Correct answer:

After full heparinization, cannulae are inserted into the venae cavae via the right atrium to siphon off the venous return from the systemic circulation. The blood is then pumped through an oxygenator and a heat exchanger before returning to the systemic circulation via a catheter in the ascending aorta or the femoral artery. This form of bypass will perfuse the whole body with oxygenated blood at an adequate pressure while diverting it from the heart and the lungs. The heart may now be stopped and cooled by infusion via the coronary arteries of cold ‘cardioplegic’ solution containing potassium, to produce rapid cardiac arrest in diastole. If the aorta is cross-clamped, the heart may be opened in a bloodless field with access to all chambers.