The incidence of spontaneous closure of uncomplicated defects of the oval fossa was determined in cohort of 498 children. Surgical repair was accomplished in 428 at a median age of 4.5 years. Of the 70 who did not undergo surgery, 20 showed spontaneous closure or a decrease in size of the defect. The defect was unchanged in the other 50. The age at diagnosis, pulmonary-to-systemic flow ratio and size of the defect were not statistically significantly different in the changed and unchanged groups, and there was no difference in prevalence of symptoms, the triad of systolic and diastolic murmurs and abnormal splitting of the second sound, or of right ventricular enlargement by echocardiography. The rate of spontaneous diminution in size or actual closure of a defect in this series was 4%, and no clinical predictor of change in the size of a defect was identified. Thus, delay in repair of a large flow atrial septal defect in the hope of spontaneous closure is not justified, whether or not symptoms are present.
