Ventricular Fibrillation

Ventricular fibrillation, or VF, is considered the most serious abnormal heart rhythm. VF is extremely dangerous and can lead to sudden cardiac death. Without treatment, the condition is fatal within minutes.

Disordered electrical activity causes the heart’s lower chambers (ventricles) to quiver instead of contracting (or beating) normally. This prohibits the heart from pumping blood, causing collapse and cardiac arrest


Watch an animation of ventricular fibrillation.

Causes of ventricular fibrillation

VF can have several causes, including:

  • Insufficient blood flow to the heart muscle
  • Damage to the heart muscle (from a heart attack, for example)
  • Cardiomyopathy (a disease of the heart muscle)
  • Problems with the aorta
  • Drug toxicity
  • Sepsis (severe body infection)
  • Electrocution accidents or injury to the heart
  • Heart attack or angina
  • Congenital heart disease
  • Heart surgery
  • Sudden cardiac death from a sudden blow to the area directly over the heart
  • Very high or very low potassium levels in the blood

Signs of cardiac arrest

Ventricular fibrillation can cause sudden cardiac arrest, which requires immediate medical attention. Signs of cardiac arrest include:

  • Loss of consciousness
  • Not breathing or only gasping for breath
  • Sudden collapse
  • No pulse

If you suspect someone is having cardiac arrest, it’s vital to respond appropriately and quickly. Call 911, give CPR and use an automated external defibrillator (AED) (PDF) if one is available.

Reducing your risk

If you’re at risk for ventricular fibrillation, your health care professional may recommend: