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Surgery_Schwartz. graft.85 For fusiform aneurysms, when the distal portion of the arch is a reasonable size, a single, beveled replacement of the lower curvature (hemiarch) is performed. More extensive arch aneurysms require total replacement involving a distal anastomosis to the proximal descending tho-racic aorta and separate reattachment of the brachiocephalic branches. The brachiocephalic vessels can be reattached to one or more openings made in the graft, or if these vessels are aneurysmal, they can be replaced with separate, smaller grafts. Alternatively, a Y-graft approach86,87 can be used to debranch the brachiocephalic vessels and move them forward, thereby permitting the distal anastomosis to be brought forward, which aids in hemostasis. When the aneurysm involves the entire arch and extends into the descending thoracic aorta, it is approached by using Borst’s elephant trunk technique of staged total arch replacement.88 The distal anastomosis is performed such that a portion of the graft is


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Surgery_Schwartz. the descending thoracic aorta, it is approached by using Borst’s elephant trunk technique of staged total arch replacement.88 The distal anastomosis is performed such that a portion of the graft is left suspended within the proximal descending thoracic aorta (Fig. 22-7). A collared graft can be used to accommodate any discrepancy in aortic diameter.86 During a subsequent operation, the suspended “trunk” is used to facilitate repair of the remaining descending thoracic or tho-racoabdominal aortic aneurysm by an endovascular technique or by open repair through a thoracotomy incision, depending on the extent of disease and other factors. The elephant trunk technique permits access to the distal portion of the graft during the second operation without the need for dissection around the distal transverse aortic arch; this reduces the risk of injuring the left recurrent laryngeal nerve, esophagus, and pulmonary artery if an open approach is used at the second stage. As described in the


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Surgery_Schwartz. transverse aortic arch; this reduces the risk of injuring the left recurrent laryngeal nerve, esophagus, and pulmonary artery if an open approach is used at the second stage. As described in the section on hybrid repair of arch aneurysms (see later), the elephant trunk can be completed by using a hybrid endovascular approach (Fig. 22-8) in certain settings. A newer technique that is currently under investigation involves using a graft compris-ing a conventional polyester proximal portion and a stent graft distal elephant trunk portion. This “frozen elephant trunk” tech-nique can enable treatment of the entire aortic pathology during a single procedure or can facilitate a subsequent endovascular procedure (Fig. 22-9).89-91Cardiopulmonary Bypass Perfusion Strategies Like the opera-tions themselves, perfusion strategies used during proximal aor-tic surgery depend on the extent of the repair. Aneurysms that are isolated to the ascending segment can be replaced by using standard


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Surgery_Schwartz. themselves, perfusion strategies used during proximal aor-tic surgery depend on the extent of the repair. Aneurysms that are isolated to the ascending segment can be replaced by using standard cardiopulmonary bypass and distal ascending aortic clamping. This provides constant perfusion of the brain and other vital organs during the repair. Aneurysms involving the transverse aortic arch, however, cannot be clamped during the repair, which necessitates the temporary withdrawal of cardio-pulmonary bypass support; this is called circulatory arrest. To protect the brain and other vital organs during the circulatory arrest period, hypothermia must be initiated before pump flow is stopped. However, the deep levels of hypothermia (below 20°C) that have been traditionally used in open arch repair are not without risk, and pure hypothermic circulatory arrest contin-ues to have substantial limitations. Importantly, although brief periods of total circulatory arrest generally are well tolerated


Surgery_Schwartz

Surgery_Schwartz. are not without risk, and pure hypothermic circulatory arrest contin-ues to have substantial limitations. Importantly, although brief periods of total circulatory arrest generally are well tolerated at cold temperatures, as the duration of circulatory arrest increases, the well-recognized risks of brain injury and death increase dra-matically. Additionally, deep levels of hypothermia are associ-ated with coagulopathy.Because of the inherent complexity of aortic arch repairs and their general tendency to require longer periods Brunicardi_Ch22_p0853-p0896.indd 86501/03/19 5:41 PM 866SPECIFIC CONSIDERATIONSPART IIADFGECBFigure 22-7. Illustration of a contemporary Y-graft approach to total arch replacement for aortic arch aneurysm. A. The proximal portions of the brachiocephalic arteries are exposed. B. The first two branches of the graft are sewn end-to-end to the transected left subclavian and left common carotid arteries. The proximal ends of the transected brachiocephalic arteries


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Surgery_Schwartz. exposed. B. The first two branches of the graft are sewn end-to-end to the transected left subclavian and left common carotid arteries. The proximal ends of the transected brachiocephalic arteries are ligated. C. A balloon-tipped perfusion cannula is placed inside the double Y-graft and used to deliver antegrade cerebral perfusion. After systemic circulatory arrest is initiated, the innominate artery is clamped, transected, and sewn to the distal end of the main graft. D. The proximal aspect of the Y-graft is clamped. This directs flow from the axillary artery to all three brachiocephalic arteries. The arch is then replaced with a collared elephant trunk graft. E. The distal anastomosis between the elephant trunk graft and the aorta is created between the innominate and left common carotid arteries. The collared graft accommodates any discrepancy in aortic diameter. F. The aortic graft is clamped, and a second limb from the arterial inflow tubing of the cardiopulmonary bypass circuit


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Surgery_Schwartz. arteries. The collared graft accommodates any discrepancy in aortic diameter. F. The aortic graft is clamped, and a second limb from the arterial inflow tubing of the cardiopulmonary bypass circuit is used to deliver systemic perfusion through a side-branch of the arch graft while the proximal por-tion of the ascending aorta is replaced. Once the proximal aortic anastomosis is completed, the main trunk of the double Y-graft is cut to an appropriate length, and the beveled end is then sewn to an oval opening created in the right anterolateral aspect of the ascending aortic graft, which completes the repair (G). (Modified with permission from LeMaire SA, Price MD, Parenti JL, et al. Early outcomes after aortic arch replacement by using the Y-graft technique, Ann Thorac Surg. 2011 Mar;91(3):700-707.)of hypothermic circulatory arrest, two cerebral perfusion strategies—retrograde cerebral perfusion (RCP) and antegrade cerebral perfusion (ACP)—were developed to supplement this process by


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Surgery_Schwartz. hypothermic circulatory arrest, two cerebral perfusion strategies—retrograde cerebral perfusion (RCP) and antegrade cerebral perfusion (ACP)—were developed to supplement this process by delivering cold, oxygenated blood to the brain and further reduce the risks associated with repair. Retrograde cerebral perfusion involves directing blood from the cardio-pulmonary bypass circuit into the brain through the superior vena cava.92 However, RCP is thought to be less beneficial than ACP,93 and although it may be helpful in the retrograde flush-ing of air and debris from the arch, many centers have stopped using RCP.In contrast, ACP delivers blood directly into the brachio-cephalic arteries to maintain cerebral flow. Although its use was cumbersome in the past, contemporary ACP techniques (Fig. 22-10) have been simplified and commonly involve can-nulating either the right axillary artery or the innominate artery and subsequent connection to the cardiopulmonary bypass circuit.94-96 Often, a


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Surgery_Schwartz. 22-10) have been simplified and commonly involve can-nulating either the right axillary artery or the innominate artery and subsequent connection to the cardiopulmonary bypass circuit.94-96 Often, a small section of graft is used as a conduit to ease cannulation, but there remains a small procedure-related risk of brachial plexus or vascular injury. Upon initiation, cold blood is delivered into the brain via the right common carotid artery and, if bilateral ACP is desired, the left common carotid artery. Note that, with the unilateral ACP technique, blood flow to the left side of the brain requires collateral circulation, ideally through an intact circle of Willis.Methods to help determine the adequacy of unilateral ACP to deliver cerebral cross-circulation include preoperative imag-ing and intraoperative monitoring. A commonly used method Brunicardi_Ch22_p0853-p0896.indd 86601/03/19 5:41 PM 867THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22ABCFigure 22-8. Illustration of


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Surgery_Schwartz. and intraoperative monitoring. A commonly used method Brunicardi_Ch22_p0853-p0896.indd 86601/03/19 5:41 PM 867THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22ABCFigure 22-8. Illustration of Borst’s elephant trunk technique using a contemporary Y-graft approach. A. Stage 1: The proximal repair includes replacing the ascending aorta and entire arch, with Y-graft reattachment of the brachiocephalic vessels. The distal anastomosis is facilitated by using a collared elephant trunk graft to accommodate the larger diameter of the distal aorta. A section of the graft is left sus-pended within the proximal descending thoracic aorta. B. Stage 2: The distal repair uses the floating “trunk” for the proximal anastomosis. C. An alternate “hybrid” approach may be used in patients with less extensive distal aortic disease. Endovascular stent grafts are placed within the elephant trunk to complete the repair. (Used with permission of Baylor College of Medicine.)ABFigure 22-9. Illustration of a


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Surgery_Schwartz. distal aortic disease. Endovascular stent grafts are placed within the elephant trunk to complete the repair. (Used with permission of Baylor College of Medicine.)ABFigure 22-9. Illustration of a frozen elephant trunk repair, which is a hybrid approach to repair that combines open aortic replacement with endovascular aortic repair. A. Extensive aortic disease affects the proximal and distal aorta. B. Aortic repair is extended into the proximal por-tion of the descending thoracic aorta after the transverse aortic arch is fully replaced. (Used with permission of Baylor College of Medicine.)Brunicardi_Ch22_p0853-p0896.indd 86701/03/19 5:41 PM 868SPECIFIC CONSIDERATIONSPART IIFigure 22-10. Illustration of a contemporary technique for deliv-ering antegrade cerebral perfusion during aortic arch repair. A. A graft sewn to the right axillary artery or to the innominate artery (inset) is used to return oxygenated blood from the cardiopulmo-nary bypass circuit. B. After adequate hypothermia


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Surgery_Schwartz. repair. A. A graft sewn to the right axillary artery or to the innominate artery (inset) is used to return oxygenated blood from the cardiopulmo-nary bypass circuit. B. After adequate hypothermia is established, the innominate artery is occluded with a tourniquet (inset) so that flow is diverted to the right common carotid artery, which maintains cerebral circulation. (Used with permission from Baylor College of Medicine.)of intraoperative monitoring is brain near-infrared spectroscopy (NIRS), which measures cerebral oxygenation. If NIRS moni-toring indicates inadequate perfusion, an additional perfusion catheter can be inserted into the left common carotid artery to provide blood flow to the left side of the brain.Because ACP provides excellent brain protection, many surgeons now use more moderate levels of hypothermia (often between 22°C and 24°C) to decrease the risks associated with deep hypothermia.97 However, some authors have raised the ABconcern that reducing the degree of


