Why is it done?
Implantation of the ICD is done in patients who suffer from very fast arrhythmias. These rhythm disorders are often associated with dizziness, or fainting and can be life-threatening. ICD can diagnose these rhythm disorders by a very sophisticated arrhythmia detection algorithm, and then deliver appropriate therapy.

If the arrhythmia is less dangerous, initially ICD tries to terminate it by overdrive pacing. If this is not effective, or if the arrhythmia is very dangerous in nature, a DC shock with appropriate energy is delivered which normalizes the heart rhythm in virtually all cases.