Understanding MYOCARDIAL INFARCTION

Coronary Heart Diseases - Heart attack/myocardial infarction

There are 2 arteries supplying the heart; the right and the left coronary artery. RCA splits into a marginal branch which feeds blood to the right ventricle and the posterior interventricular branch, which supplies the left ventricle. The LCA is a larger artery. It splits into the anterior interventicular branch( anterior descending) and circumflex branch.

The coronary arteries are very vulnerable to blockage and narrowing through a process of ATHEROSCLEROSIS which can cause a depletion of blood to a certain part of the heart, possibly causing ischaemic heart diseases and heart attach

Myocardial Infarction (Heart Attack)
Myocardial infarction (MI) is usually caused by a blood clot that stops blood flow in a heart (coronary) artery. Call for an ambulance immediately if you develop severe chest pain. Treatment with a 'clot busting' drug or an emergency procedure to restore blood flow through the blocked artery are usually done as soon as possible to prevent damage to heart muscle. Other treatments help to ease the pain and prevent complications. Reducing risk factors can help to prevent ischaemic heart disease

What is Myocardial Infarction?
Myocardial infarction (MI) means that part of the heart muscle suddenly loses its blood supply. Without prompt treatment, this can lead to damage to the affected part of the heart. An MI is sometimes called a heart attack or a coronary thrombosis. An MI is part of a range or disorders called 'acute coronary syndromes'.

Understanding the heart and coronary arteries:
The heart is mainly made of special muscle. 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 aorta is 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 when you have a myocardial infarction?
If you have an MI, 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. This part of the heart muscle is at risk of dying unless the blockage is quickly undone. (The word 'infarction' means death of some tissue due to a blocked artery which stops blood from getting past.)If one of the 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. In people who survive an MI, the part of the heart muscle that dies ('infarcts') is replaced by scar tissue over the next few weeks

What causes myocardial infarction?

Thrombosis - the cause in most cases of infarction.
The common cause of an MI is a blood clot (thrombosis) that form inside a coronary artery, or one of its branches. This blocks the blood flow to a part of the heart.Blood clots do not usually form in normal arteries. However, a clot may form 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 MI. (The diagram above shows four patches of atheroma as an example. However, atheroma may develop in any section of the coronary arteries.)Treatment with 'clot busting' drugs or a procedure called angioplasty (see below) 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 causes
Various other uncommon conditions can block a coronary artery and cause an MI. 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; cocaine abuse which can cause a coronary artery to go into spasm; complications from heart surgery; and some other rare heart problems. There are not dealt with further.The rest of this leaflet deals only with the common cause - thrombosis over an atheroma

Who has a myocardial infarction?
MI is common. About 180,000 people in the UK are admitted to hospital each year with an MI. Most MIs occur in people over 50, and become more common with increasing age. Sometimes younger people are affected. An MI is three times more common in men than women. An MI may occur in people known to have heart disease such as angina. It can also happen 'out of the blue' in people with no previous symptoms of heart disease. (Atheroma often develops without any symptoms at first.)

What are the symptoms of a myocardial infarction?
Severe chest pain is the usual main symptom. 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. 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.)A small MI occasionally happens without causing pain (a 'silent MI'). It may be truly pain-free, or sometimes the pain is mild and you may think it is just heartburn or 'wind'.Some people collapse and die suddenly if they have a large or severe MI.

What should I do if I suspect I am having a myocardial infarction?
Call for an ambulance immediately. Then, if you have some, take one aspirin tablet (see below for the reason for this). You will normally be admitted straight to hospital.

