In collaboration with Dr. Francesca Delling, we found that up to 2.3% of subjects with Mitral Valve Prolapse (MVP) experience SCD, but by convention SCD is rarely confirmed by autopsy. In a previous post-mortem study of persons <40 years of age, 7% of SCDs were caused by MVP; bileaflet involvement, mitral annular disjunction (MAD), and replacement fibrosis were common.

Through our comprehensive, county-wide, post-mortem study of all adult cases of presumed SCD (n = 603) in San Francisco County, 7 (1%) of presumed SCDs were due to MVP. Six additional MVPs were identified by review of echocardiograms, for a total prevalence of at least 2% among 603 presumed SCDs and 4% among 339 sudden arrhythmic deaths (SADs). 

MVP prevalence was at least 4% of SADs, but one-half were missed on autopsy. Monoleaflet MVP was often underdiagnosed post-mortem. Compared with young cases of SCD, lethal MVP in older cases of SCD did not consistently have bileaflet anatomy, replacement fibrosis, or MAD.