Single Ventricle refers to a group of congenital heart defects in which the heart functionally has only one pumping chamber. In the normal heart, there are two pumping chambers, the right and left ventricles.  Single Ventricle incorporates a large number of severe congenital heart defects.  Examples are Tricuspid Atresia, Hypoplastic Left Heart Syndrome, Double Inlet Left Ventricle, and Double Outlet Right Ventricle. Other defects (e.g. some forms of Atrioventricular Canal Defect and Pulmonary Atresia) may create single ventricle conditions in the heart.