44. Kane TJ 3rd, Pollack EW. The rigid versus soft postoperative dressing controversy: a controlled

study in vascular below-knee amputees. Am Surg 1980;46:244–247.

45. Schon LC, Short KW, Soupiou O, et al. Benefits of early prosthetic management of transtibial

amputees: a prospective clinical study of a prefabricated prosthesis. Foot Ankle Int 2002;23:509–

514.

46. Malone J. Lower extremity amputation. In: Moore W, ed. Vascular Surgery: A Comprehensive Review.

Philadelphia, PA: WB Saunders; 1993:809.

47. Frang R, Taylor L, Porter J. Amputations. In: Porter J, Taylor L, eds. Basic Data Underlying Clinical

Decision Making in Vascular Surgery. St. Louis, MO: Quality Medical Publishing; 1994:153.

48. Sandnes DK, Sobel M, Flum DR. Survival after lower extremity amputation. J Am Coll Surg

2004;199:394–402.

49. Aulivola B, Hile CN, Hamdan AD, et al. Major lower extremity amputation: outcome of a modern

series. Arch Surg 2004;139:395–399.

50. Roon AJ, Moore WS, Goldstone J. Below-knee amputations: a modern approach. Am J Surg

1977;134:153–158.

51. Williams JW, Britt LG, Eades T, et al. Pulmonary embolism after amputation of the lower

extremity. Surg Gynecol Obstet 1975;140(2):246–248.

52. Yeager RA, Moneta GL, Edwards JM, et al. Deep vein thrombosis associated with lower extremity

amputation. J Vasc Surg 1995;22(5):612–615.

53. Burke B, Kumar R, Vickers V, et al. Deep vein thrombosis after lower limb amputation. Am J Phys

Med Rehabil 2000;79(2):145–149.

54. Fisher DJ Jr, Clagett GP, Fry RE, et al. One-stage versus two-stage amputation for wet gangrene of

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the lower extremity: a randomized study. J Vasc Surg 1988;8(4):428–433.

55. Enneking FK, Morey TE. Continuous postoperative infusion of a regional anesthetic after an

amputation of the lower extremity. a randomized clinical trial. J Bone Joint Surg Am

1997;79(11):1752–1753.

56. Pinzur MS, Garla PG, Pluth T, et al. Continuous postoperative infusion of a regional anesthetic after

an amputation of the lower extremity. a randomized clinical trial. J Bone Joint Surg Am

1996;78(10):1501–1505.

57. Eginton MT, Brown KR, Seabrook GR, et al. A prospective randomized evaluation of negativepressure wound dressings for diabetic foot wounds. Ann Vasc Surg 2003;17(6):645–649.

58. Armstrong DG, Lavery LA, Abu-Rumman P, et al. Outcomes of subatmospheric pressure dressing

therapy on wounds of the diabetic foot. Ostomy Wound Manage 2002;48(4):64–68.

59. Ford CN, Reinhard ER, Yeh D, et al. Interim analysis of a prospective, randomized trial of vacuumassisted closure versus the healthpoint system in the management of pressure ulcers. Ann Plast Surg

2002;49(1):55–61.

60. Iacono RP, Linford J, Sandyk R. Pain management after lower extremity amputation. Neurosurgery

1987;20(3):496–500.

61. Sherman RA, Sherman CJ, Parker L. Chronic phantom and stump pain among American veterans:

results of a survey. Pain 1984;18:83–95.

62. Snyder DC, Salameh JR, Clericuzio CP. Retrospective review of forefoot amputations at a veterans

affairs hospital and evaluation of post-amputation follow-up. Am J Surg 2006;192(5):e51–e54.

63. Cruz CP, Eidt JF, Capps C, et al. Major lower extremity amputations at a veterans affairs hospital.

Am J Surg 2003;186(5):449–454.

64. Powell TW, Burnham SJ, Johnson, G Jr. Second leg ischemia. lower extremity bypass versus

amputation in patients with contralateral lower extremity amputation. Am Surg 1984;50(11):577–

580.

65. Van Gils CC, Wheeler LA, Mellstrom M, et al. Amputation prevention by vascular surgery and

podiatry collaboration in high-risk diabetic and nondiabetic patients. the operation desert foot

experience. Diabetes Care 1999;22(55):678–683.

66. Harris WR. Lower-extremity amputation in elderly patients. Can J Surg 1987;30(5):315.

67. Stineman MG, Kwong PL, Kurichi JE, et al. The effectiveness of inpatient rehabilitation in the acute

postoperative phase of care after transtibial or transfemoral amputation: study of an integrated

health care delivery system. Arch Phys Med Rehabil 2008;89(10):1863–1872

68. Bild DE, Selby JV, Sinnock P, et al. Lower-extremity amputation in people with diabetes.

epidemiology and prevention. Diabetes Care 1989;12(1):24–31.

69. Del Aguila MA, Reiber GE, Koepsell TD. How does provider and patient awareness of high-risk

status for lower-extremity amputation influence foot-care practice? Diabetes Care 1994;17(9):1050–

1054.

70. Waters RL, Perry J, Antonelli D, et al. Energy cost of walking amputees: the influence of level of

amputation. J Bone Joint Surg Am 1976;58:42–46.

71. Malone J. Above the knee amputation and hip disarticulation. In: Ernst C, Stanley C, eds. Current

Therapy in Vascular Surgery. Philadelphia, PA: BC Decker; 1991:699.

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Chapter 95

Thoracoabdominal Aortic Aneurysms

Hazim J. Safi, Anthony L. Estrera, Charles C. Miller III, Kristofer M. Charlton-Ouw, Dianna Milewicz, and

Ali Azizzadeh

Key Points

1 Remarkable progress has been made in the surgical treatment of thoracoabdominal aortic aneurysms.

2 The decline in mortality and complication rates can be attributed to improvements in surgical

technique and perioperative care, particularly the adoption of adjunct distal aortic perfusion and

cerebrospinal fluid drainage.

3 Neurologic deficit is no longer a major threat to patients, as the use of adjuncts has lowered the

incidence for all thoracoabdominal aortic aneurysms to less than 2%.

4 Research that focuses on improving organ preservation, particularly for the most troublesome extent

II thoracoabdominal aortic aneurysms, must be continued.

1 Etheredge reported the first successful repair of a thoracoabdominal aortic aneurysm (TAAA) using a

homograft tube in 1955.1 A year later, DeBakey used a Dacron tube graft to replace the descending

thoracic aorta and infrarenal abdominal aorta.2 Subsequently, Crawford introduced what became known

as the clamp-and-go technique, encompassing three basic principles of aortic surgery: the inclusion

technique; use of a Dacron tube graft conduit; and reimplantation of visceral and renal arteries.3

Initially, the operation to repair TAAA had to be performed with haste in order to avoid extended

periods of organ ischemia. TAAA surgery has since been transformed with the use of adjuncts that

provide better organ protection and improved overall outcomes. However, sudden fatal rupture of a

TAAA remains a looming and unpredictable threat. Although emergency repair of ruptured TAAA can

save lives, the associated morbidity and mortality remain extremely high. Elective surgical repair of

TAAA is the only effective treatment for eradicating the risk of aneurysm rupture and improving patient

survival (Fig. 95-1). This chapter provides a comprehensive approach to the diagnosis and management

of TAAA as well as insight into the recent surgical results and advances in organ protection.

EPIDEMIOLOGY

Aortic aneurysm disease remains a significant cause of death in the United States. Improved imaging

techniques, increasing mean age of the population, and overall heightened awareness all contribute to

an apparent increase in the prevalence of aortic aneurysms. However, the incidence of TAAA from

population studies of the thoracic or abdominal aortic aneurysms can only be inferred. Infrarenal

abdominal aortic aneurysms occur three to seven times more frequently than thoracic aortic aneurysms.

