Background This study was designed to investigate plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in patients with atrial septal defect (ASD), whose right ventricular loading patterns vary from simple volume overloading to both volume and pressure overloading.

Methods and Results Plasma ANP and BNP in the pulmonary artery were measured in 31 adult patients with ASD and 11 control subjects. On the basis of the presence of pulmonary hypertension (PH, mean pulmonary arterial pressure >20 mm Hg), patients with ASD were divided into two groups, patients without PH (group 1, n = 21) and those with PH (group 2, n = 10). Cardiac catheterization was performed to measure mean pulmonary arterial pressure and pulmonary blood flow. Plasma ANP was significantly higher in both group 1 and group 2 than in the control group. Plasma BNP and BNP to ANP (BNP/ANP) ratio were significantly higher in group 2 than in the control group, although they were not significantly elevated in group 1. Plasma ANP positively correlated with the degree of pulmonary blood flow (r = 0.54, p < 0.01), whereas plasma BNP positively correlated with the magnitude of mean pulmonary arterial pressure (r = 0.73, p < 0.001). BNP/ANP >1 was a powerful marker for the presence of PH (sensitivity 90%, specificity 90%).

Conclusions Plasma ANP levels were elevated in adult patients with ASD regardless of PH. In contrast, plasma BNP levels were elevated in proportion to the severity of PH complicating ASD. Thus BNP and ANP may represent differing aspects of cardiac response to right ventricular overload in patients with ASD. (Am Heart J 1998;136:297-301.)