Rate smoothing induced ventricular arrhythmia and syncope: a new device-induced proarrhythmia.

A 74-year-old male presented to our emergency room with history of sudden onset palpitations associated with syncope. He had a single-chamber implantable cardioverter defibrillator implanted for secondary prevention of sudden cardiac death due to ischaemic cardiomyopathy. Interrogation of the device revealed episodes of non-sustained ventricular tachycardia (NSVT) at 220 ms. Post-tachycardia, another episode of NSVT with longer duration, was induced by rate smoothing pacing algorithm following premature ventricular beats. We describe this unique form of device-related proarrhythmia causing syncope.