Myocardial Fibrosis in Patients With Primary Mitral Regurgitation With and Without Prolapse

Background: Recent studies reported left ventricular (LV) fibrosis in patients with primary mitral regurgitation (MR) thought to be principally due to mitral valve prolapse (MVP). Objectives: This study sought to evaluate the prevalence, characteristics, and prognostic implications of LV fibrosis in a large cohort of primary MR patients with and without MVP using cardiovascular magnetic resonance (CMR). Methods: Patients referred for contrast CMR assessment of chronic primary MR were enrolled and underwent comprehensive assessment of cardiac remodeling, severity of MR, and LV replacement fibrosis. Primary MR patients were stratified into: an MVP group if there was >2 mm mitral leaflet displacement on cine-CMR, or a non-MVP group. Patients were followed for arrhythmic events (sudden cardiac death, aborted sudden cardiac arrest, and sustained or inducible ventricular arrhythmia). Results: A total of 356 primary MR patients (177 MVP and 179 non-MVP) were enrolled. LV fibrosis was more prevalent in the MVP group than the non-MVP group (36.7% vs. 6.7%; p < 0.001). The presence of MVP had the strongest association (odds ratio: 6.82; p < 0.001) with LV fibrosis even after adjustment for clinical variables, measures of cardiac remodeling, and MR severity. During follow-up (median 1,354 days), MVP patients with LV fibrosis had the highest event rate for arrhythmic events. Conclusions: In primary MR patients, LV fibrosis is more prevalent in MVP than non-MVP, suggesting a unique pathophysiology beyond volume overload in MVP. LV fibrosis in primary MR may represent a risk marker of arrhythmic events.