Mechanisms of electrical defibrillation: Impact of new experimental defibrillator waveforms

doi:10.1016/0002-8703(94)90075-2

American Heart Journal

Volume 127, Issue 4, Part 2, April 1994, Pages 970-977

https://doi.org/10.1016/0002-8703(94)90075-2 Get rights and content

Abstract

Six pessible explanations for why some biphasic waveforms have lower defibrillation thresholds than monophasic waveforms of the same duration are as follows: (1) the impedance for the second phase of the biphasic shock is very low because electrode polarization develops during the first phase; (2) the large change in voltage between the first and second phases of a biphasic waveform is responsible for the increased defibrillation efficacy; (3) biphasic waveforms cause less severe detrimental effects in regions of high potential gradient; (4) the first phase of the biphasic waveform restores activity of the sodium channels, which makes defibrillation easier for the second phase; (5) the potential gradient required for defibrillation is less for biphasic waveforms than for monophasic waveforms; and (6) biphasic waveforms are better able to stimulate the myocardium to induce new action potentials or to cause refractory period prolongation. Evidence shows that, while a few of these proposed mechanisms are incorrect, several of the others may together contribute to the general superiority of biphasic waveforms.

References (41)

HG Li et al.
Defibrillation shocks produce different effects on Purkinje fibers and ventricular muscle: implications for successful defibrillation, refibrillation and postshock arrhythmia
J Am Coll Cardiol
(1993)
KM Kavanagh et al.
Comparison of the internal defibrillation thresholds for monophasic and double and single capacitor biphasic waveforms
J Am Coll Cardiol
(1989)
PD Chapman et al.
Comparative efficacy of monophasic and biphasic truncated exponential shocks for nonthoracotomy internal defibrillation in dogs
J Am Coll Cardiol
(1988)
RA Winkle et al.
Improved low energy defibrillation efficacy in man with the use of a biphasic truncated exponential waveform
Am Heart J
(1989)
EE Johnson et al.
Efficacy of short and long monophasic and biphasic waveforms in internal and external defibrillation [Abstract]
Am Heart J
(1992)
PD Chapman et al.
Comparison of monophasic with single and dual capacitor biphasic waveforms for nonthoracotomy canine internal defibrillation
J Am Coll Cardiol
(1989)
ASL Tang et al.
Ventricular defibrillation using biphasic waveforms: the importance of phasic duration
J Am Coll Cardiol
(1989)
JF van Vleet et al.
Sequential cardiac morphologic alterations induced in dogs by single transthoracic damped sinusoidal waveform defibrillator shocks
Am J Vet Res
(1978)
CF Babbs et al.
Therapeutic indices for damped sinusoidal defibrillator shocks: quantitation of effective, damaging, and lethal electrical doses
GA Ewy et al.
Comparison of myocardial damage from defibrillator discharges at various dosages
Med Instrum
(1980)

JL Jones et al.

Postshock arrhythmias: a possible cause of unsuccessful defibrillation

Crit Care Med

(1980)

S Yabe et al.

Conduction disturbances caused by high current density electric fields

Circ Res

(1990)

BB Lerman et al.

Myocardial injury and induction of arrhythmia by direct current shock delivered via endocardial catheters in dogs

Circulation

(1984)

EG Dixon et al.

Improved defibrillation thresholds with large contoured epicardial electrodes and biphasic waveforms

Circulation

(1987)

S Saksena et al.

Simultaneous biphasic shocks enhance efficacy of endocardial cardioversion defibrillation in man

PACE

(1991)

GH Bardy et al.

Electrode system influence on biphasic waveform defibrillation efficacy in humans

Circulation

(1991)

GP Walcott et al.

Comparison of monophasic, biphasic, and the Edmark waveform for external defibrillation [Abstract]

PACE

(1992)

RAS Cooper et al.

Internal cardioversion of atrial fibrillation in sheep

Circulation

(1993)

RE Ideker et al.

New developments in implantable cardioverter-defibrillator electrodes and waveforms

SA Feeser et al.

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

Circulation

(1990)

Cited by (37)

