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Brain natriuretic peptide concentrations predict haemodynamically significant patent ductus arteriosus in preterm infants

Presented at the Neonatal Society 2002 Summer Meeting (programme).

Puddy VF1, Amirmansour C2, Williams AF1, Singer DRJ3 (introduced by Dr S Calvert)

1 Regional Neonatal Unit, St George's Hospital Medical School, London, UK
Heart Science Centre, Imperial College at the NHLI, Harefield, UK
3 Department of Pharmacology and Clinical Pharmacology St George's Hospital Medical School, London, UK

Background: Patent ductus arteriosus (PDA) is an important cause of morbidity in extremely preterm infants. Increased plasma BNP is a common feature of adult cardiac disease (1) and reflects the haemodynamic shunt in the PDA (2). We measured plasma BNP concentrations in preterm infants to assess their value as a predictor of later haemodynamically significant PDA.

Design: We studied 18 preterm infants (12 male), mean gestational age 30 weeks (range 24 - 34 weeks), mean weight 1.37kg (range 0.54 - 2.13kg) and 11 term healthy controls. Plasma BNP levels were measured by double-antibody radio-immunoassay on days 3, 5 and 7 of life and an echocardiogram performed on day 7. Results are for mean±SEM. Data were compared by Mann-Whitney U tests.

Results: On day 7, twelve infants had a normal echocardiogram (gestation 31±1weeks; birth weight 1.56±0.10 kg) and six an echocardiographically proven PDA without other cardiac disease (gestation 27±1weeks; birth weight 0.99±0.15 kg). Four of these were treated successfully, one by surgical ligation, 3 with non-steroidal anti-inflammatory treatment; 2 had haemodynamically insignificant closing ducts. BNP concentrations on days 3, 5 and 7 (P<0.001) and LA:Aortic root ratio on day 7 (P=0.04) were higher in infants with persisting PDA (Table). In the absence of PDA, plasma BNP levels by day 3 were similar to values in the healthy term neonatal range (9 - 190pg/ml). Treatment of PDA reduced plasma BNP concentrations to similar levels (13±5pg/ml; n=4).

 P<0.001 vs. no PDA; † P=0.04 vs. no PDA

Conclusions: Plasma BNP levels are raised in preterm infants and fall to values in the adult range in the first week of life. In the first days of life plasma BNP levels are over 10-fold increased and remain markedly elevated in preterm infants with a persistent PDA at the end of the first week. Early measurement of plasma BNP is a potential method of predicting preterm infants at risk of a significant PDA who may require intervention.

1. Cowie MR, Lancet 1997; 350:349-5
2. H Holmström, Acta Paediatrica 2001; 90:184-191

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