Eisenmenger syndrome refers to any untreated congenital cardiac defect with intracardiac communication that leads to pulmonary hypertension, reversal of flow, and cyanosis. previous left-to-right shunt is converted into a right-to-left shunt secondary to elevated pulmonary artery pressures.

Eisenmenger complex is a specific subset of Eisenmenger syndrome, and consists of: ventricular septal defect (VSD) severe pulmonary arterial hypertension resulting in. shunt reversal and cyanosis