection of the access site is based on careful preprocedural screening and should be individualized for each patient. Currently, the majority of TAVR procedures are being performed through femoral arterial access. Other options available include transapical, axillary artery, and transaortic approach. However, these routes are reserved for cases where femoral access is not suitable. Assessment of vasculature through direct angiography is limited to evaluation of luminal size. Unlike direct angiography, multislice detector computed tomography (MDCT) can accurately assess complex atheroma, calcification, dissections, and vessel tortuosity, especially in the thoraco-abdominal aorta, femoral, and iliac regions.35 The presence of 683
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Figure 7. Three-dimensional reconstruction of the aortic annulus and aortic valve using three-dimensional dataset from cardiac magnetic resonance (CMR) with MPR (multiplanar reconstruction/reformatting) This dataset was obtained without gadolinium and with the free-breathing (nonenhanced echocardiogram-gated three-dimensional steady-state free-precession magnetic resonance angiography). RCA = right coronary artery. Reproduced with permission from Cavalcante and Schoenhagen.89
peripheral vascular disease significantly increases the risk of complications.30,35 A greater than 90° curvature in the vasculature is generally associated with difficulties in access and advancement of the valve system.36,37 In addition, accurate assessment of the luminal diameter and vessel characteristics at site of sheath insertion are necessary. Currently the Edwards SAPIEN system is 22–24 Fr in size, requiring a 7–8-mm inner luminal vessel diameter to accommodate it. In comparison, CoreValve is a 18 Fr system, requiring a 6-mm luminal diameter. It is known that, when the sheath stretches the artery >1.05 times its diameter, mortality, and bleeding outcomes increase significantly.38 Moreover, calcification extending more than 180° in the vessel results in poor ability of the vessel to accommodate larger sheaths.38 If both iliac arteries are not suitable for access, based on MDCT, then an axillary artery or transapical approach might be considered.36,39 Clearly, adequate assessment of vasculature helps 684
to determine the ideal route in advance of the procedure. With the newer generation smaller profile valves, a reduction in sheath size is expected, resulting in systems being more accommodative in smaller vessels. Edwards XT will use 18 Fr and 19 Fr sheaths. Annular Assessment: Evaluation of the AV annulus anatomy is extremely important for a successful TAVR outcome. The aortic prosthetic size is dictated by the AV annular diameter, making this measurement a critical one for procedural success. Any errors at this level could result in serious complications. One of the main utilities of MMI is accurate determination of the annular dimensions. True annulus/surgical annulus is measured at the LVaorta junction. However, for TAVR purposes, the annulus is defined by a plane which transects the base of all three cusps of the AV (Fig. 3). This is the narrowest portion in the AV and the
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Figure 8. Localization of the LM coronary artery by multidetector computed tomography and 3DTEE. A. Multidetector computed tomography imaging used to acquire the plane of the left main (LM) coronary artery, with yellow arrow indicating the distance from the hinge point of the left coronary cusp to the LM, and red arrow indicating the length of the left coronary cusp. B. Multiplanar reconstruction of a three-dimensional (3D) transesophageal echocardiography (TEE) volume set in the transverse plane. The blue arrow shows the plane of the LM coronary artery. C. Multiplanar reconstruction of a 3DTEE volume set showing the plane of the LM ostium and coronary artery. This plane is used to measure the length of the left coronary cusp (red arrow) and the distance from the hinge point of that cusp to the LM coronary ostium (yellow arrow) in systole. Ao = aorta; LV = left ventricle. Reproduced with permission from Bloomfield et al.37
dimensions obtained at this level determine the size of the device. This measurement can be obtained in the parasternal long-axis view using TTE or mid-esophageal reverse long-axis view at 120° in TEE, from the base of the right coronary cusp to the base of the commissure between left and noncoronary cusps in systole (Fig. 4).23 TTE may slightly underestimate aortic annular size when compared with TEE.40 The aortic annulus is not exactly round but has an oval shape with long and short diameters. Hence, it is recommended to obtain the widest dimensions along the long diameter and in a plane, which transects the base of all three cusps. Even TEE is known to underestimate the true annulus diameter when compared with the cylindrical sizers used in surgery, suggesting the diffi-
