Cardiac damage triggered by abrupt blockage of blood flow through the coronary arteries. If the heart muscle does not receive oxygen for a sufficient period of time, tissue death occurs, with subsequent loss of function of the fibres in the affected area.

Without adequate oxygen supply, the muscle cells fed by the blocked artery begin to die (infarct). 

The cause is often atherosclerosis which is the process that causes plaques of fatty or other material to form in the arterial wall. These plaques are coated with a fibrous material, the coating can rupture allowing plaque fragments to be released and clots to form on the plaque surface which may block the vessel or fragment and become lodged in smaller arteries. 

About 30 minutes after the vessel is blocked, irreversible damage to the muscle cells begins to occur. The goal of treatment is to preserve as much muscle as possible without irreversible damage and to prevent pain (pain causes increased work of the heart and increased risk of cardiac cell death).