Incremental Value of Right Ventricular Free-Wall Strain in Ventricular Functional Mitral Regurgitation: Insights from a Multicenter Study.

BACKGROUND: Ventricular functional mitral regurgitation (VFMR) is a heterogeneous disease with widely variable outcomes, yet current risk stratification relies predominantly on left ventricular (LV) indices. This study aims to evaluate the incremental value of right ventricular free-wall longitudinal strain (RVfwLS) beyond conventional LV parameters and LV longitudinal strain (LVLS) in an unselected VFMR population. METHODS: This multicenter retrospective cohort included consecutive patients with moderately severe or greater VFMR diagnosed between 2010 and 2022. Right ventricular free-wall longitudinal strain and apical 4-chamber LVLS (A4C-LVLS) were quantified using automated software. The primary end point was cardiovascular death or death equivalent (LV assist device implantation or heart transplantation) during the longest available follow-up. Optimal cutoff for RVfwLS was derived from regression tree analysis and maximal selective rank statistics. Incremental prognostic value was assessed using likelihood ratio tests comparing nested models. RESULTS: Among the 487 patients included, 156 (32%) patients experienced the primary end point over a median follow-up of 2.6 (interquartle range, 0.85.9) years. Compared with event-free patients, those with events had larger LV volumes, but lower LV ejection fraction, A4C-LVLS, RV fractional area change (RVFAC), and RVfwLS (all P ≤ .005). Right ventricular free-wall longitudinal strain was independently associated with the primary end point on top of conventional LV indices, A4C-LVLS, and RVFAC (all P ≤ .047). Patients with A4C-LVLS < 8.7% and RVfwLS < 14% exhibited markedly worse 6-year event-free survival (48%) than those with higher biventricular strain (A4C-LVLS ≥ 8.7% and RVfwLS ≥ 14%; 72%; P < .001). Moreover, RVfwLS provided incremental prognostic value beyond A4C-LVLS, conventional LV indices, and RVFAC (all P ≤ .046). CONCLUSIONS: Right ventricular free-wall longitudinal strain is a robust determinant of adverse outcomes beyond conventional LV indices and A4C-LVLS in VFMR. A cutoff near 14% reliably identified the highest-risk subgroup. These results might support incorporating RVfwLS into routine evaluation to improve risk stratification in VFMR.