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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3734_Библиотеки_им_академика_М_И_Перельмана
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Management oftheAortic Arch inAcute
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Aortic Dissection Type A
TakashiKunihara andHans-JoachimSchäfers
General Considerations
The goal of surgical treatment of acute aortic dissection is the replacement of the
ascending aorta in order to eliminate the segment that can and will lead to pericardial tamponade. The seemingly “straightforward” operation is performed under
emergency conditions due to the characteristics of acute aortic dissection type A
(AADA). The inherent risks or difculties are related to the disease, i.e. the patient
often presenting in shock, the frequent occurrence and dynamic character of malperfusion of vital organs, and the fragility of the aortic wall. The need for surgery is
clear. Different opinions exist regarding extent of aortic replacement, handling of
the fragile aortic wall, details of cannulation, and cerebral protection. In view of all
differing opinions regarding patient management it must not be forgotten the primary goal is to save the patient’s life.
In this chapter we review the evidence regarding the controversial issues with a
focus on management of the aortic arch and then describe our routine in more detail.
T. Kunihara
Department of Cardiac Surgery, The Jikei University School of Medicine, Tokyo, Japan
H.-J. Schäfers (
Department of Thoracic and Cardiovascular Surgery, Saarland University Medical Center,
Homburg/Saar, Germany
e-mail: h-j.schaefers@uks.eu
J. S. Coselli et al. (eds.), Aortic Dissection and Acute Aortic Syndromes,
https://doi.org/10.1007/978-3-030-66668-2_22
*)
305© Springer Nature Switzerland AG 2021
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T. Kunihara and H.-J. Schäfers
Extent ofAortic Replacement
The primary goal of the operation is to bring the patient out of the operating room
and hospital alive. A second goal is and has been to minimize the probability of later
downstream aortic dilatation; this has long been known to be more frequent if arch
dissection and a patent false lumen persist.
Traditionally, this operation has been performed as replacement of the tubular
ascending aorta with a cross clamp placed just below the brachiocephalic trunk [1].
Later it was proposed to perform the aortic replacement with an open anastomosis,
i.e. include the proximal arch in the replaced aortic segment (Fig.1) [2, 3]. The early
mortality for limited replacement of the ascending aorta has been 7–25%, and that
for proximal arch replacement 9–22% [2–10]. The mortality has apparently been
mostly related to patient-specic risk factors, such as preoperative shock or the
existence of relevant malperfusion [7, 11–13]. Smaller studies, even an early metaanalysis, did not nd obvious differences in postoperative morbidities and early/late
mortality between open (with deep hypothermia) and closed (with cross-clamp)
distal anastomosis techniques [4–6]. A large registry study (NORCAAD, n = 1134)
showed that patients who were operated by closed technique had worse short- and
mid-term survival than those who had been treated by open anastomosis [7].
The rationale for routine partial arch replacement, which has become the standard in most cardiac surgical units, has been that this eliminates entry tears created
Fig. 1 Partial arch
replacement. Depending
on the location of an entry
or re-entry tear the
replacement of the arch
may be extended in the
convexity of the arch
Management oftheAortic Arch inAcute Aortic Dissection Type A
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by the aortic cross clamp [5]. In addition, it allows inspection of the arch for a possible entry site and its resection. Partial arch replacement seems to reduce the prevalence of a persistent false lumen in the downstream aorta. If the dissection is limited
to the proximal aorta (DeBakey type II), an open arch anastomosis will lead to
complete elimination of dissection by suturing to the non-dissected arch. The positive effects were conrmed in several series [8, 14]. The open distal anastomosis
using hypothermic circulatory arrest with or without cerebral perfusion has become
a standard part of AADA surgery for the majority of western surgeons. In the
German registry circulatory arrest was not used in only 5% of patients, and thus
some form of arch replacement in 95% [15]. Freedom from secondary operations
for progressive dilatation of the downstream aorta is 87–97% at 5 years after the
initial operation [16–21].
Total replacement of the arch has been used rarely in most western series, while
it was proposed on an almost routine basis, primarily by Japanese groups [13, 22–
24] in order to minimize the probability of distal aortic dilatation. Others have been
concerned over an increased risk of mortality and morbidity and employed total
arch replacement rarely [25–28]. Over the years total arch replacement has become
more popular, in part driven by increasing popularity of the frozen elephant trunk
extension [24, 29–32]. In judging the value of the more extensive operation, we
need to keep in mind that operative mortality largely depends on patient characteristics. In previous series, partial arch replacement had at an average an early mortality of 10–15%, while total arch replacement was associated with a higher mortality
of 20% [11, 12].
