Longitudinal trajectories of secondary mitral regurgitation in non-ischemic dilated cardiomyopathy

Background: In non-ischemic dilated cardiomyopathy (NICM), the severity of secondary mitral regurgitation (SMR) is dynamic, depending on loading conditions and the effect of guideline-directed medical therapy (GDMT). However, the longitudinal trajectories of SMR and their prognostic implications remain insufficiently explored. We aimed to define the long-term trajectories of SMR and their prognostic impact in NICM. Methods: We retrospectively analyzed 764 NICM patients who underwent serial echocardiographic evaluations over a median follow-up of 9 (4-15) years. The longitudinal trajectories of SMR were identified using a latent class mixed model. Phenotypic characteristics and cardiovascular outcomes (all-cause death, heart transplant, left ventricular assist device implantation - D/HT/LVAD) associated with SMR trajectories were investigated. Results: SMR trajectories identified for patients with baseline no-mild SMR (n=440) were: no progression (76.2%), mild worsening (10.2%), and severe worsening (13.6%). In patients with baseline moderate-severe SMR (n=324), trajectories included persistent moderate-severe SMR (24%), mild improvement (8%), and strong improvement (68%). Smaller left atrium was associated with both mild and strong SMR improvement, while absence of left bundle branch block and New York Heart Association functional class