State-of-the-Art Surgical Management of Acute Type A - Ping-Pong

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Canadian Journal of Cardiology
-
(2015) 1e10
Review
State-of-the-Art Surgical Management of Acute Type A
Aortic Dissection
Ismail El-Hamamsy, MD, PhD,a Maral Ouzounian, MD, PhD,b Philippe Demers, MD,a
Scott McClure, MD,c Ansar Hassan, MD, PhD,d Francois Dagenais, MD,e
Michael W.A. Chu, MD,f Zlatko Pozeg, MD,g John Bozinovski, MD, MSc,h
Mark D. Peterson, MD, PhD,i Munir Boodhwani, MD, MMSc,j Roderick G.G. McArthur, MD,k
and Jehangir J. Appoo, MDCM;l on behalf of the Canadian Thoracic Aortic Collaborative (CTAC)*
a
b
Division of Cardiac Surgery Montreal Heart Institute, University of Montreal, Quebec, Canada
Division of Cardiac Surgery, Peter Munk Cardiac Centre, University of Toronto, Ontario, Canada
c
d
Division of Cardiac Surgery, Kingston General Hospital, Queen’s University, Ontario, Canada
Department of Cardiac Surgery, New Brunswick Heart Centre, Saint John, New Brunswick, Canada
e
Division of Cardiac Surgery, Quebec Heart and Lung Institute, Que bec City, Que bec, Canada
f
g
h
Division of Cardiac Surgery, University of Western Ontario, London, Ontario, Canada
Division of Cardiac Surgery, St Boniface Hospital, University of Winnipeg, Manitoba, Canada
Division of Cardiac Surgery, Royal Jubilee Hospital, University of British Columbia, Victoria, British Columbia, Canada
i
j
Division of Cardiac Surgery, St Michael’s Hospital, University of Toronto, Ontario, Canada
Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
k
l
Division of Cardiac Surgery, University of Alberta, Edmonton, Alberta, Canada
Division of Cardiac Surgery, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada
ABSTRACT
RESUM
E
Acute type A aortic dissections still present a major challenge to cardiac surgeons. Although surgical management remains the gold
standard, operative mortality remains high, including in experienced
centres. Nevertheless, recent advances in the understanding and
management of various aspects of these complex operations are expected to improve overall patient outcomes. The Canadian Thoracic
Aortic Collaborative (CTAC) represents a group of surgeons with interest and expertise in the management of patients with aortic diseases.
The purpose of this state-of-the-art review is to detail our approach to
the contemporary surgical management of acute type A aortic dis-
sentent encore un de
fi
Les dissections aortiques aiguës de type A repre
important pour les chirurgiens cardiaques. Bien que la prise en charge
talon or, la mortalite
ope
ratoire demeure
chirurgicale demeure l’e
leve
e, y compris dans les centres spe
cialise
s. Ne
anmoins, les
e
centes avance
es en matière de compre
hension et de prise en charge
re
rations complexes devraient ame
liorer
des divers aspects de ces ope
sultats cliniques globaux des patients. Le CTAC (Canadian
les re
sente un groupe de chirurgiens qui
Thoracic Aortic Collaborative) repre
rêt et une expertise dans la prise en charge des patients
ont un inte
souffrant de maladies aortiques. L’objectif de cette revue de pointe
Received for publication June 1, 2015. Accepted July 29, 2015.
*Members of the Canadian Thoracic Aortic Collaborative (CTAC) are
listed in Supplemental Appendix S1.
Corresponding author: Dr Ismail El-Hamamsy, Division of Cardiac
Surgery, Co-Director, Aortic and Connective Tissue Clinic, Montreal Heart
Institute, Universite de Montreal. 5000, Belanger E, Montreal, Quebec,
Canada, H1T 1C8. Tel.: þ1-514-376-3330 (ext. 3715); fax: þ1-514-5932157.
E-mail: [email protected]
See page 8 for disclosure information.
Operative mortality remains high in patients presenting with
acute type A aortic dissection. However, recent advances in
the understanding and management of various aspects of these
complex operations are expected to improve overall patient
outcomes. The purpose of this state-of-the-art review is to
detail the contemporary surgical management of acute type A
aortic dissection. We focus specifically on cannulation strategies, cerebral protection, and extent of proximal and distal
resection, and discuss specific clinical scenarios such as
http://dx.doi.org/10.1016/j.cjca.2015.07.736
0828-282X/Ó 2015 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.
