The coronary arteries, can become diseased, a condition known as coronary insufficiency. Various conditions--such as elevated serum cholesterol, hypertension, diabetes, cigarette smoking--cause cholesterol deposits to accumulate in the inner lining of the coronary arteries, a process called atherosclerosis. Atherosclerosis is a slow process, occurring over decades, and results in a gradual narrowing of the channel of the coronary artery as well as diminished arterial capacity to dilate under work load conditions. The result is a compromise to the blood flow to the heart muscle. This compromise may not manifest when the body is at rest but becomes much more significant under work conditions.

Even under "normal" conditions, the workload demands on the heart vary significantly. When the body is at rest, the heart’s oxygen demand is relatively low and the coronaries supply enough blood for baseline heart function. During exercise, the body’s blood demands rise greatly and the heart must increase it’s output of blood to meet these needs. In order to do this, the heart itself demands greater blood supply. In a healthy heart under work load conditions, the coronary arteries have a tremendous capacity to dilate, increasing by several fold their delivery of blood to the working heart muscle. However, when the coronary arteries become diseased, they lose the capacity to dilate and increase delivery of blood to meet the body’s needs. The result is coronary insufficiency.

Early symptoms of coronary artery disease include chest pain on exertion, or "angina." As the coronary artery disease progresses, the angina may occur with less and less exertion. This exertional angina ( also called stable angina) is significant with regards to symptoms but is also significant because the presence of cholesterol plaque in the coronary artery has the potential to cause myocardial infarction, or heart attack. Under certain conditions, a coronary plaque may become unstable and rupture. The various factors that lead to plaque rupture are not well understood and are currently actively being investigated. Coronary plaque rupture exposes the fatty contents of the plaque to the circulating blood, leading to a blood clot that occludes the channel of the coronary artery and prevents blood from flowing to the heart muscle. This results in "unstable angina" and heart attack, which are characterized by angina at rest.

Stable exertional angina is treated with a three-tiered approach of risk factor modification, medications, and coronary revascularization. Risk factor modification includes weight loss, adoption of a diet low in saturated fat, cessation of smoking, and initiation of an exercise program. These measures are aimed at reducing the coronary risk factors. Medications include aspirin, beta blockers, ACE inhibitors, and cholesterol-lowering drugs, all of which have been shown to reduce the risk of heart attack. Treatment of hypertension is done using a variety of antihypertensive agents nitrates are prescribed for controlling symptoms of angina. Coronary revascularization--with angioplasty or coronary artery bypass surgery--is performed in selected patients for relief of symptoms and, in some patients, for survival benefit.