However, fewer than 1,000 TAAAs, aneurysms involving both the thoracic and abdominal aorta, are

repaired annually, compared with approximately 50,000 infrarenal abdominal aortic aneurysms. The

estimated prevalence of abdominal aortic aneurysms varies between 2.3% and 10.7%, depending on the

population studied and the size used to define an aneurysm.4–6 The incidence of TAAAs is estimated to

be 10.4 cases per 100,000 person-years.7 The mean age of patients with a TAAA is between 59 and 69

years with a male-to-female predominance of between 2 and 4 to 1.8

Fewer than 40% of patients with untreated large TAAAs survive beyond 5 years, with most deaths

caused by rupture.3,8–10 TAAA studies have shown that rupture is more likely to occur when aneurysms

exceed 5 cm in diameter and that the rate of rupture rises with increasing aneurysm size.9,11–14 The

median size at which TAAAs rupture is around 7 cm.15,16 Aneurysms equal to or greater than 8 cm have

an 80% risk of rupture within 1 year of diagnosis.17 The lifetime probability of rupture for any

untreated aortic aneurysm is 75% to 80%, but the size at which the aneurysm will rupture and how long

it will take to reach that point cannot be easily determined. However, the average overall rate of

growth for TAAAs is 0.10 to 0.42 cm per year with an exponential growth rate for aneurysms exceeding

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5 cm in diameter.11,16,18–20

PATHOGENESIS

An aortic aneurysm is defined as a localized or diffuse dilatation that exceeds 50% of normal aortic

diameter. Most TAAAs are degenerative, with an underlying pathology similar to the more frequently

encountered infrarenal abdominal aortic aneurysm. Arteriosclerosis has long been implicated in the

development of aortic aneurysm. However, arteriosclerosis primarily affects the intima and typically

causes occlusive disease, whereas aneurysm disease usually involves the media and adventitia. Although

the pathogenesis of arteriosclerotic occlusive disease and that of aneurysm disease have been shown to

be distinct, the two conditions commonly occur together. Aneurysms associated with severe

atheromatous disease portend the potential for poor late outcomes due to chronic occlusive branch

disease and embolization. Histologically, degenerative aortic aneurysms are characterized by thinning of

the media with destruction of smooth muscle cells and elastin, infiltration of inflammatory cells, and

neovascularization.21–23 A chronic inflammatory infiltrate, comprised of macrophages, as well as T and

B lymphocytes, is consistently observed in the outer layer of aneurysm wall. The degree of vessel wall

inflammation varies and the stimulus for cell migration remains unclear. These inflammatory cells,

particularly macrophages, secrete proteases and elastase that degrade the aortic wall. In turn, elastin

degradation products may act as chemotactic agents for the influx of inflammatory cells.21 The role of

matrix metalloproteinases (MMPs), the most prominent type of elastases, in the development of aortic

aneurysms has emerged from both clinical and experimental studies. Increased elastases MMP2, MMP9,

and MMP12 have been found in aortic aneurysmal aortic tissue.21,24–26

Figure 95-1. Thoracoabdominal aortic aneurysm: comparison of survival rates in untreated patients versus surgically treated

patients.

Many TAAAs result from chronic ascending and descending aortic dissections. Familial clustering of

aortic dissections is evident because up to 20% of patients with ascending thoracic aortic aneurysms that

predispose to aortic dissections have one or more first-degree relatives with the same affliction.27–29

Marfan syndrome, characterized by skeletal, ocular, and cardiovascular abnormalities, is the most

common inherited connective tissue disorder related to aortic aneurysm and dissection. Marfan

syndrome occurs at a frequency of 1:5 to 10,000 worldwide. Aortic dilatation observed in Marfan

patients has been linked to mutations in fibrillin-1 protein, encoded by the FBN1 gene. Other known

genetic syndromes that predispose individuals to TAAA and dissection include Loeys–Dietz syndrome,

Ehlers–Danlos syndrome, Turner syndrome, and polycystic kidney disease.30–33 In addition, families

with multiple members who have thoracic aortic aneurysms and dissections have been reported in the

literature.34 In most of these families, the phenotype for TAAA and dissection is inherited in an

autosomal dominant manner with marked variability in the age at onset of aortic disease and decreased

penetrance.34 Four genes have been identified for familial thoracic aortic aneurysms and dissections that

account for 20% of this family condition. Mutations in the smooth muscle isoform of alpha-actin,

encoded by ACTA2, are responsible for 15% of familial aortic disease. Other genes responsible for less

than 2% include MYH11, TGFBR2, and TGFBR1.35–38

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A small percentage of TAAAs are the result of infection (mycotic aneurysms) or trauma

