Transthoracic Ventricular Defibrillation Research Articles

External cardioversion of atrial fibrillation: comparison of biphasic vs monophasic waveform shocks

It is well established in transthoracic ventricular defibrillation that biphasic truncated waveform shocks are associated with superior defibrillation efficacy when compared with damped sine wave monophasic waveform shocks. The aim of this study was to explore whether biphasic waveform shocks were superior to monophasic waveform shocks for external cardioversion of atrial fibrillation (AF). Fifty-seven patients in whom cardioversion of AF was indicated were randomized in this prospective study, to transthoracic cardioversion with either monophasic damped sine waveform shocks or biphasic impedance compensating waveform shocks. In the group randomized to monophasic waveform shocks (27 patients), a first shock of 150 J was delivered, followed (if necessary) by a 360 J shock. In the biphasic waveform group (30 patients), the first shock had an energy of 150 J and (if necessary) a second 150 J was delivered. All shocks were delivered in the anterolateral chest pad position. Sinus rhythm was restored in 16 patients (51%) with the first monophasic shock and in 27 patients (86%) with the first biphasic shock. The difference was statistically significant (P=0.02). After the second shock, sinus rhythm was obtained in a total of 24 patients (88%) with monophasic shocks and in 28 patients (93%) with biphasic shocks. No complication was observed in either group and cardiac enzymes (CK, CKmb, troponin I, myoglobin) did not show any significant changes. This study suggests that at the same energy level of 150 J, biphasic impedance compensating waveform shocks are superior to monophasic damped sine waveform shocks cardioversion of atrial fibrillation.

Part 6: Advanced Cardiovascular Life Support

Part 6: Advanced Cardiovascular Life Support

Biphasic Better Than Monophasic Shock in AF

Preliminary work suggests that biphasic waveforms are better than monophasic waveforms for transthoracic ventricular defibrillation. These authors

Comparison of a novel rectilinear biphasic waveform with a damped sine wave monophasic waveform for transthoracic ventricular defibrillation

We compared the efficacy of a novel rectilinear biphasic waveform, consisting of a constant current first phase, with a damped sine wave monophasic waveform during transthoracic defibrillation. Multiple studies have shown that for endocardial defibrillation, biphasic waveforms have a greater efficacy than monophasic waveforms. More recently, a 130-J truncated exponential biphasic waveform was shown to have equivalent efficacy to a 200-J damped sine wave monophasic waveform for transthoracic ventricular defibrillation. However, the optimal type of biphasic waveform is unknown. In this prospective, randomized, multicenter trial, 184 patients who underwent ventricular defibrillation were randomized to receive a 200-J damped sine wave monophasic or 120-J rectilinear biphasic shock. First-shock efficacy of the biphasic waveform was significantly greater than that of the monophasic waveform (99% vs. 93%, p = 0.05) and was achieved with nearly 60% less delivered current (14 +/- 1 vs. 33 +/- 7 A, p < 0.0001). Although the efficacy of the biphasic and monophasic waveforms was comparable in patients with an impedance < 70 ohms (100% [biphasic] vs. 95% [monophasic], p = NS), the biphasic waveform was significantly more effective in patients with an impedance > or = 70 ohms (99% [biphasic] vs. 86% [monophasic], p = 0.02). This study demonstrates a superior efficacy of rectilinear biphasic shocks as compared with monophasic shocks for transthoracic ventricular defibrillation, particularly in patients with a high transthoracic impedance. More important, biphasic shocks defibrillated with nearly 60% less current. The combination of increased efficacy and decreased current requirements suggests that biphasic shocks as compared with monophasic shocks are advantageous for transthoracic ventricular defibrillation.

Double pulse transthoracic defibrillation in the calf using percent fibrillation cycle length as spacing determinate.

Recent studies have found that when multiple pulses of energy are used for defibrillation with implantable electrodes, the spacing between these pulses is better determined as a percentage of the fibrillation cycle length (CL), rather than as a fixed function of time. Here, this concept is further tested in the transthoracic defibrillation of calves, which are approximately the size of heavy humans. Eleven 90-110 kg calves (101 +/- 6 kg) were used in evaluating the effectiveness in achieving transthoracic ventricular defibrillation of ten double pulse waveforms (two 50 A 4-ms rectangular monopulses) having leading edge-to-edge spacings of 4 ms (a 50 A 8-ms rectangular monopulse) and 50, 60, 70, 80, 90, 100, 110, 120, 130 percent fibrillation CL, respectively. In each of these waveforms, the total time when 50 A current was flowing (on time) was 8 ms. Our results show an unequivocal adverse interaction between the pulses, when the spacing is around 60%-70% fibrillation CL; but that the two pulses combined to defibrillate as effectively as a single 8-ms pulse when the spacing is around 110%-130% fibrillation CL. Electrocardiographic analysis suggests that the adverse interaction is due to a refibrillation phenomenon. This study confirms that double pulses can interact and have a negative effect on defibrillation efficacy. Our data suggests that the mechanism of this interaction involves the second pulse reinitiating fibrillation when the pulse separation is in a critical range of values. Our results are also compatible with the hypothesis that the spacing of multiple pulses is better determined as a percentage of the fibrillation CL than as absolute time, although more study is necessary to fully test this hypothesis.

