Persistent pulmonary hypertension of the newborn (persistent fetal circulation)
Introduction
Failure to reduce pulmonary vascular resistance in the postnatal period
Etiology, pathogenesis
- primary (idiopathic) — affects term
infants an has no obvious pulmonary or cardiovascular causes
- secondary — with known etiology for
example lung hypoplasia, masive meconium aspiration,
pneumonia, congenital heart diseases or bronchopulmonary
dysplasia
Clinical signs
Idiopathic PPHN:
- central cyanosis
- respiratory distress
- right to left shunt across the foramen ovale and the ductus arteriosus
- decreased pulmonary blood flow
Histology
Preacinar and intra-acinar pulmonary arteries and arterioles
show medial hyperplasia with extension of smooth muscle into
small peripheral vessels. It is likely that the arterial
changes begin in utero from increased sensitivity to hypoxia
or stress or primary failure of mechanism governing arterial
muscularization.