Arrhythmia Diagnosis Following an ICD Shock.

Abstract

Stored electrograms show atrial fibrillation with rapid ventricular rates (top panel). Sufficient numbers of RR intervals meet the tachycardia detection criteria initiating a train of anti-tachycardia pacing by the ICD (after the 8th electrogram in the second panel). This provokes rapid monomorphic ventricular tachycardia (note that the electrogram morphology is different from that during atrial fibrillation) which enters the fibrillation detection zone leading to an ICD shock (after the 3rd electrogram in the 4th panel). Sinus rhythm is restored. Note the 5th and 11th electrograms in the 4th panel have different morphology from sinus rhythm electrogram following shock indicating PVCs. There is no evidence for ICD malfunction. Induction of ventricular tachycardia by attempted anti-tachycardia pacing is a pro-arrhythmic effect of ICD therapy.

Keywords

• implantable defibrillator
• proarrhythmic effect