Abstract
Introduction: Surgery is the mainstay of treatment for aortic
dissection which lesion affected the aortic arch. Conventional surgical
methods usually use unilateral cerebral perfusion by cardiopulmonary
bypass (CPB) to maintain the perfusion of the brain, and the
reconstruction of arch branches must be performed under CPB. Unilateral
cerebral perfusion with prolonged CPB may lead to complications of
cerebral hypoperfusion. We propose a new technique that can accomplish
aortic arch branches replacement without the use of cardiopulmonary
bypass and maintain bilateral cerebral perfusion at all times.
Materials and Methods: From January 2018 to July 2021, we
performed the new technique in 23 patients. Furthermore, we performed a
retrospective analysis with patients undergoing conventional surgery
during the same period, comparing perioperative data and follow-up data
between two groups.
Result: The CPB time, deep hypothermic circulatory arrest time
and aortic cross-clamping time of new technique group was significantly
shorter than conventional group. Other perioperative data and follow-up
data were not statistically different.
Discussion: Simplified arch-first technique can significantly
shorten CPB, aortic cross-clamping and deep hypothermic circulatory
arrest time. The technique is theoretically safer because it can better
protect the cerebral perfusion during the operation. The short-term
efficacy of this technique is the same as that of conventional surgery,
and it is more convenient for surgeons to operate.
Conclusions: Compared with the conventional method, the
simplified arch-first technique is non-inferior, friendly in operation
and safer in theory, and is worthy of promotion.
Key words : Aortic dissection; Arch-first; Cardiopulmonary
bypass; Aortic arch reconstruction
INTRODUCTION
Acute aortic dissection(AAD) is an emergency situation, with
2.5-6/100,000 incidence per year according to an Oxford Vascular study
and a mortality of 50% within the first 48 hours if not
operated1,2. It is generally accepted emergency
surgery is the best way to resolve this problem3. Now,
a standard surgical approach is Sun’s procedure, namely graft
replacement of the ascending aorta and aortic arch, and integrating
frozen elephant trunk (FET) into the descending
aorta4.
Total arch replacement is complex and time-consuming, and long-time
interruption of cerebral blood flow increases the risk of cerebral
ischemia5. Conventional Sun’s surgery is the same as
most surgeries, generally needs cannulation through the right axillary
artery and right atrium to establish cardiopulmonary bypass (CPB) first.
Then the aortic root procedures are finished after the coronary
circulation arrest is instituted. FET is implanted into the descending
aorta, and the distal end of the four-branched vascular graft is
anastomosed with the FET under the deep hypothermia with selective
antegrade cerebral perfusion (SACP) and lower body circulatory arrest.
Only after all those steps are completed, the left common carotid
artery, left subclavian artery and brachiocephalic trunk can be
anastomosed with the vascular graft. Since the reconstruction of distal
aorta and arch is time-consuming, SACP time is required long enough in
the classic surgery to ensure cerebral protection. In addition, the
reconstruction of arch branches unavoidably takes up a big part of the
time of CPB. All those conditions may lead to excessive associated
operative complications.
We tried to establish autologous bypass through the femoral artery to
carotid arteries without CPB and extra materials, which allows us to
complete the reconstruction of the aortic arch branches without CPB and
hypothermia. At the same time, we ensured bilateral cerebral perfusion
throughout the whole operation, and the shortest left subclavian artery
ischemia time.
MATERIALS AND METHODS
23 patients were treated with arch-first technique in Qilu Hospital of
Shandong University from January 2018 to July 2021. One patient died
during surgery due to severe ischemic cardiomyopathy, and the remaining
22 patients (Group A) completed the surgery. The 22 patients’ mean age
were 56.5(±9.3) years old, and 9 (40.91%) of them were male. All
patients were diagnosed with acute type A aortic dissection (ATAAD) and
the lesion affected the aortic arch. 2 (9.09%) patients were type B
aortic dissection progressed into ATAAD after thoracic endovascular
aortic repair (TEVAR). Besides, we also reviewed and collected clinical
data from 25 other patients (Group B) as a historical control. Those
patients only underwent conventional Sun’s procedure by the same
surgical group during the same period. There was no significant
difference in the comorbidities of the two groups of patients. Patients’
preoperative characteristics are listed in Table 1. All discharged
patients were followed up by outpatient service, phone or WeChat. We
performed CT on patients at 3 months 6, and 12 months as required by the
guidelines3,6. This study was approved by Medical
Ethics Committee of Qilu Hospital of Shandong University. Patient
consent statement was waived due to no harm to patients.
