Abstract 16798: Evidence of Abnormal T1 Mapping in Arrhythmic Mitral Valve Prolapse Without Significant Mitral Regurgitation

Abstract

Background: Prior cardiac magnetic resonance (CMR) studies have reported abnormal T1 mapping, reflective of diffuse myocardial fibrosis, in patients with mitral valve prolapse (MVP) and ventricular arrhythmias. However, T1 mapping was derived from conventional Look-Locker sequences and/or obtained in selected MVP patients with severe mitral regurgitation (MR) and a clinical indication for CMR. Hypothesis: We hypothesize that extracellular volume (ECV) fraction, a marker of diffuse fibrosis derived from research-based, MOLLI T1 mapping sequences, is increased in MVP subjects with ventricular arrhythmias, even in the absence of significant MR. Methods: We performed CMRs in 10 consecutive, randomly selected MVP patients identified through our echocardiographic database, age/gender matched to 10 controls free of significant cardiac disease. All 10 MVPs underwent ambulatory EKG monitoring. CMR images were acquired using a GE 3.0T Discovery MR750w scanner. Global ECV fraction was calculated using pre- and 10 minutes post-contrast T1 times after administration of 0.1 mmol/kg of gadobutrol (Gadavist). Late gadolinium enhancement (LGE) was also obtained. MR fraction was quantified by velocity encoded CMR. Mild MR was defined as MR fraction < 16%. Results: MVP patients had significantly higher ECV fraction compared to controls (mean ECV (%) 32 ± 4 vs 20 ± 6, p = 0.0002), with 5/10 demonstrating non-sustained VT on ambulatory EKG monitoring. The majority (9/10 or 90%) of MVPs had mild or no MR (MR fraction < 16%), and 1/10 or 10% had moderate MR (MR fraction 18%). Only one individual in the MVP group had late gadolinium enhancement (LGE) in the papillary muscles. Conclusion: MVP with ventricular arrhythmias is associated with increased global ECV reflective of diffuse myocardial fibrosis, even in the absence of significant MR or LGE. Our preliminary findings highlight for the first time a primary interstitial derangement in MVP. Larger studies are needed to understand the mechanisms and prognostic significance of primary diffuse fibrosis in MVP.