2. What is atherosclerosis?

Atherosclerosis of the arteries is a process where over time plaque builds up inside the artery wall. Plaque is composed of cholesterol, fat and calcium as well as other substances. Over time the plaque accumulates, hardens and narrows the arteries throughout the body. This process is also known as “hardening of the arteries.” Coronary artery disease occurs when plaque builds up in the coronary arteries and causes them to narrow. With this narrowing, blood flow is limited to the heart muscle and symptoms, like chest pain, may occur. A heart attack occurs when blood flow in an artery is completely blocked and the heart muscle is “starved” of oxygen and death of an area of the heart may occur.

Figure A shows a normal artery with normal blood flow. The inset image shows a cross-section of a normal artery. Figure B shows an artery with plaque buildup. The inset image shows a cross-section of an artery with plaque buildup. (Source: National Heart, Lung and Blood Institute)

3. What causes coronary artery disease?

The process of atherosclerosis begins when the smooth interior surface of the coronary artery is damaged. The most common causes of damage are uncontrolled hypertension, abnormal cholesterol levels, tobacco use, and poorly controlled diabetes. Once the arterial wall is damaged the “bad cholesterol,” or the LDL, begins to build up on the damaged walls. With this accumulation, inflammatory cells are released from the body and migrate to the damaged arteries. These inflammatory products also become part of the buildup on the arterial walls and over time plaque is formed.

4. What is the clinical significance of this plaque?

Atherosclerotic plaque in the coronary arteries can have many different clinical implications:

1. Plaque can grow slowly and never develop into any significant blockage that can cause symptoms.
2. Plaque can expand and diminish blood flow in a coronary artery. In this case the heart muscle is still getting some blood flow but such symptoms as chest pain with exertion (angina) and shortness of breath may occur.
3. Plaque can rupture causing blood to clot and completely block the artery. If the blockage is sustained, then the heart muscle is starved of oxygen and the muscle dies causing a heart attack. Interestingly, heart attacks typically occur in arteries with minor blockages.