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conservative measures such as hydration, analgesics, caffeine, and patient positioning. More severe cases can be managed
with an epidural blood patch [19].
The second part of the equation for maximizing spinal perfusion pressure is to maintain an elevated MAP. This is important both intra- and postoperatively. We target a MAP of 85–90 mmHg in the majority of cases. This artificial hypertension
is achieved by a combination of blood and fluid resuscitation with vasoactive medications. The elevated MAP helps promote blood flow to the spinal cord through collateral channels. After the first 72 h, the collateral circulation has had some
time to mature and we typically allow a slightly lower target MAP of 80–85 mmHg.
We routinely use an “open distal” technique in which a proximal cross-clamp is placed but the distal aorta is left open.
The exception is during periods of left heart bypass when a distal cross-clamp is required. The open distal aorta is thought
to allow free drainage of blood from the lower body, intercostal arteries, and lumbar arteries, which lowers the CSF and
central venous pressures [20]. Shed blood from the distal aortic stump is reinfused with a combination of a cell salvage
device and rapid infuser. During these periods of high-blood loss and turnover, the blood is directly reinfused without washing. Although there was initially some fear of coagulopathy and blood cell shearing with this technique, those fears have
not been substantialized [21].
Partial bypass or left heart bypass is an important adjunct for spinal cord protection, especially in more complicated
cases. Perfusion of the lower body and lower intercostal arteries can benefit those in whom a long ischemic time is expected,
such as extent II aneurysms, chronic dissections with many large patent intercostal arteries, and acute dissections [5].
During the proximal anastomosis, partial bypass allows perfusion of the lower sets of intercostal arteries, lumbar arteries,
reno-visceral arteries, and the lower extremities. Because a large proportion of the body is perfused during the cross-clamp
time, the postprocedural reperfusion injury and associated hypotension are reduced. This allows for a smoother postoperative hemodynamic recovery.
The spinal cord blood supply is dependent on a highly variable collateral network, which is partially dependent
on the intercostal and lumbar segmental arteries and branches of the internal iliac and vertebral arteries. The artery of
Adamkiewicz is thought to arise in the T7-L1 region in most people, although it is often not identifiable. During TAAA
repair, often multiple pairs of segmental arteries must be sacrificed. Although some have questioned the importance of
intercostal reimplantation [22,23], the majority of groups have found significant benefit to reimplanting patent intercostal arteries [24]. Many surgeons routinely attempt to reimplant sets of intercostal arteries in the T10-T12 region in
an effort to minimize risk of permanent ischemic SCI. A balance must be struck between the number of reimplanted
pairs, the time it takes to perform the reimplantation, and the risk of intercostal patch aneurysm in the future. Several
techniques can be used to perform the reimplantation. With DTA and extent I TAAA, the intercostal arteries can often
be beveled in and combined with the distal aortic suture line. Otherwise, a patch reimplantation of one to two sets of
intercostal arteries can be made in the side of the aortic graft prior to performing the distal anastomosis. Attempts have
been made to simplify intercostal reimplantation by using a separate side-arm interposition graft but the patency rate
was significantly lower with the interposition graft technique compared to the patch technique [25]. This may be due to
the low flow and slow runoff of the spinal collateral system. The patch technique maintains the intercostal arteries in the
high-flow, high-pressure aortic conduit.
Methods to Reduce Spinal Cord Metabolism
Hypothermia itself provides neurologic and end-organ protection by decreasing the metabolic rate of the tissues. It is used
in varying degrees for protection during routine cardiac and circulatory arrest cases. Profound hypothermia is a proven
method of cerebral protection, which allows for a period absent of circulation to the brain while the aortic arch is reconstructed [26]. The same principles can be applied to the neurons in the spinal cord. For cases performed using a clamp-andsew technique or with left heart bypass, the patient’s body is allowed to passively cool to 33–34°C. The open chest and
abdominal cavities in a cold operating room are adequate for this purpose.
