Pulmonary vascular disease in ventricular septal defect: structural and functional correlations in lung biopsies from 85 patients, with outcome of intracardiac repair.

Pulmonary vascular structure was analysed using morphometric techniques, and arterial wall abnormalities in lung biopsy specimens taken from 85 cases of ventricular septal defect, aged 3 weeks to 30 years were described. The defect was closed in 53 patients, 12 died at operation and 11 survivors were recatheterized. Structural examination revealed a characteristic pathological picture which appeared to precede classical grade IV pulmonary vascular disease. This predilatation phase was identified by finding pre-acinar obstructive intimal proliferation or fibrosis, associated with only a slight increase in intra-acinar arterial muscularity, in the absence of stigmata of grade IV disease in patients with a pulmonary resistance greater than 6 units m2. Predilatation features occurred in 62 per cent of patients who either died at repair or who had post-operative pulmonary hypertension. These findings help identify a high risk group in whom resistance is higher than expected in the absence of classical grade IV changes. In addition, a marked increase in muscularity without intimal obstruction can also be associated with a pre-operative resistance of more than 6 units m2. The presence of medial hypertrophy only does not ensure either survival or a normal post-operative pulmonary arterial pressure. Early intra-cardiac repair is recommended before obstructive intimal fibrosis develops during the second year.