The spectrum of anomalies of aortopulmonary septation.

Embryologically related defects resulting from abnormal septation of the aortopulmonary trunk in 13 patients were reviewed and grouped according to a new classification system. Seven patients (54 percent) had typical aortopulmonary septal defects or windows (Type I), three (23 percent) had a more cephalad defect between the ascending aorta and the origin of the right pulmonary artery (Type II), and three (23 percent) had anomalous origin of the right pulmonary artery from the ascending aorta (Type III). Type I defects are caused by incomplete septation of the aortopulmonary trunk; Type II and III defects result from unequal partitioning of the aortopulmonary trunk by the conotruncal ridges. Three of six patients survived correction of Type I defects; both patients having correlation of Type II defects and all three patients with Type III defects survived and remain well 2 to 216 months (mean 61 months) postoperatively. The recommended technique for Type I and II defects is transaortic closure of the defect by prosthetic patch with the aid of cardiopulmonary bypass, supplemented by profound hypothermia (20 degrees C.), and circulatory arrest for improved exposure in selected cases. For Type III defects, division of the anomalous connection plus direct implantation of the right pulmonary artery into the main pulmonary artery is the preferred approach.