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Proarrhythmic potential and synchronization of shock delivery has been studied in patients with inducible ventricular tachycardia (VT) with a reported proarrhythmic rate of 6-31%. We sought to characterize the outcomes and synchronization of shock delivery for spontaneous tachyarrhythmias with implantable cardioverter-defibrillators (ICD).
Medical and device records were reviewed for ICD shocks from 2004-2012 at a tertiary-care hospital. Polymorphic VT, ventricular fibrillation (VF), noise or over-sensing events were excluded. 136 shock episodes were included. Arrhythmias were classified as VT, supraventricular tachycardia (SVT), or atrial fibrillation/flutter (AF). Shock delivery was considered synchronized if delivered within 30 msec of initial ventricular depolarization. Outcomes were categorized as proarrhythmic, ineffective or successful. Ejection fraction (EF), etiology of cardiomyopathy, and arrhythmia cycle length (CL) were recorded.
The mean age was 55 years +/- 15.5, 70% were male, mean EF was 28%, 48% had ischemic cardiomyopathy and 73% had ICDs placed for primary prevention. Of all arrhythmias, VT, AF, SVT comprised 71%, 5%, 24%, respectively, and 61% had CL > 270 msec. Arrhythmias occurred more often in non-ischemic cardiomyopathy (59.9%, p<0.03) and if EF ≤ 35% (71.3%, p < 0.001). All shocks were delivered synchronously. Outcomes were as follows: 4% were proarrhythmic, 67% were successful, and 29% were ineffective. The mean energy delivered was 32.6 +/- 8.0 J. Proarrhythmic shocks were not significantly greater for CL ≤ 270 msec (5.6% vs. 2.5 %, p=0.34), VT vs. AF (4.1% vs. 14.2%, p=0.22), VT vs. SVT (4.1% vs. 0%, p=0.24), or for patients with ischemic cardiomyopathy (5.5% vs. 2.5%, p=0.36), but there was a trend towards greater frequency when EF ≤ 35% (5.2% vs. 0%, p=0.15).
Prevalence of proarrhythmic ICD shocks for spontaneous tachyarrhythmias is lower than that for induced VT. CL, type of arrhythmia, and patient features are not significantly associated with proarrhythmic shocks. Despite 100% shock synchronization, 4% of shocks were proarrhythmic suggesting proarrhythmia is not a function of synchronous shock delivery.
Poster Sessions, Expo North
Saturday, March 09, 2013, 3:45 p.m.-4:30 p.m.
Session Title: Arrhythmias: Devices I – Identification and Avoidance of Complications Associated with Implantable Devices
Abstract Category: 8. Arrhythmias: Devices
Presentation Number: 1149-35
- 2013 American College of Cardiology Foundation