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Myocardial Infarction (Heart Attack)

stethescope Physicians who treat this condition

 

A myocardial infarction, commonly known as a heart attack, is a medical emergency that occurs when a portion of the heart is deprived of oxygen because of blockage of one of the coronary arteries, which supply the heart muscle (myocardium) with blood. Lack of oxygen causes characteristic chest pain and death of myocardial tissue.

The process of atherosclerosis, or buildup of plaque on arterial walls which causes clotting, may be halted or even reversed with fairly simple measures to reduce the risk of heart attack. If treatment is received within a few hours of the onset of a heart attack, chances for survival are good. However, prompt emergency medical attention is crucial.

Improved treatment methods, including the administration of thrombolytic (clot dissolving) drugs and angioplasty (inflation of a tiny balloon at the site of the blockage to widen the artery and permit the flow of blood through the artery), have led to a steady decrease in mortality from heart attacks. However, the best treatment remains prevention.

When to Call an Ambulance
Symptoms
Causes
Prevention
Diagnosis
Treatment

When to Call an Ambulance

  • If you experience crushing chest pain, with or without nausea, vomiting, profuse sweating, breathlessness, weakness or intense feelings of dread.
  • If chest pain from previously diagnosed angina does not subside after 10 to 15 minutes.
  • If it’s the first time you experience intense chest pain.

Symptoms
One-third of all heart attacks occur with no prior warning signs. In the remainder, attacks of chest pain (angina) brought about by stress or exertion occur periodically for months or years prior to a heart attack. In some cases, a mild heart attack produces no symptoms and is often referred to as a “silent heart attack.”
Here are a few of the warning signs you should know:

  • Chest pain or pressure, tightness, squeezing, burning, aching, or heaviness in the chest lasting longer than 10 minutes. The pain or discomfort is usually located in the center of the chest just under the breastbone and may radiate down the arm (especially the left), up into the neck, or along the jaw line.
  • Shortness of breath.
  • Profuse sweating.
  • Dizziness.
  • Muscle weakness.
  • Nausea and vomiting.
  • A choking sensation.
  • Anxiety or a feeling of impending doom.
  • No symptoms occur with a silent heart attack. 

Call for emergency assistance if rest and/or medications do not relieve symptoms in 5-10 minutes.

Causes
Heart attacks are more likely to occur when arteries have already been substantially narrowed by years of coronary artery disease. In a process known as atherosclerosis, plaque (which is composed of cholesterol-rich fatty deposits, collagen and other proteins, and excess smooth muscle cells) builds up in the arterial walls, causing those walls to thicken and narrow, inhibiting the flow of blood into the heart.

Plaque deposits roughen arterial walls, making it much easier for blood clots to form along the surface of the plaque. If the clots grow, or if they detach from their place of origin and are carried along to a narrower section of artery, they may block a coronary artery completely, causing a heart attack. Arteries may also narrow suddenly as a result of an arterial spasm.

Risk for heart attacks increases with age (heart attacks most commonly occur after age 65) in both men and women, though men have a significantly higher risk of heart attack than pre-menopausal women. The risk for postmenopausal women approaches that of men as estrogen production decreases with menopause.

Other factors and causes that may increase your risk for heart attack can include cigarette smoking, high blood pressure, high blood cholesterol levels, a diet rich in saturated fat (especially animal fat), obesity, lack of exercise and diabetes mellitus.

  • A family history of early or premature heart attacks (before the age of 55 in men and 65 in women) increases the risk of heart attack.
  • A spasm of the muscles of the arterial walls may cause a heart attack by narrowing an artery. Spasms may be triggered by smoking, extreme emotional stress, or exposure to very cold air or water.
  • Abuse of cocaine or amphetamines may cause a sudden heart attack even in those with no signs of heart disease.
  • Heavy exertion, such as shoveling snow or carrying heavy objects up stairs, and severe emotional stress may trigger a heart attack.
  • Having had one heart attack increases the risk of future heart attacks.

Prevention
You can help prevent a heart attack by knowing your risk factors for coronary artery disease and heart attack and taking action to lower those risks. Even if you’ve already had a heart attack or are told that your chances of having a heart attack are high, you can still lower your risk, most likely by making a few lifestyle changes that promote better health.