Total arch replacement may be performed using different technical variants. The
anatomic form of total replacement of the arch with implantation of the aortic island
carrying the orices of the supraaortic vessels (Fig.2) [19, 20, 28, 29, 32, 33] is
feasible also in acute dissection. On the other hand, achieving hemostasis on the
Fig. 2 Total arch replacement in its anatomic form. The island of the aortic arch carrying the orices of the supraaortic branches is implanted in the arch graft
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T. Kunihara and H.-J. Schäfers
distal suture line, i.e. between graft and descending aorta, may be challenging in
acute dissection. The Japanese variant (Fig.3) of this operation includes the distal
anastomosis and three separate grafts connected to the supraaortic branches. The
time required to complete the arch repair is thus longer, but control of the distal
anastomosis is facilitated. The Griepp group suggested a modication, which combines advantages of both approaches (Fig.4). In this technique a smaller graft (e.g.
14 or 16mm) is anastomosed in end-to-side fashion to the island carrying the supraaortic branches. The aortic graft is connected to the descending aorta while the
supraaortic graft is intubated or clamped for antegrade cerebral perfusion. All variants may be combined with a short conventional or frozen elephant trunk [34, 35].
A recent meta-analysis including a large number of Asian patients (42%) revealed
that total arch replacement was performed in 32.3% of all procedures [36]. Total
arch replacement was performed in almost 50% of all operations for cute type A
dissection in 2017in Japan [37]. In the international registry (IRAD), the German
registry (GERAADA), and American database (STS) the frequency of total arch
replacement has been only 26.9%, 16.2%, and 14.1%, respectively [11, 12, 38]. It is
even less than 10% in Italian and Nordic registry; 6.9% and 5.9%, respectively
[39, 40].
One Japanese series demonstrated superior freedom from aortic events after total
arch replacement (83%) compared with ascending aortic replacement (51%) at 9
years [41]. A lower rate of reoperation was observed during 10 years after extensive
repair than proximal repair (5.4% vs 16.9%, P<.05) in another series [42]. Many
other studies have not found any signicant difference in the incidence of late distal
reoperation or major adverse events between aggressive and conservative approach
for the aortic arch [11, 16, 36, 40, 43]. One meta-analysis identied increased incidence of aortic reoperation (proximal or distal unknown) after proximal
Fig. 3 Total arch
replacement with separate
anastomoses of the
supraaortic vessels. It may
or may not be combined
with a limited elephant
trunk extension into the
descending aorta
Management oftheAortic Arch inAcute Aortic Dissection Type A
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SCP
axillary
perfusion
Full systemic
perfusion
309
Fig. 4 Modied total arch replacement. A smaller graft is anastomosed to the island carrying the
orices of the supraaortic branches. This graft can then be perfused in antegrade fashion while total
arch replacement is performed. The two grafts are then connected. The operation may be combined
with a limited elephant trunk extension into the descending aorta
replacement compared with total arch replacement [44]. Failure to exclude the primary entry site was identied as predictor for distal aortic events [45]. On the other
hand, one should keep in mind that elective reoperation for progressive enlargement
of the distal aorta was not necessary in more than 80% of the patients undergoing
proximal arch replacement only; in addition, the complexity of such an elective
procedure is far from that of acute dissection.
This increased complexity is conrmed by a higher early mortality after total
arch replacement in the majority of registries [11, 12, 36], and it was statistically
signicant so in a recent meta-analysis (odds ratio =0.77) [36]. So far, only the
Japanese database shows a different result [37]. It is unclear whether this is related
to the procedure per se or rather differences in patient selection. Total arch replacement is unquestionably associated with longer procedural time [11, 16, 36, 41–44,
46]. Several registries show a similar incidence of postoperative stroke between
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T. Kunihara and H.-J. Schäfers
replacement of the total arch and the ascending aorta [11, 12, 29, 36], while the STS
database and Nordic database report a higher incidence for total arch replacement
[38, 40]. The incidence of postoperative acute renal failure was also increased in
extended arch replacement according to the IRAD data [11]. So far, total arch
replacement has not improved log-term survival [11, 36, 41, 43]; survival seems to
be affected mainly by patient-related factors [43, 45, 46].
The addition of a (frozen) elephant trunk (Fig.5) has been associated with thrombosis of the distal false lumen, at least in the proximal descending aorta [30, 31, 42,
47]. While this technical variant does not prolong cross-clamping time, there is a
prolonged lower-body arrest time [29, 30]. In a meta-analysis thrombosis of the
distal false lumen was seen in 96.8% of cases who were treated with frozen elephant
trunk [29]. Thrombosis rate of the proximal descending aorta was 25–66% after
proximal repair and 82–100% after extended repair with frozen elephant trunk in
single center experiences [31, 42, 47]. It is yet unclear whether this technique indeed
reduces the need for secondary distal aortic replacement sufciently.
Cannulation forExtracorporeal Circulation
Venous cannulation for these procedures is standard. Single venous drainage from
the right atrium using a two-stage cannula is sufcient in essentially all patients. In
unusual instances, venous cannulation through a femoral vein may be used
alternatively.