(pseudoaneurysms). An infected aneurysm frequently results from bacterial or septic emboli that seed

an atherosclerotic aorta. Another mechanism is contiguous spread from empyema or adjacent infected

lymph nodes. Although any organism can infect the aortic wall, Salmonella, Haemophilus influenza,

Staphylococcus, Mycobacterium tuberculosis, and Treponema pallidum spirochetes species are the most

common.39,40 Infected aortic aneurysms are usually saccular and thought to be at greater risk for

rupture. Chronic traumatic pseudoaneurysms of the aorta related to previously unrecognized traumatic

transection are also prone to rupture, and surgical repair is warranted at the time of diagnosis.

Approximately 25% of TAAAs are associated with chronic aortic dissection. An estimated 20% to 40%

of patients will develop aneurysms in the thoracoabdominal aorta within 2 to 5 years following acute

aortic dissection.41–43 Persistent patency of the false aortic lumen is reported to be a significant

predictor of aneurysm formation.42,44 However, the presence of chronic aortic dissection or patent false

lumen has not been linked to a higher risk of aortic rupture.45 Aneurysm disease occurs in more than

one part of the aorta in approximately 20% of cases. The so-called “mega” aorta is an “extensive” aortic

aneurysm involving the ascending, transverse arch, and the entire thoracoabdominal aorta. Although

associated factors include Marfan syndrome and chronic aortic dissection, the cause of extensive aortic

aneurysm remains unknown.

CLINICAL MANIFESTATIONS

Aortic aneurysms can cause compressive symptoms, although most do not until they reach a large size.

The most frequent complaint is ill-defined chronic back pain, although pain can also occur in the chest,

flank, or epigastrium. Acute changes in the characteristics and severity of pain can indicate sudden

expansion or impending aortic rupture. Hoarseness, resulting from vocal cord paralysis caused by

compression of the left recurrent laryngeal or vagus nerves, is frequently seen in patients with large

aneurysms of the proximal descending thoracic aorta. Patients may also experience dyspnea related to

compression of the tracheobronchial tree. A large aneurysm can exert pressure on the adjacent

esophagus or duodenum, causing dysphagia or weight loss related to obstruction or early satiety. Direct

erosion of the aneurysm into the adjacent tracheobronchial tree, esophagus, or both can cause

exsanguination, presenting as massive hemoptysis or hematemesis, respectively. Less frequently, direct

erosion can cause slow intermittent blood loss. Rarely, paraplegia or paraparesis can occur in patients

with TAAA as a result of acute occlusion of the intercostal or spinal arteries. These findings are usually

associated with acute aortic dissection, but can also result from thromboembolization. Although most

aneurysms have a varying amount of mural thrombus, distal embolization causing acute mesenteric,

renal, or lower extremity ischemia is infrequent.

Rupture is thought to be the first clinical manifestation of a TAAA in as many as 10% to 20% of

patients (Fig. 95-2). The acute onset of severe chest, abdominal, or back pain associated with

hypotension must raise the suspicion of a ruptured aneurysm. A pulsatile mass may be palpable in the

abdomen. However, if the larger part of the TAAA is positioned deep within the thoracic cage, the

aneurysm may not be apparent on physical examination. Although most ruptured aneurysms are fatal

unless treated emergently, the ruptured arterial wall may temporarily seal for several hours or days

before free rupture. In patients who are brought to the hospital alive, rupture is usually contained

within the pleura or retroperitoneum. Free rupture is accompanied by severe hypotension and patients

are more likely to die before reaching the hospital.

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Figure 95-2. Computed tomography scan of a ruptured thoracoabdominal aortic aneurysm. Note stranding in the retroperitoneum

denoting extravasation of blood.

Figure 95-3. Thoracoabdominal aortic aneurysm classification. Extent I, distal to the left subclavian artery to above the renal

arteries. Extent II, distal to the left subclavian artery to below the renal arteries. Extent III, from the sixth intercostal space to below

the renal arteries. Extent IV, the twelfth intercostal space to the iliac bifurcation (total abdominal aortic aneurysm). Extent V,

below the sixth intercostal space to just above the renal arteries.

