THE TREATMENT OF COMPLETE HEART BLOCK WITH
AN IMPLANTED, CONTROLLABLE PACEMAKER

ADRIAN KANTROWITZ, M.D., RICHARD COHEN, M.D., Brooklyn, New York,
HEINZ RAILLARD, M.S.E.E., JOHN SCHMIDT, B.S.E.E., Syracuse, New York, and
DANIEL S. FELDMAN, M.D., Brooklyn, New York

THE INCIDENCE of atrioventricular dissocia-
tion and Stokes-Adams seizures has been
variously estimated. Rowe and White re-
viewed 160,000 electrocardiograms taken
at the Massachusetts General Hospital from
1925 to 1955 and discovered 350 patients
who showed complete atrioventricular dis-
sociation. Penton, Miller, and Levine re-
ported 251 cases of complete heart block
during a 42 year period. In Rowe’s series,
Stokes-Adams syndrome occurred in 30 per
cent of the patients, whereas Penton re-
ported an incidence of 61 per cent. At
Maimonides Hospital of Brooklyn, 44 cases
of Stokes-Adams syndrome were seen dur-
ing the 5 year period 1956 through 1960.

By far the most common cause of com-
plete heart block in the older age group is
coronary artery disease. There is an in-
creasing number of patients who have per-
manent heart block subsequent to open
heart surgery.

Since 1952 when Zoll first suggested the
use of an external electric stimulator in the
treatment of intractable, complete heart
block, there has been increasing interest in
this therapeutic approach. Weirich, Gott,
and Lillehei described a method of implant-
ing electrodes in the myocardium and
stimulating the hearts of patients suffering
from surgically induced heart block. Glenn
and his associates reported a method of
implanting subcutaneously a tuned circuit
driven from the outside by a radio-frequency

From the Departments of Surgery and Neurology, Maimon-
ides Hospital, Brooklyn, and State University of New York Col-
lege of Medicine, New York, and the Electronics Laboratory,
General Electric Company, Syracuse.

This work was supported by U. S. Public Health Service
Grants Nos. H-5977 and H-6510.

link. A pacemaker, similar in principle,
has been used by Senning. Furman and
Robinson reported a method of stimulating
patients with complete heart block by pass-
ing a catheter into the right ventricular
cavity through an accessible vein. In 1959,
Hunter and colleagues described a bipolar
myocardial electrode. In 1960, Chardack
and associates (1) reported the treatment
of 3 patients with a totally implanted elec-
tronic circuit. A subsequent report by these
investigators (2) evaluated their experience
with 15 patients.

In a joint effort, the Surgical Research
Division of Maimonides Hospital and the
Electronics Laboratory of the General
Electric Company have developed a totally
implantable pacemaker with a fixed mini-
mum rate, as well as the capability of re-
sponding to an optional external control.

DESIGN OF THE PACEMAKER

The basic circuit operation consists of a
pulse oscillator requiring a small number
of components as shown in Figure 1. It
employs a PNPN or complementary transis-
tor configuration exhibiting a negative
resistance across the terminal of resistance
R17. The theory of such a circuit has been
described previously by Suran.

The circuit operation may be summarized
as follows: When the capacitor C is com-
pletely discharged, the transistor configura-
tion becomes regenerative and acts as a
closed switch. The capacitor C’ is charged
from the batteries £7 and E2 with a time
constant given by the product of C and the
sum of the load resistance, i.e., the heart,

Reprint from SURGERY, Gynecology G Obstetrics, October, 1962, Vol. 115, 415-420

Copyright, 1962, by The Franklin H. Martin Memorial Foundation
2 Surgery, Gynecology ez Obstetrics - October 1962

T
I we
J 2

HEART SR Re 3f
4

 

 

 

— 41+ +=1i[-+
E\ E2

Fic. 1. Circuit diagram of implantable pacemaker.

transistor saturation resistance, and R3. The
corresponding current surge constitutes the
impulse delivered to the heart. When the
capacitor voltage reaches the battery voltage
(E1 + £2), the switch turns off and the
transistors cease to conduct current. The
capacitor C now discharges through R7 and
the load, until Cis almost empty, whereupon
a new current surge generates another im-
pulse.

