The natural history of patients (pts) undergoing surgical repair of ostium primum atrial septal defects (ASD-1) in adulthood remains unclear. We followed 33 pts who underwent surgical correction of ASD-l at our institution at ages 20–73 years (mean=42), 12 of these patients were over the age of 50 at the time of surgery. Moderate preoperative exercise incapacity (NYHA Class >2) was present in 4 pts, and 6 were in atrial fibrillation. Preoperative mean pulmonary artery pressure >25mmHg, pulmonary vascular resistance >4 Wood units, or moderate-severe mitral regurgitation was present in 8, 4, and 5 pts, respectively, Autologous pericardium was used to patch the ASD-l in 30 pts (91 %). Mitral valvuloplasty, consisting of cleft repair (n=10) and mitral valve replacement (n=2), were performed selectively. At a mean follow-up of 5.3 years (1 month-18.2 years), all 28 surviving pts are free of exercise limitation (NYHA Class 1). Late post-operative deaths have occurred in 5 pts (15%); related to myocardial infarction, stroke, hepatic failure, renal failure, or sepsis. Reoperation was required in 2 pts (6%); for a residual ASD-1 (n=1). and severe mitral regurgitation (n=1), both within the first postoperative year. The presence of advanced age at operation, symptoms, atrial arrhythmias, mitral regurgitation, or moderately increased pulmonary vascular resistance did not predict late postoperative mortality, complications or functional capacity.ConclusionASD-1 can be repaired in adult pts with the expectation of excellent long-term results, independent of age at operation and preoperative mitral valve function; and despite the presence of atrial fibrillation, or moderately elevated pulmonary vascular resistance.