Differential lung function in atrial septal defect.

C LASSICAL studies of atrial defect1' 2 have mentioned only the total pulmonary blood flow and the appearance of pulmonary plethora on the chest radiograph. No mention has been made of differences between the two lungs. The present study was suggested by investigations on the first patient in this series. He was a 50-year-old man whose atrial septal defeet was confirmed by cardiac catheterization and subsequently repaired under hypothermia. The pulmonary vascular resistance was 4 units (table 1) and the pulmonary blood flow was small for an atrial septal defect. This atypical case presented several difficulties, among which was the difference in the radiographic appearance of vascularity of the 2 lungs (fig. 1). The right lung appeared plethoric and the left oligemic. Angiocardiography confirmed this impression. showing large, well-filled vessels in the right lung and attenuated vessels of normal distribution in the left. Bronehospirometry showed nearly normal distribution of the ventilation and vital capacity but 85 per cent of the oxygen uptake took place in the right lung and only 15 per cent in the left (normal 55 per cent on the right and 45 per cent on the left3). Bronchial abnormality was excluded by a normal left bronchogram. Subsequently the posteroanterior radiographs of several patients with atrial septal defect appeared to show a similar, though less marked, discrepancy between the vascular markings in the 2 lungs. It was thought that there may be a regular difference in the