What is Coronary Artery Disease

Arteries that supply blood and oxygen to the heart muscles are called coronary arteries. Coronary artery disease (CAD) occurs when cholesterol plaque (a hard, thick substance comprised of varying amounts of cholesterol, calcium, muscle cells, and connective tissue, which accumulates locally in the artery walls) builds up in the walls of these arteries, a process called arteriosclerosis. Over time, arteriosclerosis causes significant narrowing of one or more coronary arteries. When coronary arteries narrow more than 50% to 70%, the blood supply beyond the plaque becomes inadequate to meet the increased oxygen demand of the heart muscle during exercise. Lack of oxygen (ischemia) in the heart muscle causes chest pain (angina) in most people. However, some 25% of those with significant coronary artery narrowing experience no chest pain at all despite documented ischemia, or may only develop episodic shortness of breath instead of chest pain. These people are said to have “silent angina” and have the same risk of heart attack as those with angina. When arteries are narrowed in excess of 90% to 99%, people often have angina at rest (unstable angina). When a blood clot (thrombus) forms on the plaque, the artery may become completely blocked, causing death of a part of the heart muscles (heart attack, or myocardial infarction).

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.

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How to diagnose Coronary Artery Disease

The resting electrocardiogram (EKG, ECC) is a recording of the electrical activity of the heart, and can show changes indicative of ischemia or heart attack. Often, the EKG in individuals with coronary artery disease is normal at rest, and only becomes abnormal when heart muscle ischemia is brought on by exertion. Therefore, exercise treadmill or bicycle testing (stress tests) are useful screening tests for those with significant coronary artery disease (CAD) and a normal resting EKG. These stress tests are 60% to 70% accurate in diagnosing significant coronary artery disease.

If the stress tests are not diagnostic, a nuclear agent can be given intravenously during stress tests. Addition of one of these agents allows imaging of the blood flow to different regions of the heart, using an external camera. An area of the heart with reduced blood flow during exercise, but normal blood flow at rest, signifies substantial artery narrowing in that region.

Stress echocardiography combines echocardiography (ultrasound imaging of the heart muscle) with exercise stress testing. It is also an accurate technique for detecting coronary artery disease. When a significant narrowing exists, the heart muscle supplied by the narrowed artery does not contract as well as the rest of the heart muscle. Stress echocardiography and thallium stress tests are 80% to 85% accurate in detecting significant coronary artery disease.

When a person cannot undergo an exercise stress test because of neurological or arthritic difficulties, medications can be injected intravenously to simulate the stress on the heart normally brought on by exercise. Heart imaging can be performed with either a nuclear camera or echocardiography.

Cardiac catheterization with angiography (coronary arteriography) is a technique that allows X-ray pictures to be taken of the coronary arteries. It is the most accurate test to detect coronary artery narrowing. Small hollow plastic tubes (catheters) are advanced under X-ray guidance to the openings of coronary arteries. Iodine contrast “dye” is then injected into the arteries while an X-ray video is recorded. Coronary arteriography gives the doctor a picture of the location and severity of narrowed artery segments. This information is important in helping the doctor select medications, percutaneous coronary intervention, or coronary artery bypass graft surgery (CABG) as the preferred treatment option.

A newer, less invasive technique is the availability of high speed CT coronary angiography. While it still involves radiation and dye exposure, no catheters are needed in the arterial system, which does decrease the risk of the procedure somewhat. This the role of this modality in the evaluation and management of coronary artery disease is still evolving. It is important to remember that the risk of serious complications from conventional coronary angiography is very low (well under 1%).

How do we treat coronary artery disease?

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.

Angina medications reduce the heart muscle’s demand for oxygen in order to compensate for the reduced blood supply, and also may partially dilate the coronary arteries to enhance blood flow. Three commonly used classes of drugs are the nitrates, beta blockers, and calcium blockers.

Many people benefit from these angina medications and experience reduction of angina during exertion. When significant ischemia still occurs, either with ongoing symptoms or with exercise testing, coronary arteriography is usually performed, often followed by either percutaneous coronary intervention or CABG.

Individuals with unstable angina have severe coronary artery narrowing and often are at imminent risk of heart attack. In addition to angina medications, they are given aspirin and the intravenous blood thinner, heparin. A form of heparin, enoxaparin (Lovenox), may be administered subcutaneously, and has been demonstrated to be as effective as intravenous heparin in those with unstable angina. Aspirin prevents clumping of blood clotting elements called platelets, while heparin prevents blood from clotting on the surface of plaques. Newer potent IV antiplatelet agents (“super aspirins”) are also available to help initially stabilize such individuals. While people with unstable angina may have their symptoms temporarily controlled with these potent medications, they are often at risk for the development of heart attacks. For this reason, many people with unstable angina are referred for coronary angiography, and possible Percutaneous Coronary Intervention (PCI) or Coronary Artery Bypass Grafting CABG.

CABG surgery is performed to relieve angina in those whose illness has not responded to medications and are not good candidates for PCI. CABG is best performed in patients with multiple blockages in multiple locations, or when blockages are located in certain arterial segments which are not well-suited for percutaneous coronary intervention. CABG is often also used in patients who have failed to attain long-term success following one or more percutaneous coronary intervention procedures. CABG surgery has been shown to improve long- term survival in people with significant narrowing of the left main coronary artery, and in those with significant narrowing in multiple arteries, especially in cases of decreased heart muscle pump function.

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