Background
Paravalvular aortic regurgitation (AR) after transcatheter aortic valve implantation (TAVI) is common, but the evaluation of its severity by two-dimensional (2D) transthoracic echocardiography (TTE) presents several constrains. The aim of this study was to assess the usefulness of a new methodology, using three-dimensional (3D) TTE, for better assessment of paravalvular AR after TAVI.
Methods
Two-dimensional and 3D TTE was performed in 72 patients, 5 months after TAVI, using the X5-1 PureWave microbeamforming xMATRIX probe. The position and severity of the paravalvular AR jets were described using 2D and 3D TTE, and a model was designed for paravalvular AR systematic location description. Vena contracta width was measured using 2D transthoracic echocardiographic views, and the planimetry of the vena contracta was assessed after the perfect alignment plane was obtained using the multiplanar 3D transthoracic echocardiographic reconstruction tool. AR volume was calculated as the difference between 3D TTE–derived total left ventricular stroke volume and right ventricular stroke volume estimated using 2D TTE. Diagnostic efficiency for moderate AR was assessed using receiver operating characteristic curve analysis.
Results
Forty-three patients (57.4%) presented with AR; 10 (13.3%) had central AR, and 33 (44.0%) had paravalvular AR jets. Vena contracta widths were similar between patients with moderate and mild AR (2.1 ± 0.53 vs 1.9 ± 0.16 mm, P = .16), but vena contracta planimetry was larger in patients with moderate AR than in those with mild AR (0.30 ± 0.12 vs 0.09 ± 0.07 cm 2 , P = .001). Vena contracta planimetry on 3D TTE was better correlated with AR volume than vena contracta width on 2D TTE (Kendall’s τ = 0.82 [ P < .001] vs 0.66 [ P < .001]). The areas under the receiver operating characteristic curves were 0.96 for vena contracta planimetry and 0.35 for vena contracta width.
Conclusions
This study proposes an alternative methodology for paravalvular AR assessment after TAVI. Using vena contracta planimetry on 3D TTE, an accurate methodology for paravalvular AR jet evaluation and moderate AR classification is described.
Transcatheter aortic valve implantation (TAVI) techniques have been recently recognized as an alternative treatment for patients with severe aortic stenosis and high surgical risk. Favorable hemodynamic results with a low incidence of prosthesis-patient mismatch have been demonstrated, although some degree of residual aortic regurgitation (AR), particularly in the paravalvular region, is common. Paravalvular AR appears to be minor in most patients, but the hemodynamic impact and effect on cardiac chamber remodeling is unknown. Conversely, paravalvular leaks secondary to aortic valve replacement were found to be responsible for hemodynamic deterioration, left ventricular remodeling, or hemolysis. As a result, accurate evaluation and detailed description of AR after TAVI are essential for proper follow-up. However, until now, it has been challenging because no systematic methodology has been proposed. Moreover, the assessment of AR severity by two-dimensional (2D) transthoracic echocardiography (TTE) is demanding, and its limitations require the use of an integrative approach for an adequate evaluation of severity.
Vena contracta width by 2D TTE is one of the most robust measurements of AR in native valves, and it is well correlated with angiographic grading and regurgitant orifice area. However, its assessment might be difficult in the presence of a prosthesis. In the parasternal long-axis or apical view on 2D TTE, only one dimension of the AR jet is visualized. Consequently, the area can only be estimated using an assumption of its shape, commonly circular or elliptical, which is mostly an incorrect assumption. In theory, using 2D transthoracic echocardiographic color Doppler in the short-axis view, the vena contracta shape could be delineated either in a native valve or in a biologic prosthesis. However, it is impossible to ensure that the plane is exactly parallel to the vena contracta or that one is not measuring the jet size in a larger stream, particularly in presence of eccentric jets.
Three-dimensional (3D) transthoracic echocardiographic color evaluation of AR is based on the acquisition of a pyramidal data set, with the aortic valve and paravalvular region inside it. Once performing the cropping to the correct angle, the precise location of an AR jet can be described and the real vena contracta shape planimetered. Accordingly, 3D TTE represents an enhancement of 2D TTE. In the present study, we considered the usefulness of a new methodology using 3D TTE for the accurate assessment of paravalvular AR after TAVI.
Methods
This study included 72 patients with severe aortic valve stenosis (aortic valve area ≤ 1 cm 2 ) who underwent successful TAVI. All patients had degenerative aortic stenosis and tricuspid aortic valves. These patients were obtained from a series of 97 consecutive patients who underwent TAVI, after excluding those with concomitant moderate to severe mitral valve disease (six patients) and those not able to come to follow-up (19 patients).