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Surgery_Schwartz. more moderate levels of hypothermia (often between 22°C and 24°C) to decrease the risks associated with deep hypothermia.97 However, some authors have raised the ABconcern that reducing the degree of hypothermia increases the risk of ischemic complications involving the spinal cord, kid-neys, and other organs that are ischemic (without the benefit of deep hypothermia) during the systemic circulatory arrest period.98 Consequently, some groups supplement ACP with additional perfusion strategies that provide flow to the descend-ing aorta during arch repair.99,100Endovascular Repair Experience with purely endovascular treatment of proximal aortic disease remains limited and only investigational.101 The unique anatomy of the aortic arch and the need for uninterrupted cerebral perfusion pose difficult chal-lenges. There are reports of the use of “homemade” grafts to exclude arch aneurysms; however, these grafts are experimen-tal at this time. For example, in 1999, Inoue and colleagues102


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Surgery_Schwartz. difficult chal-lenges. There are reports of the use of “homemade” grafts to exclude arch aneurysms; however, these grafts are experimen-tal at this time. For example, in 1999, Inoue and colleagues102 reported placing a triple-branched stent graft in a patient with an aneurysm of the aortic arch. The three brachiocephalic branches were positioned by placing percutaneous wires in the right brachial, left carotid, and left brachial arteries. The patient underwent two subsequent procedures: surgical repair of a right brachial pseudoaneurysm and placement of a distal stent graft extension to control a major perigraft leak. Since then, efforts to employ endovascular techniques in the treatment of the proxi-mal aorta have been essentially limited to the use of approved devices for off-label indications, such as the exclusion of pseu-doaneurysms in the ascending aorta.Hybrid Repair In June 1991, the Ukrainian surgeon Nikolay Volodos and his colleagues performed the first hybrid aortic arch


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Surgery_Schwartz. such as the exclusion of pseu-doaneurysms in the ascending aorta.Hybrid Repair In June 1991, the Ukrainian surgeon Nikolay Volodos and his colleagues performed the first hybrid aortic arch repair103,104; 22 years later, Volodos reported that the patient was still alive.105 Unlike purely endovascular approaches, hybrid repairs of the aortic arch have entered the mainstream clinical arena, although they remain controversial. Hybrid arch repairs involve some form of “debranching” of the brachiocephalic vessels (which are not unlike Y-graft approaches), followed by endovascular exclusion of some or all of the aortic arch (Fig. 22-11). Although this technique has many variants, they often involve sewing a branched graft to the proximal ascend-ing aorta with the use of a partial aortic clamp. The branches of the graft are then sewn to the arch vessels. Once the arch is “debranched,” the arch aneurysm can be excluded with an endograft. Commonly, a zone 0 approach (Fig. 22-12) is under-taken


Surgery_Schwartz

Surgery_Schwartz. branches of the graft are then sewn to the arch vessels. Once the arch is “debranched,” the arch aneurysm can be excluded with an endograft. Commonly, a zone 0 approach (Fig. 22-12) is under-taken in which the proximal end of the endograft is secured within the ascending aorta. Other hybrid approaches aim to extend repair into the distal arch and descending thoracic aorta (see the following section). The arguments for using a hybrid approach to treat aortic arch aneurysm include the potential to avoid using cardiopulmonary bypass, circulatory arrest, and car-diac ischemia.59,60It is not yet clear whether hybrid repairs are as durable as traditional ones because little midor long-term data have been published, and there are very few comparative studies.65 Procedure-related risks include the risk of embolization and stroke due to wire and device manipulation within the aortic arch (this risk appears to be greatest in zone 0 repairs106), retrograde acute aortic dissection,107 type I


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Surgery_Schwartz. the risk of embolization and stroke due to wire and device manipulation within the aortic arch (this risk appears to be greatest in zone 0 repairs106), retrograde acute aortic dissection,107 type I endoleak,108 and paraplegia.27 Because iatrogenic retrograde dissection of the ascending aorta is a particularly lethal complication, special considerations, including careful blood pressure management and wire manipulation, are recommended to avoid this problem in patients who are undergoing hybrid arch zone 0 stent deployment.109 Notably, patients with an ascending aortic diameter greater than 4.2 cm may be more susceptible to retrograde dissection. In an effort to Brunicardi_Ch22_p0853-p0896.indd 86801/03/19 5:41 PM 869THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22Figure 22-11. Illustration of a “Zone 0” hybrid arch repair. A. A distal arch aneurysm is shown that extends into the proximal aspect of the descending thoracic aorta. B. The brachiocephalic vessels are debranched onto


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Surgery_Schwartz. of a “Zone 0” hybrid arch repair. A. A distal arch aneurysm is shown that extends into the proximal aspect of the descending thoracic aorta. B. The brachiocephalic vessels are debranched onto a Y-graft, and a separate graft is used as a conduit for ante-grade endovascular deployment of the stent graft. C. In the completed repair, the proximal landing zone of the endograft is within zone 0. (Used with permission from Baylor College of Medicine.)reduce the risk of iatrogenic dissection, some centers have begun to replace a small section of the ascending aorta with a standard polyester graft such that the endograft’s proximal landing zone comprises prosthetic material rather than native aortic tissue.107Distal Thoracic Aortic Aneurysms Open Repair In patients with descending thoracic or thoracoab-dominal aortic aneurysms, several aspects of treatment—includ-ing preoperative risk assessment, anesthetic management, choice of incision, and use of protective adjuncts—are dictated by the


Surgery_Schwartz

Surgery_Schwartz. thoracoab-dominal aortic aneurysms, several aspects of treatment—includ-ing preoperative risk assessment, anesthetic management, choice of incision, and use of protective adjuncts—are dictated by the overall extent of aortic involvement. By definition, descend-ing thoracic aortic aneurysms involve the portion of the aorta between the left subclavian artery and the diaphragm. Thora-coabdominal aneurysms can involve the entire thoracoabdominal aorta, from the origin of the left subclavian artery to the aortic bifurcation. Surgical repair of thoracoabdominal aortic aneu-rysms is categorized by the extent of aortic replacement accord-ing to the Crawford classification scheme (Fig. 22-13). Extent I thoracoabdominal aortic aneurysm repairs involve most of the descending thoracic aorta, usually beginning near the left sub-clavian artery, and extend down into the suprarenal abdominal aorta. Extent II repairs also begin near the left subclavian artery but extend distally into the infrarenal


Surgery_Schwartz

Surgery_Schwartz. beginning near the left sub-clavian artery, and extend down into the suprarenal abdominal aorta. Extent II repairs also begin near the left subclavian artery but extend distally into the infrarenal abdominal aorta, and they often reach the aortic bifurcation. Extent III repairs extend from the lower descending thoracic aorta (below the sixth rib) and into the abdomen. Extent IV repairs begin at the diaphragmatic hiatus and often involve the entire abdominal aorta.Descending thoracic aortic aneurysms not amenable to endovascular therapy are currently repaired through a left thoracotomy. In patients with thoracoabdominal aortic aneu-rysm, the thoracotomy is extended across the costal margin and into the abdomen.110 Using a double-lumen endobronchial tube allows selective ventilation of the right lung and deflation of the left lung. Transperitoneal exposure of the thoracoabdominal aorta is achieved by performing medial visceral rotation and circumferential division of the diaphragm.


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Surgery_Schwartz. the right lung and deflation of the left lung. Transperitoneal exposure of the thoracoabdominal aorta is achieved by performing medial visceral rotation and circumferential division of the diaphragm. During a period of aortic clamping, the diseased segment is replaced with a polyes-ter tube graft. Important branch arteries—including intercostal arteries and the celiac, superior mesenteric, and renal arteries—are reattached to openings made in the side of the graft. In patients with Marfan syndrome and other heritable conditions, separate (8and 10-mm) grafts to the visceral branches are often used to prevent subsequent “patch aneurysms” that can develop in residual aortic tissue.111 Visceral and renal artery occlusive dis-ease is commonly encountered during aneurysm repair; options for correcting branch-vessel stenosis include endarterectomy, direct arterial stenting, and bypass grafting.Clamping the descending thoracic aorta causes ischemia of the spinal cord and abdominal viscera.


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Surgery_Schwartz. branch-vessel stenosis include endarterectomy, direct arterial stenting, and bypass grafting.Clamping the descending thoracic aorta causes ischemia of the spinal cord and abdominal viscera. Clinically significant manifestations of hepatic, pancreatic, and bowel ischemia are relatively uncommon. However, both acute renal failure and spinal cord injury resulting in paraplegia or paraparesis remain major causes of morbidity and mortality after these operations. Therefore, several aspects of the operation are devoted to minimizing spinal and renal ischemia (Table 22-3). Our multimodal approach to spinal cord protection includes expeditious repair to minimize aortic clamping time, moderate systemic heparinization (1.0 mg/kg) to prevent small-vessel AB5-FrenchsheathMarked pigtailcatheterDeliverysheathStiffguidewireUndeployedendograftCBrunicardi_Ch22_p0853-p0896.indd 86901/03/19 5:41 PM 870SPECIFIC CONSIDERATIONSPART IIFigure 22-13. Illustration of the Crawford classification of


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Surgery_Schwartz. 86901/03/19 5:41 PM 870SPECIFIC CONSIDERATIONSPART IIFigure 22-13. Illustration of the Crawford classification of thora-coabdominal aortic aneurysm repair, based on the extent of aortic replacement. (Used with permission from Baylor College of Medicine.)Right commoncarotid arteryInnominatearteryLeft commoncarotid arteryLeft subclavianarteryLanding Zone ClassificationsFigure 22-12. Illustration of the Criado landing zones, which are used to describe aortic anatomy during thoracic endovascular repair. The arch is the short segment that includes the origins of the three brachiocephalic arteries—the innominate artery, the left com-mon carotid artery, and the left subclavian artery. Zone 0 includes the ascending aorta and the origin of the innominate artery. Zone 1 includes the origin of the left common carotid artery. Zone 2 includes the left subclavian artery origin. Zone 3 is a short section of the aorta that comprises the 2 cm immediately distal to the origin of the left