2
Volume - 2015
sections. We focus specifically on cannulation strategies, cerebral
protection, and extent of proximal and distal resection. In addition,
specific clinical scenariosdincluding malperfusion, intramural hematomas, and surgery in octogenariansdare explored.
senter en de
tail notre approche de la prise en charge
est de pre
chirurgicale contemporaine des dissections aortiques aiguës de type A.
gies de canulaNous nous concentrons particulièrement sur les strate
re
brale et l’e
tendue de la re
section proximale et
tion, la protection ce
narios cliniques pre
cis, à savoir
distale. De plus, nous explorons des sce
matomes intramuraux et la chirurgie chez les
la malperfusion, les he
naires.
octoge
malperfusion and intramural hematomas. Although this
document represents a detailed review of the surgical management of acute type A dissection by surgeons across Canada
with a specific interest in the management of aortic pathologic
conditions, these are neither guidelines nor specific
recommendations.
remains one of the main technical challenges of surgical repair
of acute type A aortic dissections because of the friable
dissected aortic tissue and the coagulopathy that may exist
secondary to a number of factors (long cardiopulmonary
bypass times, moderate to deep hypothermia, preoperative
state of the patient, and consumption of coagulation factors by
the dissection process itself).
Surgical Principles
Medical therapy for type A dissection is associated with
60% 30-day mortality; thus, surgical repair is indicated for
most patients presenting with an acute type A aortic dissection.1,2 The primary goal of surgical treatment in patients with
acute type A aortic dissection is to reduce the risk of aortic
rupture or proximal extension of the dissection by replacing the
ascending aorta and proximal arch using a synthetic presealed
woven polyester vascular graft. This also serves to prevent or
correct coronary malperfusion, acute aortic insufficiency, and
cardiac tamponade. In addition, the primary intimal tear,
which can be located in the ascending aorta or the arch, should
be resected or excluded at the time of surgery.
To achieve successful aortic repair, the fragile dissected
aortic layers should be reconstituted proximally and distally by
meticulous use of fine continuous or interrupted sutures, with
or without reinforcement, to obliterate the false lumen. The
result is the redirection of aortic blood flow into the true aortic
lumen both proximally and distally, thus increasing the likelihood of reperfusion of aortic branches previously compromised by static or dynamic obstruction.
When aortic valve regurgitation is present, aortic valve
competence is often achieved through reconstruction of the
sinuses of Valsalva with resuspension of the commissures.3
Nevertheless, depending on involvement of the aortic root,
the discovery of a pre-existing aortic root aneurysm, or the
presence of underlying connective tissue disorders, complete
aortic root replacement with reimplantation of the coronary
ostia is often indicated. Separate aortic valve replacement and
supracoronary aortic graft replacement is now rarely used in
patients with acute type A aortic dissections but may be
appropriate in very selected high-risk patients in whom the
sinuses can be spared but aortic valve competence cannot be
achieved using other techniques.
In almost all cases, a brief period of deep hypothermic
circulatory arrest is used to allow direct inspection of the aortic
arch and secure distal aortic reconstruction of a portion of
(hemiarch repair) or the entire aortic arch using the elephant
trunk technique or one of its variants.4 Furthermore, to ensure
adequate blood flow to various parts of the body before,
during, and after repair, arterial pressure in the right and left
radial arteries as well as the femoral artery should be monitored throughout the case. Finally, satisfactory hemostasis
Cannulation Strategies
Several arterial cannulation strategies have been advocated
in the operative management of acute type A aortic dissection.
Currently these include femoral, right axillary, left axillary,
central aortic, and, less commonly, apical cannulation. The
choice of cannulation site is dictated by patient-specific factors, including extent of dissection and whether or not a potential cannulation site is involved, presence of malperfusion,
hemodynamic instability (shock or tamponade), age, peripheral vascular disease, and a history of stroke.
For years, the femoral artery has served as the cannulation
site of choice for many surgeons, including those with expertise
in aortic surgery.5 Accessing the femoral vessels is fairly easy and
allows for the rapid institution of cardiopulmonary bypass in
hemodynamically unstable patients. However, there is a potential risk of retrograde embolization, stroke, and malperfusion
with femoral artery cannulation. In addition, use of the femoral
artery implies using either isolated deep hypothermic circulatory arrest or separate cannulation of the head vessels during
circulatory arrest to achieve cerebral flow.
Recent studies, however, have suggested a benefit of right
axillary artery cannulation with respect to short- and longterm outcomes after aortic arch surgery.6,7 Whenever
possible, we consider the right axillary artery as the cannulation site of choice. The right axillary artery is uncommonly
affected by the acute dissection process or pre-existing
atherosclerotic disease and may be cannulated either directly
or by sewing an end-to-side 8- or 10-mm polyester graft to the
artery. Right axillary cannulation lowers the risk associated
with retrograde aortic flow and its attendant complications
and facilitates the use of selective antegrade cerebral perfusion.
However, this technique may be time-consuming, especially
in obese patients, and this should be weighed against the
urgency of the operation. In addition, injury to the brachial
plexus, arm hyperperfusion, or seroma formation, although
rare in experienced hands, are potential complications. Use of
the innominate artery, provided that it is not dissected, offers
advantages similar to those of the right axillary artery while
eliminating some of the concerns over the added length of the
procedure.8
Alternative approaches for arterial cannulation include
direct aortic cannulation under echographic guidance using a
El-Hamamsy et al.
Surgical Management of Acute Type A Aortic Dissection
Seldinger technique,9,10 as well as transapical cannulation.
None of these techniques is recommended as the initial cannulation strategy of choice.
Independent of which cannulation site is chosen, intraoperative transesophageal echocardiographic imaging plays a
central role in determining the direction and distribution of
flow between true and false lumens. The adequacy of true
lumen perfusion may be inferred by monitoring the flow in
the arch and thoracic descending aorta before and immediately after initiating cardiopulmonary bypass. Additionally,
adequacy of brain perfusion may be monitored through either
cerebral oximetry or transcranial Doppler assessment of the
middle cerebral artery.
Cerebral Protection
Deep hypothermia and circulatory arrest at systemic temperatures between 15 and 20 C has traditionally been the
cornerstone of neuroprotection in aortic surgery. Deep hypothermia affords 20-30 minutes of safe cerebral anoxia,11
which is often sufficient to complete an open distal or hemiarch repair. Increased cerebral ischemic times beyond 30
minutes, without adjunct cerebral perfusion, are associated
with an increased risk of neurological injury.
Retrograde cerebral perfusion through the internal jugular
vein was originally proposed as an alternative means of supplying blood flow to the brain during circulatory arrest.
However, concerns over “precerebral steal” through collaterals
and cerebral edema secondary to high-pressure flow have
limited its use.12 Currently, the sole indication for retrograde
cerebral perfusion is to flush debris and air from the brachiocephalic vessels whenever embolic events are suspected.
Selective antegrade cerebral perfusion has emerged as the
preferred method of adjunct cerebral protection. Its use is
made simpler through axillary or innominate cannulation, in
which a clamp or occluding loop is placed at the origin of the
innominate artery, thus allowing antegrade flow through the
right common carotid artery at a rate of 10-15 mL/kg/min.
Retrograde flow through the left carotid artery and an increase
in left-sided brain oximetry as a result of this technique are
suggestive of distribution of blood flow into both hemispheres. In a significant number of individuals, however, the
circle of Willis is not fully developed, and uneven flow may
result.13 In these circumstances, direct cannulation of the left
carotid artery using a balloon-tipped catheter may provide
more homogeneous blood supply to the brain. With most
corrective aortic repair procedures being completed within 45
minutes, no clear benefit has been shown with bilateral vs
unilateral antegrade techniques.14,15 Nevertheless, when systemic circulatory arrest is expected to extend beyond 45 minutes or when cerebral oximetry indicates poor perfusion to
the left side of the brain after initiation of unilateral antegrade
perfusion, a bilateral antegrade approach may be beneficial to
further optimize cerebral perfusion.
