Heart AttackOverview, Signs, Symptoms, and What to Do |
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Overview
The heart is a complex, highly specialized, muscular organ in the chest that maintains the circulation of blood throughout the body. Heart attack, or acute myocardial infarction, is the death of heart tissue caused by a complete blockage in one of the arteries that supply blood to the heart (coronary arteries), resulting in an interruption in the blood supply to the heart.
When heart tissue is deprived of blood-borne oxygen for longer than 30 minutes (called ischemia), it begins to die. Ischemia causes electrical instability within the chambers of the heart, preventing the heart from adequately pumping blood throughout the body (called ventricular fibrillation). Permanent brain damage and death can occur when the brain is deprived of blood flow for longer than 5 minutes.
In most cases, blockage occurs as a result of coronary heart disease (CHD), also called atherosclerosis, a condition in which plaques (deposits of cholesterol and fatty material) build up in the arteries and partially or completely block blood flow. When the surface of a plaque tears or ruptures, a blood clot (thrombus) can form and completely block the flow of blood in the artery.
Sudden cardiac arrest (SCA), also called sudden cardiac death, occurs when the heart develops an abnormal rhythm (arrhythmia; e.g., ventricular fibrillation) that causes it to stop beating suddenly. In as many as 95% of cases, a person who experiences an SCA dies, usually within minutes.
Risk factors for sudden cardiac arrest include heart disease, severe physical stress (e.g., extreme blood loss, intense exercise), and genetic (inherited) heart conditions. The condition, which can occur in people who are unaware of an underlying medical condition, is the leading cause for death in young athletes.
SCA requires immediate treatment with a device that delivers and electrical shock to the heart (called a defibrillator). Cardiopulmonary resuscitation (CPR) should be administered until the defibrillator can be used. Automated external defibrillators (AEDs) are available in some public places (e.g., airports, shopping malls, large office buildings).
Incidence and Prevalence
According to the American Heart Association, coronary heart disease (CHD) is the leading cause of death in the United States; and, in adults, heart attacks cause 1 out of every 5 deaths. According to the National Institutes of Health (NIH) more than 1.2 million heart attacks occur each year in the United States and about 460,000 of these are fatal. Approximately 300,000 people die annually from heart attacks before they can receive medical treatment.
According to the World Health Organization (WHO), coronary heart disease accounts for about 17 million (approximately 30%) deaths annually throughout the world. It is estimated that by the year 2010, heart disease will be the leading cause of death in the world.
The primary risk factor for heart attack is coronary heart disease (CHD), also called atherosclerosis. Atherosclerosis is a condition in which plaques (deposits of cholesterol and fatty materials) form in the arteries and partially or completely block blood flow. When a plaque tears or ruptures, a blood clot (thrombus) can form and completely block the flow of blood to the heart. Most heart attacks are caused by a blood clot in a coronary artery.
Many of the risk factors for CHD and subsequent heart attack are related to being overweight. Risk factors include the following:
- Age (over 55)
- Diabetes
- Elevated levels of certain amino acids and proteins (e.g., homocysteine, C-reactive protein, fibrinogen)
- Gender (male)
- Heredity (family history of heart disease)
- High blood pressure (hypertension)
- High fat diet
- High levels of "bad" (LDL) cholesterol and low levels of "good" (HDL) cholesterol
- Lack of exercise
- Smoking
- Stress (e.g., "type A" or driven personality)
In some cases, heart attack is caused by a severe spasm (contraction) in a coronary artery. During a spasm, the artery narrows and blood flow to an area of the heart decreases or stops. The cause of spasms is unknown, and one can occur in normal arteries as well as those partially blocked by atherosclerosis.
The following also may cause heart attack:
- Complications from bypass surgery or cardiac catheterization
- Congenital heart conditions (i.e., conditions present at birth)
- Coronary embolization (blood clot from elsewhere in the body that breaks away and travels to the heart)
- Drug abuse (e.g., cocaine use may impede blood flow in the heart)
- Inflammatory artery disease (indicated by the presence of markers in the blood such as interleukin-18 [IL-18] or C-reactive protein [CRP])
- Trauma (cut, severe blow, or stab wound to the heart)
About one-quarter of all heart attacks occur without producing any identifiable symptoms. These so-called "silent" heart attacks may only be discovered incidentally by examination of an electrocardiogram (EKG) or by other heart test.
A heart attack is a medical emergency and prompt treatment increases the chance for survival. If you suspect that you or someone around you is experiencing a heart attack, seek medical attention immediately.
Symptoms of heart attack vary considerably, even in patients who have experienced a previous heart attack. Heart attack can occur suddenly and cause severe, intense symptoms; however, most begin slowly and cause mild discomfort that may come and go.
In some cases, the condition does not produce symptoms (called "silent heart attack") and is diagnosed incidentally by an electrocardiogram (ECG or EKG). This occurs more often in patients with diabetes.
Warning signs of a heart attack include the following:
- Uncomfortable pressure, fullness, squeezing, or pain in the center of the chest that lasts more than a few minutes or that goes away and comes back
- Pain or discomfort that radiates to other areas of the upper body (e.g., one or both arms, shoulders, back, neck, jaw, or abdomen)
- Shortness of breath (may occur prior to chest pain, may accompany it, or may occur without it)
- Lightheadedness or fainting (may occur with or without chest pain)
- Cold sweat or paleness (may occur with or without chest pain)
- Nausea (may occur with or without chest pain)
Additional symptoms include the following:
- Clamminess
- Indigestion
- Intense sweating
- Unexplained anxiety, weakness, or fatigue
Heart Attack (continued...)
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