Patients were referred for TAVI because of an excessive risk for aortic valve replacement, which was estimated using the logistic European System for Cardiac Operative Risk Evaluation score and/or clinical judgment. The procedure was performed with fluoroscopic and transesophageal echocardiographic guidance (Philips iE33, X7-2t 7-MHz probe; Philips Medical Systems, Eindhoven, The Netherlands) using the techniques described in detail in previous reports. Two valve sizes are available, 23-mm and 26-mm expanded diameter for Edwards Sapien valves (Edwards Lifesciences, Irvine, CA) and 26 and 29 mm for CoreValve devices (Medtronic, Inc., Minneapolis, MN). The aortic prosthesis size was decided according to the annular diameter, measured with transesophageal echocardiography (TEE).
TTE
TTE was performed 5 months after TAVI, from June to October 2010, using the X5-1 PureWave microbeamforming xMATRIX probe (Philips Medical Systems). This probe presents all the facilities of the 2D S5-1 probe with 3D capabilities as full volume, Live 3D, and Live 3D color acquisitions, from one to four beats. The full volume combines a series of four subvolumes acquired with electrocardiographic gating to create the final reconstructed image. This acquisition mode is essential for the measurement of volumes and left ventricular ejection fraction by 3D volumetric assessment. Live 3D and Live 3D color provide real-time 3D volumetric motion, without electrocardiographically gated reconstruction. However, these acquisition modes can be optimized for a higher frame rate by performing near-real-time images, with electrocardiographically gated reconstruction, with up to four heartbeats. In this study, we used Live 3D without electrocardiographically gated reconstruction and Live 3D color images acquired with four heartbeats. We used iCrop, a new flexible tool that allows direct analysis on Live 3D and Live 3D color images, for interpretation while performing the exams.
First, conventional 2D TTE was performed, in which the prosthesis area was calculated using the continuity equation. Apical five-chamber, three-chamber, and parasternal long-axis and short-axis color views were recorded, and AR jets were described following international standard recommendations. We systematically assessed the vena contracta width in the parasternal long-axis or apical long-axis view using a Nyquist limit of 50 to 60 cm/sec ( Figure 1 ). AR volume was calculated as the difference between 3D TTE–derived total left ventricular stroke volume and stroke volume through the right ventricular outflow tract. The right ventricular outflow tract diameter and velocity-time integral at the site were measured in the short-axis parasternal view, and the right ventricular stroke volume was calculated by multiplication of the cross-sectional right ventricular outflow tract area by the velocity-time integral. AR was graded using an integrative approach considering the recommended semiquantitative Doppler parameters and the AR volume as mild (AR volume < 30 mL) or moderate (30 mL ≤ AR volume ≤ 59 mL), assessed as previously described.
![](https://i0.wp.com/thoracickey.com/wp-content/uploads/2018/06/gr1-264.jpg?w=960)
Full-volume and Live 3D color images were acquired from one to four heartbeats in the apical four-chamber view. At the time of acquisition, we used the 3D TTE and two orthogonal 2D transthoracic echocardiographic views for guidance, as illustrated in Figures 2 A and 3 . If necessary, we adjusted the lateral and the elevation width to be certain that all of the structures we intended to analyze were included in the volumetric images acquired. Full-volume acquisitions, obtained by combining four electrocardiographically gated subvolumes, were used to measure left ventricular volumes and ejection fraction by direct volumetric analysis ( Figure 2 ). We assessed the aortic prosthesis using Live 3D views ( Figure 4 ). Using Live 3D color images, with the narrowest sector possible for frame rate optimization, the aortic prosthesis was isolated with the iCrop tool. The entire circumference of the prosthesis, and the paravalvular region, were viewed from the aortic root and also from the ventricular aspect, as illustrated in Figure 3 .
![](https://i0.wp.com/thoracickey.com/wp-content/uploads/2018/06/gr2-171.jpg?w=960)
![](https://i0.wp.com/thoracickey.com/wp-content/uploads/2018/06/gr3-106.jpg?w=960)
![](https://i0.wp.com/thoracickey.com/wp-content/uploads/2018/06/gr4-57.jpg?w=960)
The iCrop tool constructs an image from two orthogonal square views, whose size can be adjusted for the proposed region of analysis. The anatomic findings can be viewed from each of the sides of the square ( Figure 3 ); consequently, in the same acquisition, the prosthetic valve can be viewed from the left ventricular outflow tract and also from the aortic root. Depending on the cutting plane, the area of the regurgitant jet varies, because the view from the aortic root shows the isovelocity surface area proximal to the regurgitant orifice, while the view from the left ventricular outflow tract shows the beginning of the color jet as blood entrains and travels into the left ventricle. Consequently, iCrop allowed the identification and localization of the AR jet, but it was not used to measure AR jet size, which was performed using the multiplanar reconstruction tools. To describe AR localization systematically, we designed a reference diagram in which the parasternal short-axis view was chosen as a reference and the paravalvular region divided into 12 sections according to the hours of a clock face ( Figure 5 ).
