A syndrome characterized by the reversal of a septal defect-associated left-to-right shunt due to the resulting secondary pulmonary hypertension. the presence of the pulmonary hypertension causes increased pressure in the right heart chambers resulting in the reversal of the shunt into a right-to-left shunt. signs and symptoms include cyanosis, pulmonary hypertension, heart failure, and high red blood cell count.

Eisenmenger syndrome or Eisenmenger's syndrome is defined as the process in which a long-standing left-to-right cardiac shunt caused by a congenital heart defect (typically by a ventricular septal defect, atrial septal defect, or less commonly, patent ductus arteriosus) causes pulmonary hypertension and eventual reversal of the shunt into a cyanotic right-to-left shunt. Because of the advent of fetal screening with echocardiography early in life, the incidence of heart defects progressing to Eisenmenger syndrome has decreased. Eisenmenger syndrome in a pregnant mother can cause serious complications, though successful delivery has been reported...