The Pulmonary Arterial Tree in Atrial Septal Defect

IN CONTRAST to cases of ventricular septal defect in which pulmonary arterial lesions occur at a very early age, such changes are generally considered to be late phenomena in atrial septal defect. It is well known that pulmonary hypertension, when it occurs as a complication of a defect in the atrial septum, is usually not seen before adult life.1' 2 The pulmonary arteries are reported to be largely normal when the pressure in the pulmonary circulation is within normal limits.3 When the pressure is moderately elevated, intimal thickening of small muscular pulmonary arteries with subsequent narrowing of the lumen is believed to be an early change. In the presence of an increased flow, on the other hand, the pulmonary arterial tree in atrial septal defect is dilated,3 and it has been shown that dilatation of the vessels with stretching of the walls may mask the presence of medial hypertrophy.4 In view of the uncertainties regarding the changes in the pulmonary arterial tree, a study was undertaken of the pulmonary arterial branches in fetuses, infants, and children with uncomplicated atrial septal defect. Material and Methods Our material was derived from 12 subjects with uncomplicated atrial septal defect (table 1). Three of these were fetuses of 24, 30, and 36 weeks' gestation, one was a full-term stillborn infant, and the ages of the remaining eight ranged from 2 days to 11 years. Data from cardiac catheterization were available in two cases; in one of these (case