![](https://i0.wp.com/thoracickey.com/wp-content/uploads/2018/06/gr5-30.jpg?w=960)
For AR vena contracta planimetry by 3D TTE, Live 3D color data sets were analyzed using the multiplanar reconstruction tool. First, the best frame for AR jet visualization in two orthogonal long-axis views was selected. Then we cropped the data set along the axis of the AR jet, from the aortic side to the level of the vena contracta, in a plane that was exactly perpendicular to the long axis of the AR jet. Subsequently, we performed planimetry ( Figure 6 ) using the methodology previously validated by Fang et al. In patients with more than one independent leak, the vena contracta was taken as the sum of all individual vena contracta areas.
![](https://i0.wp.com/thoracickey.com/wp-content/uploads/2018/06/gr6-12.jpg?w=960)
This protocol was approved by the local ethics committee, and all patients gave written informed consent for participation.
Reproducibility
Two experienced operators blinded to 2D echocardiographic results analyzed separately 3D color data sets, worked through the multiplanar reconstruction tools, and performed the vena contracta planimetry in patients with AR.
Statistical Analysis
Categorical variables are expressed as percentages and continuous variables as mean ± SD unless otherwise specified. Continuous variables were compared between groups using unpaired t tests (for normally distributed variables) or the Mann-Whitney U test (for variables not normally distributed). Kendall’s τ (nonparametric test) was calculated for the assessment of correlations between vena contracta measurements by 3D TTE and 2D TTE and AR volume. The diagnostic efficiency of vena contracta width and planimetry was assessed using receiver operating characteristic curve analysis. All reported P values are two tailed, and P values < .05 were considered to indicate statistical significance. Analyses were performed using SPSS version 16.0 (SPSS, Inc., Chicago, IL).
Results
Among the 72 patients included, 39 (54.2%) were women, the mean age was 82 ± 8 years, and the mean log European System for Cardiac Operative Risk Evaluation score was 19.2 ± 9.9. Overall, and according to intervention, baseline patients’ characteristics and echocardiographic data are presented in Table 1 . Most characteristics were similar in both groups, but patients who underwent a transapical approach were younger (77 ± 9 vs 84 ± 5 years, P = .003) and presented more commonly with peripheral vascular disease (65.2% vs 14.3%, P < .001).
Variable | Overall ( n = 72) | Percutaneous ( n = 49) | Transapical ( n = 23) | P |
---|---|---|---|---|
Clinical characteristics | ||||
Age (y) | 82 ± 8 | 84 ± 5 | 77 ± 10 | .003 |
Women | 39 (54.2%) | 30 (61.2%) | 9 (39.1%) | .133 |
Log EuroSCORE (%) | 19.1 ± 9.9 | 19.2 ± 8.2 | 18.8 ± 13.0 | .544 |
Hypertension | 59 (81.9%) | 41 (83.7%) | 18 (78.3%) | .820 |
Diabetes | 20 (27.8%) | 11 (22.4%) | 9 (39.1%) | .234 |
Dyslipidemia | 44 (61.1%) | 25 (51.0%) | 19 (82.6%) | .021 |
Coronary artery disease | 30 (41.7%) | 19 (38.8%) | 11 (47.8%) | .638 |
Previous PCI or prior CABG | 24 (33.3%) | 13 (26.5%) | 11 (47.8%) | .129 |
COPD | 29 (40.3%) | 19 (38.8%) | 10 (43.5%) | .903 |
Renal impairment | 20 (27.8%) | 11 (22.4%) | 9 (39.1%) | .234 |
Peripheral vascular disease | 22 (30.6%) | 7 (14.3%) | 15 (65.2%) | <.001 |
Echocardiographic characteristics | ||||
Mean aortic pressure gradient (mm Hg) | 52 ± 16 | 54 ± 16 | 47 ± 13 | .073 |
Aortic peak pressure gradient (mm Hg) | 86 ± 24 | 88 ± 24 | 81 ± 24 | .198 |
Aortic valve area (cm 2 ) | 0.6 ± 0.1 | 0.6 ± 0.1 | 0.6 ± 0.1 | .465 |
LVEF (%) | 59 ± 13 | 58 ± 14 | 59 ± 13 | .865 |
Systolic aortic annular diameter (mm) | 21.2 ± 2.4 | 21.2 ± 2.5 | 21.2 ± 2.3 | .972 |
Device | ||||
Edwards Sapien valve | ||||
23 mm | 24 (47.1%) | 16 (57.1%) | 8 (34.8%) | .105 |
26 mm | 27 (52.9%) | 12 (42.9%) | 15 (65.2%) | |
CoreValve | ||||
26 mm | 19 (90.5%) | 19 (90.5%) | 0 | — |
29 mm | 2 (9.5%) | 2 (9.5%) | 0 |
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