The effects of second and third phase duration on defibrillation efficacy of triphasic rectangle waveforms
2016, Resuscitation
Citation Excerpt :
Compared with monophasic waveforms, biphasic waveforms that consisting of two phases of opposite polarity significantly decreased the shock strength needed for defibrillation and caused less myocardial dysfunction.5 The second phase of the biphasic shock is believed to neutralize virtual electrodes and tissue polarization residual from the first phase.6 The biphasic waveforms are more effective than monophasic waveforms due to a lesser tendency to re-initiate VF from regions of residual charge left on the myocardium.
Biphasic waveforms are superior to monophasic waveforms for the termination of ventricular fibrillation (VF). However, whether triphasic waveforms are more effective than biphasic ones is still controversial. In the present study, we investigated the effects of second and third phase duration of triphasic rectangle waveform on defibrillation efficacy in a rabbit model of VF.
VF was electrically induced and untreated for 30 s in 20 New Zealand rabbits. A defibrillatory shock was applied with one of the 7 waveforms: 6 triphasic rectangle waveforms and a biphasic rectangle waveform. The triphasic waveforms had identical first duration but with different second and third phase durations. A 5 step up-and-down protocol was utilized for determining the defibrillation threshold (DFT). After a 5 min interval, the procedure was repeated. A total of 35 cardiac arrest events and defibrillations were investigated for each animal.
Two triphasic waveforms with identical first and second phase duration but shorter third phase duration had significantly lower DFT energy than biphasic waveform (0.57 ± 0.18 J vs. 0.80 ± 0.28 J, p = 0.001; 0.60 ± 0.18 J vs. 0.80 ± 0.28 J, p = 0.003). However, no statistical difference in DFT energy was observed between the two triaphsic waveforms that had identical phase duration but different voltages (0.57 ± 0.18 J vs. 0.60 ± 0.18 J, p = 0.638).
Phase durations played a main role on defibrillation success for triphasic rectangle waveforms. The optimal triphasic rectangle waveforms that composed of identical second and first phase durations but with shorter third pulse were superior to biphasic rectangle waveform for ventricular defibrillation.
Current is better than energy as predictor of success for biphasic defibrillatory shocks in a porcine model of ventricular fibrillation
2013, Resuscitation
Citation Excerpt :
Electrical defibrillation is achieved by applying a high voltage pulse on patient's chest by two electrode paddles or pads. To be successful, electrical defibrillation needs the delivery of sufficient current through the heart such to depolarize a large number of myocardial cells and thus to terminate VF.1 The defibrillation current has been shown to be a better physiological indicator than energy for selection of appropriate therapeutic dose when monophasic defibrillatory shocks were employed.2,3
The evidence that monophasic defibrillation success is mainly determined by current is secure. However, modern defibrillators use biphasic waveforms. The aim of this study was to compare energy, peak voltage and peak current in predicting biphasic shock success in a porcine model of ventricular fibrillation (VF) where the impedance varies within a wide of ranges.
In 14 domestic male pigs weighing between 27 and 38 kg, VF was electrically induced and untreated for 15 s. Animals were randomized to receive defibrillation attempts from one of two defibrillators with different impedance compensation methods. A grouped up-and-down defibrillation threshold testing protocol was used to maintain the average success rate in the neighborhood of 50%. After a recovery interval of 5 min, the testing sequence was repeated for a total of 60 test shocks for each animal.
A high defibrillation success was observed when high peak current was delivered. The area under ROC curve for predicting shock success was 0.681 for peak current, 0.585 for peak voltage and 0.562 for energy. The odds ratio revealed that peak current was a better predictor (OR = 1.321, p < 0.001) for defibrillation outcome compared with energy (OR = 0.979, p < 0.001) and peak voltage (OR = 1.000, p = 0.69) when multivariable logistic regression was conducted.
In this porcine model of VF within a wide range of transthoracic impedance, peak current was a better indicator for shock success than the currently used energy for biphasic defibrillatory shocks. This finding may encourage design of new current-based biphasic defibrillators.
Comparison of defibrillation efficacy between two pads placements in a pediatric porcine model of cardiac arrest
2012, Resuscitation
Citation Excerpt :
Transthoracic defibrillation is achieved by applying a high voltage pulse on patient's chest with the aid of two electrodes that may be either manual paddles or self adhesive pads.7 The success of defibrillation depends on the capability to generate sufficient transmyocardial current such that to depolarize a large number of myocardial cells.8 Thus, defibrillation efficacy is influenced by multiple factors, such as paddle/pads size, shock waveform, capacitor size and sequential delivery of shocks.9–11
The placement of defibrillation pads at ideal anatomical sites is one of the major determinants of transthoracic defibrillation success. However, the optimal pads position for ventricular defibrillation is still undetermined. In the present study, we compared the effects of two different pads positions on defibrillation success rate in a pediatric porcine model of cardiac arrest.
Eight domestic male pigs weighing 12–15 kg were randomized to receive shocks using either the anterior–posterior (AP) or the anterior–lateral (AL) position with pediatric pads. Ventricular fibrillation (VF) was electrically induced and untreated for 30 s. A sequence of randomized biphasic electrical shocks ranging from 10 to 100 J was attempted. If the defibrillation failed to terminate VF, a 100 J rescuer shock was then delivered. After a recovery interval of 5 min, the sequence was repeated for a total of approximately 30 test shocks were attempted for each animal. The dose response curves were constructed and the defibrillation thresholds were compared between groups.
The aggregated success rate was 65.6% for AP placement and 43.0% for AL one (p = 0.0005) when shock energy was between 10 and 70 J. A significantly lower 50% defibrillation threshold was obtained for AP pads placement compared with traditional AL pads position (2.1 ± 0.4 J/kg vs. 3.6 ± 0.9 J/kg, p = 0.041).
In this pediatric porcine model of cardiac arrest, the anterior–posterior placement of pediatric pads yielded a higher success rate by lowering defibrillation threshold compared to the anterior–lateral position.
Triphasic and quadriphasic waveforms are superior to biphasic waveforms for synchronized beating of cardiomyocytes
2012, Journal of Electrocardiology
Citation Excerpt :
In contrast to the shortage of systematic studies concerning the optimization of waveforms for synchronized cardiomyocyte contraction, defibrillation has been well investigated, and there are many in vivo studies showing that waveform optimization can result in more efficient devices. The most striking result of these studies is that the cells in the cardiac tissue respond better to waveforms with increasing number of phase changes.5,6 These results have also been shown on cardiomyocytes in vitro when comparing monophasic and biphasic waveforms.7,8
Within pacemaker research few attempts have been made to find an optimal waveform phase sequence that synchronizes beating of cardiomyocytes at an electrode. Multielectrode arrays (MEAs) offer electrophysiological screening of cardiomyocytes serving as a system for preliminary screening of pacing waveform design.
The HL-1 cell line was cultured in MEAs until confluence and stimulated with biphasic, triphasic, and quadriphasic waveforms. The amplitudes required for synchronized beating of the cells were determined.
Triphasic and quadriphasic waveforms were more efficient in eliciting synchronized beating of the HL-1 cells compared with the biphasic waveform because it allows significant reductions in synchronizing voltage amplitudes and reductions in supplied stimulus.
The MEA system allows for a straightforward manner to investigate effects of waveform design on synchronized beating in cardiomyocytes in vitro. Increased number of phase changes in a pacing waveform seems to be the major reason for the reduction in synchronizing amplitudes.
A comparison of defibrillation efficacy between different impedance compensation techniques in high impedance porcine model
2009, Resuscitation
Citation Excerpt :
Transthoracic defibrillation is achieved by applying a high voltage pulse on a patient's chest with two electrodes. The success of defibrillation depends on generating sufficient transmyocardial current to depolarize a large number of myocardial cells.1 The transthoracic impedance (TTI), which includes the electrode–skin interface and the patient impedance, is one of the principal defibrillation parameters that affect the defibrillating current, energy, and therefore the defibrillation efficacy.2
Impedance compensation methods differ markedly among manufacturers and can play an important role in defibrillation success. In this study we compared the efficacy of two different commercial defibrillators based on defibrillation success in a high impedance porcine model of cardiac arrest. The first defibrillator (A) compensates high impedance by controlling current with fixed shock duration, while the second defibrillator (B) by prolonging the shock duration.
In 10 domestic male pigs weighing between 17 and 28 kg, ventricular fibrillation was electrically induced and untreated for 15 s. Animals were randomized to receive defibrillations with either defibrillator A or defibrillator B, at maximum energy settings of which were 200 J for the defibrillator A and 360 J for the defibrillator B. A grouped up-down defibrillation threshold testing protocol was used to compare the success rate between the two defibrillators. A variable resistance, ranging from 80 to 200 ohm was placed in series with the defibrillation pads. After a recovery interval of 5 min, the sequence was repeated for a total of 60 test shocks for each animal.
The measured total pathway impedance was in a range of 108–278 ohm. The combined success rate was 49.5% for the two defibrillators in a total of 600 testing shocks. The success rate was significantly higher when the defibrillator A was employed in comparison with defibrillator B (63% vs. 36%, p = 0.0001).
For transthoracic impedances greater than average, the current-based compensation technique was more effective than the duration-based compensation technique.
Mystery of Biphasic Defibrillation Waveform Efficacy. Is it Calcium?<sup>*</sup>*Editorials published in the Journal of the American College of Cardiology reflect the views of the authors and do not necessarily represent the views of JACC or the American College of Cardiology.
2008, Journal of the American College of Cardiology

