PARADOXICAL RELATIONSHIP BETWEEN N-TERMINAL PROATRIAL NATRIURETIC PEPTIDE AND FILLING PRESSURE IN ADULTS WITH CYANOTIC CONGENITAL HEART-DISEASE

Background Many adults with cyanotic congenital heart disease are char acterized by reduced ventricular filling pressures and decreased syste mic oxygen transport. Data from animals suggest that hypoxia can induc e synthesis and secretion of atrial natriuretic peptide. Methods and R esults We measured plasma N-terminal (1-98) proatrial natriuretic pept ide (proANP) in 26 cyanotic adults and 28 noncyanotic control subjects . Resting arterial oxygen saturation was significantly lower and hemog lobin concentration and hematocrit significantly greater in cyanotic p atients 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 evid ence of iron deficiency. Plasma proANP levels were elevated in cyanoti c patients compared with control subjects (1828 +/- 1147 versus 689 +/ - 343 pmol/L, P < .0001). Comparison of resting arterial oxygen satura tion and proANP levels demonstrated an inverse linear relationship bet ween the two measures (r= -.70, P < .0001). There was a significant li near 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), a nd there were inverse logarithmic relationships between proANP levels and systemic cardiac index (r= -.82. P = .0002), systemic oxygen trans port (r = -.68, P = .005), and mixed venous oxygen saturation (r = -.7 9, P < .0001). Conclusions Adults with cyanotic congenital heart disea se are characterized by increased levels of plasma proANP. The increas ed atrial natriuretic peptide most likely results in extracellular and plasma volume depletion and reduced systemic oxygen transport. Measur es designed to increase ventricular filling may improve quality of lif e of these patients.