Closure of the ductus arteriosus and development of pulmonary branch stenosis in babies of less than 32 weeks gestation.

AIMS To define how often transient pulmonary branch stenosis (PBS) develops after closure of a patent ductus arteriosus (PDA) in babies born at less than 32 weeks gestation; to describe the natural history of PBS and the relation between PBS and a cardiac murmur. METHODS Fifty three preterm infants born at a gestational age less than 32 weeks and who had PDA diagnosed on echocardiography were recruited. An echocardiogram was performed on alternate days until the ductus arteriosus closed. If PBS was diagnosed, the baby was followed up until PBS resolved. RESULTS In 59%, PBS developed in one or both branches after closure of the PDA. In 21%, both pulmonary branches were affected. In 79%, the left pulmonary artery alone was involved but the right side was never affected alone. PBS had resolved in 74% by the time the infants reached 40 weeks, in 95% at a corrected age of 6 weeks, and in 100% at a corrected age of 3 months. There is a better correlation between a cardiac murmur and PBS than between a murmur and PDA. CONCLUSIONS PBS in preterm infants is usually not present at birth but develops after closure of a PDA. PBS resolves by a corrected age of 3 months. The presence of a murmur after closure of a PDA is usually related to PBS and not to reopening of the ductus arteriosus.