Dramatic advances in the diagnosis and treatment of congenital heart disease (CHD), the most common inborn defect, has resulted in a growing population of adults with CHD. Eisenmenger syndrome (ES) represents the extreme form of pulmonary arterial hypertension associated with CHD, characterized by markedly increased pulmonary vascular resistance with consequently reversed or bidirectional shunting. While ES is a direct consequence of a heart defect, it is a fundamentally multisystem syndrome with wide-ranging clinical manifestations. The introduction of targeted pulmonary hypertension therapies aimed has subtly shifted clinical focus from preventing iatrogenic and other adverse events toward cautious therapeutic activism.