Extremely thickened media of small pulmonary arteries in fatal pulmonary hypertension with congenital heart disease - A morphometric and clinicopathological study

There are patients with congenital heart disease and fatal pulmonary hypertension in whom the medial hypertrophy of the small pulmonary arteries is quite beyond the extent of ordinary cases of hypertension, a condition described as pulmonary hypertension with extremely thickened media of small pulmonary arteries (PH/ETM). Lungs from 6 infants, all younger than 2 years of age, who had congenital heart disease and fatal pulmonary hypertension, were analyzed by accurately measuring the media using Suwa's method. In PH/ETM, the media of the small pulmonary arteries was shown to be not only unusually thick, but extending toward the periphery, whereas the intimal changes were unexpectedly mild. In the PH/ETM group, the % wall thickness at a diameter of 50 mum (%Tw(50)), determined from regression analysis, was 23.2+/-1.3%, which was significantly higher than in either the control (10.3+/-1.2%) or ventricular septal defect group (18.9+/-1.6%). In persistent pulmonary hyper tension of the newborn (PPHN), it was 22.3+/-1.8%, not significantly different from PH/ETM. The striking medial hypertrophy in PH/ETM and PPHN was apparently confined to small pulmonary arteries and in both conditions is likely to be the result of maldevelopment of these arteries. Surgical intervention may trigger a critical elevation of the pulmonary arterial resistance.