How do doctors perform open heart surgery?

Bypass: Blood returning to the heart is diverted and run through a machine that performs the function of the lungs (add oxygen to the blood) and then the blood is directed back to the arterial side of the circulation. So the blood bypasses the heart. This is necessary for operations such as replacing a valve. As the blood is not passing through the heart, the heart can be stopped during the surgery.

Different ways: The classic way is to open the chest thru the breast bone, place pt on heart lung machine and perform surgery. However, many bypass surgeries can be be done w/o the heart lung mach and the heart beating. Certain valve surgeries can be done thru small incisions between the ribs. And recently some aortic valves can be treated thru a small cut in the groin by team of surgeons and cardiologists.