culty in identifying the angle with the widest diameter.41 This problem can be overcome by using biplane TEE acquisitions (Fig. 4), multiplanar analysis of 3DTEE, or MDCT,23,40 which allows the assessment of both diameters, the circumference, and area. Three-dimensional TEE planimetry of the annulus has been shown to improve the prosthesis size selection and to predict significant postprocedural AI.42 MDCT plays a significant role in accurately obtaining these measurements because the coronal, sagittal, and transverse imaging planes can be adjusted in 3 dimensions using the turnaround rule. A cross section can then be obtained at the right level to get precise dimensions (Fig. 5).43 With semiautomated quantification, analysis time can be significantly reduced, resulting in a better
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Figure 9. Coronary CT angiogram (CTA) of left ventricular outflow track (LVOT) aortic root angulation (ARA). Measurement of LVOT-ARA is performed using a coronal oblique projection and is defined as the angle between the axis of the first portion of the ascending aorta corresponding to the upper part of the bioprosthesis, and the LVOT axis corresponding the distal portion or landing zone of the prosthesis. This measurement is critical for determining whether the prosthesis will properly sit within the aorta. Patients with an LVOT-ARA >90°are not candidates for TAVI. Courtesy UTMB Department of Radiology.
inter-observer agreement. These advancements can result in significant improvement in the workflow and standardization of the annular measurements in evaluation for TAVR.44 Renal dysfunction places a major limitation on the use of MDCT. Intracardiac echocardiography (ICE) has good correlation with MDCT in obtaining dimensions at the aortic annulus and the sinus of Valsalva, and can be a valuable tool in this group of patients (Fig. 6, movie clip S1).45 In a study by Jabbour et al.22 CMR and cardiac CT measurements of the aortic annulus and the aorta showed close agreement in TAVR
candidates, making CMR a great option in patients with renal dysfunction, as the use of gadolinium-based contrast is not required (Fig. 7). When compared with CT, the use of 3DTEE with post processing (Q-Lab, Philips Healthcare Best, The Netherlands) is reported to have moderate correlation in the measurement of dimensions, with slightly smaller overall measurements including the eccentricity index (1-minimum diameter/maximum diameter).46 Moreover, 3DTEE has comparable sensitivity and specificity to CT in predicting paravalvular regurgitation of moderate or greater intensity, which is superior to 2DTEE, based on the predetermined cutoffs.47 Hence, in patients with limitations for use of contrast, 3DTEE might be a good alternative (Fig. 8). Aortic root angulation is another critical parameter for TAVR success, playing a role in the ability of the deployed valve to sit in the right location. It is obtained in the oblique coronal plane by MDCT and defined as the angle between the axes of the LVOT and the proximal portion of the ascending aorta (Fig. 9).48 An angle greater than 90°is a contraindication for TAVR. A smaller angle facilitates correct positioning of the valve. Height of the Coronary Ostia: It is important to measure the height of the coronary ostia from the annulus for TAVR because the leaflets of the native valve approximate against the aortic wall. In some cases, the stent in which the valve is placed may impede the coronary ostial flow. Moreover, it can make future access of the ostia difficult especially if angiography is needed. This is noted to be more of a concern in balloon expandable valves.49 The recommended annulus to ostia length is >10–11 mm for the
Figure 10. Quantification and characterization of the calcium burden of each calcium nodule and the whole aortic valve with multidetector CT. For each nodule the volume and mass are quantified, and also its situation about the specific cusp and location within the valve (annulus, leaflet, or both) are determined. Aortic valve total calcium burden is obtained by adding the volume and mass of each calcium nodule. A global evaluation of the most calcified cusp and the eccentricity of calcification are finally performed. Mg Ca HA, milligrams of calcium-hydroxyapatite. Reproduced with permission from Azzalini et al.51
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TABLE III Imaging Parameters and Complications Intra-Procedural Assessment Annular size correlation Accuracy of device positioning Immediate device complications Paravalvular leak Device embolization Periprocedural events Coronary ostial occlusion/embolization Worsening AI/MR Pericardial effusion/tamponade LV perforation Aortic dissection AI = aortic regurgitation; MR = mitral regurgitation.
