Reprinted from TRANSPLANTATION BULLETIN
Vol. 2, No. 4, pp. 189-140, October, 1955
Printed in U.S.A.

BLOOD VESSELS

This account deals with our experience with the
surgical treatment of dissecting aneurysms of the
aorta and the use of homografts in this condition.
As is known, this form of aneurysm is associated
with a grave prognosis, having a rapidly fatal
course in 75 to 90% of the cases, and up to now
treatment has been largely symptomatic and
unsatisfactory.

Pathologically, the lesion differs from other
forms of aneurysm in its tendency to be diffuse
rather than segmental in character, often ex-
tending throughout the extent of the aorta. It
begins usually in the upper reaches of the aorta
as a transverse tear in the intima and media just
above the aortic valves or near the origin of the
left subclavian artery, with separation of the
intramural layers of the aorta by the forceful
stream of blood. This dissection may then
progress circumferentially to involve all, or a
portion, of the aorta and distally down to the
bifurcation, and even lower, to involve the fem-
oral arteries. The extent and course of the dis-
section is quite variable and in most instances
there is final terminal perforation through the
outer wall, resulting in death in a few hours or
days. In some cases, re-entry of the dissected
passage into the true lumen takes place, usually
at some point in the abdominal aorta, with the
formation of a so-called “‘double-barrelled” aorta.
This is nature’s method of dealing with the prob-
lem and the patient may then survive for months
or years.

It is thus apparent from these pathologic
features of the disease that the principles of sim-
ple excisional therapy with homograft replace-
ment, as used, for example, in fusiform aneurysms
of the aorta, cannot be applied here in most
instances. For this reason another approach to the
problem is necessary. This was suggested to us by
nature’s method of healing, in which spontaneous
re-entry of the dissected passage occurs, with

restoration of peripheral circulation. Accordingly,
this constituted the basis for the principles under-
lying the procedure employed in our first case.

This patient, a white male 58 years of age,
had experienced sudden, constricting pain in the
chest approximately a year prior to admission
and on radiologic examination of the chest was
found to have a rounded density in the posterior
inferior mediastinum that projected into the left
hemithorax and appeared to be a markedly tor-
tuous, dilated descending thoracic aorta. At
operation, on July 7, 1954, the left pleural cavity
having been entered through the bed of the re-
sected fifth rib, there was revealed a U-shaped
aneurysm of the descending thoracic aorta which
projected posteriorly and to the left. The aorta
above and below was elongated, tortuous and
dilated, being more than twice normal. size.
After division of several pairs of intercostal ar-
teries and mobilizing the aorta above and helow
the aneurysm, occluding clamps were applied
proximal and distal to the U-shaped aneurysmal
process, and the intervening segment was ex-
cised. Upon cutting across the distal end, there
was revealed a double lumen formed by the dis-
secting process. The proximal end, however,
showed only one lumen and on examination of the
excised specimen it was apparent that the aorta
had been divided above the origin of the dis-
secting aneurysm. The false Jumen in the distal
end was then obliterated by approximating the
edges of the outer and inner walls with inter-
rupted sutures (we have since used a continuous
suture for this purpose). It was then possible to
restore continuity by end-to-end anastomosis.
Recovery was uneventful and the patient has
since remained well. Subsequent angiocardio-
grams revealed a relatively normal outline of the
descending thoracic aorta.

There were two unusual features in this case.
The first was that the dissecting process began
in the descending thoracie aorta and it was thus
possible to remove it. The second unusual feature
was that no homograft was needed to bridge the

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140

defect, owing to the fact that it had become
elongated, thus providing sufficient length, after
it had been mobilized, to bring the ends together.

In subsequent and more typical cases, the
origin of the dissecting process was found to have
taken place in the region of the aortic arch.
Under these circumstances the descending tho-
racic aorta is mobilized and cross-clamped in a
similar manner and then divided between the
clamps. The false passage in the lower end is also
obliterated in a similar fashion by approximating
the outer and inner layers. The proximal end,
however, is managed somewhat differently, since
the purpose here is to create an opening between
the outer and inner lumens for the flow of blood
from the dissecting false passage into the true
lumen. Accordingly, a wedge shaped segment is
excised from the inner wall and the two ends of
the aorta are approximated by end-to-end
anastomosis. Thus, blood from the double aortic
lumen above is diverted into the single normal
lumen below. Although this obviously does not
cure the dissecting aneurysm in the region of the
aortic arch, it is believed to have the following
beneficial effects. First, by shortening the extent
of the false passage there is a tendency to reduce
peripheral resistance to blood flow and thus
diminish the danger of rupture of the weakened
outer wall; second, by restoring blood flow into
the normal aortic lumen in the abdominal aorta
there is a tendency to correct the compressive
ischemic effects of the false passage upon the
points of origin of the major vascular channels
arising from the aorta.

In still other forms of the disease the dis-
secting process may be associated with a fairly

TRANSPLANTATION BULLETIN

well localized fusiform or sacciform arising in
the outer wall. Under these circumstances it
would seem desirable to combine the principles
used above with those of excision and replace-
ment of the defect with a homograft. This form
of treatment was employed in two of our cases.
The aneurysm in these cases arose near the origin
of the subclavian artery and, while the dissecting
process extended down into the abdominal aorta,
there was a fairly well localized fusiform aneu-
rysm involving the outer wall in the distal part
of the aortic arch. The procedure employed here
consisted in cross-clamping the aorta at the level
of the subclavian artery proximally, and just
below the fusiform dilatation distally, excising the
intervening segment, obliterating the distal false
passage by approximating with suture the inner
and outer walls, and restoring aortic continuity
with a homograft. Hypothermia is employed in
these cases where temporary arrest of aortic cir-
culation must be done at such a high level in
order to prevent ischemic damage to the spinal
cord.

Our experience with these methods of treat-
ment includes 6 cases, with 2 deaths, one of which
occurred on the eighth post-operative day from
rupture into the pericardium, presumably from
uncontrollable hypertension, and the other from
ventricular fibrillation, probably as a consequence
of tension penumothorax and hypothermia. The
results in the 4 patients who recovered have been
quite gratifying.

Micwarr Ei. DeBary, M.D.
Baylor University College

of Medicine
ITouston, Texas