Keywords
aortic aneurysm - elephant trunk - stand-alone
Introduction
Patients with aortic disease involving the descending thoracic aorta present a major
surgical challenge due to the extent of the disease and the morbidity and mortality
associated with the repair procedure.[1] Depending on the extent/anatomy of the disease they may require more than one surgical
intervention. Although endovascular repair techniques are associated with less morbidity
compared with open repairs, they may not be technically suitable for all patients
and their durability is uncertain.[2]
Repair of descending aortic disease (open or endovascular) requires a securely landed
graft at the distal aortic arch level. In the present era, this is often accomplished
by cumbersome extra-anatomic debranching of the aortic arch. We report our experience
with an alternative procedure, the “stand-alone” elephant trunk (ET). For this procedure,
we transect the aortic arch between the left carotid and left subclavian arteries.
We then sew the two sides together, incorporating a Dacron ET in the distal segment.
We performed this procedure in 5 patients between January 2010 and June 2020 and analyzed
our results.
Methods
We reviewed our institution's (Aortic Institute at Yale-New Haven) experience with
5 patients who underwent “stand-alone” ET procedure by retrospective chart review.
This study was approved by the Yale University Human Investigations Committee, and
the requirement for individual consent was waived. The Yale Aortic Institute database
was searched for the period from January 1, 2010 to July 30, 2020. Each patient's
data were collected including the following variables: sex, age, the occurrence of
stroke or paraplegia, need for surgical reexploration for each stage, period between
two stages, follow-up details, and overall mortality. Patients were followed up through
June 2020.
Surgical Technique
Stage 1
Stage 1 is performed through a standard median sternotomy. Standard cardiopulmonary
bypass (CPB) is instituted via the left femoral artery and right atrium. Straight
deep hypothermic circulatory arrest (DHCA) is utilized during the ET placement. The
head is packed with ice. We do not use cerebral perfusion techniques, either antegrade
or retrograde. Following exposure of the arch vessels, the distal ascending aorta
is cross-clamped and the first dose of cardioplegia is given. Once the nasopharyngeal
temperature reaches 18 to 20°C, the patient is put in the Trendelenburg position,
circulatory arrest is instituted, and the cross-clamp is removed. We transect the
aortic arch between the left carotid and left subclavian arteries (perpendicular to
its long axis). We then sew the two sides of the aorta together, incorporating a Dacron
ET in the distal segment ([Fig. 1] and [Video 1]). After completion of the anastomosis, the aorta is de-aired, DHCA is terminated,
CPB flow is increased gradually, and rewarming begun. When the bladder temperature
reaches 34°C, the patient is weaned from CPB.
Video 1 Surgical video illustration of the stand-alone elephant trunk procedure. [Video courtesy:
Elefteriades JA, Ziganshin BA. Practical Tips in Aortic Surgery. Springer; 2021.]
Fig. 1 Establishment of a stand-alone elephant trunk.
In terms of length of the ET, we make certain that it is long enough to reach well
beyond the subclavian artery, so that it can be retrieved easily at Stage 2. The paraplegia
risk from the ET before Stage 2 is minimal for two reasons: First, the aorta in which
the ET lies is quite dilated (that is the reason for the procedure in the first place,
so there is little danger of the free-floating graft occluding vital intercostal arteries).
Second, unlike a stented graft, the free-floating ET does not lie against the spinal
ostea with radial force.
Because the incision and anastomosis are done proximal to the left subclavian artery,
the recurrent laryngeal nerve is not in jeopardy.
Stage 2
General anesthesia is induced with a double-lumen endotracheal tube, cerebral spinal
fluid drainage is used to optimize spinal cord protection, the patient is positioned
in the right lateral decubitus position, and a left thoracotomy incision is made.
Cannulation is performed via the left inferior pulmonary vein and femoral artery.
The ET graft in the descending aorta is visualized by transesophageal echocardiography.
The ET is retrieved by the “finger-thumb technique”[3] ([Fig. 2]). Adenosine is administered for cardiac standstill (usually 16 g bolus) and a small
vertical aortotomy is done in the descending aorta (to create a tight fit for the
surgeon's finger and thumb) at the level of the ET graft. The graft is retrieved by
the finger-thumb technique, brought out of the aorta under finger-thumb control, and
clamped. (We find that the 15–20 seconds of asystole induced by the adenosine is generally
adequate to permit opening the aorta to retrieve and clamp the ET graft.) The length
of the ET is adjusted by pulling the graft distally (to undo interim retraction and
to spread the corrugations), and the distal anastomosis is performed. This anastomosis
is done to the transected distal aorta below the lower extent of the aneurysm. If
needed, an identical piece of Dacron graft is anastomosed to the original graft to
provided additional length. Left heart bypass is terminated and the remaining aortic
tissue is wrapped around the anastomosed graft. Intercostal arteries are managed by
our usual routine for descending aortic replacement. (Preoperative computed tomography
angiography of the spinal arteries is performed. Any identified spinal artery is spared
or reimplanted at the time of surgery.[4]) At the end of the surgical procedure, the left subclavian artery is transected
and connected to blood flow via a separate 8- or 10-mm Dacron graft originating from
the new aortic graft or the native aorta.
