Reprinted from Vol. 23, No. 2, February 1958
The Current Status of
Open Cardiac Surgery

HENRY SWAN*

University of Colorado School of Medicine, Denver

"The inner surfaces of
the chambers of the
heart are the last ana-
tomic areas of the body
to yield to safe direct-
vision surgical inter-
vention. In the past
five years, two entirely
different methods to
achieve this have been
developed to the stage
of practical clinical ap-
plication. Thus, today, no portion of the hu-
man body defies surgical exposure.

The implications of this accomplishment on
the future treatment of various forms of heart
disease are obviously great, since both hypo-
thermia and cardiopulmonary bypass are only
in their infancy in terms of application to the
technical problems posed by specific disease
states. Significant advances in surgical treat-
ment of various forms of heart disease can be
confidently expected for years to come.

At present it would appear that hypothermia
is the safer of the two technics, but it also has

HENRY SWAN

*Department of Surgery, University of Colorado School of Medicine,
Denver, Colorado..

February 1958

 

stricter limitations. Since this method received
clinical trial earlier, it is not surprising that
it has achieved a slightly more mature state of
development. This is not, however, to say
some pump oxygenators may not soon equal
or exceed it in terms of risk; it is to be hoped
that both technics will soon be essentially
without risk. I shall outline some experience
with both methods, and indicate some of the
problems yet to be overcome.

Hypothermia

Stimulated by the report of Bigelow and
associates’ in 1950, hypothermia has been and
is at present under continuing investigation in
the Halsted Laboratory for Experimental Sur-
gery at the University of Colorado. It was
early observed that general hypothermia was
attended by a high mortality because of severe
myocardial arrhythmias (especially ventricu-
lar fibrillation) and because of serious dis-
turbances in the clotting mechanism. Exten-
sive experimental and clinical observations.
over the past five years have essentially elimi-
nated both these hazards. We feel that the risk
of hypothermia per se, as currently employed
in this clinic, is in the neighborhood of zero.

127
TABLE 1

ProcGressivE INCIDENCE OF SIGNIFICANT CARDIAC
ARRHYTHMIAS IN 265 Cases In Wuic
HyporHermia Was Usep

 

 

FIBRILLA- |
DEATH |STANDSTILL DEATH
TION
First 100 cases... 15 12 7 1
Second 100 cases .. 8 4 1 1
Last 65 cases .... 1 0 0 0

 

 

The following details in the management of
clinical hypothermia for cardiac surgery ap-
pear important in promoting the safety of the
method.

1. The range of the lowest rectal tempera-
ture achieved is 30 to 32° C. Circulatory ar-
rest is performed at this temperature.” This
limitation in degree of hypothermia is ex-
tremely important.

2. Cooling is accomplished simply and by
design by immersion in ice water. There ap-
pears to be some rationale in cooling the pe-
ripheral tissue ahead of the heart and other
vital organs.”

3. Throughout the entire procedure, a de-
liberate respiratory alkalosis is maintained by
hyperventilation.*-°

4. Throughout the course of the cooling,
operation and warming, dextrose is adminis-
tered intravenously. Evidence is increasing
that intravenous nutrients have a beneficial
effect on the myocardium in hypothermia.®

d. The first two units of blood used dur-
ing operation are heparinized, having been
freshly drawn in plastic bags. The presence of
platelets, fibrinogen and other enzyme ele-
ments of the clotting mechanism, together
with the absence of citrate, are considered
helpful in avoiding the bleeding diathesis of
hypothermia.’ Transfusion is given freely be-
cause a low blood volume is poorly tolerated
in hypothermia.®

6. A bilateral sternum-splitting incision is
always used in order to achieve adequate ex-
posure and allow proper positioning.”

7. Great care is taken to position the pa-
tient so that the cardiotomy is in the upper-
most portion of the heart, thus materially re-

128

ducing the risk of air embolism occurring in
the coronary arteries.’®

8. After the establishment of inflow occlu-
sion to the heart the coronary circulation is
perfused with 1 to 2 cc. of 1:4000 prostic-
MIN® in order to slow the heart. The decreased
metabolic needs of the slowly beating heart
apparently are important in reducing the risk
of ventricular fibrillation.’""

