Arteries carry blood from the heart to the rest of the body. But sometimes arteries become blocked. When this happens, surgeons create a new channel to bypass the blockage. Doctors call it bypass graft surgery. It uses a working blood vessel from another part of the body -- the graft -- to channel blood around the blocked area.
When is bypass surgery needed?
The aorta is the main artery that carries blood from the heart. Two main blood vessels branch from the base of it: the right and left coronary arteries. Each of the coronary arteries has many branches.
When plaque buildup narrows an artery to about 70% of its normal size, the artery is essentially blocked. Less severe blockage can be relieved by angioplasty and stenting. That's when a tiny balloon is threaded into the blocked artery and slowly inflated. Then a tube called a stent is used to keep the artery open.
But severe blockage usually requires bypass surgery.
What is multiple bypass surgery?
Sometimes several arteries are blocked, and several bypasses are needed. If, for example, there were blockages in all three coronary arteries and one branch, a person would get four bypasses. This is called quadruple bypass surgery.
People who need several bypasses aren't necessarily at higher risk than those who need just one, says UCLA professor Prediman K. Shah, MD, director of cardiology and the Atherosclerosis Research Center at Cedars-Sinai Medical Center in Los Angeles.
"It is not the number of bypasses that dictates a patient's risk," Shah tells WebMD. "The risk is more dependent on the general condition of the patient, whether the patient has other conditions, such as kidney disease or diabetes, and the condition of the heart muscle itself. So if the patient's condition is good, the number of bypasses may mean a longer surgery but not significantly greater risk."