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 anambulanceimme diately 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 riskfactors can help to prevent a myocardial infarction.Unde rstanding the heart and coronary arteriesThehear tis 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 othermuscle, 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 heartmuscle.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.Top Cardiologists in Delhi/ NCRSome newer terms used by doctorsA heart attack and myocardial infarction (MI) are commonly used terms, and mean the same thing. However, the term MI is used less often now by doctors. This is because there are actually a range ofconditions that can be caused by a sudden reduction in blood flow in a coronary artery. This range of conditions has an overall term calledacute coronary syndrome (ACS). Two main sub types of ACS can be diagnosed by what is seen on your heart tracing (ECG). The two main types are called ST-elevation MI (STEMI) and non-ST-elevation MI (NSTEMI). NSTEMI can also include unstable angina. (The ST elevation refers to a section on theECGtracing.) In STEMI, the artery supplying an area of the heart muscle is completely blocked. However, in NSTEMI, the artery is only partly blocked, so only part of the heart muscle supplied by the affected artery is affected. Your treatment can depend upon which type you have - STEMI or NSTEMI.How is myocardial infarction caused? Blood clot (thrombosis) - the cause in most casesThe most common cause of an MI is a blood clot (thrombosis) that forms inside a coronary artery, or one of itsbranches. This blocks the blood flowto a part of the heart.Blood clots do not usually form in normal arteries. However, a clot mayform if there is 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.What happens is that a crack develops in the outer shell of the atheroma plaque. This is called plaque rupture. This exposes the softer inner core of the plaque to blood. This can trigger the clotting mechanism in the blood to form a blood clot. Therefore, a build-up of atheroma is the root problem that leads to most cases of ACS / MI.Treatment with clot-busting medication or a procedure called angioplasty can break up the clot and restore blood flow through the artery. If treatment is given quickly enough this prevents damage to the heart muscle, or limits the extent of the damage.Uncommon causesVarious other uncommon conditionscan 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.Top Cardiologists in Delhi/ NCRWho is at risk of having a myocardialinfarction / heart attack?Most occur in people aged over 50 and it becomes more common with increasing age. Sometimes younger people are affected.MI is three times more common in young men than in young women. However, after themenopause, the female hormones no longer protect the heart so the risk is then the samefor men and women.MI may occur in people known to have heart disease, such as people with angina. It can also happen out of the blue in people with no previous symptoms of heart disease. This is because atheroma often develops without any symptoms at first.Certain risk factors increase the risk of more atheroma forming. This can lead to ACS / MI. Briefly, risk factors that can be modified and may help toprevent MI include:*.Smoking . If you smoke, you shouldmake every effort to stop.*.High blood pressure. If your blood pressure is high it can be treated.*.If you areoverweight, losing some weight is advised. Losing weight will reduce the amount of workload on your heart and also help to lower your blood pressure.*.Ahig h cholesterol. This should usually be treated if it is high.*.Inactivi ty. You should aim to do some moderate physical activity onmost days of the week for at least 30 minutes - for example, brisk walking, swimming, cycling, dancing, gardening, etc.*.Diet. You should aim to eat ahealthy diet.*.Diabetes . People with diabetes have a higher risk of having ACS. This risk can be reduced by ensuring your blood pressure, cholesterol levels and glucose levels are well controlled.*.Fa mily history. Your risk is increased if there is a family historyof heart disease or a stroke that occurred in your father or brother aged below 55, or in your mother orsister aged below 65.*.Ethnic group. Certain ethnic groups- for example, British Asians - havea higher risk of developing cardiovascular diseases.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 yourchest. 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 aftera 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.Occas ionally, an MI happens withoutcausing any pain. This is usually diagnosed when you have anelectrocardio gram(ECG, or heart tracing) at a later stage.Some people collapse and die suddenly, if they have a large portionof heart muscle damaged. This is not very common.What should I do if I think I am having a myocardial infarction?Call for anambulanceimme diately.Then, if you have some, take one aspirin tablet . You will normally be admitted straight to hospital.How is a myocardial infarction diagnosed and assessed?Many people develop chest pains that are not due to an MI. For example, you can have quite bad chest pains with heartburn, gallbladder problems or with pains from conditions of the muscles in the chest wall. Therefore, tests are usually done to confirm an MI. These are:*.AnECG. There are typical changes to the normal pattern of the heart tracing in MI. Patterns that occur include things called pathological Q waves and ST elevation. However, it is possible to have a normal ECG even if you have had an MI.*.Blood tests. A blood test that measures a chemical called troponin is the usual test that confirms MI. This chemical is present in heart muscle cells. Damage to heart muscle cells releases troponin into the bloodstream. In MI the blood level of troponin increases within 3-12 hours from the onset of chest pain, peaks at 24-48 hours, and returns to a normal level over 5-14 days.A rough idea as to the severity of theMI (the amount of heart muscle that is damaged) can be gauged by the degree of abnormality of the ECG and the level of troponin in the blood. Another chemical that may bemeasured in a blood test is called creatine kinase. This too is released from heart muscle cells during MI.Your heart tracing will be monitored for a few days to check on the heart rhythm. Various blood tests will be done to check on your general well-being.Othe r tests may be done in some cases. This may be to clarify the diagnosis (if the diagnosis is not certain) or to diagnose complications such as heart failure ifthis is suspected. For example, an echocardiogram (an ultrasound scanof the heart) or a test called myocardial perfusion scintigraphy may be done.Also, before discharge from hospital,you may be advised to have tests to assess the severity of atheroma in the coronary arteries. For example, an ECG taken whilst you exercise on a treadmill or bike (exercise tolerance test). Anangiographyof the coronary arteries may also be performed. In this test a dye is injected into the coronary arteries. The dye can be seen by special X-ray equipment. This shows up the structure of the arteries (like a road map) and can show the location and severity of any atheroma.What is the treatment for a myocardial infarction?The following is a typical situation and mentions the common treatments that are usually offered. However, each case is different and treatments may vary depending on your situation.Aspir in and other antiplatelet medicinesAs soon as possible after MI is suspected you will be given a dose of aspirin. Aspirin reduces the stickiness of platelets. Platelets are tiny particles in the blood that triggerthe blood to clot. It is the platelets that become stuck on to a patch of atheroma inside an artery that go on to form the clot.Other antiplatelet medicines called clopidogrel or ticagrelor may be given. They work in a different way to aspirin and help reduce platelet stickiness.Inje ctions of heparin or a similar medicineThese are usually given for a few days to help prevent further blood clots from forming.
Posted on: Wed, 11 Sep 2013 16:03:33 +0000
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