Fransthoracic Ventricular Defibrillatlon with
Square-wave Stimuli: ONE-HALF CYCLE,
)NE CYCLE, AND MULTICYCLE WAVEFORMS
iy John C. Schuder, Ph.D., Harry Stoeckle, M.D., and
Alfred M. Dolan, B.S.E.E.
Downloaded from http://circres.ahajournals.org/ by guest on September 29, 2016
• In 1960 Kouwenhoven, Jude, and Knickerbocker1 reported that adequate circulation of
the blood could be achieved by means of
closed chest cardiac massage. This technique
is said to permit the oxygen demands of the
myocardium to be satisfied by external means
and thereby makes practical the utihzation of
transthoracic electric shock for the reversal of
ventricular fibrillation. 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.
As a result of both these developments, the
use of electric shocks applied by means of
electrodes held on the surface of the chest
has assumed an appreciably increased clinical
importance in the treatment of cardiac arrhythmias. With this increased importance and
use has come a renewal of interest in evaluating the effectiveness of different types of electric shocks in order to find the most satisfactory waveform. This interest has led to the
development of several types of external defibrillators which deliver capacitor discharges.
From the University of Missouri School of Medicine, Columbia, Missouri.
Supported by a grant from the Life Insurance
Medical Research Fund.
Presented in part at the Thirty-sixth Scientific Sessions of the American Heart Association, October 25,
1963.
Received for publication March 2, 1964.
258
One type, suggested by Kouwenhoven and
Knickerbocker,7 uses capacitors charged to
opposite polarities which are discharged in
turn through a series circuit composed of an
inductor and the patient. In another study,
Lown and associates4" used a single capacitor
which discharged through the chest via a series inductor. Peleska8 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.9'12 In addition to the various capacitor discharge systems, the 60 cycles/sec sinusoidal defibrillators described by Guyton and Satterfield13
and by Kouwenhoven's group14 continue to
be employed.
While the clinical results obtained with the
presently utilized methods are most impressive, a systematic experimental evaluation of
a wide variety of waveforms appears necessary if the most satisfactory type of shock is
to be found. An almost endless variety of
waveforms can be generated at low power
levels with apparatus commercially available.
The present paper describes a very high
powered and rather specialized amplifier
which accepts the output from the low level
generators and makes the same waveforms
available at the much higher levels required
for transthoracic electric shock. This amplifier
is being utilized for a systematic experimental
study of the effectiveness of various square
waves in the treatment of ventricular fibrillation.
Circulation Rtsttrcb, Vol. XV, Stpfmbrr 1964
259
TRANSTHORACIC VENTRICULAR DEFIBRILLATION
Methods
SPECIAL EQUIPMENT
Downloaded from http://circres.ahajournals.org/ by guest on September 29, 2016
A block diagram of the equipment which is
described in greater detail elsewhere,15 is shown
in figure 1. The energy is stored in two 1,000
microfarad capacitor banks which are charged
to opposite polarities. The stored energy is then
released to the experimental animal in controlled
fashion by means of two banks of power tubes.
Each bank, consisting of 11 type 7094 beam
power transmitting tubes, is capable of supplying
over 10 amperes of current to the thorax of an
animal. The control signals for the banks of power
tubes are derived from a modulated radio frequency carrier which is inductively coupled into
the high-power blocks and demodulated before
being applied to the grids of the power tubes.
The top bank of tubes conducts current which
passes through the subject in one direction and
the bottom bank conducts current which passes
through the subject in the opposite direction.
If current waveforms of only one polarity are
desired, the two capacitor banks are operated in
parallel and the two banks of tubes are also used
in parallel. This mode of operation yields peak
currents in excess of 20 amperes. When used on
an animal with chest resistance of 60 ohms, 20
amperes correspond to a power of 24,000 watts.
An important feature of the amplifier is that its
output impedance is large in comparison to that
of the chest. Hence, the amplifier tends to deliver
a shock of predetermined current waveform and
amplitude despite variations of chest impedance
from animal to animal and despite changes of
electrode-skin resistance from procedure to procedure on a given animal. In contrast to the results with low impedance sources, the power
supplied to the chest increases with increasing
chest impedance levels.
In order that the amplifier may be used both
to induce fibrillation and to terminate it, a manual
selector switch (not shown on diagram) in the
input circuit of the signal frequency amplifier
allows the operator to pick one of three types of
shock. The first of these is usually a low current
60 cycles/sec shock for the induction of fibrillation, the second is the waveform under investigation, and the third is a highly effective defibrillatory shock. The amplitudes and durations of
each of these signals can be independently adjusted. A two-channel direct-writer is used for
recording the slower current and voltage waveforms. Faster waveforms are displayed on a
cathode-ray oscilloscope.
+ HV
•2000 V
1000 pf
POWER
TUBES
DEMODULATOR
PATIENT ELECTRODES
MODULATED
AMPLIFIER
POWER
TUBES
DEMODULATOR
1000 pf
RADIO
FREQUENCY
OSCILLATOR
SIGNAL
FREOUENCY
AMPLIFIER
FROM
LOW-LEVEL
SIGNAL
GENERATOR
- 2000 V
• -HV
FIGURE 1
Block diagram of high powered amplifier used for transthoradc ventricular defibriUation.
CircnUtion Rtsttrcb, Vol. XV, Sipumhtr 1964
SCHUDER, STOECKLE, DOLAN
260
PROCEDURE
Downloaded from http://circres.ahajournals.org/ by guest on September 29, 2016
Six dogs were used in two groups of three
animals each to evaluate the effectiveness of any
given waveform in the treatment of ventricular
fibrillation. The first three animals were anesthetized with pentobarbital sodium injected intravenously at 27.5 mg/kg body weight. Sometimes
additional anesthesia, up to 40% of the initial
dose, was required during the procedure. The
operating tables on which animals lay were
equipped with rubber tips on the legs and insulating mats between the animal and the table.
These precautions guaranteed that the current
flowed between the two electrodes held on
the chest and not through alternate paths to
ground. The electrocardiograph cables, which
were connected to the animals by means of
needle electrodes inserted subcutaneously in the
limbs, terminated in a junction box and a selector
switch was used to choose the desired signal for
display on a cathode-ray oscilloscope. The same
selector switch served to isolate the animal from
the oscilloscope during the actual shock.
The first animal was given a low current shock
(usually 60 cycles/sec, sinusoidal). Ventricular
fibrillation typically followed the first shock; but
if it did not, the shock was repeated until ventricular fibrillation occurred. After the onset of
ventricular fibrillation, a 30-second waiting period
was allowed to elapse before an attempt was made
to defibrillate with the waveform under investigation. In the event that the initial attempt to
defibrillate failed, a shock of known high effectiveness was utilized to salvage the animal. The
0.5
second and third animals were then treated in
identical fashion. This rotational sequence was
repeated until each animal had undergone 20
such procedures.
If efforts to defibrillate an animal failed after
several shocks with the follow-up waveform, external cardiac massage was used and the animal,
whether surviving or dead, was replaced by
another one for the remainder of the immediate
experiment.
After 60 procedures had been completed with
the first group of animals, the experiment was
repeated with the second group of three animals.
In this way each waveform under investigation
was evaluated on the basis of 120 trials. If defibrillation and an effective cardiac beat were
achieved on the initial trial of any given procedure, it was tabulated as a successful defibrillation. Defibrillation at the second or later attempt
was tabulated as a failure.
Results
Figure 2 illustrates the results of a study
involving the effectiveness of a defibrillatory
shock consisting of a one-half cycle unidirectional square current pulse. Since the family
of curves is plotted from 26 points, and each
point involves 120 trials, this figure summarizes data on 3,120 fibrillation-defibrillation
episodes. Except for the 10-ampere and 50millisecond point, and the 5-ampere and 50millisecond point, both of which appear to be
4
8
16
32
DURATION IN MILLISECONDS
64
128
256
FIGURE 2
Relation between per cent success of ventricular defibrillation and duration of one-half-cycle
unidirectional square-wave shocks.