All analyses were calculated using SPSS software (version 26.0, SPSS
Inc, Chicago, IL). Continuous data were presented as the mean ± standard
deviation (SD) or median (lower quartile -upper quartile). Student-t
test or Mann-Whitney U test was used for continuous variables.
Chi-squared test or Fisher’s exact test was used for categorical
variables. A P-value <0.05 was considered significant.
SURGICAL TECHNIQUE
Preoperative examination included computed tomographic angiography (CTA)
of coronary artery, carotid artery, thoracic aorta, abdominal aorta,
iliac artery and lower limb artery to determine the dissection.
Transthoracic echocardiography was performed to determine the aortic
root condition and other cardiac structural changes. The safety and
effectiveness of cannulation was analyzed by CTA to determine whether
the right subclavian artery, left common carotid artery and the femoral
artery, iliac artery of the cannulated side were true lumens.
The operation used combined intravenous and inhalation general
anesthesia. Central venous pressure, bilateral radial artery pressure,
unilateral dorsal pedal artery pressure and nasopharyngeal temperature,
rectal temperature were monitored during operation.
The patient was in a supine position and underwent a median thoracotomy,
exposes the right subclavian artery, the branches of aortic arch and
femoral artery. 1 mg of heparin per kilogram was given to heparinize.
Cannulations through femoral artery, left common carotid artery, and
right subclavian artery (or brachiocephalic artery if the right
subclavian artery is involved in the dissection) were used to establish
autologous bypass to maintain cerebral perfusion. The femoral artery was
intubated with 18-24mm cannula, the right subclavian artery was
intubated with 8-12mm cannula, and the left common carotid artery was
intubated with 6-8mm cannula (Figure 1A). The innominate artery should
be intubated with 10-14mm cannula if the right subclavian artery could
not be intubated. The pipeline of autogenous circulation was modified
from the arterial conduit of CPB. No additional material or instrument
was required. The root of the arterial tube was clamped before CPB to
ensure the sealing of autologous circulation.
Reconstruction of the arch branches could be performed after the
completion of autologous bypass. The sequence of anastomosis to
four-branched vascular graft was innominate artery, left common carotid
artery and left subclavian artery. The arch branches were clamped and
transected, then the proximal sides were sutured first to remove
vascular clamps to expose surgical field (Figure 1B). The distal stumps
were anastomosed with the limbs of vascular graft in turn. After the
reconstruction of the branches, vascular clamps were taken away to
de-air the vascular graft, then the both ends of the vascular graft were
clamped. Oxygenated blood from the right subclavian artery (or
innominate artery) retrograded into the vascular graft, and then, flowed
into the left common carotid artery and the left subclavian artery.
Cannulation of the left common carotid artery could be removed (Figure
1C). It should be noted that radial artery and dorsal pedal artery blood
pressure need to be closely monitored and maintained at relatively high
levels to ensure cerebral perfusion during this period.
The next step was establishment of CPB through cannulation of the right
atrial appendage. The left ventricle was vented through the right upper
pulmonary vein. CPB supplied arterial blood to the lower and upper parts
of the body through the femoral artery and right subclavian artery (or
innominate artery) respectively. Patients with known connective tissue
disease should have an aortic root replacement7.
Others with aortic sinus injured by dissection should be treated with
aortic root reconstruction (Wheat, Bentall procedure or reconstruction
of sinus of Valsalva) during the cooling phase (Figure 2D). When the
rectal temperature drops to 25°C, systemic circulation was arrested and
SACP was initiated. In order to facilitate the anastomosis, the clamp of
the distal end of vascular graft should be moved to a position near to
the proximal side. The aortic arch was transected on the anterior wall
and the FET was inserted into the true lumen of the descending aorta,
and the distal vascular graft trunk was anastomosed with the proximal
FET (Figure 2E). Then the perfusion of the systemic circulation was
restored, SACP was discontinued, and rewarming started. After the above
procedures were completed, there was sufficient time to check the
leakage of each anastomosis, especially the position of distal vascular
graft and proximal FET.
Finally, the proximal end of the four‐branched vascular graft was
anastomosed with the aortic root (Figure 2F).
RESULTS
The average time of autologous bypass in Group A was 35.2 ± 8.0 min. As
expected, the CPB time of arch-first technique was significantly shorter
than Group B (223.5 ± 45.2 min versus 254.2 ± 57.2 min, p =
0.049). Meanwhile, deep hypothermic circulatory arrest time and aortic
cross-clamping time also decreased markedly. Other measures, such as
concomitant surgery, ICU stay time, ventilator support time and
postoperative complications were not statistically different.
