Chronic thoracic and thoracoabdominal aortic disease

Definition

Aneurysm, traditionally defined as a permanent localized dilation of the aorta that is at least 50% greater than its normal diameter, is the most common condition of the thoracic aorta that necessitates treatment. In contemporary aortic repair, treatment involves open surgery to replace the aorta with a synthetic graft (or less commonly, a tissue-based graft such as an allograft or homograft); endovascular therapy in which a stent-graft is placed within the aorta; or a combination of both approaches (i.e., hybrid repair). In the absence of symptoms, repair is commonly performed at a diameter-based threshold. This chapter describes treatment for chronic thoracic aortic disease, specifically repair of the ascending thoracic aorta, the aortic arch, the descending thoracic aorta, and the thoracoabdominal aorta. Other aortic topics are covered elsewhere in this book, such as aortic root disease ( Chapter 12 ), acute traumatic aortic transection ( Chapter 24 ), postoperative paraplegia ( Chapter 24 ), and acute aortic dissection ( Chapter 22 ).

Historical note

An important contribution to modern aneurysm surgery was made by Matas in New Orleans in 1902 when he described the basic maneuver of “getting inside the aneurysm” with minimal external dissection and after obtaining control of the artery above and below the aneurysm; the procedure itself relied on primary closure (arteriorrhaphy) of the arterial wall. Interestingly, this basic maneuver was ignored as aortic aneurysm surgery began to develop.

Throughout the first half of the 20th century, sporadic attempts were made to treat aortic aneurysms, almost all in the abdominal aorta. Treatment was by proximal partial or complete ligation of the aorta, wrapping with various materials, and insertion of intraluminal wire to stimulate thrombosis. Results were generally unsatisfactory. Various other palliative procedures had also been used unsuccessfully. In 1950, Estes at the Mayo Clinic published a classic paper that demonstrated the poor prognosis of patients with abdominal aortic aneurysms, only 50% of whom survived 3 years after diagnosis, with two-thirds of the deaths attributable to aneurysmal rupture. In response to that study, the Mayo Clinic began a surgical approach to this condition in 1951 and, in 1953, reported the results of aneurysm reinforcement and the tedious operation of aortoplasty and complete wrapping with fascia lata.

Meanwhile, an exploration into the repair of aortic coarctation sought to better understand the limits of clamping the aorta and suspending its circulation. In 1944, Alexander and Byron successfully resected a thoracic aortic aneurysm secondary to coarctation, although without restoration of aortic continuity. This same year, Crafoord resected an aortic coarctation and restored continuity with end-to-end suture, surmising that aortic clamping could be tolerated for as much as 20 to 25 minutes based on his experimental work. Because of the limitations of aortic resection without replacement, aortic substitutes were soon developed in the form of cadaver-based donor tissue; aortic allografts were developed in 1948 by Gross and colleagues in Boston to replace the resected aortic segments. On May 24, 1948, they resected a coarctation in a 7-year-old boy, restoring aortic continuity with an aortic allograft. When the clamps were released, the distal vasculature dilated, and the patient became hypotensive and died. This led to a recommendation to slowly release the clamps following repair of aortic coarctation. ^, They performed four more allograft replacements of the aorta for coarctation in 1948, five in 1949, and eight in 1950, including the first frozen and irradiated graft, which functioned for at least 30 years (Dr. Robert Replogle, personal communication, July 19, 2002). In 1950, Swan and colleagues also reported successful clinical use of allografts for treating complex coarctations, including those with aneurysms. Aortic allograft banks were subsequently established in some centers to provide aortic replacement grafts. ^,

Adopting techniques from coarctation repair within the descending thoracic aorta, Lam and Aram in 1951 reported resection and allograft replacement of a descending thoracic aortic aneurysm in an adult. Paraparesis developed in their patient, and the patient died 6 weeks after operation of empyema. About this time, Bahnson reported successful management of a saccular aneurysm of the descending thoracic aorta by lateral resection and aortorrhaphy. In 1953, DeBakey and Cooley reported the first successful application of resection and allograft replacement of a 20-cm descending thoracic aortic aneurysm (and Cooley later argued this repair was, in fact, an extent I thoracoabdominal aortic repair). ^,

Regarding the abdominal aorta, in 1952, Schafer and Hardin in Kansas City reported resection and allograft replacement of an abdominal aortic aneurysm, only to have the patient die of numerous complications 28 days after operation. In that same year, Dubost and colleagues, working in Paris, reported the first successful case of aortic resection for degenerative aneurysm with restoration of blood vessel continuity using a preserved aortic allograft (in their case, an abdominal aortic aneurysm that was approached retroperitoneally). In 1953, reports of similar successes came from DeBakey and Cooley in Houston and from the Mayo Clinic. ^, ^,

In much of the early work with abdominal aortic aneurysms performed at the Mayo Clinic and elsewhere, the aneurysm was meticulously dissected away from surrounding tissues, often with a long and difficult operation and considerable hemorrhage from lumbar arteries. DeBakey and Cooley described this tedious method in their classic paper of 1953 and reported the survival of six out of seven patients, all of whom underwent allograft replacement. Although Javid and colleagues in 1962 and Creech in 1966 are generally credited with reintroducing Matas’s technique of working within the aneurysm so as to avoid separating the aneurysm from surrounding tissues and related complications, the provenance of how this technique was popularized is unclear. ^, DeBakey (who had himself trained under Matas and brought Creech to Houston in 1949) and colleagues in Houston had reintroduced this concept into abdominal aortic aneurysm surgery by as early as 1958. Crawford’s inclusion technique of sewing the graft from within the aneurysm embodies this concept.

Ascending aortic aneurysms were also approached surgically before the advent of cardiopulmonary bypass (CPB). In 1952, Cooley and DeBakey reported the removal of six sacciform ascending aortic and aortic arch aneurysms after lateral clamping and resection followed by direct suture (aortorrhaphy), as did Bahnson, and Johnston and colleagues in 1953. ^, ^, In 1956, Cooley and DeBakey reported the first successful modern operation for ascending aortic aneurysm, consisting of resecting the ascending aorta and replacing it with an aortic allograft. To provide CPB during repair, they employed a modified DeWall-Lillehei pump oxygenator and provided unilateral antegrade cerebral perfusion (ACP) via the right common carotid artery. Later, once prosthetic aortic valves were available, Wheat and colleagues then reported successful simultaneous but separate replacement of the aortic valve and the entire ascending aorta (from the aortic anulus to the innominate artery), reimplanting the coronary ostia onto the replacement graft; they used a Teflon graft and a Starr-Edwards valve in this patient with a luetic aneurysm and aortic valve insufficiency, reporting their efforts in 1964. Bentall and De Bono in 1968 and Edwards and Kerr in 1970 reported complete aortic root replacement using a composite valve and polyester tube graft. ^, Wheat and colleagues subsequently demonstrated long-term patency of their anastomoses between grafts and coronary ostia.

Aneurysms enveloping the full arch of the aorta presented a more difficult surgical challenge, largely because of the need to address branching brachiocephalic arteries during repair. In 1954, DeBakey and Cooley reported the successful resection of a distal aortic arch aneurysm that had resulted from acute traumatic aortic transection, replacing it with an allograft. The case is of interest in that the patient’s temperature was reduced to 28°C by surface cooling before thoracotomy. The aorta was clamped proximal to the left subclavian artery (which was also individually clamped) for 1 hour, and paraplegia did not develop (see “ Paraplegia ” under “Special Features of Postoperative Care” in Chapter 24 for the significance of this finding). In 1955, Cooley and colleagues reported unsuccessful resection of an aneurysm of the entire aortic arch without CPB, and instead using a cumbersome method of temporary shunts to each of the three brachiocephalic arteries, similar to Stranahan and colleagues in a 15-hour operation in 1955 and a second attempt from Houston with Creech and colleagues in 1956. In 1957, DeBakey and colleagues reported the first successful repair of an aortic arch aneurysm with allograft replacement using the same modified DeWall-Lillehei pump oxygenator as they did in their ascending aortic replacement repair, although this time, they provided bilateral ACP via the innominate and left common carotid arteries. Thoracoabdominal aneurysms also presented difficult surgical challenges, not only because of the magnitude of the operation and having to incorporate the branching visceral arteries but also because of the propensity of patients to develop renal and spinal cord dysfunction after repair. ^, Early attempts included Bahnson’s successful repair of a saccular thoracoabdominal aneurysm by lateral resection and aortorrhaphy in 1952. Ellis and colleagues at the Mayo Clinic first reported repair of an abdominal aneurysm involving a visceral artery (in their case, the right renal artery) by resection and allograft replacement in 1955. Etheredge and colleagues reported successful repair of a more complex thoracoabdominal aneurysm, including the celiac axis and superior mesenteric artery in the same year. He used a proximal to distal shunt, replaced the aortic aneurysm with an allograft, reattached the celiac and mesenteric arteries, and sacrificed the left kidney in a 37-year-old patient who lived another 20 years. This same year in London, Rob reported his work in detailing aortic replacement in 33 aortic aneurysms, of which 6 involved the thoracoabdominal aorta. In 1956, DeBakey and colleagues reported successful repair of such an aneurysm involving all the visceral arteries (celiac, superior mesenteric, and both renal arteries) and replacement with an allograft in a series of four thoracoabdominal aortic aneurysm (TAAA) repairs. Subsequently, once synthetic grafts (Dacron in particular) gained preference as an aortic substitute over allografts, DeBakey and his team devised the technique of using the synthetic graft as permanent aortic bypass going around the aneurysm and using individual branched grafts to bridge the distance and reattach the visceral arteries, and in 1965 they reported 26% mortality among 42 patients. As mentioned earlier, Crawford and colleagues modified and simplified the operation by applying the inclusion technique with in situ construction, reducing hospital mortality to 8% by 1978. ^, However, the extraanatomic approach remained in use by DeBakey and others for many years afterward.

During this developmental phase, there was controversy about the lethality of thoracic aortic aneurysms. Some reports indicated that patients with thoracic aneurysms fared better than those with abdominal aneurysms. In 1964, Joyce and colleagues established that this was not the case.

