Ventricular Fibrillation

Ventricular fibrillation, or V-fib, is considered the most serious cardiac rhythm disturbance.

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

This type of arrhythmia is a medical emergency. It’s life-threatening.


Watch an animation of ventricular fibrillation.

Causes of ventricular fibrillation

V-fib can have several root causes, including:

  • Insufficient blood flow to the heart muscle
  • Damage to the heart muscle (from a heart attack, for example)
  • Cardiomyopathy
  • Problems with the aorta
  • Drug toxicity
  • Sepsis (severe body infection)

Signs of cardiac arrest

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

  • Loss of responsiveness (no response to tapping on the shoulders)
  • No normal breathing (the victim is not breathing or is only gasping)

If you suspect someone is suffering from 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 and its serious consequences, your doctor may recommend: