The invention provides a system and method for establishing cardiopulmonary bypass and performing an interventional procedure in a patient's heart or great vessel with a minimum of arterial and venous penetrations. In one embodiment, a bypass cannula (180) configured for introduction into a patient's artery includes a blood flow lumen (188) which may be connected to a cardiopulmonary bypass system (92,94,96,100). A catheter shaft (202) is coupled to the bypass cannula, usually within the blood flow lumen, and has a member (216) at its distal end for performing an interventional procedure within the heart or great vessel. In a particular embodiment, the catheter shaft has an expandable member such as an inflatable balloon disposed near its distal for occluding the ascending aorta so as to substantially block all blood flow therethrough for a plurality of cardiac cycles. The catheter shaft has an inner lumen (212) through which cardio-plegic fluid may be delivered upstream of the occluding member to infuse cardio-plegic fluid into the coronary arteries for arresting the heart. The blood flow lumen in the bypass cannula is connected to a cardiopulmonary bypass system, which receives deoxygenated blood from the patient's venous system, oxygenates the blood, and delivers the oxygenated blood to the patient's arterial system through the blood flow lumen. <；IMAGE>；
