OBJECTIVE: This study was designed to investigate the pathophysiological role of adrenomedullin(ADM) in congenital heart disease. METHODS: Forty-eight children with congenital heart disease confirmed by cardiac echocardiography and catheterization were studied.The patients were divided into three groups on the basis of hemodynamic indices measured during cardiac catheterization: high pulmonary blood flow with(group 1) or without(group 2) pulmonary hypertension(mean pulmonary arterial pressure >20 mmHg) and a cyanosis group(without high pulmonary blood flow)(group 3).Six children who recovered from Kawasaki disease were used as a Control group.Plasma ADM levels were measured by radioimmunoassay. RESULTS: The plasma ADM levels from the femoral vein were significantly higher than those from femoral artery in patients with congenital heart disease.The patients from group 1 and group 3 had higher plasma ADM levels(1.9±1.8 pmol/L and 2.4±1.3 pmol/L,respectively) than the controls(1.0±1.4 pmol/L;P<0.01).Plasma ADM levels were significantly negatively correlated with mean systemic arterial pressure,oxygen saturation in mixed vein and oxygen saturation in systemic artery(r=-0.401,-0.562,-0.600,respectively;P<0.01) but positively correlated with pulmonary vascular resistance(r=0.406;P<0.01). CONCLUSIONS: Plasma ADM levels are increased in congenital heart disease with high pulmonary blood flow and hypertension or with cyanosis.Plasma ADM levels are related to pulmonary arterial resistance and hypoxemia.Increased ADM levels may play roles in reducing the pulmonary arterial resistance and alleviating hypoxemia in these patients.