The role of reduced left ventricular enddiastolic volume in the apparently high prevalence of mitral valve prolapse in atrial septal defect.

Twenty-three patients with ostium-secundum atrial septal defect (ASD) were studied in order to investigate the etiology of angiographic mitral valve prolapse associated with ostium-secundum ASD. 12 patients (52%) had angiograhic MVP. Ventricular volumes, ejection fraction, segmentary contractility and oxygen step-up were analyzed in all patients. Patients with MVP had smaller enddiastolic and stroke volumes (73 +/- 21.8 ml/m2 and 46.6 +/- 18 ml/beat/m2) than patients without MVP (106.6 +/- 22 ml/m2 and 78 +/- 11.3 ml/beat/m2) (P less than 0.01). Oxygen step-up was greater in patients with MVP (P less than 0.05). No consistent differences in ejection fraction and segmentary contractility were found. Our findings suggest that angiographic MVP associated with ostium-secundum ASD is a functional disorder due to reduced left ventricular enddiastolic volume secondary to the atrial shunt.