Ventricular fibrillation is a heart rhythm disorder that occurs when the heart beats with fast and irregular electrical impulses. Fibrillation is an uncontrolled twitching of muscle fibers (fibrils) and when it occurs in the lower chambers of the heart, it is called ventricular fibrillation.

Ventricular fibrillation occurs when the heartbeat is interrupted, such as during a heart attack. This in turn causes blood pressure levels to fall, cutting off blood supply to vital organs. 

This condition requires immediate medical attention, as it can lead to sudden cardiac death. Treatment options generally include certain medications, cardiopulmonary resuscitation (CPR) and defibrillation to restore normal heart rhythm.



Loss of consciousness (fainting) is the most common sign of ventricular fibrillation. Other signs and symptoms of ventricular fibrillation include:

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



The heart pumps blood to the lungs, brain and other organs. When it beats, electrical impulses follow a pathway through the heart. In instances where these electrical impulses become interrupted, ventricular fibrillation occurs and blood is not pumped from the heart.

The most common causes of ventricular fibrillation are a heart attack, where the heart muscle does not receive enough oxygen and the formation of scar tissue in the heart’s muscle from a prior heart attack.

Another cause may be ventricular tachycardia. Most ventricular tachycardia last less than 30 seconds and may not cause symptoms, however in more severe cases where VT lasts for more than 30 seconds, it can lead to heart palpitations, dizziness or fainting.

Other conditions that can lead to ventricular fibrillation include:

  • Heart disease present at birth
  • Heart muscle disease
  • Heart surgery
  • Narrowed coronary arteries
  • Certain medications


Risk factors 

Factors that can  increase the risk of ventricular fibrillation include:

  • A previous occurrence of ventricular fibrillation
  • A prior heart attack
  • Congenital heart disease
  • Heart muscle disease
  • Injuries that cause damage to the heart muscle
  • Use of illegal drugs
  • Electrolyte abnormalities