CORONARY ARTERY DISEASE

Definition: Myocardial Infarction
Heart Structures
Definition: Coronary Artery Disease
Symptoms
Risk Factors
Medical Examination
Medical Therapies


We all know someone who has had a “heart attack”, or what is medically known as a myocardial infarction. The term myocardium is the name for the heart muscle, generally that of the left ventricle (main pump of the heart). The term infarction is the term used to define the process where tissue dies as a result of insufficient arterial blood supply, such as that found in diseased arteries to any organs of the body, including the heart.

The two main pumping chambers of the heart are the left and right ventricles. These structures are composed of muscle which functions rather automatically in performing their pumping duties. This muscle requires oxygen and energy to not only survive, but also to provide endless function as a pump. Arteries supply the oxygen and other nutrients to the muscle. These arteries are called coronary arteries. There are three main coronary arteries: left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA). When these arteries are normal they are very pliable and have smooth internal surfaces.

Coronary Artery Disease is a disease which causes gradual or abrupt decrease in arterial blood flow to the heart muscle. The reason that this decrease in blood flow occurs is because there is a build-up of “plaque” in the walls of the coronary arteries. (see below diagram). This plaque is made up of calcium, cholesterol, and large cells containing lipid (other fatty materials). In many patients the peripheral arteries, such as those of the chest, abdomen, head, and extremities, may also be affected by this plaque deposit. This process is called atherosclerosis.

The patients who have significant narrowing of one or more of their coronary arteries have a variety of symptoms, which range from none to many, including chest pain radiating to the left arm, neck and jaw pain, upper abdominal pain, and many more less common symptoms. The rhythm of the heart also may be variable as well. When the blood supply to the heart muscle is severely reduced there may result in the death of the muscle cells of the myocardium. As with any destruction of tissues of the body, the result is the formation of scar tissue which is incapable of contributing to the pumping effort of the left ventricular muscle. This results in a reduction in the pumping output of the heart, and renders the patient incapable of performing tasks he had previously done with ease. A cardiologist can detect this heart failure (congestive heart failure) by a physical examination and some other tests (such as EKG and chest X-ray).

There are 12-15 million people in the US that have coronary artery disease. More men than women have the disease. What are the factors that result in someone having coronary artery disease? These factors are called “risk factors”. There are two main categories of risk factors:

1. Risk factors that we cannot change: age and heredity. As we age, there is a higher incidence of coronary disease. Obviously, we cannot change our heredity.
   
2. Risk factors that we can change: high cholesterol, high blood pressure, cigarette smoking, diabetes, obesity, lack of physical activity.

When we see our physician, he/she will attempt to point out the changes that can be made in our lives that will lessen the risk of getting coronary artery disease. The earlier we take this advice seriously, the better.

Our physician will institute a series of examinations to determine if coronary artery disease is present, and to what degree. We are familiar with most of these tests:

1. History and physical examination.
   
2. Electrocardiogram: looking at the electrical activity of the heart.
   
3. Exercise stress test: this can be a treadmill test or a drug-induced stress test. Both of these are equivalent. People who cannot exercise generally use the latter test. Many times the stress test will be coupled with a series of nuclear images which define the adequacy of the blood flow to the heart muscle of the left ventricle both at rest and with exercise.
   
4. Chest X-ray: to observe the sizes, densities and shapes of the heart and lungs.
   
5. Cardiac catheterization: by inserting a flexible catheter into a groin or arm artery, the cardiologist can examine the chamber of the left ventricle along with the coronary arteries. A clear definition of the extent of disease and whether the diseased arteries are amenable to therapy can be made. This therapy might be coronary artery bypass grafting (CABG) or balloon angioplasty (PTCA) with stenting.

If there are indications that coronary bypass grafting or angioplasty cannot be done, then the physician might initiate medical therapy (i.e. pharmacologic or drug therapy). The result of this medical therapy, along with the more invasive procedures should be to:

1. Relieve symptoms.
2. Prevent catastrophic events: sudden death.
3. Prevent heart attacks.
4. Prevent dangerous rhythm disturbances.
5. Allow the patient to have a more productive life.

W. A. Boade, MD
1.25.2005

These articles are intended for informational purposes only and should not be used to make diagnosis of any condition. We encourage you to seek examination and treatment by your trained health professional.