Chronic cardiac changes following transthoracic ventricular defibrillation in the dog

Chronic cardiac changes following transthoracic ventricular defibrillation in the dog

Transthoracic ventricular defibrillation in the 100 kg calf with symmetrical one-cycle bidirectional rectangular wave stimuli.

From 2760 fibrillation-defibrillation episodes in 100 kg calves, the effectiveness of reversing ventricular fibrillation of 30 s duration with symmetrical one-cycle bidirectional rectangular-wave shocks was determined. Pulse widths of 0.5-64 ms, pulse amplitudes of 35,50,70,100, and 140 A, and delivered pulse energies in the 93-1567 J range were employed in a primary study involving 39 animals. Families of curves relating percent successful defibrillation and the time intervals required for the return ofventricular activity and of normal sinus rhythm in the postdefibrillation electrocardiograms to the parameters of the delivered shocks were derived. In an eight-calf supplementary study involving 91-110 kg animals, the effectiveness of 50 A, 10 ms bidirectional rectangular wave shocks and 70 A, 6 ms unidirectional rectangular wave shocks were stringently compared by interlacing fibrillation-defibrillation episodes involving 120 bidirectional and 120 unidirectional shocks. When combined with previously published data for unidirectional wave shocks in 100 kg calves, our data suggest that pulse amplitude and pulse width specifications are considerably broader for successful bidirectional rectangular wave shocks than for unidirectional rectangular wave shocks, and that appreciably higher first-shock successful defibrillation (96-99 percent) can be achieved with bidirectional waveforms

Scaling current and energy with body weight: requirements for the transthoracic ventricular defibrillation of calves as they grow from 50 to 150 kg.

To test the hypothesis that the effectiveness of a shock in achieving ventricular defibrillation is relatively independent of body weight if electrode diameter is proportional to the one-third power and current is proportional to the two-thirds power of weight, we studied defibrillation rates in 10 calves as they increased weight. At 50 kg, each calf was subjected to 20 fibrillation-defibrillation episodes using 10.3-cm diameter electrodes and 32-amp, 4-msec rectangular pulses for defibrillation. Two days after the original study, each calf underwent 20 additional episodes involving 44-amp pulses. With the specified scaling of electrode diameter and pulse amplitude, the two studies were repeated at weight intervals of 25 kg as the animals grew. Six calves survived. In the study that started with 32-amp pulses, first-shock success values of 28%, 49%, 66%, 51% and 23% were found in the six surviving calves at 50, 75, 100, 125 and 150 kg, respectively. The corresponding values were 93%, 96%, 93%, 94% and 91% in the study that started with 44-amp pulses. While the results of the 32-amp study fail to support our initial hypothesis, those obtained in the 44-amp current study appear compatible with the hypothesis.

Transthoracic ventricular defibrillation in adults.

A prospective study of the energy required for transthoracic ventricular defibrillation in adults showed that in 42 (81%) out of 52 episodes of ventricular fibrillation shocks of 100 watt-seconds (Ws) of stored energy were successful. Out of 233 episodes, 222 (95%) were converted by 200 W s shocks. Among patients in whom primary ventricular fibrillation occurred within one hour of the onset of acute myocardial infarction, 200 W s shocks were successful in 40 (98%) out of 41 episodes. When low-energy shocks failed, a stored energy of 400 W s invariably succeeded. The need for large and expensive defibrillators that store more than 400 W s and are less readily available is therefore questioned.

Low-Energy Ventricular Defibrillation and Miniature Defibrillators

To the Editor.— When discussing transthoracic ventricular defibrillation, Loeb (232:845, 1975; 235:144, 1976) and Tacker et al (235:144, 1976) overlooked both direct-current (DC) countershock using low-level electrical energy and miniature defibrillators. More than 35 years ago, Wiggers 1 showed that serial low-energy shocks expedite ventricular defibrillation. Recent experiments, corroborating and extending these earlier observations, indicate that only a limited critical mass of ventricle need be defibrillated for restoration of intrinsic cardiac pacemaker function. 2 In humans, prospective investigation of transthoracic defibrillation showed that the stored 200 watt-second (W-sec) DC shock provided an average 3.1 (1.8-4.0) W-sec/kg. This 200 W-sec shock eliminated primary ventricular fibrillation on the first shock in 73 and on the second shock in 7 of 80 cardiac patients. Two others needed higher energy levels for defibrillation. 3 Our early experience confirms this report (Table). Thus, 86 episodes of prospectively assessed human ventricular fibrillation responded to an average

Transthoracic ventricular defibrillation in the dog with truncated and untruncated exponential stimuli.