Some groups use DHCA as their primary strategy for repair of DTA and TAAA. DHCA can provide protection for the
central nervous system, heart, and visceral organs by cooling the entire body to 18°C. It also eliminates the need for other
adjuncts such as monitoring motor-evoked potentials of renal/visceral perfusion. Kouchoukos has achieved an SCI rate of
5.3% and 30-day mortality of 7.8% using this technique [12], similar to series of other groups using different combinations
of adjunctive protection. Sundt has used a similar technique with a mortality of 10% and only one patient with delayed
SCI. However, 11% of patients had strokes [27]. The preference at our center is to use DHCA only when necessary, such
as when the arch is aneurysmal or if we are unable to obtain proximal aortic control with a cross-clamp. This allows us to
decrease the operative time and it avoids the coagulopathy and bleeding that can be associated with deep hypothermia and
extensive dissection in the retroperitoneum.
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Intrathecal administration of papaverine has been used by the Cleveland Clinic group as part of their spinal protective
strategy. Intrathecal papaverine vasodilates the spinal collateral network and anterior spinal artery resulting in increased
spinal cord blood flow. A CSF drain must be placed prior to surgery and CSF is drained out before the aorta is crossclamped. Papaverine is infused through the drain and allowed to diffuse. During aortic cross-clamping, CSF is allowed to
drain. The limited human studies available from this group have shown a reduction in rate of SCI. Evidence favoring its use
is limited and most TAAA surgeons do not currently employ this technique [28].
Similarly, epidural cooling has been used by a few groups to protect the spinal cord. Hypothermia is thought to reduce
spinal cord metabolic activity and reduce the ischemic insult during the period of cross-clamping. Local hypothermia
is induced by infusing iced normal saline into the CSF drain well prior to aortic cross-clamping. A separate catheter is
required to monitor CSF pressure because the infusion can cause elevated intrathecal pressures, which can decrease spinal
cord blood flow. More recently, specially designed infusion/drainage cooling catheters have been tested. Single-center studies have shown promise but the technique of epidural cooling has not been widely adopted [29,30].
Methods for Monitoring the Spinal Cord
Techniques for monitoring intraoperative spinal cord function may be helpful in preventing SCI by allowing for adjustments to be made if ischemia is suspected. During the procedure there is no clinical way to assess spinal cord function
without special monitoring. If the team is made aware of compromised spinal cord function they can attempt to increase
spinal perfusion by increasing MAPs, draining additional CSF, or adjusting anesthetics.
Monitoring of somatosensory evoked potential (SSEP) and motor evoked potentials (MEPs) is used by some groups as
an indirect method of assessing spinal cord function and perfusion intraoperatively [22,31,32]. SSEP monitoring is relatively safe to perform and is easy to interpret. However, the rate of false positive and false negative prediction for postoperative motor function in the lower extremities is high. SSEP monitoring relies on peripheral somatosensory nerves entering
the dorsal spinal cord and this may not be entirely reflective of changes in the anterior spinal cord, which is responsible for
motor function. MEP monitoring, on the other hand, is a sensitive measure of anterior spinal cord function and can be used
to evaluate the motor pathways. However, neuromuscular blockade can interfere with readings and the muscular twitching
that can occur during a reading can interfere with surgery [33]. MEPs are not suitable for postoperative monitoring but
SSEPs can be used both intra- and postoperatively.
Near-infrared spectroscopy (NIRS) has more recently emerged as a possible alternative to indirectly monitor spinal
cord perfusion. NIRS has been successfully used to monitor cerebral oximetry during aortic arch surgery with adjunctive
cerebral perfusion. The intercostal arteries, which are responsible for spinal cord blood flow, also supply blood to the paraspinous collateral network of vessels. Animal models have shown a high correlation of spinal NIRS readings with spinal
cord and paravertebral muscle oxygenation [34]. Preliminary human studies have shown that use of spinal NIRS is feasible
but confirmatory correlative studies are necessary [35].
RENAL–VISCERAL PROTECTION
Despite advances in surgical techniques and intensive care, postoperative renal dysfunction remains a major contributor to
the morbidity and mortality associated with TAAA repair. The incidence of acute renal dysfunction is up to 40% with acute
renal failure rates of 4%–11% [36]. Without adjunctive protective measures, the kidneys experience warm ischemic time
during the period of cross-clamping. Warm or cold solutions of either blood or crystalloid mixtures can be infused during
the cross-clamp period using balloon-tipped catheters. Blood solutions can be administered by passive shunts but are most
often run off of the left heart bypass circuit. Crystalloid solutions are less cumbersome and can be run through a separate
pump [37].
Although one might assume that normothermic oxygenated blood would be the most physiologic solution, comparisons
of warm blood to cold crystalloid renal protection showed that cold crystalloid renal protection resulted in lower rates
of acute renal dysfunction but no difference in need for dialysis [36]. The benefits of hypothermia, including decreased
metabolism and reduced ischemic damage, appeared to outweigh the benefits of oxygen-rich, nutritive blood flow. Further
studies comparing cold blood to cold crystalloid solution found that cold crystalloid offered comparable renal protection
compared to cold blood and the use of oxygenated blood offered no enhanced protection [38]. Crystalloid renal protection
can be given as intermittent doses with an initial dose of 200–300 mL into each kidney, followed by 100–150 mL doses
every 10–15 min.
Bowel and mesenteric ischemia is a much less common complication, occurring in about 1% of TAAA repairs. For
extensive TAAA repairs in which visceral perfusion may be beneficial, left heart bypass is used during the proximal
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anastomosis to perfuse the distal aorta. Then when the distal aorta is later opened, continuous isothermic blood is infused
at 300–500 mL/min into the superior mesenteric and celiac arteries via the left heart bypass circuit [39].
POSTOPERATIVE MANAGEMENT
Aside from the usual cardiopulmonary management of a patient who has undergone an extensive thoracic and/or abdominal
operation, care of the postoperative TAAA patient is largely focused on preserving spinal cord blood flow and function.
Patients have hourly neurologic exams to document adequate spinal cord function. Hemodynamics are optimized to allow
for augmented spinal perfusion. MAP is kept artificially elevated at 85–90 mmHg. CSF pressure is kept below 12 mmHg
with the aid of a lumbar spinal drain. The combination of systemic hypertension and low intraspinal pressure helps maximize spinal perfusion pressure.
Cardiac function is supported with inotropes as necessary. Aggressive fluid resuscitation is necessary in order to maintain an adequate preload. These patients often have a strong inflammatory response with extensive third spacing of fluid. In
the immediate postoperative period, crystalloid is infused at a rate of 200–300 mL/h with additional boluses as necessary.
Red blood cells are transfused to maintain an adequate hematocrit. This helps augment blood pressures as well as increases
oxygen carrying capacity of the circulating blood volume, including that to the spinal cord. After the first 24–48 h, capillary leaks begin to seal and third spacing decreases. Fluid is mobilized back into the intravascular space and diuretics are
usually necessary.
Lumbar spinal drains are left in place for 72 h. At that point, the drain is clamped and neurologic function is monitored
for several hours before the drain is removed. A small subset of patients will have delayed neurologic deficits. If this occurs,
a new lumbar spinal drain should be placed immediately and MAP should be brought back up to as high as 90–100 mmHg
immediately. Many delayed SCIs can be reversed if acted upon expediently.
SPECIAL SITUATIONS
Ruptured TAAAs present a challenging situation for surgeons and operative mortality was as high as 50% in the 1990s in a
nationwide sample [40]. Often these patients have multiple comorbidities and present with hemodynamic instability. With
improvements in surgical technique and perioperative care, mortality has decreased to 24% in the more current era [40].
