Coronary heart disease, the leading cause of death in the United States, is a narrowing of the coronary arteries, the vessels that supply blood to the heart muscle. Physical activity increases the oxygen needs of the body, and the heart responds to the greater demand by pumping blood more vigorously, which in turn increases the oxygen needs of the heart muscle.

In coronary heart disease, (sometimes called coronary artery disease), narrowed coronary arteries limit the supply of blood to the heart muscle. If narrowing is not extensive, difficulties may occur only during physical exertion, when the narrowed arteries are unable to meet the increased oxygen requirements of the heart. However, as coronary heart disease worsens, the narrowed arteries may starve the heart muscle of oxygen during periods of normal activity, or even at rest.

Coronary heart disease is generally due to the buildup of plaques in the arterial walls, a process known as atherosclerosis. Plaques are composed of cholesterol-rich fatty deposits, collagen, other proteins, and excess smooth muscle cells. Atherosclerosis, which usually progresses very gradually over a lifetime, thickens and narrows the arterial walls, impeding the flow of blood. Blood clots form more easily on arterial walls roughened by plaque deposits. The clots may block the narrowed coronary artery completely and cause a heart attack. Arteries may also narrow suddenly as a result of an arterial spasm. (Spasms are most commonly triggered by smoking.)

Symptoms of coronary heart disease usually develop insidiously. In the early stages of coronary heart disease, there are generally no symptoms. As the coronary heart disease progresses, chest pain (angina pectoris) may develop during periods of physical activity or emotional stress, because the narrowed arteries cannot supply the heart with the increased amount of blood and oxygen necessary at those times.

Angina usually subsides quickly with rest, but over time, symptoms arise with less exertion, and coronary heart disease may eventually lead to a heart attack. However, in a third of coronary heart disease cases, angina never develops, and a heart attack can occur suddenly with no prior warning.

Although coronary heart disease can be a life-threatening condition, the outcome of the disease is in many ways up to the patient. Damage to the arteries can be slowed or halted with lifestyle changes, including smoking cessation, dietary modifications, and regular exercise, or by medications to lower blood pressure and cholesterol levels. Additional goals of treating coronary heart disease, which may involve medication and sometimes surgery, are to relieve symptoms, improve circulation, and prolong life.

Symptoms of Coronary Heart Disease

• No symptoms in the early stages of coronary heart disease.

• Angina (chest pain), or milder pressure, tightness, squeezing, burning, aching, or heaviness in the chest, lasting from 30 seconds to five minutes. The pain or discomfort is usually located in the center of the chest just under the breastbone, and may radiate down the arm (usually the left), up into the neck, or along the jaw line. The pain is generally brought on by exertion or stress and stops with rest. The amount of exertion required to produce angina is reproducible and predictable.

• Shortness of breath, dizziness, or a choking sensation, accompanying angina.

• A sudden increase in the severity of angina, or angina at rest, is a sign of unstable angina that requires immediate medical attention because a heart attack may shortly occur.

What Causes Coronary Heart Disease?

• Smoking promotes the development of plaque in the arteries. Also, by increasing the amount of carbon monoxide in the bloodstream and decreasing the amount of oxygen available to the heart, smoking increases the likelihood of angina.

• High blood cholesterol levels lead to coronary heart disease. LDL (low-density lipoprotein) enters the lining of the arterial walls where, after being chemically altered, its cholesterol can be incorporated into plaque.

• High blood pressure predisposes one to coronary heart disease.

• People with diabetes mellitus are at greater risk for atherosclerosis.

• Obesity may promote atherosclerosis.

• Lack of exercise (a sedentary lifestyle) may encourage atherosclerosis.

• Men are at greater risk than women for coronary heart disease, although the risk for postmenopausal women approaches that of men as estrogen production decreases with menopause.

• Women over age 35 who take oral contraceptives and smoke cigarettes have a higher risk of atherosclerosis.

• A family history of premature heart attacks is associated with greater risk of coronary heart disease.

• A spasm of the muscular layer of the arterial walls may cause an artery to contract and produce angina. Spasms may be induced by smoking, extreme emotional stress, or exposure to cold air.

Prevention of Coronary Heart Disease

• Don’t smoke.

• Eat a diet low in saturated fat, cholesterol, and salt.

• Pursue a program of moderate, aerobic exercise for a minimum of 30 minutes, at least three days a week. People over age 50 who have led a sedentary lifestyle should check with a doctor before beginning an exercise program.

• Lose weight if you are overweight.

• See your doctor regularly to have your blood pressure and cholesterol levels measured, and, if elevated, treated.

• Your doctor may advise you to take a low dose of aspirin every day if you are at high risk for coronary heart disease. Aspirin reduces the tendency for the blood to clot, thereby decreasing the risk of heart attack. However, such a regimen should only be initiated under a doctor’s recommendation.

Diagnosis of Coronary Heart Disease

• Patient history and physical examination. If you suffer a heart attack, diagnosis will often be made upon examination by a doctor or emergency medical technician.

• An electrocardiogram (ECG) may be performed to measure changes in the electrical activity of the heart resulting from abnormalities in the flow of blood or a prior heart attack.

• Chest x-rays.

• Blood tests.

• Stress testing. Blood pressure, heartbeat, and breathing rates are measured by ECG while you walk on a treadmill. If you cannot exercise adequately, a medication may be injected instead.

• An injection of a radioisotope such as thallium may be given after an exercise test to gauge blood flow to the heart.

• An echocardiogram, which uses ultrasound waves to create moving images of the heart, may be performed.

• A coronary angiography is performed to determine the presence of narrowings of the coronary arteries. In this procedure a tiny catheter is inserted into an artery of a leg or arm and threaded up into the coronary arteries. A contrast material is then injected from the end of the catheter into the coronary arteries, and x-rays are taken.