How is 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. However, tests can usually confirm MI. These are:
A heart tracing called an ECG (electrocardiograph). There are typical changes to the normal pattern of the heart tracing if you have an MI. Patterns that occur with an MI include things called 'pathological Q waves' and 'ST elevation'. However, it is possible to have a normal ECG even if you have had a severe MI
Blood tests. A blood test that measures a chemical called troponin is the usual test that confirms an MI. This chemical is present in heart muscle cells and damage to heart muscle cells releases troponin into the bloodstream. 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 the MI (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 be measured in a blood test is called creatinine kinase. This too is released from heart muscle cells during an 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.Other 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 if this is suspected. For example, an echocardiogram (an ultrasound scan of 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-ECG'). Or, angiography of the coronary arteries. 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 myocardial infarction?
The following is a 'typical' situation and mentions the common treatments offered. Each case is different and treatments may vary depending on your situation
Aspirin and other anti-platelet drugs
As soon as possible after an 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 trigger the blood to clot. It is the platelets that become stuck onto a patch of atheroma inside an artery that go on to form the clot (thrombosis) of an MI. Another anti-platelet drug called clopidogrel is also usually given as soon as possible. This works in a different way to aspirin and adds to the action of reducing platelet stickiness. In Malaysia, a popular clopidogrel is Plavix 75mg
Pain relief
A strong pain killer given by injection into a vein will ease the pain such Morphine.
Treatment to restore blood flow in the blocked coronary artery
The part of the heart muscle starved of blood does not die ('infarct') immediately. If blood flow is restored within a few hours, much of the heart muscle that would have been damaged will survive. This is why an MI is a medical emergency, and treatment is given urgently. The quicker the blood flow is restored, the better the outlook. There are two treatments that can be done to restore blood flow back through the blocked artery.Emergency angioplasty is, ideally, the best treatment if it is available and can be done within a few hours of symptoms starting. In this procedure a tiny wire with a balloon at the end is put into a large artery in the groin or arm. It is then passed up to the heart and into the blocked section of a coronary artery using special x-ray guidance. The balloon is blown up inside the blocked part of the artery to open it wide again. A stent may be left in the widened section of the artery. A stent is like a wire mesh tube which gives support to the artery and helps to keep the artery widened. An injection of a 'clot busting' drug is an alternative to emergency angioplasty. In reality, this is the more common treatment as it can be given easily and quickly in most situations. Some ambulance crews are trained to give this treatment. Note: the common 'clot buster' drug used in the UK is called streptokinase. If you are given this drug you should not be given it again if you have another MI in the future. This is because antibodies develop to it and it will not work so well a second time. An alternative 'clot buster' drug should be given if you have another MI in the future.Both the above treatments usually work well to restore blood flow and greatly improve the outlook. The most crucial factor is the quickness in which one or other treatment is given after symptoms have developed.




Injection of heparin or a similar drug
These are usually given for a few days to help prevent further blood clots

Treatment after you have had a myocardial infarction:
Once you have had an MI, you will normally be advised to take regular medication for the rest of your life. After a Myocardial Infarction, briefly the following four drugs are commonly prescribed to prevent a further MI, and to help prevent complications.

Aspirin300mg - to reduce the 'stickiness' of platelets in the blood which helps to prevent blood clots forming. If you are not be able to take aspirin then an alternative anti-platelet drug such as clopidogrel (Pravix 75mg)may be advised.

A beta-blocker - to slow the heart rate, and to reduce the chance of abnormal heart rhythms developing.
An ACE inhibitor (angiotensin converting enzyme inhibitor). ACE inhibitors have a number of actions including having a protective effect on the heart. In Malaysia, popular ones are

Coversyl 4mg,8mg and Catapril 12.5mg,25mg,50mg
A statin drug to lower the cholesterol level in your blood. This helps to prevent the build-up of atheroma.
Also, you will normally be advised to take the anti-platelet drug clopidogrel in addition to aspirin. However, this is usually only advised for a certain number of weeks or months, depending on the type and severity of the MI.Many people recover well from an MI and have no complications. Before discharge from hospital it is common for a doctor or nurse to advise you how to reduce any risk factors (see below). This advice aims to reduce your risk of a future MI as much as possible.Other drugs or treatments may be needed if you develop complications. For example, treatments for heart failure may be needed if you develop heart failure as a complication after an MI

How serious is a myocardial infarction?
This often depends on the amount of heart muscle that is damaged. In many cases only a small part of the heart muscle is damaged (infarcts or dies) which heals as a small patch of scar tissue. The heart can usually function normally with a small patch of scar tissue. A larger MI is more likely to be life-threatening or cause complications.Even before treatments became available to restore blood flow such as 'clot busting' drugs and angioplasty, many people made a full recovery as many MIs are small. With the help of modern treatment, particularly if you are given treatment within a few hours to restore blood flow, a higher percentage of people now make a full recovery.Some possible complications that may occur after an MI include the following.

