Ventricular Fibrillation

Updated:Nov 17,2014

arrhythmiaVentricular fibrillation is life-threatening
Ventricular fibrillation (v-fib for short) is the most serious cardiac rhythm disturbance. The lower chambers quiver and the heart can't pump any blood, causing cardiac arrest.

How it works
The heart's electrical activity becomes disordered. When this happens, the heart's lower (pumping) chambers contract in a rapid, unsynchronized way. (The ventricles "fibrillate" rather than beat.) The heart pumps little or no blood. Collapse and sudden cardiac arrest follows -- this is a medical emergency! Watch an animation of v-fib.

Signs of cardiac arrest
  • Sudden loss of responsiveness (no response to tapping on shoulders)
  • No normal breathing (the victim is not breathing or is only gasping)
  • This is sudden cardiac arrest (SCA) -- which requires immediate medical help (CPR and defibrillation)!
Treatment for cardiac arrest caused by ventricular fibrillation
Ventricular fibrillation can be stopped with a defibrillator, which gives an electrical shock to the heart. If you see someone experiencing the signs of cardiac arrest:
  • Yell for help.Tell someone to call 9-1-1 and get an automated external defibrillator (AED) if one is available. You begin CPR immediately.
  • If you are alone with an adult who has these signs of cardiac arrest, call 9-1-1 and get an AED (if one is available) before you begin CPR.
  • When doing CPR, push down on the chest at least 2 inches at a rate of at least 100 compressions a minute. After each compression, let the chest come back up to its normal position.
  • Use an AED as soon as it arrives.
  • Continue CPR until the person starts to respond or trained emergency medical help arrives and takes over.
  • While Hands-Only™ CPR (giving chest compressions alone) may be effective for teens or adults who suddenly collapse, the AHA recommends CPR with a combination of compressions and breaths (given as sets of 30 compressions and 2 breaths) for: all infants, children up to puberty, anyone found already unconscious and not breathing normally, and any victim of drowning, drug overdose, collapse due to breathing problems, or prolonged cardiac arrest.
Learn more about defibrillation

Reducing risk of ventricular fibrillation This content was last reviewed on 10/23/2014.