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September 1, 1990CirculationOpen Access

Ventricular refractory period extension caused by defibrillation shocks.

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Why the study?

Do transcardiac shocks extend the ventricular refractory period compared to pacing stimuli in pentobarbital-anesthetized dogs?

Population

Pentobarbital-anesthetized dogs

Comparison

Transcardiac shocks of up to 30 J delivered to… vs Pacing stimuli

Design

Preclinical

Authors

RSRobert J. SweeneyRGRobert M. GillMSMitchell I. Steinberg

Discussion

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Overview

Hypothesis-generating for defibrillation mechanisms in dogs; leaves open translation to human arrhythmia management.

Key Points

  • To determine how defibrillation shocks affect the refractory period of myocardial tissue during different phases of the electrical cycle.
  • Delivered transcardiac shocks and pacing stimuli to anesthetized dogs' myocardial tissue.
  • Examined the timing of shocks relative to the electrical cycle, primarily during electrical systole.
  • Measured the extension of the refractory period using left ventricular pacing.
  • A 30-J shock delivered 10 msec before the end of the refractory period extended it by 63 +/- 15 msec (p < 0.001).
  • A 30-J shock delivered 40 msec earlier extended the refractory period by only 25 +/- 10 msec (p < 0.001).
  • A 5-J shock produced 36 +/- 18 msec (p < 0.005) when delivered late and only 10 +/- 8 msec (p < 0.001) when delivered early.

Structured PICO

Do transcardiac shocks extend the ventricular refractory period compared to pacing stimuli in pentobarbital-anesthetized dogs?

P
Population
Pentobarbital-anesthetized dogs
I
Intervention
Transcardiac shocks of up to 30 J delivered to myocardial tissue at different times in the electrical cycle
C
Comparator
Pacing stimuli
O
Outcome
Extension of the ventricular refractory period as determined by left ventricular pacingsurrogate

Transcardiac shocks delivered late in electrical systole selectively extend the ventricular refractory period, providing a potential mechanism for ventricular defibrillation.

Cite This Study

Sweeney et al. (1990) studied this question.

synapsesocial.com/papers/6a75fca774b63c188eb20c84https://doi.org/10.1161/01.cir.82.3.965
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Also Consider

Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context:

  1. 1Improved defibrillation thresholds with large contoured epicardial electrodes and biphasic waveforms.1987 · 211 citations
  2. 2Influence of shock strength and timing on induction of ventricular arrhythmias in dogs1988 · 139 citations
  3. 3Epicardial activation after unsuccessful defibrillation shocks in dogs1988 · 74 citations
  4. 4Comparison of the defibrillation threshold and the upper limit of ventricular vulnerability.1986 · 250 citations
  5. 5Interaction of sequential stimuli applied during the relative refractory period in relation to determination of fibrillation threshold in the canine ventricle.1975 · 54 citations