Natural history of atrial septal defect of secundum type in the middle-aged. Medical versus surgical therapy.

10 middle-aged patients with atrial septal defect of the secundum type (ASD II) were referred to surgery, but for several noncardiological reasons the operation was not performed. 5 patients were reexamined after an interval from 6 1/2 to 15 years. During the follow-up period only relatively minor changes in pulmonary arteriolar resistance had occurred and all patients were still acceptable candidates for surgical treatment. The other 5 patients died after a period of time ranging from 2 weeks to 16 1/2 years from conditions directly or indirectly related to the cardiac malformation. During the same period of time, 84 ASD II patients underwent surgery with a mortality rate of 8.3% after 74 months, including 2 hospital deaths. These results suggest that middle-aged patients with ASD II without obstructive pulmonary hypertension should be operated on without delay, but that in a significant number of cases, long-term conservative treatment is not associated with an increase in pulmonary arteriolar resistance.