treatment for life-threatening cardiac dysrhythmias

Defibrillation is taking the heart out of fibrillation, often saving a persons life. Fibrillation is when the heart is not pushing blood well, because the heart muscle is not working in any pattern. The de- prefix in the name means "undo".

Automated External Defibrillator (AED), with paddles

Electrical chemical charge causes a muscle to contract. This is how nerves cause muscles to work, using chemicals like it is the power (in normal function). The heart is a large muscle, and certain parts need to contract before other parts in a regular pattern. This lets it push blood through the heart and out to the rest of body correctly. Sometimes the heart muscle doesn't contract in the correct way, or at the correct speed, and this is called an arrhythmia (out of rhythm). Fibrillation is a type of arrhythmia when the whole heart is quivering, not organized to make heart beats of any kind.[1] Cardio Pulmonary Resuscitation (CPR) can get blood to the body when the heart is fibrillating, but the heart still needs to be restarted. Sometimes CPR will do that as well, but often a defibrillator is needed. Defibrillation is done with a defibrillator.

Defibrillation works by sending a strong electric current to the heart, which resets the heart, and hopefully returns it to a normal, coordinated rhythm. It needs to depolarise (take away the existing electric charge) from a large part of the heart muscle, which stops the arrhythmia and allows the normal heartbeat to return. Defibrillators can work from outside the body with the use of an external defibrillator or an automated external defibrillator, or inside the body with an implantable defibrillator.



The first use of the technique on a human was in 1947 by Claude Beck, a professor of surgery at Case Western Reserve University. The patient was a 14-year-old boy named Mickey.[2]

Defibrillation is now used during open heart surgery, when the heart is stopped on purpose. In 1980 the first implanted defibrillator was put into a patient. Implanted defibrillators are put into the chests of people at risk of going into fibrillation[3] commonly nowadays.



Not all arrhythmias need defibrillation. Some arrhythmias still push blood to the body, not well, but still enough to keep a person alive. Other types, like ventricular fibrillation or pulseless ventricular tachycardia, will cause a person to die within minutes unless treated. These are what need to be treated by defibrillation.

Fibrillation is when the heart muscle is contracting, but not in any organized way, and blood is not pumped. Pulseless tachycardia is when the heart is beating too fast to collect any blood to push.

Asystole is when the heart is not working at all (flat-line). Defibrillation does not work on asystole, but CPR might help.

Success rate


Defibrillation is most successful when done right when the problem starts. Success in the first minute is about 90% and drops by 10% every minute after that. This time can be made longer by giving the person CPR, but having a defibrillator close by is very important.[4]



  1. "Ventricular Fibrillation". Retrieved 21 February 2014.
  2. "Claude Beck, defibrillation and CPR". Case Western Reserve University. Archived from the original on 2007-10-24. Retrieved 2007-06-15.
  3. Matchett, M.; Sears, S. F.; Hazelton, G.; Kirian, K.; Wilson, E.; Nekkanti, R. (2009). "Implantable cardioverter defibrillator". Expert Review of Medical Devices. 6 (1). Nat'l Inst. of Health: 43–50. doi:10.1586/17434440.6.1.43. PMID 19105779. S2CID 23062309. Retrieved 22 February 2014.
  4. "Defibrillation and Cardiac Arrest" (PDF). PrenHall. Retrieved 21 February 2014.

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