9. The root of the aorta is always clamped
(except in operations for aortic stenosis) to
prevent coronary blood flow during occlusion.
This helps avert coronary air embolism, main-
tains bradycardia, and diminishes the coro-
nary return to the heart, thus insuring a dry
operative field."

10. The period of circulatory arrest must
not exceed six minutes. If more time is needed
to complete the procedure, the operation should
be interrupted and the circulation restored. A
second period of occlusion can then be insti-
tuted after an appropriate interval to complete
the procedure. The principle of multiple short
occlusions allows at least 10 minutes of safe
intracardiac time."

ll. Warming is achieved by diathermy.
which is a form of internal warming. There
appears to be some rationale for rewarming
vital internal organs before peripheral tissues.”

Careful observation of these considerations
reduces the mortality rate of hypothermia it-
self to a level that is essentially negligible.
For example, the incidence of serious cardiac
arrhythmias in our series of patients is given
in table 1. The incidence of disturbances in
the clotting mechanism is given in table 2. It
is clear that as the limitations of the methods
and better control of the unusual physiology
were learned the risk has steadily decreased.

TABLE 2

ProcressivE INCIDENCE OF CLOTTING DISTURBANCES
Durine or AFTER HyroTHeRMIA

 

 

BLEEDING | THROMBOSIS | DEATH
First 100 cases 4 2 6
Second 100 cases 3 2 5
Last 65 cases ..... 0 1 0

 

 

POSTGRADUATE MEDICINE
TABLE 3

ProcressiveE Morta.ity For ALL Patients UNDERGOING
Open Carptac Procepures Durinc
HypoTHERMIA (180 Cases)

 

 

DEATHS
Number | Per Cent
First 60 cases toe. 12 20
Second 60 cases . 6 10
Third 60 cases 3 5

 

In the last 65 cases, not a single death was at-
tributable to either ventricular fibrillation or a
disturbance of the clotting mechanism.

The effect of better over-all management of
hypothermia on the mortality rate of open
heart operations is seen in table 3. Of course,
better selection of patients and improving
technic with increasing experience may play
a part in the trend of these figures, but irre-
spective of the relative importance of various
factors it is gratifying that there has not been
a single death among the last 41 patients un-
dergoing bilateral thoracotomy and open car-
diotomy during hypothermia.

In view of this experience, we feel at pres-
ent that those open cardiac procedures which
can be technically achieved in 10 minutes of
direct-vision time should be done during cir-
culatory occlusion under hypothermia, since
the method itself is so safe.

The following diseases are examples of le-
sions for which the open operation is clearly
preferable to blind technics and the procedure
can be done adequately within the time limit.

1. Pulmonary valvular or infundibular ste-
nosis occurring as a single lesion.

2. Atrial septal defect (secundum).

TABLE 4

Resutts or Direct-Vision Repair oF PULMONARY
Stenosis During HypoTHERMIA

3. A combination of pulmonary stenosis
and atrial septal defect (trilogy of Fallot).

4, Aortic stenosis.

Both valvular and infundibular pulmonic
stenosis, occurring as isolated lesions, are
readily amenable to plastic repair. The results
of open intervention in restoring normal hemo-
dynamics and obliterating the pressure gradi-
ent have been very satisfactory.'® Since the
mortality has been nil in this group, we now
recommend operation to any young patient
whose pressure in the right ventricle exceeds
70 mm. Hg, irrespective of whether or not he
has had any symptoms relative to the heart.
Table 4 shows our total cumulative experience
with these two lesions. With the risk rate so
low and the results so satisfactory following
open operation during hypothermia, it seems
unwise at this time to recommend either a
closed procedure or use of the pump oxygena-
tor, with its greater risk.

