Left Ventricular Fibrosis by Cardiac Magnetic Resonance Tissue Characterization in Chronic Mitral Regurgitation Patients

Background: Left ventricular remodeling in chronic mitral regurgitation (MR) encompasses two types of myocardial fibrosis: replacement fibrosis, identified by late gadolinium enhancement (LGE), and diffuse interstitial fibrosis, assessed by pre- and postcontrast T1 mapping techniques. These may explain irreversible LV dysfunction after MR correction. We aimed to assess the presence of myocardial fibrosis in patients with moderate and severe MR with no criteria for surgery versus mild MR controls. Methods: We enrolled 137 patients with chronic primary MR and 130 controls; all underwent cardiac magnetic resonance, and were followed up in a median of 2.9 years to assess mortality and the need for mitral valve replacement. Results: Patients in the study group displayed significantly higher degrees of LGE (28.4% vs 7.69%, p < 0.05), higher native T1 values (1167 +/- 58.5 versus 971 +/- 51.4 (p < 0.05)), and higher extracellular volumes compared to controls (32.3% +/- 3.5 versus 23.9 +/- 2.2, (p < 0.05)). The composite outcome occurred in 28 patients in the study group (20.4%), and significantly higher with LGE+ (78.5%). Replacement fibrosis (HR = 1.83, 95% CI, p < 0.01) and interstitial fibrosis (HR = 1.61, 95% CI, p < 0.01) were independent predictors for the composite outcome. Conclusions: Patients with moderate and severe MR with no criteria for surgery still exhibit a significant degree of both replacement and interstitial fibrosis, with prognostic implications.