IMPORTANCE - Malignant arrhythmic mitral valve prolapse (MVP) phenotype poses a substantial risk of sudden cardiac death (SCD), and an estimated 26 000 individuals in the United States are at risk of SCD per year. Thus, identifying risk-stratification strategies for SCD is imperative.

OBSERVATIONS - Patients with MVP have a heterogenous clinical spectrum, ranging from a benign course to a devastating complication such as SCD. Some of the high-risk markers of MVP, which are identified electrocardiographically, include inverted or biphasic T waves, QT dispersion, QT prolongation, and premature ventricular contractions originating from the left ventricular outflow tract and papillary muscles. Morphofunctional characteristics of SCD are leaflet thickness of 5 mm or greater, mitral annulus disjunction, paradoxical systolic increase of the mitral annulus diameter, increased tissue Doppler velocity of the mitral annulus, and higher mechanical dispersion on echocardiography and fibrosis identified by late gadolinium enhancement on cardiac magnetic resonance imaging.

CONCLUSIONS AND RELEVANCE - Findings from this review suggest that SCD can occur earlier in the course of MVP from complex arrhythmias that are triggered by the repeated tugging and traction of the chordopapillary muscle unit and basal mid-myocardium, even before macrofibrosis can be identified in these regions by late gadolinium enhancement on cardiac magnetic resonance imaging. Some of the newer markers identified by speckle-tracking Doppler, such as mechanical dispersion, myocardial work index, and postsystolic shortening, need further validation in a larger population.