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Ventricular Fibrillation (VF) is a severely abnormal heart rhythm that is life threatening.


The heart pumps blood to the lungs, brain and other organs. An interrupted heartbeat, even for a few seconds, can lead to fainting or cardiac arrest.

Fibrillation is an uncontrolled twitching or quivering of muscle fibers. When it occurs in the lower chambers of the heart, it is called VF. During VF, blood is not pumped from the heart and sudden cardiac death can result.

The most common cause of VF is a heart attack. However, VF can occur whenever the heart muscle does not get enough oxygen for any reason. Conditions that can lead to VF include:

  • Electrocution accidents or injury to the heart
  • Heart attack or angina
  • Heart disease that is present at birth
  • Heart muscle disease in which the heart muscle becomes weakened and stretched or thickened
  • Heart surgery
  • Sudden cardiac death; most often occurs in athletes who have had a sudden blow to the area directly over the heart
  • Medicines
  • Very high or very low potassium levels in the blood

Most people with VF have no history of heart disease. However, they often have heart disease risk factors, such as smoking, high blood pressure and diabetes.


A person who has a VF episode can suddenly collapse or become unconscious. This happens because the brain and muscles are not receiving blood from the heart.

The following symptoms may occur within minutes to one hour before the collapse:

  • Chest pain
  • Dizziness
  • Nausea
  • Rapid or irregular heartbeat
  • Shortness of breath

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