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Related Experiment Videos

Improved internal defibrillation success with shocks timed to the morphology electrogram

W Hsu1, Y Lin, D J Lang

  • 1Department of Tachyarrhythmia Research, CPI/Guidant, St Paul, Minn, USA.

Circulation
|September 4, 1998
PubMed
Summary
This summary is machine-generated.

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Timed defibrillation shocks, synchronized to ventricular fibrillation electrograms, significantly reduced energy requirements and improved predictability compared to asynchronous shocks. This suggests potential for simplified programming in human cardiac devices.

Area of Science:

  • Cardiovascular Research
  • Medical Device Technology
  • Electrophysiology

Background:

  • Previous studies suggested improved defibrillation efficacy with shocks timed to electrogram upslope.
  • This study aimed to prospectively evaluate timed shocks versus asynchronous shocks for reducing defibrillation threshold.

Purpose of the Study:

  • To prospectively determine if algorithm-timed shocks to ventricular fibrillation (VF) upslope reduce defibrillation threshold compared to asynchronous shocks.
  • To assess the impact of shock timing on defibrillation energy requirements and predictability.

Main Methods:

  • A prospective study in ten pigs instrumented for internal defibrillation.
  • Defibrillation threshold (E50) estimated using an up/down method for both timed and asynchronous shocks.

Related Experiment Videos

  • Probability-of-success curves generated to compare energy requirements and predictability.

    • Main Results:

    • Timed shocks required significantly lower energy than asynchronous shocks (P<0.001).
    • E80 was reduced by 15.5% with timed shocks (22.9 J vs. 27.1 J).
    • The probability-of-success curve was significantly narrower with timed shocks, indicating greater predictability.

    Conclusions:

    • Defibrillation threshold is lower and more deterministic when shocks are timed to the electrogram upslope in this animal model.
    • Timed shock delivery may simplify programming of shock intensity for human cardiac devices if similar results are observed.