Downloaded from http://heart.bmj.com/ on March 10, 2015 - Published by group.bmj.com
Valvular heart disease
ORIGINAL ARTICLE
Aortic regurgitation severity after transcatheter aortic valve implantation is underestimated by echocardiography compared with MRI Stefan Orwat,1 Gerhard-Paul Diller,1 Gerrit Kaleschke,1 Gregor Kerckhoff,1 Aleksander Kempny,1 Robert M Radke,1 Boris Buerke,2 Matthias Burg,2 Christoph Schülke,2 Helmut Baumgartner1 1
Division of Adult Congenital and Valvular Heart Disease, Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany 2 Department of Clinical Radiology, University Hospital of Muenster, Muenster, Germany Correspondence to Professor Helmut Baumgartner, Division of Adult Congenital and Valvular Heart Disease, Department of Cardiovascular Medicine, University Hospital Muenster, Albert-SchweitzerCampus 1, Muenster 48149, Germany; helmut. [email protected] Received 7 February 2014 Revised 29 June 2014 Accepted 2 July 2014 Published Online First 24 July 2014
▸ http://dx.doi.org/10.1136/ heartjnl-2014-306390
To cite: Orwat S, Diller G-P, Kaleschke G, et al. Heart 2014;100:1933–1938.
ABSTRACT Objective Aortic regurgitation (AR) after transcatheter aortic valve implantation (TAVI) is associated with a poor clinical outcome and its assessment therefore crucial. Quantification of AR by transthoracic echocardiography (TTE), however, remains challenging in this setting. The present study used quantitative flow measurement by cardiac MRI (CMR) with calculation of regurgitant fraction (RF) for the assessment of AR and compared the results with TTE. Methods and results We included 65 patients with a mean age of 82.2±8.1 years (38 women) who underwent successful TAVI with Edwards SAPIEN valves (52 transfemoral, 13 transapical). The postinterventional degree of AR was assessed by CMR and by TTE. There was agreement between CMR and TTE with regards to the absence of severe AR. However, TTE significantly underestimated the presence of moderate AR classifying it to be mild in 38 and moderate in only 5 patients, whereas CMR found mild AR in 23 and moderate in 16 patients. Overall, there was only fair agreement between CMR and TTE regarding the grading of AR with a weighted κ of 0.33. The rate of detection of TTE for more than mild AR was only 19%. Conclusions Using CMR for the quantification of AR in a sizeable group of TAVI patients, we demonstrate a strong tendency of TTE to underestimate AR compared with CMR. Since higher AR severity on echocardiography has been associated with worse patient outcome, the potential incremental prognostic value of CMR should be studied prospectively in this setting.
valve replacement, it remains common after TAVI with reported trivial or mild AR in up to 70% and moderate AR in more than 10%.8 The negative impact of residual AR on outcome obviously increases markedly with the severity of regurgitation.7 Thus, quantification of AR after TAVI appears crucial. Transthoracic echocardiography (TTE) is currently the standard imaging modality for the detection and quantification of AR after the procedure. While detection of AR is possible with high sensitivity and specificity, its quantification by TTE remains however challenging. The current standard used in TAVI research studies—the Valve Academic Research Consortium (VARC) criteria9— recommend quantitative assessment that has been developed and validated for native AR, such as size of the vena contracta or effective regurgitant orifice area. However, these are difficult to apply in this special setting and may actually not be suitable for evaluation of AR after TAVI.10 Magnetic resonance phase-contrast imaging (CMR), on the other hand, allows for accurate and reproducible blood flow measurement in the ascending aorta and quantitative assessment of the severity of AR by calculation of regurgitant fraction (RF).11–15 Applicability and accuracy of this technique should not be affected by the specific setting—native AR versus paravalvular AR. Considering the critical effect of AR severity on outcome after TAVI and the difficulties to quantify AR by TTE in this setting, we sought to assess AR severity in a series of TAVI patients by CMR and compare the results with TTE findings.
