Absence of anatomic origin from heart of pulmonary arterial supply.

Among certain patients with cardiovascular malformations, a common phenomenon is a ventricular septal defect and absence of anatomic origin of the pulmonary arterial supply from the heart. In this situation, true pulmonary arteries may be present or absent. In the latter case, the pulmonary arterial supply comes through bronchial arteries. When true pulmonary arteries are present, the left and right pulmonary arteries either may be in continuity at their origins (confluence) or they may arise from separate sites (nonconfluence). When confluence is present, the two pulmonary arteries may arise either from an atretic pulmonary trunk or from certain forms of persistent truncus arteriosus. Pulmonary atresia may be localized to the proximal end of the pulmonary trunk or diffuse in this vessel. When nonconfluence is present, each pulmonary artery arises separately from one of three possible sources as follows: (1) a form of persistent truncus arteriosus, (2) through ducti arteriosi from the aortic arch system,