Background: Mitral valve prolapse (MVP), particularly bileaflet prolapse with mitral annular disjunction (MAD), has been associated with an increased risk of sudden cardiac death. Despite various studies being conducted over the years, the incidence of sudden cardiac death, however, is still not known.

Method: In this retrospective cohort study, we identified all patients from 2002 to 2017 followed in the UCLA Health System with echocardiographic evidence of MVP or mitral valve leaflet bowing. Patients with other congenital heart diseases, pulmonary disease, cirrhosis, or circulatory shock at time of MVP diagnosis, or history of ventricular arrhythmias prior to MVP were excluded. Up to 5 controls were matched per MVP patient, based on age, Charlson comorbidity index, and presence of echocardiogram ordered within 6 months of qualifying case. Mortality data was obtained from the National Death Index for all patients through 2017. The primary endpoint was ventricular fibrillation, or sudden death from arrhythmic cause. Competing risks analysis was used to compare the risk of primary endpoint in cases versus control.

Results: We identified 636 patients with mitral valve bowing or prolapse (88 with bowing only, 321 with single leaflet prolapse, 227 with bileaflet prolapse, age 58 ± 19 years, 45% male), and 2859 control patients (age 59 ± 19 years, 43% male). Median follow-up was 1671 days. The primary endpoint was met in 2 (0.62%) cases of single leaflet prolapse, in 4 (1.76%) cases of bileaflet prolapse  and in 11 (0.38 %) controls (p = 0.02 between all case vs. control, p = 0.004 bileaflet prolapse vs. control). The incidence of the primary endpoint in cases was 0.08% per patient year for single leaflet prolapse, 0.13% per patient years for bileaflet prolapse and 0.1% per patient year in controls. The primary endpoint was met in 2 case patients after a mitral valve repair/replacement surgery

Conclusions: The risk of VF/Arrhythmic death in patients with mitral valve prolapse is low, but significantly higher than that of matched controls, particularly in patients with bileaflet prolapse. Mitral valve surgery may not negate the risk of SCD in these patients