Circulation Runrcb, Vol. XV, Stpttmhtr 1964
261
TRANSTHORACIC VENTRICULAR DEFIBRILLATION
100
90
80
i
10 AMPERES/
70
$60
LLJ
§ 50
Downloaded from http://circres.ahajournals.org/ by guest on September 29, 2016
1-40
z
o 30 cc
UJ20
/
10 -
J
<6
I
I
0
/
\
-OR
0.5
J
~|
T
10 Amperes
1
1
/
1
|
4
8
1
2
DURATION IN MILLISECONDS
1
16
32
64
128
FIGURE 3
Relation between per cent success of ventricular defibrillation and duration of ten-ampere
one-half-cycle unidirectional and of ten-ampere one-cycle bidirectional shocks.
abnormally depressed, the data yielded relatively smooth curves of effectiveness as a
function of pulse duration.
Figures 3 and 4 compare results obtained
with one-half cycle unidirectional shocks and
those obtained with one-cycle bidirectional
shocks. Figure 3 presents the results for 10ampere shocks and figure 4 the results for
5-ampere shocks. In this particular experiment the one-cycle waveform was obtained
by closing an electronic switch, and thereby
connecting a square wave generator to the
100 90
80 = 70
u.
c/)60
no
J I
5 AMPERES
•
LJ
l
o50
•
5 30
\
-
\
5 AMPERES I
£20
Q_
-
10
0
*
.05
2
4
8
16
DURATION IN MILLISECONDS
32
.
64
— : — *
128
256
FIGURE 4
Relation between per cent success of ventricular defibrillation and duration of five-ampere
one-half-cycle unidirectional and of five-ampere one-cycle bidirectional shocks.
CircnUsion Ruttrcb, Vol. XV, Stpumitr 1964
262
SCHUDER, STOECKLE, DOLAN
Downloaded from http://circres.ahajournals.org/ by guest on September 29, 2016
ampHfier for a time period equivalent to one
cycle of the square wave. Because the instant
of closing the switch was arbitrary, the exact
waveform varied from trial to trial. Two of
the possible waveforms are illustrated in the
figures. An important feature of the onecycle bidirectional shock is that, despite the
arbitrary starting point, the net electrical
charge transport is zero. As in figure 2, the
points corresponding to a 50-millisecond
shock duration seem to be abnormally depressed.
Figure 5 illustrates the results for multicycle square-wave shocks. Their duration was
fixed at 128 milliseconds and their amplitude
at 5 amperes for all shocks. The independent
variable is the fundamental frequency of the
square wave and this is plotted along the
abscissa. Since there is a one-to-one correspondence between frequency and the number of cycles in any fixed duration shock, the
number of cycles in the shock is also plotted
along the abscissa.
Discussion
Limitations of the frequency response of
our apparatus tended to introduce appreciable distortion in one-half cycle unidirectional shocks equal to or less than one millisecond, in one-cycle bidirectional shocks
equal to or less than four milliseconds, and in
multicycle shocks at frequencies equal to or
greater than 250 cycles/sec. Consequently,
some distortion in waveform is observed for
shocks represented by points at the far left
of the curves in figures 2, 3, and 4 and for
the point furthest to the right in the curve of
figure 5.
The 20-ampere curve of figure 2 has a peak
effectiveness of almost 100% for a duration of
4 milliseconds. The 10-ampere curve has a
similar peak value of effectiveness for a duration of approximately 16 milliseconds. Since
the energy in joules introduced into the chest
(which is primarily resistive in nature) is
given by PRt where 1 is the current in am-
100
90
80
co
Seo
: ~u U "1 Lr
•5 AMPERES
0.128 SEC —*|
w 50
40
U
a:
30
UJ
Q.
