Coronary artery disease (CAD), also called coronary heart disease, is primarily caused by atherosclerosis, a process in which a substance called plaque builds up on the inner walls of the arteries. When the buildup occurs in the coronary arteries, the arteries that supply the heart, it causes CAD.

Plaque is made up of fat, cholesterol, calcium, and other substances found in the blood. Eventually, the build up of plaque narrows and hardens the arteries, and blood flow to the heart is reduced. This decreases the oxygen supply to the heart muscle.

When the heart muscle does not get enough oxygen, two conditions can develop, angina and a heart attack. Angina is a condition in which the heart muscle does not get sufficient oxygen. This causes chest pain or discomfort. A heart attack can occur if an artery closes all the way or a clot blocks the blood flow. When this happens, the heart muscle does not get oxygen and cells begin to die. A blocked coronary artery can also cause an irregular heart beat called arrhythmia that decreases the heart's ability to pump blood and can cause death.

Certain factors increase your risk of developing CAD. According to the National Heart, Lung, and Blood Institute, some risk factors can't be changed:

• Your age. Men older than 45 and women older than 55 are at higher risk.

• Having a family history of early heart disease. Your risk increases if heart disease was diagnosed in your father or brother before age 55, or if heart disease was diagnosed in your mother or sister before age 65.

But you can control other factors.

High cholesterol

Cholesterol is a waxy substance your body needs for nerve function, and to make cells and hormones. It is found naturally in foods and is made by your body. It is carried in the blood in combination with other substances called lipoproteins. Low density lipoproteins (LDL) carry the form of cholesterol that builds up in the arteries. LDL is also known as the "bad" cholesterol. High density lipoproteins (HDL) carry cholesterol that is being removed from the body, which keeps it from building up on the walls of arteries. HDL is known as the "good" cholesterol.

A low HDL level (less than 40 mg/dL in men; less than 50 mg/dL in women) increases the risk for heart disease. If you have too much LDL cholesterol (160mg/dL or higher), it can accumulate with other substances in the lining of the arteries. This makes the arteries narrower and eventually blocks the flow of blood. 

Two ways to lower your cholesterol without medication are to exercise regularly and eat a diet low in saturated fat and low in cholesterol. Most people with a total cholesterol of 240 mg/dL or higher will need medication to lower their levels. If you are prescribed medication, take it as directed and report any side effects to you doctor.

High blood pressure

Your heart works harder when your blood pressure is at 140/90 mm Hg or greater. This level is called high blood pressure. When your blood pressure is high for an extended time, the heart can enlarge and arteries can become scarred and hardened. You can treat high blood pressure with medication and by making changes in your diet, weight and exercise routine. For healthy adults ages 18 to 65 years, research has shown that 2 hours and 30 minutes or 150 minutes each week of regular moderate-intensity physical activity, such as brisk walking, gardening, or dancing, can help lower your blood pressure. It's important to know you can break up the time into shorter 10-minute periods. Check with your doctor before you start any program to find out which activities and how much activity is safe for you.

Cigarette smoking

Smoking has been identified as the single most important modifiable risk factor for heart disease. Smoking promotes heart disease by speeding up the development of atherosclerosis and reducing your HDL cholesterol.

Diabetes

Diabetes makes it easier for plaque to form in your arteries. Because of this, it increases the risk for heart attack. People with diabetes are two to four times as likely to have a heart attack as is someone who does not have diabetes. You can delay or prevent the buildup of plaque by keeping blood sugar levels in the optimal range, and managing high blood pressure, cholesterol, and weight.