By Stephanie Trelogan, MS

Reviewed by Christopher Friedrich, MD,PhD and Andy Avins, MD
Last updated September 12, 2000

The coronary arteries serve as the main blood supply for the heart muscle, which requires oxygen and other nutrients in order to function. Coronary artery disease (CAD) occurs when these arteries become narrowed or clogged. When the heart doesn't get enough oxygen, the muscle becomes injured, which usually causes chest pain called angina. If untreated, CAD can progress to the point where the coronary arteries are completely blocked, cutting off the heart's blood supply. This is what is commonly known as a heart attack, or in medical terminology, a myocardial infarction.

You may have encountered the term coronary heart disease (CHD), which occurs when CAD results in permanent damage to the heart muscle. CHD and CAD are often used interchangeably; here, we will use CAD as a blanket term for both conditions.

What Are Blood Vessels Made of?

Blood vessels are tubes that transport blood throughout the body. All blood vessels have an inner lining called the endothelium, which is surrounded by connective tissue and thin layers of muscle. Although these muscles are not under our voluntary control, they play an important role in determining blood pressure. The tone of these muscles can be affected in the short term by exertion or excitement, and in the long term by factors such as smoking and diabetes.

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What Causes CAD?

CAD is caused by a narrowing of coronary arteries, called atherosclerosis. Blood flow becomes more and more restricted as the artery continues to narrow.

Most commonly, atherosclerosis results when cholesterol and fat circulating in the bloodstream build up on the artery walls. The triggering event is an injury to the artery's inner lining; the injury can be caused by high blood pressure, diabetes, or other causes. The body's immune system responds to the injury, causing inflammation. Immune cells called macrophages are activated and try to heal the injury. This process creates a plaque within the artery wall made up of low density lipoprotein (LDL cholesterol), other fats, and macrophages.

Some plaques are hard; others have just a thin cap on top of a soft, fatty core. If the cap ruptures, the underlying core will be exposed to the blood, triggering the formation of a blood clot. If the blood clot is large enough, blood flow in the artery will be completely blocked. This is what causes a heart attack.

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Signs and Symptoms

Symptoms of CAD can range widely, from no symptoms at all, to mild intermittent chest pain, to pronounced and steady pain. In some people, symptoms can be severe enough to hinder their normal daily activities. A person experiencing angina may feel heaviness, tightness, pain, burning, pressure, or squeezing, usually behind the breastbone but sometimes also in the arms, neck, or jaws. These sensations are usually localized to the left side of the body. Angina is often accompanied by shortness of breath, and sometime by nausea and sweating. These symptoms are usually brought on by exertion and relieved by rest. Nevertheless, some people (especially diabetics) have heart attacks without ever experiencing any of these symptoms.

According to the American Heart Association, the most common warning signs include:

• Uncomfortable pressure, fullness, squeezing, or pain in the center of the chest that lasts more than a few minutes, or goes away and comes back
• Pain that spreads to the shoulders, neck or arms
• Chest discomfort with lightheadedness, fainting, sweating, nausea, or shortness of breath

Less common warning signs include...

• Any chest pain unlike the pain described above
• Stomach or abdominal pain
• Nausea or dizziness (without chest pain)
• Shortness of breath and difficulty breathing (without chest pain)
• Unexplained anxiety, weakness, or fatigue
• Palpitations, cold sweat, or paleness

Not all patients experiencing these symptoms have CAD. However, if you experience these symptoms, you should consult your doctor for further evaluation.

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Factors That Increase Risk

Your risk of developing CAD is a factor of both your genes and your environment. Studies of identical twins have revealed just how important it is to consider both genes and environment when assessing your risk of developing CAD. Even if you are genetically predisposed to develop CAD, a healthy lifestyle may allow you to live to old age without ever experiencing symptoms. Similarly, just because there is no CAD in your family doesn't guarantee that you won't develop it yourself. Most people develop CAD after the age of 45 (in men) or 55 (in women). However, your risk increases if you have a family member who had CAD before age 50, or if you have ever had chest pain, heart attack, stroke, or other vascular diseases. ( For news about environmental factors that increase risk, see Related News below.)

