Acute cardiac care & resuscitation

Does transthoracic impedance influence termination and recurrence of ventricular fibrillation during impedance-compensated shocks for out-of-hospital cardiac arrest? A retrospective study

ResuscitationPublished retrospective observational study

Authors' conclusion

Despite impedance-compensated defibrillation, TTI ≥100 Ω remains associated with reduced likelihood of VF/pVT termination in OHCA. In contrast, TTI does not appear to influence the risk of recurrent VF/pVT following successful termination.

Study context

Population
Non-traumatic out-of-hospital cardiac arrest (OHCA) in patients aged ≥16 years with an initial shockable rhythm, January 2019 to October 2022cases, 8333 analysable shocks
Participants
1,880 participants
Exposure
The relationship between TTI and VF/pVT termination and recurrence
Outcome
VF/pVT termination (unadjusted)
Methodological detailsmixed-effects logistic regression models applied to shock level data with a random intercept for clustering by patient
  • Mixed-effects logistic regression models applied to shock level data with a random intercept for clustering by patient

Main finding

As reported in the abstract

  • The unadjusted probability of VF/pVT termination declined at TTI values ≥100 Ω, whereas no clear relationship was observed at TTI <100 Ω

Observational data: associations, not effects.

Further findings

VF/pVT termination (adjusted)

Adjusted OR per 1-Ω increase (95% CI)P value
TTI <100 ΩNot associated0.999 (0.993–1.006)P = 0.860
TTI ≥100 ΩLower odds of termination0.994 (0.988–0.999)P = 0.016

Recurrent VF/pVT, among shocks that resulted in VF/pVT termination

Adjusted OR per 1-Ω increase (95% CI)P value
TTINot associated1.003 (0.999–1.006)P = 0.082

Original publication

Does transthoracic impedance influence termination and recurrence of ventricular fibrillation during impedance-compensated shocks for out-of-hospital cardiac arrest? A retrospective study. Resuscitation. Published 25 May 2026. doi:10.1016/j.resuscitation.2026.111151

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