There are many causes of abnormal heart rhythms (arrhythmias). Some arrhythmias are harmless and do not need treatment. Sometimes arrhythmias stop on their own or with changes in lifestyle, such as avoiding alcohol, caffeine (in beverages and foods), and smoking. Other arrhythmias are dangerous or bothersome enough to need treatment. Cardioversion-defibrillation is one type of treatment. Other treatments for arrhythmias include insertion of a pacemaker or an implantable cardioverter-defibrillator (ICD), use of antiarrhythmic medications, or destruction of a small area of heart tissue that is responsible for the arrhythmia (ablation).
Cardioversion-defibrillation involves giving an electrical shock to the heart. Sometimes this shock can stop a fast arrhythmia and restore normal rhythm. The shock briefly stops the heart from beating and, after a second or 2, it starts beating again on its own. Often, it starts back in a normal rhythm but sometimes the arrhythmia starts again. However, electrical shocks cannot restart a heart that has no electrical activity at all (asystole).
Giving the heart such an electrical shock is called cardioversion, or defibrillation, depending on the type of abnormal rhythm for which it is used.
Cardioversion is giving an electrical shock timed (synchronized) to a specific part of the heart beat. It may be used for arrhythmias starting in the atria (such as atrial fibrillation) or the ventricles (such as ventricular tachycardia) as long as there is some type of organized electrical activity in the heart.
Defibrillation is giving an electrical shock during ventricular fibrillation. During ventricular fibrillation, there is no organized electrical activity in the heart to which the shock can be timed.
The machine that delivers the shock is called a defibrillator, even though it is used for both defibrillation and cardioversion. Defibrillators can be used by a team of doctors and nurses, by paramedics, or by firefighters.
An automated external defibrillator (AED) can automatically detect the presence of an arrhythmia, determine if a shock is advisable, and deliver the proper strength shock. Thus, using an AED requires only minimal training, such as that provided in a first-aid course, and sometimes can be done without any training. AEDs are present in many public places, such as airports, sports arenas, hotels, and shopping malls.