This is in part due to the advent of thoracic stent-grafts, which, when anatomy is appropriate, have significantly reduced
mortality associated with ruptured aneurysms. However, many patients do not have suitable anatomy and this necessitates
open surgery. Fortunately, operative mortality has improved significantly with open procedures as well. In experienced
referral centers, ruptured TAAAs can be repaired with an operative mortality as low as 14% in ruptured aneurysms compared to 4% in intact aneurysm patients [7].
Mycotic or infected TAAAs present another unique challenge. There is a high incidence of fatal rupture and mortality
in excess of 45% with medical therapy alone [41]. Surgery is often the best option although operating is not without risk.
Operative mortality ranges from 3% to 33% [41,42]. In addition to repairing the aneurysm, all of the infected tissue must
be debrided and a variety of methods must be used to prevent graft reinfection. Empiric antibiotics should be started upon
diagnosis and adjusted based on cultures. In the thoracoabdominal aorta, anatomic limitations require that the graft be
placed in the in situ position so often soft tissue coverage of the graft is necessary to protect the graft from the surrounding tissues that may harbor residual bacteria. This can be achieved with a serratus anterior muscle flap or omental flap.
Postoperatively, patients are treated with an extended period of intravenous antibiotics. Long-term suppression with oral
antibiotics may help prevent reinfection [41].
A number of patients who have surgery on the thoracic aorta will return for another dilated segment of the aorta in the
future. In the thoracoabdominal aorta, the most common scenario is a DTA or extent I TAAA repair followed by dilatation
of the distal aorta requiring either an extent III or extent IV TAAA repair. Reoperations in this space are made difficult by
the extensive adhesions in the reoperative field as well as the additional hemodynamic stress of another aortic procedure.
Although risk and mortality may be mildly higher than with first time operations, reoperations can be performed with reliable results [43]. Access to the aorta can usually be obtained through either the same incision or a thoracotomy incision two
rib spaces above or below the previous thoracotomy to prevent soft tissue ischemia.
Thoracic endovascular aneurysm repair (TEVAR) has become an increasingly common method for repairing descending thoracic aneurysms. However, 10%–15% of patients with degenerative aneurysms and 16%–24% of patients with
chronic dissections who are treated with stent-grafts will need additional aortic reinterventions, many of which are open
aortic procedures [44,45]. TEVAR can fail due to endoleaks (most commonly type I), graft infection, device failure, migration, or continued aortic growth. These patients may need complete explantation of the stent-graft and interposition graft
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replacement. The surgical approach to these aneurysms is similar to routine TAAA repairs. Proximal vascular control may
require cross-clamping of the segment of aorta that is stented. The majority of stent-grafts are manufactured using selfexpanding nitinol and we have not found any significant damage using padded cross-clamps. In patients who have dilatation of the aorta distal to the stent-graft, some of these grafts can be salvaged partially or fully by incorporating the distal
end of the stent-graft into the proximal anastomosis of the distal aortic repair, creating a “sandwich” incorporating the
layers of the native aorta, stent-graft, and surgical prosthetic graft [44].
In the elderly population, namely octogenarians, careful consideration must be given to whether these patients are
appropriate candidates for open TAAA repair. This population generally has more comorbidities and often have heavily
calcified branch vessels that may require endarterectomy or stenting. In even the most experienced hands, operative mortality is as high as 26% compared to 6.9% in a younger population. Less extensive repairs carry more reasonable results but
more extensive operations carry the highest mortality with extent II repairs having a mortality of up to 62% [46]. Although
life-saving surgery should not be absolutely withheld from octogenarians, especially in those presenting with rupture, those
with extensive asymptomatic aneurysms should be evaluated carefully. Risk of surgery may exceed the risk of medical
management.
CONCLUSION
Surgery for DTA and TAAA continues to be an evolving field. Despite the many advances in intraoperative technique
and perioperative critical care, it remains a difficult procedure associated with not insignificant morbidity and mortality,
especially with more extensive aneurysms. Experienced centers can build a team that produces reliably good results.