Fig. 5 Total arch
replacement combined
with a frozen elephant
trunk. In this variant
separate grafts are
connected to the
supraaortic vessels
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Arterial cannulation has undergone changes over time. The femoral artery has
been the traditional cannulation site, and it remains one of the fastest and easiest
sites for arterial cannulation. In 2011–2012, the femoral artery was still the rst
choice of arterial cannulation site for AADA (45.9%), however, the aorta (29.1%)
and the axillary artery (31.0%) were used equally as the second choice in STS database [48]. Retrograde perfusion may, however, decrease cerebral perfusion intraoperatively if the false lumen is perfused preferentially. The potential risk of
malperfusion of other vital organs is also inherent with this adjunct. In order to
minimize these problems, it has been combined with cannulation of the aortic graft
once arch repair was nished in order to establish antegrade perfusion into the true
lumen [2].
In the 2000s, right axillary artery cannulation became popular as an alternative.
Its use in aneurysm surgery has reduced the incidence of embolic cerebral complications [49, 50] by avoiding retrograde ow through an atherosclerotic descending
aorta. In acute dissection, its main advantage lies in the fact that there is probably
better maintenance of blood ow through the right carotid artery. The axillary artery
can be cannulated directly using Seldinger technique [34]. Alternatively, an 8mm
Dacron graft is anastomosed in end-to side fashion to the artery and intubated with
the arterial cannula [51]. After termination of cardiopulmonary bypass this Dacron
graft can simply be oversewn or ligated, thus avoiding potential repair procedure on
the artery itself.
Two meta-analyses published in 2015 found the superiority of axillary artery
cannulation over femoral artery cannulation in reducing early mortality and the incidence of permanent neurological dysfunction [52, 53]. However, one of them failed
to nd clinical benet of axillary artery cannulation in preventing malperfusion
[53]. In 2015, the axillary artery was used as the rst choice of arterial cannulation
site in more than half of European and Canadian patients with acute setting (54%
and 76%, respectively) followed by the femoral artery (28% and 17%, respectively)
[33, 54].
Direct cannulation of the proximal aorta has emerged in recent years [55, 56].
This can easily be done by cannulating the non-dissected arch in type II dissections.
Different approaches have been proposed for cannulation of the dissected arch [57–
59]. The aorta may be cannulated using Seldinger technique guided by epiaortic
ultrasonography or transesophageal echocardiography [57]. The position of the cannula within the true lumen can be conrmed by a guidewire, which is in the true
lumen both in the ascending and descending aorta as judged by echocardiography.
At times the fragility of the aortic tissue may make this form of cannulation difcult. We therefore use it only in selected circumstances.
Some groups cannulate inside the true lumen directly after transection of the
ascending aorta [58, 59]. The senior author has a limited personal experience with
this approach; it has been difcult to ascertain a stable position in the ascending
aorta for controlled perfusion. We therefore do not use this technique. Finally, also
the left ventricular apex has been proposed as cannulation site. In the authors’ experience, this has been difcult, and left ventricular distension may occur in the presence of aortic regurgitation. Even though there have been small studies showing that
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the transapical cannulation is safe [60, 61] it should not be one of the preferred
approaches.
T. Kunihara and H.-J. Schäfers
Cerebral Protection
Any form of arch replacement has to consider the different options of cerebral protection. Deep hypothermia has traditionally been used as the main method of cerebral protection and is probably safe at a nasopharyngeal temperature of 20°C for up
to 20–25min [62, 63]. Different other temperatures have been stated to be followed,
such as rectal, bladder, or tympanic. In interpreting the results of different groups it
is important to look at this in detail; tympanic or nasopharyngeal temperature best
represent brain temperature [64]. A target brain temperature may already be reached
at a bladder temperature of 28°C.
Retrograde perfusion via the superior vena cava has originally been proposed by
a Japanese group [65]. Later studies [66, 67] showed a positive effect in that it
reduced the incidence of embolic cerebral complications. Since it probably does not
provide nutritive blood ow to the brain [68] it can be used as a way of cooling the
head and brain and reducing potential embolic phenomena. Exclusively in patients
with acute aortic dissection who underwent isolated proximal aortic repair, retrograde perfusion was associated with shorter procedural time and similar mortality
and neurological outcome to antegrade fashion [69]. We use it only for that purpose
and commonly employ a ow of 600–1000 ml/min, adjusted to have a central
venous pressure of less than 20mmHg.
More recently, antegrade perfusion of the brain has become a popular means of
cerebral protection. This can be achieved by placing perfusion catheters into the
supraaortic branches. Alternatively, when the right axillary artery is used for arterial
inow, the brachiocephalic trunk may be clamped and a catheter introduced only
into the left carotid artery. Installing such catheters requires a certain time of circulatory arrest [70], so it is commonly used in conjunction with hypothermia.
