CMR to Evaluate Aortic Regurgitation After TAVR
Is aortic regurgitation (AR) quantified on cardiac magnetic resonance (CMR) imaging more accurate than echocardiography for prognostic assessment after transcatheter aortic valve replacement (TAVR)?
A total of 135 patients from three centers underwent CMR a median of 40 days after TAVR (range 6-105) for assessment of left ventricular geometry and quantification of AR and were compared to transthoracic echocardiograms performed a median of 6 days (range 6-22) after TAVR. CMR studies were performed on 1.5 T scanners and phase contrast imaging was used to quantify forward and regurgitant volumes. Definitions of mild, moderate, and severe regurgitation were based on Valve Academic Research Consortium (VARC)-2 criteria. AR was quantified on echo as none/trace, mild, or moderate/severe based on an integrated multi-parametric approach. Clinical outcomes evaluated included mortality, hospitalization for heart failure, and need for valve reintervention.
There were 14.9% and 12.8% of patients who were found to have moderate or severe AR based on echocardiography and CMR, respectively. Thirty-one patients died over a median follow-up of 26 months. There were also 16 hospitalizations for heart failure and eight valve reinterventions. Regurgitant fraction by CMR was an independent predictor of death (hazard ratio 1.12 per 5%, p < 0.0001) and the composite of death and heart failure hospitalization (hazard ratio 1.17 per 5%, p < 0.0001) and led to risk reclassification beyond echocardiography (net reclassification index = 0.15 for both death and for the composite of death and heart failure hospitalization). Regurgitant fraction ≥30% was the optimal for identifying patients who experienced mortality within 2 years (c-statistic 0.678, sensitivity 39%, specificity 70%, p = 0.001) and the composite of mortality and heart failure hospitalization (c-statistic 0.679, sensitivity 39%, specificity 70%, p = 0.0001). Patients with ≥30% regurgitant fraction experienced higher mortality (35.1% vs. 14%, p = 0.03) and mortality or heart failure hospitalization (47.3% vs 15.2%, p = 0.0002).
CMR-quantified AR after TAVR predicted clinical outcomes beyond echocardiography.
This study adds to the rapidly growing body of literature supporting the use of CMR in the assessment of valvular disease. Given the well-established prognostic importance of AR in the post-TAVR setting, better tools for assessment of AR may have an important role in selecting patients for reintervention. This study is particularly important given the comparison with transthoracic echocardiography. However, the study did not use 3-D echocardiography, and a detailed assessment of whether particular quantitative echocardiographic parameters could have closed the gap compared to the somewhat subjective, integrated assessments used was not performed. Additional studies seeking to determine whether identifying patients for reintervention using CMR could improve outcomes are necessary.
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