Abnormal chordal insertion: a cause of mitral valve prolapse.

Although the morphology of mitral valve prolapse (MVP) has been described, abnormalities of chordal arrangement and insertion have not been emphasized. We retrospectively reviewed 23 surgically-excised MVP and 10 control mitral valves removed at necropsy. Two-dimensional echocardiograms (2DE) were available in 10 MVP and in six additional controls. 2DE accurately assessed the length of anterior leaflet (AL) and posterior leaflet (PL) of the mitral valve (3.2 +/- 0.7 cm and 2.2 +/- 0.6 cm, respectively) as compared to morphologic measurements (3.0 +/- 0.4 cm and 2.1 +/- 0.4 cm, respectively). However, annular diameter as assessed by echocardiography was significantly less (4.6 +/- 0.7 cm) than that derived by morphologic measurements of annular circumference (AC) (5.3 +/- 0.7 cm). The AL and PL lengths and the mitral anuli were significantly larger in patients with MVP as compared to controls (p less than 0.01) when assessed both by 2DE and by morphology. The ratio of the maximum distance of chordal separation/AC was 0.11 +/- 0.04 in MVP and 0.13 +/- 0.02 in controls (p less than 0.05). Chordal divisions were increased in MVP (4.2) compared to controls (3.1, p less than 0.01). The most striking morphologic feature of MVP was abnormal chordal insertion and a random, unpredictable pattern of chordal distribution. We postulate that abnormal chordal architecture may be responsible for unequal stress on the valve leaflets and may thus lead to MVP.