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Coronary Artery Disease Overview

Illustration of heart arteries

Your heart is a strong muscular pump that is responsible for moving about 3,000 gallons of blood through your body every day. Like other muscles, your heart requires a continuous supply of blood to work properly. Your heart muscle gets the blood it needs to do its job from the coronary arteries.

What is coronary artery disease?

Coronary artery disease is the narrowing or blockage of the coronary arteries, usually caused by atherosclerosis. Atherosclerosis (sometimes called “hardening” or “clogging” of the arteries) is the buildup of cholesterol and fatty deposits (called plaques) on the inner walls of the arteries. These plaques can restrict blood flow to the heart muscle by physically clogging the artery or by causing abnormal artery tone and function.

Without an adequate blood supply, the heart becomes starved of oxygen and the vital nutrients it needs to work properly. This can cause chest pain called angina. If blood supply to a portion of the heart muscle is cut off entirely, or if the energy demands of the heart become much greater than its blood supply, a heart attack (injury to the heart muscle) may occur.

What causes the coronary arteries to narrow?

Coronary arteries narrowing

Your coronary arteries are shaped like hollow tubes through which blood can flow freely. The muscular walls of the coronary arteries are normally smooth and elastic and are lined with a layer of cells called the endothelium. The endothelium provides a physical barrier between the blood stream and the coronary artery walls, while regulating the function of the artery by releasing chemical signals in response to various stimuli.

Coronary artery disease starts when you are very young. Before your teen years, the blood vessel walls begin to show streaks of fat. As you get older, the fat builds up, causing slight injury to your blood vessel walls. Other substances traveling through your blood stream, such as inflammatory cells, cellular waste products, proteins and calcium begin to stick to the vessel walls. The fat and other substances combine to form a material called plaque.

Over time, the inside of the arteries develop plaques of different sizes. Many of the plaque deposits are soft on the inside with a hard fibrous “cap” covering the outside. If the hard surface cracks or tears, the soft, fatty inside is exposed. Platelets (disc-shaped particles in the blood that aid clotting) come to the area, and blood clots form around the plaque. The endothelium can also become irritated and fail to function properly, causing the muscular artery to squeeze at inappropriate times. This causes the artery to narrow even more.

Sometimes, the blood clot breaks apart, and blood supply is restored. In other cases, the blood clot (coronary thrombus) may suddenly block the blood supply to the heart muscle (coronary occlusion), causing one of three serious conditions, called acute coronary syndromes.

Who is affected by coronary artery disease?

Heart disease is the leading cause of death among men and women in the United States. Coronary artery disease affects 16.8 million Americans. The American Heart Association (AHA) estimates that about every 34 seconds, an American will have a heart attack. In addition, the lifetime risk of having cardiovascular disease after age 40 is 2 in 3 men and more than 1 in 2 women.

Reference: Heart Disease and Stroke Statistics 2009 Update: A Report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation. 2009, January 27.

What are acute coronary syndromes?

Unstable angina: This may be a new symptom or a change from stable angina. The angina may occur more frequently, occur more easily at rest, feel more severe, or last longer. Although this can often be relieved with oral medications, it is unstable and may progress to a heart attack. Usually more intense medical treatment or a procedure are required to treat unstable angina.

Non-ST segment elevation myocardial infarction (NSTEMI): This type of heart attack, or MI, does not cause major changes on an electrocardiogram (ECG). However, chemical markers in the blood indicate that damage has occurred to the heart muscle. In NSTEMI, the blockage may be partial or temporary, so the extent of the damage is usually relatively minimal.

ST segment elevation myocardial infarction (STEMI): This type of heart attack, or MI, is caused by a prolonged period of blocked blood supply. It affects a large area of the heart muscle, and causes changes on the ECG as well as in blood levels of key chemical markers.

Although some people have symptoms that indicate they may soon develop an acute coronary syndrome, some may have no symptoms until something happens, and still others have no symptoms of the acute coronary syndrome at all.

All acute coronary syndromes require emergency evaluation and treatment.

