Heart Attack

18 May

Heart Attack
A heart attack is sudden death of a portion of the heart muscle that has been deprived of its blood supply. Most heart attacks are caused by blockage of a coronary artery. The blockage may be caused by a slow-growing plaque (fatty deposit) that blocks blood flow in the artery or by a quicker event, such as when a plaque ruptures or tears, causing a blood clot to form and clog the artery. Nearly 95 percent of sudden heart attacks are caused by a ruptured plaque and subsequent blood clot formation, which slows or prevents blood flow to the heart muscle.

When a blood clot forms on the rough surface of a plaque in the arterial wall, blocking an artery completely and suddenly, the result is often a sudden heart attack. Doctors also call this a “coronary thrombosis” or a “coronary occlusion.” Heart damage occurs very quickly following blockage of a coronary artery. The

affected heart tissue begins to deteriorate, and damage becomes permanent after about 6 minutes. This is why the speed of response to a heart attack is critical. The more quickly a person is treated, the better the chances of limiting damage to the heart.

For the heart muscle to function properly, it needs a continuous supply of oxygen-rich blood from the coronary arteries. The body has a remarkable ability to adapt to changing conditions—even narrowing of the coronary arteries—to ensure this continuous supply of blood. For example, if an artery starts to close gradually by thickening of its inner lining, and sometimes if it is closed by a blood clot, neighboring arteries gradually increase in size and send out new branches to supply adequate blood to the threatened area. This process is known as the formation of “collateral circulation.”

In most cases, when a blood clot blocks a branch of the coronary artery, the symptoms appear suddenly, although it may take minutes, hours, or even days for the clot to grow large enough to block the artery. The time required for block- age to occur depends on the width of the channel inside the artery. If the artery is small and has narrowed gradually over a period of years, so that good collat- eral circulation is already present, blockage by a blood clot may cause mild symptoms or none at all. On the other hand, if the artery is large and there has been only slight narrowing, sudden obstruction by a blood clot may cause severe discomfort.

Rarely, a heart attack may occur when a clot from another part of the heart breaks away and lodges in the coronary artery. Another uncommon cause of a heart attack is a spasm in a coronary artery that stops blood flow. The causes of such spasms are usually unknown.

The symptoms and extent of a heart attack depend on factors such as the size of the blocked artery, the width of the channel inside the artery, the suddenness of the blockage, the extent to which an adequate collateral circulation has formed, and the general condition of the heart at the time of the attack.

The pain of a heart attack is usually, but not always, severe. Like angina, the pain occurs in the center of the chest and may spread to the back, left arm, or jaw; less often the pain spreads to the right arm. Because many people have strong denial capabilities (“It can’t be happening to me!”), they may downgrade the severity of the pain and attribute it to some other cause, such as indigestion. Other symptoms of a heart attack include a heavy pounding of the heart, feeling faint or fainting, restlessness or anxiety, and sweating. The lips, hands, or feet may turn slightly blue. Older people may become disoriented or confused. Irreg- ular heartbeats (arrhythmia) may seriously interfere with the heart’s ability to pump effectively and may precede a heart attack.

Two of three people who have heart attacks experience intermittent chest pain, shortness of breath, or fatigue a few days beforehand. Some people may think these symptoms are nothing more than an angina episode. The key is to be able to recognize the difference between angina and the pain caused by a heart attack, which is usually more severe, lasts longer, and does not go away with rest or after taking nitroglycerin.

One of five people who have a heart attack has only mild symptoms or none at all. Such “silent” heart attacks are often diagnosed after the fact through a rou- tine electrocardiogram (ECG; an examination of the electrical activity of the heart). Many of these silent attacks go unnoticed because they affect a less cru- cial part of the heart or because the person having the attack may have an unusu- ally high tolerance for pain.

Warning Signs of a Heart Attack
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ecome familiar with the warning signs of a heart attack so you can seek immediate help if you or someone you know begins to experience them. The most common symptoms of a heart attack include:

•   sudden, strong pain, pressure, fullness, or squeezing in the center of the chest that lasts more than just a few minutes and is not relieved by rest

•   chest pain that spreads to the shoulders, neck, jaw, or arms

•   chest discomfort accompanied by shortness of breath, light-headedness or fainting, sweating, cold or clammy skin, nausea or vomiting, or loss of consciousness

Less common heart attack symptoms are:

•   other kinds of chest pain or stomach or abdominal pain

•   unexplained anxiety, weakness, or fatigue

•   palpitations, a cold sweat, or pale skin

A heart attack is a medical emergency. If you have any of the symptoms described above, call 911 or your local emergency number, or call an ambulance service, and ask for immediate transportation to a hospital emergency department. If you are with a person who has any of these symptoms, call 911 or your local emergency number, or take him or her to the nearest hospital emergency department without delay.

Other conditions may mimic a heart attack. These conditions include pneu- monia, a blood clot in the lung (pulmonary embolism), inflammation of the membrane that surrounds the heart (pericarditis), fracture of a rib, spasm of the esophagus, indigestion, gastroesophageal reflux disease, and chest muscle ten- derness after injury or exertion. An ECG and measurement of certain enzymes in the blood can confirm the diagnosis of a heart attack within a few hours. In many instances, an ECG can show when a person is having a heart attack. Several abnormalities may appear on the ECG, depending on the extent and the location of heart muscle damage. If a person has had a previous heart attack, however, the current heart muscle damage may be difficult to detect. If the results of a few

ECGs taken over the course of several hours are normal, the doctor usually con- siders a heart attack less likely but will wait for the results of blood enzyme tests before making a diagnosis.

