DIAGNOSIS: atrial septal defect (ASD), as evidenced by the fixed split of the second heart sound over the pulmonic area (S2P) and the systolic murmur. The chest x-ray shows some prominence of the pulmonary segment in keeping with the fact that the patient has become symptomatic. A "bubble" echocardiogram confirmed the diagnosis, and showed that the patient had begun to develop a right-to-left shunt. Surgery is the treatment of choice. This disorder often first manifests itself in middle aged persons..