Routine use of selective antegrade cerebral perfusion has
led to a shift toward moderate hypothermia (21 -28 C) over
deep hypothermic circulatory arrest (15 -20 C). Moderate
hypothermia allows for shorter cooling and rewarming times,
thereby reducing overall cardiopulmonary bypass times. In
addition, it potentially reduces the incidence of severe coagulopathy and systemic inflammatory response often observed
3
with deep hypothermia and prolonged cardiopulmonary
bypass times. Reports of systematic use of moderate hypothermia with selective antegrade cerebral perfusion in acute
type A dissection suggest the safety and efficacy of this strategy.16,17 However, one must consider the risk of spinal cord
ischemia at warmer temperatures, especially with prolonged
periods of circulatory arrest.
Management of the Aortic Root
Although the primary tear is often distal to the sinotubular
junction in acute type A aortic dissections, the dissection
process may extend into the aortic root to the level of the
coronary ostia. The traditional approach, aimed at reducing
the complexity and length of the operation, has been to
replace the supracoronary aorta in conjunction with
commissural resuspension (with or without separate aortic
valve replacement), thus leaving the native sinuses of Valsalva
intact. Although some studies suggest good freedom from late
proximal reoperation using this strategy,3 more complete
resection of sinus tissue at the time of surgical repair should be
considered in particular cases.
When one or more of the sinuses of Valsalva is severely
damaged by the dissection process, the patient has Marfan
syndrome or other connective tissue disorder, a large root
aneurysm is present, the patient has severe annuloaortic
ectasia, or the valve needs to be replaced for other reasons
(such as moderate-severe aortic stenosis), complete aortic root
replacement with reimplantation of the coronary ostia is
indicated. This may be accomplished using either a composite
valve graft or a valve-sparing aortic root replacement technique, as described by Yacoub et al.18 and David and Feindel.19
When the involvement of the aortic root is limited to the
noncoronary sinus of Valsalva, isolated replacement of the
noncoronary sinus of Valsalva in conjunction with replacement of the tubular ascending aorta (commonly termed a
“uni-Yacoub”) is a simple technique that may be adequate.
In the setting of acute aortic dissection in young patients
with normal valve leaflets, valve-sparing aortic root replacement using David and Feindel’s reimplantation technique
might be the optimal technique, allowing for complete
removal of all diseased tissue and a lower incidence of late
reintervention for aortic root or aortic valve problems.20
Recent evidence from experienced centres confirms that
valve-sparing aortic root reconstruction can be performed in
acute type A dissection with good short- and long-term
outcomes.21-24
Occasionally, the origins of the coronary arteries, in
particular that of the right coronary artery, may be severely
dissected to the point that direct reimplantation of one or
more these ostia may be technically difficult and compromise
myocardial blood flow. In these situations, direct ligation of
the affected ostium in combination with one or more bypass
grafts might be considered as an option.
Management of the Aortic Arch and Extent of
Aortic Treatment
The optimal management of the aortic arch in an acute
type A aortic dissection is highly variable and should be
tailored to the patient’s clinical presentation, the anatomy of
4
the arch, and distal aortic anatomy. Important anatomic details to consider include the location and extent of the intimal
tear, the size of the aortic arch and distal aorta, collapse of the
distal true lumen, and the presence of dynamic or static
obstruction of the branch vessels of the aortic arch or distal
aorta.
Standard hemiarch replacement
For patients with a tear localized to the ascending aorta
who have a normal-caliber aortic arch without distal malperfusion, the standard surgical repair involves a hemiarch
replacement with an open distal anastomosis under circulatory
arrest (Fig. 1). This repair mandates direct inspection of the
aortic arch and the orifices of the arch vessels to ensure the
absence of distal tears. Elimination of proximal aortic tissue up
to the orifice of the innominate artery and an aggressive bevel
of the lesser curvature of the arch extending distally to the
level of the ligamentum arteriosum are the hallmarks of a true
hemiarch repair. Unfortunately, the term has been used quite
liberally over the years, and in many reports includes simple
open distal anastomoses at the origin of the innominate artery,
Volume - 2015
leaving ascending aortic tissue at risk of future dilatation or
dissection. Although the standard hemiarch repair is often
curative for dissections limited to the ascending aorta and
proximal arch, this repair requires long-termesurveillance
imaging in patients with more extensive arch and descending
thoracic aortic involvement to ensure stability of the distal
aorta, particularly during the early postoperative period.
