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

Resumo Fundamento O cardioversor-desfibrilador implantável subcutâneo (S-CDI) é uma alternativa segura ao sistema convencional do CDI transvenoso (TV-CDI) para evitar morte súbita. Objetivo Comparar o impacto do tipo de sistema de CDI e técnica cirúrgica na qualidade de vida dos pacientes, bem como a gravidade do desconforto e da dor, entre receptores de S-CDI e TV-CDI. Métodos Pacientes consecutivamente implantados com um sistema S-CDI foram pareados com pacientes com um sistema TV-CDI. Além disso, foram incluídos os pacientes submetidos ao implante de S-CDI após a remoção de um TV-CDI, devido a complicações. Foram avaliadas a qualidade de vida (medida com o questionário de saúde de 12 itens) e a gravidade da dor e desconforto. Significância estatística foi definida como p < 0,05. Resultados Foram analisados 64 pacientes implantados com S-CDI ou TV-CDI sob anestesia local e sedação consciente. Pacientes com sistemas S-CDI e TV-CDI não diferiram significativamente nos escores de qualidade de vida. Os pacientes com S-CDI apresentaram maior nível de dor peri-operatória; nenhuma diferença foi encontrada em relação à gravidade da dor intra-operatória. A magnitude do desconforto estético e dos distúrbios do sono não diferiu entre os grupos.O S-CDI foi implantado em 7 pacientes adicionais após a remoção de um TV-CDI. Todos exceto um desses pacientes recomendaram o sistema S-CDI. Conclusões O tipo de sistema de CDI e a técnica cirúrgica têm impacto insignificante na qualidade de vida dos pacientes. Estes resultados sugerem que a sedação consciente, fornecida por uma equipe experiente de eletrofisiologia, pode ser considerada uma alternativa à anestesia geral para o manejo de pacientes submetidos ao implante de S-CDI. Abstract Background The totally subcutaneous implantable cardioverter-defibrillator (S-ICD) is a safe alternative to the conventional transvenous ICD (TV-ICD) system to prevent sudden death. Objective To compare the impact of the type of ICD system and surgical technique on patients’ quality of life, as well as the severity of discomfort and pain, between S-ICD and TV-ICD recipients. Methods Consecutively implanted patients with an S-ICD system were matched with patients with a TV-ICD system. In addition, patients undergoing S-ICD implantation after removal of a TV-ICD due to complications were included. Quality of life (measured with the 12-item short-form health survey) and severity of pain and discomfort were evaluated. Statistical significance was defined as p < 0.05. Results A total of 64 patients implanted with S-ICD or TV-ICD under local anesthesia and conscious sedation were analyzed. Patients with S-ICD and TV-ICD systems did not differ significantly in quality of life scores. S-ICD patients had a higher level of perioperative pain; no differences were found regarding severity of intraoperative pain. The magnitude of aesthetic discomfort and sleep disturbances did not differ between groups. An S-ICD was implanted in 7 additional patients after removal of a TV-ICD. All but one of these patients recommended the S-ICD system. Conclusions The type of ICD system and the surgical technique have negligible impact on patients’ quality of life. These results suggest that conscious sedation, provided by an experienced electrophysiology team, could be considered as an alternative to general anesthesia to manage patients undergoing S-ICD implantation.

Recent observations suggest that frequent dual-chamber pacing in recipients of implantable cardioverter defibrillators (ICD) may adversely influence clinical outcomes. This prospective, multicenter study examined the relationship between the frequency of atrial (%AP) and ventricular pacing (%VP) and the incidence of atrial (AT) and/or ventricular tachyarrhythmias (VT) in a standard ICD population. A total of 141 consecutive patients with primary and secondary ICD indications were studied. Continuous arrhythmia detection with a dual-chamber ICD revealed paroxysmal AT in 60 (43%) and VT in 72 (51%) patients within 6 months of device implantation. Far-field oversensing of ventricular signals occurred in 13% of all "atrial tachy response" mode switches. Without adjustment for covariates, a higher %AP was associated with an increased incidence of AT (P0.05). However, this association remained only weakly significant after adjustment for covariates using a multivariate model. High New York heart failure functional classes correlated significantly with AT (P = 0.02) and VT (P = 0.007). Rate-modulated pacing, programmed in 1/3 of patients, correlated with occurrence of AT (P = 0.006), but not with occurrence of VT. With respect to dual-chamber pacing, a %AP/= 48% combined with a %VP40% was associated with an increased probability for VT. In conclusion, AT and VT occurred frequently within 6 months after dual-chamber ICD implantation. High rates of DDD/R stimulation were associated with a trend toward higher incidence of AT, VT, or both.