10
0.5
I
4
8
2
4
8
16
TOTAL NUMBER OF CYCLES
16
32
64
128
32
256
FREQUENCY IN CYCLES PER SECOND
FIGURE 5
Relation between per cent success of ventricular defibrillatum and frequency for 128-millisecond fioe-ampere square-waoe shocks.
Circnl^ion Rtsttrcb, Vol. XV, September 1964
263
TRANSTHORACIC VENTRICULAR DEFIBRILLATION
Downloaded from http://circres.ahajournals.org/ by guest on September 29, 2016
peres, R the resistance in ohms, and t the duration in seconds, it is apparent that the most
effective 10-ampere shock and the most effective 20-ampere shock have about the same
energy content. For a chest resistance of 60
ohms this energy is 96 joules. All the curves
of figure 2 demonstrate that for a given amplitude of current there is an optimal duration,
and that shocks which are longer than this
optimum are less effective. It is our distinct
impression that, while shocks with durations
less than that corresponding to peak effectiveness usually produce a prompt return to a
normal sinus rhythm when defibrillation is
achieved, those of greater durations often
produce transitory severe arrhythmias.
The curves are generally, but not exactly,
compatible with the hypothesis that the effectiveness of a shock is a function only of its
energy content provided the level of current
is above a certain value. Thus in figure 2 if
the 20-ampere curve were to be translated
horizontally to the right by multiplying its
abscissa values by four, it would coincide approximately with the 10-ampere curve over
only a limited range. The 5-ampere curve, regardless of energy content, never yields a
very high level of effectiveness.
Perhaps the most striking feature of the
curves of figures 3 and 4 is the apparent
broadening of the range of high effectiveness
for the bidirectional shocks as compared to
the corresponding unidirectional shocks of the
same duration and energy content. For both
the 5-ampere and the 10-ampere shocks, one
finds that the bidirectional waveform continues to be very effective at durations for
which the effectiveness of the corresponding
unidirectional pulses is noticeably reduced. It
is again our impression that the arrhythmias
associated with the longer unidirectional
pulses are much more severe than those occurring when the bidirectional shocks of the
same duration are utilized. It appears that
the values of peak effectiveness for given
current levels are almost identical for both
unidirectional and bidirectional shocks.
Since frequency is the independent variable for the curve of figure 5, and shock
Cinnlmtiom Research, Vol. XV, September 1964
amplitude and duration are fixed, the energy
content is the same for all shocks. While the
results indicate very low effectiveness for both
extremes of frequency, the curve shows a
maximal effectiveness of about 70%. It is interesting that this maximum is similar to that
observed for both the most effective 5-ampere
one-half-cycle unidirectional shock and the
most effective 5-ampere one-cycle bidirectional shock. The rather low effectiveness
found at 256 cycles/sec differs from the results observed by Crowley et al.10 for internal
defibrillation.
Summary
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%.
Acknowledgment
The authors express appreciation to James K.
West for constructing the apparatus and to Carl
F. Ehrlich, Jr., Shan Lin Hou, B. J. McClatchey,
and Jerry D. Benedict for extensive assistance
with the experimental procedure.
References
1. KOUWENHOVEN, W. B., JuDE, J. R., AND KNICKERBOCKER, G. G.: Closed-chest cardiac massage.
J. Am. Med. Assoc. 173: 1064, 1960.
2.
DEL GUERICO, L. R. M., COOMARASWAMY, R. P.,
AND STATE, D.: Cardiac output and other
hemodynamic variables during external cardiac
massage in man. New Engl. J. Med. 269:
1398, 1963.
3. ALEXANDER, S., RLETCER, R., AND LOWN, B.:
Use
of external electric countershock in the treat-
264
SCHUDER, STOECKLE, DOLAN
ment of ventricular tachycardia. J. Am. Med.
Assoc. 177: 916, 1961.
4.
5.
6.
