Optimal Quantification of Functional Mitral Regurgitation: Comparison of Volumetric and Proximal Isovelocity Surface Area Methods to Predict Outcome.

Background Effective orifice area (EOA) ≥0.2 cm2 or regurgitant volume (Rvol) ≥30 mL predicts prognostic significance in functional mitral regurgitation (FMR). Both volumetric and proximal isovelocity surface area (PISA) methods enable calculation of these metrics. To determine their clinical value, we compared EOA and Rvol derived by volumetric and PISA quantitation upon outcome of patients with FMR. Methods and Results We examined the outcome of patients with left ventricular ejection fraction <35% and moderate to severe FMR. All had a complete echocardiogram including EOA and Rvol by both standard PISA and volumetric quantitation using total stroke volume calculated by left ventricular end-diastolic volume×left ventricular ejection fraction and forward flow by Doppler method: EOA=Rvol/mitral regurgitation velocity time integral. Primary outcome was all-cause mortality or heart transplantation. We examined 177 patients: mean left ventricular ejection fraction 25.2% and 34.5% with ischemic cardiomyopathy. Echo measurements were greater by PISA than volumetric quantitation: EOA (0.18 versus 0.11 cm2), Rvol (24.7 versus 16.9 mL), and regurgitant fraction (61 versus 37 %) respectively (all P value <0.001). During 3.6±2.3 years' follow-up, patients with EOA ≥0.2 cm2 or Rvol ≥30 mL had a worse outcome than those with EOA <0.2 cm2 or Rvol <30 mL only by volumetric (log rank P=0.003 and 0.004) but not PISA quantitation (log rank P=0.984 and 0.544), respectively. Conclusions Volumetric and PISA methods yield different measurements of EOA and Rvol in FMR; volumetric values exhibit greater prognostic significance. The echo method of quantifying FMR may affect the management of this disorder.