  • Don’t smoke. Your doctor may recommend methods for quitting, including nicotine replacement.
  • Eat a diet low in fat, cholesterol and salt.
  • See your doctor regularly for blood pressure and cholesterol monitoring.
  • Pursue a program of moderate, regular aerobic exercise. People over age 50 who have led a sedentary lifestyle should check with a doctor before beginning an exercise program.
  • Lose weight if you are overweight.
  • Your doctor may advise you to take a low dose of aspirin regularly. Aspirin reduces the tendency for the blood to clot, thereby decreasing the risk of heart attack. However, such a regimen should only be initiated under a doctor’s expressed recommendation.
  • Women at or approaching menopause should discuss the possible cardio-protective benefits of estrogen replacement therapy with their doctor

Diagnosis
At Johns Hopkins, heart attack (or myocardial infarction) is most commonly treated first at the Johns Hopkins Emergency Department. Patients may then be moved to the Coronary Care Unit for further management.

  • The doctor will take a patient history and perform a physical exam. The diagnosis will sometimes be made immediately by a doctor or emergency response technician but frequently requires further blood tests to confirm.
  • An electrocardiogram, also called an ECG or EKG, may be ordered to record the heart’s electrical activity, identifying any abnormal heart rhythms that result from abnormalities in the flow of blood.
  • Blood tests may be ordered to measure the release of certain proteins from damaged heart muscle into the bloodstream.
  • Coronary angiography, or X-ray of the heart’s blood vessels, may be performed to evaluate possible narrowings of the coronary arteries. In this procedure a tiny catheter is inserted into an artery of a leg or arm and threaded up into the coronary arteries. A contrast material is then injected from the end of the catheter into the coronary arteries, and X-rays are taken.

Treatment
Time is critical during treatment of heart attack. Most heart attack deaths result from an abnormal heart rhythm during delays in reaching the hospital. Call 911 if there is any suspicion of a heart attack. A stopped heartbeat must be restarted immediately by cardiopulmonary resuscitation (CPR) or by a device known as an electrical defibrillator. The longer the time from the onset of a heart attack to re-establishing blood flow to the heart, the more permanent heart damage can occur.

  • Chew on an aspirin at the onset of the symptoms of a heart attack as it may help break up a blood clot.
  • Thrombolytic, or clot-dissolving, drugs such as tissue plasminogen activator (tPA), streptokinase or urokinase may be injected immediately to dissolve arterial blockage. This technique is most effective within three hours of the onset of a heart attack.
  • Painkillers such as morphine or meperidine may be administered to relieve pain.
  • Nitroglycerin may be given to reduce the heart’s oxygen demands and to lower blood pressure.
  • Antihypertensive drugs such as beta-blockers, ACE inhibitors or calcium channel blockers may also be administered to lower blood pressure and to reduce the heart’s oxygen demand. Diuretics may enhance the effect of these drugs.
  • Oxygen may be administered through nasal tubes.
  • Anticoagulants such as heparin, aspirin or warfarin may be administered to reduce the risk of blood clots.
  • Digitalis glycosides, such as digoxin, may be prescribed in some cases to strengthen heart muscle contraction.
  • Dopamine or dobutamine may be administered to increase blood flow to the heart and strengthen the heartbeat.
  • Angioplasty, a procedure to open up narrowed arteries, may be performed. Using local anesthesia, the doctor will insert a catheter -- a long, narrow tube with a deflated balloon at its tip -- into the narrowed part of the artery. Then the balloon is inflated, compressing the plaque and enlarging the inner diameter of the blood vessel so blood can flow more easily.
  • Coronary bypass surgery may be performed to go around blocked blood vessels and restore adequate blood flow to the heart.
  • Electronic implants such as a pacemaker or a defibrillator may be attached to the heart to maintain strong, regular contractions of the heart muscle.
  • Severe cases that badly damage heart tissue may require a heart transplant.
  • During recovery, follow prevention tips given by your doctor to reduce the risk of another heart attack.

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