INTRODUCTION
METHODS
Since its introduction in 2002, transcatheter aortic valve implantation (TAVI) has evolved as a promising alternative to conventional aortic valve replacement in surgical high-risk patients.1 One of the major concerns after aortic valve intervention remains postprocedural aortic regurgitation (AR), which has been linked to adverse outcome after surgical aortic valve replacement as well as TAVI.2–5 In both settings, even mild paravalvular AR has been associated with increased long-term mortality.6 7 After TAVI, several aetiologies for AR have been proposed, including annulus-prosthesis-size mismatch and insufficient sealing in the setting of heavily calcified cusps. While paravalvular AR has become rare with current surgical techniques of
We enrolled consecutive patients who had undergone TAVI at our institution and presented for regular follow-up visits. Patients underwent CMR if they had no contraindication such as an implanted pacemaker, the examination was logistically possible and the patient agreed to the additional diagnostic procedure but were otherwise not selected. All patients provided written informed consent, and the institutional review board approved the study. The decision for TAVI was made in accordance with current guidelines and after discussion and consensus within a multidisciplinary Heart Team consisting of cardiologists and cardiac surgeons. The TAVI procedure was performed with the balloon-expandable
Orwat S, et al. Heart 2014;100:1933–1938. doi:10.1136/heartjnl-2014-305665
1933
Downloaded from http://heart.bmj.com/ on March 10, 2015 - Published by group.bmj.com
Valvular heart disease Edwards-SAPIEN or SAPIEN XT valve prosthesis (Edwards Lifesciences, Irvine, California, USA), which was available at this time in 23 and 26 mm sizes. Preprocedural annulus dimension was evaluated in all patients by ECG-gated CT and transesophageal echocardiography (TEE). Additional balloon sizing (angiography during balloon valvuloplasty) was performed in the case of uncertainty about the appropriate valve size. All procedures were performed under general anaesthesia and echocardiography guidance by TEE. Transfemoral access was used in 52 patients while a transapical access route was chosen in 13 patients because of poor vascular access. At the end of the TAVI procedure, the degree of postprocedural AR was evaluated angiographically and by TEE after final device deployment and removal of the catheter and the guidewire. After hospital discharge, clinical and TTE follow-up was obtained in all patients at 1–3 months, 6 months, 1 year and then annually. At one of these follow-up visits, patients had CMR and TTE generally within 24 h of each other.
Echocardiographic assessment All echocardiograms were performed by one of two experienced echocardiographers (SO and AK) using a commercially available echocardiographic machine (Vivid E9 System, General Electric, Milwaukee, Wisconsin, USA) according to a standardised local protocol. Loops were recorded in accordance with published recommendations with subjects in the left lateral position.16 17
All recordings were stored digitally for offline analysis. The AR severity was graded according to the recommendations of the European Association of Echocardiography18 and the VARC criteria9 19 with a special focus on semiquantitative parameters like diastolic flow reversal in the descending aorta measured by pulse-wave Doppler and circumferential extent of prosthetic valve paravalvular regurgitation. Unfortunately due to limited acoustic windows, adequate echocardiographic quantification of RF was only possible in a minority of patients and has therefore not been included as part of the analysis. All Doppler measurements were evaluated as the average of at least three cycles in patients with sinus rhythm or more than five cycles in those with atrial fibrillation. For the detection of regurgitant jets, the parasternal long-axis and short-axis views, the apical long-axis view and the five-chamber view were used (figure 1). Similar to the approach for native aortic valvular regurgitation, an integrative approach was applied to grade the AR. The degree of AR was classified into one of four grades: absent, mild, moderate or severe. In the presence of multiple AR jets, the overall degree of both paraprosthetic and central components was estimated in accordance with the VARC recommendations.9 In addition, a prominent holodiastolic flow reversal in the descending aorta classified a patient to have a more than mild AR.20 This evaluation of AR was performed by an echocardiographer who did not attend to the TAVI procedure and who was blinded to the results of the CMR evaluation of AR.