Over subsequent decades, a series of technical improvements evolved into many of the techniques currently used for surgical treatment of aortic arch aneurysms. Even after successful repair of aneurysms of the arch had been accomplished using CPB, methods remained complex, often involving separate cannulation of the brachiocephalic arteries. In 1964, Borst and colleagues reported repair of a traumatic aneurysm of the distal portion of the aortic arch through a left thoracotomy, using CPB to produce deep hypothermia (20°C) and performing a direct-suture-based repair during an interval of circulatory arrest. Another technical improvement was the use of a single anastomosis (an “island” approach) between an oval opening in the graft and the aortic wall around all three brachiocephalic arteries in replacing aortic arch aneurysms, reported by Bloodwell, Cooley, and colleagues in 1968 and by Pearce and colleagues the following year. ^, In 1975, Griepp and colleagues established the value of profoundly hypothermic circulatory arrest (HCA) for resecting and grafting of more proximal and more extensive aneurysms of the aortic arch; in their report of repair in four patients, the lowest temperature ranged from 12°C to 18°C. In 1978, Ott, Cooley, and colleagues reported tailoring a more limited arch resection so that a single distal anastomosis could be made, replacing only the lesser curvature of the arch with graft (i.e., a “hemiarch” approach). In 1981, Crawford and Saleh applied the inclusion technique to arch aneurysms, working entirely within the aneurysm and wrapping the graft with an aneurysm wall. Additionally, in the last several decades, further modifications include the use of trifurcated grafts to debranch the brachiocephalic arteries, the widespread adoption of ACP, and the development of elephant trunk (ET) and frozen ET approaches to extend repair from the arch to the descending thoracic aorta. ^,

Although more completely detailed in Chapter 24 , a brief note of the technical improvements that have also been made in aortic replacement graft material is warranted. As discussed earlier, Dubost and others in the early surgical period (1950s) used preserved aortic allografts to replace aortic segments. ^, ^, ^, ^, Difficulty in procurement (which relied on a deceased donor) and concerns of durability soon revived the search for synthetic aortic substitutes despite the unsuccessful pioneering efforts of Carrel and others. The first satisfactory synthetic aortic substitute was a fabric tube made of polyvinyl chloride cloth, and the first clinical application of this device was reported by Blakemore and Voorhees in New York City in 1954. Shumacker and King in Indianapolis also used these fabric tubes for aortic replacement in the same year. For the next several years, surgeons autoclaved and used fabric grafts made on the sewing machines of wives and friends, with generally good results. Several groups quickly undertook intensive study of prosthetic grafts, and in 1955, Deterling and Bhonslay reported that polyester was the best material then available for aortic replacement. Knitted and woven grafts of various types, mostly polyester, have been widely used since then. Early synthetic grafts typically had substantial porosity, and bleeding could be difficult to control. Subsequent development of polyester grafts impregnated with collagen, gelatin, or albumin has resulted in a substantial reduction in blood loss through the grafts (particularly in fully heparinized patients such as those on full CPB), a major cause of postoperative morbidity.

In time, alternative approaches to aortic replacement would emerge that relied on the endovascular deployment of a stent-graft (namely a large-diameter metal stent covered in fabric) that would overlay the aorta and largely rely on radial pressure to incorporate into the aortic wall. Stent-grafting of descending thoracic aortic aneurysms was introduced by Volodos and popularized by Dake and colleagues at Stanford University in the early 1990s using custom-designed grafts. Since then, a number of commercially developed grafts have become available for clinical use and revolutionized many aspects of aortic repair.

Morphology and morphogenesis

Anatomy

The most basic classification of the aorta divides it along the diaphragmatic hiatus into the thoracic and abdominal aorta. The thoracic aorta includes the ascending thoracic aorta, the aortic arch, and the descending thoracic aorta; the thoracoabdominal aorta describes the descending thoracic aorta combined with the abdominal aorta ( Fig. 23.1 ). Contemporary classification has evolved to include a more comprehensive system based on key anatomic features, dividing the aorta into 11 zones. ^, ^, The aorta is known for its strength and flexibility; these are conferred by collagen and elastic fibers, respectively. The aortic wall is composed of three layers—the intima, media, and tunica adventitia. The innermost layer, the intima, contains a single layer of endothelial cells supported by a small amount of connective tissue. The internal elastic membrane is located adjacent to the intima and is formed by a layer of elastic fibers arranged in a circular pattern. The media is the thickest layer of the aorta wall, containing many alternating layers of lamellar units. These lamellar units are composed of layers of smooth muscle cells arranged in multiple concentric and longitudinal layers interspersed between sheets of elastin and collagen bundles. These elements are embedded within an extracellular matrix containing adhesive proteins, proteoglycans, and other factors. The external elastic membrane separates the media from the adventitia and is composed of a layer of elastic fibers arranged in a longitudinal pattern. The outer layer, the tunica adventitia, comprises a thin layer of connective tissues, fibroblasts, nerves, the vasa vasorum, and other factors within a supporting extracellular matrix containing collagen and elastin. The vasa vasorum provides a blood supply to the outer aortic wall. ^,

An illustration of the aorta with labeled thoracic, abdominal, and iliac segments and their major branches. The illustration presents the full length of the aorta with labels identifying the major regions and branches. At the top, the innominate artery lies on the right side of the arch, the left common carotid artery lies in the center, and the left subclavian artery lies on the left. These vessels arise from the transverse arch, which connects to the ascending aorta. Below this level, the sinotubular junction and the sinuses of Valsalva are located. The proximal descending thoracic aorta runs beneath the left subclavian artery, followed by the mid descending thoracic aorta and the lower descending thoracic aorta. The thoracoabdominal region continues downward into the pararenal abdominal aorta. Lower in the diagram, the suprarenal abdominal aorta lies above the right renal artery on the right side, and the left renal artery on the left, and the infrarenal abdominal aorta lies below these renal branches. Near the lower end, the right common iliac artery branches to the right and the left common iliac artery branches to the left, and each divides into an external iliac artery and an internal iliac artery. At the lowest portion, the right common femoral artery continues from the right external iliac artery, and the left common femoral artery continues from the left external iliac artery. On the left side of the illustration, a side view of a human silhouette is included, with the path of the aorta traced along the midline from the upper chest to the lower abdomen. — • Figure 23.1

Classification

Chronic diseases of the thoracic aorta that are amenable to surgical treatment are listed in Box 23.1 .

• BOX 23.1

Aortic Disease Amenable to Surgical Treatment

Sporadic (medial) degeneration
Chronic aortic dissection
- Intramural hematoma
- Penetrating aortic ulcer
Heritable thoracic aortic disease
- Syndromic
- Marfan syndrome
- Loeys-Dietz syndrome
- Vascular Ehlers-Danlos syndrome
- Other syndromes
- Nonsyndromic disorders
- Congenital disorders
Aortitis
Infection
Trauma
Pseudoaneurysm and other late complications
Diffuse arteriosclerotic disease

Aneurysm.

The category of risk factors and causes of thoracic or TAAA include nonspecific (spontaneous) medial degeneration, aortic dissection (including variants), heritable conditions (syndromic and non-syndromic), inflammation, infection, trauma, congenital conditions, and other factors. Additionally, aortic composition differs by segment and age, with the ascending aorta being more flexible than the abdominal aorta and older patients having a less elastic aorta that becomes stiffer, which can contribute to aortic dilation. ^, ^,

Sporadic (medial) degeneration.

Thoracic aneurysms without clear evidence of heritable causation are considered sporadic and degenerative; however, although such aneurysms are not linked to established genetic mutations, emerging evidence suggests the possibility of genetic predisposition. Degenerative aneurysms are the most frequently occurring aortic aneurysms, with the abdominal aorta being the most commonly affected segment. The etiology of degenerative aneurysms is imperfectly understood and thought to form from a combination of factors, including the aging process; oxidative and biomechanical stress; structural degradation of the aortic intima; inflammation or autoimmune responses; factors specific to the function of smooth muscle cells (e.g., phenotypic switching, senescence, or death); and other causes. ^, ^, The aortic wall’s media and adventitia are particularly vulnerable to inflammation, which can trigger smooth muscle cell destruction and subsequently reduce elastin within the extracellular matrix, resulting in a loss of flexibility. ^, Degeneration occurs as the lamellar units within the weakened media accumulate proteoglycans, which are later replaced by myxoid material (i.e., mucoid extracellular matrix accumulation). ^, Although atheromatous changes are frequently present in and around degenerative aneurysms, the causative role of arteriosclerosis in their development is not clearly established, although emerging evidence suggests plaque-induced remodeling of the extracellular matrix. Efforts to systematically quantify and describe medial degeneration typically rely on mucoid accumulation, specific changes to elastic fibers, medial fibrosis, smooth muscle cell disorganization, and nuclei loss.

Aortic dissection.

Morphologic features of acute aortic dissection, including classification and the acuity of repair, are discussed in Chapter 22 . Briefly, during an acute dissection event, the inflow of blood through the entry tear and into the media creates an inner and outer channel of blood; the weakened outer wall, consisting of the outer layer of the media and the adventitia, separates from the intimal layer. Surviving patients generally enter the chronic phase of dissection 30 to 90 days after onset, ^, ^, and a residual, untreated portion of the native aorta often remains, which tends to progressively enlarge. In untreated aortic segments, the false lumen is typically patent and has persistent blood flow, although it may be partly thrombosed. Aneurysms related to chronic aortic dissection and its variants (intramural hematoma [IMH] and penetrating aortic ulcer [PAU], presented later) may be saccular or fusiform in shape. Survivors of DeBakey type I aortic dissection often need subsequent repair of the aortic arch. Survivors of DeBakey type I and III aortic dissection typically undergo repair of the descending thoracic or thoracoabdominal aorta to treat progressive aortic expansion. Unlike the acute phase of aortic dissection, in which the urgency of repair is dictated by location, repair in chronic dissection is typically dictated by the presence of symptoms, high-risk features, or aortic expansion beyond a guideline-driven threshold of repair.

Intramural hematoma.

IMH ( Fig. 23.2 ) is an imperfectly understood condition in which blood collects within the medial layer in the absence of a visible intimal tear or patent false lumen. Imaging studies reveal a distinct crescent-shaped thickening of the outer aortic layer >5 mm. The rupture of an arteriosclerotic plaque and spontaneous rupture of vasa vasorum have been postulated as mechanisms for the development of the hematoma. Alternative theories speculate IMH results from small intimal tears that are not readily visualized and are an intermediate stage to classic dissection.

Penetrating aortic ulcer.