Collateral Circulation

collateral circulation

As the size of the blockage in a coronary artery increases, the narrowed coronary artery may develop “collateral circulation.” Collateral circulation is the development of new blood vessels that reroute blood flow around the blockage. However, during times of increased exertion or stress, the new arteries may not be able to supply enough oxygen-rich blood to the heart muscle.

What is ischemia?

Ischemia is a condition described as “cramping of the heart muscle.” Ischemia occurs when the narrowed coronary artery reaches a point where it cannot supply enough oxygen-rich blood to meet the heart’s needs. The heart muscle becomes “starved” for oxygen.

Ischemia of the heart can be compared to a cramp in the leg. When someone exercises for a very long time, the muscles in the legs cramp up because they’re starved for oxygen and nutrients. Your heart, also a muscle, needs oxygen and nutrients to keep working. If the heart muscle’s blood supply is inadequate to meet its needs, ischemia occurs, and you may feel chest pain or other symptoms.

Ischemia is most likely to occur when the heart demands extra oxygen. This is most common during exertion (activity), eating, excitement or stress, or exposure to cold.

When ischemia is relieved in less than 10 minutes with rest or medications, you may be told you have “stable coronary artery disease” or “stable angina.” Coronary artery disease can progress to a point where ischemia occurs even at rest.

Ischemia, and even a heart attack, can occur without any warning signs and is called “silent” ischemia. Silent ischemia can occur among all people with heart disease, though it is more common among people with diabetes.

How is Coronary Artery Disease (CAD) Diagnosed?

Your cardiologist (heart doctor) can tell if you have coronary artery disease by

  • talking to you about your symptoms, medical history, and risk factors
  • performing a physical exam
  • performing diagnostic tests

Diagnostic tests help your doctor evaluate the extent of your coronary heart disease, its effect on the function of your heart, and the best form of treatment for you. They may include:

Other diagnostic tests may include:

Tests used to predict increased risk for coronary artery disease include: C-reactive protein (CRP), complete lipid profile and calcium score screening heart scan.

What are the risk factors for coronary artery disease?

Nonmodifiable risk factors (those that cannot be changed) include:

  • Male gender. Men have a greater risk of heart attack than women do, and men have heart attacks earlier in life than women. However, beginning at Age 70, the risk is equal for men and women.
  • Advanced age. Coronary artery disease is more likely to occur as you get older, especially after Age 65.
  • Family history of heart disease. You have an increased risk of developing heart disease if you have a parent with a history of heart disease, especially if they were diagnosed before Age 50. Ask your doctor when it’s appropriate for you to start screenings for heart disease so it can be detected and treated early.
  • Race. African Americans have more severe high blood pressure than Caucasians and, therefore, have a higher risk of heart disease. The risk of heart disease is also higher among Mexican Americans, American Indians, native Hawaiians and some Asian Americans. This is partly due to higher rates of obesity and diabetes in these populations.

Modifiable risk factors (those you can treat or control) include:

  • Cigarette smoking and exposure to tobacco smoke
  • High blood cholesterol and high triglycerides – especially high LDL (“bad”) cholesterol over 100 mg/dL and low HDL (“good”) cholesterol under 40 mg/dL. Some patients who have existing heart or blood vessel disease, and other patients who have a very high risk, should aim for a LDL level less than 70 mg/dL. Your doctor can provide specific guidelines.
  • High blood pressure (140/90 mmHg or higher)
  • Uncontrolled diabetes (HbA1c >7.0)
  • Physical inactivity
  • Being overweight (body mass index [BMI] 25–29 kg/m2) or being obese (BMI higher than 30 kg/m2)
  • NOTE: How your weight is distributed is important. Your waist measurement is one way to determine fat distribution. Your waist circumference is the measurement of your waist, just above your navel. The risk of cardiovascular disease increases with a waist measurement of over 35 inches in women and over 40 inches in men.
  • Uncontrolled stress or anger
  • Diet high in saturated fat and cholesterol
  • Drinking too much alcohol

The more risk factors you have, the greater your risk of developing coronary artery disease.

How is coronary artery disease treated?

Treatment of coronary artery disease involves reducing your risk factors, taking medications as prescribed, possibly undergoing invasive and/or surgical procedures, and seeing your doctor for regular visits. Treating coronary artery disease is important to reduce your risk of a heart attack or stroke.

