Abstract
Despite growing awareness of the clinical importance of pulmonary hypertension (PH) in preterm infants, uncertainty persists regarding the different clinical settings in which abnormalities of pulmonary vascular growth, function, and structure contribute to high morbidity and mortality, and potential interventions to improve outcomes are uncertain. A major gap for improving outcomes of preterm infants with PH has been the limited characterization of the distinct settings of PH and related disease-specific mechanisms in preterm infants that represent diverse pulmonary vascular phenotypes of prematurity. In comparison with term newborns, preterm infants have a higher risk for developing hypoxemia due to suprasystemic levels of PH in preterm infants shortly after birth or persistent pulmonary hypertension of the newborn (PPHN). Variable and milder levels of PH have also been demonstrated in preterm infants without evidence of severe hypoxemic respiratory failure, suggesting delayed vascular transition of the lung which is associated with higher risks of mortality and developing bronchopulmonary dysplasia (BPD). In addition, early echocardiographic signs of PH at day 7 are strongly associated with the subsequent diagnosis of BPD, late PH, and respiratory disease throughout early childhood. In infants with evolving or established BPD, PH that persists beyond the first few months of life in preterm infants is associated with high mortality. Recent data further show that PVD can persist and cause PH in prematurely born adults. Overall, more precise characterization and studies of diverse pulmonary vascular phenotypes in preterm infants will be likely to improve the development of therapeutic strategies to optimize care of preterm infants with PH.