Reduction in defibrillation threshold by modifications to the subcutaneous implantable-cardioverter defibrillator coil

Abstract

The subcutaneous implantable cardioverter defibrillator (S-ICD) is approved as an alternative to the traditional transvenous ICD (T-ICD). The S-ICD has higher average defibrillation threshold (DFT) than the T-ICD, related primarily to greater distance from shocking coil to ventricular myocardium with the S-ICD. The S-ICD therefore utilizes a larger device capable of generating an 80J shock, compared to 35-40J maximal shock output typical for T-ICDs, and defibrillation efficacy testing is generally recommended for the S-ICD 1 Wilkoff B, Fauchier L, Stiles M, et al. 2015 HRS/EHRA/APHRS/SOLAECE expert consensus statement on optimal implantable cardioverter-defibrillator programming and testing. Heart Rhythm 2016;13;e50-86. Google Scholar . We previously published computer modeling of predictors of defibrillation efficacy with the S-ICD, which determined that minimal fat underlying the S-ICD coil and generator (reducing shock impedance), and posterior generator position (better directing the shock vector across the ventricles), are predictors of lower DFT 2 Heist E. Belalcazar A. Stahl W. et al. Determinants of Subcutaneous Implantable Cardioverter-Defibrillator Efficacy. J Am Coll Cardiol EP. 2017; 3: 405-414 Google Scholar . Those findings formed the basis for the PRAETORIAN score, which is utilized in clinical S-ICD implantation to reduce DFT 3 Quast A.-F.B.E. Baalman S.W.E. Brouwer T.F. et al. A novel tool to evaluate the implant position and predict defibrillation success of the subcutaneous implantable cardioverter-defibrillator: The PRAETORIAN score. Heart Rhythm. 2018; 16: 403-410 Abstract Full Text Full Text PDF PubMed Scopus (65) Google Scholar . A previously published computer modeling study examined the impact of dual S-ICD electrodes and electrode arrays, as well as variations in generator and lead location; results demonstrated reduced DFT with some configurations compared to the standard S-ICD 4 Jolley M. Stinstra J. Tate J. et al. Finite Element Modeling of Subcutaneous Implantable Defibrillator Electrodes in an Adult Torso. Heart Rhythm. 2010; 7: 692-698 Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar . In this current study, we performed computer modeling to determine whether design modifications to the S-ICD coil could result in reductions to S-ICD DFT.