Arteriosclerotic lesions involving the intimal layer of the aorta may ulcerate and penetrate the internal elastic lamina of the aortic wall. They can result in separation of the layers of the media and form localized areas of pooled blood. Penetrating arteriosclerotic ulcers occur most commonly in the descending thoracic aorta, although they may occur in the ascending aorta or aortic arch, where they are generally considered more harmful. Most commonly, PAUs are isolated, discrete lesions that are saccular in shape ( Fig. 23.3 ). However, they may progress to include IMH, classic aortic dissection, rupture, and combinations thereof—the process of which remains incompletely understood. PAUs tend to occur in elderly patients with heavy atherosclerotic burden, and embolization can occur. Small ulcers (<10 mm in diameter or depth) that are isolated, asymptomatic, and located in the distal aorta are commonly repaired in the chronic phase after conservative management. ^,

Heritable thoracic aortic disease.

Whereas abdominal aortic aneurysms are primarily attributed to the aging process, thoracic aortic aneurysms often have heritable implications. ^, ^, Within the thoracic aorta, aneurysms of the ascending thoracic aorta are more likely to have a heritable cause than those of the descending thoracic aorta. ^, Thus far, 11 genes have been determined to cause heritable thoracic aortic disease (HTAD), which forms the basis of contemporary genetic testing panels. ^, Roughly 20% to 30% of thoracic aneurysms result from HTAD, which is categorized as syndromic or nonsyndromic. ^, Syndromic HTAD signifies multisystemic features affecting other organs, whereas nonsyndromic HTAD designates disease limited to the aorta and its branching arteries. Frequently, only a single gene is mutated, which can manifest as syndromic or nonsyndromic disease. Although sporadic degenerative aortic disease commonly develops in older patients (i.e., age 60 and older), HTAD typically presents in younger patients (i.e., age 50 and younger).

Marfan syndrome.

Marfan syndrome is an autosomal dominant disorder resulting from numerous mutations in the FNB1 gene that lead to defective synthesis of the glycoprotein fibrillin (a major component of the extracellular matrix within the medial layer of the aorta). There is systemic disruption of connective tissues, including the eye (e.g., dislocation of the ocular lens); skeleton (e.g., overgrowth of the long bones with a tall and skinny stature); and the aorta (e.g., a predisposition to aortic aneurysm, dissection, and rupture). Patients with Marfan syndrome are known for a distinctly dilated aortic root but can experience aneurysms in other aortic segments, especially if aortic dissection is present. ^, ^, Most patients will have a family history, but roughly 25% of mutations are de novo. Marfan syndrome can be difficult to diagnose and does not strictly depend on genetic findings; the Ghent criteria are used to aid diagnosis.

Loeys-dietz syndrome.

Loeys-Dietz syndrome (LDS) is an autosomal dominant aortic aneurysm disorder and results from mutations in either in transforming growth factor or these receptors ( TGFBR1, TGFBR2, TGFB2, TGFB3 ) or cellular transmission ( SMAD3 ). ^, Clinical features include a bifid uvula or cleft palate; widely set eyes (i.e., hypertelorism); foot deformities; widespread systemic arterial tortuosity; and aggressive aortic disease that presents at a younger age as compared to Marfan syndrome. ^, The majority of patients have aortic root aneurysms that result in aortic dissection, which can occur even in those with normal aortic dimensions. Thus, patients with LDS and their families need careful monitoring and should seek treatment if experiencing chest pain.

Vascular Ehlers-Danlos syndrome.

Ehlers-Danlos syndrome comprises a group of heterogeneous conditions characterized by various defects in the synthesis of type III collagen; for most forms of Ehlers-Danlos, the development of aneurysms is uncommon. However, vascular Ehlers-Danlos syndrome (VEDS; formerly categorized as type 4 EDS), resulting from a mutation in the collagen gene ( COL3A1 ), manifests in systemic and aggressive vascular disease at a young age. Spontaneous rupture or dissection of the aorta or other arteries can occur at normal aortic diameters. ^, ^, Syndromic features include a unique facial structure (e.g., thin nose, small earlobes, and prominent eyes); translucent skin; and easy bruising. Tissue fragility, bleeding complications, and poor healing can complicate surgical treatment.

Other syndromes.

Other syndromes (and the related gene) associated with aneurysm development and aortic dissection include Shprintzen-Goldberg syndrome ( SKI ), Meester-Loeys syndrome ( BGN ), arterial tortuosity syndrome ( SLC2A10 ), smooth muscle dysfunction syndrome ( ACTA2 ), and other syndromes, even when no clear family history is present. ^, ^,

Nonsyndromic disorders.

Nonsyndromic thoracic aortic disease is limited to the aorta and branching arteries—and as mentioned earlier, other organ systems are not involved. In general, such disease is more common, easier to manage than syndromic conditions, and may be nonfamilial or familial (i.e., present in one or more family members). ^, ^, Familial thoracic aortic aneurysm tends to be inherited in an autosomal dominant manner. Several genes have been identified as causes of familial thoracic aortic aneurysms (e.g., ACTA2, MYH11, MYLK, PRKG1 , and others). ^, ^, A thorough family history should be obtained because of the relatively high prevalence in both first- and second-degree relatives.

Congenital conditions.

Congenital conditions associated with aortopathy include bicuspid aortic valve, Turner syndrome, and other complex congenital heart defects; aortic coarctation may also be identified in these patients. There are several genes associated with bicuspid aortic valve ( NOTCH1, TGFBR2, MAT2A, GATA5, SMAD6, LOX, ROBO4, TBX20 ). Aortic valve stenosis (related to the valve not fully opening) and altered blood flow mechanics (as seen in 4D imaging) are present in patients with a bicuspid aortic valve, but patients may also have aortic valve regurgitation. ^, Bicuspid aortopathy refers to both the pathological destruction of the aortic wall (i.e., medial degeneration) related to both cellular mechanisms and wall shear stress from altered blood flow and the phenotypic expression of this disease process. Phenotypic patterns are thought to be related to cusp fusion patterns, with distinct patterns and extent of aortic disease. There are three basic aneurysm shapes of bicuspid aortopathy, which are based on the extent and location of disease: (1) ascending phenotype, (2) root phenotype, and (3) extensive phenotype, including aortic coarctation. The ascending phenotype (related to a right-noncoronary cusp fusion) is most common, followed by the root phenotype (related to a right-left cusp fusion), and the extensive phenotype being uncommon. ^, ^,

Risk factors for aortic dissection in patients with bicuspid aortopathy are incompletely understood. Aortic diameter may not be the best predictor of aortic dissection; the root phenotype, aortic valve regurgitation, uncontrolled hypertension, genetics, and rapid aortic dilation may play a role in determining risk. ^, ^,

Turner syndrome is caused by an X chromosome mutation ( XO, Xp ) and thus affects only women; signs include short stature, late puberty, learning disabilities, and infertility. Cardiovascular disease is present in roughly half of all women with Turner syndrome. When a bicuspid aortic valve or aortic coarctation is additionally present, the aortic growth rate appears elevated, increasing the risk for aortic aneurysm and dissection.

Aortic coarctation typically presents as a narrowing of a short section of the descending thoracic aorta just distal to the left subclavian artery. The quality of aortic tissue in this section is generally poor. In rare cases, the location and extent of coarctation differ; this includes an interrupted or hypoplastic aortic arch or a long-segment aortic coarctation (i.e., middle aortic syndrome). Typical aortic coarctation is often corrected in childhood, and late complications such as an aneurysm, pseudoaneurysm, or restenosis may develop. ^,

Aortitis.

Patients with chronic granulomatous inflammatory changes may develop aneurysms of the thoracic aorta that require surgical treatment. ^, ^, Aortitis most commonly results from Takayasu arteritis or giant cell arteritis, although a variety of inflammatory disorders, such as Behçet disease, ankylosing spondylitis, psoriatic arthritis, polyarteritis nodosa, and Reiter syndrome, may result in dilation of the aortic root and aortic valve regurgitation that require surgical intervention. Aortitis may be widespread or limited to an isolated portion of the aorta; it is diagnosed from preoperative imaging studies (e.g., diffuse thickening); serum biomarkers; or histopathologic findings in aortic tissue samples. Notably, giant cell arteritis can mimic IMH. ^,

Infection.

Primary infection of the native thoracic aorta is rare; this infectious aortitis may be aneurysmal (i.e., mycotic aneurysm) or nonaneurysmal. Causes include direct deposition of circulating bacteria from septic emboli and other sources onto traumatized aortic intima or diseased segments of arteriosclerotic or aneurysmal aorta. Infection of nearby structures may spread to the aorta, and infection of intraluminal clot in a preexisting degenerative aneurysm may occur after an episode of bacteremia or other infectious process. ^, ^, Other risk factors for development of infected aneurysm include congenital cardiac or vascular defects, trauma, and impaired immunity. Infectious aortitis is difficult to diagnose, and the causative organism may remain undetermined. Common causative organisms include Staphylococcus aureus, Staphylococcus epidermidis, Salmonella , and Streptococcus species. ^, ^, ^, However, any number of organisms could cause aortic disease. Infected aneurysms may be saccular or fusiform in shape and are occasionally multifocal. Infectious aortitis is unpredictable, and infected saccular aneurysms may expand quickly and rupture at relatively small aortic diameters; once ruptured, catastrophic consequences for the patient are not uncommon. ^,

Trauma.

Aneurysms resulting from blunt trauma most frequently involve the proximal descending thoracic aorta and may present many years after the acute injury. When neither death nor operation follows the acute transection, disruption (from partial thickness tears) of at least part of the aortic circumference, usually at the level of the ligamentum arteriosum, results in extravasation of blood into the periaortic tissues. A pseudoaneurysm may form with continued blood flow contained by aortic adventitia or the mediastinal tissues. Over time, the pseudoaneurysm may enlarge and rupture from increased wall stress (Laplace law). Chronic posttraumatic aneurysms represent a small percentage of patients with aneurysms of the thoracic aorta. Common sites of injury include the aortic isthmus, proximal to the innominate artery, distal to the left subclavian artery, and at the ligamentum arteriosum. ^,

Pseudoaneurysm and other late complications.

