Quantitative structural study of pulmonary circulation in the newborn with aortic atresia, stenosis, or coarctation.

Study of the structural features of the pulmonary circulation in various types of congenital heart disease makes it possible to correlate function and structure in the fetal and newborn lung. We applied quantitative morphometric techniques to the injected and inflated lungs of newborn infants who had died with obstruction to left ventricular outflow from aortic atresia, stenosis, or coarctation. The structure and development of the pulmonary circulation was judged by the number of arteries and veins and their size and wall structure, with particular attention to vessels within the respiratory unit. The study established for the first time that the structure of the pulmonary circulation is modified by the antenatal abnormalities in blood flow that occur through the heart and great vessels in the presence of congenital heart disease. Fetal multiplication of intra-acinar arteries in aortic atresia and stenosis is increased as also is the muscularity of both pre- and intra-acinar arteries and veins, muscle extending into smaller and more peripheral vessels than is normal at birth. When the pulmonary circulation is normal before birth but arterial pressure and flow are abnormally increased at birth, as in coarctation with patent ductus and ventricular septal defect, an increase in arterial diameter and muscularity is apparent within the first week of life.