In tests on 11 mature dogs, immobilized by means of an automatic blocking and synchronization system, artefact free EKG were obtained, beginning 0.04-0.06 sec after passage of a defibrillating current. Different versions of the start of fibrillation were noted, in application of the defibrillating stimulus in the early phase of the cardiac cycle. A swinging phenomenon, increasing amplitude, of fibrillation was noted for 0.4-1.5 sec after delivery of a subthreshold stimulus. Conditions for a positive outcome of repeated defibrillation were found, and a relationship was noted between the configuration of the exciting process with respect to the lines of force of the defibrillating current and the defibrillation threshold. It was shown that the initial EKG dynamics after defibrillation is based on a gradual shift of the pacemaker from the myocardium of the ventricles to the sinus node, through phases of atrioventricular and atrial automatism

Bikov, I. I.

Chebotarov, Y. P.

Nikolaev, V. G.

English

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NASA TM-76002
INITIAL DYNAMICS OF THE EKG DURING AN ELECTRICAL DEFIBRILLATION
OF THE HEART
I.I.  Bikov, Y a. P . Chebotarov and V.G. Nikolabv
Translation of "Pochatkova dynamika EKG pri elektrychniy
defibrylyatsii sertsya," Fiziologichnyy Zhurnal Akademii
Nauk Ukrains'koy RSR, Vol-15., No. 3, 1969, pp. 322-327
(NASA-Tip-76092) INITIAL DYNAMICS OF THE EKG
	
