METHODS AND RESULTS: We measured plasma N-terminal (1-98) proatrial
natriuretic peptide (proANP) in 26 cyanotic adults and 28 noncyanotic control subjects. Resting arterial oxygen saturation was significantly lower and
hemoglobin concentration and hematocrit significantly greater in cyanotic patients than in control subjects (82+/-6 versus 96+/-3%, 19.7+/-2.2 versus 14.7+/-2.1 g/dL, and 59.0+/-8.5% versus 44.3+/-5.2%, respectively, P<.0001 in all cases). Four cyanotic patients had evidence of
iron deficiency. Plasma proANP levels were elevated in cyanotic patients compared with control subjects (1828+/-1147 versus 689+/-343 pmol/L, P<.0001). Comparison of resting arterial oxygen saturation and proANP levels demonstrated an inverse linear relationship between the two measures (r=-.70, P<.0001). There was a significant linear relationship between both
hemoglobin concentration and hematocrit and proANP levels as well (r=.53, P=.0003 and r=.48, P=.002, respectively). Cyanotic patients had lower mean right atrial pressures than the control subjects (4+/-3 versus 7+/-2 mm Hg, P=.005), and there were inverse logarithmic relationships between proANP levels and systemic cardiac index (r=-.82, P=.0002), systemic
oxygen transport (r=-.68, P=.005), and mixed venous oxygen saturation (r=-.79, P<.0001).
CONCLUSIONS: Adults with cyanotic
congenital heart disease are characterized by increased levels of plasma proANP. The increased
atrial natriuretic peptide most likely results in extracellular and plasma volume depletion and reduced systemic
oxygen transport. Measures designed to increase ventricular filling may improve quality of life of these patients.