Narrowing of the coronary arteries that supply the heart muscle with blood, leading to heart damage
- More common with increasing age
- More common in males until the age of 60, then equal incidence
- Sometimes runs in families
- Smoking, a high-fat diet, lack of exercise, and excess weight are risk factors
The coronary arteries, which branch from the main artery in the body, the aorta, supply the heart muscle with oxygen-rich blood. In coronary artery disease (CAD), also known as coronary heart disease, one or more of the coronary arteries is narrowed. Blood flow through the arteries is restricted, which can lead to heart muscle damage. Heart disorders, including heart attacks (see Myocardial infarction) and the chest pain of angina, are usually caused by CAD. This condition is therefore a leading cause of death in many developed countries. The number of deaths from CAD reached its peak in the UK in the late 1970s, with about 85 people per 100,000 dying each year. The death rate from CAD has since fallen by more than half as a result of health education about smoking and diet and the introduction of more effective treatments. However, in many parts of the world, including some developing countries, mortality from CAD is rising as a result of changing lifestyle factors.
What are the causes?
Coronary artery disease is usually due to atherosclerosis, a condition in which fatty deposits accumulate on the inside of the artery walls. These deposits narrow the arteries and restrict blood flow. If a blood clot forms or lodges in the narrowed area of an artery, the vessel can become completely blocked. CAD caused by atherosclerosis is more likely if your blood cholesterol level is high and you eat a high-fat diet. CAD is also linked to smoking, obesity, lack of exercise, diabetes mellitus, and high blood pressure (see Hypertension).
In premenopausal women, the risk of CAD is lower, possibly because of the effects of the female hormone oestrogen. After the menopause, oestrogen levels fall, and by the age of 60 women have the same risk of developing CAD as men, although their mortality remains lower. Hormone replacement therapy (HRT) does not reduce mortality from CAD in postmenopausal women and is likely to increase the risk of certain cancers.
Rarely, the coronary arteries are narrowed by inflammation, which may be due to the autoimmune disorder polyarteritis nodosa or Kawasaki disease, which affects children. Temporary narrowing can be caused by spasm in the artery wall, which, in rare cases, may cause a heart attack.
What are the symptoms?
In the early stages of CAD, there are often no symptoms. In the later stages of CAD, the first symptom is usually either pain in the chest on exertion, a condition known as angina, or a heart attack. Some people with CAD develop an abnormality of the heart rhythm (see Arrhythmias), which may cause palpitations (awareness of heartbeats), light-headedness, and, sometimes, loss of consciousness. Some severe forms of arrhythmia can cause the heart to stop pumping completely (see Cardiac arrest), which accounts for most of the sudden deaths from CAD.
In elderly people, CAD may lead to a condition called chronic heart failure, in which the heart gradually becomes too weak to provide an adequate circulation of blood around the body. Chronic heart failure may then lead to the accumulation of excess fluid in the lungs and tissues, causing additional symptoms such as shortness of breath and swollen ankles.
How is it diagnosed?
CAD is usually diagnosed only when a person develops symptoms of the disease. Sometimes, a heart attack is the first sign. If you have symptoms such as chest pain, your doctor may arrange a series of tests to detect and establish the severity of the problem. These tests include an ECG to monitor the heart’s electrical activity and radionuclide scanning to show whether the blood supply to the heart muscle is adequate. You may have exercise testing to see how the heart performs under stress, and echocardiography, an ultrasound technique that images the heart muscle and valves. The imaging techniques of high-resolution CT scanning and MRI are increasingly used to detect heart and coronary artery abnormalities.
If these tests suggest that the blood supply to your heart is inadequate, you may be referred for coronary angiography, in which a dye is injected into the bloodstream to enable arteries to be seen on an X-ray. Angiography detects blocked or seriously narrowed sections of an artery and provides your doctor with the information needed to decide whether surgical treatment is required.
What is the treatment?
Treatment for CAD falls into three categories: lifestyle changes and protective drug treatment – for example, with lipid-lowering drugs – to reduce the risk of CAD becoming worse; drug treatments to improve the function of the heart and help to relieve symptoms; and surgical procedures, such as coronary angioplasty, that improve the blood supply to the heart muscle.
If you are diagnosed as having CAD, you should adopt a healthier lifestyle, with a low-fat diet and regular exercise. If you smoke, you should stop.
The drugs used to treat CAD depend on your symptoms and their severity and on the cause of the disorder. If tests show that you have a high blood cholesterol level, you will be treated with lipid-lowering drugs. These drugs are usually prescribed even if you eat a diet low in fat and your cholesterol levels are within the acceptable range. This is because treatment with lipid-lowering drugs slows the progression of CAD and, as a consequence, reduces the risk of a heart attack.
Angina may be treated with drugs, such as nitrate drugs and beta-blocker drugs, that improve the blood flow through the arteries and help the heart to pump effectively. Other drugs that may be used to treat angina include calcium channel blockers, which relax the arteries and thereby improve blood flow, andivabradine, which slows the heart rate and so reduces the heart’s oxygen and energy requirements. An abnormal heart rhythm is often treated using antiarrhythmic drugs.
If treatment fails to relieve the symptoms or if there is extensive narrowing of the arteries, your doctor will discuss several other treatment options with you. If only small segments of the artery are affected, you may be offered coronary angioplasty and stenting, in which a balloon is inflated in the narrowed area of the affected blood vessel to widen it. During the procedure, a stent (a tubular scaffold device) will usually be inserted into the affected artery to keep it open. Alternatively, your doctor may suggest a coronary artery bypass graft. In this procedure, blockages in one or more coronary arteries are bypassed using an artery on the inside of the chest wall or veins taken from a leg.
What is the prognosis?
Coronary artery disease affects people in middle to old age and is more easily prevented than treated. The chance of developing the disease can be reduced by following a healthy lifestyle. More efficient methods of diagnosing CAD and screening for risk factors also make it possible to begin treatment early in the course of the disease. Effective drugs to prevent the progression of CAD and the success of both coronary angioplasty and bypass grafting have greatly improved the prognosis for CAD.
For an individual with CAD, the outlook depends on the number of blood vessels involved and how extensively the heart muscle is damaged.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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