992-112 Compromised Time to Shock Therapy in a Noncommitted Transvenous ICD System

Abstract

Reduction in electrogram size after an endocardial shock has been associated with sensing problems in some transvenous integrated bipolar shock/sense lead systems. We have previously reported that redetection time (RDT) after a failed defibrillation shock is not prolonged in the 60 series Endotak lead (CPI, St Paul, MN) combined with the Ventak P (committed shock) pulse generator. We performed this study to examine RDT in the non-committed Ventak P2 using the same lead system. In 25 patients (20 male, 15 with coronary disease) undergoing follow-up testing, 84 episodes of failed defibrillation shock were examined for initial detection time (lDT) and RDT as well as failed arrhythmia reconfirmation during capacitor charge (FTR). Event marker output and telemetered data were used to analyze each ventricular fibrillation episode for detection duration excluding the programmed delay and charge time. Mean ( ± SEM) age was 61 ± 3 and ejection fraction was 31 ± 2%. In seconds (s), lDT was 2.83 ± 0.14 and RDT was 4.01 ± 0.31 (p < 0.0001). There were 7 lDT and 18 RDT events ≥ 5s (p = 0.03) and no lDT and 4 RDT events ≥10s. There were 5 FTR events prior to failed shocks, and 19 after such shocks (p = 0.004). Mean energy of failed shocks was 10.8 ± 0.9J. Sensing of VF after a failed shock is significantly prolonged in this ICD system; our data suggest that the requirement for reconfirmation may delay therapy delivery after an initial shock that fails to defibrillate.