The natural history of small atrial septal defects; long-term follow-up with serial heart catheterizations.

Thirty-nine patients with a small ASD of the secundum type were followed clinically for 5 to 21 years (mean 11.6 years); no evidence of deterioration was found. In 26 of these cases recatheterization was carried out with a mean follow-up period of 9.8 years. No significant changes were found in most patients; in four patients, however, the left-to-right shunt had increased significantly. Our recommendations are that we will continue to advise surgery in patients with large ASD's, whereas we still do not recommend surgery in patients with small ASD's; the latter patients should be followed for longer periods to ensure that no deterioration occurs. The decision as to whether an ASD should be regarded as large or small in our opinion not only should be based on a chosen limit of pulmonary-to-systemic flow ratio, but clinical factors such as diastolic flow murmurs, ECG changes, the heart size, and the pulmonary vascular markings should also be taken into consideration.