Coronary artery bypass graft surgery (CABG) is a procedure used to
treat coronary artery disease in certain circumstances. Coronary
artery disease (CAD) is the narrowing of the coronary arteries
(the blood vessels that supply oxygen and nutrients to the heart
muscle), caused by a buildup of fatty material within the walls of the arteries.
This buildup causes the inside of the arteries to become rough and
narrowed, limiting the supply of oxygen-rich blood to the heart muscle.
One way to treat the blocked or narrowed arteries is to bypass the
blocked portion of the coronary artery with another piece of blood
vessel. Blood vessels, or grafts, may be pieces of a vein that are
then grafted above and below the blocked area of a coronary artery,
allowing blood to flow around the obstruction. Veins are usually taken
from the leg, but arteries from the chest may also be used to create a
One end of the graft is attached above the blockage and the other
end is attached below the blockage. Thus, the blood is rerouted
around, or bypasses, the blockage through the new graft to reach the
This bypass of the blocked coronary artery can be done by performing
coronary artery bypass surgery.
Traditionally, in order to bypass the blocked coronary artery in
this manner, the chest is opened in the operating room and the heart
is stopped for a time so that the surgeon can perform the bypass. In
order to open the chest, the breastbone (sternum) is cut in half and
Once the heart is exposed, tubes are inserted into the heart so that
the blood can be pumped through the body during the surgery by a
cardiopulmonary bypass machine (heart-lung machine). The bypass
machine is necessary to pump blood while the heart is stopped and kept
still in order for the surgeon to perform the bypass operation.
While the traditional "open heart" procedure is still
performed and often preferred in many situations, newer, less invasive
techniques have been developed to bypass blocked coronary arteries.
"Off-pump" procedures, in which the heart does not have to
be stopped, were developed in the 1990's. Other minimally-invasive
procedures, such as key-hole surgery (performed through very small
incisions) and robotic procedures (performed with the aid of a moving
mechanical device), are also in development.
Other related procedures that may be used to assess and/or treat the
To better understand how coronary artery disease affects the heart, a
review of basic heart anatomy and function follows.
The heart is basically a pump. The heart is made up of specialized
muscle tissue, called the myocardium.
The heart's primary function is to pump blood throughout the body,
so that the body's tissues can receive oxygen and nutrients and have
waste substances taken away.
Like any pump, the heart requires fuel in order to work. The
myocardium requires oxygen and nutrients, just like any other tissue
in the body.
However, the blood that passes through the heart's chambers is only
passing through on its trip through the body - this blood does not
give oxygen and nutrients to the myocardium. The myocardium receives
its oxygen and nutrients from the coronary arteries. The coronary
arteries lie on the outside of the heart and supply oxygenated blood
to the heart tissue.
When the heart tissue does not receive an adequate blood supply, it
cannot function as well as it should. If the myocardium's blood supply
is decreased for a length of time, a condition called ischemia may develop.
Ischemia can decrease the heart's pumping ability, because the heart
muscle is weakened due to a lack of food and oxygen.
For many years, coronary artery disease (CAD) was commonly called
"hardening of the arteries" and was not easily treated.
However, in the last 30 years, many advances have been made in the
diagnosis and treatment of cardiac diseases.