Mild Expression of Mitral Valve Prolapse in the Framingham Offspring: Expanding the Phenotypic Spectrum

Background: Mitral valve (MV) prolapse (MVP) is a common disorder associated with mitral regurgitation, endocarditis, heart failure, and sudden death. Nondiagnostic morphologies have been described in the familial context and may represent early expression of MVP in those genetically predisposed. The aim of this study was to explore the spectrum of MVP abnormalities in the community and compare their clinical and echocardiographic features. Methods: We measured annular diameter MV leaflet displacement, thickness, anterior and posterior leaflet projections onto the annulus, MV leaflet coaptation height (posterior MV leaflet projection/annular diameter), and MR jet height in 296 individuals of the Framingham Offspring Study with MVP (n = 77), the "abnormal anterior coaptation" (AAC) phenotype (n = 11) or "minimal systolic displacement" (MSD) (n = 57), and 151 age-matched and sex-matched referents with no MVP or its nondiagnostic forms. Results: AAC did not meet diagnostic displacement criteria but resembled MVP with regard to annular diameter and leaflet thickness (P > .05 for both). AAC was similar to posterior MVP with regard to posterior leaflet asymmetry and an anteriorly shifted coaptation (P = .91). Compared to patients with MSD and referents, patients with AAC had greater leaflet coaptation height, thickness, and annular diameter (P < .05 for all). MSD shared the posterior leaflet asymmetry with MVP, but the coaptation point was more posterior (coaptation height = 31% vs. 42%, P < .0001), as seen in referents. A higher proportion of patients with MVP had jet height >= 2 mm (mild or greater MR) compared with the other participants (44% vs. 16%, P < .0001). Conclusions: Nondiagnostic morphologies are observed in the community and share the common feature of posterior leaflet asymmetry with MVP. AAC and MSD may thus represent early expressions of MVP. Longitudinal studies are warranted to elucidate the natural history of these phenotypes.