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Heart and Cardiovascular System |
Improving the heart's blood supply
FROM MAYO CLINIC
To get somewhere that's blocked off, you bypass the problem — you take a detour. The same principle applies when the arteries that supply blood to your heart become blocked. A detour may be necessary. That's why some 500,000 coronary artery bypass surgeries are done each year in the United States.
Since its introduction in the late 1960s, coronary bypass surgery has become one of the most common surgeries performed in this country. It's also generally very safe. Not only can bypass surgery improve quality of life, but it may also prolong life when combined with heart-healthy lifestyle changes and perhaps drug therapy to help lower cholesterol.
Coronary artery disease sets the stage for coronary bypass surgery. The disease results from atherosclerosis (ath-ur-o-skluh-RO-sis) — the slow, progressive buildup of hardened deposits (plaques) on the inner walls of your arteries. The plaques are composed of several substances, including fats, cholesterol and calcium.
When plaques accumulate inside the arteries that serve the heart (coronary arteries), the flow of oxygen-rich blood to heart muscle is impaired. This restriction of oxygen is called ischemia (is-KEE-me-uh).
Eventually, impaired blood flow in the coronary arteries may cause chest pain or pressure (angina pectoris) that may be brought on by stress or physical exertion. Should a complete blockage occur, a heart attack can result.
Once coronary artery disease is diagnosed, treatment generally includes lifestyle changes (such as diet and exercise) and medications to lower cholesterol and blood fats. Depending on the extent of the disease, coronary bypass surgery or other procedures may also be recommended. Bypass surgery is generally done if any of the following is true:
· There's increasing or debilitating angina and several coronary arteries are impaired
· Several coronary arteries are impaired and the heart's main pump (the left ventricle) is functioning poorly
· The left main coronary artery (which serves the left ventricle) is blocked
Coronary bypass surgery generally takes between 3 and 6 hours and requires general anesthesia. On average, about three coronary arteries are bypassed during the surgery, although sometimes as many as six or seven bypasses may be done.
The majority of coronary bypass surgeries are still done conventionally — meaning a chest incision is made so that the rib cage can be opened to expose the heart.
Typically, a heart-lung machine (cardiopulmonary bypass pump) is used. This machine takes over the function of the heart and lungs. It allows your heart to be stopped while a surgeon sews in place replacement blood vessels (grafts) that provide detours for blood flow around blocked coronary arteries.
The blood vessel grafts are obtained from other arteries and veins in your body. Typically, an artery already present in your chest — the internal thoracic artery (also called the internal mammary artery) — is used. It's diverted from your chest wall and one end is attached to a diseased coronary artery beyond the blockage.
Graft segments are also created from the long vein — the saphenous (sa-FUH-nus) vein — that runs just beneath the surface of your leg. The vein grafts are connected on one end to the main artery supplying blood to your body (your aorta) and on the other end to the blocked coronary artery beyond the point of obstruction. Occasionally, the radial artery (at the wrist) is used as a bypass graft.
Once all the grafts are completed, your heart is restarted and you're taken off the heart-lung machine.
Recently, minimally invasive bypass procedures have been developed. These techniques don't require opening the rib cage.
One technique — minimally invasive direct coronary artery bypass (MIDCAB) — involves making a small incision near the left breast. Sometimes part of the rib overlying the heart is removed. A heart-lung machine is not used in the procedure.
Only the main coronary artery that runs down the front of the heart can be bypassed using MIDCAB. The procedure is limited in use because most people having bypass need several vessels bypassed. Another minimally invasive procedure — port-access coronary artery bypass (PACAB) — is also limited in use to primarily bypassing the heart's main coronary artery.
Of growing interest is performing conventional bypass surgery without stopping the heart. Instead of using the heart-lung machine, a special tool is used to restrain the heart's movement in each area where a vessel is being bypassed.
Study is ongoing to determine whether such bypass surgery is as safe as conventional surgery using the heart-lung machine and whether the long-term results are comparable. Preliminary research indicates that older people who have had bypass surgery without the heart-lung machine have less postoperative confusion during recovery.
Following conventional bypass surgery, you can expect a recovery period of about 6 to 12 weeks. People with more sedentary work often return to work after 6 weeks. If your work is more physical, you may be out for 12 weeks or more.
Most people who have bypass surgery are able to resume normal activities, and 90 percent have a substantial lessening of angina. However, about 40 percent have new blockages within the first 10 years after surgery and may require a second bypass, other procedures or an increase in medication.
Lasers and gene therapy — the future?
Research is ongoing to develop new treatment methods for coronary artery disease. One avenue under study is laser revascularization — using lasers to create new channels for blood flow through the heart muscle itself (arteries are not involved).
Although the channels don't remain open, it's thought by some that the scarring of the heart tissue stimulates the growth of tiny new blood vessels, a process called angiogenesis. The procedure may have a place in treating people with serious angina who haven't been helped with standard treatments.
Research is also under way to determine the value of gene therapy and growth factor proteins in restoring blood flow to the heart by stimulating new blood vessel growth.
Coronary bypass surgery plays an important role in treating coronary artery disease, but it isn't a cure. Surgery can improve symptoms and even prolong life when the left main coronary artery or multiple vessels are bypassed, but it doesn't get rid of the disease.
With the guidance of your doctor, aggressive coronary artery disease management is still necessary following surgery. If you smoke, it's imperative that you stop.
Controlling high blood pressure can reduce the workload on your heart. And lowering cholesterol with diet, exercise and perhaps lipid-lowering medications can help prevent further blockages that may be more difficult to treat. Treating your LDL ("bad") cholesterol to get it lower than 100 becomes the target if you've had coronary artery disease or bypass.
Research is ongoing to develop new treatment methods for coronary artery disease. One avenue under study is laser revascularization — using lasers to create new channels for blood flow through the heart muscle itself (arteries are not involved).
Although the channels don't remain open, it's thought by some that the scarring of the heart tissue stimulates the growth of tiny new blood vessels, a process called angiogenesis. The procedure may have a place in treating people with serious angina who haven't been helped with standard treatments.
Research is also under way to determine the value of gene therapy and growth factor proteins in restoring blood flow to the heart by stimulating new blood vessel growth.