Intraoperative and postoperative data are listed in Table 2 and Table 3
respectively.
Two patients in Group A died during hospitalization. Both of them were
due to postoperative massive cerebral infarction, one of whom had renal
failure. Three patients in group B died in hospital. Causes of death
included extensive cerebral infarction, severe heart failure, ischemic
necrosis of abdominal organs, and severe renal failure and electrolyte
imbalance due to severe ischemic necrosis of lower extremities. There
was no significant difference in mortality between the two groups
(p =1.000).
The remaining patients were discharged successfully. Every patient
underwent CTA and was found that the autologous arterial blood flowed
smoothly, the true lumen was enlarged compared to pre-operation, and
thrombosis had formed and started to reabsorption in the false lumen.
The preoperative and postoperative CTA of the patient can be seen in
Figure 3. There were no complications such as death, internal leakage,
spinal cord ischemia, and stroke in discharged patients.
5 DISCUSSIONS
Circulatory management is essential in aortic arch surgery. Total aortic
arch replacement surgery may cause many complications (such as the
cerebral or renal ischemia), the main reason is attributed to
insufficient perfusion and severity is positively correlated with
ischemia time5. The conventional Sun’s surgical method
uses unilateral cerebral perfusion by CPB to maintain the perfusion of
the brain, and the reconstruction of arch branches must be performed
under CPB4. Although the other arch-first technique
before us ensured the cerebral perfusion or reduced time, they were
still performed under CPB8–11.
Excessively long CPB and hypothermia also may lead to more
complications, such as the disturbances of the coagulation system and
stroke12–15. In addition, unilateral perfusion must
rely on collateral circulation of the brain. Although the ophthalmic and
leptomeningeal arteries also provide partial perfusion, the main source
of perfusion is the circle of Willis16. But the
anomalies of the circle of Willis are frequent, Merkkola et al. reported
that 22% of the anterior communicating arteries and 46% of the left
posterior communicating arteries were missing17.
The simplified arch-first technique could solve some of problems. The
most remarkable advantage is it shortens the time of CPB and part of the
circulatory arrest time because the reconstruction of the aortic arch
branches is under the autologous bypass, which may reduce the lower body
circulatory arrest relevant and CPB related complications. Meanwhile,
cerebrum blood is supplied by bilateral cerebral perfusion during the
whole operation even at the anastomosis of the left common carotid
artery, which avoids cerebral ischemia caused by incomplete circle of
Willis. In addition, triple aortic arch branches perfusion could reduce
spinal cord injury compared to unilateral cerebral
perfusion18. The left subclavian artery is temporarily
cross-clamped only during anastomosis, the perfusion of left vertebral
artery is continuous at other times, which may minimize the possibility
of neurologic complications.
In addition, due to the reconstruction of the arch branches is done
under the whole brain perfusion, the surgeon has sufficient time to
complete procedures without the limitation of CPB and low body
circulatory arrest. Since the distal and proximal ends of the vascular
graft trunk are not anastomosed, the graft can be moved freely and the
vision of the surgical field is clearer, which is conducive to operation
and hemostasis. Therefore, simplified arch-first technique is a very
friendly innovation to surgeon.
The disadvantages of this technique include increased complexity of
cannulation and may obscuring the operative field. Meanwhile, this
technique has higher requirements for trimming the length of the
four-branched vascular graft. If the vascular graft is too long, it will
be twisted and the lumen will be narrowed. On the other hand, it will
cause the anastomotic stoma to be too tight and incontrollable bleeding
if the graft is too short. Hence, the spatial imagination of the surgeon
is required. It is necessary to carefully read the CT before surgery and
repeatedly study the three-dimensional spatial images of thoracic, heart
and aorta to preliminarily estimate and measure the site of vessel
reconstruction and the length of the vascular graft, which is critical
for the trim and placement of the graft during surgery.
CONCLUSIONS
Simplified arch-first technique can significantly shorten CPB, aortic
cross-clamping and deep hypothermic circulatory arrest time. Although
unproven, this technique could theoretically provide better cerebral
perfusion. Simplified arch-first technique has good clinical and
short-term follow-up outcomes, and it is non-inferior to conventional
aortic dissection surgery. It can be predicted that this
operator-friendly technique is expected to provide new improvements and
development directions for the surgical options of aortic arch
replacement.