080-21019
DURING AN ELECTRICAL DEFIBRILLATION OF THE
HEART (National Aeronautics and Space
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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION,
WASHINGTON, D.C. 20546 	 APRIL 1980
INITIAL DYNAMICS OF THE EKG DURING AN ELECTRICAL DEFIBRILLATION
OF THE HEART
I.I. Bikov, Y a.P. Chebotarov and V.G. Nikolaev
Dept. of Anat. and physiol., Lugansk Pedagog. Inst., Lugansk
There are no data in the literature on the dynamics of the EKG
immediately after application of a defibrillating discharge, since re-
cordings of the electrical activity of the heart begin no sooner than
a few seconds after passage of a powerful (5-15 A) current through the
target [1, 51.
i
i
/322*1
Also, the transition process in the development of fibrillation
after an electrical trauma has not been studied, and there is no knowl-
edge of the effect of a subthreshold electrical. stimulus on the develop-
ment of fibrillation. These delicate questions are especially important
for the electrophysiological interpretation of many authors [2, 3, 5, 81
of the positive effect of repeated defibrillation, in those cases when
single trials fail.
In this study, cardiograms were recorded before and 0.04-0.06 sec
after application of a defibrillating discharge (in all figures, the
time of the discharge is designated by a dot).
Method
In the studies, an experimental defibrillator [7] and a system of
automatic devices were used, which permitted the use of these operations:
1. closing the "damping" swatch of the electrocardiograph; 2. switching
on the recording electrodes and closing the equivalent arms of the
electrocardiograph input switches; 3. connection of the defibrillation
electrodes to the defibrillator; 4. giving commands to turn on the de-
fibrillator; 5. switching off the defibr_".lator electrodes from the
target; 6. restoring the switches of the recording electrodes of the
electrocardiograph; 7. switching on the "damper."
Numbers in the margin indicate pagination in the foreign text.
l
a1
In this case, a recording interval of 0.1-0.2 sec was recorded on
the EKG (Fig. la).
a	 b6
06	 f3	 q
4 11	 g Icon
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e
In
Fig. 1. Method of study 4^ind examples of fibrillation: a. interruption
of record in fatigue of synchronizer, b. artefact of muscle tremor after
passage of pulse; c. example of effect of pulse on normally function-
ing heart (65% of threshold current strength); d. fibrillation through
series of decreasing -.arge amplitude oscillations (experiment 9; 58%
of threshold current strength); e. example of fibrillation through
irregular low amplitude oscillations (experiment 9; 80% of threshold
current strength.). Key: f. 1 mV	 g. 1 sec
The studies were conducted on 11 random bred dogs weighing from 6
to 23 kg. The animals were under morphine anesthesia, at a dose of 0.5
ml of 1% morphine solution per kg of weight.
The electrocardiograms were recorded with a EKPS-Ch instrument, the
femoral artery pressure was monitored kymographically and the respiration,
by means of a pneumatic cuff.
Since muscle tremor developed after passage of the defibrillating
stimulus, which masks the electrocardiogram (Fig. lb), the skeletal
muscles were disengaged with listenon, and the study was conducted with
artificial respiration. In this case, noticeable artefacts were absent
( Fig 1c)
Fibrillation was induced with 127 V alternating current, which was
passed through electrodes inserted under the skin of the right front and
left rear paws for a period of 2 sec.
In this case, the start of fibrillation was not successfully re-
corded despite the clear operation of the synchronization system and
I	 2
out off of the stimulating current in the zero phase, since the bioelec-
tric complexes were masked by a slowly (over 4 -8 sec) decreasing potential,
which evidently is connected with electrochemical shifts in the tissues,
caused by the persistent effect of the alternating current.
Records of the initial fibrillation were obtained by stimulation of
the heart with an electrical stimulus in the "early" phase of the electro-
cardiographio cycle, the rising arm and peak of the T spike.
Defibrillation was performed with 0.04 sec long alternating cur-
	 /323
rent, which was made up of the symmetrical first two and decreasing
third and fourth half waves. The pulse of this configuration was well
recommended in studies conducted earlier.
The defibrillation threshold was produced 10-,?0 sec after the
electrical trauma, by stepwise presentation of stimuli of increasing
magnitude. The strength of the current was recorded in this case.
Fibrillation of the hearts of the same animals was induced repeat-
edly, with 15 min intervals between individual electrical trauma.
Results and Discussion
Fibrillation. Basicallly, only 2 more or less t ypical variations. can
'be sketched in the dynamics of each fibrillation: 1. large, regular
sinusoidal oscillations, which gradually die out and become irregular
(Fig. ld) 2. a small spike process of irregular shape, which differs
very little from some types of cardiograms in further development of
fibrillation (Fig. 1, 2) .
Antagonistic interrelations of the amplitudes of standard leads I
and III in the initial fibrillation are presented in Fig. 2a, b.
Occasionally, several initial complexes can be observed, which remotely /325
resemble ventricular extrasystoles which, in the opinion of some authors
[6], precede the start of fibrillation (Fig. 2, c, d).
3
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d a
repeated defibrillation. There
was a more regular change in the
pattern of the EKG, upon applica-
tion of subthreshold stimuli to
the fibrillating heart. In this
case, the "swinging" phenomenon
Key. e.	 11L	 i sec	 is observed, which consists of a
temporary increase in amplitude of fibrillation, which evidently is con-
nected with an increase in organization of the process, due to synchronous
