Thromboxane A2 and prostacyclin biosynthesis in children and adolescents with pulmonary vascular disease

The pathogenesis of pulmonary vascular disease in children with congenital heart disease is incompletely understood. Thromboxane (TX) A2 and prostacyclin (PGI2) have opposing effects on platelet aggregation and pulmonary vascular smooth muscle. An imbalance in their biosynthesis could contribute to the progressive increase in pulmonary vascular resistance seen in older untreated patients with pulmonary hypertensive congenital heart disease and the thrombotic complications they may develop.

We investigated TXA2 and PGI2 biosynthesis in 15 young children (0.2 to 2.25 years old) with congenital heart disease with increased pulmonary blood flow and potentially reversible pulmonary vascular disease by measuring urinary excretion of 2,3-dinor-TXB2 and 2,3-dinor-6-oxoprostaglandin (PG) F1 alpha and compared the findings with those in 16 healthy children (0.5 to 2.8 years old). 2,3-Dinor-TXB2 excretion was greater in the patients than in control subjects (1253 +/- 161 versus 592 +/- 122 ng/g creatinine; P < .001). Excretion of 2,3-dinor-6-oxo-PGF1 alpha was 452 +/- 54 compared with 589 +/- 95 ng/g creatinine in control subjects. In 5 patients who underwent successful cardiac surgery > or = 1 year later excretion of 2,3-dinor-TXB2 decreased from 1100 +/- 298 to 609 +/- 131 ng/g creatinine (P < .05), a value comparable to those in 5 healthy children of similar age (749 +/- 226 ng/g creatinine). We also compared 15 patients (11 to 23 years old) with advanced irreversible pulmonary vascular disease with 19 healthy control subjects (10 to 23 years old). The ratio of TX to PGI2 metabolite excretion was greater in the patients than in control subjects (3.5 +/- 0.6 versus 2.0 +/- 0.3; P < .05).

There is increased 2,3-dinor-TXB2 excretion in children with congenital heart disease and a high pulmonary blood flow that may reflect an imbalance in biosynthesis of TXA2 and PGI2 in the pulmonary vascular bed. The imbalance may contribute to the progressive development of increased pulmonary vascular resistance and persists in older patients whose heart defects are uncorrected.