TRANSTHORACIC DEFIBRILLATION OF 100 KG CALVES
`WITH BIDIRECTIONAL TRUNCATED EXPONENTIAL SHOCKS
`
`J. C. Schuder, W. C. McDaniel, and H. Stoeckle
`
`Jones and
`High-intensity electric field stimulation causes periods of arrest in cultured myocardial cells.
`Jones have shown that the duration of arrest caused by stimulation with a unidirectional rectangular pulse may be
`reduced by the addition of a low-amplitude reverse polarity pulse to the waveform1 and that the ratio of field in—
`tensity required to produce a given duration of arrest to that needed for cellular excitation tends to be larger for
`damped sinusoidal waveforms having a reverse current component than for unidirectional waveformsz. These
`findings suggest that the inclusion of a reverse current component in a defibrillatory waveform might reduce post—
`shock arrhythmias without having an adverse effect upon the level of successful defibrillation. On the contrary,
`Niebauer and colleagues have compared the efficacy and safety of unidirectional and bidirectional low-droop
`trapezoidal (nearly rectangular) waveforms in defibrillating isolated perfused canine hearts and concluded that
`symmetrical bidirectional waveforms offer no significant efficacy or safety advantage over unidirectional pulsesa.
`A comparison of the results of studies by our group of the effectiveness of one-cycle, symmetrical, bi—
`directional, rectangular wave shocks4, one—cycle, asymmetrical, bidirectional, rectangular wave shocks5, and
`unidirectional rectangular wave shocks6 in the transthoracic defibrillation of 100 kg calves indicates that the most
`successful of the symmetrical and asymmetrical bidirectional waveforms are more successful and require less
`energy than the most successful unidirectional waveform.
`While rectangular wave shocks are very convenient for defibrillation research because the various parame—
`ters can be so easily and unambiguously specified, they are technologically difficult to generate in clinical sized
`defibrillators.
`In the present paper, we describe a study of the effectiveness of a category of symmetrical and
`asymmetrical truncated exponential waveforms, which can be implemented in clinical sized apparatus,
`in the
`transthoracic defibrillation of 90—110 kg calves.
`
`METHOIE
`
`Waveform Selection. A generalized representation of the category of waveforms considered in this paper
`is shown in Figure 1 . The leading and lagging portions of the waveform have identical time constants, r , and
`identical durations, T. The amplitude of the initial current of the leading half-cycle of the waveform, I, is 70 amp
`in all cases. We define the fractional undershoot associated with this category of waveforms as
`
`Ilh/l
`=
`ll3/|]|
`=
`f
`where the vertical lines denote absolute value.
`The energy in joules delivered by a waveform of current of the type shown in Figure 1 is given by
`2
`2
`2
`2
`- IZ)+(|3 '
`|~)]
`
`Equationl
`
`Equation2
`
`2 |
`
`U
`
`= 0.5RT [(I1
`
`which, together with Equation 1, yields
`
`u
`
`= 0.5 R 1 (I12 -122) (1+ f2)
`
`where R is the chest resistance in ohms, T is in seconds, and the 1's are in amperes.
`Solving Equation 3 for 1 gives
`
`Furthermore,
`
`1
`
`= ng—T
`R(Il -|2) (1+f)
`
`T
`
`=
`
`1 1n (ll/'2)
`
`Equation3
`
`Equation4
`
`Equation5
`
`From Equations 4 and 5, one can determine the time constant and duration required to deliver a specified energy
`level, U. to a chest having a given resistance, R, with a waveform having specified values of 11, 12, and f.
`
`From the Departments of Surgery and Child Health, University of Missouri, Columbia, Missouri.
`Supported by grant HL-l80h0 from the National Heart, Lung, and Blood Institute and a grant
`from Physio
`Control Corporation.
`
`Vol.XXX Trans Am Soc Artif Intern Organs WM
`
`520
`
`1
`
`L|FECOR427-1010
`
`1
`
`LIFECOR427-1010
`
`