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Surgery_Schwartz. of the left common carotid artery. Zone 2 includes the left subclavian artery origin. Zone 3 is a short section of the aorta that comprises the 2 cm immediately distal to the origin of the left subclavian artery, and zone 4 begins where zone 3 ends. (Used with permission from Baylor College of Medicine.)Table 22-3Current strategy for spinal cord and visceral protection during repair of distal thoracic aortic aneurysmsAll extents• Permissive mild hypothermia (32°C–34°C, nasopharyngeal)• Moderate heparinization (1 mg/kg)• Aggressive reattachment of segmental arteries, especially between T8 and L1• Sequential aortic clamping when possible• Perfusion of renal arteries with 4°C crystalloid solution when possibleCrawford extent I and II thoracoabdominal repairs• Cerebrospinal fluid drainage• Left heart bypass during proximal anastomosis• Selective perfusion of celiac axis and superior mesenteric artery during intercostal and visceral anastomosesthrombosis, mild permissive hypothermia (32°C


Surgery_Schwartz

Surgery_Schwartz. heart bypass during proximal anastomosis• Selective perfusion of celiac axis and superior mesenteric artery during intercostal and visceral anastomosesthrombosis, mild permissive hypothermia (32°C to 34°C [89.6°F to 93.2°F] nasopharyngeal temperature), and reattachment of segmental intercostal and lumbar arteries. As the aorta is replaced from proximal to distal, the aortic clamp is moved sequentially to lower positions along the graft to restore perfusion to newly reattached branch vessels. During extensive thoracoabdominal aortic repairs (i.e., Crawford extent I and II repairs), cerebrospinal fluid drainage is used to improve spinal perfusion by reducing cerebrospinal fluid pressure. Because the benefits of this adjunct have been confirmed in a randomized clinical trial,112 its use is recommended in current guidelines (Class I, Level B recommendation).44 During cerebral spinal fluid drainage, the cerebral spinal fluid pressure is closely monitored, and the amount of fluid that is


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Surgery_Schwartz. recommended in current guidelines (Class I, Level B recommendation).44 During cerebral spinal fluid drainage, the cerebral spinal fluid pressure is closely monitored, and the amount of fluid that is removed is carefully limited to avoid the devastating complication of intracranial hemorrhage.113 Motor evoked potentials are used by some groups to monitor the spinal cord throughout the operation.114,115 Left heart bypass, which provides perfusion of the distal aorta and its branches during the clamping period, is also used during extensive thoracoabdominal aortic repairs.116-118 Because left heart bypass unloads the heart, it is also useful in patients with poor cardiac reserve. Balloon perfusion cannulas connected to the left heart bypass circuit can be used to deliver blood directly to the celiac axis and superior mesenteric artery during their reattachment. The potential benefits of reducing hepatic and bowel ischemia include reduced risks of postoperative coagulopathy and


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Surgery_Schwartz. to the celiac axis and superior mesenteric artery during their reattachment. The potential benefits of reducing hepatic and bowel ischemia include reduced risks of postoperative coagulopathy and bacterial translocation, respectively. Whenever possible, renal protection is achieved by perfusing the kidneys with cold (4°C [39.2°F]) crystalloid. In a randomized clinical trial, reduced kidney temperature was found to be associated with renal protection, and the use of cold crystalloid independently predicted preserved renal function.119Hypothermic circulatory arrest can also be used dur-ing descending thoracic or thoracoabdominal aortic repairs.120 At our center, the primary indication for this approach is the inability to clamp the aorta because of rupture, extremely large aneurysm size, or extension of the aneurysm into the distal transverse aortic arch, or because a prior endovascular repair hinders clamping.67As discussed previously, complete repair of extensive aneurysm involving the


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Surgery_Schwartz. of the aneurysm into the distal transverse aortic arch, or because a prior endovascular repair hinders clamping.67As discussed previously, complete repair of extensive aneurysm involving the ascending aorta, transverse arch, and descending thoracic aorta generally requires staged open 7Brunicardi_Ch22_p0853-p0896.indd 87001/03/19 5:41 PM 871THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22Figure 22-14. Illustration of the reversed elephant trunk technique using a traditional “island” approach to total aortic arch replacement. A. Stage 1: The distal aorta is repaired through a left thoracoabdominal approach. The aneurysm is opened after the aorta is clamped between the left common carotid artery and the left subclavian artery, which is also clamped. Before the proximal anastomosis is performed, the end of the graft is partly invaginated to leave a “trunk” for the subsequent repair. Proximal intercostal arteries are oversewn. B. After the proximal suture line is completed, the


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Surgery_Schwartz. is performed, the end of the graft is partly invaginated to leave a “trunk” for the subsequent repair. Proximal intercostal arteries are oversewn. B. After the proximal suture line is completed, the clamps are repositioned to restore blood flow to the left subclavian artery. The repair is completed by reattaching patent intercostal arteries to an opening in the side of the graft and creating a beveled distal anastomosis at the level of the visceral branches. C. Stage 2: The proximal aorta is repaired through a median sternotomy. The aortic arch is opened under hypothermic circulatory arrest. The “trunk” is pulled out and used to replace the aortic arch and ascending aorta. This eliminates the need for a new distal anastomosis and sim-plifies the procedure. Circulatory arrest and operative time, along with their attendant risks, are reduced. D. The completed two-stage repair of the entire thoracic aorta. (Modified with permission from Coselli JS, LeMaire SA, Carter SA, et al: The


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Surgery_Schwartz. time, along with their attendant risks, are reduced. D. The completed two-stage repair of the entire thoracic aorta. (Modified with permission from Coselli JS, LeMaire SA, Carter SA, et al: The reversed elephant trunk technique used for treatment of complex aneurysms of the entire thoracic aorta, Ann Thorac Surg. 2005 Dec;80(6):2166-2172.)operations or a hybrid approach. In such procedures, when the descending or thoracoabdominal component is symptomatic (e.g., causes back pain or has ruptured) or is disproportionately large (compared with the ascending aorta), the distal segment is treated during the initial operation, and repair of the ascend-ing aorta and transverse aortic arch is performed as a second procedure. A reversed elephant trunk repair, in which a portion of the proximal end of the aortic graft is inverted down into the lumen, can be performed during the first operation; this tech-nique facilitates the second-stage repair of the ascending aorta and transverse aortic arch


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Surgery_Schwartz. of the aortic graft is inverted down into the lumen, can be performed during the first operation; this tech-nique facilitates the second-stage repair of the ascending aorta and transverse aortic arch (Fig. 22-14).121Although spinal cord ischemia and renal failure receive the most attention, several other complications warrant consid-eration. The most common complication of extensive repairs is pulmonary dysfunction. With aneurysms adjacent to the left subclavian artery, the vagus and left recurrent laryngeal nerves are often adherent to the aortic wall and thus are susceptible to injury. Vocal cord paralysis should be suspected in patients who have postoperative hoarseness, and the presence of nerve damage should be confirmed by endoscopic examination. Vocal cord paralysis can be treated effectively by direct cord medial-ization (type 1 thyroplasty).122 Injury to the esophagus during Brunicardi_Ch22_p0853-p0896.indd 87101/03/19 5:41 PM 872SPECIFIC CONSIDERATIONSPART IIFigure


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Surgery_Schwartz. effectively by direct cord medial-ization (type 1 thyroplasty).122 Injury to the esophagus during Brunicardi_Ch22_p0853-p0896.indd 87101/03/19 5:41 PM 872SPECIFIC CONSIDERATIONSPART IIFigure 22-15. Illustration of a thoracoabdominal aortic aneurysm repair in a patient with a patent left internal thoracic artery-to-left anterior descending coronary artery graft. The proximal anastomosis is being performed while the aorta is clamped between the left common carotid and subclavian arteries. Myo-cardial perfusion is maintained through the carotid-subclavian bypass graft. (Modifed with permission from Jones MM, Akay M, Murariu D, et al: Safe aortic arch clamping in patients with patent inter-nal thoracic artery grafts. Ann Thorac Surg. 2010 Apr;89(4):e31-e32.)the proximal anastomosis can have catastrophic consequences. Carefully separating the proximal descending thoracic aorta from the underlying esophagus before performing the proximal anastomosis minimizes the risk of a secondary


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Surgery_Schwartz. have catastrophic consequences. Carefully separating the proximal descending thoracic aorta from the underlying esophagus before performing the proximal anastomosis minimizes the risk of a secondary aortoesophageal fistula. In patients who have previously undergone coronary artery bypass with a left internal thoracic artery graft, clamp-ing proximal to the left subclavian artery can precipitate severe myocardial ischemia and cardiac arrest. When the need to clamp at this location is anticipated in these patients, a left common carotid-to-subclavian bypass is performed to prevent cardiac complications (Fig. 22-15).123Endovascular Repair Descending Thoracic Aortic Aneurysms Stent graft repair has become the standard treatment for patients with descending thoracic aortic aneurysm.55,56,124 Although aortic repair with a self-fixing endoprosthesis was reported by Volodos103,104 in the mid 1980s, it was the report by Parodi and associates125 of using endovascular stent grafting to repair


Surgery_Schwartz

Surgery_Schwartz. Although aortic repair with a self-fixing endoprosthesis was reported by Volodos103,104 in the mid 1980s, it was the report by Parodi and associates125 of using endovascular stent grafting to repair abdominal aortic aneurysm that launched widespread interest in developing this approach. Only 3 years after this seminal report was published, Dake and colleagues126 reported performing endovascular descending tho-racic aortic repair with “homemade” stent grafts in 13 patients.Guidelines for the use of endovascular repair in thoracic aortic disease have been published,44 and reporting standards to uniformly describe the endovascular repair process have been established.127 Although endografting was initially approved to treat degenerative descending thoracic aortic aneurysm, newer devices have been approved for use in treating various descending thoracic aortic pathologies, including blunt aortic injury, penetrating aortic ulcer (see following section), coarcta-tion, and dissection.