The performance of 2 versions of the
circuit, one employing 4 and the other 5
mercury cells at 1.4 volts each, is sum-
marized in ‘Table I.

On the basis of the rated capacity of the
batteries the implantable pacemaker should
operate for at least 5 years without battery
replacement. A decrease in battery voltage
will, however, result in a change in pulse
rate and may, therefore, readily be detected.

TABLE I.
Circuit A, Circuit B,
4 batieries 5 batteries
Peak pulse power, milliwatts. . 32 56
Peak output voltage, volts. ... 2.8 3.9
Average current drain, micro-
AMPEFES... 6... cece eee eee 14 25
Average power drain, micro-
wattS. 6... ee eee ee 82 184
Energy delivered to the load,
microjoules.............. 23 64
Power efficiency, per cent.... 30 30
Frequency, per minute....... 62 62
Pulse time constant, milli-
seconds. ...........0006. 1.8 2

Frequency stability, per cent. . 6 between 0 and 60°C.
Expected battery life, hours—

1,000 MA hr. rated ca-

PACIY eee cece eevee 71,000 40,000
Packaged volume, including
batteries, cubic inches..... 2.4 4

The entire implantable pacemaker circuit
was potted in epoxy resin and is shown in
Figure 2, together with the external control
circuit. The circuit is then hermetically
sealed in a teflon case. The load terminals
are connected to a pair of teflon-coated, 24
inch long cardiac electrodes. Each electrode
consists of 49 braided strands of 1.5 mil
annealed No. 316 stainless steel wire. An
external control circuit capable of trans-
mitting a suitable trigger pulse to the
internal pacemaker has also been developed.
This circuit employs a PNPN complemen-
tary transistor configuration connected in a
relaxation oscillator mode similar to the
implantable circuit described before. A
sharp current pulse is generated which
energizes an induction coil and thus triggers
the internal circuit magnetically. ‘The mini-
mum and maximum rate of the external
control circuit is adjusted by selecting 2
resistors. With a variable resistance, con-
tinuous external rate control between the
limits of 60 and 120 is then possible. The
flat induction coil has a diameter of 3.5
inches and is connected to the circuit by a
15 inch cable. This arrangement permits
the patient to attach the coil to the skin
close to the internal pacemaker. ‘The area
of the coil is considerably larger than that
of the internal unit. This discrepancy in size
allows the 2 units to be placed up to 1.5
inch off center.

In connection with the development of
the pacemaker circuit, measurements were
made on 3 patients to determine the nature
and quantity of the required electrical
stimulation. Stimulation was achieved
through a pair of electrodes implanted in
the myocardium approximately 1 centi-
meter apart. The teflon-coated electrodes
were brought out of the body for external
stimulation. At the time these measure-
ments were made the patients had been
stimulated for 6 months. Although the
magnitude of the required stimulation in-
creased during the initial period after im-
plantation of the electrodes, the critical
threshold levelled off at a constant value.
Kantrowitz ef al.: PACEMAKER IN TREATMENT OF COMPLETE HEART BLOCK 3

An electrocardiograph was used as a moni-
tor to indicate whether or not stimulation
was achieved. For a number of pulse widths,
ranging from 0.3 to 7 milliseconds, the cur-
rent and voltage waveforms corresponding
to the minimum stimulation were photo-
graphed. A study of the waveforms permits
a determination of the approximate im-
pedance of the load, i.e., the heart, and
this was found to consist of a series combina-
tion of 300 ohms and 20 microfarad capaci-
tance. The resulting waveforms may then
be analyzed in detail in a graphic procedure.
The average current, the root-mean-square
current, the charge, and the energy of each
pulse were determined.

A comparison of the various quantities as
a function of pulse width indicates that both
current and charge are strongly dependent
on pulse width, whereas energy is fairly
constant. The data indicate that the nature
of the threshold has the dimension of a
constant energy level of approximately 15
microjoules per pulse when measured over
a fairly wide range of pulse widths. Our
findings of the energy requirements of 15
microjoules to stimulate the human heart
after 6 months of stimulation through im-
planted electrodes agree with the findings
of Chardack and other workers. It would
appear then that this is close to the upper
limits of energy required after long term
stimulation. Since our unit delivers 64 joules
there is a safety factor of close to 400 per
cent.

OPERATIVE TECHNIQUE

The operative procedure is carried out
under general anesthesia with an endo-
tracheal tube in place. All patients are
brought to the operating room under elec-
tronic control of an external pacemaker with
a cardiac catheter electrode passed through
the right saphenous vein. Electrocardio-
graphic leads are then attached to the arms
and legs, and the continuous electrocardio-
gram is displayed on an oscilloscope. The
patient is placed in the dorsal recumbent
position.

 

Fic. 2. Five battery implantable pacemaker. Optional
external control circuit is on the right.

‘Two incisions are made. One is a trans-
verse incision of 5 centimeters just to the
left of the umbilicus and deepened to the
anterior rectus sheath. The second is a left
submammary incision. The pleural cavity
is entered through the fourth intercostal
space. The pericardium is opened to expose
the left ventricle. A subcutaneous tunnel
is then made from the chest incision to the
abdominal incision. The electrodes are
individually brought through the tunnel
into the chest incision and through the
pericardium. Each electrode is sutured into
the myocardium, fixing the teflon in the
depths of the muscles. The bared electrode
is then passed back through the myocardium
to emerge near the entrance of the teflon.
The second electrode is implanted in the
same fashion as the first, 1 centimeter away.
The pericardium is closed with interrupted
silk sutures. The chest is closed in layers.
The pacemaker is then placed into the
subcutaneous pocket. Sutures are taken
through the teflon coating to attach the
pacemaker firmly to the anterior rectus
sheath. The subcutaneous tissue and skin
4 Surgery, Gynecology et Obstetrics - October 1962

     
  

PULMRNARY, 4
ARTERY : LRET AUAICOLAR
APPENDAGE

108
ANTE RAO Leer
VENTRICLE
VESoEL

   

foser.
YENTRCTE
eLECTROGES

Fic. 3. Drawing of heart with electrodes in left ven-
tricular myocardium.

are closed. The external conirol unit is
taped on the abdomen and set between
80 and 90 per minute.

RESULTS

In our series of 14 patients, 13 had
coronary artery disease and 1 patient was
believed to have had a viral myocarditis.
The indication for implanting the pace-
maker in 13 of these patients was multiple
Stokes-Adams seizures which did not re-
spond to vigorous medical therapy. In 1
patient the main indication for implanting
the pacemaker was congestive heart failure
secondary to intractable bradycardia. Im-
plantation of the pacemaker greatly re-
lieved the congestive failure. In 10 patients
the mechanism for the Stokes-Adams sei-
zures was ventricular asystole, whereas in 2
patients paroxysmal ventricular tachycardia
was the mechanism. One patient had elec-
trocardiographic evidence of varying asys-
tole and ventricular tachycardia.

