Ventricular Fibrillation

Chaotic electrical impulses to the lower chambers of the heart (the ventricles) can cause the ventricles to quiver rather than contracting in a coordinated way. No blood is pumped from the heart, causing a form of cardiac arrest that is fatal unless treated immediately.



Ventricular fibrillation causes a loss of consciousness in seconds. Without treatment, the brain doesn't get enough oxygen. A person will typically develop seizures and irreversible brain damage after approximately five minutes. Death soon follows.


Causes and Risk Factors

The most common cause of ventricular fibrillation is a lack of blood flow to the heart muscle due to coronary artery disease, such as occurs during a heart attack. Other causes include:

  • Drowning
  • Drugs that affect electrical currents in the heart (such as sodium or potassium channel blockers)
  • Electrical shock
  • Very low blood pressure, which can result from coronary artery disease and other disorders
  • Very low levels of potassium in the blood (hypokalemia)


Signs of cardiac arrest include:

  • Loss of detectable pulse, heartbeat or blood pressure
  • Skin that turns a deadly white
  • Sudden collapse
  • Very dilated pupils

An electrocardiogram is used to diagnose the cause of the cardiac arrest as ventricular fibrillation.



Ventricular fibrillation is an extreme medical emergency. Cardiopulmonary resuscitation (CPR) must be started as soon as possible — within a few minutes. As soon as possible, defibrillation (an electrical shock to the chest) should be administered. Antiarrhythmic drugs may then be given to help maintain a normal heart rhythm.

An electrical shock to the heart can restore normal heart rhythms if the ventricular fibrillation occurs within hours of a heart attack in people who are not in shock and do not have heart failure. If shock and heart failure are present, it is likely that there is major damage to the ventricles. Defibrillation is not as successful in these cases.

Once a person has been brought back from ventricular fibrillation, he/she at high risk of having another episode. Treatment includes treating an underlying disorder if it is reversible and a cause of the ventricular fibrillation. Drugs may also be given to prevent reoccurrences.

Surgery to implant a defibrillator in the chest can also be performed. The defibrillator identifies abnormal heart rhythms and sends an electric shock to the heart to correct the problem.

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