`

`Schuder et a1. Transthoracic defibrillation
`
`The 11, 12, f. and U values used in the 8 waveforms evaluated in the present study were selected so that
`the results for each specific waveform could be compared easily with results obtained previously with bidirec—
`tional rectangular waveforms“,5 having amplitude. fractional undershoot, and delivered energy values of I1, f.
`U and 12, f, U-
`the rectangular waveform shown in Figure 2b has a leading half-cycle amplitude equal to
`As an example,
`the initial amplitude of the leading half—cycle of the exponential waveform sketched in Figure 2a:
`the waveform
`shown in Figure 20 has a leading half-cycle amplitude equal to the final amplitude of the leading half—cycle of the
`waveform shown in Figure 2a. The 3 waveforms in Figure 2 have identical undershoots and deliver the same
`energy.
`
`In this table, the dura-
`The specifications for the 8 waveforms which were evaluated are shown in Table I.
`tions mbulated in the fourth and eighth columns are calculated from Equations 4 and 5.
`In some cases, the levels
`of current listed in columns 6 and 7 are experimental target values which have been rounded to the nearest integer
`from their theoretical noninteger values.
`
`TABLE 1.
`
`DESCRIPTION OF BIDIRECTIONAL EXPONENTIAL WAVEFORMS
`
`Leading Half-Cycle
`Current
`Duration
`
`Fractional
`Undershoot
`
`Lagging Half-Cycle
`Current
`Duration
`
`Waveform
`No.
`
`1
`2
`3
`1+
`5
`6
`7
`8
`
`amp
`
`I
`
`1
`
`70
`70
`70
`70
`70
`70
`70
`70
`
`|
`
`2
`
`35
`35
`50
`50
`35
`35
`50
`50
`
`T
`msec
`
`3.77
`3.77
`2.80
`2.80
`7.511
`7.511
`5.61
`5.61
`
`f
`
`1/2
`l
`1/2
`l
`l/h
`1/2
`1/11
`1/2
`
`—|
`
`3
`
`-|h
`amp
`
`35
`70
`35
`70
`18
`35
`18
`35
`
`18
`35
`25
`50
`9
`18
`13
`25
`
`T
`msec
`
`3.77
`3.77
`2.80
`2.80
`7.511
`7.5%
`5.61
`5.61
`
`Delivered
`Energy
`
`.
`
`U
`oules
`
`250
`1100
`250
`1100
`MS
`500
`l125
`500
`
`Delivered energy values are based upon an assumed representative chest resistance of 20 ohms.
`
`Equipment. A bidirectional waveform research defibrillator, which has been described elsewhere7, was
`used to supply a low current shock for inducing fibrillation, the bidirectional exponential waveform being evaluated
`(or a screening bidirectional rectangular wave shock), and an effective follow—up shock to salvage the animal in
`case the waveform being evaluated did not yield defibrillation. Current and voltage waveforms of the shock being
`evaluated were displayed on a Tektronix model 5113 dual-beam storage oscilloscope. The chest resistance of the
`bidirectional exponential waveforms was calculated as the arithmetic mean of the voltage to current ratios evalu—
`ated near the midpoints of the 2 half-cycles. Lead 1] electrocardiograms were displayed on an oscilloscope and
`recorded with an electrocardiograph for later evaluation.
`Procedure. Before being entered into our detailed study, calves were screened by requiring that success-
`ful first—shock defibrillation be achieved in at least 19 out of 20 defibrillation attempts with a bidirectional rec—
`tangular wave shock having a leading half -cycle amplitude of 50 amperes, a leading half-cycle duration of 8 msec,
`a fractional undershoot of 1/2, and a nominal delivered energy of 500 joules. Fourteen calves passed the screening
`requirement and were used in our detailed study: one calf failed the screening test.
`The procedure used in our detailed study was almost identical to that previously describede. Briefly, the
`calves were anesthetized with 110 mg/kg glycerly guaiacolate and 4. 4 mg/kg thiopental sodium injected intrave—
`nously. intubated, and maintained with methoxyflurane in 50% N20 and 50% 02. Fibrillation was induced with a
`low current transthoracic shock and, after 30 secs,
`the shock being evaluated was applied.
`If defibrillation was
`achieved on the first trial, it was recorded as a success and the electrocardiogram recorded for 2-1/2 mins.
`Otherwise, the shock was recorded as a failure and a shock of known high effectiveness used to defibrillate the
`animal. The procedure was repeated with not less than 5 mins between the start of successive episodes. Each
`specific waveform was evaluated on the basis of 120 episodes in 90—110 kg calves with no animal being involved in
`more than 20 episodes in a given session or more than 20 episodes with a single waveform. Our detailed study
`encompassed a total of 120 x 8 = 960 fibrillation-defibrillation episodes.
`
`RESULTS
`
`The results are summarized in Tables 11 and III. The experimental chest resistance values tabulated in
`Table II indicate a limited variation in chest resistance for the shocks evaluated and serve to justify the use of 20
`ohms as a representative value of chest resistance.
`
`521
`
`2
`
`

