A Myocardial Infarction, also known as a heart attack or an M.I. is death of the muscle in A heart attack is the result of a blockage in one of the coronary arteries carrying oxygen-rich blood to the heart muscle. When the blood supply is cut off, a part of the heart muscle dies - or infarcts. A heart attack is also known as a myocardial infarction (MI), coronary thrombosis or, simply "a coronary".

Causes of a heart attack

The underlying cause of most heart attacks is atherosclerosis, a disease of the coronary arteries that usually develops over many years.

Atherosclerosis involves the formation of fatty deposits (plaques) on the walls of the coronary arteries. These plaques can rupture, releasing substances that cause blood flowing in the coronary artery to clot. Combined, the plaque and blood clot (thrombus) can block the coronary artery altogether, resulting in the symptoms of heart attack.

Lesser degrees of narrowing, without complete blockage, of a coronary artery may cause angina

Who is affected?

Heart attacks are more common in elderly people and, up to the age of 50, are more common in men than women. After that age, the difference between men and women narrows.

In addition to age and sex, doctors have identified a number of factors that may occur together to make atherosclerosis, and so a heart attack, more likely. These include

A family history of heart disease, an inactive lifestyle (less than 30 minutes per day, on most days, of physical activity), diabetes, obesity, high blood pressure, high blood cholesterol. Smoking.

Symptoms

Most heart attacks cause severe pain in the centre of the chest. However, sometimes there may be no symptoms at all (silent MI), especially in the elderly and people with diabetes.

The central chest pain is often described as heaviness, squeezing or crushing, and may come on suddenly causing the person to collapse. It may spread to the arms, neck, jaw, face, back or stomach. A person having a heart attack may appear pale, sweaty and breathless. They may feel or be sick. The symptoms can come on suddenly, but sometimes the pain comes on more slowly. Heart attack pain is more persistent than angina and can last for hours. A person who is used to angina will find that the pain of a heart attack will not respond to their usual medicine (eg glyceryl trinitrate). Treating a heart attack

If a heart attack is suspected, emergency treatment is vital - getting to hospital quickly and receiving specialist care greatly improves the chances of survival. If you suspect someone is having a heart attack call 999 immediately. If the person can swallow, give them a single aspirin tablet to chew. This thins the blood and can help to prevent the clot that is blocking the coronary artery from spreading.

Before hospital

In response to an emergency call for a suspected heart attack, the ambulance service will send a paramedic as quickly as possible. Their job is to stabilise the person and transport them to hospital quickly and safely for further treatment. A paramedic may have to resuscitate a very ill person, give oxygen and pain-relieving drugs. In a suitably equipped ambulance, they may take an electrocardiogram (ECG), which is a trace of the electrical activity of the heart. A heart attack can be diagnosed with this test.

At hospital

An ECG will be taken and blood tests done to confirm the diagnosis. Oxygen and pain relief is given - usually by giving an intravenous injection of diamorphine (heroin), which is combined with an anti-sickness medicine. This will make the patient comfortable and calmer and in this situation has no danger of causing addiction.

Low dose aspirin, if not already given, is used to thin the blood. Ideally, the person should be transferred to a coronary care unit for specialist medical and nursing care. At the coronary care unit, or sometimes in the accident and emergency department, a slow intravenous injection of a drug called a thrombolytic (clot buster) is given. This dissolves the clot in the coronary artery. The drug is not without risks and a heart attack must be confirmed before giving it. But if the clot dissolves, the chances of a full recovery are much better. Other drugs may be given if pain persists, if there is fluid on the lungs or a fast heartbeat.

Complications

In the first few days of surviving a heart attack, there may be irregular, or abnormally fast or slow heart rhythms, which are known as arrhythmias. As a result of the attack, the heart may not be able to pump around the body as efficiently as before the heart attack. This is called heart failure. The larger the area of the heart muscle affected by the heart attack, the more likely heart failure is to occur.

Other rarer complications can include blood clots on the lung, stroke, inflammation of the membrane covering the heart (pericarditis), a bulging weakness in the heart muscle (aneurysm). There is also an increased risk of further heart attacks.

Long-term treatments

A small daily dose of aspirin is usually recommended for all heart attack survivors. Then, a range of other medicines may be required to promote blood flow, widen narrowed arteries, to give the heart less work to do or to make it pump more effectively. Other drugs reduce levels of blood cholesterol or control blood pressure. People who have had a heart attack may have to take a number of medicines daily, and long term.