Po-03-060 a manual synchronous low energy shock impedance as a predictor of successful defibrillation testing during subcutaneous icd implantation

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). 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. 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. 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%). LESS impedance values without the need to induce VF can intraoperatively predict the chance of successful DFT.