Prolapse of the mitral valve in secundum atrial septal defect: a functional mechanism.

Prolapse of the mitral valve in patients with secundum atrial septal defect has been described angiographically and by two-dimensional echocardiography. It has been suggested that prolapse of the mitral valve in these patients is due to distortion of left ventricular shape and small left ventricular volume. To test this hypothesis 10 patients with unrepaired secundum atrial septal defect and 10 patients who had undergone repair of the defect were studied by two-dimensional echocardiography. The prevalence of mitral valve prolapse was 80% in the unrepaired group and 20% in the repaired group (P less than 0.01). Short axis of the left ventricle revealed septal bulging into the left ventricle, the end-diastolic ratio of minor to major axis being 0.71 in the unrepaired group and 0.93 in the repaired group (P less than 0.001). Systolic and diastolic cross-sectional areas were larger in the repaired group compared with the unrepaired group (P less than 0.05). Prolapse of the mitral valve in patients with secundum atrial septal defect may be related to the distorted left ventricular shape and small left ventricular volume.