Although more limited repairs of the ascending aorta performed with the clamp in place have historically been
described, these should be avoided because they do not allow
for direct inspection of the arch and invariably leave a remnant
of diseased ascending aorta.
Total arch replacement
The standard indications for a total arch replacement in an
acute dissection include the presence of an extensive intimal
tear throughout the arch and arch vessels that is not amenable
to primary resection and dilatation of the arch. Although no
strict size criteria for replacement have been established, we
suggest that an arch with a caliber of > 45 mm should be
given consideration for replacement at the time of initial
repair. This, however, should be tailored to each patient based
on several criteria, including clinical presentation, patient age,
surgeon experience, and cannulation strategy. The island or
en-bloc technique for reimplantation of the arch branch vessels is often problematic in an acute dissection because of the
poor quality of the dissected tissues or the presence of a tear
along the greater curvature of the arch, or both. The integrated 4-branched graft technique of Kazui et al.25 or the
trifurcated or Y-graft technique proposed by Spielvogel et al.26
have become the preferred approaches for managing the
supra-aortic vessels in an acute dissection. Although reimplantation or extra-anatomic bypass of the left subclavian artery is desirable, it may be ligated if it is not easily accessible as
long as the left vertebral artery is not felt to be a dominant
vessel based on preoperative imaging.
Beyond the arch
Figure 1. Standard surgical repair involving hemiarch replacement
and open distal anastomosis under circulatory arrest for patients with
tears localized to the ascending aorta, a normal caliber aortic arch,
and no evidence of distal malperfusion. Image courtesy of Dr Jehangir
Appoo. Reproduced with permission.
In addition to the standard indications for total arch and
more extensive distal repairs described here, one may consider
an extended distal repair to improve early and late outcomes
after acute type A aortic dissection. The goals of an extended
distal repair are to seal tears extending beyond the transverse
arch and to improve obliteration of the false lumen of the
thoracic aorta. Theoretical benefits include a reduction in
early malperfusion and prevention of late distal aortic dilatation, reintervention, and mortality. Although we do not
advocate wide use of this approach in patients with acute type
A dissections because of its inherent risks and complexity, in
centres with adequate expertise, it may be reasonable to
consider an extended distal repair in the following circumstances: evidence of distal malperfusion, presence of primary
intimal tear in the distal arch or descending aorta, young
patients, and dilated arch or descending thoracic aorta in
patients with known connective tissue disorders.
The distal anastomosis may be constructed with or without
an elephant trunk (classic or frozen), depending on the size of
the overall aorta as well as the size of the true lumen beyond
the arch. The classic elephant trunk is facilitated by the use of a
collared graft that permits tailoring of the skirt to match the
El-Hamamsy et al.
caliber of the arch as well as displacement of the distal anastomosis to a more technically facile proximal location between
the left common carotid and left subclavian arteries. The
frozen elephant trunk involves the deployment of a distal
endovascular stent graft in the true lumen at the time of circulatory arrest. This is usually performed without direct
visualization of the distal landing zone and may be done over a
wire. There are multiple emerging techniques using a frozen
elephant trunk for the treatment of acute type A aortic
dissection that vary regarding the extent of arch replacement
and the method of stent graft deployment.27 These techniques
5
are depicted in Figure 2 and may be classified into 2 broad
categories based on whether the stent graft is deployed
through an open arch during circulatory arrest (open stent
graft) or with the aid of intraoperative fluoroscopy after
termination of cardiopulmonary bypass. Irrespective of
whether the classic or frozen elephant trunk is used, a remnant
or a delayed-onset distal aortic pathologic condition may
necessitate a second-stage open or endovascular completion
repair.
Prospective trials of extended aortic repair vs hemiarch
replacement are currently not available. The studies that do
Figure 2. (A) Open stent graft and total arch replacement with antegrade stent graft placed in the descending thoracic aorta at time of circulatory
arrest. (B) Open stent graft and hemiarch replacement with antegrade stent graft placed in the descending thoracic aorta at time of circulatory
arrest. (C) Closed stent graft with hybrid arch. Proximal rerouting of arch vessels to sinotubular junction and endovascular stent graft deployment
into ascending aortic graft with fluoroscopy after weaning from cardiopulmonary bypass. (D) Closed stent graft with hybrid arch replacement. Arch
replaced surgically to the level of left subclavian artery and polyester proximal landing zone created for stent graft in transverse arch. Images
courtesy of Dr Jehangir Appoo. Reproduced with permission.
