Background Early diagnosis and effective treatment of the patent ductus arteriosus (PDA) in infants less than 32 weeks gestation remains contentious.

Objective To determine which clinical and echocardiographic parameters are associated with PDA patency in preterm infants less than 32 weeks gestation.

Design/Methods This was a prospective cohort study. An echocardiography (echo) was performed within 12–48 h of birth and a follow-up echo at 1 month of life. Parental consent was obtained.

Results 55 babies were enrolled. Median (range) gestation was 28 (24–31) weeks and birth weight 1090 g (470–1800 g). ECHO 1 demonstrated that 50 babies had a PDA present within 48 h of birth, of which 19 were large (≥2 mm) (36%) and 31 were small (59%) on colour Doppler assessment of duct diameter. Three babies died before 1 month. At 1 month 30 babies still had a PDA (58%), 10 of which were large (19%) and 19 were small (36%). Parameters significantly associated with large PDAs versus no PDA at 1 month were gestational age (26 weeks vs 30 weeks, p=0.002), birth weight (860 g vs 1290 g, p=0.007) and ventilator support at 48 h (80% vs 17%, p=0.001). Echo parameters revealed that ductal size on colour Doppler (2.5 mm vs 1.5 mm, p=0.003), end diastolic flow velocity (57 m/s vs 147 m/s, p<0.001) and peak systolic to end diastolic flow velocity ratio (2.29 vs 1.23, p=0.001) at 48 h were associated with large PDAs at 1 month.

Conclusions For infants less than 32 weeks gestation a peak systolic to end diastolic flow velocity ratio>2 within 48 h of birth is associated with a persistent large PDA at 1 month of age.