Edwards SAPIEN valve depending on its size.3 For CoreValve, there is no recommended annulus to ostia length. However, it is important to be aware of this measurement and the
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length of the cusps to estimate the risk of coronary occlusion. The height to the right coronary annularostial distance can be measured in the TTE parasternal long-axis view or the reverse longaxis mid-esophageal view by TEE at 120–140° (Fig. 7). Visualization of the ostium of the left main coronary artery is more complex and requires biplane imaging, 3DTEE, or MDCT.30 The origin of the left main needs to be visualized in the short axis of the AV (mid esophageal 30°) and an image 90° to that plane crossing through the ostium of the left main artery needs to be obtained using the biplane technique in 3DTEE. This facilitates visualization of the distance between annulus and the ostium of the left main coronary artery. MDCT, due to its ability to obtain images in multiple planes, has an advantage in providing these measurements with greater ease (Fig. 6). In the case of renal dysfunction, CMR is valuable in determining the distance between the aortic annulus and coronary ostia.21
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Figure 11. 1. Suggested scheme and real-world application of the rule in normal aortic root anatomy. A. Schematic illustration of the “follow the right cusp” rule pointing to the proper alignment in the case of normal aortic root anatomy. B. Example of normal aortic root anatomy: images are provided without (upper images) and with (lower images) a schematic overlay. The white arrow indicates the pigtail catheter. Panels I through III show fluoroscopy-guided alignment of the aortic plane; panel IV shows the final result. CAU = caudal; CRA = cranial; L = left cusp; LAO = left anterior oblique; N = noncoronary cusp; R = right cusp; RAO = right anterior oblique. Reproduced with permission from Kasel et al.57 2. Suggested scheme and real-world application of the rule in horizontal aortic root anatomy. A. Schematic illustration of the “follow the right cusp” rule pointing to the proper alignment in the case of “horizontal” aortic root anatomy. B. Example of horizontal aortic root anatomy: images are provided without (upper images) and with (lower images) a schematic overlay. The white arrow indicates the pigtail catheter. Panels I through IV are as described in (1). Abbreviations as in (1). Reproduced with permission from Kasel et al.57
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mass of the largest calcium nodule, has been found to be an independent predictor of PVR. Other predictors are the number of calcified nodules, severe calcification in the landing area, and annulus area (Fig. 10).51 Certain parameters, including cover index of average annular diameter, obtained from the perimeter using 3DTEE (Q-Lab software) have been noted to have good sensitivity in predicting PVR with effective regurgitant orifice ≥29 mm2. Cover index is defined as 100 9 [(transcatheter heart valve diameter (THV) TEE annular diameter)/THV diameter]. A large aortic annulus size measured by MRI and CT has been reported to predict PVR. These studies suggest that a certain amount of oversizing may prevent PVR. Oversizing the valve by at least 1 mm relative to the mean annular diameter or by >10% of the annular area, as measured by MDCT, has reduced the risk of PVR.52,53 Figure 12. Transesophageal echocardiography biplane imaging to assess annular dimensions and predict aortic regurgitation A. Biplane imaging during balloon inflation. The green arrows identify the waist of the balloon at the level of the annulus. The blue arrow shows asymmetric balloon dilation at the commissure between the left and noncoronary cusps. The yellow arrows depict acoustic shadowing, which prevents adequate visualization of the peri-balloon region. B. The red arrows predict aortic regurgitation at the sites predicted during aortic balloon valvuloplasty. Reproduced with permission from Bloomfield et al.37
Degree and Location of Aortic Valve Calcification: Accurate assessment of calcification of the AV is important. The presence of some calcium is necessary for the valve to sit in place. However, large amounts of eccentric calcification result in inadequate apposition of the valve, leading to paravalvular leaks (PVR). In some cases, fusion of two leaflets with calcium can lead to a functional bicuspid valve, which may pose difficulty in adequate valve expansion. When the balloon is inflated, large calcium deposits noted at the tips of leaflets can potentially embolize into the coronaries, pushing the leaflets close to the coronary ostia.50 In cases with large calcification in the native valve, a smaller prosthesis than suggested by the annular dimension may be advisable. Fluoroscopy may also provide additional measurements at the time of definitive prosthesis sizing decision.30 Predicting Paravalvular Regurgitation: Multimodality imaging has a major role in predicting PVR. Multiple models have been proposed in this regard. Aortic valve calcium nodule score, computed as AV calcium mass x 688