6
Volume - 2015
Table 1. Review of publications for extended distal repair of acute type a dissection
Author (reference)
Year
Yun et al.34
Kazui et al.35
Takahara et al.36
Ohtsubo et al.31
Watanuki et al.37
Kim et al.38
Mizuno et al.39
Tsagakis et al.40
Ma et al.41
Katayama et al.42
Roselli et al.43
Pan et al.44
Chen et al.45
Preventza et al.46
Vallabhajosyula et al.47
Diethrich et al.48
Marullo et al.49
Kent et al.50
Chang et al.51
1991
2000
2002
2002
2007
2011
2002
2010
2013
2015
2013
2013
2014
2014
2014
2005
2010
2012
2013
Type of repair
Total arch
Total arch
Total arch
Total arch
Total arch
Total arch
Open stent graft and
Closed stent graft
Closed stent graft
Closed stent graft
Closed stent graft
total arch
total arch
total arch
total arch
hemiarch
hemiarch
hemiarch
hemiarch
hemiarch
N
30-day/in-hospital
mortality (%)
Permanent
stroke (%)
Permanent SCI (%)
7
70
37
24
54
44
9
68
398
120
17
27
122
25
62
1
15
1
21
29
16
8.1
33.3
3.7
13.4
11.1
13
7.8
6
0
0
4.93
12
14
0
4.2
0
4.8
NA
2.9
0
12.5
5.6
15.9
11.1
10
2.5
3
0
0
0
12
8
0
0
0
0
NA
1.4
0
NA
0
2.3
22.2
1
2.5
2
0
0
0
0
1
0
0
0
0
NA, not applicable; SCI, spinal cord ischemia.
exist are inherently small, prone to bias, and confounded by
dissimilar repair techniques and heterogeneous patient
populations,28-33 thus making comparisons of these techniques challenging. Table 1 presents a summary of the
contemporary results of extended distal repair for type A
dissection.
Dealing with malperfusion
End-organ malperfusion is reported in 18%-33% of patients with acute type A aortic dissections.52 Malperfusion
may involve all major aortic branches and thus potentially
result in coronary, brain, spinal cord, visceral organ, or limb
ischemia. In patients with advanced age and hemodynamic
instability on arrival, malperfusion constitutes one of the
major risk factors for mortality in acute type A aortic dissection.53 A high index of suspicion for malperfusion is critical to
identify it, both on clinical examination and imaging studies.
This should be done before surgery and regularly thereafter to
rule out signs of new-onset malperfusion, a frequent cause of
perioperative mortality in patients with acute type A dissection. On physical examination, focal neurological changes,
paraplegia, a distended and tender abdomen, discordant blood
pressure readings, or pulseless extremities are all suggestive of
malperfusion. The electrocardiogram may demonstrate signs
of myocardial ischemia. The absence of arterial organ branch
perfusion on preoperative computed tomographic imaging is
greatly indicative of malperfusion.
Malperfusion may be described as dynamic, static, or
mixed. In dynamic malperfusion, which is the most frequent
type, the overpressurized false lumen pushes the septum
toward the true lumen and may ultimately collapse the true
lumen and obstruct the origin of one or more arterial
branches. When true lumen collapse occurs above the level
of the diaphragm, a pseudocoarctation or aortic obstruction
occurs, resulting in dynamic distal organ malperfusion.
Conversely, static malperfusion results from stenosis or occlusion of an organ arterial branch owing to a local process
within the organ artery, such as dissection, intramural hematoma, or thrombosis.
Dynamic malperfusion is treated by resecting the primary
intimal tear and redirecting the flow toward the true lumen.
