As many as one in three people will be dead within 24 hours of having a heart attack. But most people who survive the first month will still be alive five years later. So prompt treatment is essential, as is prevention. What causes a heart attack? The heart is a large muscular pump. It beats 70 times a minute to push blood around the body. Like any busy muscle, the heart tissues need a good supply of blood from their blood vessels, which are called the coronary arteries. Diseases that narrow the coronary arteries can cause a shortage of oxygen and essential nutrients in the heart muscle. This triggers chest pain known as angina, especially when the heart is made to work extra hard, for example during exercise. If someone has angina, the more severe the narrowing of the arteries, the less they can do before they experience pain. If the shortage is severe and prolonged, some of the heart muscle will die, resulting in permanent damage. This is a heart attack, more technically known as a myocardial infarction or MI. Blocked coronary arteries The most common underlying disease for heart attacks is atherosclerosis, where fatty plaques build up on the lining of the coronary arteries. This is known as coronary artery disease, and is a gradual process that slowly limits the blood supply to the heart muscle. How do heart attacks happen? What usually happens in a heart attack is that one of the fatty plaques cracks and a blood clot forms on top of it. It is this clot that finally blocks the artery completely. There are other, rarer causes of a heart attack, such as a dissection or splitting of the wall of the coronary artery. How many people are affected? The UK has one of the worst heart attack rates in the world. It's estimated that someone has a heart attack every two minutes in the UK. More than 1.4 million people have angina and each year about 275,000 people have a heart attack. Of these, more than 120,000 are fatal. Heart attacks are responsible for one in four deaths in men and one in six deaths in women. They are more common among older people. Risk factors The biggest single risk factor for heart attack is smoking. Other causes include high cholesterol, high blood pressure, diabetes and a family history of heart disease. There are many steps you can take to change your lifestyle and reduce your risk. Different types of heart attack When someone goes into hospital with pain or other symptoms suggesting coronary heart disease, a diagnosis of acute coronary syndrome (ACS) is made. The next step is to work out which part of the heart is affected, and how badly. This is done by studying an electrocardiogram (ECG) and other tests, in particular a blood test that measures levels of a chemical called troponin, which is released from damaged heart muscle cells. There are several different types of heart attack. The area of the heart that's 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. For example, if a heart attack affects the inferior (underneath) surface of the heart, which sits against the diaphragm, there is a greater risk of abnormal heart rhythms, because the electrical conducting system of the heart is disrupted. If the heart attack affects the anterior (front wall) of the heart, there is more likely to be damage to the left ventricle, which is responsible for pumping blood around the body, leading to low blood pressure and heart failure. Sometimes a heart attack doesn't affect the full thickness of the heart muscle and may not produce typical changes on an ECG. This sort of heart attack may require different treatment. Rapid treatment saves lives About half of those who have a heart attack die within 28 days. Most people who survive the first month will still be alive five years later, but many are left with long-term heart problems. One in three people dies within 24 hours. Most of these deaths are sudden, occurring within one hour of onset of symptoms and before reaching hospital, and are often due to dangerous heart rhythms. Heart attacks must be recognised and treated as quickly as possible because once a coronary artery is blocked, the heart muscle will die within four to six hours. Rapid treatment reduces the risk of sudden death and prevents long-term complications. Don't wait to call for help - this could make treatment less effective. If you suspect a heart attack, get medical help immediately Everyone's experience is different but common symptoms include: chest pain, usually a central, crushing pain, which may travel into the left arm or up into the neck or jaw, and persists for more than a few minutes sometimes the pain doesn't fit this pattern, or is confused with indigestion some people having a heart attack don't have any pain shortness of breath nausea or vomiting sweating feeling light-headed or dizzy palpitations or an abnormal heart rate Treatment When a heart attack is suspected, drugs such as aspirin may be given immediately to improve blood flow through the coronary arteries. Pain relief, oxygen and other treatments may also be given. When a heart attack has been diagnosed, one of two methods may be used to try to reopen the blocked artery. Drugs that dissolve the blood clots blocking the artery have greatly improved the treatment of heart attacks. These drugs, known as thrombolytics or 'clot busters', can restore blood flow in about 60 per cent of cases, although sometimes the artery blocks again later on. These drugs aren't suitable for everyone and there is a risk of bleeding. As many as two per cent of those treated will have a dangerous brain haemorrhage as a result. Thrombolytics must be given as soon as possible after symptoms start and certainly within 12 hours. The other method is an operation called percutaneous transluminal coronary angioplasty or PCI. It involves inserting a tube into the coronary arteries. The tube carries a deflated balloon that can be inflated in the blocked area to push against the artery walls and open the vessel. In general, PCI produces slightly better long-term results than thrombolytic drugs but it must be carried out in a specialised centre. Recovering from a heart attack Not so long ago, a heart attack meant weeks of bed rest. Nowadays, people may spend just a few days in hospital, but a much longer process of rehabilitation is important to help the person recover fully, deal with common problems such as depression and reduce the risk of a second attack.