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Cardiac ischemia is a situation in which the flow of oxygen-rich blood to the heart muscle is impeded, resulting in inadequate oxygenation of the heart. The most common cause of cardiac ischemia is plaque buildup in the arteries due to the long-term effects of coronary artery disease. This plaque buildup narrows the arteries to the point where the amount of blood flowing through the arteries is not enough to supply oxygen-rich blood to the heart, especially during times of physical exertion or emotional stress.

The lack of oxygen is often temporary, and symptoms can include a type of chest pain, pressure or discomfort called angina. These episodes may last anywhere from 2 to 20 minutes. However, many episodes of ischemia do not have any associated symptoms (silent ischemia).

Lengthy episodes of cardiac ischemia can be a sign of a heart attack. A heart attack occurs when a blood clot blocks the flow of blood to the heart muscle. It can occur in an artery already narrowed by plaque (atherosclerosis), or a heart attack can occur after a blood clot breaks off from its original site and travels through the arteries. The blockage causes a sudden and possibly complete interruption of oxygen-rich blood flow, and the resulting heart attack could cause permanent damage and scarring to the portion of the heart muscle supplied by the blocked artery. Prevention and treatment are related to modifying the underlying factors that promote the development of atherosclerosis and blood clot formation.