Monarch Disease Ontology entry MONDO_0019944 (Eisenmenger syndrome) (ES) is an form of pulmonary arterial hypertension (PAH) associated with unoperated congenital heart disease and is characterized by congenital heart malformations with reversed or bi-directional shunting through an intra-cardiac or intervascular (usually aorto-pulmonary) communication with the development of PAH. Also known as: Eisenmenger's syndrome.