A Tubular Aortopulmonary Window: An Embryological Curiosity

We describe, in this report, an unusually shaped aortopulmonary communication observed in a six-month-old infant who presented with an associated ventricular septal defect. The defect was tubular, measuring 7 mm in length, and located intrapericardially between the proximal ascending aorta and the pulmonary trunk. It was well defined by transthoracic echocardiogram and was suitable for surgical ligation. We share our dilemma in naming this defect appropriately. We base our explanation on our understanding of normal development of the intrapericardial arterial trunks. There is initially an extensive aortopulmonary foramen. This is closed by apposition of a protrusion from the dorsal wall of the aortic sac, the aortopulmonary septum, with the distal margins of the outflow cushions. The spiral nature of formation of the aortopulmonary septum provides an understanding of the configuration of our tubular aortopulmonary window.