Acute Coronary Syndrome

acute coronary syndrome

A heart attack (myocardial infarction) is usually caused by a blood clot, which stops the blood flowing to a part of your heart muscle. First and foremost call for an ambulance immediately if you develop severe chest pain.

The heart is 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 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 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 in 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. Now this part of your heart is at risk of dying within a couple of minutes unless the blockage is quickly removed. If the main coronary arteries are 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.

What causes a myocardial infarction?
  • Blood clot - the cause in most cases
  • The most common cause of an MI is a blood clot (thrombosis) that forms inside a coronary artery, or one of its branches. This blocks the blood flow to a part of the heart. Blood usually does not clot in normal arteries. However, a clot may form if there are some fatty deposits called atheroma within the lining of the artery. An atheroma over time acquires a brittle outer shell and comes to be called as plaques. The critical event is a crack developing 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.

    Treatment with clot-busting medications or a procedure called angioplasty opening up a blocked artery with a balloon or a stent or both and restore blood flow through the artery. Early treatment is the key as if given quickly enough this prevents damage to the heart muscle, or limits the extent of the damage.

  • Inflammation of the coronary arteries;
  • 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;
  • Cocaine addiction, which can cause a coronary artery to go into spasm;
Who is at risk of having a myocardial infarction / heart attack?

MI is common. Most occur in people aged over 50 and it becomes more common with increasing age. MI is three times more common in young men than in young women. However risk equalizes after females achieve menopause.

Briefly, risk factors that can be modified and may help to prevent MI include:

  1. Smoking.
  2. High blood pressure.
  3. Being overweight.
  4. High cholesterol.
  5. Sedentary lifestyle.
  6. A high fat/carbohydrate diet.
  7. Diabetes.
  8. Family history.
What are the symptoms of a myocardial infarction?

The most common symptom is severe chest pain, which often feels like a crushing pressure feeling on your chest. The pain may travel up into your jaw and down your left arm or down both arms. You may also sweat, feel sick and feel faint. However, some people (chiefly diabetics) have only a mild discomfort in their chest. The pain can sometimes feel like indigestion or heartburn.In a good percentage of people MI happens without causing any pain. This is usually diagnosed when you have an electrocardiogram (ECG, or heart tracing) at a later stage. In rare cases people collapse and die suddenly, if they have a large portion of heart muscle damaged.

How do I respond if I think I am having a myocardial infarction?
  • Call for an ambulance immediately.
  • If there is one medicine that may help you survive an episode, it is aspirin. Take one aspirin tablet. It works by making the blood non-sticky and preventing further clot formation.
How is a myocardial infarction diagnosed and assessed?

ECG(a study of the electrical rhythm of the heart). A MI causes some characteristic changes in the electrical waves of the heart indicating the area involved and the extent of involvement. It is important to remember that MI can occur without any ECG changes too.

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.

Another chemical that may be measured in a blood test is called creatine kinase. This too is released from damaged heart muscle cells.

Also, before discharge from hospital, you may be advised to have tests to assess the severity of atheroma in the coronary arteries. An angiography of the coronary arteries may also be performed. In this test a radio-opaque dye (that shows up on a sophisticated X-Ray Machine) is injected into the coronary arteries. This shows the state of the coronary arteries and can show the location and severity of any blockage.

What is the treatment for a myocardial infarction?
  1. Aspirin and other antiplatelet medicines (As 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 trigger clotting. Other antiplatelet medicines called clopidogrel or ticagrelor may be given).
  2. Injections of heparin
  3. A strong painkiller such as morphine or pethidine is given by injection into a vein.

Treatment to restore blood flow in the blocked coronary artery.If blood flow is restored to the blocked area is restored within a few hours, much of the heart muscle that would have been damaged can be rescued.

There are two major treatments that can restore blood flow back through the blocked artery:
  • Emergency angioplasty
  • 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 inflated 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 which gives support to the artery and helps to keep the artery widened.

  • An injection of a clot dissolving medicine is an alternative to emergency angioplasty.
  • It can be given easily and quickly in most situations. Some highly trained ambulance crews are capable of giving this, thereby cutting short the time to respond.

You may be given oxygen by a face mask. Oxygen works to reduce the risk of damage to your heart muscle. How critical is a myocardial infarction?

This is directly related to the extent of damage you have suffered. In some cases, only a small part of the heart muscle is damaged and then heals as a scar. The heart can function perfectly normally with a small patch of scar tissue. A larger heart attack is more likely to be life-threatening or cause complications such as heart failure or chronic rhythm disturbances.

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