Congenital heart disease with left-to-right shunt can induce proliferation, vasoconstriction and thrombosis in the pulmonary vascular bed. Eventually, the patient may develop Eisenmenger syndrome defined as pulmonary arterial hypertension caused by high pulmonary vascular resistance with right-to-left shunt and cyanosis. Patients with Eisenmenger syndrome suffer a high risk of complications in connection with acute medical conditions, extra-cardiac surgery and pregnancy. This article describes the precautions that should be taken to reduce morbidity and mortality in these patients.