Abstract: A method and apparatus for use in coronary bypass surgery procedures wherein the heart remains beating rather than completely stopping the heart, where a blockage is located in the blood vessel for the heart and an incision is made in the vessel adjacent the blockage for the grafting of a vein from another location in the patient's body, and an intraluminal shunt is inserted into the blood vessel to retain the vessel open and allow blood flow through the vessel but prevent blood flow on the exterior of the shunt. The intraluminal shunt comprises a primary perfusion tube having an enlarged bulb or occluder adjacent each end of the tube to cooperate with the interior surface of the vessel, and a secondary perfusion tube intersecting the primary tube at a point either intermediate between the ends of the primary tube or at a location providing a one-third/two-thirds ratio along the primary tube.