Clinical Impact of the Volumetric Quantification of Ventricular Secondary Mitral Regurgitation by Three-dimensional Echocardiography

Background: The assessment of ventricular secondary mitral regurgitation (v-SMR) severity through effective regurgitant orifice area (EROA) and regurgitant volume (RegVol) calculations using the proximal isovelocity surface area (PISA) method and the two-dimensional echocardiography volumetric method (2DEVM) is prone to underestimation. Accordingly, we sought to investigate the accuracy of the three-dimensional echocardiography volumetric method (3DEVM) and its association with outcomes in v-SMR patients. Methods: We included 229 patients (70 ± 13 years, 74% men) with v-SMR. We compared EROA and RegVol calculated by the 3DEVM, 2DEVM, and PISA methods. The end point was a composite of heart failure hospitalization and death for any cause. Results: After a mean follow-up of 20 ±11 months, 98 patients (43%) reached the end point. Regurgitant volume and EROA calculated by 3DEVM were larger than those calculated by 2DEVM and PISA. Using receiver operating characteristic curve analysis, both EROA (area under the curve, 0.75; 95% CI, 0.68-0.81; P = .008) and RegVol (AUC, 0.75; 95% CI, 0.68-0.82; P = .02) measured by 3DEVM showed the highest association with the outcome at 2 years compared to PISA and 2DEVM (P < .05 for all). Kaplan-Meier analysis demonstrated a significantly higher rate of events in patients with EROA ≥ 0.3 cm2 (cumulative survival at 2 years: 28% ± 7% vs 32% ± 10% vs 30% ± 11%) and RegVol ≥ 45 mL (cumulative survival at 2 years: 21% ± 7% vs 24% ± 13% vs 22% ± 10%) by 3DEVM compared to those by PISA and 2DEVM, respectively. In Cox multivariable analysis, 3DEVM EROA remained independently associated with the end point (hazard ratio, 1.02, 95% CI, 1.00-1.05; P = .02). The model including EROA by 3DEVM provided significant incremental value to predict the combined end point compared to those using 2DEVM (net reclassification index = 0.51, P = .003; integrated discrimination index = 0.04, P = .014) and PISA (net reclassification index = 0.80, P < .001; integrated discrimination index = 0.06, P < .001). Conclusions: Effective regurgitant orifice area and RegVol calculated by 3DEVM were independently associated with the end point, improving the risk stratification of patients with v-SMR compared to the 2DEVM and PISA methods.