Importance of Initiation Pattern of Polymorphic Ventricular Tachycardia in Patients with Implantable Cardioverter Defibrillators

BACKGROUND: Stored intracardiac electrograms (ICEGs) are helpful in understanding the initiation mechanisms of sustained ventricular arrhythmias and in determining the appropriateness of the therapy delivered by implantable cardioverter defibrillators (ICDs). AIM: We investigated the initiation pattern of sustained polymorphic ventricular tachycardia (PVT) and the features of the therapy delivered by ICDs. METHODS: Sixty-six patients (mean age of 67 +/- 8 years) with 97 stored ICEGs showing PVT were evaluated. Cardiovascular diagnosis included coronary artery disease in 72.7% of the patients. The average left ventricular ejection fraction was 33+/-6%. RESULTS: Nonsudden onset episodes were more common than sudden onset episodes (63 episodes, 65% vs 34 episodes, 35%, P < 0.001). More PVT episodes were required multiple shock delivery if they had nonsudden onset initiation (28.6% vs 23.6%, P < 0.01). The mean shock energy delivered for arrhythmia termination was higher in PVT with nonsudden onset (20 +/- 4 vs 14 +/- 5 J, P < 0.01). CONCLUSIONS: The stored ICEGs demonstrate that PVT is most often preceded by ventricular ectopy. To be reverted, nonsudden onset episodes require higher levels of shock energy and more frequently multiple shock achievements than sudden onset episodes.