A developmental abnormality in which the spiral (aortopulmonary) septum failed to completely divide the TRUNCUS ARTERIOSUS into ASCENDING AORTA and PULMONARY ARTERY. This abnormal communication between the two major vessels usually lies above their respective valves (AORTIC VALVE; PULMONARY VALVE).

Synonyms: Aortopulmonary Septal Defect, Aorticopulmonary Septal Defect, Septal Defects, Aorticopulmonary, Septal Defect, Aortopulmonary, Aortopulmonary Septal Defects, Septal Defects, Aortopulmonary, Septal Defect, Aorticopulmonary, Aorticopulmonary Septal Defects