Ventricular fibrillation

Synonyms: V-fib

Medical Specialties: Cardiology, Emergency medicine, Internal medicine

Clinical Definition

Ventricular fibrillation is a life-threatening cardiac arrhythmia, marked by rapid, unsynchronized depolarization of the ventricles. Contractions are uncoordinated and ineffective at maintaining proper circulation and blood pressure. Ventricular fibrillation leads to cardiac arrest if not treated immediately.  

In Our Own Words

Ventricular fibrillation is an abnormal heart rhythm, which can be fatal if not reversed quickly. When ventricular fibrillation occurs the lower chambers of the heart called ventricles don’t beat properly. Instead of beating normally, the ventricles quiver or flutter.


Due to the abnormal rhythm, the heart is not able to pump blood to organs throughout the body, such as the brain. Ventricular fibrillation usually causes collapse quickly and can lead to sudden cardiac death if treatment to restore an effective rhythm is not administered.

Relevant Conditions
Side Effects
  • Loss of consciousness
  • No pulse
  • Seizures
Share this article
  • American Heart Association. Ventricular Fibrillation. Accessed October 2013.
  • NYU Langone Medical Center. Ventricular Fibrillation. Accessed October 2013.
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