Pseudoaneurysms are most commonly associated with trauma, infection, invasive procedures, and previous operations on the aorta and may present years after the initial insult to tissue. In patients with prior open repair, pseudoaneurysms can develop at the site of aorta-to-aorta or aorta-to-graft anastomoses, generally as a result of tension or infection (which can lead to anastomotic dehiscence). In patients with a prior arch or thoracoabdominal aortic repair, the use of an island reattachment strategy infrequently results in a patch aneurysm, especially in patients with heritable disease. Fistulas may form after prior open or endovascular aortic repair, with an added risk of infection. Persistent endoleak after endovascular repair may result in rapid aortic expansion and aneurysm formation. Graft or stent-graft infection is a rare complication that is difficult to diagnose and, if suspected, typically necessitates reoperation to remove the infected materials. ^,

Diffuse arteriosclerotic disease.

Atherosclerosis, a chronic inflammatory disease linked to elevated lipids, is commonly identified in patients with thoracic aortic aneurysms. It is typically graded from normal (Grade I) to most severe (Grade V), which indicates the presence of mobile atheroma. When severe disease is detected in patients who are undergoing operations on the heart or ascending aorta, it is vital to identify the presence of arteriosclerotic plaques with a thickness of more than 4 mm because this is an important predictor of brain infarction because such plaques are also a source of embolization to other organs; in such cases, graft replacement or endarterectomy of the involved segment of the arch should be considered. ^, Furthermore, late-stage severe arteriosclerosis of the aorta (i.e., porcelain aorta) adds substantial risk to thoracic aortic repair. Cannulating, clamping, and manipulating wire (especially near branching arteries) in the aorta are important risk factors for stroke, especially when sessile, mobile, or pedunculated atheroma are present ( Fig. 23.4 ).

A pair of panels from an epiaortic ultrasound and a resected aortic section present a circular lumen with an arrow and an arrowhead marking abnormal areas. The pair of panels shows an epiaortic ultrasound in a transverse section showing a circular lumen with an arrow pointing to an irregular inward surface and an arrowhead pointing to a dense area along the wall, and the corresponding resected aortic section showing the same lumen with an arrow indicating an uneven interior surface and an arrowhead indicating a firm wall region. — • Figure 23.4

Additionally, patients with such disease who do not undergo cardiac or thoracic surgical procedures remain at risk for embolic stroke and embolization to the abdominal organs and lower extremities. ^, ^, Strategies to reduce the risk of embolic stroke in patients with severe atherosclerosis include cannulating in disease-free parts of the ascending aorta, the use of lower flow rates, and performing repair under HCA. ^, ^, Occasionally, the presence of pedunculated mobile atheroma in patients who have had a transient ischemic attack or stroke is an indication for operation.

Prevalence

The prevalence of thoracic and TAAAs is difficult to determine because it is often a silent disease that is incidentally discovered. In the past, the prevalence was estimated using autopsy studies, whereas contemporary studies may include noninvasive surveillance studies (e.g., imaging studies) or population-based, hospital and administrative data. A meta-analysis of 22 studies determined a pooled incidence of thoracic aortic aneurysm of 5.3 per 100,000 persons/year and with a prevalence of 0.16%. However, when autopsy studies (n=3) were removed, the prevalence of thoracic aortic aneurysm dropped to 0.07%. Notably, thoracic aortic aneurysm is more common in men than in women, and its incidence appears to be increasing in contemporary eras. ^, ^, Olsson and colleagues reported incidence as 16.3 per 100,000 persons/year for men and 9.1 per 100,000 persons/year for women in Sweden. Lodewyks and colleagues reported incidence increased from 16.8 per 100,000 persons/year to 24.4 per 100,000 persons/year from 1998 to 2016 in Manitoba, Canada.

Certain sets of patients, such as those with abdominal aortic dilation (i.e., 25% larger) or aneurysm, intracranial aneurysm, heart disease, or relatives with nonsyndromic aortic disease tend to have higher rates of thoracic aortic aneurysm than those from general population studies. For example, a large Danish, population-based study found abdominal aortic dilation to be highly predictive of concomitant thoracic aortic disease, and in a small hospital-based study, 18.3% of survivors of abdominal aortic repair were identified with thoracic aortic disease.

Location

The true anatomic distribution of thoracic aortic aneurysms is not known with certainty, but the aortic arch and thoracoabdominal regions are less likely to be aneurysmal as compared to the ascending aorta and descending thoracic aorta. ^, ^, In 72 individuals with aneurysms, Bickerstaff and colleagues found that 37 (51%) involved the ascending aorta, 8 (11%) the aortic arch, and 27 (38%) the descending thoracic aorta. Thoracoabdominal aneurysms comprise 5% to 10% of asymptomatic thoracic aneurysms. ^,

Clinical features and diagnostic criteria

Symptoms

Many patients with thoracic aortic aneurysms are asymptomatic at presentation, and the aneurysms are detected during testing for other disorders. Symptoms relating to the aneurysm usually develop later in the course of aortic enlargement and result from an impingement of the aneurysm on adjacent structures. Aneurysms involving the aortic root (see Chapter 12 ) or ascending aorta are frequently associated with symptoms related to aortic valve regurgitation that develops as a result of progressive aortic enlargement near the aortic valve anulus. Patients with aneurysms of the aortic arch may present with pain in the neck and jaw. Hoarseness results from stretching of the left recurrent laryngeal nerve, stridor from compression of the trachea, dysphagia from impingement on the lumen of the esophagus, dyspnea from compression of the lung parenchyma, and plethora and edema from compression of the superior vena cava. Patients with aneurysms of the descending thoracic aorta may report pain in the interscapular area or left-sided pleuritic pain. Aneurysms of the thoracoabdominal aorta may be associated with back pain, abdominal pain, and pain in the left shoulder resulting from irritation of the left hemidiaphragm.

Acute onset of severe tearing pain in the anterior part of the chest or neck or between the shoulders is the typical presenting symptom of acute aortic dissection (see Chapter 22 ); acute chest pain may also result from variants of classic dissection, such as IMH or penetrating arteriosclerotic ulcer (e.g., from erosion into the surrounding tissues). Aortic rupture or sudden expansion in a patient with chronic aortic dissection may also present as severe chest or neck pain. Stroke or evidence of ischemia of the kidneys, abdominal viscera, and lower extremities may result from embolization of atheroma or thrombus from a severely arteriosclerotic aorta or from malperfusion-related sequalae of chronic aortic dissection.

Signs

Direct physical signs of the presence of a thoracic aortic aneurysm are uncommon. In earlier times, a pulsating mass of the anterior chest was the first evidence of a syphilitic aneurysm of the ascending aorta; rarely, such an aneurysm eroded the sternum and ruptured, resulting in fatal hemorrhage. Signs of aortic regurgitation (bounding peripheral pulses, an aortic diastolic murmur) may be present in patients with large aneurysms of the aortic root, as is common in patients with Marfan syndrome. A pulsatile mass in the upper abdomen may be present in patients with thoracoabdominal aneurysms and warrants careful evaluation. Evidence for embolization of atheroma or thrombus from an aneurysm or from a severely arteriosclerotic aorta to the lower extremities (blue toe syndrome) may occasionally be the first indication of severe aortic disease. Unexplained bleeding raises suspicion of an aortic fistula. Additionally, aortic disease may be detected during evaluation of nonspecific symptoms concerning family history or as part of a recognized congenital cardiovascular condition.

Imaging techniques

The importance of imaging in managing aortic disease cannot be understated—a definitive diagnosis relies on high-quality imaging. The modality of imaging depends on what is institutionally available and on the patient’s condition. Once aortic disease is established, the aorta is carefully monitored until a diameter-based threshold of repair is met or until symptoms develop. Managing aortic disease typically requires an enhanced awareness of emerging symptoms through patient education and regularly repeated imaging studies. Efforts have been made in recent years to standardize imaging surveillance protocols and develop best practices. These include using a single imaging operator whenever possible, having the previous imaging study available during testing for comparison, and using specific anatomic landmarks perpendicular to the axis of blood flow. ^,

Chest radiography.

Findings on the chest radiograph, such as a widened mediastinum, may suggest a thoracic aortic aneurysm. Ascending aortic aneurysms produce a convex shadow to the right of the cardiac silhouette ( Fig. 23.5 ); those of the arch, an anterior and left-sided shadow ( Fig. 23.6 , A-B ); those of the descending thoracic aorta, a shadow to the left and posteriorly ( Fig. 23.7 ), and of the thoracoabdominal aorta ( Fig. 23.7 , B-C ). However, many patients with aortic disease will have an unremarkable chest radiograph. Substantial enlargement of the ascending aorta may be confined to the retrosternal area so that the aortic silhouette appears normal. Any suspicion of aortic disease generally requires a more accurate diagnostic modality for definitive diagnosis.

A chest radiograph presents both lungs with rib outlines, a central mediastinal shadow, the heart shadow, and an upper contour that curves toward the right side. — • Figure 23.5

A pair of chest radiographs labeled A and B presents a frontal view and a lateral view of the lungs, ribs, heart shadow, and central mediastinum. The pair of chest radiographs labeled A and B presents A as a frontal view with both lungs, rib outlines, a central mediastinal shadow, and a rounded contour on the left side, and B as a lateral view with the lung field, rib outlines, and a rounded contour projecting forward. — • Figure 23.6

• Figure 23.7

Chest radiograph of (A) a patient with large but well-localized aneurysm of mid-descending thoracic aorta, and a (B) patient with a calcified rim (arrows) in the aortic wall of a thoracoabdominal aortic aneurysm in an anteroposterior and lateral view.

(Printed with permission of Baylor College of Medicine.)

Computed tomography.

Computed tomographic (CT) imaging is the most widely used noninvasive technique for diagnosing thoracic aortic disease. It is used with and without contrast agents. This imaging is rapidly acquired and provides information about size, location, type, and extent of aortic disease ( Fig. 23.8 ). Importantly, the external diameter is measured, and both the thoracic and the abdominal aorta should be examined. CT imaging is of particular value in identifying aortic dissection, documenting the growth rate and diameter of aneurysms, and, thus, determining the timing of operative intervention in asymptomatic patients. It is useful in identifying anatomic variants, branch vessel involvement, determining the severity and extent of thickening or calcification of the aortic wall in patients with severe aortic arteriosclerosis, and locating thrombus. CT is also useful for detecting IMH (see Fig. 23.2 ) and penetrating arteriosclerotic ulcers. Three-dimensional (3D; Fig. 23.9 ) data rendering is widely available and facilitates patient education and operative planning as this technique clearly depicts the extent of disease, aberrant anatomy, and in the case of aortic dissection, can improve understanding of entry tears and communication sites between the true and false lumens and determine from which lumen a branching artery originates.