Although there is nothing you can do to change your family history of CAD, you can control your environmental (nongenetic) risk factors, including:

• Smoking. The worst thing you can do for your heart is smoke. The risk of heart attack is twice as high for smokers as for nonsmokers, and smokers who suffer a heart attack are more likely to die within an hour of the attack. The good news is, no matter how long or how much you've smoked, your risk of CAD will rapidly decline as soon as you quit smoking. It's never too late to stop smoking.
• High cholesterol levels. Higher cholesterol levels increase the risk of CAD because cholesterol builds up on artery walls. Adults over 35 years of age should have their cholesterol levels measured at least once every five years. If your parents developed CAD before age 50, you should begin cholesterol screening earlier. Although there is a genetic component to how much cholesterol is in your blood, you can control it to some extent by exercising regularly and eating a diet low in cholesterol and saturated fat. If necessary, you can also take medications to help manage your cholesterol.
• High blood pressure. High blood pressure can also increase your risk for heart attack. Often blood pressure can be kept under control by limiting salt intake, exercising regularly, avoiding excessive alcohol intake, and maintaining a healthy weight. For high blood pressure that doesn't respond to these measures, medication can keep it within healthy limits.

Click above to view weight index table The body mass index is used to assess a person's body weight relative to height. It's a useful, indirect measure of body composition, because it correlates highly with body fat in most people.

• Obesity and inactivity. People who are too heavy for their height more likely to develop CAD, even with no other risk factors. This is because extra weight increases blood pressure and cholesterol, both of which are CAD risk factors.

• Diabetes. Diabetes can make CAD worse in many different ways. High blood glucose can cause elevated levels of blood fats and cholesterol, promote injury to the inside of blood vessels, and affect the immune system.

More on Diabetes

• Stress. Most doctors believe that high levels of stress can also increase the risk of CAD. This is difficult to prove because there is no way to accurately measure how much stress a person has, or even how stress affects a person. However, research has indicated that managing stress may profoundly reduce the risk of CAD.

Although these environmental risk factors increase every person's chance of developing CAD, they put you at particular risk if you also have family members with CAD.

• Other people in your family have developed CAD early in life (i.e., before age 45 in men or before age 55 in women)
• Multiple people in your family have or have had CAD
• A genetic syndrome or familial diagnosis has been identified in your family

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Screening

Because symptoms can vary widely, there is no one simple test for CAD. Your doctor will always begin by taking a careful medical history and performing a thorough physical exam. The history and physical exam are extremely sensitive and specific tests for determining whether symptoms are due to CAD. If the history and physical exam suggest CAD, then your doctor may then use a combination of diagnostic procedures to measure the extent and severity of any CAD, and to rule out other possible causes of symptoms. (For recent news about screening, see Related News below.)

• An electrocardiogram (ECG or EKG) records the heart's electrical activity as it contracts and rests. An EKG can detect abnormal heart beats, areas of heart muscle damage, inadequate blood flow, and enlargement of the heart.
• A stress test (also called a treadmill test) can be useful because some problems only show up when the heart is working hard and oxygen demands are higher. In a stress test, an EKG is recorded before, during, and after exercise. Another type of stress test employs echocardiography during exercise to allow the doctor to visualize how the heart performs under stress.
• Nuclear scanning can identify regions of the heart in which blood flow is limited. A small amount of radioactive material is injected into a vein, usually in the arm. The amount of nuclear material that is taken up by heart muscle is then recorded using a scanning camera. Areas with decreased blood flow will take up less radioactive material than areas with normal blood flow.
• Cardiac catheterization (or coronary angiography) is the most definitive test for CAD. A long, thin tube is inserted into a major artery in leg or arm and then threaded all the way into the coronary arteries. A special dye is injected through this catheter and a series of x-rays are taken. The dye is visible on the x-ray, so it is possible to determine if a blockage is present and how serious it is. This test allows doctors to see blockages in the coronary arteries, but since it is more risky, the other tests are usually performed first.