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Surgery_Schwartz. have been approved for use in treating various descending thoracic aortic pathologies, including blunt aortic injury, penetrating aortic ulcer (see following section), coarcta-tion, and dissection. Although the use of stent grafts in cases of aortic infection is not ideal, patients with a fistula or mycotic aneurysm are sometimes treated with endovascular devices as a bridge to open repair.In elderly patients with severe comorbidity and patients who have undergone previous complex thoracic aortic procedures, endovascular repair is a particularly attractive alternative to stan-dard open surgical procedures.128 Patients who undergo endo-vascular repair tend to have a lower incidence of intraoperative complications, a shorter length of stay, and a higher likelihood of being discharged to home than those who undergo open repair.129 As mentioned previously, appropriate patient selection depends on specific measurements taken from preoperative CT angiograms.To protect patients against


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Surgery_Schwartz. home than those who undergo open repair.129 As mentioned previously, appropriate patient selection depends on specific measurements taken from preoperative CT angiograms.To protect patients against spinal cord ischemia during endovascular repair of the descending thoracic aorta, the most important maneuver is to keep the mean arterial perfusion pres-sure between 90 and 110 mmHg after the endograft is deployed. In patients who have had previous open or endovascular abdom-inal aortic aneurysm repair, cerebrospinal fluid drainage is rec-ommended.130 The first step in the repair procedure is to obtain appropriate vascular access for the insertion of the thoracic stent graft. If the femoral artery will not accommodate the necessary Brunicardi_Ch22_p0853-p0896.indd 87201/03/19 5:41 PM 873THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22sheath, then an iliac artery is exposed. If necessary, a graft can be sewn to the iliac artery in an end-to-side fashion to facilitate the deployment of


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Surgery_Schwartz. ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22sheath, then an iliac artery is exposed. If necessary, a graft can be sewn to the iliac artery in an end-to-side fashion to facilitate the deployment of the endograft. After 5,000 to 10,000 units of heparin are administered, a guidewire and the delivery sheath are typically inserted into the access artery under fluoroscopic guidance; depending on which endovascular device is used, the stent graft can be advanced through a sheath or with no sheath. The endograft is then advanced into the aorta and suitably posi-tioned. Note that the best view of the distal arch and descending thoracic aorta is usually in the left anterior oblique position at an angle of approximately 40° to 50°. The device is then deployed, and the proximal and distal ends can be ballooned for better apposition of the stent graft to the aortic wall. An aortogram is then performed to rule out any endoleak, and protamine is administered. As an alternative to aortography,


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Surgery_Schwartz. can be ballooned for better apposition of the stent graft to the aortic wall. An aortogram is then performed to rule out any endoleak, and protamine is administered. As an alternative to aortography, intravascular ultrasonography (IVUS) can be used to identify the proximal and distal landing zones, and the entire procedure can be per-formed with minimal or no contrast.Although it is not uncommon to cover the left subcla-vian artery with the endograft to lengthen the proximal landing zone,131 findings suggest that the risk of spinal cord complica-tions is heightened when the subclavian artery is covered and not revascularized, presumably because of a loss of collateral circulation to the spinal cord.132 To prevent this complication, a carotid-to-subclavian bypass can be easily constructed to main-tain vertebral artery blood flow and minimize neurologic injury (Fig. 22-16).133,134 In addition, recent studies suggest that revas-cularization of the left subclavian artery is associated


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Surgery_Schwartz. to main-tain vertebral artery blood flow and minimize neurologic injury (Fig. 22-16).133,134 In addition, recent studies suggest that revas-cularization of the left subclavian artery is associated with lower stroke risk in patients in whom an endograft was deployed in Zone 2 and covered the left subclavian artery.135 In addition, new generations of stent grafts are being designed with side branches that can be placed within the left subclavian artery. This feature is particularly attractive if the proximal neck is short or if the patient has a patent left internal thoracic artery-to-left anterior descending coronary artery bypass. Indications for left subclavian artery revascularization include previous coro-nary artery bypass with patent internal thoracic artery, dominant left vertebral artery, aneurysm arising from the left subclavian artery, left arm arterio-venous fistula, and coverage of a long segment of the descending thoracic aorta.Elephant Trunk Completion In select patients,


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Surgery_Schwartz. aneurysm arising from the left subclavian artery, left arm arterio-venous fistula, and coverage of a long segment of the descending thoracic aorta.Elephant Trunk Completion In select patients, elephant trunk completion repairs can be done with an endovascular approach (see Fig. 22-8C), rather than by the traditional open operation through a thoracotomy.136 Recall that an elephant trunk is used when an aortic aneurysm extends from the distal arch to the descending thoracic aorta. An endograft can be deployed at the time of elephant trunk construction or during a separate, subse-quent procedure.97,107,137 When the stent is deployed in a retro-grade manner during a second-stage procedure, the procedure is facilitated by placing radiopaque markers at the end of the elephant trunk during the first-stage procedure. This allows the distal end of the trunk to be identified via fluoroscopy. A guide-wire can then be manipulated into the trunk and advanced into the ascending aorta to stabilize


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Surgery_Schwartz. first-stage procedure. This allows the distal end of the trunk to be identified via fluoroscopy. A guide-wire can then be manipulated into the trunk and advanced into the ascending aorta to stabilize it during stent deployment. Note that advancing a wire in retrograde fashion from the femoral artery into the elephant trunk can be challenging. Occasionally, the wire must be advanced in an antegrade fashion from a bra-chial artery. The frozen elephant trunk technique—in which a short stent graft is delivered antegrade inside the trunk—can be used to perform the entire repair in one stage or to facilitate the second stage.89,90Thoracoabdominal Aortic Aneurysms Although endovascular thoracoabdominal aortic aneurysm repair remains experimental, it has been shown to be feasible in a handful of specialized cen-ters. Endovascular thoracoabdominal aortic aneurysm repairs are quite complex, because at least one of the visceral arteries is incorporated into the repair. The number of visceral


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Surgery_Schwartz. of specialized cen-ters. Endovascular thoracoabdominal aortic aneurysm repairs are quite complex, because at least one of the visceral arteries is incorporated into the repair. The number of visceral branches that need to be addressed varies with the extent of aortic coverage.138 The types of stent grafts used include fenestrated grafts, reinforced fenestrated grafts, branched or cuffed grafts, modular combinations of grafts, and multilayer stents.139 Graft fenestrations and branch vessels are typically aligned by using inflatable angioplasty balloons. Procedure time is not insignifi-cant, nor is the amount of contrast medium required to obtain the highly detailed images needed to plan these procedures. In addi-tion, some of the stent grafts used in endovascular thoracoab-dominal aortic aneurysm repair are custom-made in advance and thus may take several weeks to obtain; therefore, their use is limited to cases of elective repair.107 In efforts to hasten repair and utilize


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Surgery_Schwartz. aortic aneurysm repair are custom-made in advance and thus may take several weeks to obtain; therefore, their use is limited to cases of elective repair.107 In efforts to hasten repair and utilize off-the-shelf devices, parallel graft approaches, which use a combination of largeand small-diameter stents, have been reported.140 And, although some centers now propose distal coverage of the celiac axis141 for extent I thoracoabdomi-nal aortic aneurysm repairs, this potentially risky approach is not widely used.It should be noted that, like open thoracoabdominal aortic aneurysm repair, endovascular repair carries risks of paraplegia, renal failure, stroke, and death, despite the apparent benefits of its being a less invasive procedure. Notably, reports from centers experienced in endovascular thoracoabdominal aortic repair primarily describe limited extent IV repairs.64 Although the technology is progressing rapidly, at present endovascular thoracoabdominal aortic aneurysm repair should


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Surgery_Schwartz. thoracoabdominal aortic repair primarily describe limited extent IV repairs.64 Although the technology is progressing rapidly, at present endovascular thoracoabdominal aortic aneurysm repair should be considered investigational.Hybrid Repair Extensive hybrid thoracoabdominal aortic aneurysm repair142,143 can be a life-saving option in patients at high surgical risk, such as those who have limited physiologic reserve, are of advanced age, or have significant comorbidities. Hybrid procedures use open surgical techniques to reroute blood supply to the visceral arteries so that their aortic origins can be covered by stent grafts without causing visceral ischemia (Fig. 22-17). Endovascular methods are then used (either as part of the same procedure or at a later stage) to repair the aor-tic aneurysm, often with simple tube stent grafts; such devices are more readily available than the customized, modular stent grafts deployed in strictly endovascular repairs. Overall, results for hybrid


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Surgery_Schwartz. aneurysm, often with simple tube stent grafts; such devices are more readily available than the customized, modular stent grafts deployed in strictly endovascular repairs. Overall, results for hybrid thoracoabdominal aortic aneurysm repair have been somewhat disappointing.144 However, a handful of centers report acceptable outcomes in high-risk patients, particularly when a staged hybrid approach is used.145Postoperative Considerations Open Procedures Aortic anastomoses are often extremely fragile during the early postoperative period. Even brief episodes of postoperative hypertension can disrupt suture lines and precipitate severe bleeding or pseudoaneurysm formation. Therefore, during the initial 24 to 48 hours, meticulous blood pressure control is maintained to protect the integrity of the anastomoses. Generally, we liberally use IV vasoactive agents to keep the mean arterial blood pressure between 80 and 90 mmHg. In patients with extremely friable aortic tissue, such as those


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Surgery_Schwartz. of the anastomoses. Generally, we liberally use IV vasoactive agents to keep the mean arterial blood pressure between 80 and 90 mmHg. In patients with extremely friable aortic tissue, such as those with Marfan syndrome, we lower the target range to 70 to 80 mmHg. It is a delicate balancing act because one must be Brunicardi_Ch22_p0853-p0896.indd 87301/03/19 5:41 PM 874SPECIFIC CONSIDERATIONSPART IIFigure 22-16. Illustration of a “Zone 2” hybrid repair of the proximal descending thoracic aorta. A. The preoperative representation of the aneurysm shows that establishing a 2-cm proximal landing zone for a stent graft will require covering the origin of the left subclavian artery. B. Through a supraclavicular approach, a bypass from the left common carotid artery to the left subclavian artery is performed to reroute circulation and create a landing zone for the stent graft. After the bypass is completed, the left subclavian artery is ligated proximal to the graft. C. In the completed


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Surgery_Schwartz. is performed to reroute circulation and create a landing zone for the stent graft. After the bypass is completed, the left subclavian artery is ligated proximal to the graft. C. In the completed hybrid repair, the aneurysm has been excluded successfully by a stent graft that covers the origin of the left subclavian artery, and the proximal landing zone of the endograft is within zone 2. Importantly, blood flow to the left vertebral artery and arm is preserved by the bypass graft. (Reproduced with permission from Bozinovski J, LeMaire SA, Weldon SA: Hybrid Repairs of the Distal Aortic Arch and Proximal Descending Thoracic Aorta, Oper Tech Thorac Cardiovasc Surg 2007;12(3):167-177.)VertebralarterySubclavianarteryPhrenicnerveAnterior scalenemuscle (divided)Internal thoracicarterySternocleidomastoidmuscle (divided)Commoncarotid arteryVagusnerveABCBrunicardi_Ch22_p0853-p0896.indd 87401/03/19 5:41 PM 875THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22Figure 22-17. Illustration of a


