Lung biopsy findings in transposition of the great arteries with ventricular septal defect: potentially reversible pulmonary vascular disease is not always synonymous with operability.

Pulmonary vascular structure was analyzed in lung biopsy specimens taken from 28 children, aged 2 months to 15 years, with transposition of the great arteries and ventricular septal defect. Cellular intimal proliferation occurred in infants as young as 2 months, but it increased markedly between ages 7 to 9 and 10 to 12 months, and the increased obstruction was associated with a lower mean percent arterial medial thickness in patients older than 10 months than was found in younger patients. Early generalized arterial dilation appeared without the intimal fibrosis and dilation lesions characteristic of classical grade III and IV pulmonary vascular disease. Intimal abnormalities increased with age and pulmonary artery pressure, but mean percent arterial medial thickness was inversely related to mean pulmonary artery pressure (r = -0.5; p less than 0.0001). Nine patients survived intracardiac repair and six did not. Five of the patients who died were of similar age (12 months or less), had similar preoperative hemodynamic and pulmonary vascular abnormalities compared with the survivors and died after a clinical course compatible with pulmonary vascular disease. The findings emphasize that potential structural reversibility is not synonymous with "operability." Further studies are indicated on the function of the excessively muscularized pulmonary vascular bed of such infants.