Sudden Cardiac Arrest Common, Misunderstood

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The death of Brittany Murphy of apparent sudden cardiac arrest highlights this leading and common cause of death in the United States. An estimated 400,000 Americans die of sudden cardiac arrest each year, yet many people do not know what this condition is.

Sudden cardiac arrest is not a heart attack (i.e., a myocardial infarction). In people who suffer sudden cardiac arrest, the heart abruptly and unexpectedly stops functioning, also known as cardiac arrest. This is caused by a malfunction in the electrical circuitry of the heart, a rhythm disorder known as ventricular fibrillation (VF). In a heart attack, a blockage in a blood vessel interrupts the flow of blood to the heart, causing an infarct. It is possible, however, for someone to suffer both sudden cardiac arrest and a heart attack.

Ventricular fibrillation occurs when the electrical signals that regulate the contractions in the ventricles become erratic, which prevents them from pumping blood from the heart to the body. If the individual who is experiencing sudden cardiac arrest does not get immediate medical help, he or she will die within minutes.
The life-saving device for victims of sudden cardiac arrest is a defibrillator. This device delivers an electric shock to the heart, restoring its normal rhythm. This shock must be administered within minutes of the arrest, however, to prevent death.

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Anyone who knows they are at high risk for sudden cardiac arrest may have an implantable cardioverter defibrillator, a device that monitors the heart’s rhythm and automatically sends a brief, high-energy shock to the heart when the individual develops an irregular heart rhythm that may result in sudden cardiac death.

Causes of Sudden Cardiac Arrest
In people who have a normal, healthy heart, causes of sudden cardiac arrest can include an electrical shock, trauma to the chest, or use of illegal drugs. In most cases, however, the event occurs in a person who has a pre-existing heart condition, even if he or she is not aware of the condition. These include:

  • Coronary artery disease. More than 80 percent of people who suffer sudden cardiac arrest have coronary artery disease.
  • Heart attack: If an individual has a heart attack that is the result of severe coronary artery disease, it may trigger ventricular fibrillation and sudden cardiac arrest.
  • Congenital heart disease. When sudden cardiac arrest occurs in young people (age 35 and younger), it is often due to congenital heart disease. Among young athletes, a genetic disorder called hypertrophic cardiomyopathy is the most common cause of sudden cardiac arrest. It is believed to be brought on by vigorous exercise.
  • Enlarged heart. In these cases, the heart’s muscle is abnormal, which can lead to tissue damage and arrhythmias.
  • Valvular heart disease. If there are leaky or narrow heart valves, they can cause the heart muscle to stretch or thicken. These events can increase the risk of arrhythmias.
  • Electrophysiological abnormalities. Some people have a malfunction in their heart’s electrical system. Examples of these primary heart rhythm problems include primary ventricular fibrillation, long QT syndrome, and Wolff-Parkinson-White syndrome.

Symptoms of Sudden Cardiac Arrest
Unfortunately, symptoms of sudden cardiac arrest are usually sudden and drastic: sudden collapse, no breathing, no pulse, and loss of consciousness. Sometimes other signs and symptoms may precede the actual event, including fatigue, fainting, blackouts, dizziness, chest pain, palpitations, or vomiting. In most cases, however, sudden cardiac arrest occurs without warning.

Sudden cardiac arrest is an all-too-common event. Although it most often affects people age 40 and older, about 10 percent of cases occur in younger people. Brittany Murphy may have been a victim in this latter category. Even among people who receive emergency treatment, the survival rate ranges from about 3 to 16 percent, according to a recent study in the Journal of the American Medical Association.

SOURCES:
Heart Rhythm Foundation
Mayo Clinic
Nichol G et al. JAMA 2008 Sep 24; 300(12): 1423
Sudden Cardiac Arrest Foundation

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