Preprocedural Planning: All the information discussed in the preceding sections helps in: (1) planning the procedure; (2) determining the route of access; size and type of prosthesis; speed of the procedure; and level of pacing; and (3) anticipating problems such as inadequate expansion of valve or possibility of PVR; possibility of device migration; and development or worsening of MR leading to flash pulmonary edema. Being aware of these possibilities ahead of time allows for better planning and the ability to deal with these complications should they arise. Intra-Procedural Use: Intra-procedural use of MMI is an essential final step to correlate with the preprocedural assessment prior to the valve deployment. This step also serves as continuous vigilance in appropriate positioning and identification of early complications following balloon valvuloplasty and valve deployment (Table III). Primarily, intra-operative imaging is carried out by TEE and fluoroscopy. Some centers have used DynaCT or rotational angiography for implant selection and 3D model generation during rapid pacing with all the necessary cardiac landmarks.54,55 Real time CMR has been successfully tested in animal models, which may lead to its use in the near future especially with its benefits in reducing radiation and the lack of contrast usage. Annular Size Correlation: Prior to device placement, a final determination on the size of the device is made from assessing the waist diameter of the balloon used for
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Figure 13. Grading criteria for paravalvular AR. A. Schematic and illustrated representation of the short-axis view at the level of the aortic valve by echocardiography. B. Echocardiographic and schematic illustrations of the short-axis view of the aortic valve. Paravalvular aortic regurgitation (AR) can be graded according to the circumferential extent of the regurgitant jet. Paravalvular AR can be graded as mild, moderate, or severe on the basis of a circumferential extent of 20%, respectively. See Leon et al.90 RV = right ventricle. Image credit: CC Patrick J. Lynch and C. Carl Jaffe, Yale University, 2006. Reproduced with permission from Bloomfield et al.37
Figure 14. Treatment algorithm for PAR after TAVR. Treatment algorithm using a multimodal approach with the use of hemodynamic measurements and imaging modalities to quantify the severity of PAR during the TAVR procedure and to identify patients who will benefit from corrective measures. AR = aortic regurgitation; TEE = transesophageal echocardiography; TTE = transthoracic echocardiography. Reproduced with permission from Sinning et al.67
valvuloplasty. Any significant variations should be addressed at this time.41 This is an important step because reports suggest that balloon valvuloplasty leads to adjustment of prosthesis size in 25% of patients.56 This step can be performed under
fluoroscopic guidance but does come with the intrinsic limitation of obtaining images in a plane that is perfectly perpendicular to the native valve. Newer balloons with surrounding radiopaque circles will likely eliminate the uncertainty when imaging the balloon perpendicular to its position when fully inflated. “Follow the right cusp rule” proposed by Kasel et al.57 simplifies the steps to define the perpendicular annulus plane by fluoroscopy in both the normal and horizontally aligned heart (Fig. 9). This technique can be quickly done at the beginning of the procedure to improve the accuracy of valve placement. The steps of the procedure are (1) with a pigtail catheter in the right cusp, aortogram is carried out in left anterior oblique (LAO) 10° cranial (CRA) 10°; (2) the C-arm is then rotated to right anterior oblique (RAO) or LAO position to have right cusp in the center of aorta; and (3) the C-arm is then rotated in the cranial or caudal direction to bring the base of the right cusp at the annular level. These steps result in obtaining the perpendicular annulus plane. In a horizontal heart the sequence is similar. However, RAO and LAO rotations are intended to get the right cusp at the annular level, and cranial and caudal motion to center the right cusp (Fig. 11).57 TEE can be used to guide positioning of the balloon relative to the AV. It is especially useful when the valve is not very calcified and, 689
