If ventricular tachycardia occurs in an Implantable Cardioverter Defibrillator (ICD) wearer, the ICD can combat this with 2 different forms of therapy, provided these are activated (which can be done using a programming device). First, the ICD attempts to override the tachycardia. The fastest pacemaker gets control of the heart. If this is not successful, the defibrillator function is used. Here you can see the limb leads. Initially there is a relatively slow ventricular tachycardia with a heart rate of approx. 125 bpm. The ICD then starts with the antitachycardia pacing (ATP) over 16 beats, easily recognizable by the pacemaker spikes. At the end, however, there is still ventricular tachycardia (initially with a still low rate), so this overstimulation was not successful.