Runaway Pacemaker in an Implantable Cardioverter Defibrillator

Runaway Pacemaker in an ICD. Introduction : Runaway pacemaker is a potentially catastrophic complication of any permanent pacing system. Methods and Results : A 70‐year‐old man was found to have erratic behavior of his implantable cardioverter defibrillator (ICD) during a routine outpatient interrogation. His device was turned off, and he was hospitalized in preparation for a pulse generator replacement. During his hospitalization, his ICD unexpectedly began pacing rapidly. Despite prompt resuscitation attempts, the patient died. Postmortem examination of the device demonstrated a crystal oscillator failure. Conclusion : A previously unrecognized component malfunction is a potentially lethal complication of ICDs.