Ventricular Fibrillation: The Heart Rhythm That Kills in Minutes
Ventricular fibrillation causes the heart's ventricles to quiver instead of pumping, producing zero cardiac output — fatal within minutes without defibrillation.
Ventricular fibrillation (VF or V-fib) is a cardiac arrhythmia in which the heart's ventricles produce rapid, chaotic electrical signals, causing them to quiver instead of contracting in coordinated pumps. Cardiac output drops to zero — the heart moves but doesn't pump blood. Without intervention, VF is fatal within minutes. It is the leading cause of sudden cardiac death and the primary arrhythmia targeted by automated external defibrillators (AEDs). The treatment is defibrillation — delivering an electrical shock that resets the heart's electrical activity, allowing normal rhythm to resume. Importantly, a defibrillator does not "restart" a stopped heart. It stops the chaotic rhythm of VF (or ventricular tachycardia), giving the heart's natural pacemaker cells a chance to re-establish coordinated beating. A heart in asystole (complete electrical silence — "flatline") cannot be defibrillated and has a far worse prognosis. **See also:** Why Defibrillators Can't Restart a Stopped Heart