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January 1, 2001Canadian Journal of Physiology and Pharmacology

The mechanisms of the vulnerable window: the role of virtual electrodes and shock polarity

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Why the study?

Does shock polarity and coupling interval affect arrhythmia induction and virtual electrode polarization in rabbit hearts?

Population

Langendorff-perfused rabbit hearts (n = 7)

Comparison

Monophasic shocks applied from a transvenous… vs Different shock polarities and coupling intervals

Design

Preclinical

Authors

YYYoshio YamanouchiTohoku Institute of TechnologyYCYuanna ChengTongji UniversityPTPatrick TchouElectrophysiology

Discussion

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Implication

Polarity affects arrhythmia induction in rabbit hearts; extends mechanistic insights but leaves open clinical translation.

Key Points

  • To elucidate how virtual electrode polarization, coupling intervals, and shock polarity establish the vulnerable window and mediate cardiac vulnerability to shock-induced arrhythmias.
  • Conducted optical mapping with a potentiometric dye on Langendorff-perfused rabbit hearts (n = 7) to image anterior epicardial electrical responses.
  • Delivered 8 ms monophasic shocks (+/-100 V and +/-200 V) via a transvenous defibrillation lead across varying coupling intervals relative to the cardiac cycle.
  • Cathodal shocks induced significantly more arrhythmias than anodal shocks (53.1 ± 39.3% vs. 33.2 ± 30.1%, P < 0.01), with the vulnerable window consistently located near the T-wave.
  • Anodal shocks produced inward-propagating wavefronts that frequently collided and self-terminated, whereas cathodal shocks generated outward-propagating wavefronts that sustained reentry.

Structured PICO

Does shock polarity and coupling interval affect arrhythmia induction and virtual electrode polarization in rabbit hearts?

P
Population
Langendorff-perfused rabbit hearts (n = 7)
I
Intervention
Monophasic shocks (+/-100 V and +/-200 V, duration of 8 ms) applied from a transvenous defibrillation lead at various coupling intervals
C
Comparator
Different shock polarities (anodal vs cathodal) and coupling intervals
O
Outcome
Arrhythmia induction rate and virtual electrode polarization (VEP) mechanismssurrogate

The probability of VEP-induced phase singularity degenerating into sustained arrhythmia depends on the VEP gradient (coupling interval) and wavefront direction (shock polarity), explaining the vulnerable window and polarity-dependence of vulnerability.

Cite This Study

Yamanouchi et al. (2001) studied this question.

synapsesocial.com/papers/6a82b289d88fdfcf4fa0c7fehttps://doi.org/10.1139/cjpp-79-1-25
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Also Consider

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

  1. 1<b>Myocardial Vulnerability to T Wave Shocks</b>: Relation to Shock Strength, Shock Coupling Interval, and Dispersion of Ventricular Repolarization1996 · 72 citations
  2. 2Optical Transmembrane Potential Measurements During Defibrillation-Strength Shocks in Perfused Rabbit Hearts1995 · 70 citations
  3. 3Optical recordings in the rabbit heart show that defibrillation strength shocks prolong the duration of depolarization and the refractory period.1991 · 175 citations
  4. 4Activation and Repolarization Patterns are Governed by Different Structural Characteristics of Ventricular Myocardium:1996 · 64 citations
  5. 5Ventricular fibrillation is not an anodally induced phenomenon in open-chest dogs1992 · 15 citations