LOWN, B., NEUMAN, J., AMARASINCHAM, R., AND
11. GURVICH, N. L., AND YUNIEV, G. S.: Restoration
BERKOVITS, B. V.: Comparison of alternating
current with direct current electroshock across
the closed chest Am. J. Cardiol. 10: 223, 1962.
of heart rhythm during fibrillation by a condenser discharge. Am. Rev. Soviet Med. 4:
252, 1947.
LOWN, B., AMARASINCHAM, R., AND NEUMAN,
12. WECRIA, R., AND WICCERS, C. J.: Factors deter-
J.: New method of terminating cardiac arrhythmias. J. Am. Med. Assoc. 182: 548, 1962.
LOWN, B., PERLROTH, M. G., KATDBEY, S., ABE,
mining the production of ventricular fibrillation by direct currents. Am. J. Physiol. 131:
104, 1940.
T., AND HARKEN, D. E.: "Cardioversion" of
13. GUYTON, A. C , AND SATTERFIELD, J.: Factors
atrial fibrillation. New Engl. J. Med. 269: 325,
1963.
7.
KOUWENHOVEN,
concerned in electrical defibrillation of heart
particularly through unopened chest. Am. J.
Physiol. 167: 81, 1951.
W . B . , AND KNICKERBOCKER,
Downloaded from http://circres.ahajournals.org/ by guest on September 29, 2016
G. G.: The development of a portable defibrillator. Trans. Am. Inst. Elec. Engr. part
3. 81: 428, 1962.
8. PELESKA, B.: Cardiac arrhythmias following condenser discharges and their dependence upon
strength of current and phase of cardiac cycle.
Circulation Res. 13: 21, 1963.
9. MACKAY, R. S., AND LEEDS, S. E.: Physiological
effects of condenser discharges with application to tissue stimulation and ventricular defibrillation. IRE Trans. Med. Electron. ME-7:
104, 1960.
10.
of regular rhythm in mammalian fibrillating
heart. Am. Rev. Soviet Med. 3: 236, 1946.
GURVICH, N. L., AND YUNIEV, G. S.: Restoration
14.
KOUWENHOVEN, W. B., MlLNOR, W. R., KNICKERBOCKER, G. G., AND CHESNUT, W. R.: Closed
chest defibrillation of the heart. Surgery 42:
550, 1957.
15. SCHUDER, J. C , STOECKLE, H., WEST, J. K., AND
DOLAN, A. M.: A very high power amplifier
for experimental external defibrillation. Proc.
16th Ann. Conf. Engr. Med. Biol. Baltimore,
Conference Committee, 5: 40, 1963.
16. COWLET, R. A., TISCHLER, M., ATTAR, S., AND
TAMRES, A.: Cardiac defibrillation above 60
cycles with a portable square-wave defibrillator. Surgery 51: 207, 1962.
Circuliion RtHtrcb, Vol. XV, Stpttmber 1964
Transthoracic Ventricular Defibrillation with Square-wave Stimuli: One-Half Cycle, One
Cycle, and Multicycle Waveforms
JOHN C. SCHUDER, HARRY STOECKLE and ALFRED M. DOLAN
Downloaded from http://circres.ahajournals.org/ by guest on September 29, 2016
Circ Res. 1964;15:258-264
doi: 10.1161/01.RES.15.3.258
Circulation Research is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 1964 American Heart Association, Inc. All rights reserved.
Print ISSN: 0009-7330. Online ISSN: 1524-4571
The online version of this article, along with updated information and services, is located on the
World Wide Web at:
http://circres.ahajournals.org/content/15/3/258
Permissions: Requests for permissions to reproduce figures, tables, or portions of articles originally published in
Circulation Research can be obtained via RightsLink, a service of the Copyright Clearance Center, not the
Editorial Office. Once the online version of the published article for which permission is being requested is
located, click Request Permissions in the middle column of the Web page under Services. Further information
about this process is available in the Permissions and Rights Question and Answer document.
Reprints: Information about reprints can be found online at:
http://www.lww.com/reprints
Subscriptions: Information about subscribing to Circulation Research is online at:
http://circres.ahajournals.org//subscriptions/