`

`Schuder et a1. Transthoracic defibrillation
`
`TABLE II.
`
`BODY WEIGHT AND CHEST RESISTANCE 0F CALVES
`
`Waveform
`No.
`
`Body Weight
`kg
`
`Chest Resistance
`ohms
`
`1
`2
`3
`1;
`S
`6
`7
`8
`
`103:6
`10215
`102 t 3
`102111
`100:3
`10112
`101 ill
`102 i 11
`
`20.3i1.3
`20.31- 1.3
`19.9 1 2.0
`19.71: 1.7
`153.512.]
`19.3i2.2
`19312.1
`18.6 i 1.1+
`
`Entries for body weight and chest resistance are
`means 1 SD and based upon 120 episodes.
`
`TABLE III.
`
`RESULTS OF BIDIRECTIONAL WAVEFORM SHOCKS
`
`Waveform
`No.
`
`Successful
`Defibrillations
`No.
`14
`
`Time Required for Appearance
`of First Ventricular Complex
`secs
`
`Time Required To Return
`To Normal Sinus Rhythm
`secs
`
`1
`2
`3
`11
`5
`6
`7
`8
`
`108
`113
`109
`117
`101-1
`115
`119
`120
`
`90
`9‘1
`91
`98
`87
`96
`99
`100
`
`3.0 i 1.0
`6.1 i 3.8
`3.1 $1.4
`5.2 1 3.9
`8.3 i 8.3
`6.1i 5.0
`6.2 i 11.7
`9.7 i 9.6
`
`6.11
`9.11 :1:
`26.2 i 15.5
`12.7 i
`9.11
`28.11 117.14
`17.7 i 10.7
`16.7 1111.1
`9.8 1 SJ;
`21.8 i 17.0
`
`Entries for the appearance of the first ventricular complex and for the return of normal
`sinus rhythm are means 1: SD and based upon the indicated number of successful defibrillations.
`
`In Figure 3 is plotted percent success versus delivered energy for the 4 exponential waveforms in which
`the initial half—cycle current sweeps from 70 to 35 amperes.
`In Figure 4 are plotted the corresponding data for the
`4 waveforms in which the initial half—cycle current sweeps from 70 to 50 amperes. Two short line segments are
`associated with each of the 8 datum points. These segments represent the percent success observed previously
`for bidirectional rectangular wave shocks4’ 5 having the fractional undershoot of the exponential waveform and
`leading half-cycle current amplitudes equal to the initial and final values respectively of the leading half—cycle of
`the exponential waveform.
`In calves, there is often an appreciable period of standstill or of only p—waves in the electrocardiogram
`following a defibrillatory shock. Data from the fourth column of Table III, along with corresponding data from
`earlier studies with bidirectional rectangular waveforms4v 5 are plotted in Figures 5 and 6. Similar graphs relat-
`ing the time required for a return of normal sinus rhythm in the electrocardiogram could be constructed from
`data in the final column of Table III and our earlier studies4'5.
`
`DISCUSSION
`
`The predominant tendency for each of the percent success levels of the bidirectional exponential wave shocks
`under evaluation to fall within, on. or very close to the boundaries defined by the 2 associated bidirectional rec—
`tangular wave shocks, as illustrated in Figures 3 and 4, supports the proposition that such shocks are well behaved
`and that their performance is approximately predictable from that of the associated bidirectional rectangular wave
`shocks. This proposition is further strengthened by the data concerning the shock induced electrocardiographic
`disturbances as shown graphically in Figures 5 and 6 and by a comparison of the data in column 5 of Table III with
`corresponding rectangular wave data developed earlier4’ 5. The most successful of the bidirectional exponential
`waveforms evaluated (100%) was equivalent to the most successful bidirectional rectangular waveform5 (100%) and
`superior to the most successful unidirectional rectangular6 (93%) and unidirectional truncated exponential8 (94%)
`waveforms in achieving ventricular defibrillation in our 100 kg calves.
`Although there are inherent uncertainties in trying to extrapolate expierimental experience from the 100 kg
`calf to the human, we interpret the results of this and our earlier studies47 ’8 as warranting clinical trials of hi—
`directional truncated exponential wave defibrillators.
`
`522
`
`3
`
`