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Surgery_Schwartz. (divided)Commoncarotid arteryVagusnerveABCBrunicardi_Ch22_p0853-p0896.indd 87401/03/19 5:41 PM 875THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22Figure 22-17. Illustration of a “Zone 0” hybrid approach—which combines open and endovascular techniques—for repair of an extensive aortic aneurysm. Debranching the arch and thoracoab-dominal segments allows the use of a series of endovascular stent grafts to exclude the entire aneurysm. Note that the arterial inflow for the debranched visceral arteries comes from the left common iliac artery.Table 22-4Classification of and common treatment strategies for endoleakType I• Incomplete seal between stent graft and aorta at the proximal landing site (Type Ia), the distal landing site (Type Ib), or branch module, fenestration, or plug (Type Ic)• Early reintervention to improve seal or conversion to open surgeryType II• Retrograde perfusion of sac from excluded collateral arteries• Surveillance; as-needed occlusion with percutaneous or other


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Surgery_Schwartz. reintervention to improve seal or conversion to open surgeryType II• Retrograde perfusion of sac from excluded collateral arteries• Surveillance; as-needed occlusion with percutaneous or other interventionsType III• Incomplete seal between overlapping stent graft or module (Type IIIa), or tear in graft fabric (Type IIIb)• Early reintervention to cover or conversion to open surgeryType IV• Perfusion of sac due to porosity of material• Surveillance; as-needed reintervention to reline stent graftType V• Expansion of sac with no identifiable source• Surveillance; as-needed reintervention to reline stent graftmindful of spinal cord perfusion and avoid periods of relative hypotension while maintaining these low pressures.Endovascular Procedures Many of the complications are directly related to manipulation of the delivery system within the iliac arteries and aorta.146 Patients with small, calcified, tor-tuous iliofemoral arteries are at particularly high risk for life-threatening iliac


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Surgery_Schwartz. to manipulation of the delivery system within the iliac arteries and aorta.146 Patients with small, calcified, tor-tuous iliofemoral arteries are at particularly high risk for life-threatening iliac artery rupture. Although relatively uncommon, acute iatrogenic retrograde dissection into the aortic arch and ascending aorta is a life-threatening complication that neces-sitates emergency repair of the ascending aorta and aortic arch via sternotomy and cardiopulmonary bypass.109 The most important risk factors for this complication include incautious wire and catheter manipulation, aggressive proximal ballooning (especially in cases of acute descending thoracic aortic dissection), and hybrid arch repair in which the native ascending aorta is dilated (more than 4 cm). Retrograde proximal dissection con-verts a localized descending thoracic aortic aneurysm into an acute problem involving the entire thoracic aorta. Of note, ret-rograde aortic dissection may also occur several months after


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Surgery_Schwartz. con-verts a localized descending thoracic aortic aneurysm into an acute problem involving the entire thoracic aorta. Of note, ret-rograde aortic dissection may also occur several months after initial repair.147Another significant complication of descending thoracic aortic stent grafting is endoleak. An endoleak occurs when there is a persistent flow of blood (visible on radiologic imaging) into the aneurysm sac, and it may occur during the initial proce-dure or develop over time. Although endoleaks are a relatively common complication,148,149 they are not benign because they lead to continual pressurization of the sac, which can cause expansion or even rupture. These complications are categorized (Table 22-4) according to the site of the leak.127 Although all endoleaks may progress such that they can be considered life-threatening, type I and type III endoleaks generally necessitate early and aggressive intervention. Recently published reporting guidelines aid standardized


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Surgery_Schwartz. such that they can be considered life-threatening, type I and type III endoleaks generally necessitate early and aggressive intervention. Recently published reporting guidelines aid standardized reporting.127Other complications include stent graft misdeployment, device migration, endograft kinking or infolding, and stent graft infection, including fistula. Although not all complications related to stent grafts are fatal, endovascular repairs should be performed by expert teams qualified to address the variety of problems that may arise; some patients may need to have these devices removed and replaced with polyester grafts.67,68,150,151 Complications of endovascular repair are relatively common, so regularly scheduled radiologic imaging surveillance is of the utmost importance.Brunicardi_Ch22_p0853-p0896.indd 87501/03/19 5:41 PM 876SPECIFIC CONSIDERATIONSPART IIAORTIC DISSECTIONPathology and ClassificationAortic dissection, the most common catastrophic event involving the aorta,


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Surgery_Schwartz. 87501/03/19 5:41 PM 876SPECIFIC CONSIDERATIONSPART IIAORTIC DISSECTIONPathology and ClassificationAortic dissection, the most common catastrophic event involving the aorta, is a progressive separation of the aortic wall layers that usually occurs after a tear forms in the intima and inner media. As the separation of the layers of the media propagates, two channels are typically formed (Fig. 22-18): the original lumen, which remains lined by the intima and which is called the true lumen, and the newly formed channel within the layers of the media, which is called the false lumen. The dissecting membrane separates the true and false lumens. Additional tears in the dis-secting membrane that allow communication between the two channels are called reentry sites. Although the separation of lay-ers primarily progresses distally along the length of the aorta, it can also proceed in a proximal direction; this process often is referred to as proximal extension or retrograde dissection.The


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Surgery_Schwartz. lay-ers primarily progresses distally along the length of the aorta, it can also proceed in a proximal direction; this process often is referred to as proximal extension or retrograde dissection.The extensive disruption of the aortic wall has severe anatomic consequences (Fig. 22-19). First, the outer wall of the false lumen is extremely thin, inflamed, and fragile, which makes it prone to expansion or rupture in the face of ongoing hemodynamic stress. Second, the expanding false lumen can compress the true lumen and cause malperfusion syndrome by interfering with blood flow in the aorta or any of its branch vessels, including the coronary, carotid, inter-costal, visceral, renal, and iliac arteries. Finally, when the separation of layers occurs within the aortic root, the aortic valve commissures can become unhinged, which results in acute valvular regurgitation. The clinical consequences of each of these sequelae are addressed in detail in the section on clinical


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Surgery_Schwartz. the aortic valve commissures can become unhinged, which results in acute valvular regurgitation. The clinical consequences of each of these sequelae are addressed in detail in the section on clinical manifestations.Dissection vs. Aneurysm. The relationship between dissec-tion and aneurysmal disease requires clarification. Dissection and aneurysm are separate entities, although they often coexist and are mutual risk factors. In some cases, dissection occurs in patients without aneurysms, and the subsequent progressive dilatation of the weakened outer aortic wall ultimately results in an aneurysm. On the other hand, in patients with degenera-tive aneurysms, the ongoing deterioration of the aortic wall can lead to a superimposed dissection. The overused term dissecting aneurysm should be reserved for this specific situation.Classification. For management purposes, aortic dissec-tions are classified according to their location and chronicity. Improvements in imaging have increasingly


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Surgery_Schwartz. reserved for this specific situation.Classification. For management purposes, aortic dissec-tions are classified according to their location and chronicity. Improvements in imaging have increasingly revealed variants of aortic dissection that probably represent different forms along the spectrum of this condition.Location To guide treatment, dissections are categorized according to their anatomic location and extent. The two tra-ditional classification schemes that remain in common use are the DeBakey and the Stanford classification systems (Fig. 22-20).152,153 In their current forms, both of these schemes describe the segments of aorta that are involved in the dissec-tion, rather than the site of the initial intimal tear. The main drawback of the Stanford classification system is that it does not distinguish between patients with isolated ascending aor-tic dissection and patients with dissection involving the entire aorta. Both types of patients would be classified as having type A


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Surgery_Schwartz. does not distinguish between patients with isolated ascending aor-tic dissection and patients with dissection involving the entire aorta. Both types of patients would be classified as having type A dissections, despite the fact that their treatment, follow-up, and prognosis are substantially different.Additional classification schemas include that by Borst and associates,154 in which the ascending and descending aorta are considered independently; the recent modification of the DeBakey classification by Tsagakis et al,155 which extends type II dissection into the aortic arch; and the Penn modification of the Stanford classification,156,157 which expands the classification to include the presence of tissue and global malperfusion. These modifications may help to better streamline the primary surgical intervention.Normal aortaAortic dissectionIntramural hematomaPenetrating aortic ulcerFigure 22-18. Illustration of longitudinal sections of the aortic wall and lumen. Blood flows freely


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Surgery_Schwartz. surgical intervention.Normal aortaAortic dissectionIntramural hematomaPenetrating aortic ulcerFigure 22-18. Illustration of longitudinal sections of the aortic wall and lumen. Blood flows freely downstream in normal aortic tissue. In classic aortic dissection, blood entering the media through a tear creates a false channel in the wall. Intramural hematomas arise when hemor-rhage from the vasa vasorum causes blood to collect within the media; the intima is intact. Penetrating aortic ulcers are deep atherosclerotic lesions that burrow into the aortic wall and allow blood to enter the media. In each of these conditions, the outer aortic wall is severely weakened and prone to rupture.Brunicardi_Ch22_p0853-p0896.indd 87601/03/19 5:42 PM 877THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22Figure 22-19. Illustration of the potential anatomic consequences of aortic dissection, with a mapped diagram of affected regions (inset). A. Ascending aortic rupture and cardiac tamponade. B.


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Surgery_Schwartz. 22Figure 22-19. Illustration of the potential anatomic consequences of aortic dissection, with a mapped diagram of affected regions (inset). A. Ascending aortic rupture and cardiac tamponade. B. Disruption of coronary blood flow. C. Injury to the aortic valve causing regurgitation. D, E, and F. Compromised blood flow to branch vessels, causing ischemic complications. (Adapted with permission from Creager MA, Dzau VS, Loscalzo J: Vascular Medicine, 7th ed. Philadelphia, PA: Elsevier/Saunders; 2006.)Figure 22-20. Illustration of the classification schemes for aortic dissection based on which portions of the aorta are involved. Dissection can be confined to the ascending aorta (left) or the descending aorta (middle), or it can involve the entire aorta (right). (Used with permission from Baylor College of Medicine.)ABCDEFBrunicardi_Ch22_p0853-p0896.indd 87701/03/19 5:42 PM 878SPECIFIC CONSIDERATIONSPART IIContrast-enhanced CT scanTransfer to operatingroom, intubation,diagnostic


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Surgery_Schwartz. Baylor College of Medicine.)ABCDEFBrunicardi_Ch22_p0853-p0896.indd 87701/03/19 5:42 PM 878SPECIFIC CONSIDERATIONSPART IIContrast-enhanced CT scanTransfer to operatingroom, intubation,diagnostic TEESuspected acutedissectionAortic dissection?Ascending aorticdissection (Stanford A orDeBakey I or II)?Secondary diagnosticstudy (MRA, TEE, oraortography)Emergency operationEmergency operationTransfer to intensive carefor further stabilizationand diagnostic work-upTransfer to intensive care unitfor blood pressure control,anti-impulse therapy Emergency endovascular(fenestration, stent) oropen interventionYesYesYesYesYesYesNoNoNoNoNoNoFurther diagnosticwork-upHemodynamicallystable?Anti-impulse therapy(beta blockers),blood pressure controlAortic dissection?Complicated descendingaortic dissection (malperfusion, rupture)?Management of acute aortic dissectionAscending aorticdissection (Stanford A orDeBakey I or II)?Figure 22-21. Algorithm used to facilitate decisions regarding treatment of


