Wagenvoort, N.

A quantitative analysis was made of the pulmonary arterial medial thickness and index of medial surface area (ratio of medial tissue to pulmonary parenchyma) in 50 cases of uncomplicated ventricular septal defect in fetuses, infants, and children. The ages of the subjects ranged from 26 weeks of fetal life to 12 years. The results were compared with those obtained from a control group of the same age. During the fetal and newborn period, both the thickness and the index of surface area of the media were generally within normal limits, although in an occasional case pulmonary arterial branches were considerably thinner than those in corresponding controls. The subjects between 1 week and 5 weeks of age had a medial thickness and an index of medial surface area that were lower than the average values at the time of birth. In this regard the pulmonary arterial tree in cases of ventricular septal defect corresponded with that in normal newborn infants. Soon after, however, and most clearly from 8 weeks on, the subjects with ventricular septal defect showed a pronounced rise both in medial thickness and in the index of medial surface area, indicating the presence of considerable medial hypertrophy. Although intimal proliferation was observed in two infants of 11 and 27 days of age, it was uncommon in children less than the age of 1 year. Above that age it was almost invariably present. Plexiform or glomeruluslike structures were found in seven cases. The youngest patient with these lesions was 2½ years of age.

The pulmonary vascular tree was studied in 12 cases of uncomplicated atrial septal defect in fetuses, infants, and children. The ages of these subjects ranged from 24 weeks of fetal life to 11 years. A quantitative analysis was made of the medial thickness and of the index of medial surface area (ratio of medial tissue to pulmonary parenchyma) of the pulmonary arterial branches. In contrast to subjects with ventricular septal defect in corresponding age groups, the three fetuses in this series had medial hypertrophy, as indicated by a high index of medial surface area. In the postnatal group, both the medial thickness and the index of medial surface area were also usually greater than in the controls of corresponding ages, notably in two patients, who, at the ages of 7 weeks and 4 months, died of cardiac failure. No satisfactory explanation for these unexpected findings can be offered. Slight to moderate intimal proliferation was observed in some muscular and elastic pulmonary arteries, in bronchial arteries, and in pulmonary veins in several subjects. Thickening of the intima in elastic arteries was observed in a fetus of 26 weeks' gestation. Pronounced obliterative intimal changes were found in only one subject, an 11-year-old girl with severe pulmonary hypertension.