In the 14 patients in whom this pace-
maker has been implanted, there has been
no failure of the pacemakers. In Patient 1,
3 months after operation one of the elec-
trodes pulled out of the myocardium and

also frayed at the exit from the pacemaker.
Each of these technical problems was cor-
rected, and the patient has been asympto-
matic for 6 months. Patient 2 died on the
fourth postoperative day from acute pul-
monary edema. Autopsy revealed diffuse
coronary artery disease but no evidence
of acute infarction. In Patient 5 one of the
electrodes broke because of a sharp flexion.
This problem was solved by implanting a
new pacemaker and welding the new elec-
trodes to the old ones going to the heart
which avoided another thoracotomy. In
Patient 7 congestive failure developed 4
weeks after operation. This condition re-
sponded to medical therapy and increasing
the heart rate with the external circuit. Pa-
tient 11 died on the third postoperative day.
This patient, in addition to multiple seizures
had diabetic retinopathy, advanced gener-
alized arteriosclerosis, hypertension, and
congestive heart failure. Autopsy revealed
acute myocardial infarction with advanced
coronary sclerosis and advanced arterio-
lonephrosclerosis. In 12 patients the pulse
rate has remained under continuous control
since implantation of the pacemaker.

DISCUSSION

‘The implantable, self-powered pacemaker
offers a number of advantages over other
types of electronic pacemakers. It elimi-
nates the problems of skin excoriation, in-
fection, and accidental dislodgment of the
electrodes of the pacemaker. The electrical
energy requirement of an internal pace-
maker is a fraction of that required by an
external pacemaker. With the internal pace-
maker, the patient is not concerned with
its control.

The implanted pacemaker has an in-
trinsic rhythm which is set between 60 and
65 pulses per minute. This rate represents a
compromise between a lower rate which
would yield longer battery life and a higher
rate in which cardiac output would be in-
creased with a diminished stroke volume.

The unit measures approximately 2 by 4
by 6 centimeters. None of the patients has
Kantrowitz ef al.: PACEMAKER IN TREATMENT OF COMPLETE HEART BLOCK 5

complained of any discomfort from the sub-
cutaneously implanted pacemaker.

The 9 components were chosen for their
compatibility and function well below their
rated specifications. Silicon transistors were
used rather than germanium, because of
their greater reliability. The assembled units
were extensively tested in the laboratory
by the engineering group, at times trying
the patience of the clinical group.

The entire unit has been embedded in
teflon. Harrison and associates have shown
that teflon is chemically inert and less wet-
table and incites less tissue reaction than
any of the plastics thus far studied. Methods
for resealing the teflon in the operating
room have been designed should this be
necessary to replace the pacemaker or an
electrode. This procedure has been carried
out successfully in 2 of our cases.

The problem of electrode breakage in
Patients 1 and 5 is similar to that reported
by other workers. Mechanical problems
with the electrodes were re-examined by the
Electronics Laboratory of the General
Electric Company. It is known that wires
implanted in the myocardium are subjected
to a certain amount of cyclical stress. A
technique was devised to reduce their stress.
The electrodes are passed into the myo-
cardium fixing the teflon in the depths of
muscle. The bared electrode is then passed
back through the myocardium to emerge
near the entrance of the teflon. In addition,
the exit point of the pacemaker was re-
designed so that the electrode is not per-
mitted any point of sharp flexion close to
the pacemaker.

The external control circuit is an optional,
transistorized device that the patient wears
when it seems desirable for him to have an
increased pulse rate. We have found this
to be a distinct advantage in several situa-
tions. All 14 patients were sent from the
operating room to the recovery room with
the external control circuit setting the im-
planted pacemaker at a rate between 80 and
100 beats per minute. It is also desirable
to increase the pulse rate during periods

 

Fic. 4. Illustration of incisions and sites of implanta-
tion of pacemaker and electrodes.

of stress such as infection, blood loss, and
exercise. Younger patients have found it
desirable to have the ability to increase
their pulse rate during vigorous exertion.

Finally, the functioning of the implanted
pacemaker can be studied by using the ex-
ternal control circuit as a test instrument.
It has been shown that failure of the in-
ternal pacemaker to follow the external
control circuit at a rate of 120 indicates
increasing myocardial threshold or decreas-
ing energy levels being delivered by the
internal pacemaker.

