Key result
Implantation high-voltage impedance in EV-ICD strongly tracks shock impedance, running ~16 Ω higher.
Why the study?
Longitudinal high-voltage impedance behavior in the extravascular implantable cardioverter-defibrillator (EV-ICD) and its correlation with shock impedance during defibrillation threshold testing had not been fully characterized.
Observational (n=20)
No
This study defines expected post-implant high-voltage impedance behavior in extravascular ICD recipients, demonstrating strong correlation with defibrillation shock impedance and an early transient decrease at 0–3 weeks that regresses toward baseline.
Background The extravascular implantable cardioverter-defibrillator (EV-ICD) eliminates transvenous leads while providing limited pacing for tachycardia therapy and pause-prevention. Longitudinal high-voltage impedance (HVI) behavior and correlation with shock impedance during defibrillation threshold (DFT) testing have not been fully characterized. Purpose To describe HVI trends and evaluate the association between implantation HVI and shock impedance during defibrillation testing following EV-ICD implantation. Methods Serial HVI measurements were retrospectively assessed in consecutive patients undergoing EV-ICD implantation at a single-center. Defibrillation testing with ventricular fibrillation induction was performed at implant. Patients requiring system revision procedures were excluded. The association between implantation HVI and shock impedance was assessed using Spearman correlation and paired Wilcoxon testing. Longitudinal changes were evaluated using a linear mixed-effects model across predefined intervals: baseline, 0–3 weeks, 3 weeks–6 months, 6 months–1 year, and >1 year. Results Twenty patients (mean age 51.9 years; 25% female) were analyzed. Shock impedance during defibrillation testing was 64.5 ± 13.5 Ω (n = 20). Implantation HVI was 80.4 ± 30.7 Ω (n = 19) and strongly correlated with shock impedance (Spearman ρ = 0.93, p < 0.0001). Implantation HVI was significantly higher than shock impedance (mean difference 15.8 ± 21.6 Ω; p < 0.0001). Median follow-up was 9.7 months. HVI decreased at 0–3 weeks compared with baseline (estimate −22.3 Ω; 95% CI −37.0 to −7.6; p = 0.004). No significant differences were observed at later intervals (all p > 0.05) compared with implantation HVI, and no progressive impedance rise suggestive of system failure occurred. Conclusion Implantation HVI strongly correlates with shock impedance in EV-ICD recipients, with a systematic mean difference of 15.8 Ω. HVI decreases early after implantation but regresses toward baseline. These findings define expected post-implant impedance behavior and may assist in interpretation of EV-ICD diagnostics and system integrity.Correlation Between HVI and Implantation HVXLongitudinal HVI Trend
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Maroutsos et al. (2026) conducted an observational in Extravascular implantable cardioverter-defibrillator (EV-ICD) implantation (n=20). Extravascular implantable cardioverter-defibrillator (EV-ICD) implantation high-voltage impedance (HVI) vs. Shock impedance during defibrillation threshold testing and baseline implantation HVI was evaluated on Association between implantation high-voltage impedance (HVI) and shock impedance, and longitudinal HVI trends (MD 15.8, p=<0.0001). Implantation high-voltage impedance in EV-ICD recipients strongly correlated with shock impedance (ρ=0.93, p<0.0001; MD 15.8 Ω) and transiently decreased at 0–3 weeks (−22.3 Ω, p=0.004).
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