Incremental Prognostic Value of Regurgitant Fraction in Patients with Ventricular Secondary Mitral Regurgitation

Objectives: Quantifying ventricular secondary mitral regurgitation (MR) remains challenging, and the prognostic value of echocardiographic parameters is uncertain. This study aimed to assess the concordance of parameters of MR severity and determine the added value of regurgitant fraction (RF) in predicting outcomes. Methods and results: We retrospectively analysed 186 patients with ventricular secondary MR who underwent echocardiography with MR assessment, evaluating effective regurgitant orifice area (EROA), regurgitant volume (RegVol) and RF. The primary endpoint was a composite of all-cause death or heart failure hospitalisation. Quantitative parameters of MR severity were frequently discordant. Using the guideline-recommended cut-offs for EROA (≥40 mm2), RegVol (≥60 mL) and RF (≥50%), severe MR was present in 5.4%, 3.3%, and 29.5% of patients, respectively. Both RF ≥ 50% and EROA ≥ 40 mm2 were independently associated with clinical outcomes in multivariable Cox models. Combining RF and EROA provided incremental prognostic value over either parameter alone (p < 0.05). Kaplan–Meier curves showed that patients with EROA < 40 mm2 and RF ≥ 50% had similar outcomes to those with EROA ≥ 40 mm2 (p = 0.055), whereas patients with both EROA < 40 mm2 and RF < 50% had significantly better outcomes (p = 0.002). Conclusions: Substantial discordance between quantitative parameters of severe MR was observed in ventricular secondary MR. RF is a strong, underutilised marker of MR severity, reflecting haemodynamic burden beyond EROA and RegVol. Patients with EROA < 40 mm2 and RF > 50% had outcomes comparable to those who met the guideline-based threshold for severe MR, defined as EROA ≥ 40 mm2. Our results demonstrate that routine RF assessment may enhance risk stratification and enable identification of a high-risk subgroup of patients with EROA < 40 mm2.