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Figure 15. Origin and mechanism of paravalvular aortic regurgitation (PAR). A. Transesophageal echocardiography (TEE) longaxis view of Edwards SAPIEN 23-mm prosthesis with both transvalvular AR and PAR (movie clip S2). B. PAR after deployment of an Edwards SAPIEN XT 26-mm prosthesis because of malapposition with the left annulus. The device was not coaxial to the root (movie clip S3). C. TEE short-axis view of underexpanded oval-shaped waist of a Medtronic CoreValve 29-mm prosthesis. D. TEE long-axis view of an Edwards SAPIEN XT 26-mm prosthesis with diameters of 24–26 mm indicating reasonable expansion in the presence of PAR. E. Color three-dimensional TEE of malposition PAR after low implantation of a Medtronic CoreValve prosthesis. The PAR jet passes from within the aortic portion of the stent frame above the tissue skirt (“supra-skirt” PAR) into the paravalvular space and LVOT (movie clip S4). F. TEE of malposition PAR after the high implantation of a Medtronic CoreValve 29-mm prosthesis. The posterior PAR jet passes from the aortic sinus below the tissue skirt (“infra-skirt” PAR) into the LVOT where the irregular inflow edge rises above the native annulus (movie clip S5). AR = aortic regurgitation. Reproduced with permission from Sinning et al.67
consequently, difficult to image on fluoroscopy. Biplane imaging using TEE during balloon inflation is also useful to identify areas of poor expansion. These areas could be the sites of poor apposition of the valve due to calcification and thereby predispose to PVR (Fig. 12).37 TEE may be used to (1) confirm a stable position during inflation and (2) monitor the behavior of the calcified aortic cusps during inflation as they are pushed back into the sinuses and toward the coronary ostia.23 DynaCT is useful during TAVR: this modality can facilitate exact sizing of the aortic annulus and help to prevent obstruction of the coronary arteries.58 However, this approach often requires a large amount of contrast agent, especially in cases of poor calcification of the annulus or the 690
cusps, which may contribute to postoperative renal failure.59 Accuracy of Device Positioning: A combination of fluoroscopy and TEE is used for accurate positioning of the AV across the annulus during deployment. TEE provides continuous real time 3D visualization of the annulus, valve, and the balloon, thereby aiding device placement, prediction, and immediate detection of AI.37 Depth perspective in live 3D mode provides better visualization for positioning the prosthesis on the balloon relative to the native valve annulus and surrounding structures. It also facilitates appreciation of the guide wire path through the LV and around the mitral valve subvalvular apparatus.23 Higher or lower placement of the valve
Multimodality Imaging in TAVR
TABLE IV Evaluation of Complications Postprocedural Use Assessment of valve hemodynamics Valve area and gradients Patient prosthesis mismatch Monitoring for long-term complications Paravalvular leak Valve thrombosis Endocarditis Device migration Impact on mitral valve Ventricular perforation Effect on concomitant pathologies Systolic and diastolic function Chamber remodeling
may result in supra-skirt or infra-skirt PVR, respectively. In patients with limited native valve calcification or for valve-in-valve procedures where TAVR is used in the setting of another bioprosthesis, TEE may be the main modality used for guidance. The optimal position of the Edwards SAPIEN valve is 2–4 mm below the annular plane in the LVOT. The CoreValve extends 5–10 mm below
the annulus.23 Immediately following deployment, TEE is used to confirm satisfactory positioning and function of the prosthesis. The next generation devices will enable the operator to resheath the device if the position needs to be adjusted during the deployment, making the use of MMI indispensible during the procedure.6 Role of ICE during the TAVR Procedure: ICE has been shown to be effective in reducing contrast use for angiography, resulting in shorter hospital stay, reduced severity, and decreased probability rates of acute kidney injury.60 When compared to TEE, ICE uses less intensive sedation/anesthesia during the procedure, and may reduce the need for probe repositioning. In addition, this technique provides better coaxial Doppler measurements in the ascending aorta leading to superior assessment of intra-procedural pressure gradients (Fig. 11).61 However, true longaxis views of the AV, annulus, and outflow tract are difficult to obtain. Thus, annular and coronary height measurements are not as accurate as those obtained by preprocedure MDCT.45 Immediate Device Complications: The availability of imaging is crucial in monitoring and managing immediate device complications, including device embolization and PVR.