A multitude of surgical techniques and spinal cord protective measures are available. Some combination of these techniques must be used if optimal results are to be achieved.
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Chapter 31
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Subtotal and Total Aortic Replacement
Marian Gaspar
Institute of Cardiovascular Medicine, Timisoara, Romania
Chapter Outline
Introduction 357
Revolutionary Discovery of Heart–Lung Machine 357
Evolution of Graft Tube 358
Subtotal and Total Aortic Arch Replacement 358
Indication of Partial or Total Aortic Arch Replacement 358
Exposure and Cannulation for Cardiopulmonary Bypass 360
Cerebral Protection During Aortic Arch Replacement 361
Retrograde Cerebral Perfusion 362
Anterograde Cerebral Perfusion 362
Distal Visceral Perfusion 363
Total Aortic Arch Replacement Technique 363
Open Technique for Aortic Arch Replacement 363
Partial Arch Repair Technique 364
Elephant Trunk Technique 365
Hybrid Procedure of Total Aortic Arch Replacement 367
Complications of and Results of Aortic Arch Surgery 368
Results of Aortic Arch Surgery 368
References 369
Further Reading 371
INTRODUCTION
The aortic arch is the second segment of aorta with its origin in the innominate artery, left common carotid artery, and left
subclavian artery. Surgery of the aortic arch remains among the most challenging techniques, because from this segment,
a real crossroad, arises great vessels that give blood to the brain, upper part of the body, and downstream visceral organs.
For the aneurysm, even before of open-heart surgery era, the surgical approach was to prevent rupture by promoting
thrombosis, distal or proximal ligature (Anell, Brasdor, Pasquin), wrapping with cellophane (Harrison, Chandy), getting
inside of aneurysm suturing (Mattas), and total aneurysm resection with or without reconstruction of the vessel. But in spite
of this difficulty, very early, and even before heart–lung machine support, in the mid-1950s several attempts were made by
visionary surgeons to fully replace the aortic arch.
In 1955, Denton Cooley and Michael DeBakey utilized innovative techniques, such as bypass shunts and hypothermia,
try to repair the aortic arch, but the patient developed cerebral stroke and died [1]. The major principle of surgery, consisting of cutting the diseased segment of an organ to restore the normal function of the organ, was a target for generations of
surgeons. Three major landmark targets were already defined at the first attempt of total resection of aortic arch by Cooley
and his colleagues: to find a resistant, easy-to-insert tube to replace a natural aorta; methods to protect and give blood to
the brain and distal visceral organs, during these maneuvers (a temporary shunt, surface cooling, cerebral protection); and
to avoid distal thrombosis of the vessels by heparin.
REVOLUTIONARY DISCOVERY OF HEART–LUNG MACHINE
In the early 1950s cardiac and great vessels surgery was reduced to a few closed-heart procedures. The need for visualization of the inside structure of the heart brought together the ideas of visionary engineers and doctors—Charles Lindbergh,
Alexis Carrel, John Gibbon, C. Walton Lillehei, R. DeWall, Warden Cohen, Vincent Gott, and others—to develop a machine
that could interrupt the circulation by taking over the functions of the heart and lungs, allowing surgeons to repair and then
restore normal heart structures, lung, and great vessels function. They had to answer to a lot of questions: how to arrest the
heart, how to drain the blood from the body, how to pump it back, how to clear air from the inside of the heart, and how
to anticoagulate successfully without clotting the machinery (fortunately, heparin had been discovered by Jay McLean in
1916).
New Approaches to Aortic Diseases from Valve to Abdominal Bifurcation. http://dx.doi.org/10.1016/B978-0-12-809979-7.00031-6
Copyright © 2018 Elsevier Inc. All rights reserved.