View all citing articles on Scopus

^☆: Supported in part by the National Institutes of Health research grant Nos. HL-42760, HL-44066, HL-28429, and HL-33637 and the National Science Foundation Engineering Research Center grant No. CDR-86222011.

View full text

Mechanisms of electrical defibrillation: Impact of new experimental defibrillator waveforms☆

Abstract

J Am Coll Cardiol

J Am Coll Cardiol

J Am Coll Cardiol

Am Heart J

Am Heart J

J Am Coll Cardiol

J Am Coll Cardiol

Sequential cardiac morphologic alterations induced in dogs by single transthoracic damped sinusoidal waveform defibrillator shocks

Am J Vet Res

Therapeutic indices for damped sinusoidal defibrillator shocks: quantitation of effective, damaging, and lethal electrical doses

Comparison of myocardial damage from defibrillator discharges at various dosages

Med Instrum

Postshock arrhythmias: a possible cause of unsuccessful defibrillation

Crit Care Med

Conduction disturbances caused by high current density electric fields

Circ Res

Myocardial injury and induction of arrhythmia by direct current shock delivered via endocardial catheters in dogs

Circulation

Improved defibrillation thresholds with large contoured epicardial electrodes and biphasic waveforms

Circulation

Simultaneous biphasic shocks enhance efficacy of endocardial cardioversion defibrillation in man

PACE

Electrode system influence on biphasic waveform defibrillation efficacy in humans

Circulation

Comparison of monophasic, biphasic, and the Edmark waveform for external defibrillation [Abstract]

PACE

Internal cardioversion of atrial fibrillation in sheep

Circulation

New developments in implantable cardioverter-defibrillator electrodes and waveforms

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

Circulation