A Case Report Demonstrating Spontaneous Change in Tachycardia Terminating Window

A patient who received a patient-activated pacemaker system for termination of paroxysmal, drug-resistant, ventricular tachycardia is described. During the pre-implant invasive electrophysiological (EP) study and the three post-implant non-invasive EP studies, tachycardias were easily and reproducibly terminated by two stimuli using the interval scanning mode. On the fourth day post-implant, this pacing mode no longer terminated tachycardia at rest. A new pacing mode using more stimuli was then found to terminate the tachycardia reproducibly under various physiological conditions. This case report demonstrated a spontaneous change in the tachycardia terminating window and the usefulness of versatility in antitachycardia pacemaker systems.