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The first use of a heart–lung machine in 1953 by Gibbon to repair an atrial septal defect was a result of more than
25 years of studies, experimental works, and observations. In spite of his personal disappointment after a series of unsuccessful operations, this opened the way for today’s advances. At that time, the era of modern aortic aneurysm surgery was
open, and Cooley succeeded in convincing some of his cardiologists that “the era of open-heart surgery had arrived” and in
1956 began to perform open-heart surgery, ascending aortic aneurysm and aortic arch, using the DeWall–Lillehei bubble
oxygenator, deep hypothermia, and heparin, with considerable success [2,3].
EVOLUTION OF GRAFT TUBE
At the beginning of aneurysm surgery, the vascular tube supply used was the aortic homograft. In 1952, DeBakey and
Cooley were the first to use a homograft to repair a large aneurysm of the thoracoabdominal aorta, to replace the ascending
aorta (1956) and the aortic arch (1957) [4,5]. But after this, the natural tube was abandoned because calcification appears
very soon after such surgery.
The first used artificial graft tube by Cooley, in his first aortic arch aneurysm replacement, was polyvinyl alcohol sponge
(Ivalon) with formaldehyde, in 1955. The properties that accounted for its early popularity included malleability (enabling a
wide variety of shapes and sizes of graft to be prepared) and ease of handling at operation. Early reports were encouraging
and it was considered favorable in a comprehensive review by Rob (1955).
Subsequent experience, however, showed difficulties in manufacture and, more seriously, a tendency in vivo to loss of
tensile strength, failure of fibrous tissue in growth, calcification, and in some cases rupture (Brown and Essig, 1959). Ivalon
has been abandoned as a vascular graft [6].
A better velour knitted graft was introduced by DeBakey and Cooley. Using the deep hypothermia and fully heparin
circuits of the patients under cardiopulmonary bypass, the serious problem of bleeding was difficult to control and in 1981
Cooley developed a method to prepare woven Dacron grafts soaked in the patient’s own plasma and then autoclaved to
seal the interstices of the graft with coagulated protein [7]. Quickly, the companies producing this vascular graft developed
methods of sealing, giving the best zero porosity prosthesis with no need for preclotting and no oozing, easy handling,
and suture made. This innovative concept had a dramatic effect in reducing postoperative bleeding, mortality, and surgeon
stress [8].
SUBTOTAL AND TOTAL AORTIC ARCH REPLACEMENT
Indication of Partial or Total Aortic Arch Replacement
There are two major, different pathological situations requiring surgery on the aortic arch: aortic dissection and aortic arch
aneurysm.
Aortic aneurysm can occur anywhere along the aorta segments. However, isolated aortic arch aneurysm, type A, is less
frequent. Usually it is a continuation of ascending or descending aorta aneurysm, types B, C, and D, making this approach
even more difficult. Etiology of this aneurysm is the same like others in localization, medial degenerative disease, after
chronic aortic dissection, associated with genetic disorders including Marfan syndrome, Ehlers–Danlos syndrome, Loeys–
Dietz syndrome, infection (syphilis), and very rare after trauma. They are saccular or fusiform aortic arch aneurysm, partial
arch, or total. At the beginnings of aortic arch surgery and before a correct treatment of syphilis infection, a lot of specific
saccular aortic arch and brachiocephalic vessel aneurysms were diagnosed and operated on. The fate of this localization
was compared with cancer because of the rupture and sudden death. The diagnosis “as soon as possible, but despite of the
most thorough studies the precise diagnosis will often remain in doubt unless exploratory thoracotomy is done” (D. Cooley,
1955), was not as clear as it is now, in the era of CT-256 multislice aortography. Great progress has been made in the treatment of aortic aneurysms over the past 5 decades, but the work and visions of Cooley have contributed remarkably to our
modern approach of aortic aneurysms [9]. He developed aortic arch classification (Fig. 31.1), which is helpful because by
location and extension, there are different techniques for repair [10].
The surgical indication in case of isolated aortic arch aneurysms in low-risk, asymptomatic patients is to replace the arch
when the aortic diameter exceeds 6 cm or is growing more than 0.5 cm per year.
