The purpose of bypass surgery is to bypass the narrowed or blocked artery. Each bypass procedure improves blood supply to your heart muscle. You may need one or several bypasses, depending on the number of blockages you have and the number of branches and area of affected heart muscle. An incision is made through the sternum or breast bone. A second incision may be necessary to remove a piece of vein or artery from your chest wall, arm or leg to be used as a bypass