DIAGNOSTIC IMAGING

The diagnosis of TAAA can be confirmed by various imaging modalities. Currently, computed

tomography angiography (CTA) is the imaging modality of choice in defining the extent of TAAA as per

the modified Crawford Classification (Fig. 95-3) and for planning operative strategy. The diameter of

the entire aorta, from the ascending segment to the bifurcation, can be accurately measured at various

levels on axial images assuming the centerline determination is made. The distinction between the false

and true lumens in aortic dissection can be shown on CTA. CTA can also detect thrombus or

inflammatory changes in the aortic wall. Furthermore, the presence of free (or contained) fluid or blood

can indicate free (or contained) rupture. Thin-slice CTA image acquisition can also identify patent

intercostal arteries. Coronal reformatting or three-dimensional reconstruction of axial CT images

provide additional views of TAAA (Fig. 95-4). These views are often helpful for surgical planning as

well as determining adjacent organ involvement. Intravenous iodinated contrast can be omitted in

patients with impaired renal function because it is not required for simple sizing of TAAA.

Magnetic resonance angiography (MRA) has become widely available and is frequently used as a

screening test to detect diseases of the aorta and its branches. The principal advantage of MRA over

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CTA is that MRA does not require intravenous iodinated contrast and, thus, can be performed safely in

patients with impaired renal function. In addition, MRA avoids the radiation exposure required for CT

especially when serial follow-up examinations are required. Although MRA provides better contrast

resolution, its spatial resolution is poorer than that of spiral CT. In addition, CT can better demonstrate

aortic calcification and intramural thrombus compared with MRA. The time required to acquire images,

claustrophobia, internal metallic hardware (e.g., pacemakers or orthopedic implants), and higher cost

are other limiting factors of MRA.

Figure 95-4. Somatosensory and motor evoked potentials are recorded at three sites: the popliteal fossa (A, B), C5 (C) and the

vertex (D, E).

Transesophageal echocardiography (TEE) can provide excellent imaging of the ascending and

descending thoracic aorta. TEE can be performed at the bedside or in the operating room. TEE can be

used in patients who are too unstable to be transported to the CT scanner. TEE can show aortic wall

disease, differentiating arteriosclerotic plaque from intimal tear due to dissection. In the operating

room, TEE can also be used to locate the optimal area for aortic cross-clamping and to assess cardiac

function. However, TEE is an invasive modality and requires an experienced operator for optimal

visualization and interpretation. Examination of the aorta by TEE is limited to the supradiaphragmatic

aorta because the ultrasound probe loses contact with the aorta as it crosses the gastroesophageal

junction.

Intravascular ultrasound has become an important diagnostic modality in thoracic aortic disease as it

allows very good characterization of the intraluminal relationships, especially in aortic dissection.

Although relatively invasive, requiring arterial sheath access, this is becoming an important modality

for planning endovascular therapies in aortic dissection. Epiaortic ultrasound has also been applied to

TAAA treatment. Epiaortic ultrasound can allow better characterization of the thoracic aorta for

cannulation or clamping.

PREOPERATIVE EVALUATION

The initial consultation with the TAAA patient focuses on a thorough history and physical examination,

primarily to detect comorbidities, because there are generally few symptoms or physical signs related to

the aneurysm itself. The extent of the TAAA is determined from imaging studies. Further evaluation of

associated risk factors is performed, and consultation with a cardiologist, pulmonologist, or nephrologist

is often necessary to aid in the stratification of risks.

Ischemic heart disease is prevalent in this population and is the most common cause of death in

patients with a TAAA. TEE provides an excellent estimate of cardiac function. Coronary artery

revascularization for critically stenosed coronary artery disease, using either percutaneous intervention

(balloon angioplasty or stent) or surgical bypass, may be indicated prior to TAAA surgery, but the risk

of rupture of the aneurysm must be weighed against the risk of coronary intervention and the delay

caused by intervention. For patients who must undergo coronary artery bypass prior to TAAA repair,

the conduit of choice is the saphenous vein graft. Use of the left internal mammary artery is avoided to

prevent potential cardiac ischemia if aortic cross-clamping proximal to the left subclavian artery is

required during the TAAA repair. Moreover, the internal mammary artery may be an important

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