excitation of elements of the myocardium.
The swinging is of varied (from 0.4 to 1.5 sec) duration, and its
shape most often resembles a damped sinusoid (Fig. 3, a, b), but it can
be irregular (Fig. 3c).
Sometimes, the "swings" are spindle shaped, with the maximum 0.6-
0.8 sec after application of the stimulus (Fig. 3d)• Nearly always, the
closer the pulse to the threshold (value, which causes defibrillation),
the greater the amplitude and duration of the swing (Fig. 4a), but this
is not an unfailing rule.
In series of defibrillations with close enough intervals between
succeeding stimuli, the "swings" progressively become longer, and renewal
of the monorhythm occurs, until the last stimulus "succeeds" in falling
in the large amplitude phase of the oscillation provoked by the preceding
k
This entire part of the
study is of a preliminary na-
ture, and it does not permit
remote conclusions to be drawn
on the genesis of fibrillation
by pulsed electrical stimulation
in the "early" phase of the
cardiac cycle.
Effect of subthreshold
uulses on fibrillation dynamics:Fig. 2. Fibrillation: a, b. examples
of antagonistic relationship of ampli-
tudes of standard leads I and III in
fibrillation-, (experiment 7; a. 41%, b.
80% of threshold current strength); c.
d. examples of fibrillation through
series of extrasystole like complexes
(c. experiment 10, 50% of threshold
current strength; d. experiment 11,
58% of threshold current strength).
1 V	 f
4
pulse (Fig. 4b). Evidently, the
best effect of the paired stimuli
is achieved in those cases, when
the interval between stimuli
varies from 0.2 to 0.3 sec [2] .
This interval guarantees that
another stimulus will fall in
the "swinging" phase caused by
the first stimulus. Recommenda-
tion of a 0.8-1 sec interval
also is not prohibited, if the
;cos; ibility of spindle like
Fig. 3. Diverse "swings" and dynamics 	 "swinging" is kept in mind.
of defibrillation series: a, b. ex-
amples of decreasing "swings" of dif-
ferent duration, regular shape as result	 Dependence of defibrilla-
of subthreshold pulses (a. experiment 3, tion threshold on configuration
80% of threshold current strength; b.
experiment 4, 60% of threshold current 	 of excitation process in rela-
strength); c. irregular shaped "swing"
	 tion to direction of lines of(experiment 2, 80% of threshold current
strength); d. spindle like "swing" (ex- force of defibrillation current.
periment 3, 95% of threshold current
strength); e. example of progressing 	 If a circular theory of fibrilla-
"swing" and emergence from fibrillation tion is maintained, the frequent-
as result of series of pulses of varied observed antagonistic relation-
strength (experiment 6).
ships of the EKG amplitudes in
Key: f. 1 mV	 g. 1 sec	 leads I and III (for dogs, these
leads are orthogonal) can be interpreted as a consequence of a return of
the master cycle, which forms the basis of the path of movement of the
excitation.
The direction of the lines of force of the defibrillation current
in our studies was stable (the electrodes were applied to both sides of
the thoracic cage in the region of the pericardium). Principally, the
configuration of the excitation process with respect to the lines of
force always shifts. If subthreshold stimuli are applied at intervals
known to be sufficient for the "swinging" effect to begin to play some
part, a clear relationship appears,, "between fibrillation amplitude in
the third lead and the effect of this current at the time of passage 6f
the current. Stimuli of the same magnitude, which fall in the phase of
a o
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.
Fig. 4. Effectiveness of current vs. phase of fibrillation process:
a. example of progressing "swing” with approach to threshold and emer-
gence from fibrillation through right ventricular complexes, atrio-
ventricular automatism and return (not shown in figure) to sinus rhythm
through tremor of atrium (experiment 3, 1st pulse 80% of threshold cur-
rent strength, next pulse 90% 3rd pulse threshold); b, c. effectiveness
of pulse vs. phase of process by lead III (experiment 6, equal strength
pulses); d. example of ineffectiveness of 7.2 A pulse in small oscilla-
tion phase and emergence from fibrillation upon application of 6.5 A
pulse in large oscillation phase (experiment 8).
Key: e. 1 mV	 f. 1 sec	 g. a,b,d 1 sec
small, medium and large oscillations, correspondingly, give a rapidly
damped "swing," a persistent "swing" and emergence from fibrillation.
This is seen easily in the recordings presented in Fig. 4b, c.
Fig. 4d demonstrates the absence of an effect of a 7.2 A pulse in
the low amplitude oscillation phase and emergence from fibrillation, as
a result of a 6.5 A stimulus in the large oscillation period.
We could not make a quantitative evaluation of the phenomenon des-
cribed.
Emergence from fibrillation. The patterns of emergence from fibrilla-
tion are extremely diverse.
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Fig. 5• Examples of emergence from fibrillation: a. right ventricular
emergence from fibrillation with rapid appearance of sinus rhythm (ex-
periment 7); b. emergence from fibrillation through left ventricle with
movement of pacemaker to area of atrioventricular node (experiment 1);
c. emergence through left ventricle (experiment 1); d. e. emergence from
fibrillation through "swing" -- left ventricle -- sinus rhythm --
polytopic extrasystole -- nodal rhythm -- sinus rhythm (d. experiment 5;
e. experiment 3); f. example of emergence through two right ventricular
complexes to sinus rhythm, speed of return to normal of ST interval
position, left atrial extrasystole (experiment 10); f. emergence from
fibrillation through atypical complex to sinus rhythm with insertion of
polytopic extrasystoles; g. emergence from fibrillation through "swing"
-- sinus rhythm -- nodal rhythm -- sinus rhythm; h. example of emergence
through paroxysmal tachycardia of left ventricular type.
	
