Improved low energy defibrillation efficacy in man with the use of a biphasic truncated exponential waveform

Winkle, Roger A.; Mead, R. Hardwin; Ruder, Michael A.; Gaudiani, Vincent A.; Buch, Wally S.; Pless, Ben D.; Sweeney, Michael B.; Schmidt, Paula

doi:10.1016/0002-8703(89)90665-0

Cited by 200 publications

(45 citation statements)

References 14 publications

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“…I ext is the current injection term that appears in Eq. (2). The currents shown here are the ones that are applied by the electrode that is located at position / ¼ p=2; the currents applied by the other electrode (located at / ¼ 3p=2) have the same magnitude but opposite polarity.…”

Section: Figmentioning

confidence: 99%

Shock-induced termination of reentrant cardiac arrhythmias: Comparing monophasic and biphasic shock protocols

Bragard

Šimić

Elorza

et al. 2013

Chaos: An Interdisciplinary Journal of Nonlinear Science

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In this article, we compare quantitatively the efficiency of three different protocols commonly used in commercial defibrillators. These are based on monophasic and both symmetric and asymmetric biphasic shocks. A numerical one-dimensional model of cardiac tissue using the bidomain formulation is used in order to test the different protocols. In particular, we performed a total of 4.8 Â 10 6 simulations by varying shock waveform, shock energy, initial conditions, and heterogeneity in internal electrical conductivity. Whenever the shock successfully removed the reentrant dynamics in the tissue, we classified the mechanism. The analysis of the numerical data shows that biphasic shocks are significantly more efficient (by about 25%) than the corresponding monophasic ones. We determine that the increase in efficiency of the biphasic shocks can be explained by the higher proportion of newly excited tissue through the mechanism of direct activation. In the present paper, we show how numerical simulations can be used to understand the efficiency of different defibrillation protocols. Fibrillation is a rapid, irregular electrical activity of the heart. This fatal medical condition is usually treated by the application of an external electric shock to the patient chest through external paddle electrodes. The shape of the electric waveforms that are usually applied are either monophasic or biphasic. This means that in the latter the polarity is switched at some point in the course of the application of the shock. Empirical observations suggest that biphasic shocks are more efficient than monophasic shocks in terminating fibrillation. In this paper, by using a simplified mathematical model of cardiac tissue, which, however, includes a realistic response of the cells to large electric fields, we confirm and explain this experimental observation. The model developed here could be used in subsequent studies in order to design and test more complex waveforms, which could be done systematically because the model is simple and not very computationally costly. The next goal is to find the optimal waveform that reduces the energy needed for defibrillatory shocks. This would be of great benefit for patients undergoing defibrillation by limiting the damage to the heart tissue caused by such a strong electric shock.

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Section: Figmentioning

confidence: 99%

Shock-induced termination of reentrant cardiac arrhythmias: Comparing monophasic and biphasic shock protocols

Bragard

Šimić

Elorza

et al. 2013

Chaos: An Interdisciplinary Journal of Nonlinear Science

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show abstract

“…The peak seen at 8.5 msec in the biphasic curves of Figure 9 (top panel) is greater than the neighboring portions of the curve for durations of 7.5 msec and 10.5 msec (p<0.03). The and C was only about 20%, the effectiveness of using just 16 preliminary shocks to choose the optimal V21 for these waveforms may be questioned. In other words, the protocol for choosing waveforms B and C, even though complex due to the sensitivity of success to slight changes in V11 and V21, probably did not consistently select the optimal waveforms.…”

Section: Part Idmentioning

confidence: 99%

Strength-duration and probability of success curves for defibrillation with biphasic waveforms.

et al. 1990

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Certain biphasic waveforms require less energy to defibrillate than do monophasic pulses of equal duration, although the mechanisms of this increased effectiveness remain unclear. This study used strength-duration and percent success curves for defibrillation with monophasic and biphasic truncated exponential waveforms to explore these mechanisms. In part 1, defibrillation thresholds were determined for both high-and low-tilt waveforms. The monophasic pulses tested ranged in duration from 1.0 to 20.0 msec, and the biphasic waveforms had first phases of either 3.5 or 7.0 msec and second phases ranging from 1.0 to 20.0 msec. In part 2, defibrillation percent success curves were constructed for 6.0 msec/6.0 msec biphasic waveforms with a constant phase-one amplitude and with phase-two amplitudes of approximately 21%, 62%, 94%, and 141% of phase one. This study shows that if the first phase of a biphasic waveform is held constant and the second phase is increased in either duration or amplitude, defibrillation efficacy first improves, then declines, and then again improves. For pulse durations of at least 14 msec, the second-phase defibrillation threshold voltage of a high-tilt biphasic waveform is higher than that of a monophasic pulse equal in duration to the biphasic second phase (p<0.05), indicating that the previously proposed hypothesis of stimulation by the second phase is not the sole mechanism of biphasic defibrillation. These facts indicate the importance of the degree of tilt for the defibrillation efficacy of biphasic waveforms and suggest at least two mechanisms exist for defibrillation with these waveforms, one that is more effective for smaller second phases and another that becomes more effective as the second phase is increased. (Circulation 1990;82:2128-2141 C ertain biphasic waveforms require less energy to defibrillate or produce less cardiac dysfunction than do monophasic pulses of equal duration.1-4 The lower defibrillation threshold (DFT) for certain biphasic waveforms has important implications for the effectiveness and lifespan of automated, implantable cardioverter/ defibrillators with power supplies that are constrained by space considerations.5-7Research seeks to answer the following two closely related questions. First, what is the mechanism that

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“…This was not introduced in modern medicine for implantable defibrillators until 1989 when it had been appreciated that lower energies were required and that therefore smaller capacitors could be used. 36 Clinical evidence that the same held true for out-of-hospital external defibrillation followed. 37 But Kouwenhoven had worked with alternating current and progressively reduced the number of cycles to oneoriginally he called it a diphasic discharge -and regarded this as optimal.…”

Section: Took a Hen Which I Knocked Down With The First Shock Dirementioning

confidence: 89%

Never quite there: a tale of resuscitation medicine

Chamberlain

2003

Clinical Medicine

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Improved low energy defibrillation efficacy in man with the use of a biphasic truncated exponential waveform

Cited by 200 publications

References 14 publications

Shock-induced termination of reentrant cardiac arrhythmias: Comparing monophasic and biphasic shock protocols

Shock-induced termination of reentrant cardiac arrhythmias: Comparing monophasic and biphasic shock protocols

Strength-duration and probability of success curves for defibrillation with biphasic waveforms.

Never quite there: a tale of resuscitation medicine

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