The main purpose of this study was to investigate whether circulating natriuretic peptides in premature infants reflect the hemodynamic significance of a patent ductus arteriosus (PDA). The study comprises 120 examinations in 55 premature infants with a mean gestational age of 27.2 wk and a mean birthweight of 933 g. Based on clinical and echocardiographic findings, the hemodynamic influence of ductal shunting was classified as small, moderate or large. Blood samples for N-terminal proatrial natriuretic peptide (Nt-proANP) and brain natriuretic peptide (BNP) were analysed after completion of the clinical part of the study. Linear regression indicated a very strong association between Nt-proANP and BNP (adjusted R = 0.89). The mean levels of Nt-proANP and BNP increased with the size of the shunt through a PDA, and peptide values followed hemodynamic alterations. The size of PDA accounted for 50% and 47% of the total variation in the plasma values of Nt-proANP and BNP, respectively. In detecting an echocardiographically significant PDA, the area under a ROC curve was 0.94 for Nt-proANP and 0.90 for BNP.
Conclusion: The magnitude of shunting through a PDA is the main determinant of plasma levels of natriuretic peptides in premature infants. Nt-proANP and BNP seem to have the same pattern of secretion. Our findings indicate that measurements of natriuretic peptides may provide clinically relevant information in the hemodynamic assessment of premature infants.