Changes in pulmonary artery pressure during early transitional circulation in healthy full-term newborns

Although pulmonary artery systolic pressures (PASPs) are frequently measured in newborn infants using the tricuspid regurgitant jet velocity or ductal Doppler velocity, little is known about the reference range in the general population.

This was a retrospective study of 296 neonates less than 14 days of age who were evaluated using echocardiography. Patients included in this study did not have clinical or acquired cardiac disease. PASP was estimated using the ductal Doppler velocity and/or the tricuspid regurgitant jet velocity and the Bernoulli equation.

The majority of the definite right-to-left through the ductus arteriosus was limited to the first 6 h after birth, and the majority of the left-to-right shunt was limited to 10 h after birth. After 10 h, 24 infants with Doppler color-flow imaging revealed a very small and transient jet. The percentage of measurable tricuspid regurgitation was 91% after 24 h. Multivariable regression analysis found that there was a significant correlation between neonatal age and PASP (determined from tricuspid regurgitant jet velocity and Bernoulli equation: r(2)=0.748, P<0.0001; and from ductal Doppler velocity: r(2)=0.179, P<0.001). The upper 95% limit for PASP measured in healthy neonates younger than 14 days was 39.1 mmHg.

The ductal Doppler velocity is measured more easily for monitoring PASP than tricuspid regurgitant jet velocity in newborns soon after birth; however, in neonates older than 24 h, the tricuspid regurgitant jet velocity is easier for measurement. Age is an independent impact factor of PASP in the neonates. And PASP values gradually decreased to less than 39.1 mmHg by 14 days after birth.