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Mitral Valve Prolapse and Sudden Cardiac Death
Study Questions:
What is the relationship between mitral valve prolapse (MVP) and sudden cardiac death (SCD)?
Methods:
Two cohorts were examined: 1) patients who suffered SCD, and 2) living patients with MVP. For the former, a cardiac registry of 650 young adults (≤40 years of age) who suffered SCD was reviewed (the registry was comprised of collected and preserved hearts of SCD victims from the Veneto region of northeastern Italy from 1982 through 2013), and cases in which MVP was the only cause of SCD were re-examined. Hearts from 15 age- and sex-matched patients who died suddenly from noncardiac causes served as controls. For the latter, 30 patients referred during 2010 through 2013 for MVP with complex ventricular arrhythmias underwent a study protocol including contrast-enhanced cardiac magnetic resonance (CMR). A group of 14 patients with MVP, but without complex ventricular arrhythmias served as controls.
Results:
The autopsy registry included 43 patients with MVP (26 women, age range 19–40 [median 32] years), representing 7% of all cases of SCD and 13% of all women in the registry. Among 12 with an available electrocardiogram, 10 (83%) had had inverted inferior T waves, and all had ventricular arrhythmias of right bundle branch block morphology. MVP was bileaflet in 70%. Left ventricular (LV) fibrosis was detected histologically at the level of papillary muscles in all and in the inferobasal wall in 88%. Among 30 living patients with complex ventricular arrhythmias (either right bundle branch block morphology or polymorphic; 22 women, age range 28–43 [median 41] years), 70% had bileaflet MVP. There was late enhancement on CMR in 29 (93%) versus 14% of controls (p < 0.001), localized at the papillary muscles in 25 (83%), or in the inferobasal wall in 22 (73%).
Conclusions:
The authors conclude that MVP is an underestimated cause of arrhythmic SCD, mostly in young adult women. Fibrosis of papillary muscles and the inferobasal LV wall, suggesting myocardium stretched by the prolapsing leaflet, is the structural hallmark and correlates with the origin of ventricular arrhythmias. CMR may help to identify this concealed substrate for risk stratification.
Perspective:
As presented, this study suggests that MVP is a mortal disease, associated with SCD that presumably is mediated by lethal arrhythmias. The problem is that clinical experience, at least in the United States, does not seem to support this. Data for the study come from the Veneto region of northeastern Italy, the same origin data that suggest a high risk for SCD in unscreened athletes. It is unclear whether residents of the Veneto region of Italy, owing to genetic or environmental factors, might face a higher risk of SCD (among athletes, and now among patients with MVP) than do their counterparts in other world regions. It is not clear that these data should lead to a worldwide change in the management of most patients with MVP.
Keywords: Arrhythmias, Cardiac, Autopsy, Bundle-Branch Block, Death, Sudden, Cardiac, Electrocardiography, Heart Conduction System, Heart Valve Diseases, Magnetic Resonance Imaging, Mitral Valve Prolapse, Papillary Muscles
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