A heart attack (also known as a myocardial infarction) is the death of heart muscle from the sudden blockage of a coronary artery by a blood clot. Coronary arteries are blood vessels that supply the heart muscle with blood and oxygen. Blockage of a coronary artery deprives the heart muscle of blood and oxygen, causing injury to the heart muscle. Injury to the heart muscle causes chest pain and pressure. If blood flow is not restored within 20 to 40 minutes, irreversible death of the heart muscle will begin to occur. Muscle continues to die for 6-8 hours at which time the heart attack usually is "complete." The dead heart muscle is replaced by scar tissue.
The heart is a muscular pump located in the chest. Its job is to pump blood around the body via the circulatory system of blood vessels. The heart consists of 4 chambers: right atrium and right ventricle, and left atrium and left ventricle. Blood is depleted of oxygen after circulating through the body. This blood returns into the right atrium. From there the blood flows into the right ventricle, which pumps the blood out to the lungs for oxygenation.
The oxygen-rich blood then returns to the left atrium. From there it flows into the left ventricle and is pumped out at high pressure into the arteries. The high pressure is generated by powerful contraction of the heart muscle.This raises the pressure of the blood and enables it to flow through the extensive network of arteries to every part of the body and return to the heart. For this pumping action, the heart has to be strong. The heart is nourished by the blood supplied directly to the heart muscle through the coronary arteries. The strength of the heart muscle depends very much on this blood supply. The coronary arteries are usually strong, elastic, and quite flexible. The inner lining of the arteries is normally smooth. This allows the blood to flow smoothly without clotting.
