Ventricular fibrillation manifests itself by a fast and disorganized electrical activation of the ventricles, with the immediate consequence of the loss of any effective cardiac contraction. Failure to intervene within 5 minutes can be fatal (sudden death) or lead to irreversible brain damage. The only treatment is an electric shock delivered by a defibrillator.
Ventricular fibrillation is associated with pre-existing heart disease (infarction, cardiomyopathy) but can occur in a healthy heart.