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Surgery_Schwartz. (malperfusion, rupture)?Management of acute aortic dissectionAscending aorticdissection (Stanford A orDeBakey I or II)?Figure 22-21. Algorithm used to facilitate decisions regarding treatment of acute aortic dissection. CT = computed tomography; MRA = magnetic resonance angiography; TEE = transesophageal echocardiography.Regardless of which system is used, patients with isolated ascending aortic dissection usually undergo emergent opera-tion, as do patients with dissection involving both the ascend-ing and descending thoracic segments. Patients with isolated descending thoracic and abdominal aortic dissection are typi-cally treated medically, unless complications requiring surgery develop. Understanding the precise extent of dissection has become increasingly important as some aortic centers consider augmenting traditional ascending aortic repairs with endovascu-lar techniques to treat dissected distal aortic segments.158Chronicity Aortic dissection also is categorized according to


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Surgery_Schwartz. consider augmenting traditional ascending aortic repairs with endovascu-lar techniques to treat dissected distal aortic segments.158Chronicity Aortic dissection also is categorized according to the time elapsed since the initial tear. Dissection is considered acute within the first 14 days after the initial tear; after 14 days, the dissection is considered chronic. Although arbitrary, the dis-tinction between acute and chronic dissections has important implications, not only for decision making about perioperative management strategies and operative techniques, but also for evaluating surgical results. Figure 22-21 provides an algorithm for the management of acute aortic dissection. In light of the importance of acuity, Borst and associates154 have proposed a third phase—termed subacute—to describe the transition between the acute and chronic phases. The subacute period encompasses days 15 through 60 after the initial tear. Although this is past the traditional 14-day acute phase,


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Surgery_Schwartz. describe the transition between the acute and chronic phases. The subacute period encompasses days 15 through 60 after the initial tear. Although this is past the traditional 14-day acute phase, patients with subacute dissection continue to have extremely fragile aortic Brunicardi_Ch22_p0853-p0896.indd 87801/03/19 5:42 PM 879THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22tissue, which may complicate operative treatment and increase the risks associated with surgery. Recently, the International Registry of Acute Aortic Dissections (IRAD) investigators pro-posed a new classification system for characterizing the phases of aortic dissection: The period within 24 hours from the onset of symptoms was defined as hyperacute, the period between 2 and 7 days was defined as acute, the period between 8 and 30 days was defined as subacute, and the period beyond 30 days was defined as chronic.159Variants As noted earlier, advancements in noninvasive imag-ing of the aorta have revealed


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Surgery_Schwartz. between 8 and 30 days was defined as subacute, and the period beyond 30 days was defined as chronic.159Variants As noted earlier, advancements in noninvasive imag-ing of the aorta have revealed variants of aortic dissection (see Fig. 22-18). The recently introduced term acute aortic syn-drome encompasses classic aortic dissection and its variants. Other aortic syndromes, which were once thought to be rare, include intramural hematoma (IMH) and penetrating aortic ulcer (PAU). Although the issue is somewhat controversial, the current consensus is that, in most cases, these variants of dissec-tion should be treated identically to classic dissection.An IMH is a collection of blood within the aortic wall, without an intimal tear, that is believed to be due to rupture of the vasa vasorum within the media. The accumulation of blood can result in a secondary intimal tear that ultimately leads to a dissection.160 Because IMH and aortic dissection represent a continuum, it is possible that IMH


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Surgery_Schwartz. the media. The accumulation of blood can result in a secondary intimal tear that ultimately leads to a dissection.160 Because IMH and aortic dissection represent a continuum, it is possible that IMH is seen less frequently than aortic dissection because IMH rapidly progresses to true dissec-tion. The prevalence of IMH among patients with acute aortic syndromes is approximately 6%, and 16% progress to full dis-section.161 An IMH can be classified according to its location (i.e., ascending or descending) and should be treated analo-gously to classic dissection.162A PAU is essentially a disrupted atherosclerotic plaque that projects into the aortic wall and is associated with surround-ing hematoma. Eventually, the ulcer can penetrate the aortic wall, which leads to dissection or rupture. The rate of disease progression is higher than that of IMH alone.163Causes and Clinical HistoryAortic dissection is a lethal condition with a reported incidence of 3.5 per 100,000 in the United


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Surgery_Schwartz. The rate of disease progression is higher than that of IMH alone.163Causes and Clinical HistoryAortic dissection is a lethal condition with a reported incidence of 3.5 per 100,000 in the United States.164 Without appropriate mod-ern medical or surgical treatment, most patients (approximately 90%) die within 3 months of dissection, mostly from rupture.165,166Although several risk factors for aortic dissection have been identified, the specific causes remain unknown. Ultimately, any condition that weakens the aortic wall increases the risk of aortic dissection. Common general cardiovascular risk factors, such as smoking, hypertension, atherosclerosis, and hypercholesterolemia, are associated with aortic dissection. Patients with heritable forms of aortopathy, aortitis, bicuspid aortic valve, or preexisting medial degenerative disease are at risk for dissection, especially if they already have a thoracic aortic aneurysm.24 Aortic injury during cardiac catheterization, surgery, or


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Surgery_Schwartz. valve, or preexisting medial degenerative disease are at risk for dissection, especially if they already have a thoracic aortic aneurysm.24 Aortic injury during cardiac catheterization, surgery, or endovascular aortic repair is a common cause of iatrogenic dissection. Other conditions that are associated with aortic dissection include cocaine and amphetamine abuse,167 as well as severe emotional stress or extreme physical exertion such as during weightlifting.168 Advances in the understanding of the molecular mechanisms behind abdominal aortic aneu-rysms have prompted similar investigations of thoracic aortic dissection.169-171Clinical ManifestationsThe onset of dissection often is associated with severe chest or back pain, classically described as “tearing,” that migrates Table 22-5Anatomic complications of aortic dissection and their associated symptoms and signsANATOMIC MANIFESTATIONSYMPTOMS AND SIGNSAortic valve insufficiencyDyspneaMurmurPulmonary ralesShockCoronary


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Surgery_Schwartz. 22-5Anatomic complications of aortic dissection and their associated symptoms and signsANATOMIC MANIFESTATIONSYMPTOMS AND SIGNSAortic valve insufficiencyDyspneaMurmurPulmonary ralesShockCoronary malperfusionChest pain with characteristics of anginaNausea/vomitingShockIschemic changes on electrocardiogramElevated cardiac enzymesPericardial tamponadeDyspneaJugular venous distensionPulsus paradoxusMuffled cardiac tonesShockLow-voltage electrocardiogramSubclavian or iliofemoral artery malperfusionCold, painful extremityExtremity sensory and motor deficitsPeripheral pulse deficitCarotid artery malperfusionSyncopeFocal neurologic deficit (transient or persistent)Carotid pulse deficitComaSpinal malperfusionParaplegiaIncontinenceMesenteric malperfusionNausea/vomitingAbdominal painRenal malperfusionOliguria or anuriaHematuriadistally as the dissection progresses along the length of the aorta. The location of the pain often indicates which aortic segments are involved. Pain in the anterior


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Surgery_Schwartz. or anuriaHematuriadistally as the dissection progresses along the length of the aorta. The location of the pain often indicates which aortic segments are involved. Pain in the anterior chest suggests involvement of the ascending aorta, whereas pain in the back and abdomen generally indicates involvement of the descending and thora-coabdominal aorta. Additional clinical sequelae of acute aortic dissection vary substantially and are best considered in terms of the dissection’s potential anatomic manifestations at each level of the aorta (see Fig. 22-19 and Table 22-5). Thus, potential complications of dissection of the aorta (and involved second-ary arteries) may include cardiac ischemia (coronary artery) or tamponade, stroke (brachiocephalic arteries), paraplegia or paraparesis (intercostal arteries), mesenteric ischemia (superior mesenteric artery), kidney failure (renal arteries), and limb isch-emia or loss of motor function (brachial or femoral arteries).Ascending aortic dissection


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Surgery_Schwartz. arteries), mesenteric ischemia (superior mesenteric artery), kidney failure (renal arteries), and limb isch-emia or loss of motor function (brachial or femoral arteries).Ascending aortic dissection can directly injure the aortic valve, causing regurgitation. The severity of the regurgitation varies with the degree of commissural disruption, which ranges from partial separation of only one commissure, producing mild Brunicardi_Ch22_p0853-p0896.indd 87901/03/19 5:42 PM 880SPECIFIC CONSIDERATIONSPART IIvalvular regurgitation, to full separation of all three commis-sures and complete prolapse of the valve into the left ventricle, producing severe acute heart failure. Patients with acute aortic valve regurgitation may report rapidly worsening dyspnea.Ascending dissections also can extend into the coronary arteries or shear the coronary ostia off of the true lumen, caus-ing acute coronary occlusion; when this occurs, it most often involves the right coronary artery. The sudden


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Surgery_Schwartz. extend into the coronary arteries or shear the coronary ostia off of the true lumen, caus-ing acute coronary occlusion; when this occurs, it most often involves the right coronary artery. The sudden disruption of coronary blood flow can cause a myocardial infarction. This presentation of acute myocardial ischemia can mask the pres-ence of aortic dissection, which results in delayed diagnosis and treatment.172The thin and inflamed outer wall of a dissected ascend-ing aorta often produces a serosanguineous pericardial effusion that can accumulate and cause tamponade. Suggestive signs include jugular venous distention, muffled heart tones, pulsus paradoxus, and low-voltage electrocardiogram (ECG) tracings. Free rupture into the pericardial space produces rapid tampon-ade and is generally fatal.As the dissection progresses, any branch vessel from the aorta can become involved, which results in compromised blood flow and ischemic complications (i.e., malperfusion). Therefore, depending on


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Surgery_Schwartz. the dissection progresses, any branch vessel from the aorta can become involved, which results in compromised blood flow and ischemic complications (i.e., malperfusion). Therefore, depending on which arteries are involved, the dissection can produce acute stroke, paraplegia, hepatic failure, bowel infarc-tion, renal failure, or a threatened ischemic limb.Diagnostic EvaluationBecause of the variations in severity and the wide variety of potential clinical manifestations, the diagnosis of acute aortic dissection can be challenging.173-175 Only 3 out of every 100,000 patients who present to an emergency department with acute chest, back, or abdominal pain are eventually diagnosed with aortic dissection. Not surprisingly, diagnostic delays are com-mon; delays beyond 24 hours after hospitalization occur in up to 39% of cases. Unfortunately, delays in diagnosis lead to delays in treatment, which can have disastrous consequences. The European Society of Cardiology Task Force on Aortic