Atrial septal defect of the so-called secun-
dum type is a lesion complicated by many as-
sociated variations. Aberrant pulmonary ve-
nous drainage into the right auricle, multiple
septal defects, unusual prominence of the valve
of the inferior vena cava, and associated pat-
ent ductus arteriosus all commonly participate
in this malformation. With such complexities
it seems hardly necessary to mention the su-
periority of an open technic for treatment. In
spite of its variety it is uniformly possible to
repair the lesion in such a fashion that the
pulmonary veins are transplanted to the left
side of the repair in less than 10 minutes of
operating time. Table 5 outlines our experi-
ence with this operation. In view of the fact
that the last 41 patients with atrial septal de-
fect have undergone a curative procedure with-
out mortality, we are currently extending our

TABLE 5

REsuLts oF Direcr-Vision REPAIR OF ATRIAL
SeptaL Derect (Secunpum) Durtne

 

 

 

 

 

 

(Intact SEpta) HyPoTHERMIA
TYPE | CASES | CURED | IMPROVED | DEATHS CURED DIED
Valvular . 34 32 2 0 First 43 patients 36 | 7 (16%)
Infundibular....) 4 | 4 | 9 0 Last 41 patients 41 0

 

February 1958

 

129
TABLE 6

Resutts oF Dinect-Vision Orenation Durinc
HyYpoTHERMIA IN TRILOGY OF FALLoT

 

CASES |OPERATIONS|TOTAL CURE| IMPROVEMENT | DEATH

 

16 18 6 7 3

 

 

 

indications for operation in young persons
with this disease. We believe at present that all
patients with atrial septal defect (secundum)
should have operation when the diagnosis is
established, irrespective of the presence or ab-
sence of symptoms, gross cardiac enlargement,
or other objective findings. A major contrain-
dication to operation is reversal of the shunt
with consequent cyanosis. In this respect,
therefore, the indications for surgery are es-
sentially similar to those for patent ductus
arteriosus.

The combination of atrial septal defect and
pulmonary stenosis (trilogy of Fallot) presents
interesting therapeutic problems. In 15 of our
16 cases the shunt preoperatively was right to
left, and the patient was cyanotic, in some
instances extremely so. Our initial impression
was that if adequate relief of the pulmonic
stenosis were achieved the atrial septal defect
might close spontaneously. However, in some
cases cyanosis has persisted while in others a
conversion of the shunt to a left-to-right direc-
tion has resulted in cardiomegaly and even
cardiac failure. Two of these earlier patients,
therefore, have undergone a second hypo-
thermic procedure to close the auricular sep-
tal defect. In our last four patients we per-
formed a two stage curative procedure at a
single session, first opening the pulmonary
valve and then suturing the atrial septum at a
second occlusion. Our cumulative experience
with this malformation is seen in table 6. Some
of the earlier patients with only a single stage
may eventually need closure of the atrial sep-
tal defect. In six of the surviving patients the
circulatory system has been restored essential-
ly to normal.

More recently we have explored the possi-
bility of transferring our technic for pulmonic
obstruction to operation on the aortic valve."
Exposure of the ostia of the coronary arteries

130

to room air did not prove a serious deterrent,
as methods for avoiding coronary air embo-
lism were developed. The risks of this proce-
dure have proved to be largely technical, since
the need for much greater care in avoiding re-
gurgitation of the aortic valve following ma-
nipulation limits the operation and extends
the operative time. Nonetheless, the results in
a small series to date have been sufficiently
satisfactory to warrant continuation of the
technic. These results are shown in table 7.
In our opinion the open procedure is so su-
perior to the digital and blind instrumental
technics previously available that operative
intervention in rheumatic aortic stenosis is
justified much earlier, before there is exten-
sive calcification of the valve. In addition, it
is suggested that congenital aortic stenosis is
more common than generally supposed and
that, whether the obstruction is valvular or
subvalvular in position, open operation is in-
dicated when left ventricular strain is present,
with or without subjective symptoms.

Total Cardiopulmonary Bypass

Many lesions require much more operating
time than that currently permitted by hypo-
thermia. For these, the pump oxygenator using
total cardiopulmonary bypass is the method
of choice. The variety of oxygenators and
pumps currently in use throughout the world
attests to the fact that the best design for such
an instrument has yet to be developed. The
problems associated with total bypass are mul-
tiple. Blood procurement and crossmatching,
rate of flow, type of pulse, adequacy of oxy-
genation and extraction of carbon dioxide,
avoidance of air embolism, aberrations in me-

TABLE 7

Resuits oF Direct-Viston Repair oF AORTIC
Stenosis Durtnc HYPOTHERMIA

 

