Congenital heart anomalies that, if untreated, may result in Eisenmenger syndrome include (in approximate order of occurrence— 1) Ventricular septal defect (VSD) Atrioventricular septal defect (AVSD) Patent ductus arteriosus (PDA) Aortopulmonary window Atrial septal defect (ASD) Truncus arteriosus Double outlet right ventricle (DORV) without pulmonary stenosis Partial anomalous venous return (PAPVR, whereby some of the pulmonary veins connect to the right atrium instead of the left atrium) Rare patients with single ventricle variants or with transposition of the great arteries with a persistent patent ductus arteriosus and / or ventricular septal defect may develop Eisenmenger syndrome if untreated, though the vast majority of these patients die early in infancy if the anomaly is not recognized and treated.