Qualitative and Quantitative Assessment of Atrial Functional Mitral Regurgitation: analysis from the REVEAL-AFMR registry.

Background: The prevalence, characteristics, and prognosis of atrial functional mitral regurgitation (AFMR) based on severity remain unclear. No studies have systematically evaluated quantitative thresholds, such as effective regurgitant orifice area (EROA) or regurgitant volume, in relation to outcomes in AFMR. This multicenter study aimed to clarify the clinical implications of both qualitative and quantitative assessments of AFMR severity.

Methods: In this first multicenter study across 26 centers, patients with at least moderate AFMR-defined by preserved left ventricular (LV) function, enlarged left atrium (LA), and absence of primary mitral valve changes-were retrospectively analyzed. AFMR severity was evaluated using a comprehensive approach, including EROA, regurgitant volume, and regurgitant fraction.

Results: Among 1,007 patients, 728 (72.3%) had moderate, 146 (14.5%) moderate-to-severe, and 133 (13.2%) severe AFMR. Age, sex, natriuretic peptide levels, and LV ejection fraction were similar across all groups. Patients with severe AFMR had longer atrial fibrillation history, worse heart failure symptoms, larger LV and LA, and more severe tricuspid regurgitation. AFMR severity was independently associated with a higher risk of death, heart failure hospitalization, and mitral valve intervention (HR 1.51, p=0.001 for moderate-to-severe, 2.80, p<0.001 for severe). Quantitative thresholds showed a significantly higher event risk with EROA ≥0.30, regurgitant volume ≥60 mL, and regurgitant fraction ≥50%.

Conclusions: Severe AFMR was common and linked to greater atrial fibrillation burden, cardiac structural issues, and an increased risk of adverse clinical events. Quantitative thresholds offer valuable guidance for clinical decision-making and treatment planning.