Reduce your Risk Factors

Reducing your risk factors involves making lifestyle changes. Your doctor will work with you to help you make these changes.

  • If you smoke, you should quit.
  • Make changes in your diet to reduce your cholesterol, control your blood pressure, and manage blood sugar if you have diabetes. Low-fat, low-sodium and low-cholesterol foods are recommended. Limiting alcohol to no more than one drink a day is also important. A registered dietitian can help you make the right dietary changes. Cleveland Clinic offers nutrition programs and classes to help you reach your goals.
  • Increase your exercise/activity level to help achieve and maintain a healthy weight and reduce stress. But, check with your doctor before starting an exercise program. Ask your doctor about participating in a cardiac rehabilitation program.
Take Medications as Prescribed

If lifestyle changes aren’t enough to control your heart disease, medications may be prescribed to treat certain risk factors, such as high cholesterol or high blood pressure. Your doctor will determine the best medications for you based on your personal needs, presence of other health conditions and your specific heart condition.

Have Procedures to Treat Coronary Artery Disease, as Recommended
Interventional procedures
balloon angioplasty (PTCA)

Common interventional procedures to treat coronary artery disease include balloon angioplasty (PTCA) and stent or drug-eluting stent placement. These procedures are considered nonsurgical because they are done by a cardiologist (heart doctor), who accesses the heart using a long, thin tube (catheter) that is inserted into a blood vessel, rather than by a surgeon through an incision. Several types of balloons and/or catheters are available to treat the plaque build-up within the vessel wall. If you require an interventional treatment, your physician will determine the type that is best for you based on your individual needs.

Coronary artery bypass graft (CABG) surgery

One or more blocked coronary arteries are bypassed by a blood vessel graft to restore normal blood flow to the heart. These grafts usually come from the patient’s own arteries and veins located in the chest, arm or leg. The graft goes around the clogged artery (or arteries) to create new pathways for oxygen-rich blood to flow to the heart.

Coronary Artery Bypass Graft (CABG)

When these traditional treatments are not options for you, doctors may suggest other less traditional therapies, such as enhanced external counterpulsation (EECP).

Enhanced external counterpulsation (EECP)

For patients who have persistent angina symptoms and have exhausted the standard treatments without successful results, EECP may stimulate the openings or formation of small branches of blood vessels (collaterals) to create a natural bypass around narrowed or blocked arteries. EECP is a noninvasive treatment for people who have chronic, stable angina; who are not receiving adequate relief from angina by taking nitrate medications; and who do not qualify for a procedure such as bypass surgery, angioplasty or stenting.

Important Note:

These procedures increase blood supply to your heart, but they do not cure coronary heart disease. You will still need to decrease your risk factors by making lifestyle changes, taking medications as prescribed and following your doctor's recommendations to reduce the risk of future disease development.

Follow-Up Care

Your cardiologist will want to see you on a regular basis for a physical exam and possibly to perform diagnostic tests. Your doctor will use the information gained from these visits to monitor the progress of your treatment. Check with your cardiologist to find out when to schedule your next appointment.

Doctors vary in quality due to differences in training and experience; hospitals differ in the number of services available. The more complex your medical problem, the greater these differences in quality become and the more they matter.

Clearly, the doctor and hospital that you choose for complex, specialized medical care will have a direct impact on how well you do. To help you make this choice, please review our Miller Family Heart and Vascular Institute Outcomes.

Cleveland Clinic Heart and Vascular Institute Cardiologists and Surgeons

Choosing a doctor to treat your coronary artery disease depends on where you are in your diagnosis and treatment.

Click on the following links to learn more about Sections and Departments treat patients with Coronary Artery Disease:

The Miller Family Heart and Vascular Institute offers specialty centers and clinics for patients whose treatment requires the expertise of a group of doctors and surgeons who focus on a specific condition.

See: About Us to learn more about the Sydell and Arnold Miller Family Heart & Vascular Institute.


If you need more information, click here to contact us, chat online with a nurse or call the Miller Family Heart and Vascular Institute Resource & Information Nurse at 216.445.9288 or toll-free at 866.289.6911. We would be happy to help you.

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