Changes in pulmonary arterial pressure in preterm infants with chronic lung disease

Background-Pulmonary arterial pressure (PAP) is raised in preterm infants with respiratory distress syndrome who subsequently develop chronic lung disease. The natural history of pulmonary hypertension in infants with chronic lung disease is unknown. Objectives-To investigate changes in PAP, assessed non-invasively using Doppler echocardiography, in infants with chronic lung disease during the Ist year of life. Methods-Serial examinations were performed in infants with chronic lung disease and healthy preterm infants. The Doppler derived acceleration time to right ventricular ejection time ratio (AT/RVET) was calculated from measurements made from the pulmonary artery velocity wave-form. Results-A total of 248 examinations were performed in 54 infants with chronic lung disease and 44 healthy preterm infants. The median AT/RVET was significantly lower in infants with chronic lung disease than in healthy preterm infants (0.31 v 0.37). AT/RVET significantly correlated with age corrected for prematurity in both infants with chronic lung disease (r = 0.67) and healthy infants (r = 0.55). There was no significant difference between the rate of change in AT/RVET between the Two groups. In infants with chronic lung disease, multivariate analysis showed that AT/RVET was significantly independently associated with age and inversely with duration of supplemental oxygen treatment. Median AT/RVET was significantly lower in infants with chronic lung disease until 40-52 weeks of age corrected for prematurity. Conclusions-Although PAP falls with increasing age in both infants with chronic lung disease and healthy preterm infants, it remains persistently raised in infants with chronic lung disease until the end of the 1st year of life.