Acute and Chronic Fetal Pulmonary Hypertension Alter Pulmonary Vasoreactivity

Abstract

Persistent pulmonary hypertension of the newborn (PPHN) is the failure of the pulmonary circulation to adapt successfully to postnatal conditions. Associated with a wide variety of neonatal cardiopulmonary disorders, PPHN represents the inability to achieve or sustain a drop in pulmonary vascular resistance during the immediate newborn period. Previous clinical and experimental studies suggested that intrauterine events may play important roles in its pathogenesis. Supportive evidence includes: (1) the timing of onset of disease within hours of birth; (2) the severity of histologic findings at autopsy of infants with severe PPHN dying within the first few days, including marked smooth muscle and perivascular adventitial thickening;1 and (3) animal studies suggesting that fetal stresses, such as hypoxia or hypertension, can cause smooth muscle thickening of small pulmonary arteries.