Defibrillators continuously monitor the heart rhythm in order to detect overly rapid arrhythmias such as
- Ventricular tachycardia (rapid regular beating of the ventricles, the bottom chambers of the heart); and
- Ventricular fibrillation (rapid irregular beating of the ventricles).
These ventricular arrhythmias impair the pumping efficiency of the heart and greatly raise the risks of fainting (syncope) and sudden cardiac arrest. They tend to develop in people with coronary artery disease and heart muscle diseases (cardiomyopathies). They are life- threatening.
A defibrillator can be implanted within the body by far less invasive techniques than in the past because the devices, aside from being more technologically advanced, are smaller. (An implantable defibrillator is about the size of a minicassette).
The defibrillator corrects the heart rhythm by delivering precisely calibrated and timed electrical shocks, when needed, to restore a normal heartbeat.