Heart attack (otherwise known as myocardial infarction) is usually caused by a blood clot that obstructs the blood flow in one of the coronary arteries. The coronary arteries are responsible for providing the heart with oxygen and if blocked, the cells of the heart die from hypoxia if the blockage isn’t removed in time.
The size of the damaged area of the heart depends on which artery was blocked. If one of the main coronary arteries was blocked, a large portion of the heart will be damaged. If, however, a smaller artery is blocked, the extent of the damage will be much smaller.
After a few weeks, if the patient survives the heart attack, the damaged cells of the heart are replaced with scar tissue. If a large portion of the heart was replaced by scar tissue, the force with which the heart can contract is substantially lowered. This can result in chronic heart failure. Moreover, the scar tissue, being less strong as myocardial cells, might become stretched by the high pressure within the heart. This can result in an aneurism (a protrusion in the heart’s wall) or even a rupture of the heart’s wall.