An ICD is similar to a pacemaker and has the same basic functions. However, this device is able to detect abnormal and dangerous heart rhythms. Once these heart rhythms have been detected the device will be able to stop them by either pacing the heart rapidly for a short period or alternatively if this is not successful then it will deliver a high energy shock to reset the heart.
Like a pacemaker, these devices can have their settings changed by communication with the pacing programmer. An ICD is implanted in the same manner as a pacemaker, using local anaesthetic and some sedation. In some cases the shock function will also be tested while the patient is sedated.