Determinants and Prognostic Impact of Left Atrial Reservoir Strain Improvement Following Mitral Transcatheter Edge-To-Edge Repair

Heart failure with functional mitral regurgitation (FMR) has poor prognosis, and mitral transcatheter edge-to-edge repair (M-TEER) is an effective treatment. However, patient responses are variable, highlighting the need for early markers of treatment success. Left atrial reservoir strain (LARS) reflects atrial compliance and chronic hemodynamic burden and may identify patients with reversible atrial dysfunction. We retrospectively analyzed 128 patients with FMR (median age 80 years, 37% female; 31% atrial subtype) undergoing M-TEER at Hiroshima University Hospital. LARS was measured at baseline and 1 month postprocedure, with improvement defined as ≥15% relative increase. Procedural success was high (98%), and LARS assessment showed excellent reproducibility. LARS improved in 33% of patients. Key predictors of early improvement were absence of persistent atrial fibrillation, lower baseline LARS, and better renal function. Procedural factors such as residual mitral regurgitation or transmitral gradient were not associated. Patients with LARS improvement showed greater reductions in pulmonary arterial wedge pressure, improved biventricular function, lower residual tricuspid regurgitation, and enhanced exercise capacity. During a median follow-up of 14 months, early LARS improvement was associated with significantly higher event-free survival. Multivariable analysis confirmed that LARS improvement independently predicted lower risk of all-cause death and heart failure hospitalization, beyond baseline LARS and conventional post-M-TEER risk factors. Continuous analysis of %ΔLARS further supported a dose-response relationship with outcomes. In summary, early LARS improvement reflects integrated atrial and cardiopulmonary reverse remodeling and is a strong independent predictor of short-term prognosis after M-TEER. Serial assessment of LARS shortly after M-TEER may serve as a practical tool for early risk stratification and therapeutic optimization across all FMR subtypes.