Variation in the size and distensibility of the pulmonary arteries in d-transposition of the great arteries.

The relative size of the main pulmonary artery was determined from cineangiograms of 117 patients with d-transposition of the great arteries by calculating the ration between the diameters of the main pulmonary artery and aorta. The pulmonary artery was largest in patients with ventricular septal defect or patent ductus arteriosus, or both, because of increased pulmonary arterial pressure and flow. In patients with an intact ventricular septum or with left ventricular outflow tract obstruction, or both, the main pulmonary artery was approximately the size of the aorta. Two cases of d-transposition and gross dilatation of the main pulmonary artery and hypoplastic first branch pulmonary arteries are presented. In these cases the ratio between the diameters of the main pulmonary artery and aorta was greater than in any of the other 117 cases studied...