From 10 560 transthoracic fibrillation-defibrillation episodes in large anesthetized dogs, the effectiveness of 88 types of untruncated and truncated exponential waveforms in reversing ventricular fibrillation was evaluated. The study involved waveforms which could be generated with stored energy levels (in the simple capacitor-switch sense) of 60, 90, 120, and 180 J and initial current levels of 10, 20, 30, 40, 60, 80, and 100 A. The 10-A waveforms were untruncated or truncated at final current values of 5, 7.5, and 9 A. The 20-, 30-, and 40-A waveforms were untruncated or truncated at 5, 10, and 15 A. The 60-, 80-, and l00-A waveforms were untruncated or truncated at the 15-A level.

Transthoracic ventricular defibrillation in the dog with unidirectional rectangular double pulses.

The energy requirement for transthoracic ventricular defibrillation with unidirectional rectangular double pulse shocks was evaluated by means of 4,560 fibrillation-defibrillation episodes in dogs. The results obtained compare unfavourably with those previously observed with single pulse defibrillatory shocks.

Incidence of arrhythmias in the dog following transthoracic ventricular defibrillation with unidirectional rectangular stimuli.

The incidence of the various types of arrhythmia induced by defibrillation in anesthetized dogs that had had continous ventricular fibrillation for 30 seconds was studied as a function of the current strengh and the duration of the unidirectional rectangular pulse used to terminate the fibrillation. Shocks at 10, 20, 40, 80, and 100 amp with durations in the range of 80 µsec through 64 msec were used. At any given energy level the incidence of induced arrhythmias was much larger for the 40-, 80-, and 100-amp shocks than for the 10- and 20-amp shocks. At 10 and 20 amp, the incidence of induced arrhythmias increased with increasing energy content. Premature ventricular contractions were observed at nearly all levels of energy and current, in contrast to other types of arrhythmias that appear to be strongly related to energy content or current amplitude or both.

Transthoracic ventricular defibrillation with very high amplitude rectangular pulses

ARTICLESTransthoracic ventricular defibrillation with very high amplitude rectangular pulsesJ. C. Schuder, G. A. Rahmoeller, S. H. Nellis, H. Stoeckle, and J. W. MackenzieJ. C. Schuder, G. A. Rahmoeller, S. H. Nellis, H. Stoeckle, and J. W. MackenziePublished Online:01 Jun 1967https://doi.org/10.1152/jappl.1967.22.6.1110MoreSectionsPDF (3 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByInfluence of electrical axis of stimulation on excitation of cardiac muscle cells.Circulation Research, Vol. 69, No. 3Accepted, controversial, and speculative aspects of ventricular defibrillationProgress in Cardiovascular Diseases, Vol. 23, No. 3Contour graph for relating per cent success in achieving ventricular defibrillation to duration, current, and energy content of shockAmerican Heart Journal, Vol. 98, No. 2Transthoracic ventricular defibrillation in the 100 kg calf with unidirectional rectangular pulses.Circulation, Vol. 56, No. 5Incidence of Arrhythmias in the Dog Following Transthoracic Ventricular Defibrillation with Unidirectional Rectangular StimuliCirculation Research, Vol. 23, No. 3 More from this issue > Volume 22Issue 6June 1967Pages 1110-1114 Copyright & PermissionsCopyright © 1967 the American Physiological Societyhttps://doi.org/10.1152/jappl.1967.22.6.1110PubMed6027057History Published online 1 June 1967 Published in print 1 June 1967 Metrics

TRANSTHORACIC VENTRICULAR DEFIBRILLATION WITH SQUARE-WAVE STIMULI: ONE-HALF CYCLE, ONE CYCLE, AND MULTICYCLE WAVEFORMS.

A very high powered amplifier for experimental transthoracic ventricular defibrillation has been described. The effectiveness of both one-half-cycle unidirectional and one-cycle bidirectional square waves in terminating ventricular fibrillation first increases, then reaches a maximum and finally decreases as the duration of the shock is increased. With 10- and 20-ampere unidirectional shocks and 10-ampere bidirectional shocks, a maximal effectiveness of substantially 100% was found under the chosen experimental conditions. Five-ampere unidirectional and bidirectional shocks yielded maximal effectiveness of 70%. The effectiveness of a 128-millisecond, 5-ampere, multicycle square-wave shock is a strong function of frequency and has a maximal value of approximately 70%.