Pulmonary vascular bed in children with complete atrioventricular septal defect: relation between structural and hemodynamic abnormalities.

Pulmonary vascular structure was analyzed in lung tissue taken from 38 patients, aged 2 weeks to 9.1 years, with complete atrioventricular (AV) septal defect without important left AV valve regurgitation. Biopsy material was used in 27 patients (71%). Pulmonary artery (PA) pressure and resistance increased with age (r = 0.5, p less than 0.001 and r = 0.4, p less than 0.02, respectively). Intra-acinar mean PA arterial medial thickness decreased with age (r = -0.6, p less than 0.001), PA pressure (r = -0.6, p less than 0.001) and resistance (r = -0.4, p less than 0.05). Reduction in intra-acinar PA muscularity was associated with an increase in severity of obstructive intimal damage in pre-acinar PAs with age. A PA resistance of less than 6 units m2 was associated with age younger than 3 years (usually younger than 2 years), PA medial thickness of more than 19% (normal = 7.4%), and muscle extension with or without intimal proliferation. A higher resistance occurred in patients of all ages, but in those younger than 3 years structural abnormalities usually resembled those in patients with a lower resistance, whereas older patients had a normal or slightly increased PA medial thickness of 14% or less (normal = 7.4%), or classic grade III or IV disease. The 4 perioperative deaths attributed to pulmonary vascular disease occurred in patients who were similar in age and hemodynamic status to the survivors, but who had more severe pulmonary vascular abnormalities; either less muscularity with more severe intimal fibrosis or a much greater increase in muscularity, emphasizing that even potentially reversible abnormalities can prejudice intracardiac repair.