Keywords
aortic dissection - repeat surgery - frozen elephant trunk technique
Introduction
During conventional surgery for acute Type-A aortic dissection (AAD), a prosthetic
replacement limited to the ascending aorta is generally performed, without cerebral
vessel debranching and/or arch replacement.[1]
[2] Aneurysmal dilatation of the residual dissected aorta may occur, particularly if
the intimal tear involved the aortic arch at the time of the initial operation.[3]
[4]
[5] The need for reoperation is greater in patients with Marfan's syndrome.[6] For this reason, some patients may require surgical repair of the chronically dissected
aortic arch and the descending thoracic aorta.
Staged procedures for management of extensive disease of the remaining thoracic aorta,
including the use of the elephant trunk (ET) technique, have been successfully used
to treat the aforementioned conditions.[7]
[8]
[9]
[10]. Although these are useful techniques, marked aneurysmal dilatation of the proximal
descending thoracic aorta (the usual site for anchoring of the aortic graft) is often
present in the setting of chronic aortic dissection (ChAD) marking that dilation may
preclude the safe anastomosis of a graft to the aorta in this area. Furthermore, the
aggregate mortality and morbidity for the staged procedure may be substantial.
A less invasive approach may be represented by a hybrid approach with cerebral vessel
rerouting followed by a TEVAR. But the limited length of the previously implanted
ascending aortic graft rarely provides enough room allowing a beating-heart cerebral
vessel debranching and the creation of a reliable landing zone for the implantation
of a firmly anchored thoracic endovascular stent graft. [11]
[12]
[13]
In the last few years, many publications have advocated the advantage of the FET technique
which combines the cut-and-sew technique at the level of the distal aortic arch with
an endovascular stent-graft implantation in the descending thoracic aorta.[14]
[15]
[16]
[17] As FET has evolved, many variations of this procedure have been described. All these
procedures have in common that the stent graft is delivered into the open aorta under
circulatory arrest and it is sutured, at least partially, into the dissected aortic
arch. This intervention is a major surgical procedure, requiring prolonged time on
cardiopulmonary bypass (CPB), hypothermic circulatory arrest, and selective cerebral
perfusion. The prolonged spinal cord ischemia, associated with the exclusion of several
intercostal arteries, increases the risk of paraplegia. In the Bologna experience,
Di Eusanio et al[18] described an incidence of 7.4% permanent neurologic dysfunction and 9.0% spinal
cord injury. Further, the execution of the distal anastomosis in Hishimaru's zone
3 may be impaired by its distal location and by the frequent poor quality of the dissected
aortic wall in this area.
We propose a new technique which preserves all the advantages of FET. Anastomosing
the stent graft to the previously implanted ascending aortic graft allows complete
exclusion of the aortic arch and of the proximal thoracic descending aorta without
“touching” the native chronically dissected aorta. Since 2014, we have employed this
technique in five patients without observing any early or midterm mortality or any
major neurological complications.
Materials and Methods
We retrospectively analyzed all consecutive patients treated in our institution between
2014 and 2017 for ChAD after the successful surgical treatment of acute Type-A aortic
dissection with graft replacement of the ascending aorta.
Patients in whom cerebral vessels rerouting had been performed at the first operation
have been excluded from this report. They were treated by traditional thoracic endovascular
aneurysm repair (TEVAR) at the repeat operation. Furthermore, when the previous ascending
aorta graft implant was longer than 5 cm, cerebral vessel debranching on beating heart
was performed to obtain a reliable landing zone for allowing a stable anchored stent
graft for TEVAR. Also, this group of patients was excluded from this report.
The institutional review board approved this study. All patients provided written
consent.
Five patients underwent surgical correction of the chronic dissection with our modified
FET technique with total aortic arch and upper descending aortic exclusion without
touching the native aorta. The same surgeon performed all procedures. The indication
for surgery was aneurysmal enlargement of a ChAD involving the aortic arch and the
descending thoracic aorta. The choice of this technique was related to the presence
of a short previous ascending aortic graft (<5 cm). We used a C-Tag stent graft (C-TAG,
WLGore Arizona) of 31 of 34 mm diameter and 20-cm length in all patients.
Patient characteristics are described in [Table 1]. Mean age was 52 ± 15 years, and 80% were men. There were two Marfan's patients.
All patients were in NYHA class 1 to 2. Mean delay time between first operation for
acute aortic dissection and the second operation was 26 months (range, 3–80 months).
Table 1
Baseline patient characteristics
|
Characteristics
|
n = 5
|
%
|
|
Age (y)
|
52 ± 15
|
–
|
|
Male
|
4
|
80
|
|
Left ventricular ejection fraction >50%
|
5
|
100
|
|
NYHA class I–II
|
5
|
100
|
|
Elective surgery
|
5
|
100
|
|
Previous surgery for AAD
|
5
|
100
|
|
Interval between operations (mo)
|
26 (range, 3–80)
|
–
|
Abbreviations: AAD, acute aortic dissection; NYHA, New York Heart Association.
