Coronary arteries supply the heart muscle with oxygen and nutrition so that it can pump blood to the rest of the body. The narrowing and blockage of these blood vessels, commonly called coronary artery disease, is responsible for heart attacks and heart pain (angina). This process takes many years to develop. It is more common in males, diabetics, smokers, those with high blood pressure or high cholesterol, and in those with a family history of premature heart disease (in first-degree male relatives, premature is younger than age 55; in female relatives, younger than 65). People with these risk factors experience vessel trauma and inflammation, which in turn encourage the development of plaque in the coronary arteries. Under the right conditions, these plaques cause a progressive narrowing of the artery, sometimes resulting in an intermittent or complete obstruction of the vessel. This obstruction can produce acute symptoms, including heart attack.

Most coronary heart disease results from a buildup of fatty deposits on the heart blood vessel wall. This is plaque. Progressive narrowing restricts blood flow to the heart muscle, which causes the muscle to cramp; this discomfort is called angina pectoris. With a sudden obstruction of blood flow--usually by a piece of plaque that has ruptured, causing a blood clot to form--the heart muscle begins to die and the discomfort is similar to angina but is more intense and prolonged. If blood flow can be restored within a few hours, some of the damaged muscle can be salvaged. Clot-busting drugs, balloon angioplasty, and stents are all very effective in restoring blood flow and improving survival in heart-attack victims. See "Percutaneous Coronary Intervention").

High blood pressure (hypertension), diabetes, high cholesterol, a sedentary lifestyle, smoking, and a family history of heart disease are all risk factors. Managing these risk factors can slow the disease.

Chest discomfort upon exertion may suggest coronary artery disease. The classic diagnostic tool is the stress test, in which the patient walks on a treadmill while connected to an electrocardiogram machine (ECG), which monitors heart rate. This may be coupled with imaging tests, such as the nuclear stress test and echocardiography. (These improve the accuracy of the stress test by taking pictures of the heart.) Sometimes drugs are used to stress the heart if the patient is not able to walk. In the appropriate patient, more invasive studies such as cardiac catheterization (watch a video of an angiogram of normal coronary arteries Right coronary artery, Left coronary artery) can help determine a diagnosis and prognosis.

A relatively new technique, calcium scanning, helps get a rough estimate of plaque buildup (calcium deposits frequently appear in plaque). Measures of inflammation such as C-reactive protein (CRP) have also been used to assess risk and prognosis. An even newer technique, multi-slice CT scanning, promises to replace at least some of these diagnostic tools in the near future.

The most feared complication is acute myocardial infarction or heart attack. In some patients, this causes sudden collapse and death. Those who survive can experience unstable heart rhythms and congestive heart failure (due to the damage to the heart muscle).

The progress of coronary artery disease can be slowed by a motivated patient--someone who exercises, takes their medications as prescribed, and stops smoking. Behavioral changes like these have helped make coronary artery disease much less fatal than it was two decades ago.