The clinical use of implanted pacemakers
has an additional significance. It represents
a departure from the conventional role of
medical electronics in measuring and gath-
ering data. With engineering achievements
such as microminiaturization and circuits
requiring low power, an important new
role for electronic devices can be foreseen.
We have used the word “bioelectronics”’ to
describe this integrated, long term elec-
tronic control of various impaired physi-
6 Surgery, Gynecology ¢ Obstetrics + October 1962

ologic systems. We (7) and others have
reported explorations in this cross-discipline
which holds exciting promise for the future.

SUMMARY

1. An implantable, transistorized, self-
powered, teflon-encapsulated, electronic cir-
cuit capable of serving as an artificial pace-
maker for patients suffering from intractable
Stokes-Adams seizures is described.

2. Clinical experience with 14 patients
has been encouraging. One patient died 4
days after operation from acute pulmonary
edema, and autopsy revealed extensive
coronary artery disease. Another patient
died 3 days after operation, and autopsy re-
vealed acute myocardial infarction and ad-
vanced arteriolonephrosclerosis. Two pa-
tients suffered from electrode breakage.
This failure of the electrodes was corrected
by modified techniques.

3. The advantages of this unit are its
high reliability, small size, and low power
drain. It is responsive to an optional ex-
ternal circuit which may be used when
higher rates are desired.

REFERENCES

1, Cuarpack, W. M., Gace, A. A., and GREATBATCH,
W. A transistorized, self-contained, implantable
pacemaker for the long term correction of complete
heart block. Surgery, 1960, 48: 643.

2.

Idem. Experimental observations and clinical ex-
periences with the correction of complete heart
block by an implantable self-contained pacemaker.
Tr. Am. Soc. Artificial Int. Organs, 1961, 7: 286.

. Furman, S., and Ropinson, G. The use of an extra-

6.

10.

11.

12,

13,

cardiac pacemaker in the correction of total heart
block. Surgical Forum; Clinical Congress 1958.
Vol. IX, p. 245. Chicago: American College of Sur-
geons, 1959.

GLENN, W. W.L., Mauro, A., Lonco, E., LAVIETES,
P. H., and Mackay, F. Remote stimulation of the
heart by radio frequency transmission. N. England
J. M., 1959, 261: 948.

Harrison, J. H., Swanson, D. S., and Linco, A.
F. A comparison of the tissue reactions to plastic
materials. Arch. Surg., 1957, 74: 139.

Hunter, 8. W., Rory, N. A., BERNANDEZ, O., and
Nose, J. L. A bipolar myocardial electrode for
complete heart block. Lancet, Lond., 1959, 79: 606.
KantrowitTz, A., and McKinnon, W. The experi-
mental use of the diaphragm as an auxiliary myo-
cardium, Surgical Forum; Clinical Congress 1958.
Vol. TX, p. 266. Chicago: American College of
Surgeons, 1959.

Penton, G. B., Miter, H., and Levine, S. A.
Some clinical features of complete heart block.
Circulation, 1958, 13: 801.

Rowe, J. C., and Wurre, P. D. Complete heart
block; a follow-up study. Ann. Int. M., 1958,
49: 260.

SENNING, A, Discussion of physiologic P-wave cardiac
stimulation by Sam E. Stephenson, Jr.. W. H.
Edward, P. C. Jolly, and H. W. Scott, Jr. J. Thorac.
Surg., 1959, 38: 639.

Suran, J. J. Circuit properties of the PNPN transis-
tor. Proceedings of the National Conference on
Aeronautical Electronics, May 1956.

Welricu, W. L., Gort, V. L., and LitLeser, C. W.
Treatment of complete heart block by combined
use of myocardial electrode and artificial pace-
maker. Surgical Forum; Clinical Congress 1957.
Vol. VIII, p. 360. Chicago: American College of
Surgeons, 1958.

ZOLL, P. M. Resuscitation of the heart in ventricular
standstill by external electric stimulation. N. Eng-
land J. M., 1952, 274: 768.