Surgical Technique
Preoperative computed tomography (CT) of the chest, abdomen, and pelvis is performed
to assess surgical strategy and to determine the stent-graft distal landing zone.
The selection of the stent graft is based on the diameter of the previously inserted
graft in the ascending aorta with an oversizing of 2 to 4 mm. As an example, in a
28 of 30-mm graft in the ascending aorta, we generally insert a 34-mm stent-graft.
Such selection proves adequate for stenting the descending aortic aorta.
The first step of the procedure consists of performing an 8-mm PTFE carotid-left subclavian
artery bypass, through a left supraclavicular incision. Pressures are monitored in
both radial arteries and in the left femoral artery. Cerebral oxymetry is assessed
by the noninvasive INVOS system (Covidien, Medtronic Inc., Minneapolis, MN). Next,
an echo-guided pig-tail catheter is threaded though the left femoral artery in the
true lumen of the dissected aorta until its tip reaches the lumen of the previously
implanted ascending aortic graft.
Median sternotomy is performed and the incision is extended to the left cervical area
for ease of control of the cerebral vessels, particularly of the origin of the left
subclavian artery. A trifurcated modified graft with a side-arm perfusion port is
selected (Hemashield's 12–8–8 mm) and two of its distal branches are respectively
anastomosed to the transected left common carotid and to the innominate artery with
the heart beating.[18] During this time, the cerebral vessels are perfused via the native left subclavian
artery previously anastomosed to the left carotid artery ([Fig. 1]). With sequential debranching and reperfusion of the three head vessels, as described
by Matalanis et al,[19] complete and rapid cerebral perfusion is ensured.
Fig. 1 Carotid-left subclavian artery bypass and innominate and left carotid reimplantation
on the trifurcated graft. The arrow indicates the direction of blood flow for cerebral
vessels perfusion during all the 4 steps of the operation: anterograde flow, on beating
heart, guarantee left subclavian artery and left carotid throw the PTFE carotid-left
subclavian artery bypass.
CPB is then started between the right femoral artery and the right atrium. The ascending
aorta is crossclamped and antegrade cardioplegia is infused. At this point, the cerebral
vessels are perfused by the CPB in a retrograde fashion through the subclavian artery.
The proximal extremity of the trifurcated graft is anastomosed to the graft originally
implanted in the ascending aorta ([Fig. 2]). When this stage is completed, antegrade perfusion of all cerebral vessels is achieved
via the cannulated third-arm perfusion port of the trifurcated graft. The native left-subclavian
artery is ligated.
Fig. 2 Trifurcated graft anastomosed proximally on the ascending aorta graft on cardiopulmonary
bypass with aorta cross clamped to allow an easy proximal reimplantation close to
the previous anastomosis. Retrograde flow from cardiopulmonary bypass throw femoral
arterial cannulation. Please note, at this time of the operation, left carotid artery
and the innominate artery are perfused throw carotid-left subclavian bypass graft.
An appropriate stent graft is selected and prepared. The patient is cooled to 28°C
and CPB is discontinued. Under circulatory arrest, the ascending Dacron graft is opened
proximally to the old distal anastomosis. The selected stent graft is prepared. A
superstiff wire guide (Lunderquist extra stiff wire guide, Cook Medical LLC, Bloomington,
IN) is introduced through the pigtail previously inserted from the left femoral artery
and, through this access, the stent graft is deployed in an antegrade fashion under
direct vision.
Once the stent graft is deployed, the stent graft is sutured to the original ascending
aorta Dacron graft ([Figs. 3]
[4]
[5]).
Fig. 3 Stent-graft released under circulatory arrest and fixed to the previously implanted
ascending aorta graft. During circulatory arrest time, all three cerebral vessels
are continuous perfused by a cannula inserted on the trifurcated modified graft.
Fig. 4 Intraoperative photograph of stent graft sewing over previous implanted ascending
aorta Dacron graft. Reproduced with the permission from photographic archives of Clinica
San Gaudenzio, Novara.
Fig. 5 Final result with aortic arch and descending thoracic aorta replacement. At the end
of the operation, we remove the clamp on the principal branch of the trifurcated graft
and all three cerebral vessels are perfused.
At this point, CPB is restarted. When the rewarming is complete, cardiopulmonary is
discontinued.
Results
There were no intraoperative or in-hospital deaths. [Table 2] describes continuous operative data. The postoperative course was uncomplicated
for all patients. All patients were extubated on the first postoperative day and discharged
within 15 days. No patient had a minor/major neurologic event.
