Role of Early Pulmonary Hypertension as a Risk Factor for Late Pulmonary Hypertension in Extremely Preterm Infants.

OBJECTIVE: The evidence on the role of early pulmonary vascular disease (PVD) in the development of late pulmonary hypertension (PH) in the extremely preterm infants is limited. Objectives were to determine the incidence of early and late PH in extreme preterm infants and to evaluate the role of early PH as a risk factor for development of clinically detected late PH. METHODS: It was a retrospective analysis of early echocardiograms (day of life 5-14) in preterm infants, 22 to 27 weeks' gestation, admitted to the University of Iowa NICU between July 01, 2012 to June 30, 2015. Late echocardiograms performed for clinical suspicion of PH were also analyzed. RESULTS: A total of 154 infants were included in the study. Early PH was diagnosed in 31 (20%) infants. Twenty-four (16%) infants were evaluated for clinically suspected PH. Eight (5%) infants were diagnosed with late PH. Infants with early PH had echocardiograms performed earlier than infants without the evidence of early PH. Early PH was not associated with the development of late PH (p = 0.99). CONCLUSION: Early PH is common among extremely preterm infants (20%). Five percent of infants had clinically detected late PH. Infants with early PH had echocardiograms performed earlier than infants without the evidence of early PH. Early PH was not associated with the development of clinically detected late PH.

Polymorphisms in urea cycle enzyme genes are associated with persistent pulmonary hypertension of the newborn.

BackgroundPersistent pulmonary hypertension of the newborn (PPHN) is characterized by elevated pulmonary vascular resistance. Endogenous nitric oxide is critical for regulation of pulmonary vascular resistance. Nitric oxide is generated from L-arginine, supplied by the urea cycle (UC). We hypothesized that polymorphisms in UC enzyme genes and low concentrations of UC intermediates are associated with PPHN.MethodsWe performed a family-based candidate gene analysis to study 48 single-nucleotide polymorphisms (SNPs) in six UC enzyme genes. Genotyping was carried out in 94 infants with PPHN and their parents. We also performed a case-control analysis of 32 cases with PPHN and 64 controls to identify an association between amino-acid levels on initial newborn screening and PPHN.ResultsThree SNPs (rs41272673, rs4399666, and rs2287599) in carbamoyl phosphate synthase 1 gene (CPS1) showed a significant association with PPHN (P=0.02). Tyrosine levels were significantly lower (P=0.003) and phenylalanine levels were significantly higher (P=0.01) in cases with PPHN. There was no difference in the arginine or citrulline levels between the two groups.ConclusionsThis study suggests an association (P<0.05) between SNPs in CPS1 and PPHN. These findings warrant further replication in larger cohorts of patients.