What is Coronary Artery Bypass Surgery?
Coronary Arteries are the vessels that supply the heart muscle with oxygen rich blood. Sometimes these arteries become blocked or significantly narrowed, allowing less blood to be delivered to the cardiac cells. When the heart muscle cannot get enough blood, the cells can be injured or die. If a large enough area of these cardiac muscle cells die, the heart will lose the ability to pump blood. In order to keep the cardiac muscle supplied with blood it may be necessary for a cardiac surgeon to create a detour around the blockage in the coronary arteries. This is done with a bypass graft. The graft is attached to the aorta on the upstream end and to the artery below the blockage so that the blood can flow to the heart muscle. This procedure is called a coronary artery bypass graft.
There are a few materials that can be used to fashion the bypass graft, or conduit. The following are some examples.
Example Materials Used in Coronary Artery Bypass Surgery
Venous conduits are veins that are used as bypass grafts. They are usually removed from elsewhere in the patient’s body for use in the heart. The most common vein used for bypass is the greater saphenous vein which is found along the inside portion of the legs. Since the legs have so many veins to bring blood back to the heart, surgeons can borrow one to use as the conduit. Heart Disease is a progressive condition. By providing new vessels or bypass grafts in the heart, a person has excellent blood flow to the heart muscle. But, coronary artery disease will often progress. That is why the new bypasses are likely to become blocked or narrowed if the patient’s lifestyle remains the same. In some cases as years pass these venous conduits can themselves become narrowed and blocked.
Arteries are those vessels that carry the oxygen rich blood from the heart to other cells in the body. Arteries can also be used as conduits for bypass surgery. The typical arteries used in bypass surgery include the right and left internal mammary arteries and the radial arteries. The mammary arteries run under the breastbone and are very good conduits. Since the mammary arteries already lie close to the heart, one end of the artery can usually be left in place when using them to bypass blocked sections in the coronary arteries. The other end can then be sewn into the coronary artery below the blocked or narrowed section. The radial artery, found in the forearm, runs from the elbow to the thumb and may also be used as a conduit. When these arteries are removed from their original site, other smaller arterioles expand to provide adequate blood flow. This is called collateral circulation.
Arteries tend to have a longer patency rate than veins when used as bypass grafts. This means that they stay open, without blockages or narrowing for a longer time, on average, than venous conduits. This is one of the reasons that here at IHI we generally try to use arterial conduits whenever possible.
Occasionally none of the body’s own vessels are appropriate to be used as conduits. In such cases it is possible to use artificial conduits made of Dacron or other materials to transport the blood. Since artificial conduits have a greater chance of narrowing and becoming blocked they are only used when other choices are not available.
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