Cardiac Arrhythmias Following Condenser Discharges and Their Dependence Upon Strength of Current and Phases of Cardiac Cycle

The incidence of the various types of arrhythmia induced by defibrillation in anesthetized dogs that had had continuous ventricular fibrillation for 30 seconds was studied as a function of the current strength 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 fisec 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. ADDITIONAL KEY WORDSclosed-chest defibrillation countershock energy content of shock heart block premature atrial contraction premature ventricular contraction paroxysmal tachycardia idioventricular contraction• Electric shock can both induce and terminate cardiac arrhythmias and it is desirable to terminate the unwanted arrhythmias without at the same time introducing other serious arrhythmias. Peleska has published detailed studies concerning arrhythmias that follow From the

Section: Additional Abstractmentioning

confidence: 99%

Incidence of Arrhythmias in the Dog Following Transthoracic Ventricular Defibrillation with Unidirectional Rectangular Stimuli

Stoeckle

Nellis

Schuder

1968

“…Previous work 1 --has shown the necessity of selecting, for the discharge circuit, parameters that will keep voltage as low as possible, but many questions concerning the optimal parameters for d-c condenser discharges still remain unanswered. Gurvic 3 has described a major portion of existing information on this subject, and Mackay and Leeds 4 have studied optimal parameters for condenser discharges up to 15 microfarads (/AF).…”

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confidence: 99%

“…These values are interrelated, but some are of greater biological importance than others for the given objective. On the basis of our previous results 1 ' '-• 1S we can define the optimal defibrillation impulse as that which produces the least functional and morphological damage to the myocardium. The relative importance of the various physical parameters would appear to be: 1) minimal voltage and current, and 2) minimal delivered electrical energy.…”

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confidence: 99%

Optimal Parameters of Electrical Impulses for Defibrillation by Condenser Discharges

Peleska¹,

Blazek²,

Rabl³

et al. 1966

Self Cite

The defibrillation threshold for various wave forms of condenser discharge, using capacitors from 4 to 200 µF, has been measured. Condenser discharge alone was used, or condenser discharge 0.25 henry (20 ohms) with an iron core series inductance, or condenser discharge, 0.29 henry (27 ohms) inductance, but without the iron core. Statistical analysis of the results showed that the last of these three circuits gave the lowest threshold voltage values. Optimal parameters of inductance-altered discharges are obtained with values of 24, 32, and 50 µF. Detailed analysis of the separate physical parameters of the discharge show that optimal pulse duration is 8.5 to 16.6 msec. Further increase of duration does not decrease the voltage or current for threshold shocks, but merely increases the energy delivered. Pulse duration appears to be one of the more important parameters for successful defibrillation, and for this reason, a series inductance is also important.

“…However, Del Guerico et al,-have observed low cardiac output in three patients undergoing external cardiac massage. Alexander et al 8 reported successful treatment of ventricular tachycardia by transthoracic electric shock in 1961. Their paper was followed by others, particularly from Lown's group *~° which described the successful use of transthoracic shock for terminating a variety of other cardiac arrhythmias.…”

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confidence: 99%

“…In another study, Lown and associates 4 " used a single capacitor which discharged through the chest via a series inductor. Peleska 8 has published a detailed experimental study of the factors which cause certain types of capacitor discharges to "damage" the heart, as indicated by the observation that subsequent defibrillation was more difficult. Numerous other investigators have contributed also to our understanding of the use of capacitor discharges in the treatment of ventricular fibrillation.…”

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confidence: 99%

Transthoracic Ventricular Defibrillation with Square-wave Stimuli: One-Half Cycle, One Cycle, and Multicycle Waveforms

Schuder

Stoeckle

Dolan

1964

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%.