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. 2025 Jun 10;6(9):1316-1323.
doi: 10.1016/j.hroo.2025.06.002. eCollection 2025 Sep.

Long-term low-voltage impedance measurements in subcutaneous implantable cardioverter-defibrillators

Giacomo Mugnai  1 , Luca Tomasi  1 , Luca Ottaviano  2 , Stefano Viani  3 , Giuseppe Ricciardi  4 , Valter Bianchi  5 , Valeria Rella  6 , Paolo De Filippo  7 , Silvana De Bonis  8 , Roberto Rordorf  9 , Domenico Pecora  10 , Gianluca Botto  11 , Gerardo Nigro  12 , Gianfranco Tola  13 , Fabrizio Caravati  14 , Mariolina Lovecchio  15 , Sergio Valsecchi  15 , Matteo Ziacchi  16 ; “S-ICD Rhythm Detect” Investigators
Affiliations

Long-term low-voltage impedance measurements in subcutaneous implantable cardioverter-defibrillators

Giacomo Mugnai et al. Heart Rhythm O2. .

Abstract

Background: High-voltage impedance (HVI), measured during subcutaneous implantable cardioverter-defibrillator (S-ICD) implantation via defibrillation testing or a synchronized shock, is associated with defibrillation efficacy. Recently, S-ICD systems have been upgraded to automatically perform long-term measurements of low-voltage impedance (LVI) using a 1-V subthreshold pulse.

Objective: This study evaluated LVI as a surrogate for HVI and described its long-term trends in S-ICD recipients.

Methods: We analyzed data from 1226 patients who underwent de novo S-ICD implantation across 15 Italian centers. Weekly averages of LVI and HVI were calculated, and agreement between simultaneous measurements was assessed.

Results: Over a median follow-up of 37 months (interquartile range 20-57 months), 373 paired HVI and LVI measurements were analyzed. LVI strongly correlated with HVI (r = 0.90; 95% confidence interval 0.88-0.92; P < .001), with a mean bias of -3 Ω (limits of agreement -21 to 14 Ω). The mean LVI increased significantly during the first 3 months postimplantation (from 59 ± 14 to 76 ± 16 Ω; P < .001) before stabilizing (77 ± 17 Ω; P = .231). Higher LVI values were observed in overweight/obese patients when subcutaneous device positioning and the 3-incision lead deployment technique were used. Similarly, higher values were obtained when significant subcoil fat was observed and the Prospective, RAndomizEd comparison of subcuTaneOus and tRansvenous ImplANtable cardioverter-defibrillator therapy score was ≥90.

Conclusion: LVI showed strong agreement with HVI during follow-up, supporting its potential use as a noninvasive surrogate for HVI. LVI increased during the initial postimplantation period and subsequently stabilized, possibly reflecting physiological changes.

Keywords: High-voltage impedance; Implantable cardioverter-defibrillator; Low-voltage impedance; Subcutaneous defibrillator; Sudden cardiac death.

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Conflict of interest statement

Dr Ottaviano is a consultant for Boston Scientific and Medtronic. Dr Viani receives speaker fees from Boston Scientific. Dr Bianchi is a consultant for Boston Scientific. Dr De Filippo receives modest consulting fees from Medtronic, Boston Scientific, Abbott, and Biotronik as well as honoraria for advisory board participation from Medtronic. Dr Rordorf receives modest speaking fees from Boston Scientific and Abbott. Dr Botto receives speaker fees from Abbott, Biotronik, Boston Scientific, Medtronic, and MicroPort. Ms Lovecchio and Dr Valsecchi are employees of Boston Scientific. Dr Ziacchi receives speaker fees and educational grants from Abbott, Boston Scientific, Biotronik, and Edwards Lifesciences. The other authors report no conflicts.

Figures

None
Graphical abstract
Figure 1
Figure 1
A: Diagram showing LVI and HVI average values measured during the same week (n = 373). B: Bland-Altman plot: difference between LVI and HVI measures vs their mean. The solid red line indicates the bias and the red dashed lines the limits of agreement between measures. HVI = high-voltage impedance; LVI = low-voltage impedance.
Figure 2
Figure 2
Long-term trend of weekly average low-voltage impedance in the cohort (red line) with standard deviation of values (pink area).
Figure 3
Figure 3
Long-term trends of weekly average low-voltage impedance according to baseline characteristics. CMP = ischemic/non-ischemic dilated cardiomyopathy; HCM = hypertrophic cardiomyopathy; LVEF = left ventricular ejection fraction.
Figure 4
Figure 4
Long-term trends of weekly average low-voltage impedance according to implantation variables.
Supplementary Figure 1
Supplementary Figure 1
See this image and copyright information in PMC

References

    1. Knops R.E., Olde Nordkamp L.R.A., Delnoy P.H.M., et al. Subcutaneous or transvenous defibrillator therapy. N Engl J Med. 2020;383:526–536. - PubMed
    1. Knops R.E., Pepplinkhuizen S., Delnoy P.P.H.M., et al. Device-related complications in subcutaneous versus transvenous ICD: a secondary analysis of the PRAETORIAN trial. Eur Heart J. 2022;43:4872–4883. - PMC - PubMed
    1. Healey J.S., Krahn A.D., Bashir J., et al. Perioperative safety and early patient and device outcomes among subcutaneous versus transvenous implantable cardioverter defibrillator implantations: a randomized, multicenter trial. Ann Intern Med. 2022;175:1658–1665. - PubMed
    1. Heist E.K., Belalcazar A., Stahl W., Brouwer T.F., Knops R.E. Determinants of subcutaneous implantable cardioverter-defibrillator efficacy: a computer modeling study. JACC Clin Electrophysiol. 2017;3:405–414. - PubMed
    1. Gold M.R., Aasbo J.D., El-Chami M.F., et al. Subcutaneous Implantable Cardioverter-Defibrillator Post-Approval Study: clinical characteristics and perioperative results. Heart Rhythm. 2017;14:1456–1463. - PubMed

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