**9. Eisenmengers syndrome**

An unrepaired large VSD with unrestricted left to right shunt over a period of time, if not corrected, will lead to increased PVR and irreversible PVOD due to vascular remodeling. There is a bidirectional shunt initially and eventually, right to left shunt develops, as pulmonary artery pressures and PVR exceed systemic pressures and SVR, causing central cyanosis. There is a secondary erythrocytosis, polycythemia and coagulation abnormalities develop. Maladaptation of the right ventricle (RV) as a result of pressure and volume overload with time causes progressive right heart failure. Other factors that may influence risk of developing ES is presence of complex anatomy and underlying genetic and environmental factors. Diagnosis of ES is made by clinical features and echocardiography is a common monitoring tool. The patients may develop dyspnea, decreased exercise tolerance and syncope. Parameters such as O2 saturation, WHO functional class, level of exercise intolerance, reflected by six min walk distance, and NT proBNP are used for serial assessments as well as predictors of survival. Other models of risk stratification in these patients describe various clinical, laboratory and diagnostic markers to determine predictors of mortality [40]. Various other biomarkers reflecting RV dysfunction, endothelial dysfunction and some that may predict potential reversibility of pulmonary vascular lesions are being studied [17]. In a large adult study, older age, pre-tricuspid shunt
