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Coronary Artery Disease

Coronary artery disease (CAD), also known as coronary heart disease (CHD) or coronary atherosclerosis, involves the progressive narrowing of the arteries that nourish the heart muscle. Often there are no symptoms, but if one or more of these arteries become severely narrowed, angina may develop during exercise, stress, or other times when the heart muscle is not getting enough blood.

Cause
Coronary Arteries and Cardiac Veins - Diaphragmatic Surface

The narrowing is due to a buildup of fatty plaque (atherosclerosis) along the artery walls. These deposits are composed mostly of cholesterol, other lipids, and fibrous tissue, such as collagen. Coronary disease appears to be a lifelong process in some people, beginning at an early age and progressing slowly until the vessels become so occluded that the heart muscle no longer gets adequate nourishment. The underlying cause is unknown, although it is seen most frequently in people who live in developed industrialized nations.

  
Diagnosis
Right Coronary Artery - Arteriographic View

A coronary artery must be narrowed to less than 30% of its original size before there is a serious reduction in the blood flow to the heart muscle served by that vessel. Generally, about 5% of the total cardiac output of blood goes through the coronary arteries; thus there is adequate coronary blood flow to meet normal demands at rest even if the vessels are 70 to 90% occluded. If the coronary arteries are seriously blocked, however, blood flow may not be adequate for any increased demand, such as that of exercise or an emotional upset. If the heart muscle cannot get enough oxygen—a state known as myocardial ischemia—symptoms such as chest pain (angina) or shortness of breath may result.
Left Coronary Artery - Arteriographic View

A presumptive diagnosis of coronary disease is based on a review of symptoms, health history, an electrocardiogram, and an exercise stress test, perhaps with a thallium scan. A more definitive diagnosis requires cardiac catheterization and angiography.

During an exercise stress test, the patient is hooked up to an electrocardiographic monitor (an ECG or EKG machine) and then asked to walk on a treadmill, peddle a stationary bicycle, or climb steps. The ECG monitor will show whether the heart muscle is getting enough blood. An exercise test also detects silent ischemia, a condition with no symptoms in which heart muscle does not get enough blood.

If severe narrowing is suspected, a coronary angiogram may be needed. This examination entails threading a catheter through a blood vessel into the heart, and then injecting a dye into the coronary arteries to make them visible on x-rays.

Treatment

Various medications constitute the first-line treatment of coronary artery disease. These include:

Beta-Blocking Drugs: These agents act by blocking the effect of the sympathetic nervous system on the heart, slowing heart rate, decreasing blood pressure, and thereby reducing the oxygen demand of the heart. Studies have found that these drugs also can reduce the chances of dying or suffering a recurrent heart attack if they are started shortly after suffering a heart attack and continued for 2 years.

Calcium-Channel-Blocking Drugs: All muscles need varying amounts of calcium in order to contract. By reducing the amount of calcium that enters the muscle cells in the coronary artery walls, spasms can be prevented. Some calcium-channel-blocking drugs also decrease the work-load of the heart and some lower the heart rate as well.

Nitrates: Nitroglycerin may be prescribed to both treat and prevent attacks of angina.

Surgical Treatment
Coronary Arteries and Cardiac Veins - Sternocostal Surface

Coronary artery bypass surgery. An estimated 170,000 Americans undergo coronary artery bypass surgery each year. This operation, once considered a difficult achievement, is now almost routine in many medical centers. Indeed, there is a good deal of controversy over whether it is now being used unnecessarily to treat coronary disease that could be controlled just as effectively by more conservative, less costly medical therapies.

There remains some disagreement among doctors as to the indications for coronary bypass surgery. Studies have conclusively demonstrated that the operation prolongs life in patients who have a severely blocked left main coronary artery. It is also indicated in most cases in which three major arteries are diseased. There is less agreement about when it is appropriate for other patients. In general, it is recommended for people with disabling angina that cannot be controlled by conventional therapy and who are also good candidates for surgery.

The operation itself is relatively simple. For "on-pump" procedures, circulation is maintained by a heart-lung machine. In an "off-pump" operation, the surgeon operates directly on the beating heart. Most people who undergo the operation report feeling vastly better afterward. Very often, the patient may have suffered from disabling angina or other cardiac limitations before the operation. With an increased blood supply to the heart muscle, these problems should be eliminated or minimized.