Key: 1. 1 mV
	
J. 1 sec
First, there is emergence through "swinging," which can be inter-
preted successfully as several circular movements of the excitation
front through the myocardium (Fig. 4, c, d; 5, d, e, g).
The primary pacemaker, which conditions the appearance of several
ventricular type complexes, likewise, frequently can appear in the
myocardium of both the right and left ventricles (Fig. 4 a-c; 5 a-c).
/326
As has been noted, the appearance of a monorhythm can precede several
sinusoidal complexes but, in many cases, a single pacemaker pulse arises
immediately after passage of the defibrillation current. Particularly
often, it is not observed in defibrillation with a suprathreshold current.
Here, a progressive (over 4-5 cycles) constriction of the QRS complex
is characteristic (Fig. 5 b, c) .
7
r•
r-
The atrioventrioular pacemaker phase at different levels of this
node usually follows the ventricular automatism phase (Fig. 4, 5). At
s,	 the same time, a displacement of the ST interval to the isolines is
observed. The transition from the nodal rhythm to the sinus rhythm lasts
different lengths of time, from several seconds to 1-2 min, and it can oc-
cur through automatism in the walls of both the left and right atria
(Fig. 4d, f). The possibility of sudden appearance of the atrioventric-
ular and even the sinus rhythm is not excluded (Fig. 5a, f).
Sometimes, emergence from fibrillation occurs through paroxysmal
tachycardia of the ventricular type (Fig. 5h).
A common feature of the majority of emergences from fibrillation
observed is the progressive disturbance of the pacemaker from "bottom
to top" and the speed of return to normal of the ST interval, which is
connected with the elimination of hypoxia of the myocardium after
initial active contractions of the heart.
Quite often, during the nodal and even the sinus rhythm, there have /327
been polytopic extrasystoles and, sometimes, short term flickering
arrhythmia has been noted.
Conclusions
1. The initial dynamics of the fibrillation process in stimulation
of the heart with an electric current in the "early" phase of the cardiac
cycle is not stereotypic.
2. A subthreshold pulse to a fibrillating heart causes the "swing-
ing" phenomenon, which is expressed by an increase in oscillations for
0.4-1.5 sec.
3. In a series of defib rillations, an effect is achieved, at the
time when one of the defibrillation pulses occurs in the "swinging"
phase caused by the preceding pulse.
.	 .	 .
excitation in the myocardium, with respect to the lines of force of the
defibrillation current.
5. The initial dynamics of emergence from fibrillation are ex-
tremely diverse, but there is a general tendency towards progressive
displacement of the pacemaker from the level of the ventricles to the
sinus node, through the phases of atrioventricular and atrial automatism.
g
s`
9
REFERENCES
1. Gurvich, N.L., Fibrill atsi a i defibr , ill atsi a serdtsa
[Fibrillation and Defibrillation of they hoart , Medgiz Press,
Moscow, 1957.
2. Nikolayev, V.G. and M.P. Adamenko, Fiziol. zhurn. AN URSR 1215,
57 (1966).
3. Chebotarev, Ya.P., "Defibrillator," Patent No. 889495/31-16 ,  1967.
4. Ciofu, S., C. B1aja, S. Crivda and C. Vlad, Fiziol. norm si patol.
(14/6, 553	 957)
5. Milter, D. and M. N aclas, Circulat. Res. 15, 199 (1964).
6. Moo, G.K., Pharmac. card. funct. Praha, Or. Med. Puss, 115 (1964).
7. Veghely, P;.V. and A. Kemeny, Acta physiol. Acad. sci. Hung. 8/3-4,
429 (19'55)•
t
10


Initial dynamics of the EKG during an electrical defibrillation of the heart

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