Prenatal Narrowing or Closure of the Foramen Ovale.

PRENATAL closure or narrowing of the foramen ovale is an uncommon cardiac anomaly usually associated with neonatal death. Such cases afford a unique opportunity to study the effects of reducing a major intracardiac shunt normally present in fetal life. The current study demonstrates new consequences of reducing this shunt. In late gestation, about one half of the blood reaching the right atrium normally passes to the left atrium through the foramen ovale.' When this flow is reduced by premature narrowing of the foramen ovale, the diverted blood presumably passes into the right ventricle, increasing the output of that chamber. From this point, blood must pass through the pulmonary circuit or through the still patent ductus arteriosus. Normally, flow through the ductus is more than twice that through the lesser circulation.1 Unless fetal narrowing of the foramen ovale greatly increases pulmonary flow, blood flow into the left atrium and ventricle would be expected to be decreased. Most cases of narrowed or closed foramen ovale reported to date have had features suggesting this hemodynamic pattern. All but three of the published cases have had a hypoplastic left atrium and ven-tricle, the low capacity of these chambers suggesting a reduced volume of prenatal blood flow.2-4 Most of the clinical features of these cases have resembled the "hypoplastic left heart syndrome."5 The current study suggests that the left heart may not be hypoplastic as often as previously assumed in infants with the anom-736 aly. Twelve cases are presented in which a narrowed or closed foramen ovale was associated with left heart chambers of normal or near-normal size. Abnormalities in the lesser circulation rather than left heart changes help to explain why these infants died in the neonatal period. There is a possibility that appropriate therapy in such cases might lead to prolonged survival. Clinical Data Historical data on the 12 cases are detailed in table 1. A similar clinical course was observed in nine of the 10 who were liveborn. Respiratory distress was recorded almost from birth in two cases and within 12 hours of birth in six others. Cyanosis was observed soon after birth in all but cases 4 and 9 in which it was observed at 48 and at 16 hours, respectively. In case 5 it was confined to the lower two thirds of the body. Both stillborn infants were edematous as were four of the liveborn infants. In two of these …