Multiparametric Cardiac MRI Phenotyping of Arrhythmic Mitral Valve Prolapse: Ventricular Shape Analysis, Myocardial Deformation Imaging and Advanced Late Gadolinium Enhancement Characterisation

Background: Patients with arrhythmic mitral valve prolapse (A-MVP) are at increased risk of ventricular-fibrillation (VF)/sustained-ventricular-tachycardia (SVT) despite the absence of moderate–severe mitral regurgitation (MR) or left ventricular (LV) dysfunction. Given the low prevalence of A-MVP in the population, cohort studies fall short in phenotyping this condition. We therefore conducted a nested case–control study to investigate the relative contribution of potentially relevant features of A-MVP, i.e., heightened mechanical stretch of the papillary muscles (PMs), mitral annulus disjunction (MAD), myocardial fibrosis (MF) and LV geometric remodelling. Methods: We retrospectively age- and sex-matched 23 MVP patients presenting with VF/SVT (A-MVP; 51 ± 17 years, 52% male) with 69 MVP patients naïve to VF/SVT (nA-MVP; 50 ± 15 years, 49% male; ratio = 1:3) who underwent CMR. MR was mild or less in all patients. Feature-tracking of short-axis cine images (24 sectors per slice) quantified peak and time-to-peak circumferential and radial strains at PM insertion (Ins), adjacent (Adj), and remote (R) myocardium. Late-gadolinium-enhancement short-axis images were analysed by an in-house MATLAB-based software using a full-width-half-maximum algorithm to quantify MF and its microstructure. MAD was assessed on three-chamber cine images. LV shape remodelling at end-diastole (ED) and end-systole (ES) was evaluated from 3D meshes reconstructed from cine segmentations, deriving global descriptors and statistical shape modes using principal-component analysis. Results: LV volumes, mass and bi-atrial size were similar between groups (P > 0.05), although LVEF was slightly lower in A-MVP (57 ± 7% vs 60 ± 7%, P = 0.049). Peak and time-to-peak radial and circumferential strains in Ins-, Adj- and R-regions were comparable between groups (P>0.10). MAD prevalence did not differ (65% vs 46%, P = 0.117). MF prevalence and extent were greater in A-MVP (57% vs 32%, P=0.035 and 4.1 ± 2.7 vs 2.4 ± 2.4% of LV mass, P=0.015, respectively). LGE microstructure revealed larger scar-core volume, greater core/grey-zone interface surface, and higher entropy in A-MVP (P < 0.05). LV shape analysis demonstrated outward remodelling at ED with greater apical diameters (~+4 mm), higher sphericity (0.50 vs 0.42, P = 0.010). At ES, enlargement persisted with wider basal and mid-ventricular epicardial diameters (~+5 mm). Conclusions: Myocardial fibrosis - rather than MAD or myocardial deformation abnormalities - is a key feature of A-MVP, characterised by larger scar-core burden and greater microstructural heterogeneity. In addition, subtle yet consistent alterations in LV geometry throughout the cardiac cycle suggest early maladaptive remodelling in the arrhythmogenic MVP phenotype. Integrated assessment of tissue characterisation and LV shape may enhance future risk-stratification strategies in MVP.