Neufeld, Henry 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.

Among 60 necropsy specimens of isolated ventricular septal defects and more than 300 cases of ventricular septal defect observed at operation, 15 cases demonstrating unusual anatomic positions of the defect were found. The ventricular defect differed from the ordinary ventricular septal defect in that it usually occupied the position of the ventricular component of the defect in persistent common atrioventricular canal. For this reason it was named ventricular septal defect of the persistent common atrioventricular canal type. Deformities of one or both atrioventricular valves were common (nine of 15 cases). No atrial septal defects of the ostium primum type were present. Anatomic studies of the conduction tissue revealed that this tissue skirted the posterior and inferior aspects of the ventricular septal defect and that, as in persistent common atrioventricular canal, the course taken by the conduction tissue was unusually long, as a result of the peculiar posteroinferior position of the lower edge of the defect. The electrocardiographic features were striking. In all cases the mean electrical axis of the QRS lay above the isoelectric point; the vector loop obtained in the frontal plane from the scalar electrocardiogram was directed counterclockwise, and its main mass was above the zero line. In addition, in all cases there were signs of right ventricular overload, and in some cases of left ventricular overload as well. Electrocardiographic findings of this pattern have been thought by some authors to be diagnostic of persistent common atrioventricular canal, but we observed that they also occurred in each of the cases of isolated ventricular septal defect of the variety described herein. We recognize that in the usual variety of ventricular septal defect this electrocardiographic pattern occurs, but it does so uncommonly. We have not studied its exact incidence. The anatomy, hemodynamics, and surgical considerations are different in cases with this defect from those with persistent common atrioventricular canal. The surgical risk in these cases has been higher than that in the usual type of ventricular septal defect. In the discussion of the electrophysiologic theories that seek to explain the unusual electrocardiographic patterns in this group of cases, a new theory is offered, based on studies of the conduction system. In our opinion, the different orientation of the advancing fronts of depolarization is the result of congenital displacement of the bundle of His in its relation to the ventricular septal defect.

A case is reported of a 20-day-old infant with origin of the right pulmonary artery from the ascending aorta. Besides its abnormal origin, the artery was stenotic in its proximal half. We believe the malformation results from persistence of the distal (instead of the proximal) part of the primitive sixth aortic arch and of a portion of the right dorsal aorta. The presence of ductal tissue in the wall of the right pulmonary artery supports this concept. The pulmonary vasculature in the two lungs showed great differences in medial and intimal characteristics. A second case of origin of the right pulmonary artery from the aorta, deseribed elsewhere, provided material for comparative study of the structure of the right main pulmonary arteries and the intrapulmonary branches.

An anatomicopathologic entity of the tetralogy of Fallot with an additional finding of an accessory flap of tricuspid valvular tissue is described. In the 3 cases reported in this paper, the outstanding hemodynamic finding was a right ventricular systolic pressure that was significantly greater than the systemic systolic pressure. The hemodynamic findings were explained by the fact that the accessory tricuspid flap partially closed the large ventricular septal defect. The clinical picture was similar to that of either severe pulmonary stenosis with an intact ventricular septum or severe pulmonary stenosis with a small ventricular septal defect and a right-to-left shunt at the ventricular level.