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Related Experiment Videos

Transmembrane potential changes caused by monophasic and biphasic shocks

X Zhou1, W M Smith, R K Justice

  • 1Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.

The American Journal of Physiology
|November 14, 1998
PubMed
Summary

Electrical shocks alter cardiac muscle potential differently based on timing and waveform. Biphasic waveforms, especially 5/5-ms, minimize changes in transmembrane potential (DeltaVm) and repolarization time.

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Area of Science:

  • Cardiovascular Physiology
  • Electrophysiology

Background:

  • Cardiac electrophysiology is crucial for heart function.
  • Understanding transmembrane potential changes during electrical stimulation is vital for therapeutic interventions.

Purpose of the Study:

  • To investigate the effects of different electrical shock waveforms and polarities on transmembrane potential change (DeltaVm) and repolarization in guinea pig papillary muscles.
  • To determine how shock timing and fiber orientation influence these electrophysiological responses.

Main Methods:

  • Recorded DeltaVm using a double-barrel microelectrode in isolated guinea pig papillary muscles.
  • Applied monophasic and biphasic (10/10-ms, 5/5-ms) square-wave shocks at various coupling intervals (30-130 ms).
  • Evaluated shock effects during different phases of the action potential and across/along fiber orientation.

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Main Results:

  • Shock polarity induced asymmetrical hyperpolarization and depolarization, with ratios varying by S1-S2 coupling interval.
  • Monophasic shocks caused greater DeltaVm than biphasic shocks.
  • Monophasic and 10/10-ms biphasic waveforms prolonged total repolarizing time (TRT) more than 5/5-ms biphasic waveforms.
  • 5/5-ms biphasic shocks resulted in the smallest DeltaVm, least TRT prolongation, and minimal polarity-dependent dispersion.
  • Shock fields applied along fiber orientation produced larger DeltaVm and TRT prolongation compared to those across fibers.

Conclusions:

  • Shock polarity and timing influence membrane polarization asymmetrically.
  • The 5/5-ms biphasic waveform is optimal for minimizing electrophysiological disruption.
  • Fiber orientation significantly affects transmembrane potential changes and repolarization dynamics during electrical stimulation.