Prolapse of the posterior leaflet of the mitral valve associated with secundum atrial septal defect.

The association of prolapse of the posterior leaflet of the mitral valve with secundum atrial septal defect has recently been reported but the prevalence and features of this association have not been defined. Analysis of left ventricular cineangiograms in 54 patients have secundum atrial septal defect revealed evidence of prolapse of the posterior leaflet of the mitral valve in 20 (37 percent). In 11 patients (20 percent) there was clinical evidence of a mitral valve lesion (pansystolic murmur in 9 patients and mid-systolic click in 2 patients, 1 of whom also had a late systolic murmur); the remaining 9 patients had no auscultatory evidence of a mitral valve lesion. Thus, the incidence of clinically silent prolapse in association with secundum atrial septal defect was 17 percent (9 of 54 patients). Analysis of the angiographic findings revealed that the prolapse was triscalloped in 4 patients, biscalloped in 11 and uniscalloped in 5. Mitral regurgitation was present in 12, including the 11 patients with clinical signs of a mitral lesion. Three patients with moderate or severe mitral regurgitation had triscalloped prolapse. The association of prolapse of the posterior leaflet of the mitral valve with secundum atrial septal defect is common and may be present in the absence of any clinical evidence of a mitral valve lesion.