Elevated plasma levels of adrenomedullin in congenital cyanotic heart disease

Adrenomedullin is a novel hypotensive peptide originally isolated from huma n pheochromocytoma. Accumulating evidence suggests the possible involvement of adrenomedullin in the physiology of the pulmonary circulation and the p athophysiology of hypoxaemia. The aim of the present study was to investiga te the pathophysiological significance of adrenomedullin in hypoxaemia caus ed by congenital cyanotic heart disease. Subjects were 16 patients with con genital cyanotic heart disease aged 0.8-10 years (Group C) and 12 age-match ed control subjects (patients with coronary artery dilatation after Kawasak i disease; Group N). Plasma adrenomedullin concentrations were measured, us ing radioimmunoassay, in femoral venous, pulmonary arterial and pulmonary v enous blood obtained during cardiac catheterization. Plasma adrenomedullin concentrations in Group C were significantly (3-fold) higher than those in Group N at all sampling sites. In Group C, plasma adrenomedullin concentrat ions in pulmonary venous blood were significantly lower than those in pulmo nary arterial blood. Pulmonary uptake of adrenomedullin in Group C was sign ificantly greater than that in Group N. Patients with congenital cyanotic h eart disease showed elevated plasma adrenomedullin concentrations and an in creased uptake of adrenomedullin in the pulmonary circulation, which may ac t to dilate pulmonary vessels and increase pulmonary blood flow to alleviat e hypoxaemia. Intrinsically increased adrenomedullin levels may function as a compensatory mechanism for hypoxaemia in congenital cyanotic heart disea se.