A manual synchronous low energy shock impedance as a predictor of successful defibrillation testing during subcutaneous icd implantation

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUND: Current guidelines recommend defibrillation testing (DFT) at the time of subcutaneous implantable cardioverter-defibrillator (S-ICD) implantation. Implant position, patient characteristics and device factors, such as shock impedance, can influence defibrillation success. In order to evaluate the shock impedance, a manual synchronous 10J shock (LESS) can be delivered, without the need to induce ventricular fibrillation (VF). PURPOSE: Our objective was to compare LESS and DFT impedance values and to evaluate the diagnostic performance of LESS impedance for prediction of a successful DFT during S-ICD implantation. METHODS: Consecutive S-ICD implantations were included. Shock impedances were compared by paired t tests. Univariate analysis was performed to investigate factors associated with a successful first shock. A prediction model of successful DFT based on LESS impedance was assessed by logistic regression. Additionally, Receiver Operating Characteristic (ROC) curves and the Hosmer-Lemeshow test were used to evaluate its diagnostic performance. RESULTS: Sixty patients were included (52 ± 14. years; 69% male). There were no significant differences between LESS and DFT impedance values. Patients with a failed first shock had higher BMI (30±3 vs. 25.7±4.3, p = 0.014), higher mean LESS (120±35Ω vs 86. ± 23Ω, p= 0.0013) and DFT impedance (122±33Ω vs 87±24, p= 0.0013). ROC analysis showed that LESS impedance had a good diagnostic performance in predicting a successful conversion test (AUC 84% [95% CI: 0.72-0.92]) with a cutoff value of <94Ω to identify a successful DFT (sensitivity of 71%, specificity of 73%). CONCLUSION: LESS impedance values without the need to induce VF can intraoperatively predict the chance of successful DFT. [Figure: see text] [Figure: see text]