Figure 16. Schematic and examples of spectral Doppler flow acceleration in a SAPIEN transcatheter heart valve. A. Schematic presentation of echocardiographic pulse-wave (PW) Doppler patterns when the sample volume is placed prestent, instent but precusps, and continuous wave (CW) through the aortic valve. Due to flow acceleration, it is imperative that the subvalvular velocities used in either Doppler velocity index or effective orifice area be sampled proximal to the stent. B. The PW Doppler pattern of a sample volume placed before stent. White arrows show the extent of the transcatheter heart valve in the aortic root. Red arrow shows the level of the prosthetic aortic cusps. C. The PW Doppler pattern of sample volume placed within the stent but before cusps. D. The PW Doppler pattern of a sample volume placed at the level of the cusps. Reproduced with permission from Bloomfield et al.37
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Device Embolization: Valve placement at the right location is of pivotal importance in TAVR. Any slight misjudgment can lead to serious consequences, including device embolization toward the ventricle or aorta. If transcatheter repositioning is not feasible, surgical removal may be required. This potential complication can be detected by TEE or fluoroscopy during device deployment. Immediate recognition is critical, not only due to the consequences of the embolized device, but to urgently deal with the hemodynamic changes from AI created by balloon valvuloplasty done right before device deployment. Identification of the location of the embolized valve in the aorta is imperative to its capture, withdrawal, and deployment in the descending aorta.62 Paravalvular Leak: PVR, frequently with multiple jets, is commonly seen following TAVR,4 though trace to mild and with a benign stable course in the majority of patients.63 However, severe AI may occur due to incomplete expansion or incorrect device positioning, restricted cusp motion, or inappropriate prosthetic size.53 These complications can be readily identified both by fluoroscopy and TEE. Limitations to fluoroscopy include difficulty in grading the severity of regurgitation due to significant overlap between the grades and the necessary use of additional contrast. Grading PVR determines the next course of action. Moderate to severe PVR needs correction because it has an impact on patient mortality and morbidity.64 PVR is most suitably evaluated by TEE and is seen as a circumferential leak in the short-axis view. PVR is best detected in TEE at 0° in the deep transgastric view. Semiquantitative measurements such as vena contracta, jet width, and pressure half time cannot be used due to the eccentric nature of the jet.65 However, gradation can be easily performed as illustrated in Fig. 13.37 Hemodynamics offer great help in precisely assessing the grade and deciding for intervention. Sinning et al.66 described aortic regurgitation index (ARI), the ratio of the transvalvular gradient between diastolic blood pressure (RRdia) in the aorta and LVEDP, to systolic blood pressure (RRsys) in the aorta, obtained by the formula LVEDP)/RRsys] 9 100, the value of [(RRdia
which holds an inverse correlation to severity of regurgitation and prognosis. A flow diagram (Fig. 14) described by the same group serves as a good guiding tool in making decisions relevant to the intervention.67 PVR may result from poor apposition due to hindrance from calcium, inferior (ventricular) placement, supra-skirt PVR, or superior (aortic) placement, infra-skirt PVR. TEE can differentiate these three forms (Fig. 15, movie clips S2–S5). Poor apposition can be corrected in some cases with balloon post dilatation. If unsuccessful, an interventional closure with Amplatzer device can be performed.68 Supra-skirt PVR can be corrected by snaring the valve into a more aortic position.68 If this fails, a valve-in-valve implantation can be performed. Infra-skirt PVR is usually corrected by valve-in-valve implant.68,69 Rarely is a central jet of AI seen. This represents potential destruction of one of the leaflets or low diastolic pressure, leading to poor coaptation or leaflet malfunction from a design/structural flaw in the valve. The decision to correct this scenario follows the same guidelines as PVR based on the impact on hemodynamics. Periprocedural Events: Intra-procedural TEE plays a crucial role in early detection of important acute events. A new onset WMA following valvuloplasty or valve deployment suggests occlusion and/or embolization