Coronary artery disease (CAD), 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 CAD, 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 the disease worsens, the narrowed arteries may starve the heart muscle of oxygen during periods of normal activity, or even at rest.
Coronary artery 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 artery disease usually develop insidiously. In the early stages of the disease, there are generally no symptoms. As the 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 CAD may eventually lead to a heart attack. However, in a third of CAD cases, angina never develops, and a heart attack can occur suddenly with no prior warning.
Although CAD 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 treatment, which may involve medication and sometimes surgery, are to relieve symptoms, improve the circulation, and prolong life.
What Causes Coronary Artery 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 artery 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 CAD.
- 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 artery 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 CAD risk.
- 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.
Symptoms of Coronary Artery Disease
- No symptoms in the early stages of coronary artery disease.
- Chest pain (angina), 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, nausea, dizziness, or a choking sensation, accompanying chest pain
- 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.
Prevention of Coronary Artery 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 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 CAD. 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 Artery Disease
- Patient history and physical examination are performed. 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.
- Positron emission tomography (PET) scan may be used to detect damage to heart muscle, determine if areas of the heart are alive and functioning and determine if the heart is getting enough blood to keep the heart muscle healthy.
- Chest x-rays
- Blood tests
- Stress testing is performed. In this test, 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 to simulate the effect of exercise on the heart 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.
- Nuclear stress test (also called an exercise thallium test) involves injecting a radioactive substance into the bloodstream to show how blood is flowing through the arteries.
- 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.
How to Treat Coronary Artery Disease
- Emergency treatment and immediate hospitalization is necessary if a heart attack occurs—commonly signaled by crushing, persistent chest pain.
- Follow prevention tips for a heart-healthy lifestyle, including a low-fat diet and regular physical exercise. Avoid excessive alcohol consumption, nasal decongestants, and diet pills, all of which may raise blood pressure.
- Rapidly acting nitrates, such as nitroglycerin, or longer-acting nitrates like isosorbide dinitrate may be prescribed to dilate blood vessels and relieve or prevent symptoms of angina. A nitroglycerin tablet placed under the tongue (sublingually) at the onset of an angina attack usually relieves the pain within minutes. Sublingual nitroglycerin may also be taken just prior to activities that commonly provoke angina. However, for any given angina attack, you should not take more than three nitroglycerin tablets at five-minute intervals—pain lasting longer than this may signal a heart attack. Intravenous nitrates may be administered in patients with unstable angina. Nitrates may also be prescribed in the form of patches, sprays, or ointments to provide continuous protection.
- Beta-blockers such as propranolol or metoprolol are prescribed to reduce the heart’s oxygen demand by slowing the heart rate and lowering blood pressure.
- ACE inhibitors such as enalapril may be prescribed to reduce blood pressure and dilate blood vessels.
- Calcium channel blockers such as verapamil, diltiazem or nifedipine may be prescribed to reduce the heart’s oxygen demands and to increase coronary blood flow.
- Anticoagulants such as heparin or warfarin will be administered to reduce the risk of blood clots in patients with unstable angina.
- Vasodilators such as captopril, enalapril or hydralazine may be prescribed to expand blood vessels, thus reducing blood pressure and facilitating blood flow.
- An obstructed coronary artery may be opened with percutaneous transluminal coronary angioplasty (PTCA). In this procedure a small balloon is inserted into the circulatory system via a catheter and guided to the site of an arterial blockage. The balloon is then inflated, compressing the plaque, widening the passageway, and improving blood flow. Often, a stent is then placed in the artery to help keep it open. PTCA usually requires a hospital stay of only a few days.
- Coronary bypass surgery may be performed to improve blood flow to the heart. A mammary artery or a vein taken from the leg is grafted onto the damaged coronary artery to circumvent a narrowed or blocked portion.
- A heart transplant may be advised in severe cases in which the heart muscle has been badly damaged. The survival rate for heart transplant is 80 percent after one year and 63 percent after four years.
- Transmyocardial laser revascularization (TMR) is a new procedure that can help relieve severe angina or coronary artery disease in patients who are unable to undergo bypass surgery or angioplasty.
When to Call a Doctor
- EMERGENCY Call an ambulance if you experience crushing chest pain, with or without nausea, vomiting, profuse sweating, shortness of breath, weakness, or intense feelings of dread.
- EMERGENCY Call an ambulance if chest pain from previously diagnosed angina does not subside after 10 to 15 minutes.
- EMERGENCY Call an ambulance the first time you experience intense chest pain.
- See your doctor if attacks of previously diagnosed angina become more frequent or more severe or occur at rest.
Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference
Simeon Margolis, M.D., Ph.D., Medical Editor
Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50
Updated by Remedy Health Media