Coronary Artery Bypass Graft Surgery
(CABG)
Revising Medical Author: Daniel
Kulick, MD, FACC, FSCAI
Revising Medical Editor: William C. Shiel, Jr., MD, FACP, FACR
What is coronary artery bypass graft (CABG) surgery?
According to the American Heart Association 427,000 coronary artery bypass
graft (CABG) surgeries were performed in the United States in 2004, making it one of the most commonly performed
major operations. CABG surgery is advised for selected groups of patients with
significant narrowings and blockages of the heart arteries (coronary artery
disease). CABG surgery creates new routes around narrowed and blocked arteries,
allowing sufficient blood flow to deliver oxygen and nutrients to the heart
muscle.
How does coronary artery disease develop?
Coronary artery disease (CAD) occurs when atherosclerotic plaque (hardening of the
arteries) builds up in the wall of the arteries that supply the heart. This
plaque is primarily made of cholesterol. Plaque accumulation can be accelerated
by smoking, high blood pressure, elevated cholesterol, and diabetes. Patients
are also at higher risk for plaque development if they are older (greater than
45 years for men and 55 years for women), or if they have a positive family
history for early heart artery disease.
The atherosclerotic process causes significant narrowing in one or more
coronary arteries. When coronary arteries narrow more than 50 to 70%, the blood
supply beyond the plaque becomes inadequate to meet the increased oxygen demand
during exercise. The heart muscle in the territory of these arteries becomes
starved of oxygen (ischemic). Patients often experience chest pain (angina) when
the blood oxygen supply cannot keep up with demand. Up to 25% of patients
experience no chest pain at all despite documented lack of adequate blood and
oxygen supply. These patients have "silent" angina, and have the same risk of
heart attack as those with angina.
When a blood clot (thrombus) forms on top of this plaque, the artery becomes
completely blocked causing a heart attack.
When arteries are narrowed in excess of 90 to 99%, patients often have
accelerated angina or angina at rest (unstable angina). Unstable angina can also
occur due to intermittent blockage of an artery by a thrombus that eventually is
dissolved by the body's own protective clot-dissolving system.
Next: How is coronary artery disease diagnosed? »
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