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Heart Attack and Acute Coronary Syndrome

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Also known as: Acute Myocardial Infarct; AMI; Myocardial Infarct; MI; ACS

What are heart attack and acute coronary syndrome?

A heart attack, also called an acute myocardial infarct (AMI), is caused by a blockage in the heart's arteries that completely cuts off the blood supply to a portion of the heart. Without prompt medical treatment, this blockage can damage or destroy heart tissue and can kill. According to the American Heart Association, about 735,000 people in the U.S. have heart attacks each year and about 120,000 of those affected die.

Acute coronary syndrome (ACS) is a group of signs and symptoms that are associated with insufficient blood flow to the heart. A heart attack differs from other forms of ACS in that the decreased blood flow persists, causing death of heart muscle cells. When someone is rushed to the emergency room, testing must be performed to determine whether or not a person's signs and symptoms (ACS) are due to a heart attack or to another cause.

Thumbnail diagram of heart

The heart is a muscular organ that pumps blood throughout the body via a system of veins and arteries. Blood flows from the lungs, where it picks up oxygen, through the pulmonary veins into the heart, and then gets pumped out to the body, delivering oxygen to the tissues. The blood returns to the heart via the veins and gets pumped back to the lungs once again. In order to perform these tasks, the heart requires large amounts of oxygen that it obtains from its own dedicated network of veins and arteries.

The persistent blockage causing a heart attack is usually caused by a blood clot that becomes lodged in an artery that supplies blood to the heart (termed a coronary artery). This most frequently occurs in arteries that have narrowed, thickened walls. The thickening is caused by a gradual build-up of plaque in a process called atherosclerosis. The acute blockage of blood flow caused by a clot in a coronary artery, if present for more than an hour, can cause death of the heart muscle cells (infarct) and lead to scarring of the affected area of the heart.

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