This treats a blocked coronary artery in your heart. That's one of the arteries that supplies blood to your heart's tissue. With a bypass, blood will flow around the blockage so it can nourish this tissue.
To begin, you're put to sleep. To reroute your blood, your surgeon will need a healthy blood vessel from somewhere else in your body. We call this a "graft." It's often taken from a leg or wrist. Or, the surgeon may be able to use an artery in your chest. For some patients, more than one graft is needed. Next, the surgeon exposes your heart. It's stopped for the surgery. A machine will pump your blood for you.
Now the surgeon finds any blockages in your coronary arteries. To fix a blockage, a graft is attached to your aorta and to an opening made just below the blockage. Sometimes, a nearby artery can be used. If so, only one end of it needs to be connected, because it already has a supply of blood.
Finally, your heart is restarted, and your chest is closed and bandaged. Follow your surgeon's plan for a safe recovery.