Saccular aneurysms tend to grow more rapidly than fusiform aneurysms, and often rupture and compression express
the symptoms; earlier intervention is recommended. With ascending aorta aneurysm over 6 cm and proximal arch over
5 cm, it is appropriate to perform a partial arch replacement along with the ascending aortic replacement. Also, it is recommended to replace the aortic arch in cases of chronic dissection and aneurysms over 6 cm, which extend in descending aorta,
symptomatic (compression over nerves, trachea), and which have a high risk of rupture. Descending aorta aneurysm that
Subtotal and Total Aortic Replacement Chapter | 31 359
(A)
(C)
(B)
(D)
(E)
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FIGURE 31.1 Aortic aneurysm classification D. Cooley and CT-64 with ascending aortic aneurysm, huge aortic arch, and descending aortic aneurysm,
unusual origin of the right subclavian artery from the top of saccular dilatation (Timisoara).
involves also distal aortic arch can be operated on with a partial distal aortic arch, reimplantation of left subclavian artery,
and descending aorta grafting with or without cardiopulmonary support by a left anterolateral thoracotomy.
Arch vessel debranching and stent graft might be considered as an alternative to conventional surgery in certain clinical situations of aortic arch aneurysm and dissection, especially when the risk is very high when exposing patients to such
complex procedures.
The second major pathology, acute and chronic aortic dissection of aortic arch, is even more demanding for the surgeon.
Acute aortic dissection is a major emergency surgery that requires quick, precise diagnosis and proper management. First,
in 1965 DeBakey classified dissections into three types: Type 1: intimal entry flap is located in the ascending aorta and
extends distal to the ascending aorta for a short distance. Type 2: is limited to the ascending aorta and terminates proximal
to the origin of the innominate artery. Type 3: flap enters in the descending thoracic aorta, usually at or just distal to the left
subclavian artery. Then came the Stanford classification, with two types: type A, with involvement of the ascending aorta;
and type B, which indicates a dissection limited to the descending aorta (Fig. 31.2).
This Stanford classification is more practical and in closer relationship to management. Type A dissections require
emergent surgical management because of their tendency to complications: acute myocardium infarction from coronary
artery occlusion, rupture into the pericardium with cardiogenic shock from cardiac tamponade, and acute aortic regurgitation from leaflet rupture [11]. Type B dissections are managed by medical treatment as long as they are not complicated by
spinal, visceral, or severe limb ischemia.
Aortic arch dissection acute or chronic comprises a dissection flap or intramural hematoma with extension into the
transverse arch between the innominate artery and the left subclavian artery. However, aortic arch dissection was not clear
defined. When aortic arch and ascending aorta is involved we have type A dissection, while aortic arch dissection without
ascending aortic involvement is classified as type B dissection (with aortic arch involvement). Dissection is considered
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FIGURE 31.2 DeBakey (types 1, 2, 3) and Stanford (types A, B) classification of acute aortic dissection.
acute under 14 days from the onset of the symptoms (chest pain), subacute between 15 and 90 days, and chronic over
90 days from inception.
Acute type A aortic dissection is an emergency because it has a mortality of 50% within the first 48 h if not operated.
Despite improvements in surgical and anesthetic techniques, perioperative mortality is still very high, 10%–25% and neurological complications as well, 18%, remain high, and organ failure sometimes occurs before surgery [11].
Acute aortic arch dissection is managed like type B, while the supra-aortic vessels with cerebral or superior limb ischemia symptoms are not involved. It is still not clear how to deal with patients having neurological deficit or comas.
When the dissection progresses into the supra-aortic vessel, a better technique to use is end-to-end grafting of all supraaortic vessels, using four-branch grafts, in favor of island technique. A major problem is the quality of the arterial wall,
which is very fragile in acute dissection compared with chronic or aneurismal wall. The suture technique must be perfect.
