Spontaneous closure of isolated secundum atrial septal defects in infants: an echocardiographic study.

The incidence and timing of spontaneous closure of isolated secundum atrial septal defects are unknown. Twenty-nine consecutive infants under 12 months of age with clinical evidence of significant left-to-right shunting through atrial septal defects were evaluated by M-mode and two-dimensional echocardiography (2DE). All had right ventricular hypertrophy by ECG. Right ventricular, right atrial, and left atrial areas were measured and right ventricular and left atrial dimensions were obtained in all patients. Spontaneous closure of the defect in four infants was suggested by normalization of clinical examination and ECG and was documented by 2DE and M-mode echocardiography at 15 to 31 months of age. All of the remaining patients, who had suitable 2DE echocardiograms and who did not spontaneously close their defects, had enlarged right ventricular and right atrial areas. Left atrial areas were normal in the four who closed spontaneously and were large in all but three who did not close. The mean diameter of the defect was similar for all patients. The 14% incidence reported here may underestimate the true incidence of spontaneous closure, since seven patients had surgical closure, all prior to 30 months of age, the oldest age at which spontaneous closure was documented. An atrial septal flap, found in all four patients who closed spontaneously but only in 4 of the 16 patients who did not close spontaneously, may contribute in some way to spontaneous closure. Since spontaneous closure may occur up to 30 months, it seems clear that surgical closure should not be performed before that age unless medical management has failed to control symptoms.