It should be noted that not all people with severe coronary disease are suitable candidates for surgery, and also that the operation is not always successful in achieving its intended goals. As with any surgical procedure, the operation involves some risk; nationwide, about 1 to 3% of bypass patients do not survive the operation or recovery period. The risk is highest for people who have heart failure or are debilitated by age or other medical conditions. Women do particularly poorly.

The skill and experience of the surgical and recovery teams also are important considerations. Patients considering coronary bypass surgery always should determine whether the surgeon performs this particular operation regularly (at least 2 or 3 times per week) and whether there is a skilled recovery team and a special recovery unit.

Although bypass surgery greatly improves the way most patients feel, it is not a cure for heart disease. Unless other preventive steps are taken, the processes that caused the artery disease will continue. In fact, the grafts seem to become diseased even faster than the natural coronary arteries. Therefore, it is particularly important for bypass patients to follow a prudent lifestyle following the operation.
Angioplasty
Angioplasty Interactive Animation
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A relatively recent—and increasingly popular—treatment for atherosclerotic arterial diseases is transluminal angioplasty, also referred to as balloon angioplasty. Used to treat severely blocked coronary arteries as well as arteries diseased with atherosclerotic plaque in other parts of the body, this technique involves threading a catheter with an inflatable balloonlike tip through the artery to the area of blockage. The balloon is inflated, flattening the fatty deposits and widening the arterial channel, allowing more blood to reach the heart muscle.

Angioplasty offers several obvious advantages:

    * The operation is performed under local anesthesia.
    * Although invasive, it does not involve surgery or the use of a heart-lung machine.
    * It is not as costly as coronary bypass surgery, nor does it involve more than 1 or 2 days of hospitalization under ordinary circumstances.

Unfortunately, it is not appropriate for all types of coronary artery disease, nor does it work in all people. For example, studies show that women are not as likely as men to benefit from the operation; they also have a higher mortality rate from the procedure. Some studies have put the success rate at about 60 percent; people who undergo an unsuccessful angioplasty still may require coronary bypass surgery. As technology advances, the applicability and success rates of angioplasty may improve. It also should be noted that it is not a cure for the disease. In a significant number of patients, the occlusions recur, and a repeat angioplasty may be required after 2 or 3 years.

Angioplasty is also being used to treat blockages in the arteries of the legs and the carotid artery, the major vessel carrying blood to the brain.

A variation of balloon angioplasty uses a tiny drill-like device to shave away fatty deposits, similar to a Roto-Rooter. Another still experimental variation called laser ablation, is performed through a special viewing tube (fiber-optic catheter) that is inserted into the clogged artery. A laser, an intense beam of light, is used to vaporize the plaque.

Home Remedies and Alternative Therapies

There is no substitute for medical care when considering a serious—even potentially fatal—condition such as coronary heart disease. The first thing to do if you notice any symptoms of a heart problem, including chest pain, is to see your doctor. Medical treatment may be required to prevent heart attack. However, your doctor may recommend nonmedical measures, such as:

    * exercise conditioning,
    * relaxation techniques such as yoga, and
    * a low-fat diet.

These measures may help ease the symptoms of coronary heart disease, especially angina, and may help ease the effects of some risk factors. For example, relaxation techniques may help you overcome stress and block pain impulses by refocusing your concentration. These techniques include meditation, yoga, biofeedback training, and self-hypnosis. For maximum benefit, you should choose a relaxation technique that you are comfortable with and practice it for 20 minutes once or twice a day. In addition to the direct positive effect on your cardiovascular system, relaxation techniques may help you make other lifestyle changes such as stopping smoking and contribute to a general sense of well-being.

Vitamin therapy may also work in conjunction with your medical treatment. High doses of niacin can lower blood cholesterol levels, reducing the buildup of fatty deposits in the arteries. In addition, recent studies indicate that vitamin E, an antioxidant vitamin that also inhibits blood clotting, may help reduce the risk of heart attack. However, do not take any more than the Recommended Dietary Allowance (RDA) of any vitamin without first consulting your doctor; some vitamins in high doses can have toxic effects.

Other more controversial, alternative therapies include garlic, which may be consumed as deodorized pills, and fish oil (omega-3 fatty acid) supplements. Ongoing studies indicate that large amounts of garlic may have a modest cholesterol-lowering effect. Any benefits of fish oil supplements are offset by the increased calorie and fat intake. Thus, experts recommend eating one or two servings of salmon, cod, or other cold-water fish a week rather than taking fish oil pills.

Still other alternative therapies provide no benefit and should be avoided. These include chelation therapy, a technique used to remove heavy metals such as lead from the blood.


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