An ICD is a bit more drastic than a pacemaker. They do have a pacemaker-like mode, called overpacing that tries to slow down tachycardia, but their main functi

An ICD is a bit more drastic than a pacemaker. They do have a pacemaker-like mode, called overpacing that tries to slow down tachycardia, but their main function is delivering shocks to reset life-threatening arrythmias or to defibrillate in the case of ventricular or atrial fibrilation. ICDs are also much larger than pacemakers, as they have to have much larger batteries and capacitors.