 

CASES | IMPROVEMENT | DEATH
Congenital
Valvular 10 9 1
Subvalvular 3 | 1 2
Acquired i 2 2 0

POSTGRADUATE MEDICINE
tabolism, difficulties in sterilization, protection
of the formed elements of the blood, and
avoidance of interference with the clotting
mechanism are only a few. Moreover, all these
difficulties are compounded with time; the
longer the perfusion, the greater the risk of
serious or fatal physiologic deviation. Thus the
very essence of the need for pump oxygena-
tion, a prolonged operative time, imposes a
condition which raises the risk. We know of
no pump oxygenator as yet which has a risk
rate approaching that of hypothermia.

Our earlier experience with a bubble-type
oxygenator was extremely unsatisfactory.
Damage to the cells, disturbance in clotting,
and diffuse cerebral damage presumably from
multiple small emboli were associated with
inadequate flow rates. For these reasons we
turned to a screen-type oxygenator with roller
pumps, a combination which had long been
studied by Gibbon,’* and was subsequently
further refined by Kirklin et al.'° After exten-
sive laboratory trial, this instrument received
clinical trial in 13 cases of advanced pulmo-
nary hypertension associated with interven-
tricular septal defect. In most instances it was
possible to close the defect by direct suture,
but in three it was necessary to plug the defect.
One patient, undergoing operation for the sec-
ond time, had profuse bleeding during and
after heparinization. Her hemorrhagic diathe-
sis eventually proved fatal. Another child died
quite unexpectedly of heart block a few hours
after operation. The other 11 patients have
done well, but the effectiveness of the repair
and its influence on the advanced pulmonary
vascular disease remain to be studied. It ap-
pears that the pump oxygenator system we are
using is adequate although still replete with
danger as bypass is prolonged. It will remain
the subject of continuing laboratory investiga-
tion. We intend to extend its use to more com-
plicated lesions such as transposition and tet-
ralogy and to continue work on its potential
use in acquired valvular disease.

Summary

Our experience with the current methods
available for open cardiac surgery is briefly
reviewed. At present, after a broad experience,

February 1958

we consider hypothermia to be essentially
without risk and therefore the method of
choice for intracardiac procedures which can
be accomplished in 10 minutes or less. Our
screen oxygenator in association with roller-
type pumps has proved adequate for total car-
diopulmonary bypass. The risks of this in-
strument have not been thoroughly assessed,
but application to a broader spectrum of intra-
cardiac conditions seems justified on the basis
of our early experience.

REFERENCES

1, Bicetow, W. G., Lrvosay, W. K. and Greenwoop, W. F.: Hypo-
thermia: Its possible role in cardiac surgery; an investigation ut
factors governing survival in dogs at low body temperatures.
Ann. Surg. 132:849 (November) 1950.

2. Swan, H. and Brount, S. G., Jr.: Visual intra-cardiac surgery
in a series of 111 patients. J.A.M.A. 162:941 (November 3) 1956.

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A study of the icewater surface immersion and short-wave dia-
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4, Swan, H., Zeavin, I., Hotmes, J. H. and Monrcomery, V.:
Cessation of circulation in general hypothermia. I, Physiologic
changes and their control. Ann. Surg. 138:360 (September) 1953.

5. Zeavin, I, Virrcz, R. W. and Swan, H.: Cessation of circulation
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6. Caranna, L., .Tecmosse, F. J. P. and Swan, H.: The effect of
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- Swan, H., Virtue, R. W., Brount, S. G., Jr. and Kircner, L.
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ll. Preveper, A. E., Montcomery, V. and Swan, H.: Effect of
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(March) 1954.

12. Monrcomery, V., Prevever, A. E. and Swan, H.: Prostigmin in-
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13. Barr, S., Monrcomery, V., Brain, E. and Swan, H.: The rela-
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14. Swan, H., Zeavin, I., Burount, S. C., Jr. and Virtus, R. W.:
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15. Bram, E., Austin, R. R., Buount, S. G., Je. and Swan, H.:
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16. Brount, S. G., Jr., van Exx, J., Batcrum, QO. J. and Swan, H.:
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