Clinical, echocardiographic, and biomechanical differences in mitral valve prolapse affecting one or both leaflets.

Mitral valve prolapse (MVP) is the most common cause of severe mitral regurgitation necessitating surgical correction. Unileaflet prolapse (ULP), usually involving the posterior leaflet, is more common than bileaflet prolapse (BLP), which is more difficult to repair. Little is known about clinical, echocardiographic, and biomechanical differences between ULP and BLP. In this study, biomechanical testing was performed on mitral valve leaflets and chordae obtained at operation for severe mitral regurgitation. Preoperative clinical characteristics and echocardiographic measurements were obtained on surgical patients (ULP = 88, BLP = 37). Men outnumbered women by a factor of 4:1 in ULP, and by 3:1 in BLP. Patients with BLP were younger (53.2 +/- 1.7 vs 59.5 +/- 1.1 years) than those with ULP, and this difference was greater in women (48.9 +/- 2.5 vs 62.9 +/- 2.2 years). BLP patients were less likely to be hypertensive, and more likely to undergo valve replacement rather than repair. Echocardiography showed that BLP leaflets were longer and thicker than ULP leaflets. The severity of mitral regurgitation was similar in both groups, although ULP patients had a much higher incidence of flail leaflets (45% vs 5% in BLP). Mechanical strength of chordae was greater in BLP than in ULP, although leaflet strength was similar. The increased chordal strength in BLP may be responsible for less flail. In patients with MVP and severe mitral regurgitation requiring surgery, ULP and BLP are distinct entities with substantial differences in the population affected, in echocardiographic manifestations including prevalence of flail, in chordal mechanics, and in the likelihood of surgical repair.