The Relation of Medial Thickness of Small Muscular Pulmonary Arteries to Immediate Postnatal Survival in Patients with Ventri- Cular Septal Defect or Patent Ductus

The observation at necropsy of a patent ductus arteriosus in patients dying in the neonatal period is virtually universal. As a rule this observation is of no practical significance since death is caused by one of a large group of conditions not necessarily related to the cardiovascular system. Occasionally the finding is of importance, as in two male infants, with widely patent ducti, whom we studied recently. Both had died on the second day of life from pulmonary oedema. The onset of oedema in both patients appears to have been related to the state of the muscular pulmonary arteries, which had undergone an unusually rapid transition from the foetal to the adult form so that they appeared much thinner than comparable vessels seen in the normal infant of this age or in one with a defect allowing communication between the systemic and pulmonary circulations. This impression was confirmed by the measurement and comparison of the lumento-wall ratios of the small muscular pulmonary arteries in the two infants with patent ductus arteriosus, in 26 controls, and in 22 patients with congenital heart disease who survived the immediate postnatal period. Each of the 22 patients had an aorto-pulmonary or ventricular septal defect of sufficient size to equalize systolic pressures between the pulmonary and systemic circulations. We consider that this histological observation has a physiological basis of clinical importance which determines whether infants with patent ductus arteriosus survive or die in the neonatal period.