Plasma Levels of Nitrate in Congenital Heart Disease: Comparison with Healthy Children

Abstract

Nitric oxide (NO) is an endothelium- derived relaxing factor, and plasma nitrate is the stable end product of NO production. The aim of this study was to investigate the change in levels of plasma nitrate according to age and to elucidate the effect of pulmonary hypertension (PH) associated with congenital heart disease on NO production. We measured plasma levels of nitrate in 48 healthy children aged 5 days to 12 years to establish the normal range. Forty-six preoperative patients aged 4 months to 12 years with congenital heart disease were studied by cardiac catheterization. Plasma nitrate in healthy children decreased with age, from 1 month to 1 year, and then remained almost constant until the age of 12 years. Plasma nitrate was significantly increased in 22 preoperative patients with PH (mean pulmonary arterial pressure >?25 mmHg) compared with age-matched normal controls: (mean 56.9 vs 33.5 µmol/L, p<0.05) and was significantly correlated with pulmonary to systemic pressure ratio (r= 0.83, p < 0.0001). There was no significant difference between plasma nitrate levels in 24 preoperative patients without PH and those in the age-matched normal control (mean 25.6 vs 24.9 µmol/L). In 10 patients with preoperative PH who were examined before and after surgery, plasma nitrate levels remained high in the cases with residual PH but decreased to the normal range in the cases without residual PH. Plasma nitrate level is useful for evaluating PH both before and after operation in patients more than 4 months of age, and it is important to note differences in normal plasma nitrate levels according to age.