Abstract 2492: Cardioverter-Defibrillator Implantation Without Defibrillation Threshold Testing: Efficacy of Therapy and Long-Term Outcome
Background: Ventricular fibrillation (VF) is routinely induced during implantable-cardioverter defibrillator (ICD) insertion to determine defibrillation threshold (DFT) and to test ICD performance. This strategy has been questioned due to complications associated to VF induction and low incidence of spontaneous VF. We aimed to analyze efficacy of ICD therapies and long-term outcome in a cohort of consecutive patients (pts) that underwent ICD implantation without VF induction.
Methods: All consecutive patients undergoing initial ICD placement or generator replacement between May 2005 and May 2008 at our institution were followed. DFT testing was left at the discretion of the operator, but a policy of no-DFT testing was recommended. We registered:
parameters of pacing, detection and painless impedance, both at implantation and during follow-up;
spontaneous arrhythmias occurrence during follow-up and therapy efficacy; and
Results: A total of 348 pts received a high-output ICD (≥35 J): age 66±14, 82% male, 60% ischemic cardiomyopathy, 67% LVEF<35%. ICD implantation indication was primary prevention in 45% pts and 37% were generator replacements. Due to clinical reasons or physician preference, 29 (8%) pts underwent DFT testing at implant, and were excluded from analysis. Four pts were lost to follow-up. After 20±13 months of follow-up, 71 (22%) pts presented 419 ventricular events that required ICD intervention (29 pts ATP-only and 42 pts ATP and/or shocks). No significant sensing problems were detected during the VT/VF episodes. All VT/VF episodes requiring shocks (programmed at highest output) were successfully terminated by the first shock, except for 3 episodes in 3 p in whom the second shock terminated the arrhythmia. At the last device interrogation, all pacing and shock impedances were normal, except for 1 p with high pacing impedance due to electrode fracture. There were 17 deaths due to heart failure (7), in-hospital electrical storm (ICD working properly) (1), non-sudden out-of-hospital death (3) and non-cardiac death (6).
Conclusions: ICD implantation without DFT testing resulted in a 100% efficacy of VT/VF conversion and no ICD-related mortality. These results should be confirmed by randomized clinical trials.