Urinary NT-proBNP levels and echocardiographic parameters for patent ductus arteriosus.

OBJECTIVE: Patent ductus arteriosus (PDA) is common in preterm infants and is associated with significant morbidities. B type natriuretic peptide (BNP) is synthesized in the ventricles secondary to volume overload and excreted as urinary N-terminal pro-brain natriuretic peptide (NT-proBNP).

STUDY DESIGN: We report an observational prospective study of 64 preterm infants with birth weight ⩽1000 g. Echocardiographic parameters were obtained from clinical echocardiograms performed in the first week of life. Urinary NT-proBNP/creatinine ratios (pg mg-1 ) were measured on the same day of the echocardiograms.

RESULTS: Infants with medium to large PDA (n=39) had significantly higher NT-proBNP/creatinine levels compared with infants with small PDA (n=10) (median (IQ range): 2333 (792-6166) vs 714 (271-1632) pg mg-1 , P=0.01) and compared with infants with no PDA (n=15) (2333 (792-6166) vs 390 (134-1085) pg mg-1 , P=0.0003). Urinary NT-proBNP/creatinine ratios were significantly lower post treatment if PDA closed (n=17), P=0.001 or if PDA became smaller after treatment (n=9), P=0.004. Urinary NT-proBNP/creatinine levels correlated with ductal diameter (P⩽0.0001), but not with LA/Ao ratio (P=0.69) or blood flow velocity through the ductus (P=0.06).

CONCLUSION: Our findings indicate that there is a positive correlation between ductal diameter and urinary NT-proBNP in preterm infants.