Key result
Implant high-voltage and follow-up low-voltage impedances strongly correlate with spontaneous shock impedance in S-ICD patients.
Why the study?
Evidence is conflicting regarding the evolution of high-voltage impedance over time, prompting investigation into whether implantation DFT impedance and follow-up low-voltage impedance relate to impedance measured during spontaneous shocks.
Does implantation DFT impedance and follow-up LVI correlate with spontaneous shock impedance in S-ICD patients?
Observational (n=122)
No
Does implantation DFT impedance and follow-up LVI correlate with spontaneous shock impedance in S-ICD patients?
Implantation DFT impedance and follow-up low-voltage impedance strongly correlate with spontaneous shock impedance, supporting their use for optimizing S-ICD function.
Spontaneous shocks in S-ICD patients warrant closer follow-up monitoring; leaves open optimal HVI re-testing protocols at replacement.
Introduction The Subcutaneous Implantable Cardioverter Defibrillator (S-ICD) has become an important treatment option for prevention of sudden cardiac death. High-voltage impedance (HVI) measurement is performed at implantation via defibrillation threshold testing (DFT), with impedance playing a critical role in predicting conversion success. There is conflicting evidence for the evolution of HVI if re-tested during device replacement. In recent years, during follow-up low-voltage shock impedance (LVI) measurement can be performed. Purpose The primary objective is to determine whether DFT impedance is related to the impedance measured years later during spontaneous shock events. Additionally, we evaluate whether LVI measured during follow-up is related to HVI. Methods We included 122 patients undergoing S-ICD implantation in this single-centre study in the period from April 2010 until October 2025. HVI measurements were collected at DFT testing and spontaneous shocks. LVI measurements were collected at follow-ups. A retrospective analysis of S-ICD patients receiving intraoperative DFT was performed. Spearman's rank correlation was used to assess the relationship between HVI at DFT and LVI to HVI at spontaneous shock. Results This study included a total of 122 patients, of which 39.3% female and mean age of 41 years ± 16 years. 27 patients (22.1%) received a spontaneous shock during follow-up. Median HVI at DFT was 72.0 Ω (61.5.0–83.0). Median LVI at follow-up was 70.0 Ω (50.0–75.0). Median HVI at spontaneous shock was 62.0 Ω (48.0–70.0). There was a strong positive correlation between impedance at DFT and at spontaneous shock (r(df) = 0.66, p = 0.001) (graph 1). There was also a strong positive correlation between LVI at follow-up and HVI at spontaneous shock (r(df) = 0.69, p = 0.005) (graph 2). Conclusion To conclude, DFT impedance is related to impedance during spontaneous shock and LVI at follow-up is related to HVI. These findings support testing and optimizing DFT HVI at implantation, and the use of LVI testing during follow-up, given their association with spontaneous shock impedance.
No takes yet. Share an insight, caveat, or question.
Smit et al. (2026) conducted an observational in Subcutaneous Implantable Cardioverter Defibrillator (S-ICD) patients (n=122). High-voltage impedance at DFT and low-voltage impedance at follow-up was evaluated on Correlation between DFT impedance and impedance during spontaneous shock events (r = 0.66, p=0.001). High-voltage impedance at implantation and low-voltage impedance at follow-up strongly correlated with impedance during spontaneous shocks in S-ICD patients (r=0.66, p=0.001 and r=0.69, p=0.005).
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: