Figure 1:

Study Flow Diagram of Uncomplicated Preterm Infants:

BPD, bronchopulmonary dysplasia; PH, pulmonary hypertension; PDA, patent ductus arteriosus; PMA, postmenstrual age

*119/222 infants were excluded from the uncomplicated cohort because they either were: a) diagnosed with BPD²² (n=116, 52%), b) had evidence of PH on echocardiogram at 32 weeks PMA (n=17, 15%) and/or 36 weeks PMA (n=17, 9%)²⁴ and/or c) had a PDA at or beyond one week (Day 5–7, n=57, 58%; 32 weeks PMA, n=19, 16%, and/or 36 weeks PMA, n=24, 16%). Therefore, after meeting all inclusion criteria, 103 patients (47%) infants were classified as “healthy uncomplicated preterm infants.” (Adapted from J Am Soc Echocardiogr 2017;30:685–98)¹⁴ There was significant overlap between these four categories. ** There were 239 infants recruited for this study (137 infants from the Washington University School of Medicine site in Saint Louis, USA and 102 infants from the Royal College of Surgeons in Ireland site in Dublin, Ireland). Echocardiograms were performed at Day 1 (n=30), Day 2 (n=30), 32 weeks PMA (n=117), 36 weeks PMA (n=117), and 1 year corrected age (CA, n=81) in Saint Louis, USA. Echocardiograms were performed at Day 1 (n=102), Day 2 (n=102), Day 5 (n=98), and 36 weeks PMA (n=47) in Dublin, Ireland.