Histologic study of the small pulmonary arteries in 38 patients with pulmonary atresia and intact ventricular septum

Abstract

The structure of the small pulmonary arteries was studied during autopsies performed on 38 patients with pulmonary atresia with intact ventricular septum. The thicknesses of the media of these small pulmonary arteries measured using a quantitative morphometric method varied widely. However, there was a notable tendency toward thinning of the media, especially in neonates. In cases in which the patient had undergone prostaglandin E1 treatment, the media was thinner, which suggests that the longer the treatment, the thinner the media. Intimal lesions were observed in 18 of the 38 patients (47%), including 12 of the 22 neonates (55%). Intimal lesions were also found in the patients with thinner media. Based on these results, we propose that organized thrombus formation and intimal proliferation are more likely to develop in patients with reduced pulmonary blood flow, such as in those with pulmonary atresia and intact ventricular septum. In prostaglandin-treated patients, an imbalance between the markedly thinner median muscle and the relatively higher pulmonary blood flow and pressure may contribute to fibrous intimal proliferation. Small pulmonary arteries with a strikingly thinner media may be vulnerable to higher pressure, predisposing the patient to the development of intimal lesions.