A C T scan in a transverse thoracic section presents the vertebra, ribs, lung fields, mediastinal structures, and a large, rounded contour along the descending aorta. — • Figure 23.8

A three-dimensional C T reconstruction presents a curved tubular aortic structure with multiple branch vessels. The three-dimensional C T reconstruction presents an elongated tubular aorta with pronounced curves, widened segments, and several branch vessels extending from the thoracic and abdominal portions. — • Figure 23.9

Additionally, CT imaging is a highly valued imaging modality to evaluate patients postoperatively as part of imaging surveillance protocols (e.g., finding late complications or new aneurysms). However, when used to follow patients with chronic aortic dissection, evidence suggests that the false lumen may be more difficult to accurately measure—substantial variability has been noted between raters. Recently, substantial effort has been made to increase awareness of best practices for serial CT imaging in patients with chronic aortic dissection; such patients are typically followed for several years before a diameter-based threshold of repair is reached.

The principal disadvantage of CT is that it requires the use of contrast medium for precise delineation of aortic disease. Contrast-induced nephropathy may occur, especially in poorly hydrated patients, and its use may be contraindicated in patients with allergies to contrast agents or with renal insufficiency. ^, ^,

Radiation-induced malignancy in patients with thoracic aortic disease who require periodic CT imaging is a concern; this concern is amplified in clinicians, especially because of the (C) prominence of endovascular repair, which is highly dependent on advanced imaging techniques. Techniques to reduce radiation exposure (e.g., appropriate shielding, radiation dose reduction and management, and algorithms to improve system efficiency) have been implemented to minimize this risk.

Magnetic resonance.

Magnetic resonance (MR) provides equivalent imaging for diagnosing diseases of the thoracic and thoracoabdominal aorta. It is used with and without contrast agents ( Fig. 23.10 ), which are generally considered less nephrotoxic than those used to acquire CT imaging—the use of contrast (to provide MR angiography) mimics the role of conventional aortography. In certain applications, a single study can provide information similar to that obtained from a combination of echocardiography, CT, and angiography. It provides excellent imaging of aortic dissections and can accurately identify thrombus formation and sites of entry. It can also differentiate periaortic hematoma from thrombosis of a false aneurysm. Breath-holding and 3D magnetic resonance angiography permit examination of the entire thoracic aorta, its major branches, the pericardium, the aortic valve, and the contractile pattern of the left ventricle. Contrast-enhanced, time-resolved, 3D MR angiography using agents such as gadolinium provides excellent images of the aorta and its major branches, comparable with those obtained by conventional aortography ( Fig. 23.10 B). Of interest, four-dimensional flow-sensitive (4D flow) MRA has been introduced as a means of assessing aortic wall shear stress, which may be useful in predicting complications and adjusting the timing of intervention to prevent them. ^, ^,

Compared with CT, current disadvantages of magnetic resonance imaging (MRI) include a longer time to complete the study (which sometimes necessitates patient sedation), greater cost and limited institutional availability, inaccessibility to patients who are connected to ventilators and monitoring devices, and contraindication in patients with metallic implants, pacemakers, and defibrillators. Use of MRI with a contrast agent (gadolinium compounds) is associated with a risk of nephrogenic systemic sclerosis. ^, ^,

Echocardiography.

Transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) play an important and complementary role in evaluating aortic disease. ^, ^, Notably, TTE is nearly universally available, noninvasive, and can quickly visualize the ascending aorta, aortic arch, and supra-aortic vessels, in addition to structures within the heart; furthermore, a subcostal, suprasternal, or parasternal view can be used to visualize the descending thoracic aorta. However, certain thoracic structures can weaken or distort the ultrasound signal, reducing overall image quality.

TEE is a valuable tool because it can visualize the descending thoracic aorta from the left subclavian artery to the celiac axis, although its use to fully image the aortic arch or areas below the diaphragm level is limited. As a diagnostic tool, it is generally considered superior to TEE, and when used intraoperatively, it is invaluable for assessing presence of arteriosclerosis, including mobile or pedunculated atheroma in the thoracic aorta, hemopericardium, malperfusion, competency of the aortic valve before CPB is established, adequacy of any reparative procedures on the aortic valve, and additionally provides information about ventricular function and function of the mitral and tricuspid valves. It can be performed rapidly, with minimal morbidity, and has emerged as the most useful and accurate technique for diagnosing acute aortic dissection (see Chapter 22 ).

Disadvantages of TEE include lack of availability at small centers and during off hours, operator dependence, invasiveness, discomfort, and the likely need for sedation may limit use.

Aortography.

Aortography relies on the release of contrast dye through a catheter during radiography and was a widely used imaging technique in past eras to determine the extent of aortic disease and formulate an approach to repair in advance of surgery. It provides information about location of aneurysms, particularly in relation to major branches of the aorta in the chest and upper abdomen ( Fig. 23.11 ). It also defines areas of relatively normal aorta proximal and distal to aneurysms. Selective injections of the coronary, brachiocephalic, visceral, and renal arteries provide important information that permits more accurate assessment of disease and anatomic landmarks. In contemporary use, multidetector CT angiography has largely replaced aortography for anatomic studies that are required for treating and monitoring aortic disease. However, aortography remains widely used in contemporary endovascular aortic repair to visualize the aorta and branching arteries in real-time to guide the placement of stent-grafts or other devices that are used to repair the aorta, ensuring that they are positioned correctly.

A pair of thoracic aortograms, labeled A and B, shows contrast-filled aortic contours in frontal and lateral views. The pair of thoracic aortograms labeled A and B shows A as a frontal view with a contrast-filled aortic arch and arrows pointing to labels B R, L C C, and L S A, and B as a lateral view with the aortic arch outlined in contrast and arrows marking the same labels B R, L C C, and L S A along the upper portion of the arch. — • Figure 23.11

A disadvantage of aortography is that the size of large aneurysms may be underestimated because of the presence of thrombus. Other disadvantages include the risk of allergic reactions after injection of contrast medium and risk of renal failure in patients with impaired renal function.

Ultrasonography.

Intraoperative epiaortic ultrasound imaging of the thoracic aorta is useful for detecting arteriosclerosis and identifying the distal end of a previous ET graft in the descending thoracic aorta. The presence of severe arteriosclerosis, including mobile or pedunculated atheroma, may necessitate alterations in surgical technique to avoid embolization of atheromatous debris to the brain and other organs during cardiac and thoracic aortic operations (see Fig. 23.4 A). Epiaortic ultrasound imaging is more accurate than palpation of the aorta and is considered more accurate than TEE for detecting atheromatous disease in the ascending aorta.

Intravascular ultrasonography (IVUS) is emerging as a useful diagnostic aid and adjunct during open or endovascular aortic repair. It is especially helpful in cases of aortic dissection or traumatic aortic injury. IVUS may resolve diagnostic uncertainty as it allows high-resolution imaging of the aortic wall and branching arteries, dynamic visualization of intimal lesions and filling defects, and facilitates the selection of landing zones during an endovascular repair. Disadvantages of IVUS include inaccuracy related to operator dependence, invasiveness, and cost. ^,

Preoperative evaluation

Because myocardial infarction, respiratory failure, renal failure, and stroke are the principal causes of mortality and morbidity after operations on the thoracic aorta, preoperative assessment of the function of these organ systems is essential. Once these systems are evaluated, optimization efforts are prioritized to enhance operative survival. If evaluation indicates marginal function, frailty, age, and other comorbidities (including life-limiting terminal conditions), these are all considered to determine if relative operative risk prohibits open surgical or endovascular repair.

Cardiac function.

Because of the high prevalence of ischemic heart disease in older individuals, particularly those with degenerative aneurysms, assessment of cardiac function is necessary when an elective operation is contemplated, especially for those with a history of myocardial infarction or angina pectoris and those older than 50 years. Patients with symptoms or electrocardiographic (ECG) changes indicative of myocardial ischemia should undergo stress myocardial perfusion testing and coronary angiography when indicated. Patients with valvar heart disease are evaluated with echocardiography and cardiac catheterization. To optimize patients, clinically important coronary artery disease should be treated with percutaneous catheter interventional techniques or bypass grafting, and valvar heart disease by valve repair or replacement before or, in some cases, at the time of the procedure on the thoracic aorta.

Pulmonary function.

History of smoking and presence of chronic pulmonary disease are important predictors of respiratory failure, and they are frequently present in patients who require operations on the descending thoracic and thoracoabdominal aorta. Pulmonary function tests, including spirometric assessment, are useful to better understand patient-specific risk factors. For patients diagnosed with chronic obstructive pulmonary disease, it may be helpful to subsequently categorize patients by GOLD status, which uses four categories to classify patients from low to very severe disease. Arterial blood gas analysis should be performed in patients with chronic pulmonary disease. Patient optimization is multifaceted and includes exercise, weight loss, incentive spirometry training, and other measures. If reversible restrictive disease or excessive sputum production is present, antibiotics and bronchodilators should be administered preoperatively. Cessation of smoking for at least 4 weeks is recommended.

Renal function.

Preoperative renal dysfunction is the most important predictor of acute renal failure and a strong predictor of other major adverse outcomes after operations on the thoracic and thoracoabdominal aorta. ^, Although creatinine and blood urea nitrogen are routinely measured preoperatively, their predictive value for postoperative renal failure is limited. Staging patients by chronic kidney disease (defined as a preoperative estimated glomerular filtration rate <60 mL/min/1.73 m ² and described as advanced if <45 mL/min/1.73 m ²) may better predict operative risk. For patients with advanced chronic kidney disease, it is helpful to discuss the possibility of postoperative renal failure dialysis with the patient and family as well as to initiate nephrology consultation. Preoperative hydration and avoidance of intravenous contrast agents (when possible, and countered with N-acetylcysteine as needed), hypotension; low cardiac output; and hypovolemia in the perioperative period are important mechanisms for reducing the prevalence of this complication.

Neurologic function.