Static malperfusion, in contrast, will persist despite resection
of the primary intimal tear and restoration of arterial flow in
the true lumen. Owing to the complexity of the dissection,
the site of the primary intimal tear, and the cannulation site
selected, one may encounter malperfusion after initiation of
cardiopulmonary bypass. Electrocardiographic tracings, cerebral saturation, upper and lower extremity blood pressure,
and true lumen size on intraoperative transesophageal
echocardiography should be closely monitored after initiation of cardiopulmonary bypass. In the event of significant
changes, malperfusion induced by cardiopulmonary bypass
flow should be suspected, the patient should be weaned from
cardiopulmonary bypass if possible, and an alternative or
additional arterial cannulation site should be sought. Studies
suggest that perfusion through the right axillary artery offers
better true lumen flow. However, an incidence of malperfusion of 3.5% has been reported in patients with right
axillary cannulation, especially when the right subclavian
artery is dissected.54
In patients with preoperative malperfusion, restoration of
organ blood flow should be assessed immediately after
completion of the operation. With the widespread establishment of hybrid operating rooms, one may consider opting for
a completion angiogram in such situations. It should be noted
that in most instances, malperfusion resolves with removal of
the intimal tear and re-establishment of the true lumen. In the
event that malperfusion persists, branch stenting or extraanatomic bypass should be considered emergently.
Management of cerebral malperfusion with clinical manifestations of stroke or coma remains controversial. Pocar
et al.55 reported recovery of 4 of 5 patients with preoperative
coma. Similarly, in 14 patients with preoperative stroke,
Estrera et al.56 showed postoperative recovery in 8 cases. To
enhance brain flow restoration in patients with common
El-Hamamsy et al.
carotid occlusions, Luehr et al.57 proposed early extraanatomic bypass. Therefore, the presence of coma or stroke
preoperatively should not represent a contraindication to
surgery. However, documentation of hemorrhagic stroke on
brain computed tomography, a prolonged time from initial
presentation to surgery, or the presence of significant
concomitant comorbidities, such as advanced age, further
increase the operative risk and should be considered when
determining whether or not to offer an operation.58
Occasionally, a patient may present with signs of severe
malperfusion with elevated serum lactate levels.59 Two
clinical scenarios may be associated with this clinical presentation: severe pseudocoarctation of the descending aorta
or mesenteric ischemia. Although proceeding with the
standard repair of the acute type A aortic dissection is
feasible, the operative mortality is very high in the presence
of severe malperfusion with associated end-organ ischemia.
An initial nonoperative endovascular-based approach has
recently been proposed by some centres. Use of covered
stents within the true lumen of the descending aorta or
uncovered stents within the true lumen of the visceral
segment may serve to increase the size of the true lumen and
resolve the aortic pseudocoarctation.60 In addition, visceral
branch stenting, with or without endovascular fenestration,
has been advocated by some to relieve severe mesenteric
malperfusion owing to static obstruction of the mesenteric
vessels.61 Open abdominal fenestration has essentially been
abandoned in light of the significant advancements in
endovascular therapies. Once the organ perfusion has been
restored, a “reperfusion period” is allowed to evaluate recovery of the affected organs. Nevertheless, a “malperfusion
first” endovascular approach is technically challenging and
dependent on the presence of experienced operators.
Importantly, it results in delays in definitive surgical repair
of the dissection, with interim ruptures reported at rates
between 5% and 23%.62 Therefore, we still favour early
surgical repair in these patients if they are considered candidates for surgery.
Special Considerations
Intramural hematoma
In the ascending aorta, intramural hematomas (IMHs)
result from rupture of the vasa vasorum within the outer third
of the aortic media, allowing for accumulation of blood or
clot, or both, within the aortic wall in the absence of an
intimal defect.63,64 In most centres in North America and
Europe, patients presenting with acute type A IMH are
managed identically to those with acute type A aortic dissection because of the high risk of complications in these
patients.64-66 The rationale behind this approach is to prevent
rupture and cardiac tamponade as well as to reduce the risk of
IMHs evolving into a classic aortic dissection.64 This
approach has been challenged by some, particularly in Asia,
where medical therapy is advocated for selected patients with
uncomplicated acute type A IMH.67,68 If a patient with acute
type A IMH is treated medically, early monitoring in the
intensive care unit followed by close serial imaging studies is
mandatory for the first year after the event.