Figure 1 Example of transthoracic echocardiography in a patient with an Edwards SAPIEN prosthesis. Aortic regurgitation was graded by colour Doppler-echocardiography and CW-Doppler as moderate in this example. 1934
Orwat S, et al. Heart 2014;100:1933–1938. doi:10.1136/heartjnl-2014-305665
Downloaded from http://heart.bmj.com/ on March 10, 2015 - Published by group.bmj.com
Valvular heart disease Magnetic resonance imaging All CMR examinations were performed in our radiology department on a 1.5-T MRI system (Achieva, Philips Healthcare, Best, the Netherlands) equipped with a standard five-element cardiac phased array coil for signal reception and a vector electrocardiograph for cardiac synchronisation. All scans were accomplished without sedation. The image acquisition and subsequent analysis was carried out according to current guidelines.21 For cine imaging, a single-slice two-dimensional (2D) balanced steady-state free precession (SSFP) sequence in breath-hold technique and with retrospective ECG triggering was used. Imaging parameters were chosen as follows: echo time (TE) and repetition time (TR) were set to shortest resulting in an average TR of around 4 ms and a TE of 2 ms slightly varying with slice orientation, typically 25 phases per cardiac cycle and with a reconstructed in-plane resolution of 1 mm. The slice thickness usually was in the range of 6–8 mm. The typical temporal resolution of the cine b-SSFP sequences was 30–40 ms depending on the heart rate. The slice for the through-plane phase-contrast flow imaging was placed perpendicular to the direction of flow approximately 10 mm above the aortic prosthesis. This adequate distance to the prosthesis was kept, as phase-contrast acquisitions may be prone to magnetic field inhomogeneities. Sequences for orthogonal images in at least two views were used to ensure the image plane is truly perpendicular to the flow direction. To avoid aliasing, velocity encoding was individually adapted, starting at 200 cm/s, and if aliasing occurred, the
maximum velocity was increased by 50 cm/s steps until aliasing did not occur. Image acquisition is gated to the ECG signal and acquired over several cardiac cycles during a 10–20 s breathhold. Outlining the region of interest within the aortic lumen for each cardiac phase, the instantaneous flow volume (cm3/s) can be calculated and graphically displayed over the entire cardiac cycle (figure 2). The software calculates forward and reversed flow volumes, and from them the regurgitation fraction as follows: aortic regurgitation fraction (RF, %)=diastolic reversed flow volume×100/systolic forward flow volume. As previous comparisons in native valves with both modalities suggest, AR severity was classified with RF below 10% as absent/minimal, 10–20% as mild, 20–40% as moderate and greater than 40% as being severe (table 1).13 14 22–24
Statistical analysis Values are presented as mean and SD or median and IQR (25th and 75th centile), depending on variable distribution. Categorical variables are presented as frequencies and percentages. Comparisons between subgroups were performed by unpaired t test, Mann–Whitney U test or χ2 test as appropriate. For all analyses, a two-tailed p
Valvular heart disease
ORIGINAL ARTICLE
Aortic regurgitation severity after transcatheter aortic valve implantation is underestimated by echocardiography compared with MRI Stefan Orwat,1 Gerhard-Paul Diller,1 Gerrit Kaleschke,1 Gregor Kerckhoff,1 Aleksander Kempny,1 Robert M Radke,1 Boris Buerke,2 Matthias Burg,2 Christoph Schülke,2 Helmut Baumgartner1 1
Division of Adult Congenital and Valvular Heart Disease, Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany 2 Department of Clinical Radiology, University Hospital of Muenster, Muenster, Germany Correspondence to Professor Helmut Baumgartner, Division of Adult Congenital and Valvular Heart Disease, Department of Cardiovascular Medicine, University Hospital Muenster, Albert-SchweitzerCampus 1, Muenster 48149, Germany; helmut. [email protected] Received 7 February 2014 Revised 29 June 2014 Accepted 2 July 2014 Published Online First 24 July 2014
▸ http://dx.doi.org/10.1136/ heartjnl-2014-306390
To cite: Orwat S, Diller G-P, Kaleschke G, et al. Heart 2014;100:1933–1938.
ABSTRACT Objective Aortic regurgitation (AR) after transcatheter aortic valve implantation (TAVI) is associated with a poor clinical outcome and its assessment therefore crucial. Quantification of AR by transthoracic echocardiography (TTE), however, remains challenging in this setting. The present study used quantitative flow measurement by cardiac MRI (CMR) with calculation of regurgitant fraction (RF) for the assessment of AR and compared the results with TTE. Methods and results We included 65 patients with a mean age of 82.2±8.1 years (38 women) who underwent successful TAVI with Edwards SAPIEN valves (52 transfemoral, 13 transapical). The postinterventional degree of AR was assessed by CMR and by TTE. There was agreement between CMR and TTE with regards to the absence of severe AR. However, TTE significantly underestimated the presence of moderate AR classifying it to be mild in 38 and moderate in only 5 patients, whereas CMR found mild AR in 23 and moderate in 16 patients. Overall, there was only fair agreement between CMR and TTE regarding the grading of AR with a weighted κ of 0.33. The rate of detection of TTE for more than mild AR was only 19%. Conclusions Using CMR for the quantification of AR in a sizeable group of TAVI patients, we demonstrate a strong tendency of TTE to underestimate AR compared with CMR. Since higher AR severity on echocardiography has been associated with worse patient outcome, the potential incremental prognostic value of CMR should be studied prospectively in this setting.
