Paradox of disproportionate atrial functional mitral regurgitation and survival after transcatheter edge‐to‐edge repair

Abstract Aims This study aims to assess the applicability of the mitral regurgitation (MR) proportionality concept in patients with atrial functional mitral regurgitation (aFMR) treated with transcatheter edge‐to‐edge repair (M‐TEER). We hypothesized that patients with disproportionate MR (higher MR relative to left ventricular size) would exhibit different outcomes compared to those with proportionate MR, despite undergoing M‐TEER. Methods and results We retrospectively analysed 98 patients with aFMR from the EuroSMR registry who underwent M‐TEER between 2008 and 2019. Patients met criteria for aFMR (normal indexed left ventricular end‐diastolic volume LVEDV, preserved left ventricular ejection fraction LVEF ≥ 50% without regional wall motion abnormalities, and structurally normal mitral valves). We excluded patients with missing effective regurgitant orifice area (EROA) or LVEDV data. The primary endpoint was 2‐year mortality, with an EROA/LVEDV ratio employed to differentiate disproportionate from proportionate MR. Procedural success and baseline characteristics were analysed, and multivariate Cox proportional hazards models were used to identify mortality predictors. The mean patient age was 79 ± 7.3 years, with 68.8% female, and 79% had a history of atrial fibrillation. The mean EROA was 0.27 ± 0.14 cm 2 , and LVEDV was 95.6 ± 33.7 mL. Disproportionate MR was identified with an EROA/LVEDV ratio >0.339 cm 2 /100 mL. While procedural success was similar in both groups, disproportionate MR was associated with a numerically higher estimate of systolic pulmonary artery pressures (sPAP) and rates of NYHA ≥III and TR ≥ 3+. Disproportionate MR had a significant association with increased 2‐year mortality ( P < 0.001). The EROA/LVEDV ratio and tricuspid annular plane systolic excursion (TAPSE) were independent predictors of 2‐year mortality (EROA/LVEDV: HR: 1.35, P = 0.010; TAPSE: HR: 0.85, P = 0.020). Conclusions This analysis introduces the MR proportionality concept in aFMR patients and its potential prognostic value. Paradoxically, disproportionate MR in aFMR was linked to a 1.35‐fold increase in 2‐year mortality post‐M‐TEER, emphasizing the importance of accurate preprocedural FMR characterization. Our findings in patients with disproportionate MR indicate that a high degree of aFMR with high regurgitant volumes may lead to aggravated symptoms, which is a known contributor to increased mortality following M‐TEER. These results underline the need for further research into the pathophysiology of aFMR to inform potential preventative and therapeutic strategies, ensuring optimal patient outcomes.