Pulmonary vascular disease in transposition of the great vessels and intact ventricular septum.

Eight of 135 (6%) children with d-transposition of the great vessels and with intact ventricular septum and no patent ductus arteriosus had evidence of progressive pulmonary vascular disease. Seven of 101 (7%) patients for whom histologic data was available, had Heath-Edwards grades IV or V pulmonary vascular disease, six had grade II, and 88 had either normal or grade I findings. One of 34 patients for whom histologic data was not available had hemodynamic evidence of pulmonary vascular disease at cardiac catheterization after the Mustard operation. When infants younger than 3 months old were excluded, eight of 85 (9%) had advanced pulmonary vascular disease. Twenty-three patients had microthrombi in their pulmonary arteries and arterioles, and in one patient thrombi were observed before the development of pulmonary vascular disease. Clinically unrecognized pulmonary microthrombi are suggested as a possible etiologic agent in the development of pulmonary vascular disease in patients with transposition of the great vessels. Progressive pulmonary vascular disease can first be discovered after the Mustard operation, even in patients without preoperative evidence of pulmonary hypertension or elevated pulmonary vascular resistance.