The goal of coronary artery bypass graft surgery (CABG) is not to repair or remove any blocked arteries, but to detour blood around a blockage in a coronary artery and reestablish the flow of oxygen-rich blood to the heart. To create the detour, a segment of a blood vessel is taken from another part of the body. The segment may be taken from one of the following:

• The saphenous vein from the leg is commonly used.
  
  
• The internal mammary artery from the chest is usually preferred for key artery branches because it tends to remain open longer. Some call it the internal thoracic artery.
  
  
• The radial artery from the arm and sometimes arteries from the stomach (gastroepiploic artery) may also be used as bypass grafts.

Depending on which blood vessel is used, one end is either sewn to the aorta or may remain connected to the larger artery where it originated. The other end is attached (grafted) beyond the blockage in the coronary artery. As a result, blood can flow around the blocked area, increasing the supply of oxygen and nutrients to the heart muscle.

Bypass surgery may be recommended for individuals with a history of any of the following:

• Narrowing in several coronary artery branches (common in people with diabetes)
  
  
• Severe narrowing in the left main coronary artery
  
  
• Blockage in the coronary artery or another condition that may not or has not responded to other treatments (e.g., angioplasty)
  
  
• Severe angina

Bypass surgery carries some risks, including a less than 5 percent chance of heart damage and a less than 2 percent chance of death. Studies show that women have a slightly higher risk during or immediately after bypass surgery. This may relate to the fact that women who undergo the surgery are generally older and in poorer health, and their smaller body size makes the surgery technically more difficult.  However, the overall risks are relatively low when compared to the fact that many of these bypass operations significantly lengthen and improve the quality of the patient’s life.

In some cases, the grafted arteries may also become blocked and require a second bypass surgery. Second bypass has slightly higher risks than the initial surgery, because patients are older and other, less optimal blood vessels must be used for the new grafts. However, bypassed arteries can remain functioning for many years, especially when the patient makes diet and exercise adjustments for cardiac health. Therefore, bypass surgery remains a popular choice for physicians treating severe coronary artery disease.