valve replacement, it remains common after TAVI with reported trivial or mild AR in up to 70% and moderate AR in more than 10%.8 The negative impact of residual AR on outcome obviously increases markedly with the severity of regurgitation.7 Thus, quantification of AR after TAVI appears crucial. Transthoracic echocardiography (TTE) is currently the standard imaging modality for the detection and quantification of AR after the procedure. While detection of AR is possible with high sensitivity and specificity, its quantification by TTE remains however challenging. The current standard used in TAVI research studies—the Valve Academic Research Consortium (VARC) criteria9— recommend quantitative assessment that has been developed and validated for native AR, such as size of the vena contracta or effective regurgitant orifice area. However, these are difficult to apply in this special setting and may actually not be suitable for evaluation of AR after TAVI.10 Magnetic resonance phase-contrast imaging (CMR), on the other hand, allows for accurate and reproducible blood flow measurement in the ascending aorta and quantitative assessment of the severity of AR by calculation of regurgitant fraction (RF).11–15 Applicability and accuracy of this technique should not be affected by the specific setting—native AR versus paravalvular AR. Considering the critical effect of AR severity on outcome after TAVI and the difficulties to quantify AR by TTE in this setting, we sought to assess AR severity in a series of TAVI patients by CMR and compare the results with TTE findings.
INTRODUCTION
METHODS
Since its introduction in 2002, transcatheter aortic valve implantation (TAVI) has evolved as a promising alternative to conventional aortic valve replacement in surgical high-risk patients.1 One of the major concerns after aortic valve intervention remains postprocedural aortic regurgitation (AR), which has been linked to adverse outcome after surgical aortic valve replacement as well as TAVI.2–5 In both settings, even mild paravalvular AR has been associated with increased long-term mortality.6 7 After TAVI, several aetiologies for AR have been proposed, including annulus-prosthesis-size mismatch and insufficient sealing in the setting of heavily calcified cusps. While paravalvular AR has become rare with current surgical techniques of
We enrolled consecutive patients who had undergone TAVI at our institution and presented for regular follow-up visits. Patients underwent CMR if they had no contraindication such as an implanted pacemaker, the examination was logistically possible and the patient agreed to the additional diagnostic procedure but were otherwise not selected. All patients provided written informed consent, and the institutional review board approved the study. The decision for TAVI was made in accordance with current guidelines and after discussion and consensus within a multidisciplinary Heart Team consisting of cardiologists and cardiac surgeons. The TAVI procedure was performed with the balloon-expandable
Orwat S, et al. Heart 2014;100:1933–1938. doi:10.1136/heartjnl-2014-305665
1933
Downloaded from http://heart.bmj.com/ on March 10, 2015 - Published by group.bmj.com
Valvular heart disease Edwards-SAPIEN or SAPIEN XT valve prosthesis (Edwards Lifesciences, Irvine, California, USA), which was available at this time in 23 and 26 mm sizes. Preprocedural annulus dimension was evaluated in all patients by ECG-gated CT and transesophageal echocardiography (TEE). Additional balloon sizing (angiography during balloon valvuloplasty) was performed in the case of uncertainty about the appropriate valve size. All procedures were performed under general anaesthesia and echocardiography guidance by TEE. Transfemoral access was used in 52 patients while a transapical access route was chosen in 13 patients because of poor vascular access. At the end of the TAVI procedure, the degree of postprocedural AR was evaluated angiographically and by TEE after final device deployment and removal of the catheter and the guidewire. After hospital discharge, clinical and TTE follow-up was obtained in all patients at 1–3 months, 6 months, 1 year and then annually. At one of these follow-up visits, patients had CMR and TTE generally within 24 h of each other.