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Treatments

Your best bet is to prevent CAD before it starts. But even after its onset, CAD can often be managed with a number of lifestyle changes and medications. In more severe cases, invasive interventions, such as surgery or balloon angioplasty, may be required.

• Stop smoking. If you've recently been diagnosed with CAD and you smoke, the most important thing is to stop smoking.
• A healthy diet low in cholesterol and fat (especially saturated fat) can help reduce blood cholesterol levels. Studies have shown that extremely low-fat diets may actually reverse the progress of CAD. Furthermore, some oils, including fish oil and olive oil, may actually be beneficial. And several studies have shown that drinking red wine in moderation may also reduce your risk. Eating less fat should also help you lose weight. If you are overweight, losing weight can help reduce high blood pressure, another risk factor for atherosclerosis and heart disease.
• Physical exercise is a great way to help lose weight, lower blood pressure, and increase levels of HDL (the "good" cholesterol). However, if you already have CAD, be sure to check with your doctor before beginning any exercise program.
• Medications can be prescribed to manage different aspects of CAD. A variety of medications (beta-blockers, nitroglycerine, and calcium channel blockers) can control symptoms of angina. Aspirin reduces the tendency to form blood clots. Cholesterol can be controlled using a variety of medications, especially statins (HMG Co-A reductase inhibitors). Medications can also be helpful for managing high blood pressure.
  
  For recent news about medications for CAD, see Related News below.
• Coronary angioplasty can break open blockages in the coronary arteries. A cardiologist inserts a catheter with a tiny balloon at its tip through an arm or leg vein, and then threads it into the coronary artery. The balloon is inflated and deflated to improve the passage for blood flow. The catheter is removed, but a device called a "stent" is often inserted to keep the artery open.
• Coronary bypass surgery is the most definitive treatment. In this operation, a blood vessel taken from the leg or chest is grafted onto the coronary artery, bypassing the blockage. Depending on how many arteries are blocked, surgeons may need to perform more than one bypass.

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Related News

In order to view these articles you will need to have a MyGeneticHealth account. If you are not already a member, selecting the article will automatically take you to a page where you can sign up. Diet equal to drug in lowering cholesterol Oats, vitamin E open arteries after fatty meal Self test helps patients monitor cholesterol Heart scans work as well as treadmill stress test Consumption of filtered coffee does not increase cholesterol levels Margarine better than butter, but genes play a role Lifestyle contributes to heart disease risk Heart association says soy lowers cholesterol Vitamin E may reduce heart attack risk Slower rate of ethanol metabolism more cardioprotective Depression ups heart disease risk Higher dietary intake of B vitamins associated with decreased cardiovascular risk Hormone therapy reduces risk of arterial disease

References

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Eds. Cotran, R. S., et al. (1999). Robbins' Pathologic Basis of Disease, 6th ed.. Philadelphia: Saunders.

Katan, M.B., et al. (1995).Dietary Oils, Serum Lipoprotein, and Coronary Heart Disease. American Journal of Clinical Nutrition. 61(6Suppl):1368S-1373S.

Kushi, L.H., et al. (1995). Health Implications of Mediterranean Diets in Light of Contemporary Knowledge. 2. Meat, Wine, Fats, and Oils. American Journal of Clinical Nutrition. 61(6Suppl):1416S-1427S.

Ornish, D., et al. (1998.) Intensive Lifestyle Changes for Reversal of Coronary Heart Disease. JAMA. 280(23):2001-2007.

Rozanski, A., et al. (1999). Impact of Psychological Factors on the Pathogenesis of Cardiovascular Disease and Implications for Therapy. Circulation. 99(16):2192-2217.

Samuels, L.E., et al. (1999). Coronary Artery Disease in Identical Twins. Annals of Thoracic Surgery. 68(2):594-600.

Stone, N.J. (1996). Fish Consumption, Fish Oil, Lipids, and Coronary Heart Disease. Circulation. 94(9):2337-2340.