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Surgery_Schwartz. occur in up to 39% of cases. Unfortunately, delays in diagnosis lead to delays in treatment, which can have disastrous consequences. The European Society of Cardiology Task Force on Aortic Dis-section stated, “The main challenge in managing acute aortic dissection is to suspect and thus diagnose the disease as early as possible.”173 A recent study by the IRAD investigators exam-ined the reasons for delayed diagnosis and found that diagnosis lagged in women, as well as in patients with atypical symptoms, such as fever or mild pain (rather than severe pain).172 A high index of suspicion is critical, particularly in younger, atypical patients, who may have heritable disorders or other, less com-mon risk factors.Most patients with acute aortic dissection (80% to 90%) experience severe pain in the chest, back, or abdomen.173-175 The pain usually occurs suddenly, has a sharp or tearing quality, and often migrates distally as the dissection progresses along the aorta. For classification


Surgery_Schwartz

Surgery_Schwartz. in the chest, back, or abdomen.173-175 The pain usually occurs suddenly, has a sharp or tearing quality, and often migrates distally as the dissection progresses along the aorta. For classification purposes (acute vs. subacute vs. chronic), the onset of pain is generally considered to represent the beginning of the dissection process. Most of the other com-mon symptoms either are nonspecific or are caused by the sec-ondary manifestations of dissection.A discrepancy between the extremities in pulse, blood pressure, or both is the classic physical finding in patients with aortic dissection. It often occurs because of changes in flow in the true and false lumens, and it does not necessarily indi-cate extension into an extremity branch vessel. Involvement of the aortic arch often creates differences between the right and left arms, whereas descending aortic dissection often causes differences between the upper and lower extremities. Like symptoms, most of the physical signs after


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Surgery_Schwartz. differences between the right and left arms, whereas descending aortic dissection often causes differences between the upper and lower extremities. Like symptoms, most of the physical signs after dissection are related to the secondary manifestations and therefore vary considerably (see Table 22-5). For example, signs of stroke or a threatened ischemic limb may dominate the physical findings in patients with carotid or iliac malperfusion, respectively.Unfortunately, laboratory studies are of little help in diag-nosing acute aortic dissection. There has been continued inter-est in using D-dimer level to aid in making this diagnosis.176 Several reports indicate that D-dimer is an extremely sensitive indicator of acute aortic dissection; elevated levels are found in approximately 97% of affected patients.177 Tests that are com-monly used to detect acute coronary events—including ECG and tests for serum markers of myocardial injury—deserve spe-cial consideration and need to be interpreted


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Surgery_Schwartz. patients.177 Tests that are com-monly used to detect acute coronary events—including ECG and tests for serum markers of myocardial injury—deserve spe-cial consideration and need to be interpreted carefully. Normal ECGs and serum marker levels in patients with acute chest pain should raise suspicion about the possibility of aortic dissection. It is important to remember that ECG changes and elevated serum marker levels associated with myocardial infarction do not exclude the diagnosis of aortic dissection because dissection can cause coronary malperfusion. Of note, abnormal ECGs have recently been shown to delay the diagnosis of aortic dissection, and the possibility of aortic dissection should not be prema-turely ruled out.172,178 Similarly, although CXRs may show a widened mediastinum or abnormal aortic contour, up to 16% of patients with dissection have a normal-appearing CXR.174 The value of the CXR for detecting aortic dissection is limited, with a sensitivity of 67% and a


Surgery_Schwartz

Surgery_Schwartz. or abnormal aortic contour, up to 16% of patients with dissection have a normal-appearing CXR.174 The value of the CXR for detecting aortic dissection is limited, with a sensitivity of 67% and a specificity of 86%.179Once the diagnosis of dissection is considered, the tho-racic aorta should be imaged with CT, MRA, or echocardiogra-phy. The accuracy of these noninvasive imaging tests has all but eliminated the need for diagnostic aortography in most patients with suspected aortic dissection. Currently, the diagnosis of aor-tic dissection is usually established with contrast-enhanced CT, which has a sensitivity of 98% and a specificity of 87%, and, most importantly, acquires images swiftly.180 The classic diag-nostic feature is a double-lumen aorta (Fig. 22-22). In addition, CT scans provide essential information about the segments of the aorta involved; the acuity of the dissection; aortic dilata-tion, including the presence of preexisting degenerative aneu-rysms; and the development


Surgery_Schwartz

Surgery_Schwartz. essential information about the segments of the aorta involved; the acuity of the dissection; aortic dilata-tion, including the presence of preexisting degenerative aneu-rysms; and the development of threatening sequelae, including pericardial effusion, early aortic rupture, and branch-vessel compromise. Although MRA also provides excellent imaging (with both a sensitivity and specificity of 98%), the MR suite is not well suited for critically ill patients. In patients who cannot undergo contrast-enhanced CT or MRA, transthoracic echocar-diography can be used to establish the diagnosis.Transesophageal echocardiography (TEE) is excellent for detecting dissection, aneurysm, and IMH in the ascending aorta. In appropriate hands, TEE has a demonstrated sensitivity and specificity as high as 98% and 95%, respectively.181 Further-more, TEE offers important information about ventricular func-tion and aortic valve competency. Finally, TEE is the diagnostic modality of choice for


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Surgery_Schwartz. as high as 98% and 95%, respectively.181 Further-more, TEE offers important information about ventricular func-tion and aortic valve competency. Finally, TEE is the diagnostic modality of choice for hemodynamically unstable patients in whom the diagnosis of ascending dissection is suspected; ide-ally, these patients should be taken to the operating room, where the TEE can be performed and, if the TEE is confirmatory, sur-gery can be started immediately.In selected patients with ascending aortic dissection (i.e., those who have evidence of preexisting coronary artery dis-ease), coronary angiography can be considered before surgery. Specific relative indications in these patients include a history Brunicardi_Ch22_p0853-p0896.indd 88001/03/19 5:42 PM 881THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22of angina or myocardial infarction, a recent myocardial per-fusion study with abnormal results, previous coronary artery bypass or angioplasty, and acute ischemic changes on ECG.


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Surgery_Schwartz. DISSECTIONCHAPTER 22of angina or myocardial infarction, a recent myocardial per-fusion study with abnormal results, previous coronary artery bypass or angioplasty, and acute ischemic changes on ECG. Contraindications include hemodynamic instability, aortic rupture, and pericardial effusion.182 In our practice, patients with acute aortic dissections rarely undergo coronary angiog-raphy. However, all patients presenting for elective repair of chronic ascending dissections have diagnostic coronary angio-grams taken.Of note, when malperfusion of the renal, visceral, or lower extremity arteries develops, the patient is usually treated in an angiography suite or hybrid operating room.158 Although the dissection usually is diagnosed on CT scan, these patients also undergo aortography, during which the mechanism of the malperfusion is ascertained and, if possible, corrected. Hence, catheter-based aortography may be obsolete as a diagnostic test for dissection, but it remains beneficial for


Surgery_Schwartz

Surgery_Schwartz. the mechanism of the malperfusion is ascertained and, if possible, corrected. Hence, catheter-based aortography may be obsolete as a diagnostic test for dissection, but it remains beneficial for patients with malperfusion.TreatmentInitial Assessment and Management. Regardless of the location of the dissection, the initial treatment is the same for all patients with suspected or confirmed acute aortic dissection (see Fig. 22-21). Furthermore, because of the potential for rup-ture before the diagnosis is confirmed, aggressive pharmaco-logic management is started once there is clinical suspicion of dissection, and this treatment is continued during the diagnostic evaluation. The goals of pharmacologic treatment are to stabi-lize the dissection and prevent rupture.Patients are monitored closely in an intensive care unit. Indwelling radial arterial catheters are used to monitor blood pressure and optimize titration of antihypertensive agents. Blood pressures in a malperfused limb can


Surgery_Schwartz

Surgery_Schwartz. closely in an intensive care unit. Indwelling radial arterial catheters are used to monitor blood pressure and optimize titration of antihypertensive agents. Blood pressures in a malperfused limb can underrepresent the central aortic pressure; therefore, blood pressure is measured in the arm with the better pulse. Central venous catheters assure reliable IV access for delivering vasoactive medications. Pul-monary artery catheters are reserved for patients with severe cardiopulmonary dysfunction.In addition to confirming the diagnosis of dissection and defining its acuity and extent, the initial evaluation focuses on determining whether any of several life-threatening compli-cations are present. Particular attention is paid to changes in neurologic status, peripheral pulses, and urine output. Serial laboratory studies—including arterial blood gas concentrations, complete blood cell count, prothrombin and partial thrombo-plastin times, and serum levels of electrolytes, creatinine, blood


Surgery_Schwartz

Surgery_Schwartz. Serial laboratory studies—including arterial blood gas concentrations, complete blood cell count, prothrombin and partial thrombo-plastin times, and serum levels of electrolytes, creatinine, blood urea nitrogen, and liver enzymes—are useful for detecting organ ischemia and optimizing management.The initial management strategy, commonly described as anti-impulse therapy or blood pressure control, focuses on reducing aortic wall stress, the force of left ventricular ejection, chronotropy, and the rate of change in blood pressure (dP/dT). Reductions in dP/dT are achieved by lowering both cardiac contractility and blood pressure. The drugs initially used to accomplish these goals include IV b-adrenergic blockers, direct vasodilators, calcium channel blockers, and angiotensinconverting enzyme inhibitors. These agents are used to achieve a heart rate between 60 and 80 bpm, a systolic blood pressure between 100 and 110 mmHg, and a mean arterial blood pres-sure between 60 and 75 mmHg. These


Surgery_Schwartz

Surgery_Schwartz. inhibitors. These agents are used to achieve a heart rate between 60 and 80 bpm, a systolic blood pressure between 100 and 110 mmHg, and a mean arterial blood pres-sure between 60 and 75 mmHg. These hemodynamic targets are maintained as long as urine output remains adequate and neuro-logic function is not impaired. Achieving adequate pain control with IV opiates, such as morphine and fentanyl, is important for maintaining acceptable blood pressure control.b-Antagonists are administered to all patients with acute aortic dissections unless there are strong contraindications, such as severe heart failure, bradyarrhythmia, high-grade atrioven-tricular conduction block, or bronchospastic disease. Esmolol Figure 22-22. Computed tomographic scans showing that the aorta has been separated into two channels—the true (T) and false (F) lumens—in two patients with different phases of aortic dissection. A. An acute DeBakey type I aortic dissection. The dissecting membrane appears wavy (arrows) in