`

`Schuder et a1. Transthoracic defibrillation
`
`REFERENCES
`
`Jones JL, Jones RE. Decreased arrhythmias in cultured myocardial cells following high intensity
`electric field stimulation with biphasic rectangular waveforms.
`Fed Proc 42:lllh, 1983.
`Jones JL, Jones RE.
`Improved defibrillator waveform safety factor with biphasic waveforms.
`Physiol 2h5:H60, 1983.
`Niebauer MJ, Babbs CF, Geddes LA, Bourland JD. Efficacy and safety of the reciprocal pulse de-
`fibrillator current waveform. Med Biol Eng Comput 22:28, 198h.
`Schuder JC, Gold JH, Stoeckle H, McDaniel WC, Cheung KN. Transthoracic ventricular defibrillation
`in the loo kg calf with symmetrical one-cycle bidirectional
`rectangular wave stimuli.
`IEEE Trans
`Biomed Eng BME-30:4]S, 1983.
`Schuder JC, McDaniel WC, Stoeckle H. Defibrillation of lOO kg calves with asymmetrical, bidirec-
`tional,
`rectangular pulses. Cardiovasc Res
`(in press).
`JM. Transthoracic ventricular
`Gold JH, Schuder JC, Stoeckle H, Granberg TA, Hamdani SZ, Rychlewski
`defibrillation in the loo kg calf with unidirectional
`rectangular pulses. Circulation 56:7“5,
`1977.
`Schuder JC, Gold JH, McDaniel NC. Ultrahigh-energy hydrogen thyratron/SCR bidirectional waveform
`defibrillator. Med Biol Eng Comput 20:h19, 1982.
`Schuder JC, Gold JH, Stoeckle H, Granberg TA, Dettmer JC, Larwill MH. Transthoracic ventricular
`defibrillation in the loo kg calf with untruncated and truncated exponential stimuli.
`IEEE Trans
`Biomed Eng ENE-27:37,
`l980.
`
`Am J
`
`70A
`
`b
`ZII.I
`KK
`3
`0
`
`was
`
`1
`
`._
`
`4
`
`'12
`
`Figure l. Generalized representation of category of
`bidirectional
`truncated exponential waveforms studied.
`
`TIME
`
`TIME
`
`III/2
`
`,_
`2
`II]
`x
`(a) K
`3
`0
`
`35A
`
`T'3.77ml
`
`
`
`I;m
`
`xm
`
`0
`3
`
`Pz
`
`2
`x
`
`30
`
`
`
`
`(b)
`
`(c)
`
`TIME
`-I15
`III)
`
`
`40
`
`IOO
`
`90
`
`4
`a 80
`3
`3
`g 70
`m
`5
`3 ‘0
`u
`1
`a so
`
`III/2
`I
`
`in mm
`l
`I
`
`mm
`1
`70A
`4.6
`
`OEXPONENTIAL
`‘-RECTANGULAR
`
`Figure 2. Waveforms which have the same
`value of undershoot and which deliver the
`same energy to a given load.
`(a) First
`bidirectional
`truncated exponential wave-
`form evaluated.
`(b) Bidirectional
`rec-
`tangular waveform having current amplitude
`of leading half-cycle equal
`to the initial
`current value of leading half-cycle of ex-
`ponential waveform.
`(c) Bidirectional
`u
`.
`rectangular waveform having current ampli-
`tude of leading half-cycle equal
`to flnal
`value of current
`in leading half-cycle of
`exponential waveform.
`
`35A
`
`c 250
`450
`400
`350
`300
`NOMINAL DELIVERED ENERGY IN JOULES
`
`500
`
`Figure 3. Percent success of ventricular defibrilla-
`tion related to fractional undershoot and delivered
`energy for bidirectional
`truncated exponential wave-
`forms in which leading half-cycle current sweeps from
`70 to 35 amp and for bidirectional
`rectangular wave-
`forms in which the leading half-cycle is either 70 or
`35 amps.
`
`523
`
`4
`
`

