Natural history of newborn with borderline small left heart without interatrial communication.

A patient with a borderline small left heart requires difficult clinical decision making during prenatal and neonatal periods. This report describes the unusual natural history of a newborn with prenatally diagnosed hypoplastic left heart structures and early spontaneous postnatal closure of the interatrial communication. Initial deterioration from pulmonary edema and low-cardiac output improved with postnatal intensive care. During the seventh week of life, aortic coarctation was diagnosed and the infant underwent uneventful surgical repair. Despite transient clinical deterioration, early spontaneous closure of the interatrial communication in a newborn with borderline small left heart could be associated with gradual hemodynamic adaptation to postnatal biventricular circulation.