Exposure and Cannulation for Cardiopulmonary Bypass
Incision: The surgical approach depends on the extent of aortic arch aneurysm and other cardiac or aortic approaches at
the same time (ascending aortic aneurysm, aortic valve surgery, coronary artery disease, descending aortic aneurysm, or
dissection). The historical approach in 1951, a right anterior thoracotomy, performed through the second intercostal space,
revealed a large aneurysm of innominate artery at the origin, eroding the sternum and partially occluding the right innominate vein. In order to obtain better exposure, the incision was extended proximal to the suprasternal notch and then directed
laterally to the posterior border of the sternomastoid muscle (Cooley).
Repair or replacement of the ascending aorta and aortic arch is performed through a median full or partial sternotomy
with cardiopulmonary bypass [12]. Aneurysms that involve the distal arch and descending/thoracoabdominal aorta are performed through a left anterolateral thoracotomy [13]. Cardiopulmonary bypass can be established in such cases, between
femoral artery return and right atrial drainage and the right femoral vein. Kouchoukos used a clam-shell incision for a onestage operation for extended thoracic aneurysms, giving large exposure for ascending aorta, aortic arch, and descending
aorta. But now a minimally invasive approach, ministernotomy, has been described for aortic arch dissection and aneurysm.
Regarding the cardiopulmonary bypass, arterial cannulation site for inflow, right axillary artery perfusion is the first
choice not only in emergency operation, to repair an acute aortic dissection involving ascending aorta and aortic arch,
but also in chronic aortic arch situation and aneurysm [14–17]. This artery is rarely involved in the dissection, is seldom
affected by atherosclerotic plaques, and is of adequate size to carry full-flow CPB in patients who have a large body-surface
area. Axillary cannulation can be performed directly or using the interposition of an 8 mm Dacron graft. Some surgeons
prefer to use, after median sternotomy, the innominate artery for cardiopulmonary bypass [18]. But the femoral artery is
still frequently used in the acute condition because of quick preparation, when you need emergency bypass (Fig. 31.3).
The ascending aorta remains a choice in the case of chronic presentation and after cooling, circulatory arrest, distal aortic
(A)
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(B)
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FIGURE 31.3 Right axillary artery and right femoral artery—two favorites sites for aortic arch surgery cannulation.
vessel anastomosis, when it is possible to restart cardiopulmonary bypass for rewarming through the fourth branch of the
commercial prosthesis.
A European study including more than 400 contacted centers completed the survey correctly. The most preferred site
for arterial cannulation is the subclavian–axillary, both in acute and chronic presentation. Axillary cannulation can be performed directly or using the interposition of an 8-mm Dacron graft [19].
Cerebral Protection During Aortic Arch Replacement
The major concern of the aortic arch surgery, which requires manipulation and exclusion of the cerebral blood flow, for
“bloodless” performing of the repair, optimal methods of cerebral protection are required to prevent ischemic brain injuries.
There are two different mechanisms of brain injury: embolic (air, atheroma plaques) and ischemic (reduce the blood flow).
The result can be a permanent neurological dysfunction (stroke, coma, death) or transitory neurological dysfunction (confusion, agitation, delirium, obnubilation) with complete resolution during hospitalization. These complications are not only
problems for the central nervous system and brain spinal cord but also for the distal organs, such as kidneys and bowels.
Very early physiological observations brought the solution for cerebral protection using deep hypothermia and total
circulatory arrest at an average of 15–18°C, where cerebral metabolic demand is reduced and 45–60 min can be relatively
well tolerated [20].
The Mount Sinai Center team in New York City, with Randall Griepp and M. Arisan Ergin, started in 1975 and did a
complete resection of the aortic arch aneurysm and replacement with a graft, using deep hypothermia and total circulatory
arrest. From the first four patients operated on they had three survivors [21–23]. In Europe deep hypothermia and total
circulatory arrest was used in practice even earlier by Borst, in 1964, but for closing a traumatic fistula between aorta and
pulmonary artery.
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