`

`Schuder et al. Transthoracic defibrillation
`
`I00
`90
`
`.l
`3 soa)In
`'3
`g 70
`m
`
`'2' soUU
`5n. 50
`
`40
`
`t;I/2
`L/70A
`\50A
`
`Iii/4
`III
`l
`5OA—‘* 3/50A
`J
`“”1 ”~{13‘
`10A
`
`III/2
`t
`50A
`.{IgA
`
`o EXPONENTIAL
`— RECTANGULAR
`
`
`
`‘50
`400
`350
`300
`250
`NOMINAL DELIVERED ENERGY IN JOULES
`
`500
`
`K:
`
`ma 3
`
`’- 0
`
`:5
`0x a
`iufl
`g;
`:8 6
`Eu:
`:5 4
`1::
`8:-
`“I- 22
`In»
`;:>
`
`0
`
`Figure 5. Mean time required for appear-
`ance of first ventricular complex follow-
`ing a defibrillatory shock related to
`fractional undershoot and delivered
`energy for bidirectional
`truncated expo-
`nential waveforms in which leading half-
`cycle current sweeps from 70 to 35 amps
`and For bidirectional
`rectangular wave-
`forms in which the leading half-cycle is
`either 70 or 35 amps.
`
`III/2
`I
`
`fll
`l
`
`III/4
`i
`
`{II/2
`I
`
`Figure A. Percent success of ventricular
`defibrillation related to fractional under-
`shoot and delivered energy for bidirec-
`tional
`truncated exponential waveforms in
`which leading half-cycle current sweeps
`from 70 to 50 amps and for bidirectional
`rectangular waveforms
`in which the leading
`half-cycle is either 70 or 50 amps.
`
`f-I/Z
`l
`
`le III/4
`
`III/2
`
`O EXPONENTIAL
`— RECTANGULAR
`
`{70A
`35A
`:16
`
`
`
`250
`300
`350
`400
`4 50
`NOMINAL DELIVERED ENERGY IN JOULES
`
`500
`
`8 l2
`I—g
`g0
`E3 IO
`'65
`w)< a
`33
`(0.
`oz! 6
`Q8
`:5
`g 4
`“an"-E
`“Jr
`a: 2
`r->
`l
`
`O
`
`
`
`O EXPONENTIAL
`- RECTANGULAR
`
`50A
`
`70A
`
`Figure 6. Mean time required For appear-
`ance of first ventricular complex follow-
`ing a defibrillatory shock related to
`Fractional undershoot and delivered
`energy for bidirectional
`truncated expo-
`nential waveforms in which leading half-
`cycle current sweeps from 70 to 50 amps
`and for bidirectional
`rectangular wave—
`forms
`in which the leading half-cycle is
`either 70 or 50 amps.
`
`
`
`
`250
`300
`350
`400
`450
`500
`NOMINAL DELIVERED ENERGY IN JOULES
`
`524
`
`5
`
`

`

`DISCUSSION OF MANUSCRIPT #103
`
`DR. DeVRIES: What was the efficacy of the defibrillator after the time when you Fibrillated?
`How quickly after you actually got fibrillation did you actually defibrillate?
`DR. SCHUDER:
`For both the rectangular waves and the exponential waves,
`attempted at 30 secs (1 l sec) after the induction of defibrillation.
`
`the defibrillation was
`
`'1‘
`
`525
`
`6
`
`