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Coronary artery bypass graft (CABG)
surgery is an operation designed to detour blood around a narrowed segment of a heart artery in an effort restore blood flow to the heart muscle. Usually a vein graft from the leg is used for the bypass however other vessels may be used for the graft. The surgery can eliminate chest pain, improve exercise capability
and lengthen life. Anatomy and Physiology The heart is a muscular organ about the size of a clenched fist
It lies in the chest beneath the sternum or breastbone. The function of the heart is to supply blood to the body
The heart is divided into four chambers, two upper chambers called the right and left atria and two lower chambers called the right and left ventricles (Figures 1A,B,C)
The left ventricle of the heart pumps blood through the aortic valve into the aorta, the largest artery of the body, and then through a network of arteries to the whole body
The heart valves control the direction of flow of blood through the heart. After passing through the tissues of the body, the blood collects into the veins and returns to the right atrium
Blood then passes through the tricuspid valve into the right ventricle. The right ventricle pumps the blood through the pulmonary valve into the arteries of the lungs where the blood picks up oxygen and gives up carbon dioxideThe oxygenated blood returns to the left atrium after which it passes through the mitral valve to the left ventricle and the cycle repeats
Like all tissues in the body, the, heart requires oxygen filled blood in order to function
Blood nourishes the heart through the right and left coronary arteries- The left main coronary artery gives off two major branches, the circumflex and left anterior descending artery (Figure 2)
- The right coronary artery gives off the marginal artery before it continues as the posterior descending artery (Figure 3)
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Figure 1a - The heart viewed from in front showing the position of the right and left atria and ventricles. | Figure 1b
- Diagram of the atria, ventricles and valves of the heart with the heart muscle relaxed (diastole). The yellow arrows show the direction of blood flow through the valves |  | | Figure
1c - Diagram of the heart during a contraction of the heart muscle (systole). The yellow arrows show the direction of blood flow through the valves |  |  | | Figure 2 Angiogram of the left coronary artery. Courtesy K. Patel, MD | Figure 3 - Angiogram of the right coronary artery. Courtesy K. Patel, MD |
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