Fig. 2 (A) Illustrated is the transesophageal echocardiography-guided approach to the elephant
trunk graft. Please note the location of the recurrent laryngeal nerve, which is protected
by this technique. (B) Schematic illustration of elephant trunk graft retrieval in preparation for clamping.
Image courtesy: Ziganshin and Elefteriades.[3]
Results
There were 5 patients (4 males, 1 female) aged 41 to 68 (mean, 57 years). All procedures
were elective. We used DHCA for all cases. There was no operative mortality, stroke,
or need for reexploration due to bleeding in the first stage. All patients survived
to have the second stage procedure. The mean period between the stages was 6.7 months.
The second stage was performed open for all patients. There was no mortality, stroke,
or paraplegia in the second stage, either. The mean postoperative follow-up period
was 70.2 months overall. Four out of 5 (80%) patients were alive at follow-up. One
patient died due to sudden cardiac arrest of unknown etiology 8 years after the second
stage procedure.
Discussion
After the original ET technique, which was described by Borst et al in 1983, the procedure
was first modified by Crawford and Svensson.[5]
[6]
[7] Variations of this procedure continued to evolve over the years, including reversed
ET, bidirectional ET, and more recently the frozen ET technique.[8]
[9]
[10] In this report, we introduce another modification of this technique, the “stand-alone”
ET procedure, for patients who have descending thoracic aortic disease without ascending
and/or aortic arch involvement, and we review our clinical experience.
This procedure is useful and intended for ([1]) patients who require open replacement of the descending aorta who have no suitable
site for a proximal cross clamp, and ([2]) patients who are to undergo endovascular therapy of the descending aorta who require
a stable, secure, and durable proximal landing zone.
Traditional Elephant Trunk
Briefly, the basic principle of the traditional ET procedure includes replacement
of the aortic arch coupled with a free-floating extension of the arch prosthesis which
is left behind in the proximal descending aorta in the first stage; in the second
stage an extension of the prosthetic graft up is added, replacing the descending aorta
to the required level via an open lateral thoracotomy or percutaneously with an endovascular
graft in the second stage.[5]
[7]
[11]
[12] The main advantages of this two-staged technique become clearer during the second
operation. First, the proximal descending aorta does not need to be dissected, thereby
decreasing the risk of injury to the adjacent structures such as the pulmonary artery,
esophagus, lymphatic structures, and recurrent laryngeal nerve. Second, once the ET
is accessed and clamped under echo guidance a graft-to-graft extension can be added
with great rapidity, thus minimizing cross-clamp time and duration of spinal ischemia.
Third, this technique avoids the need for DHCA during the second stage. Also, with
this procedure the need to clamp the proximal left subclavian artery may be avoided,
thereby the risk of stroke and paraplegia is reduced.[11]
[13]
“Stand-Alone” Elephant Trunk
This modification is intended for the subset of patients who have severe descending
thoracic disease without ascending and/or aortic arch involvement. The “stand-alone”
ET technique provides a “rock stable” securely landed graft at the aortic arch level
without any need for an extra-anatomic debranching of the aortic arch level. This
greatly facilitates the second stage open procedure for descending aortic replacement.
In terms of potential endovascular therapies (for those teams that prefer such an
approach), this stand-alone technique provides an alternative to debranching thoracic
endovascular aortic repairs (d-TEVAR procedures).
We performed this procedure in 5 patients. There was no early mortality, no stroke,
no paraplegia, and no need for reexploration due to bleeding in either stage.
Perspective
This stand-alone ET procedure represents another alternative in a large armamentarium
of options for the aneurysmal descending aorta. This is intended specifically for
the subset of patients in whom the aortic arch is normal in size and shape. When the
arch itself is dilated, a traditional arch replacement and standard ET are appropriate,
with a later second stage via thoracotomy. It is also important to keep in mind alternative
one-stage procedures that can accomplish arch and descending aortic replacement in
one sitting: namely, arch and descending aortic replacement under DHCA with open proximal
anastomosis via left thoracotomy, or arch and descending aortic replacement via mid-sternotomy
supplemented by T-left thoracotomy, or bilateral anterior thoracotomy (clamshell).
Also, an endovascular approach by covered stent graft (after any requisite debranching
via sternotomy) is another popular alternative. We feel the stand-alone ET procedure
described here offers the powerful advantage of a secure, solid proximal anastomosis.
In conclusion, even though this experience reflects the results of a limited number
of patients in a single institution, the “stand-alone” ET procedure is a unique modification
that can be performed in a subset of patients with descending thoracic aortic disease
without ascending and/or aortic arch involvement, providing technical advantages with
low major morbidity and mortality.
