Extracellular Volume in Primary Mitral Regurgitation

OBJECTIVES This study used cardiovascular magnetic resonance (CMR) to evaluate whether elevated extracellular volume (ECV) was associated with mitral valve prolapse (MVP) or if elevated ECV was a consequence of remodeling independent of primary mitral regurgitation (MR) etiology. BACKGROUND Replacement fibrosis in primary MR is more prevalent in MVP; however, data on ECV as a surrogate for diffuse interstitial fibrosis in primary MR are limited. METHODS Patients with chronic primary MR underwent comprehensive CMR phenotyping and were stratified into an MVP cohort (>2 mm leaflet displacement on a 3-chamber cine CMR) and a non-MVP cohort. Factors associated with ECV and replacement fibrosis were assessed. The association of ECV and symptoms related to MR and clinical events (mitral surgery and cardiovascular death) was ascertained. RESULTS A total of 424 patients with primary MR (229 with MVP and 195 non-MVP) were enrolled. Replacement fibrosis was more prevalent in the MVP cohort (34.1% vs. 6.7%; p < 0.001), with bi-leaflet MVP having the strongest association with replacement fibrosis (odds ratio: 10.5; p < 0.001). ECV increased with MR severity in a similar fashion for both MVP and non-MVP cohorts and was associated with MR severity but not MVP on multivariable analysis. Elevated ECV was independently associated with symptoms related to MR and clinical events. CONCLUSIONS Although replacement fibrosis was more prevalent in MVP, diffuse interstitial fibrosis as inferred by ECV was associated with MR severity, regardless of primary MR etiology. ECV was independently associated with symptoms related to MR and clinical events. (DeBakey Cardiovascular Magnetic Resonance Study [DEBAKEY-CMR]; NCT04281823)