Heart Infarct: Description:
Commonly known as heart attack or myocardial infarction.
A heart infarct, or myocardial infarction, occurs when one of more regions of the heart muscle experience a severe or prolonged lack of oxygen caused by blocked blood flow to the heart muscle.
The blockage is often a result of atherosclerosis - a buildup of plaque, known as cholesterol, other fatty substances, and a blood clot. Plaque ruptures and eventually a blood clot forms. The cause of a heart infarct is a blood clot that forms within the plaque-obstructed area.
If the blood and oxygen supply is cut off severely or for a long period of time, muscle cells of the heart suffer damage and die. The result is dysfunction of the muscle of the heart in the area affected by the lack of oxygen.
Symptoms of a heart infarct:
The following are the most common symptoms of a heart infarct. However, each individual may experience symptoms differently. Symptoms may include:
Indigestion: Indigestion, also known as upset stomach or dyspepsia, is a painful or burning feeling in the upper abdomen that may include nausea; abdominal bloating; belching; vomiting; severe pain in the upper right abdomen; discomfort unrelated to eating; and indigestion accompanied by shortness of breath, sweating, or pain radiating to the jaw, neck, or arm.
The symptoms of indigestion may resemble other medical conditions, such as chest pain. Always consult your physician for diagnosis.
1. Severe pressure, fullness, squeezing, pain and/or discomfort in the center of the chest that lasts for more than a few minutes
2. Pain or discomfort that spreads to the shoulders, neck, arms, or jaw.
3. Chest pain that increases in intensity.
4. Chest pain that is not relieved by rest or by taking nitroglycerin.
5. Chest pain that occurs with any/all of the following (additional) symptoms: Sweating, cool, clammy skin, and/or paleness.
6. Shortness of breath.
7. Nausea or vomiting.
8. Dizziness or fainting.
9. Unexplained weakness or fatigue.
10. Rapid or irregular pulse.
11. Although chest pain is the key warning sign of a heart infarct, it may be confused with indigestion, pleurisy, pneumonia, or other disorders.
The goal of treatment for a heart infarct is to relieve pain, preserve the heart muscle function, and prevent death.
Treatment in the emergency department may include:
Intravenous therapy - nitroglycerin, morphine.
Continuous monitoring of the heart and vital signs.
Oxygen therapy - to improve oxygenation to the damaged heart muscle.
Pain medication - by decreasing pain, the workload of the heart decreases, thus, the oxygen demand of the heart decreases.
Cardiac medication - such as beta-blockers or calcium channel blockers to promote blood flow to the heart, improve the blood supply, prevent arrhythmias, and decrease heart rate and blood pressure.
fibrinolytic therapy - intravenous infusion of a medication which dissolves the blood clot, thus, restoring blood flow.
Antithrombin/antiplatelet therapy - used to prevent further blood clotting.
Antihyperlipidemics - medications used to lower lipids (fats) in the blood, particularly Low Density Lipid (LDL) cholesterol. Statins are a group of antihyperlipidemic medications, and include Simvastatin (Zocor®), atorvastatin (Lipitor®), and pravastatin (Pravachol®), among others. Bile acid sequestrants - colesevelam, cholestyramine and colestipol - and nicotinic acid (niacin) are two other types of medications that may be used to reduce cholesterol levels.
Once the heart infarct has been diagnosed and the patient stabilized, additional procedures to restore coronary blood flow may be utilized. Those procedures include:
1. Coronary angioplasty - with this procedure, a balloon is used to create a bigger opening in the vessel to increase blood flow. Although angioplasty is performed in other blood vessels, Percutaneous Transluminal Coronary Angioplasty (PTCA) refers to angioplasty in the coronary arteries to permit more blood flow into the heart. There are several types of PTCA procedures, including:
Balloon angioplasty - a small balloon is inflated inside the blocked artery to open the blocked area.
Atherectomy - the blocked area inside the artery is cut away by a tiny device on the end of a catheter.
Laser angioplasty - a laser used to "vaporize" the blockage in the artery.
Coronary artery stent - a tiny coil is expanded inside the blocked artery to open the blocked area and is left in place to keep the artery open.
2. Coronary artery bypass - Most commonly referred to as simply "bypass surgery," this surgery is often performed in people who have angina (chest pain) and coronary artery disease (where plaque has built up in the arteries). During the surgery, a bypass is created by grafting a piece of a vein above and below the blocked area of a coronary artery, enabling blood to flow around the obstruction. Veins are usually taken from the leg, but arteries from the chest or arm may also be used to create a bypass graft.
Once you have had an MI, you will normally be advised to take regular medication for the rest of your life. Medication after an MI is discussed more fully in another leaflet called 'Medication After a Myocardial Infarction'. Briefly, the following four drugs are commonly prescribed to prevent a further MI, and to help prevent complications.
Aspirin - 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 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.
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 antiplatelet 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 a heart infarct 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.
Heart infarct - Causes and risk factors:
The 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 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.
Various other uncommon conditions can block a coronary artery and cause a heart infarct. 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 plaque.
The following increase your risk of having a heart infarct.
2. High-fat diet, excess body weight.
3. Family history of early MI.
5. Oral contraceptives.
6. Hypertension (high blood pressure).
7. Being male, or a female who has gone through menopause.
8. Cocaine or amphetamine abuse.
Many people develop chest pains that are not due to a heart infarct. 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 a heart infarct. 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 an 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 heart infarct (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 wellbeing.
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.
Medicine and medications:
Your health care provider may prescribe one or several drugs to help bring blood back to the blocked artery, keep your heartbeat regular, lower your blood pressure, control pain, and improve blood flow.
Streptokinase (SK) - improves widening of the coronary artery; takes 70 minutes to feel the effects; given intravenously.
Tissue plasminogen activator - improves widening of the coronary artery; takes 45 minutes to feel the effects.
Anisoylated plasminogen streptokinase activator complex - more expensive but longer anti-clotting activity than streptokinase.
Heparin - improves widening of the coronary artery.
Nitroglycerin - improves blood flow, helping to prevent blood clots that block arteries.
Beta blockers - reduce cardiac rupture, new heart infarcts, irregular heart beat; various side effects.
Angiotensin-converting enzyme (ACE) inhibitors - reduce high blood pressure.
Pain control - morphine sulfate, intravenous.
Oxygen - by a tube inserted into your nose, as needed.
Aspirin - improves blood flow, helping to prevent blood clots that block arteries; it works best if you chew it.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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