Myocardial Infarction and Acute Coronary Syndromes (ACS)

A heart attack (myocardial infarction) is usually caused by a blood clot, which stops the blood flowing to a part of your heart muscle. You should call for an ambulance immediately if you develop severe chest pain. Treatment with a clot-busting medicine or an emergency procedure to restore the blood flow through the blocked blood vessel are usually done as soon as possible. This is to prevent or minimise any damage to your heart muscle. Other treatments help to ease the pain and to prevent complications. Reducing various risk factors can help to prevent a myocardial infarction.

Understanding the heart and coronary arteries

The heart is mainly made of special muscle (myocardium). 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 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 to your heart with a myocardial infarction

If you have a myocardial infarction (heart attack), 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 if the vessel is blocked. This part of the heart muscle is at risk of dying unless the blockage is quickly removed. When a part of the heart muscle is damaged it is said to be infarcted. The term myocardial infarction (MI) means damaged heart muscle. If a main coronary arteries is blocked, a large part of the heart muscle is affected. If a smaller branch artery is blocked, a smaller amount of heart muscle is affected. After an MI, if part of the heart muscle has died, it is replaced by scar tissue over the next few weeks.

What are the symptoms of a myocardial infarction

The most common symptom is severe chest pain, which often feels like a heavy pressure feeling on your chest. The pain may also travel up into your jaw and down your left arm or down both arms. You may also sweat, feel sick and feel faint. You may also feel short of breath. The pain may be similar to angina, but it is usually more severe and lasts longer. (Angina usually goes off after a few minutes. MI pain usually lasts more than 15 minutes - sometimes several hours.)However, some people have only a mild discomfort in their chest. The pain can sometimes feel like indigestion or heartburn.Occasionally, an MI happens without causing any pain. This is usually diagnosed when you have an electrocardiogram (ECG, or heart tracing) at a later stage.

Some people collapse and die suddenly, if they have a large portion of heart muscle damaged. This is not very common.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.

What causes acute coronary syndrome

The majority of cases are due to there being some narrowing in the blood vessels supplying the heart. This is usually due to the presence of some atheroma within the lining of the artery. Atheroma is like fatty patches or plaques that develop within the inside lining of arteries. (This is similar to water pipes that get furred up.) Plaques of atheroma may gradually form over a number of years in one or more places in the coronary arteries. Each plaque has an outer firm shell with a soft inner fatty core. Atheroma leads to the blood vessels narrowing.Various other uncommon conditions can also block a coronary artery. For example: inflammation of the coronary arteries (rare); a stab wound to the heart; a blood clot forming elsewhere in the body (for example, in a heart chamber) and travelling to a coronary artery where it gets stuck; taking cocaine, which can cause a coronary artery to go into spasm; complications from heart surgery and some other rare heart problems. These are not dealt with further in this leaflet.

Who is at risk of having acute coronary syndrome

ACS is common. About 114,000 people in the UK are admitted to hospital with an ACS each year. Most occur in people aged over 50 and become more common with increasing age. Sometimes younger people are affected.The risk factors for having an ACS are actually the same as the risk factors for having an MI or cardiovascular disease. See separate leaflet called 'Preventing Cardiovascular Diseases' which discusses these in more detail.

What are the symptoms of acute coronary syndrome

The most common symptom of a ACS is having severe chest pain. The pain often feels like a heavy pressure on your chest. The pain may also travel up into your jaw and down your left arm, or down both arms. You may also sweat, feel sick and feel faint. You may also feel short of breath.The pain may be similar to a bout of stable (normal) angina, but it is usually more severe and lasts longer. (In people who have stable angina, an angina pain usually goes off after a few minutes. ACS pain usually lasts more than 15 minutes - sometimes several hours.)

Categories