The implantable cardioverter ??? defibrillator (ICD) is a device that treats ventricular tachyarrhythmias (VT), when they appear in a sustained form. The device???s programming can deliver the following therapies: 1) antitachycardia pacing (ATP), 2) cardioversion and 3) defibrillation. Today???s devices also have the capability of every mode of cardiac pacing, i.e. atrial, ventricular, atrio-ventricular and biventricular pacing.It is well known that the antiarrhythmic drug therapy can exhibit proarrhythmic effects. Likewise, the antiarrhythmic apparatus can possibly aggravate an existing VT or cause the appearance of a new arrhythmia, attempting to convert the clinical tachyarrhythmia. A case of proarrhythmic effect related to the therapeutic sequences delivered by an ICD, is delineated in the following continuous recording of an arrhythmic event,as it was stored in the Holter function of the device
