Correlations of Microradiographic and Histological

PATIENTS with congenital intracardiac defects, pulmonary hypertension, and high pulmonary vascular resistance show widespread pulmonary arteriolar obstruction from medial hypertrophy and intimal proliferation.1 2 Postmortem radiograms show enlargement of the proximal pulmonary arteries but relatively few distal branches.3 Vascular channels remaining patent in such patients are often dilated.4 Dilated thin-walled vessels are found far distant in the pulmonary arterial bed,4-6 but the vascular segments involved have not been established.6 These dilated segments have been considered to be dilated arterioles4' 6, 7 bronchopulmonary anastomoses,8