Table 2
Continuous operative data
|
Variables (min)
|
Mean (range)
|
|
Cardiopulmonary bypass
|
141 (98–171)
|
|
Cardiac arrest time
|
74 (54–93)
|
|
Hypothermic circulatory arrest
|
16 (11–25)
|
|
Selective cerebral perfusion
|
31 (15–80)
|
Note: selective cerebral perfusion was considered the perfusion of the cerebral vessels
by the dedicated trifurcated graft; all three cerebral vessels were perfused.
Follow-up was complete for all patients with a postoperative CT scan ([Fig. 6]). Mean follow-up time was 22 months (range, 9–42 months). No mortality was observed.
Three patients underwent thoracoabdominal surgery within 3 months from the operation.
One patient has a Type-II endoleak due to an incomplete ligation of the subclavian
artery that was treated successfully by coil embolization.
Fig. 6 Volume-rendered computed tomography reconstruction in a Marfan patient: (A) first step: aortic arch and descending aorta replacement and (B) second step: thoracoabdominal aortic replacement.
Discussion
In patients with chronic dissection, aortic repair is usually performed electively
for aneurysmal degeneration of the false lumen. Most of these patients are survivors
of De Bakey's Type-1 dissections. After repair of acute Type-A aortic dissection by
graft replacement of the ascending aorta, the false lumen distal to the aortic graft
remains patent in 70 to 100% of patients.[20] Follow-up has shown that reoperation for aneurysmal dilatation of residual dissected
aorta is required in 20 to 30% of patients within the first 5 to 7 years. The need
for reoperation is more common in patients with Marfan's syndrome and when the original
intimal tear involved the aortic arch at the time of the first operation.[3]
[4]
[5]
[6]
For this indication, it is not only important to cover the proximal entry tear; one
must also address all-entry tears feeding the aneurysmal segment of the aorta. Most
commonly, this aneurysmal degeneration occurs in the distal aortic arch and the proximal
descending aorta, making the FET technique particularly well suited for this indication.
The rationale for using a stent graft in ChAD is the proximal expansion of the true
lumen covering the reentry sites along the proximal descending thoracic aorta, as
well as the realization of a satisfactory landing zone, for a possible future distal
aortic reoperation.
As FET has evolved, many variations for implantation have been described. [20]
[21]
[22]
[23] Their common feature is that the stent graft is delivered into the open aorta under
circulatory arrest and sutured into position. However, this necessitates suturing
the stent graft, at least partially, into the dissected aortic arch. Although these
are useful techniques, marked aneurysmal dilatation of the proximal descending thoracic
aorta, the usual site for attachment of the aortic graft, is often present in the
setting of ChAD and may preclude safe anastomosis of a graft to the aorta in this
area. Furthermore, all hybrid grafts retain the complexities of surgery and its associated
risks, particularly the prolonged ischemic durations of the heart, brain, spinal cord,
and viscera.[24]
[25]
We have described a new surgical approach for the treatment of chronic aortic arch
and proximal descending aortic dissection following repair of a Type-A acute aortic
dissection. The advantage of our technique is that, after releasing the stent graft
under circulatory arrest, we secure it to the graft previously implanted in the ascending
aorta in without touching the native dissected aorta. The performance of an anastomosis
in Hishimaru's zone 0 presents an easy surgical view and an enhanced suture control.
Consequently, we have observed fewer hemorrhagic complications with greater hemodynamic
stability in the early postoperative period. Other advantages of this technique include
the short circulatory arrest time and, thus, a theoretically decreased likelihood
of spinal cord damage. In our initial experience, we did not observe any neurologic
complications. Another advantage is the avoidance of a potential injury to the recurrent
laryngeal nerve.
During conventional surgery for AAD, a short ascending aortic replacement is generally
performed, without cerebral vessel debranching and arch replacement. In repeat surgery,
this surgical graft rarely provides enough room to perform cerebral vessel debranching
on beating heart and to obtain a reliable landing zone for a stable TEVAR. Length
of the ascending aorta Dacron graft less than 5 cm was considered a contraindication
to performing a total cerebral vessel rerouting on beating heart followed by a TEVAR.
Recently, we have extended this surgical strategy not only for the treatment of ChAD
but also for the treatment of arch and proximal descending thoracic aorta aneurysms
for one step repair or as a bridge to definitive thoracoabdominal repair.
Conclusions
This study documents our experience with a small number of patients and a short follow-up
period. However, our data suggest that this modified FET technique without “touching”
the native dissected aorta constitutes a suitable alternative to a more complex surgery
such as the staged ET approach or the classical FET technique with the distal anastomosis
in the descending thoracic aorta. Our study may represent a less demanding solution
to redo Type-A aortic dissection surgery in which substantial enlargement of the proximal
descending thoracic aorta precludes an easy suturing of a prosthetic graft to this
segment of the aorta. This new technique is now our preferred method of management.
A larger number of patients and longer follow-up will be required to confirm these
initial encouraging results.