Heart failure. If a large area of the heart muscle is damaged, then the pumping ability of the heart may be reduced. Less blood than usual is then pumped around the body, especially when extra blood is needed when you exercise. Symptoms such as breathlessness, tiredness, and swollen ankles may develop. Mild heart failure can often be treated with medication. Severe heart failure can be serious and life-threatening.

Abnormal heart rhythms may occur if the electrical activity of the heart is affected. The main risk of this happening is within the first few hours after an MI. Sudden, chaotic, fast heart beats may occur. This is called ventricular fibrillation and is the common cause of 'cardiac arrest'. This needs immediate treatment with an electrical shock given by a defibrillator. Otherwise, collapse and sudden death is likely.

A further MI may occur sometime in the future. This is more likely if the coronary arteries are badly affected with atheroma, or further build up of atheroma continues. If the risk of this is thought to be high then surgery may be advised to bypass or widen severely narrowed coronary arteries.
The most crucial time is during the first day or so. If no complications arise, and you are well after a couple weeks, then you have a good chance of making a full recovery. A main objective then is to get back into normal life, and to minimise the risk of a further MI

After having a myocardial infarction.
After recovering from an MI, it is natural to wonder if there are any 'dos and don'ts'. In the past, well-meaning but bad advice to "rest and take it easy from now on" caused some people to become over-anxious about their hearts. Some people gave up their jobs, hobbies, and any activity that caused exertion for fear of 'straining the heart'.However, quite the opposite is true for most people who recover from an MI. Regular exercise and getting back to normal work and life is usually advised. Much can be done to reduce the risk of a further MI. Everybody has a risk of developing atheroma which can lead to an MI. However, certain 'risk factors' increase the risk and include:

Preventable or treatable risk factors:
-smoking
-hypertension (high blood pressure)
-high cholesterol level
-lack of exercise
-a poor diet
-obesity
-excess alcohol
-Having diabetes. But if you have diabetes, the increased risk of heart disease is minimised by good control of the blood sugar level, and reducing blood pressure if it is high.
-Risk factors that are fixed and you cannot change:
a family history of heart disease or a stroke that occurred in a father or brother aged below 55, or in a mother or sister aged below 65
-being male.
-ethnic group (for example, British Asians have an increased risk)
Briefly, if you can reduce any risk factors, it reduces your risk of having an MI (or of having a further MI if you have already had one). Some risk factors are fixed and you cannot change them. However, if you have a fixed risk factor, you may want to make extra effort to reduce preventable risk factors such as smoking or lack of exercise.

What is 'acute coronary syndrome'?
The term 'acute coronary syndrome' is a term that is used more and more by doctors. It covers a range of disorders (including MI) 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 caused by a blood clot that forms on a patch of atheroma within a coronary artery (which is described earlier). If the blood clot causes a reduced blood flow, but not a total blockage then the heart muscle supplied by the affected artery does not infarct (die). This situation causes 'acute coronary syndrome with unstable angina' - and typically leads to a sudden worsening of angina pains. If there is death of heart tissue then this is called an 'acute coronary syndrome with MI' (the subject of this leaflet). There is a third 'in between' category where just a very small amount of heart tissue infarcts. This is called 'acute coronary syndrome with myocyte necrosis'. In effect, this is like having a mild MI.One test that is used to distinguish between these three acute coronary syndromes is the blood test for troponin. This test is described earlier. If the level of troponin is normal, then there is no death of heart tissue. If the level is high, then it is classed as an MI. If there is just a slight rise in the level of troponin then this diagnoses 'acute coronary syndrome with myocyte necrosis.

Note from contributer: Complementary herbal medicines are proven to assist in improving 4 areas in prevention, treatment of ischaemic heart diseases and secondary prevention of further myocardial infarction. These herbs can be taken along with western medicine.

These 4 areas are :-

(1) Help preventing atherosclerosis.

(2) Enhance anti-platelet activity of blood to prevent clotting.

(3) Enhance thrombolytic activity of blood to prevent thrombosis.

(3) Improve angiogenesis (produce new vessels). Help establishment of collateral circulation during ischaemic crisis

For further information, please contact the contributer