A myocardial infarction is when part of the heart muscle dies because it has been starved of oxygen. Myocardial infarctions are also known as heart attacks or coronary thrombosis.
A myocardial infarction usually occurs when a blood clot forms in one of the coronary arteries (the blood vessels that lead to the heart muscle). This blood clot will block the blood supply and therefore the oxygen supply to the heart. A blockage can also sometimes be caused by a spasm, or sudden narrowing, of a coronary artery.
A myocardial infarction often causes severe and crushing pain in the middle of the chest, behind the breast bone. This pain may then travel from the chest to the neck, jaw, ears, arms and wrists, which often radiating towards the left arm. The person may also be cold and clammy, and their skin may appear pale and grey in colour. However sometimes the pain doesn't fit this pattern, and some people having a myocardial infarction don't have any pain.
If you suspect a myocardial infarction, get medical help immediately.
Other symptoms to look out for:
- shortness of breath
nausea or vomiting
feeling light-headed or dizzy
palpitations or an abnormal heart rate
A myocardial infarction is much more likely to occur when your arteries have become narrowed, usually through fatty deposits that form on the artery walls. This build up of fatty plaques on the inner lining of the coronary arteries (often compared to the furring up inside a kettle) is called atherosclerosis. It is also known as coronary artery disease (or coronary heart disease), and is a gradual process that slowly limits the blood supply to the heart muscle.
The biggest single risk factor for myocardial infarction is smoking. Other causes include high cholesterol, high blood pressure, diabetes and a family history of heart disease. Poor diet, lack of exercise and obesity are also contributing factors which can increase the risk of these fatty deposits forming, and so increase the risk of a heart attack.
When a myocardial infarction is suspected, drugs such as aspirin may be given immediately to improve blood flow through the coronary arteries. When a myocardial infarction has been finally diagnosed, one of two methods may be used to try to reopen the blocked artery:
- drugs that dissolve the blood clots which are blocking the artery, known as thrombolytics or 'clot busters', can restore blood flow in about 60% of cases
- an operation called percutaneous transluminal coronary angioplasty or PCI, which involves inserting a tube into the coronary arteries which carries a deflated balloon. This balloon can be inflated in the blocked area to push against the artery walls and open the vessel.
The next step in the treatment is to work out which part of the heart is affected, and how badly. This is done by studying an electrocardiogram (ECG - a trace of the electrical activity in the heart) as well as other tests. The area of the heart that has been affected has important implications for what sort of complications there may be, how well the patient will recover and the treatment they should be given.
Approximately six in 1,000 men in the UK aged between 30-69 have a myocardial infarction each year. For women, the figure is lower, at two in 1,000. Men are three times more likely to suffer from a heart attack than women.
Most people who survive the first month after a myocardial infarction will still be alive five years later.