To minimize risk of stroke or reversible ischemic neurologic deficits, imaging of the carotid, brachiocephalic, and intracranial arteries, when indicated, should be performed preoperatively in patients with a history of stroke, transient ischemic attack, or other risk factors for cerebrovascular disease. Patients with a history of stroke should additionally undergo CT imaging of the head. Patients with substantial stenosis of one or both common or internal carotid arteries should be considered for carotid endarterectomy or stenting before elective operations on the thoracic aorta.

Natural history

Aneurysm

It is generally understood that the aorta dilates with age, and its diameter is relative to body size. However, despite decades of study, there remains much to be learned about the natural history of the thoracic and thoracoabdominal aortic pathology—including nuanced distinctions between aneurysm and dissection. Survivors of acute aortic dissection will often experience progressive aortic dilation of the residual dissected native aorta. In patients with acute DeBakey type I aortic dissection, the index repair typically prioritizes operative survival. Thus, the repair is often limited to the proximal aspect of the aortic arch (i.e., a hemiarch repair); in many patients, the remaining residually dissected arch progressive dilates over a variable period until a diameter-based threshold of repair is reached. Likewise, early survivors of DeBakey type III aortic dissection are commonly medically managed for a variable period until the distal aorta is sufficiently dilated to warrant repair.

Classic studies of thoracic and TAAAs included patients who had not undergone operative treatment at the time of diagnosis and identified rupture of the aneurysm as the most common cause of death. ^, Additionally, this evidence suggested that the rate of rupture for aneurysms with chronic dissection substantially exceeded that of aneurysms without dissection, which also tended to occur at a smaller aortic diameter. ^, Survival of patients with thoracic, thoracoabdominal, and abdominal aneurysms in the study of Perko and colleagues is shown in Fig. 23.12 .

A survival graph shows three step-line curves labeled T A A, T-A A A, and A A A across a 0 to 10 year range and a 0 to 1 survival range, with a table beneath the graph. The survival graph shows a vertical axis labeled Proportion surviving, ranging from 0 to 1, and a horizontal axis labeled Years, ranging from 0 to 10. Step-line curves show for T A A marked with triangles, T-A A A marked with circles, and A A A marked with squares. A table beneath the graph lists the yearly counts as follows T A A shows 57, 32, 30, 23, 14, 12, 11, 10, and 7 T-A A A shows 53, 30, 21, 17, 11, 8, 5, and 2. A A A shows 60, 34, 27, 17, 10, 3, and 3. The label P equals point 6 shown above the plotted curves. — • Figure 23.12

In time, fundamental concepts emerged, including the observation that the size of a thoracic aneurysm at initial evaluation appears to be the most important predictor of rupture. Aneurysms that are 5.0 cm to 6.0 cm in diameter have a faster rate of growth and a greater propensity for rupture than smaller ones. ^, ^, Rupture is often preceded by symptoms; there is general agreement that operative intervention should be performed on an urgent or emergency basis in nearly all symptomatic patients with clear-cut symptoms. Bickerstaff and colleagues reported that once symptoms developed, the mean time to rupture was 2 years. Efforts were made to develop criteria for surgical intervention that largely relied on aortic diameter. ^, In the 1999 report by Coady and colleagues, the risk of a serious distal aortic complication increased dramatically at 7.0 cm (the hinge point); thus, the target for repair was set at 6.5 cm to avoid complication. In time, these and other studies formed the basis of diameter-based thresholds for aortic repair in practice guidelines. ^,

Currently, experts at Yale suggest that the downward-trending hinge points for aortic events should result in a smaller diameter-based threshold of repair. This suggestion is based on the understanding that adverse aortic events—namely aortic dissection, rupture, and death—may occur in patients whose aortic size has not yet reached the dimensions of repair, commonly recognized as 5.5 to 6.0 cm in contemporary eras. Examining longitudinal data from 907 patients presenting with descending thoracic and TAAAs greater than 3.0 cm, Zafar and colleagues emphasized that it may be impossible to use a diameter-based threshold of repair to prevent distal aortic dissection; far below current guidelines, the median aortic diameter prior to dissection was only 4.1 cm. Additionally, with a larger sample size than their earlier work, the authors were able to analyze the risk of aortic rupture and aortic death separately. As a result, the hinge points of these events have shifted to lower diameters (from 7.0 cm hinge point to 6.5 cm and 6.0 cm, respectively).

Large population-based studies from Korea (n=2353) and Germany (n=1959) established diameter-based trends by age and sex, with older men (>70 years) having the largest absolute aortic diameters (3.7 and 3.8 cm for the ascending aorta compared to 2.7 and 3.0 cm for the descending thoracic aorta, respectively). ^, Using serial CT imaging at least 6 years apart, yearly growth rates in a Korean population without aneurysmal disease were determined to be 0.15 mm per year for the ascending aorta, 0.12 mm per year for the aortic arch, and 0.13 mm per year for the descending thoracic aorta. Of interest, emerging evidence suggests that although men tend to have a larger aortic diameter, the aortic size index (defined as the aortic diameter [cm] divided by body surface area [m ²]) is greater in women than in men.

Notably, the rate of aortic expansion is often substantially greater in patients with heritable aortopathy or with aneurysmal disease and may differ in subsets of patients. Although patients with Turner syndrome and bicuspid aortic valves had relatively minimal proximal aortic expansion (i.e., 0.02-0.03 cm per year and 0.03-0.06 cm per year depending on location and phenotype, respectively), ^, patients with Marfan syndrome had much larger rates of proximal aortic expansion (i.e., 0.26 cm per year and increasing to 0.46 cm per year at >6.0 cm). The mean growth rates for the ascending aorta in patients with the proximal aortic disease were modest (i.e., 0.02 cm per year and 0.95 mL per year). ^, For patients with aortic arch aneurysms, the yearly mean expansion rate was 0.25 cm per year. In a large series of patients with distal aortic disease, the mean aortic growth rate was 0.19 cm per year; however, this rate sharply increased as the aorta became substantially larger (i.e., 0.42 cm per year at 8.0 cm). In patients with prior aortic repair and residual distal aortic dissection, the expansion process can vary, with some patients remaining stable and others expanding more rapidly (i.e., as much as 0.28-0.53 cm per year in patients experiencing growth). ^,

For most patients, medical treatment is of limited value in managing thoracic aneurysms. Control of systemic hypertension (≥130 mmHg average systolic or ≥80 mmHg average diastolic), when present, is important to reduce aortic wall stress despite uncertainty between aortic expansion rates and hypertension. Additionally, uncontrolled hypertension is a risk factor for aortic dissection. The use of antihypertensive medications is recommended in patients with thoracic aortic disease and hypertension (Class 1; level of evidence B-NR). Statin therapy is reasonable for patients with thoracic aneurysms and clinical evidence of atherosclerosis (Class 2a; level of evidence C-LD). Although no prospective trials have demonstrated a beneficial effect of cessation of smoking on rates of progression of thoracic aortic disease, current practice guidelines recommend smoking cessation (Class 1; level of evidence C-LD).

For patients with Marfan syndrome, the use of β-adrenergic blocking agents decreases the progression of aortic dilation and may slow the rate of aortic dilation in those with chronic aortic dissection in the absence of this syndrome. ^, Angiotensin receptor blockers and angiotensin-converting enzyme inhibitors may slow the growth rate of aneurysms in patients with Marfan syndrome, although definitive evidence is lacking. The use of β-adrenergic blocking agents alongside angiotensin receptor blockers may be of benefit. Current practice guidelines support their use (Class 1 with level of evidence A and Class 2a with level of evidence C-LD, respectively).

Other conditions

The natural history of PAU and IMH is variable. Patients with PAU are commonly asymptomatic, and in most cases, the ulcers remain stable and may even regress. However, in a small percentage of cases, they may disperse emboli or progressively enlarge, forming saccular aneurysms that may rupture. Additionally, PAU can coexist with IMH. A single-institution study of 388 PAUs found that most (93%) were located in the distal aorta (with only 7% located in the proximal aorta) and that many were associated with saccular aneurysm (28%) or IMH (14%); notably, only 18% of these patients experienced symptoms, although this was prognostic for progression of disease. Additionally, a systematic review identified PAUs with a depth greater than 10 mm to be more likely to progress toward intervention.

Likewise, an IMH is a dynamic entity that may regress, expand, or progress to classic aortic dissection. Its natural history varies according to the location of the hematoma in the thoracic aorta and geographic location, with IMH being more common in Asia than it is elsewhere. A higher prevalence of dissection and death has been observed among patients with hematomas in the ascending aorta and arch than in those with hematomas in the descending thoracic aorta. And thus, IMH that occur within the proximal aorta are most commonly repaired in the acute phase, while those in the distal aorta are more frequently treated with medical management when discovered and repaired in the chronic phase. Other than having a diameter greater than 50 mm, factors prognostic of the need for intervention include persistent symptoms, rapid enlargement, and a hematoma wall thickness greater than 11 mm.

Patients with severe atherosclerotic burden face the risk of emboli dispersal that can lead to cerebral infarction or embolization to the visceral, renal, and peripheral arteries. This burden appears most commonly in the ascending aorta and aortic arch. Within the arch, high-risk features include thick arteriosclerotic plaques (>4 mm in thickness), ulcerated plaques, and mobile thrombus. Patients with severe aortic arteriosclerosis are at risk for procedure-related embolization and stroke during repair; risk centers on events during manipulation of the ascending aorta during coronary artery bypass grafting, advancing wires as a part of endovascular repair, and other cardiovascular procedures. ^, ^,

Among patients with the conditions described earlier, death due to coexisting cardiovascular disease is common.

