Association of prolapse of posterior cusp of mitral valve and atrial septal defect.

Eleven patients with fossa ovalis atrial septal defects and prolapse of the posterior cusp of the mitral valve are described. Six patients had clinical evidence of mitral regurgitation, and in 2 others the electrocardiogram was unusual for uncomplicated fossa ovalis atrial septal defects. The varied appearance of the prolapsed cusp was shown by left ventricular angiography. The principal significance of this association is in its differentiation from atrioventricular defects.