Abstract 4370029: Imaging Markers of Myocardial Fibrosis in Mitral Valve Prolapse Across Stages of Mitral Regurgitation Severity

Background: Mitral valve prolapse (MVP) is associated with mitral regurgitation (MR), which can lead to adverse cardiac remodelling due to volume overload. In addition, mechanical stress from the prolapsing mitral valve may also induce replacement fibrosis. However, the type and extent of myocardial fibrosis across different MR severities remain poorly defined. Aim: To assess cardiovascular magnetic resonance (CMR) markers of myocardial fibrosis, including late gadolinium enhancement (LGE), indexed extracellular volume fraction (iECV), native T1, and native T2, in MVP patients stratified by MR severity. Methods: Patients with MVP undergoing 1.5T CMR at Karolinska University Hospital between February 2021–April 2025 were included. Imaging was performed to assess mitral annular disjunction, rule out primary cardiomyopathy, or as part of an ongoing CMR study involving MVP patients undergoing mitral valve surgery. Patients were excluded if they had ischemic heart disease, rheumatic mitral valve disease, mitral stenosis, previous mitral valve procedures, endocarditis or signs of primary cardiomyopathy. MR severity was defined by regurgitation fraction (RF) measured by CMR as mild (RF < 20%), moderate (RF 20–39%), and severe (RF ≥ 40%). Native T1 and T2 maps were acquired at rest, and post-contrast T1 maps was used to derive ECV(%) maps. iECV was calculated by multiplying ECV% by left ventricular (LV) end-diastolic myocardial volume indexed to body surface area. Replacement fibrosis was assessed by LGE. Ordinal logistic regression was adjusted for age, sex, hypertension, and diabetes. Results: A total of 127 patients with MVP were included. Of these, 32 (25%) had mild MR, 57 (45%) moderate MR and 38 (30%) severe MR. Characteristics associated with increasing MR were older age, male sex, atrial fibrillation, pulmonary hypertension, higher LVEF, and LV dilatation. iECV, native T1 and LGE increased progressively with MR severity (ORs 1.43, 95% CI: 1.23-1.65; 1.02, 95% CI: 1.01-1.03 and 2.16, 95% CI 1.05-4.39, respectively) (Figures 1, 2 and 3). No significant differences were observed in native T2 between groups. Conclusion: Greater MR severity in patients with MVP was associated with more extensive myocardial abnormalities, including both diffuse and replacement fibrosis. Future studies are needed to determine whether CMR can guide optimal timing of mitral valve surgery to prevent irreversible remodelling and improve clinical outcomes.