Technique of operation

Preparations for aortic repair

Currently, options for repair differ by aortic segment (e.g., ascending aorta vs. aortic arch versus descending thoracic versus thoracoabdominal aorta). When the aortic valve or aortic root is diseased and requires repair or replacement, these techniques are those described under Technique of Operation in Chapter 12 . Repair of the ascending aorta and aortic arch is most commonly performed as an open surgical repair, although experimental and off-label procedures may be infrequently used in patients unable to withstand open repair. In contrast, repair of the descending thoracic aorta is most commonly performed as an endovascular procedure, and open repair is commonly limited to patient-specific scenarios, such as the presence of HTAD, infection, or a failure of previous endovascular repair. Regarding thoracoabdominal aortic repair, the gold standard remains open repair, with the addition of risk-mitigating adjuncts to reduce distal ischemia; however, endovascular thoracoabdominal aortic repair is a promising technology that may reduce operative risk in select patients. Circumstances that may limit endovascular repair include the absence of suitable arterial access, the inability to rapidly manufacture a customized device, and a lack of healthy aortic tissue for proximal or distal landing zones. Preparation for repair should include any needed adjustment of the patient’s current medication as well as a roadmap for perioperative adjustment; antibiotics are typically administered prior to incision to avoid infection. ^,

Ascending aorta replacement

The surgical approach to isolated ascending aortic aneurysm replacement involves excising the aneurysmal aortic segment and replacing it with a tube graft. This surgery is not very different from open surgery to treat coronary artery disease or valvular disease. Although it is certainly possible to carry out a partial upper median sternotomy and/or a right anterior thoracotomy for ascending aortic replacement, our preference has been to use a median sternotomy. A CT scan confirming the position of the ascending aorta relative to the sternum and anterior chest wall is critical in planning surgical entry; this is especially important in treating late complications of prior aortic repair, such as pseudoaneurysm.

After anesthesia induction, venous access is obtained with a large-bore central catheter and several large peripheral catheters. A radial arterial catheter is inserted to monitor blood pressure and withdraw blood samples. This is placed in the left radial artery in patients with ascending aortic and proximal arch disease; if there is any uncertainty during monitoring, bilateral placement may be appropriate. Isolated ascending aortic replacement is typically performed using CPB under passive mildly hypothermic conditions (approximately 28°C-32°C) and without any significant additional pump time for cooling or rewarming. The selection of cannulation sites for CPB pump return varies based on anatomic considerations. Central cannulation is generally preferred to peripheral cannulation, and femoral artery cannulation has been largely supplanted except when distance from an infected field is needed.

In many cases with isolated ascending aortic aneurysm, it is certainly appropriate to directly cannulate the distal ascending aorta (usually immediately proximal to the innominate artery or along the lesser curvature of the aortic arch) over a wire, using TEE guidance. Cannulation of the innominate, carotid, or right axillary artery may be performed directly or by suturing a small length of an 8- or 10-mm conduit graft end-to-side to the artery. When the right axillary artery is used to prevent hyperperfusion of the right upper extremity, modest constriction distal to the cannulation site may be necessary. Avoiding the extra incision underneath the right clavicle to cannulate the axillary artery has increased the popularity of innominate artery cannulation as a preferred site for pump return. If there are no additional cardiac issues requiring bicaval cannulation, dual-stage venous cannulation is commonly used.

After CPB is established and the heart is vented by placing a catheter in the right superior pulmonary vein, a single atraumatic aortic cross-clamp is placed immediately proximal to the innominate artery. The standard approach involves transecting the aorta just proximal to the aortic cross-clamp and just above the sinutubular junction with subsequent excision. Using continuous 3-0 or 4-0 polypropylene sutures, the distal anastomosis is performed using an appropriately sized Dacron graft. The aortic graft is cut to the appropriate length and anastomosed to the proximal aorta using continuous suture, as before ( Fig. 23.13 ). As needed, the anastomoses may be additionally secured using a strip of felt. Commonly, replacement of an isolated ascending aortic aneurysm requires a graft that is 24 to 28 mm in diameter. In adults, it is unusual to require a larger graft; if a patient requires a 30-mm or larger graft distally, and the distal ascending aorta may be dilated to around 4 cm or greater, the procedure should be extended as a beveled hemiarch replacement and performed under HCA.

An illustration labeled A and B shows an aorta with an enlarged segment and a graft-replaced segment. The illustration labeled A and B shows A as an aorta with a large, rounded enlargement on the ascending portion, and B as the same aorta with the enlarged segment removed and replaced by a ribbed tube graft attached between the upper arch branches and the lower portion of the vessel. — • Figure 23.13

Retrograde cardioplegia is not strictly necessary in isolated ascending aortic repair, and a single dose of del Nido cardioplegia infused directly into the coronary arteries is used by some surgeons (see Chapter 3 ). It has become routine in most programs to use transesophageal echocardiography to assess function of the cardiac valves, size of the aorta, and type and extent of aortic disease, and to monitor myocardial function; however, in patients with a simple isolated ascending aorta replacement without valvular or coronary issues and with a normal ejection fraction, its use may be helpful but not necessary. After CPB is discontinued, cannulae and venting catheters are removed; it is important to transect any conduit grafts (used to ease cannulation) flush with the aorta or branching artery to avoid creating the potential for an imaging artifact.

Severe diffuse arteriosclerosis or mobile atheroma involving the ascending aorta that is encountered during coronary artery bypass grafting or valve replacement can be managed by resection and graft replacement or by endarterectomy. ^,

Aortic arch replacement

Although aortic disease can be confined to the aortic arch (segment of the thoracic aorta that extends from the proximal origin of the brachiocephalic artery to the distal origin of the left subclavian artery), most aneurysms in this area are associated with aneurysmal disease of the ascending aorta or the adjacent descending thoracic aorta. Thus, aneurysms of the aortic arch vary in size and extent, and techniques of repair vary. Furthermore, at the time of aortic arch repair, consideration should be given to the possibility of aortic disease progressing distally. Common approaches to repair include hemiarch replacement of the lesser curvature of the aortic arch and total aortic arch replacement incorporating the brachiocephalic arteries, which can be extended into the proximal portion of the descending thoracic aorta using a classic ET or frozen ET approach; as needed in patients unable to withstand open repair, hybrid strategies combining open and endovascular repair are used.

Surgical repair of the aortic arch complex: unlike other aortic sections, its replacement typically disrupts both cerebral and distal aortic perfusion, leaving the brain, spinal cord, and other organs vulnerable to ischemia. Most aortic arch repairs rely on a period of systemic circulatory arrest combined with varying degrees of hypothermia to protect the brain and other vital organs. During cooling, the heart spontaneously fibrillates and becomes quiescent; during rewarming, spontaneous defibrillation occurs in most patients when the nasopharyngeal temperature reaches 26°C to 28°C. Although HCA is described in Section IV of Chapter 2 , we present a brief overview. HCA is the most widely used technique for protecting the brain during operations on the aortic arch and remains a viable option when arch repair of limited duration (i.e., <30 min) is anticipated. Although HCA was first used at very low temperatures (profound [≤14°C] and deep [14.1°C–20°C]), a wide spectrum of temperatures are employed today, including warmer temperature targets (moderate [20.1°C–28°C] and mild [28.1°C–34°C]). Because prolonged HCA is associated with increased operative death and cerebral and other complications, supplemental cerebral perfusion techniques were developed to reduce these risks. There are two forms of cerebral perfusion used with HCA: antegrade and retrograde ( Figs. 23.14 and 23.15 ). ACP delivers oxygenated blood in a physiologic manner; it is typically carried out in moderate or mild hypothermia (≥20°C). ^, The understanding that ACP adequately delivers oxygen to the brain has facilitated the use of more moderate temperatures during HCA. Retrograde cerebral perfusion delivers oxygenated blood via the superior vena cava in a non-physiologic manner that reverses the direction of blood flow; it is carried out in deep or profound hypothermia (<20°C). ^, This retrograde flow is thought to benefit repair with improved continuous distribution of cooling and embolic flush rather than by providing oxygen. Cerebral perfusion is controlled by varying flow rates and pressure as blood flow is delivered, and near-infrared spectroscopy is used to monitor cerebral oxygenation during repair. Although ACP is most commonly delivered unilaterally (and depends on collateral circulation from the patient’s intact circle of Willis) if monitoring detects inadequate oxygenation, a second catheter is added to the left common carotid artery to provide bilateral perfusion. Temperature targets during HCA vary widely by surgeon and institutional preference, and there is little definitive evidence of the superiority of one technique over another. ^, ^,

An illustration labeled A, B, C, and D shows different cannulation routes for aortic arch replacement with arrows indicating blood flow through grafts and tubing around the heart. The illustration labeled A, B, C, and D shows different cannulation routes for aortic arch replacement under hypothermic circulatory arrest with antegrade cerebral perfusion. Panel A shows a graft connected to the right axillary artery with arrows indicating blood flow through the graft. Panel B shows a graft attached to the innominate artery with arrows indicating flow direction. Panel C shows cannulation tubing routed from the right axillary artery toward the aorta, with venous lines entering the right atrium and inferior vena cava and arrows marking flow through the circuit. Panel D shows cannulation tubing routed from the innominate artery, with venous lines entering the right atrium and inferior vena cava and arrows indicating blood flow. A separate catheter enters the left common carotid artery in the lower panels. — • Figure 23.14

An illustration shows a heart connected to a reservoir, centrifugal pump, heat exchanger, oxygenator, arterial filter, and flow probe with arrows marking flow through the circuit. The illustration shows a heart connected to an extracorporeal circuit used for retrograde cerebral perfusion. The circuit begins at a reservoir, continues through a centrifugal pump, then passes through a heat exchanger oxygenator. From there, tubing leads through an arterial filter and a flow probe before returning toward the heart. Arrows along the tubing indicate the direction of blood flow through each labeled component. Additional arrows show blood returning from the heart toward the venous side of the circuit. Cannulation tubing enters the heart at the vena cavae and exits at the aorta. — • Figure 23.15

Likewise, the choice of cannulation sites varies by surgeon and institutional preference. Because of the increased risk of dislodging and embolizing atheromatous material from retrograde perfusion associated with femoral artery cannulation, axillary artery and innominate artery cannulation are used as inflow sites (see Fig. 23.14 ) with increasing frequency for operations that involve the aortic arch. ^, ^, Alternative sites for establishing return of arterial blood from the pump-oxygenator include the left common carotid artery and left subclavian artery; direct aortic cannulation is uncommon during aortic arch replacement. Separate cannulae are placed in the superior and inferior venae cavae for venous return to the CPB circuit.

Standard procedures to prepare the patient for HCA are described later. The patient is placed in a supine position in preparation for median sternotomy. Commonly, the patient’s head is packed in ice as a protective measure. After endotracheal anesthesia induction and sterile preparation, venous access is obtained with a large-bore central catheter and several large peripheral catheters. A radial arterial catheter is inserted for monitoring blood pressure and withdrawing blood samples; this is generally placed in the left radial artery, left brachial artery, or left common femoral artery by placing a 5-French sheath using ultrasound and micropuncture technique. Because establishing HCA depends on the use of CPB, a full dose of heparin is provided. Cerebral monitoring is established prior to anesthesia using near-infrared spectroscopy by placing probes within a support frame on the patient’s forehead. Oxygen saturation values are available in real-time on the display as a percentage and recorded throughout the entire procedure; during repair, a reduction of (regional oxygen saturation) rS o ₂ by >20% or an absolute rS o ₂ <50% is considered to signify cerebral ischemia, which signals the need for prompt intervention. Transcranial Doppler is an additional tool for cerebral monitoring. During cooling, we additionally provide mannitol for cerebral protection. To maintain sinus rhythm, we administer magnesium, lidocaine, and amiodarone.

