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Choosing the optimal monophasic and biphasic waveforms for ventricular defibrillation.

Publication ,  Journal Article
Walcott, GP; Walker, RG; Cates, AW; Krassowska, W; Smith, WM; Ideker, RE
Published in: Journal of Cardiovascular Electrophysiology
September 1995

The truncated exponential waveform from an implantable cardioverter defibrillator can be described by three quantities: the leading edge voltage, the waveform duration, and the waveform time constant (tau s). The goal of this work was to develop and test a mathematical model of defibrillation that predicts the optimal durations for monophasic and the first phase of biphasic waveforms for different tau s values. In 1932, Blair used a parallel resistor-capacitor network as a model of the cell membrane to develop an equation that describes stimulation using square waves. We extended Blair's model of stimulation, using a resistor-capacitor network time constant (tau m), equal to 2.8 msec, to explicitly account for the waveform shape of a truncated exponential waveform. This extended model predicted that for monophasic waveforms with tau s of 1.5 msec, leading edge voltage will be constant for waveforms 2 msec and longer; for tau s of 3 msec, leading edge voltage will be constant for waveforms 3 msec and longer; for tau s of 6 msec, leading edge voltage will be constant for waveforms 4 msec and longer. We hypothesized that the best phase 1 of a biphasic waveform is the best monophasic waveform. Therefore, the optimal first phase of a biphasic waveform for a given tau s is the same as the optimal monophasic waveform.We tested these hypotheses in two animal experiments. Part I: Defibrillation thresholds were determined for monophasic waveforms in eight dogs. For tau s of 1.5 msec, waveforms were truncated at 1, 1.5, 2, 2.5, 3, 4, 5, and 6 msec. For tau s of 3 msec, waveforms were truncated at 1,2,3,4,5,6, and 8 msec. For tau s of 6 msec, waveforms were truncated at 2,3,4,5,6,8, and 10 msec. For waveforms with tau s of 1.5, leading edge voltage was not significantly different for the waveform durations of 1.5 msec and longer. For waveforms with tau s of 3 msec, leading edge voltage was not significantly different for waveform durations of 2 msec and longer. For waveforms with tau s of 6 msec, there was no significant difference in leading edge voltage for the waveforms tested. Part II: Defibrillation thresholds were determined in another eight dogs for the same three tau s values. For each value of tau s, six biphasic waveforms were tested: 1/1, 2/2, 3/3, 4/4, 5/5, and 6/6 msec. For waveforms with tau s of 1.5 msec, leading edge voltage was a minimum for the 2/2 msec waveform. For waveforms with tau s of 3 msec, leading edge voltage was a minimum for the 3/3 msec waveform. For waveforms with tau s of 6 msec, leading edge voltage was a minimum and not significantly different for the 3/3, 4/4, 5/5, and 6/6 msec waveforms.The model predicts the optimal monophasic duration and the first phase of a biphasic waveform to within 1 msec as tau s varies from 1.5 to 6 msec: for tau s equal to 1.5 msec, the optimal monophasic waveform duration and the optimal first phase of a biphasic waveform is 2 msec, for tau s equal to 3.0 msec, the optimal duration is 3 msec, and for tau s equal to 6 msec, the optimal duration is 4 msec. For both monophasic and biphasic waveforms, optimal waveform duration shortens as the waveform time constant shortens.

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Published In

Journal of Cardiovascular Electrophysiology

DOI

EISSN

1540-8167

ISSN

1045-3873

Publication Date

September 1995

Volume

6

Issue

9

Start / End Page

737 / 750

Related Subject Headings

  • Ventricular Fibrillation
  • Maximum Allowable Concentration
  • Male
  • Female
  • Electric Countershock
  • Dogs
  • Disease Models, Animal
  • Defibrillators, Implantable
  • Cardiovascular System & Hematology
  • Animals
 

Citation

APA
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ICMJE
MLA
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Walcott, G. P., Walker, R. G., Cates, A. W., Krassowska, W., Smith, W. M., & Ideker, R. E. (1995). Choosing the optimal monophasic and biphasic waveforms for ventricular defibrillation. Journal of Cardiovascular Electrophysiology, 6(9), 737–750. https://doi.org/10.1111/j.1540-8167.1995.tb00450.x
Walcott, G. P., R. G. Walker, A. W. Cates, W. Krassowska, W. M. Smith, and R. E. Ideker. “Choosing the optimal monophasic and biphasic waveforms for ventricular defibrillation.Journal of Cardiovascular Electrophysiology 6, no. 9 (September 1995): 737–50. https://doi.org/10.1111/j.1540-8167.1995.tb00450.x.
Walcott GP, Walker RG, Cates AW, Krassowska W, Smith WM, Ideker RE. Choosing the optimal monophasic and biphasic waveforms for ventricular defibrillation. Journal of Cardiovascular Electrophysiology. 1995 Sep;6(9):737–50.
Walcott, G. P., et al. “Choosing the optimal monophasic and biphasic waveforms for ventricular defibrillation.Journal of Cardiovascular Electrophysiology, vol. 6, no. 9, Sept. 1995, pp. 737–50. Epmc, doi:10.1111/j.1540-8167.1995.tb00450.x.
Walcott GP, Walker RG, Cates AW, Krassowska W, Smith WM, Ideker RE. Choosing the optimal monophasic and biphasic waveforms for ventricular defibrillation. Journal of Cardiovascular Electrophysiology. 1995 Sep;6(9):737–750.
Journal cover image

Published In

Journal of Cardiovascular Electrophysiology

DOI

EISSN

1540-8167

ISSN

1045-3873

Publication Date

September 1995

Volume

6

Issue

9

Start / End Page

737 / 750

Related Subject Headings

  • Ventricular Fibrillation
  • Maximum Allowable Concentration
  • Male
  • Female
  • Electric Countershock
  • Dogs
  • Disease Models, Animal
  • Defibrillators, Implantable
  • Cardiovascular System & Hematology
  • Animals