We wished to determine the relationship between circulating levels of nitri
c oxide (NO) and cardiac index (CI) in children with congenital heart disea
ses. We measured the plasma levels of nitrate/nitrite (NOx), the stable end
products of NO production as well as tumor necrosis factor-alpha (TNF-alph
a), atrial natriuretic peptide (ANP), and brain natriuretic peptide in rela
tion to various parameters determined simultaneously. The plasma NOx levels
correlated negatively with CI (r = -0.541, p < 0.05). No correlation was o
bserved between NOx and cardiac output. TNF-alpha correlated with NOx level
s (r = 0.593, p < 0.005) but not with either CI or cardiac output. Plasma l
evels of ANP and TNF-alpha were higher in atrial septal defect than those i
n the control group (p < 0.001 and p < 0.05, respectively). Elevated plasma
NOx could explain the increased basal release of endothelial NO due to hig
h pulmonary blood flow. Plasma NOx correlate negatively with CI in young pa
tients with left-to-right shunt congenital heart diseases.