Right ventricle (RV) is frequently neglected in comparison with left ventricle in many aspects - pathogenetic, diagnostic or therapy. In contrast with this, right chamber is pathologically an active part in severe pulmonary arterial hypertension (PAH) associated with congenital heart defects and also importantly influences its course and prognosis. Life expectancy and quality of life do not depend on pulmonary pressure. Inversely, function and status of RV is determining. Eisenmenger´s syndrome presents an extreme severe form of PAH. Unique adaptation ability of different and specific RV causes better symptomatic image of patients with Eisenmenger´s syndrome among all patients with PAH.