A bypass is a rerouting of the circulation around an area that is blocked, usually by arterial plaque. Arterial plaque may also be referred to as atherosclerotic plaque.

Most Americans are familiar with coronary artery bypass graft (CABG) surgery, which uses small veins or arteries to get blood around blocked arteries in the heart to improve blood flow. Arterial bypass surgery uses the same principles.

Today, in cases where arterial blockages cannot be successfully reopened with angioplasty and/or stenting, bypasses are performed between the open artery above the blockage and another open artery below the blockage. Depending on the size and location and length of the artery to be bypassed, these operations may be done utilizing a segment of vein or artery harvested from the patient, or a synthetic graft made of Teflon or polyester. Although there is sometimes debate regarding angioplasty and/or stenting versus bypass surgery in the treatment of severe vascular disease, today most cases that appear amenable to angioplasty and/or stenting are initially treated in that manner.