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Surgery_Schwartz. channels—the true (T) and false (F) lumens—in two patients with different phases of aortic dissection. A. An acute DeBakey type I aortic dissection. The dissecting membrane appears wavy (arrows) in the early phase of dissection. Here, the true lumen of the proximal aorta can be seen to be extensively compressed. This may lead to malperfusion of the heart. B. A chronic DeBakey type III aortic dissection. In the chronic phase, the membrane appears straighter and less mobile (arrow) because it has stabilized over time. (Used with permission of Baylor College of Medicine.)Brunicardi_Ch22_p0853-p0896.indd 88101/03/19 5:42 PM 882SPECIFIC CONSIDERATIONSPART IIcan be useful in patients with bronchospastic disease because it is a cardioselective, ultra-fast-acting agent with a short half-life. Labetalol, which causes both nonselective b-blockade and postsynaptic α1-blockade, reduces systemic vascular resistance without impairing cardiac output. Doses of b-antagonists are titrated to


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Surgery_Schwartz. Labetalol, which causes both nonselective b-blockade and postsynaptic α1-blockade, reduces systemic vascular resistance without impairing cardiac output. Doses of b-antagonists are titrated to achieve a heart rate of 60 to 80 bpm. In patients who cannot receive b-antagonists, calcium channel blockers such as diltiazem are an effective alternative. Nitroprusside, a direct vasodilator, can be administered once b-blockade is adequate. When used alone, however, nitroprusside can cause reflex increases in heart rate and contractility, elevated dP/dT, and pro-gression of aortic dissection. Enalapril and other angiotensin-converting enzyme inhibitors are useful in patients with renal malperfusion. These drugs inhibit renin release, which may improve renal blood flow.Treatment of Ascending Aortic Dissection Acute Dissection Because of the risk of aortic rupture, acute ascending aortic dissection is usually considered an absolute indication for emergency surgical repair. However, specific


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Surgery_Schwartz. Dissection Acute Dissection Because of the risk of aortic rupture, acute ascending aortic dissection is usually considered an absolute indication for emergency surgical repair. However, specific patient groups may benefit from nonoperative manage-ment or delayed operation.183 Delayed repair may be con-sidered for patients who (a) present with severe acute stroke or mesenteric ischemia, (b) are elderly and have substantial comor-bidity, (c) are in stable condition and may benefit from transfer to specialized centers, or (d) have undergone a cardiac operation in the remote past. Regarding the last group, it is important that the previous operation not be too recent; dissections that occur during the first 3 weeks after cardiac surgery pose a high risk of rupture and tamponade, and such dissections warrant early operation.184In the absence of the aforementioned circumstances, most patients with acute ascending aortic dissection undergo emer-gent graft replacement of the ascending aorta.


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Surgery_Schwartz. warrant early operation.184In the absence of the aforementioned circumstances, most patients with acute ascending aortic dissection undergo emer-gent graft replacement of the ascending aorta. Operative repair is similar to that for aneurysm of the transverse aortic arch (pre-viously described) because hypothermic circulatory arrest is commonly used regardless of the extent of repair. Immediately before the operation begins, intraoperative TEE is commonly performed to further assess baseline myocardial and valvular function and, if necessary, to confirm the diagnosis. The opera-tion is performed via a median sternotomy with cardiopulmo-nary bypass and hypothermic circulatory arrest (Fig. 22-23). In preparation for circulatory arrest, cannulas are placed in the right axillary artery (to provide arterial inflow) and in the right atrium (to provide venous drainage).94 The innominate artery is some-times used for arterial inflow if it is not dissected.185 After an appropriate level of


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Surgery_Schwartz. provide arterial inflow) and in the right atrium (to provide venous drainage).94 The innominate artery is some-times used for arterial inflow if it is not dissected.185 After an appropriate level of cooling has been achieved (approximately 24°C), cardiopulmonary bypass is stopped, and the ascending aorta is opened. The innominate artery is then occluded with a clamp or snare, and flow from the axillary artery cannula is used to provide ACP.186 Currently as a default, we use bilateral ACP with a separate perfusion catheter in the left common carotid artery to ensure perfusion of the left side of the brain. This strat-egy of performing the distal anastomosis during a brief period of circulatory arrest, often termed open distal anastomosis, obvi-ates the need to place a clamp across the fragile aorta, avoiding further aortic damage. Also, it allows the surgeon to carefully inspect the aortic arch for intimal tears. Traditionally, the entire arch is replaced only if a primary intimal tear


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Surgery_Schwartz. aorta, avoiding further aortic damage. Also, it allows the surgeon to carefully inspect the aortic arch for intimal tears. Traditionally, the entire arch is replaced only if a primary intimal tear is located in the arch or if the arch is aneurysmal; most commonly, repair is lim-ited to replacement of the entire ascending aorta or to a bev-eled “hemiarch” repair.187 Conservative repair has been shown 8to increase the likelihood of early survival.188 The distal aortic cuff is prepared by tacking the inner and outer walls together and occasionally using a small amount of surgical adhesive to obliterate the false lumen and strengthen the tissue. A polyester tube graft is sutured to the distal aortic cuff. The anastomosis between the graft and the aorta is fashioned so that blood flow will be directed into the true lumen; this often alleviates distal malperfusion problems that were present preoperatively. After the distal anastomosis has been completed and adequately rein-forced, the graft


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Surgery_Schwartz. into the true lumen; this often alleviates distal malperfusion problems that were present preoperatively. After the distal anastomosis has been completed and adequately rein-forced, the graft is deaired and clamped, full cardiopulmonary bypass is resumed, rewarming is initiated, and the proximal por-tion of the repair is started. In the absence of conditions that generally necessitate aortic root replacement (i.e., annuloaortic ectasia or heritable disorders, particularly Marfan and Loeys-Dietz syndromes), aortic valve regurgitation can be corrected by resuspending the commissures onto the outer aortic wall.189 The proximal aortic cuff is prepared with tacking sutures and occasionally a small amount of surgical adhesive before the proximal aortic anastomosis is performed.In the majority of patients who undergo surgical repair of acute ascending dissection, the dissection persists distal to the site of the operative repair; the residually dissected aorta, which generally includes at


Surgery_Schwartz

Surgery_Schwartz. of patients who undergo surgical repair of acute ascending dissection, the dissection persists distal to the site of the operative repair; the residually dissected aorta, which generally includes at least a portion of the transverse aortic arch as well as a large portion of the distal aorta, is susceptible to dil-atation over time. Extensive dilatation of the arch or distal aorta develops in 25% to 40% of survivors190,191 and often necessitates further aortic repair. Additionally, long-term survival after acute proximal aortic dissection is generally poor, and rupture of the dilated distal aorta is a common cause of late death in these patients.188,190-192The challenges that survivors of acute proximal aortic dissec-tion commonly face over time have led to the development of alter-nate acute dissection strategies such as total arch replacement193 and hybrid arch strategies to extend proximal aortic repair into the distal aorta. The goal of hybrid arch approaches in acute dis-section


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Surgery_Schwartz. dissection strategies such as total arch replacement193 and hybrid arch strategies to extend proximal aortic repair into the distal aorta. The goal of hybrid arch approaches in acute dis-section is to thrombose the residual false lumen by compressing it with the radial force that is exerted by a stent graft placed in the true lumen, thereby facilitating remodeling and prevent-ing late aneurysm formation.194,195 However, in such repairs, the compressed false lumen may continue to be perfused in a ret-rograde fashion.In Europe, Japan, and elsewhere, one-piece hybrid pros-theses are now available that incorporate a polyester graft for the proximal repair and a stent graft component for the descending aorta. The device enables single-stage “frozen elephant trunk” repair of the ascending aorta, entire aortic arch, and proximal descending thoracic aorta.196 In the United States, such devices are not currently available, so this repair is commonly done by concomitantly deploying a


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Surgery_Schwartz. aorta, entire aortic arch, and proximal descending thoracic aorta.196 In the United States, such devices are not currently available, so this repair is commonly done by concomitantly deploying a commercially available stent graft in an antegrade fashion after fully replacing the ascending aorta and aortic arch. In some variations of this off-label approach, the stent graft is directly sutured to the distal aspect of the proximal open repair, whereas in others, there may be a gap of native tissue between the open and endovascular repair. Although this technique appears to be extensively used outside the United States, and with early and mid-term success,194,197-199 only a few U.S. reports describe its use.200-203 Emerging reports describe an enhanced risk of spinal cord ischemia, a risk that is not usually associated with open arch repair. This is prob-ably due to the extensive coverage of the intercostal vessels by the stent graft. Uncertainties in the frozen elephant trunk procedure


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Surgery_Schwartz. is not usually associated with open arch repair. This is prob-ably due to the extensive coverage of the intercostal vessels by the stent graft. Uncertainties in the frozen elephant trunk procedure need to be addressed before it becomes a standard Brunicardi_Ch22_p0853-p0896.indd 88201/03/19 5:42 PM 883THORACIC ANEURYSMS AND AORTIC DISSECTIONCHAPTER 22Figure 22-23. Illustration of proximal aortic repair for acute ascending aortic dissection. A. This repair requires a median sternotomy and cardiopulmonary bypass. The ascending aorta is opened during hypothermic circulatory arrest, while antegrade cerebral perfusion is delivered via an axillary artery graft (shown) or via an innominate artery graft, provided that the innominate artery is not dissected (see Fig. 22-10). B. The dissecting membrane is removed to expose the true lumen. C. An open distal anastomosis prevents clamp injury of the friable arch tis-sue and allows inspection of the arch lumen. A balloon perfusion catheter in


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Surgery_Schwartz. membrane is removed to expose the true lumen. C. An open distal anastomosis prevents clamp injury of the friable arch tis-sue and allows inspection of the arch lumen. A balloon perfusion catheter in the left common carotid artery ensures bilateral antegrade cerebral perfusion. If the origin of the dissection (i.e., intimal tear or disruption) does not extensively involve the greater curvature of the aortic arch, and if there is no evidence of a preexisting arch aneurysm, a beveled, hemiarch repair is carried out, preserving most of the greater curvature of the arch. The aorta is transected, beginning at the greater curvature immediately proximal to the origin of the innominate artery and extending distally toward the lesser curvature to the level of the left subclavian artery. Consequently, most of the transverse aortic arch, except for the dorsal segment containing the brachiocephalic arteries, is removed. An appropriately sized, sealed (with collagen or gelatin) polyester tube graft