Acute Coronary Syndrome

Acute coronary syndrome is a term given by doctors for various heart conditions, including a myocardial infarction (heart attack) and unstable angina. These conditions are due to there being a reduced amount of blood flowing to a part of the heart. Various treatments are given and these usually depend on the type of acute coronary syndrome. Treatments help to ease the pain, improve the blood flow and to prevent any future complications.

What is acute coronary syndrome?

The term acute coronary syndrome (ACS) covers a range of disorders including myocardial infarction (heart attack) and unstable angina that are caused by the same underlying problem.

The underlying problem is a sudden reduction of blood flow to part of the heart muscle. This is usually caused by a blood clot that forms on a patch of atheroma within a coronary artery (which is described below).

The types of problems range from unstable angina - when the blood clot causes a reduced blood flow, but not a total blockage so the heart muscle supplied by the affected artery does not infarct (die) - to an actual myocardial infarction (MI).

The location of the blockage, the length of time that blood flow is blocked, and the amount of damage that occurs determine the type of acute coronary syndrome.

Understanding the heart and coronary arteries

The heart is made mainly of special muscle. The heart pumps blood into arteries (blood vessels) which take the blood to every part of the body.

Like any other muscle, the heart muscle needs a good blood supply. The coronary arteries take blood to the heart muscle. The main coronary arteries branch off from the aorta. The aorta is the large artery which takes oxygen-rich blood from the heart chambers to the body. The main coronary arteries divide into smaller branches which take blood to all parts of the heart muscle.

What happens in acute coronary syndrome?

ACS ranges from MI to unstable angina.

A myocardial infarction?

If you have an MI, a coronary artery or one of its smaller branches is suddenly blocked. The part of the heart muscle supplied by this artery loses its blood (and oxygen) supply. This part of the heart muscle is at risk of dying unless the blockage is quickly undone. (The word infarction means death of some tissue due to a blocked artery which stops blood from getting past.) An MI is sometimes called a heart attack or a coronary thrombosis.

There are different types of MI which are based on what is seen on your heart tracing (also called an electrocardiograph (ECG)). The two main types are called ST elevation MI (STEMI) and non-ST elevation MI (NSTEMI). In a STEMI, the artery supplying an area of the heart muscle is completely blocked. However, in an NSTEMI, the artery is only partly blocked, so only part of the heart muscle being supplied by the affected artery is affected.