Echocardiographic assessment All echocardiograms were performed by one of two experienced echocardiographers (SO and AK) using a commercially available echocardiographic machine (Vivid E9 System, General Electric, Milwaukee, Wisconsin, USA) according to a standardised local protocol. Loops were recorded in accordance with published recommendations with subjects in the left lateral position.16 17
All recordings were stored digitally for offline analysis. The AR severity was graded according to the recommendations of the European Association of Echocardiography18 and the VARC criteria9 19 with a special focus on semiquantitative parameters like diastolic flow reversal in the descending aorta measured by pulse-wave Doppler and circumferential extent of prosthetic valve paravalvular regurgitation. Unfortunately due to limited acoustic windows, adequate echocardiographic quantification of RF was only possible in a minority of patients and has therefore not been included as part of the analysis. All Doppler measurements were evaluated as the average of at least three cycles in patients with sinus rhythm or more than five cycles in those with atrial fibrillation. For the detection of regurgitant jets, the parasternal long-axis and short-axis views, the apical long-axis view and the five-chamber view were used (figure 1). Similar to the approach for native aortic valvular regurgitation, an integrative approach was applied to grade the AR. The degree of AR was classified into one of four grades: absent, mild, moderate or severe. In the presence of multiple AR jets, the overall degree of both paraprosthetic and central components was estimated in accordance with the VARC recommendations.9 In addition, a prominent holodiastolic flow reversal in the descending aorta classified a patient to have a more than mild AR.20 This evaluation of AR was performed by an echocardiographer who did not attend to the TAVI procedure and who was blinded to the results of the CMR evaluation of AR.
Figure 1 Example of transthoracic echocardiography in a patient with an Edwards SAPIEN prosthesis. Aortic regurgitation was graded by colour Doppler-echocardiography and CW-Doppler as moderate in this example. 1934
Orwat S, et al. Heart 2014;100:1933–1938. doi:10.1136/heartjnl-2014-305665
Downloaded from http://heart.bmj.com/ on March 10, 2015 - Published by group.bmj.com
Valvular heart disease Magnetic resonance imaging All CMR examinations were performed in our radiology department on a 1.5-T MRI system (Achieva, Philips Healthcare, Best, the Netherlands) equipped with a standard five-element cardiac phased array coil for signal reception and a vector electrocardiograph for cardiac synchronisation. All scans were accomplished without sedation. The image acquisition and subsequent analysis was carried out according to current guidelines.21 For cine imaging, a single-slice two-dimensional (2D) balanced steady-state free precession (SSFP) sequence in breath-hold technique and with retrospective ECG triggering was used. Imaging parameters were chosen as follows: echo time (TE) and repetition time (TR) were set to shortest resulting in an average TR of around 4 ms and a TE of 2 ms slightly varying with slice orientation, typically 25 phases per cardiac cycle and with a reconstructed in-plane resolution of 1 mm. The slice thickness usually was in the range of 6–8 mm. The typical temporal resolution of the cine b-SSFP sequences was 30–40 ms depending on the heart rate. The slice for the through-plane phase-contrast flow imaging was placed perpendicular to the direction of flow approximately 10 mm above the aortic prosthesis. This adequate distance to the prosthesis was kept, as phase-contrast acquisitions may be prone to magnetic field inhomogeneities. Sequences for orthogonal images in at least two views were used to ensure the image plane is truly perpendicular to the flow direction. To avoid aliasing, velocity encoding was individually adapted, starting at 200 cm/s, and if aliasing occurred, the
maximum velocity was increased by 50 cm/s steps until aliasing did not occur. Image acquisition is gated to the ECG signal and acquired over several cardiac cycles during a 10–20 s breathhold. Outlining the region of interest within the aortic lumen for each cardiac phase, the instantaneous flow volume (cm3/s) can be calculated and graphically displayed over the entire cardiac cycle (figure 2). The software calculates forward and reversed flow volumes, and from them the regurgitation fraction as follows: aortic regurgitation fraction (RF, %)=diastolic reversed flow volume×100/systolic forward flow volume. As previous comparisons in native valves with both modalities suggest, AR severity was classified with RF below 10% as absent/minimal, 10–20% as mild, 20–40% as moderate and greater than 40% as being severe (table 1).13 14 22–24
Statistical analysis Values are presented as mean and SD or median and IQR (25th and 75th centile), depending on variable distribution. Categorical variables are presented as frequencies and percentages. Comparisons between subgroups were performed by unpaired t test, Mann–Whitney U test or χ2 test as appropriate. For all analyses, a two-tailed p
