Initially that right atrium can function as a hydraulic pump to drive the pulmonary circulation when an atriopulmonary anastomosis is made in Fontan surgery for tricuspid atresia.
In 1873 Kussmaul reported that in patients with constrictive pericarditis, the expected inspiratory collapse of neck veins was replaced by increased inspiratory distension.
AR in operated tetralogy of Fallot due to: dilatation of aortic root, lack of support due to subaortic VSD, valvular deformation due to retraction of surgical patch.