Calcitonin gene-related peptide has potent vasodilatory and inotropic actions. The aim of this study was to characterize the changes in this peptide in children with varying degrees of heart failure secondary to congenital heart disease with left to right shunt and to assess its relationship to systolic pulmonary arterial pressure. Plasma calcitonin gene-related peptide levels were measured in 131 children including 13 healthy ones, 43 with various degrees of heart failure secondary to congenital heart disease, and 75 with congenital heart disease without heart failure. In patients with heart failure, calcitonin gene-related peptide concentrations were markedly elevated (15.8 +/- 2.1 pg/mL) as compared with healthy control subjects (7.0 +/- 0.8 pg/mL, P < 0.05) or patients with congenital heart disease but without heart failure (18.6 +/- 1.2 pg/mL, P < 0.01). Compared with the controls, there were highly significant stepwise increases in the calcitonin gene-related peptide levels in the mild (n = 15), moderate (n = 12), and severe (n = 16) heart failure subgroups by 1.5, 1.7 and 3.4 fold, respectively. The plasma calcitonin gene-related peptide levels also correlated directly with the pulmonary arterial systolic pressure (r = 0.515, P < 0.0001). The results of this study indicate that congestive heart failure secondary to congenital heart disease with increased pulmonary flow is associated with elevated levels of calcitonin gene-related peptide that are related to disease severity. Pulmonary overcirculation may play a role in upregulation of calcitonin gene-related peptide in congestive heart failure.