The levels of certain enzymes in the blood can be measured to help diagnose a heart attack. For example, an elevated level of heart-muscle enzymes called troponins in the blood is an indication of damage to the heart muscle that results from a heart attack. The level of troponins increases about 4 to 6 hours after a heart attack, peaks 10 to 24 hours after the attack, and can be detected in the blood for about a week. Troponin levels are usually checked when a person is admitted to the hospital with chest pain and a possible heart attack and at 8-hour intervals for about 24 hours.

Another heart-muscle enzyme, called CK-MB, is also released into the blood when heart muscle is damaged. Elevated levels show up in the blood within 6 hours of a heart attack and they persist for 36 to 48 hours. Levels of CK-MB usually are checked when the person is admitted to the hospital and at 6- to

8-hour intervals over the next 24 hours.

If ECG and enzyme test results do not provide enough information to diag- nose a heart attack, imaging techniques such as echocardiography (an ultrasound examination of the heart) or radionuclide scanning (see page 213) may be per- formed. An echocardiogram may show reduced motion in part of the wall of the left ventricle (the part of the heart that pumps blood to the body), suggesting damage from a heart attack. A radionuclide scan may show a persistent reduction in blood flow to a specific area of the heart muscle, suggesting a scar (dead tis- sue) caused by a heart attack.

Why You Should  Take CPR Training
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ardiopulmonary resuscitation (CPR) is a critically important technique that could help you save the life of someone you love. CPR is used to revive a person when his or her breathing or heartbeat stops—a sign of sudden death. Sudden death can be caused by a number of events, including a heart attack, poisoning, drowning, choking, suffocation, electrocution, and smoke inhalation. The CPR procedures attempt to restart the person’s breathing and heartbeat, employing techniques that keep the person’s airway open, use rescue breathing to administer oxygen, and apply rhythmic pressure to the chest to force

the heart to pump blood. Use CPR until emergency medical personnel arrive.

Your local hospital or fire department, the local chapters of the American Red Cross or the American Heart Association, or your employer all may offer CPR training courses. Ask your doctor about CPR classes in your community. Take advantage of these opportu- nities for training because your knowledge could make the difference between life and death for someone. Once you learn the CPR procedures, practice them often so you won’t forget the correct procedures when you need them the most. CPR should be performed only by people trained in this procedure.

When dealing with a possible heart attack, speed is vital. Half of the deaths caused by heart attacks occur within the first 3 or 4 hours after symptoms begin. The faster a heart attack victim gets to a hospital emergency department, the better the chances of survival. Anyone experiencing symptoms of a possible heart attack (see “Warning Signs of a Heart Attack,” page 209) should seek immediate medical attention. If aspirin is available, encourage the person to swallow one tablet. Aspirin helps reduce the blood’s tendency to clot, thereby reducing the chances of dying of a heart attack by 20 percent.

A person suspected of having a heart attack is usually admitted to a hospital’s cardiac care unit (CCU). In the CCU, a person’s heart rhythm and blood pres- sure and the amount of oxygen in the blood are closely monitored to assess heart damage. Nurses in these units are specially trained to deal with cardiac emergencies. Upon arrival, the patient is immediately given a thrombolytic (clot- dissolving) medication such as tissue plasminogen activator (tPA), streptokinase, or urokinase. These drugs are most effective if given within 6 hours of the start of the heart attack symptoms. If a blocked coronary artery can be cleared quickly, damage to heart tissue may be prevented or limited. After 6 hours, restoring blood flow to the heart does not help very much. Early treatment with thrombolytic drugs can increase blood flow and limit heart tissue damage. Aspirin, which prevents platelets from forming blood clots, or heparin, which also stops clotting, may enhance the effectiveness of treatment with thrombolytic drugs.

A beta-blocker drug also is given to slow down the heart rate and make the heart work less hard to pump blood through the body. Reducing the heart’s work- load also helps limit damage to the heart. Oxygen is given through a face mask, or via a tube with prongs inserted into the nostrils. This therapy increases the oxygen content in the blood, which provides more oxygen to the heart and helps to keep heart tissue damage to a minimum. Some physicians recommend coro- nary angioplasty (see page 216) to open the coronary arteries or coronary artery bypass surgery (see page 216) after a heart attack instead of treatment with thrombolytic drugs.

Depending on the extent of the heart attack, you may be released from the hospital for home rest within days. Your doctor will probably advise you to stay in bed and rest for several days and to avoid excitement, physical exertion, and emotional stress. If you smoke, your doctor will tell you to quit immediately (see page 107); smoking is a major risk factor for coronary artery disease and heart attack.

It is normal to feel anxious and depressed after a heart attack. Because severe anxiety can stress the heart, the doctor may prescribe a mild tranquilizer. To deal with the depression and with denial of illness, which also is common after a heart attack, patients and their families are encouraged to talk about their feel- ings with doctors, nurses, and social workers. Many hospitals where cardiac surgery is performed offer support groups in which people who have recovered from heart attacks or cardiac surgery have been trained to work as peer coun- selors for recuperating inpatients.

In general, most people who survive for a few days after a heart attack can expect to recover fully. However, about 10 percent, usually those who continue to have angina, irregular heart rhythm, or heart failure, will die within a year. Most of those deaths will occur within the first 3 to 4 months. To promote recovery and  to  help  avoid  possible  future  heart attacks, survivors usually are  prescribed heart  medications,  cholesterol-lowering page 214), a low-fat diet, and regular ses-drugs (see “Medications for Heart Disease,” sions of aerobic exercise in a cardiac reha- bilitation program.

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