7
Surgery in octogenarians
In the past decade, some authors have reported prohibitively high mortality rates with surgical treatment of acute
type A aortic dissection in octogenarians, as well as poor
functional status in survivors,69 prompting a debate regarding
appropriateness of surgery in these patients.70 In contrast,
several expert centres have reported excellent survival and
quality of life in selected octogenarians.71,72 According to
recent International Registry of Acute Aortic Dissection data,
< 50% of patients > 80 years with acute type A aortic
dissection are treated surgically. In the registry, mortality was
significantly lower in octogenarians treated surgically
compared with those managed medically.73 Currently, we
believe that age alone is not a contraindication for surgery.
These patients should be treated surgically unless shock,
malperfusion, or significant comorbidities are present.66,74
Known or suspected coronary artery disease
Patients with atherosclerotic risk factors are at higher risk
for concomitant coronary artery disease. Although it may be
known, in most cases it can only be suspected at the time of
presentation. A preoperative coronary angiogram is not recommended because it can delay surgical intervention, but
more importantly, using wires in the aorta down to the root
can extend the dissection or cause entry tears, including into
the coronary ostia. If a preoperative computed tomographic
scan is available, the presence or absence of calcium in the
coronary tree is a helpful adjunct, along with any corresponding regional wall motion abnormalities on intraoperative
transesophageal echocardiography. When in doubt, concomitant coronary artery bypass grafting using saphenous vein
grafts is a safe and effective approach.
Dedicated aortic teams
Although some large-volume institutions have developed
special expertise and significant experience in caring for patients with diseases of the thoracic aorta that have translated
into excellent surgical outcomes, acute type A aortic dissection
has continued to challenge cardiovascular surgeons, with an
in-hospital mortality risk still ranging from 15%-30%.74
Positive volume-outcome relationships have been consistently demonstrated in cardiac surgery.74,75 Two recent reports using the US Nationwide Inpatient Sample showed an
inverse relationship between hospital/surgeon volume and
operative mortality for patients with acute type A aortic
dissection.76,77 These findings were corroborated by results
from individual centres in which aortic surgery was managed
by a dedicated team, thus resulting in significant improvements in early outcomes, especially in the treatment of acute
type A aortic dissections.78,79 These data represent compelling
evidence toward the concept of concentrating aortic surgical
activity to a limited number of surgeons dedicated to the
study and management of patients with aortic pathologies,
which should translate into more tailored care and better
outcomes. It also raises an important question about the role
of air evacuation of patients with acute type A dissections to
centres of expertise. Although delaying surgery to transfer the
patient may put some at risk, the overall risk/benefit balance
8
Volume - 2015
likely weighs in favour of more centralized care in dedicated
centres.
12. Ehrlich MP, Hagl C, McCullough JN, et al. Retrograde cerebral perfusion provides negligible flow through brain capillaries in the pig. J Thorac
Cardiovasc Surg 2001;122:331-8.
Conclusions
In conclusion, although the surgical principles of acute
type A dissection remain unchanged, the surgical techniques
have evolved over the years and will continue to do so as
endovascular technologies evolve. Although there may be
some differences in specific management strategies, we, the
Canadian Thoracic Aortic Collaborative, believe at this time
that the outlined principles correspond to the state-of-the-art
management of acute type A aortic dissections.
13. Papantchev V, Stoinova V, Aleksandrova A, et al. The role of Willis circle
variations during unilateral selective cerebral perfusion: a study of 500
circles. Eur J Cardiothorac Surg 2013;44:743-53.
Acknowledgements
The authors would like to thank Mr Mark Cromwell for
his invaluable help with the medical illustrations in this
manuscript.
16. Comas GM, Leshnower BG, Halkos ME, et al. Acute type A dissection:
impact of antegrade cerebral perfusion under moderate hypothermia.
Ann Thorac Surg 2013;96:2135-41.
Disclosures
The authors have no conflicts of interest to disclose.
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Supplementary Material
To access the supplementary material accompanying this
article, visit the online version of the Canadian Journal of
Cardiology at www.onlinecjc.ca and at http://dx.doi.org/10.
1016/j.cjca.2015.07.736.

State-of-the-Art Surgical Management of Acute Type A - Ping-Pong

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