Impact of Defibrillation Test Protocol and Test Repetition on the Probability of Meeting Implant Criteria

BACKGROUND: Defibrillation testing is a common procedure at defibrillator implant, with the purpose to ensure that each patient receives a device-lead system with a sufficient shock efficacy. The objective of this paper was to study the influence of defibrillation test protocols on the probability of passing implant testing. METHODS: Defibrillation shock efficacy as a function of shock energy was modeled by a dose-response relationship estimated from the clinical data of the PainFREE Rx II study on 564 patients. A Monte Carlo method was used to simulate the outcomes of 12 commonly used defibrillation efficacy test protocols: four safety margin tests and eight protocols estimating the defibrillation threshold (DFT). RESULTS: The probabilities of failing 20-J and 25-J implant criteria for the different protocols ranged from 0.9% to 6.3% for 20 J and 0.3% to 3.4% for 25 J. Large variations in consecutively measured DFT values in the same patients were observed. Best results in the identification of “high risk” patients were obtained with the 2/2 safety margin protocol with an implant criterion of 20 J. The study also showed that the probability of patients inappropriately passing the implant criterion increased when the defibrillation test was repeated after initial failure. CONCLUSION: The defibrillation test protocol greatly influences the probability of meeting implant criterion. Therefore, these test protocols should be standardized. The model developed in this study, could be used to further understand their impact and to derive recommendations.