Fig. 1

Flowchart of study patient selection. An electronic health record database query was performed for <32 weeks gestation at birth, < 1500 g birthweight, neonatal intensive care unit, and echocardiographic procedure. 586 infants were identified, and 25 of these met exclusion criteria. 556 patients were included in the study, and 92 (16%) had PH on any one echocardiogram while in the neonatal intensive care unit. Of the 92 infants with PH, 59 (64%) also had PH on their final echocardiogram of the hospital stay. Of these 59 infants, 32 had more than one echocardiogram and the last study during the neonatal stay showed PH