Abstract: By the quantitative morphometrie method,pulmonary vascular structure was studied on the lungs of 61 normal subjects and 37 cases who died from a congenital cardiac septal defect.The results showed that early pulmonary vascular changes were:(1)The increase of pulmonary arterial muscularity—a abnormal extension of muscle into peripheral arteries and an increased medial wall thickness of the normal muscular alteries,(2) The increase of density of pulmonary muscular and partially muscular arteries,(3)The reduction of the intraaeinar arterial size.Advanced pulmonary vascular changes were the reduction of the medial wall thickness and the decrease of the density of pulmonary muscular and partially muscular arteries. The persistence of the thick arterial wall of fetal life in neonate of congenital cardiac septal defect were observed and provided the histological evidence for the delaged postnatal fall of resistance and persistent fetal circulation in congenital cardiac septal defect with left to right shunt.

Key words: quantitative morphometric method, pulmonary vascular disease, congenital cardiac septal defect