Abstract 278: Successful Conversion of Ventricular Tachyarrhythmias by Wearable Defibrillator

Abstract

Ventricular fibrillation (VF) and ventricular tachycardia (VT) are lethal cardiac dysrhythmias which must be treated within minutes of onset to avoid death. Certain patients who are high risk for VF/VT are not eligible or appropriate in the short term for an implantable cardiac defibrillator (ICD). The wearable cardioverter defibrillator (WCD) is a bridge device for use during this waiting period. This study tested the hypothesis that the WCD would successfully convert VF/VT to a perfusing rhythm in all patients. In addition, we determined the incidence of shocks delivered to patients using the WCD and classified shocks as appropriate or inappropriate. Methods: We retrospectively reviewed data of all patients prescribed a WCD between January 1, 2007 and December 31, 2009 whose end of use date occurred on or prior to March 31, 2010 in the ZOLL LifeVest post-market registry. This included ECG recordings and customer call reports related to all shock events and deaths that occurred during WCD use. A single event was defined to include all episodes of VF/VT within a 24 hour period. Data were analyzed using summary statistics. Results: The registry included 15,193 persons with mean age 59.8 +/- 14.5 years (SD); 71.5% were male. Total exposure to WCD was 2,378 person-years in 14,475 persons with a mean duration of WCD use per person of 59.9 +/- 59.1 days. The most common indications were non-ischemic cardiomyopathy (40.1%), myocardial infarction (33.0%), and ICD pocket infection (12.1%). There were 203 VF/VT events and 378 individual episodes of VF/VT (0.16 episodes/person-year of WD use) in 185 persons (1.3% of WD users). Shock led to organized rhythm in 345 (91.3%) of VF/VT episodes and persistent VF/VT in 26 (6.9%). Event survival was 91.6%. None of the 223 inappropriate shocks delivered to 213 persons resulted in death. Conclusion: The WCD was highly effective for prevention of sudden death in persons at high risk of VF/VT but not yet eligible for an ICD, with no mortality from inappropriate shocks.