Antegrade perfusion provides nutritive blood ow to the brain and is the only safe
means of cerebral protection if the time for arch repair exceeds 30min [71, 72].
Management ofDissected Tissue
Traditionally, the biggest challenge in surgery for AADA has been handling of the
fragile tissue and consecutive hemostasis. This changed dramatically when the socalled “French Glue” became available [73]. The glue is injected between the dissected wall layers, which are then adapted with special clamps or bulldog clamps
(Fig.6a, b). While the adhesive capacity of this glue is limited, it resulted in tanning
of the tissue and creation of more normal aortic wall texture. Later Bioglue
(CryoLife, Kennesaw, GA, USA) [74] became available with similar effect. Both
ab
Management oftheAortic Arch inAcute Aortic Dissection Type A
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Fig. 6 (a) The application
of adhesive to the dissected
wall layers improves the
handling characteristics in
acute dissection. Because
of possible local toxicity
the adhesive should be
used sparingly. (b) Using
clamps the aortic wall
layers are adapted until the
adhesive has hardened
Bioglue
313
adhesives have facilitated hemostasis similarly and apparently reduced mortality.
Early series reported that the use of GRF glue decreased in-hospital mortality from
23% to 10.5% [75] or 45% to 21% [76, 77]. The use of Bioglue has been associated
with reductions in postoperative blood loss and hospital length of stay [78].
Due to the limited adhesive effect, this surgical glue has not affected the patency
of the distal false lumen [8, 79]. There have been observations indicating that an
excessive amount of glue may negatively inuence tissue stability, possibly as a
consequence of local tissue necrosis [80, 81]. Therefore, sparing use of such glue
seems advisable.
In order to support the suture line and facilitate hemostasis, an intussusception
(adventitia inversion) technique has been proposed (Fig. 7) [82]. With this technique, the aorta is transected completely, and the dissected media is shortened by
approximately 1cm compared to the adventitia. The adventitia is then invaginated
into the true lumen. In creating the suture line, each bite on the aorta will have
adventitia on the outside and inside. We have explored this technique and found it
easy to use and very hemostatic.
How WeDo It
In view of all knowledge and considerations, we attempt to keep the operations as
simple as possible. This involves standard cannulation, hypothermia, and an open
anastomosis to the arch. We rarely deviate from this standard approach. If the patient
is in shock due to tamponade, the rst procedure is the median sternotomy and limited opening of the pericardium to relieve the tamponade. Blood pressure will
always increase, and anesthesia carefully monitors blood pressure and—if necessary—administers a vasodilator to avoid sudden rupture due to hypertension. This
allows us to rapidly treat hypotension and continue under controlled conditions.
Following a median sternotomy, our standard cannulation involves an 8 mm
Dacron graft sutured to the right axillary artery. A standard arterial cannula is ligated
into the graft. We always use a two-stage, single venous cannula for optimal venous
drainage. Extracorporeal circulation is started, and the core temperature is cooled to
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Fig. 7 Invagination technique without tissue adhesive in acute dissection. Following transection
of the aorta the adventitia is left longer than the media and folded around the media. The aortic
graft is then sutured to the folded aortic edge. A strip of Teon may or may not be used for the arch
suture line
T. Kunihara and H.-J. Schäfers
a nasopharyngeal temperature of 20°C.In cases where the patient’s history (back
pain as initial presentation) or the CT scan indicate a distal location of the entry, we
will cool to a nasopharyngeal temperature of 18°C.If the degree of aortic regurgitation is limited, we will introduce a left atrial vent catheter through the right superior
pulmonary vein when the heart brillates and will continue cooling until the desired
temperature is reached. If aortic regurgitation is severe and the left ventricle is distending upon brillation, we will cross-clamp the aorta and give blood cardioplegia
directly into the coronary ostia. At this time the aorta is carefully inspected for the
location of the entry tear. If it is found in the ascending aorta the procedure is continued according to plan. If there is no entry in the ascending aorta the patient is
cooled to a temperature of 18°C.
Independent of the type of root procedure, extracorporeal circulation is stopped
when the desired nasopharyngeal temperature is reached. With the patient in an
anti-Trendelenburg position the cross-clamp is removed. The distal ascending aorta
is transected approximately 0.5–1cm proximal to the brachiocephalic trunk and the
arch inspected.
If there is an entry in the concavity of the arch it is resected by extending the
aortic transection level to the entry. Similarly, if there is no entry in the arch, the
operation is continued as planned, i.e. a hemi-arch replacement is performed. The
arch tissue is mobilized for 1cm, and Bioglue is administered sparingly. The layers
of the aortic wall are compressed with special clamps (Fig.6b) or strong bulldog
clamps until the glue has become rm. The chosen Dacron graft is then obliquely
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