into a coronary artery. Although this complication may be fatal, successful management of ostial occlusions with percutaneous angioplasty or bypass surgery has been reported.70,71 Other possible explanations for acute hemodynamic instability during the procedure that can be identified by TEE are cardiac tamponade, secondary to wire perforation of the left or right ventricle, and severe AI.23 An evaluation by color flow and Doppler across the implanted and native valves will demonstrate aortic and mitral insufficiency following valvuloplasty and valve implantation. Worsened AI after valvuloplasty is a strong reason to proceed quickly with valve implantation, as the stiffer ventricles in patients with longstanding AS can precipitate flash pulmonary edema. Aortic dissection, a tear, or rupture of the aortic root may be observed during the procedure following
Figure 17. A. CT multiplanar reconstruction prior to TAVR. Arrows are pointing to aortic annular calcification extending into the outflow tract at the level of the perimembranous interventricular septum. B. CT multiplanar reconstruction after TAVR. Arrows are pointing to the VSD inferior to the lower border of the SAPIEN valve. The previously seen calcification is no longer present. C. CT multiplanar reconstruction after VSD closure. Arrows are pointing to the membranous VSD occluding device with the LV disk overlapping the lower edge of the SAPIEN valve. Ao = aorta; LA = left atrium; LV = left ventricle; MVR = mechanical mitral replacement; RA = right atrium; RV = right ventricle; S = SAPIEN valve; VSD = ventricular septal defect. Reproduced with permission from Levi et al.85
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Figure 18. A. Longitudinal transcaval/transatrial (A) and short-axis transatrial (B) standard intracardiac echocardiographic views for TAVR. AAo = ascending aorta; AC = AcuNav catheter; AVP = aortic valve prosthesis; DAo = descending aorta; IVC = inferior vena cava; LV = left ventricle; RA = right atrium; RV = right ventricle; SVC = superior vena cava. B. Longitudinal transcaval (A) and short-axis (B) intracardiac echocardiographic views of aortic valve prosthesis after deployment and at enddiastole. Ao = aorta; 1 = minimal paravalvular leak; RCA = right coronary artery. C. Intracardiac spectral Doppler analyses of the native aortic valve (A), after predilatation (B), and after deployment of a 23-mm-diameter Edwards SAPIEN transcatheter heart valve prosthesis (C) on the basis of highest signal quality reveal decline of pressure gradient (PG). D. Longitudinal intracardiac echocardiographic view demonstrates both coronary arteries branching off above the opened aortic valve prosthesis. Ao = aorta; LCA = left coronary artery; RCA = right coronary artery. Reproduced with permission from Bartel et al.61
balloon valvuloplasty or prosthesis deployment, especially in the presence of extensive annular calcification or prosthesis oversizing. Both complications can be identified and necessary early steps taken using intra-operative TEE.23,39 Postprocedural Use: Multimodality imaging has an indispensible role and multiple applications in the postprocedural period, both short- and long-term (Table IV). Assessment of Valve Hemodynamics: Assessment of the relative AVA and gradients at regular intervals is imperative in identifying valve related problems. A good understanding of the hemodynamics inside a stented valve is required for accurate assessment. The ventricular portion of the stent creates flow acceleration into the prosthetic valve (Fig. 16).72 Hence, a PW Doppler measurement in this zone to assess for LVOT TVI will result in a spuriously high number. Used in the continuity equation, this number would calculate a falsely high prosthetic valve area or a normal Doppler velocity index (DVI). Moreover, the stented portion of the LVOT could be extended by the stent itself to a greater dimension than the regular LVOT. Measurement of the diameter in this segment may lead to erroneous calculations. Hence, the PW velocity in the LVOT and LVOT diameter should always be measured proximal to the stent of the valve in the LVOT.73 This discrepancy in measurements is of greater consequence when consecutive measurements are made in different zones, inside the stent versus outside the stent, leading to concern about valve malfunction. An important concept in prosthetic valves is patient-prosthesis mismatch (P-PM). This is more of a concern in surgically implanted valves with incidence ranging from 20 to 70%.74 An EOA