Hemiarch replacement.

Hemiarch replacement is somewhat less complex than other aortic arch repairs because these repairs do not directly incorporate the brachiocephalic arteries. If the aneurysm involves only the proximal portion of the arch (often the disease is contiguous with disease in the ascending aorta or aortic root) and involves less than 50% of the aortic circumference, a single anastomosis between the replacement tube graft and the distal aorta can be performed by beveling the incision in the aorta beneath the brachiocephalic arteries, such that they are retained within a peninsula of aortic tissue. Thus, only the lesser curvature of the transverse aortic arch is replaced ( Fig. 23.16 ) . In patients with chronic thoracic aortic disease involving the proximal arch, hemiarch repair is commonly performed concomitantly with aortic root replacement—this is typically initiated first while the patient is cooled to the selected temperature target. Concomitant aortic root repair is not thought to confer added risk to elective arch repair.

An illustration labeled A and B shows a dilated aortic segment and a graft-replaced arch segment. The illustration labeled A and B shows changes before and after repair of a dilated aortic segment. Panel A shows a dilated aortic root, ascending aorta, and proximal portion of the transverse arch, with an arrow pointing toward the enlarged root. Panel B shows the same region after repair, with the dilated segment replaced by a curved tube graft attached to the remaining aortic segments. — • Figure 23.16

Repair is performed via median sternotomy using standard procedures for HCA as described earlier. A partial occluding clamp is placed on the distal aspect of the innominate artery, and an 8- or 10-mm Dacron graft is anastomosed end-to-side with 5-0 and 6-0 polypropylene suture to serve as the arterial inflow site during CPB. A dual-stage single cannula is inserted for venous return. The patient is placed on CPB, and a retrograde cardioplegia cannula may be placed via the right atrium into the coronary sinus. A left ventricular sump is then inserted via the right superior pulmonary vein. If the ascending aorta is not overly calcified and suitable for aortic clamping, the distal ascending aorta is cross-clamped proximal to the innominate artery using an atraumatic clamp. The aorta is then opened. Antegrade and retrograde cardioplegia are provided intermittently for myocardial protection. As the patient cools, any proximal aortic repair (e.g., aortic valve replacement, aortic root replacement, coronary artery bypass, and others) is initiated whenever possible (this process is more fully described in Chapter 12 ).

Once the patient is cooled to 24°C, HCA is initiated. The innominate artery is constricted with a Rumel tourniquet or a soft clamp, and the pump flow is set to 1.2 to 1.5 L/min to begin unilateral ACP. The aortic cross-clamp is removed, and a 13- to 15-Fr balloon perfusion catheter is placed within the left common carotid artery to provide bilateral ACP. Because the perfusion bed is the left common carotid and innominate arteries, CPB flows are set at 10 to 15 mL/kg/min. Pressure in the right radial artery is monitored and kept at 60 to 70 mmHg. The lesser curvature of the transverse aortic arch is resected, and an appropriately sized tube graft (i.e., usually between 24-30 mm in diameter) is anastomosed end-to-end using a running 3-0 or 4-0 polypropylene suture in a beveled hemiarch fashion. This anastomosis is then reinforced with 3-0 or 4-0 polypropylene mattress sutures with felt pledgets (if the tissue is friable) to aid hemostasis; another common technique for achieving a hemostatic anastomosis is to secure a strip of felt at the suture line. The innominate artery tourniquet is released, the balloon perfusion catheter is removed from the left common carotid artery, and CPB flows are increased back to a normal level. Air is evacuated from the graft, and then the replacement Dacron graft is clamped.

Attention is returned to the proximal aspect of repair; if there is a previous replacement graft, then the new graft is sutured to the old graft in an end-to-end fashion; if not, the graft is sutured to the sinutubular junction. Air is vented with the 19-gauge needle, the patient is placed in a head-down position, and the cross-clamp is removed. Rewarming is initiated with full CPB provided no more than a 10°C gradient is maintained between the water bath temperature and blood to decrease the risk of gaseous emboli formation. When the patient’s temperature reaches 36.5°C (nasopharyngeal), CPB is discontinued, and all cannulae are removed; overwarming the patient is strictly avoided to reduce cerebral insult. Two 36-Fr chest tubes are placed in the anterior mediastinum for drainage, and temporary pacing wires are placed.

Total arch replacement.

When the aneurysm involves the entire transverse aortic arch, it is replaced. However, unlike hemiarch repair, total aortic arch replacement must incorporate the brachiocephalic arteries, which adds complexity. Until improvements were made in cerebral perfusion and other supporting techniques, total arch replacement was typically a high-risk repair fraught with challenges. In contemporary repair, there are two basic strategies to manage these arteries—reimplantation and replacement (and combinations thereof). The most common way to reimplant the brachiocephalic arteries is to use an “ en bloc ” or island approach, in which a small patch containing the origins of these three arteries is reimplanted. Replacing the brachiocephalic arteries with individual branch grafts goes back to the early 1960s and typically followed an anatomic reconstruction. Currently, Y-graft or trifurcated, extraanatomic “debranching” approaches are favored in centers that routinely use ACP and have the additional advantage of facilitating a distal anastomosis proximal to the left subclavian artery ( Fig. 23.17 ). ^, ^, ^, ^, Because disease often extends into the descending thoracic or thoracoabdominal aorta, most commonly, total aortic arch replacement is performed with an ET or frozen ET extension. However, if disease is more limited, or if a graft has previously replaced the descending thoracic aorta, then repair does not extend beyond the distal anastomosis. If a previous descending thoracic or thoracoabdominal aortic repair is centered on a reverse ET approach, this graft is retrieved and used to facilitate arch repair.

An illustration labeled section A through section G shows sequential steps of a Y-graft and elephant trunk approach for total aortic arch replacement. The illustration labeled A through G shows sequential steps of a Y-graft and elephant trunk approach for total aortic arch replacement. Panel A shows the proximal brachiocephalic arteries exposed. Panel B shows secondary branches of the Y-graft sewn end to end to the transected left subclavian and left common carotid arteries, with proximal brachiocephalic stumps ligated. Panel C shows a balloon-tipped cannula placed within the double Y-graft and the innominate artery clamped and transected. Panel D shows the proximal Y-graft clamped and a collared elephant trunk graft positioned along the arch. Panel E shows the distal anastomosis between the elephant trunk graft and the aorta created between the innominate and left common carotid arteries. Panel F shows the arch graft clamped while perfusion is delivered through a side branch as the proximal ascending aorta is replaced. Panel G shows the main trunk of the double Y-graft trimmed and sewn to an oval opening on the ascending aortic graft. An inset shows an alternate configuration using a straight or curved graft with a distal anastomosis placed distal to the left subclavian artery. — • Figure 23.17

Standard sterile procedures to prepare the supine patient for aortic arch replacement are described more fully earlier.

A standard median sternotomy is performed, and arterial inflow is commonly established using the right axillary or innominate artery. If the right axillary artery is to be used, then an incision is made in the deltopectoral groove. The pectoralis minor muscle is exposed after the pectoralis major muscle is spread along its fibers to aid the location of the axillary artery. The lateral and medial cords of the brachial plexus are avoided. A 3- to 4-cm segment of the axillary artery is freed, and a vessel loop is placed around it; after 5000 units of heparin are given intravenously, a partial occluding clamp is placed on the artery. An 8- to 10-mm Dacron graft is then anastomosed to the axillary artery with a continuous 5-0 or 6-0 polypropylene suture. The conduit graft is clamped, the partially occluding clamp is removed, and the conduit graft is attached to the arterial arm of the bypass circuit. Full-dose heparin is provided just prior to attaching the cannula to the CPB circuit. A dual-stage venous cannula is placed in the right atrium with its tip in the inferior vena cava to achieve venous drainage. Routinely, we place a retrograde cardioplegia cannula in the coronary sinus and a sump drain in the left ventricle via the right superior pulmonary vein. CPB is initiated, and once an adequate activated clotting time (>480 seconds) is achieved, ventilation is discontinued. The innominate artery is encircled with a Rumel tourniquet in preparation for snaring when CPB is discontinued. Alternatively, a conduit graft may be anastomosed to the innominate artery to provide ACP.

Immediately after cardiac fibrillation (typically occurring at approximately 28°C-30°C), intermittent cardioplegia is delivered retrograde into the coronary sinus. This induces diastolic arrest that is then maintained by hypothermic conditions during repair. Alternatively, if the aorta can be safely cross-clamped (e.g., free of extensive calcification) and the integrity of the aortic valve is intact, cardioplegia can be given antegrade into the aortic root or provided directly into the coronary ostia once the aorta is opened under circulatory arrest. Cardioplegia is given about every 20 to 30 minutes thereafter.

Once CPB has been initiated and the heart is fully decompressed, the patient is cooled to a moderate target of 22°C to 24°C. CPB pump flows are brought down to about 10 to 15 mL/kg/min, and the Y-graft debranching process is started. First, the origins and proximal aspects of the brachiocephalic vessels are exposed. Next, the left subclavian artery is ligated near its origin with a heavy silk tie and transected. A secondary branch of the Y-graft is then sewn end-to-end to the left subclavian artery with a 5-0 or 6-0 polypropylene suture. Likewise, the left common carotid artery is ligated and transected, and the distal end is sewn end-to-end to another secondary of the Y-graft. If the distal portion of the arch is not aneurysmal, then a single Y-graft approach can be used instead of a double Y-graft; in this case, only the left common carotid artery is anastomosed to the Y-graft, the distal anastomosis will be moved forward, and the left subclavian artery left in its native state. These grafts are then de-aired and clamped. Once HCA is achieved, the arch is opened, the proximal portion of the innominate artery is ligated, and the distal end of the innominate artery is anastomosed end-to-end to the primary trunk of the Y-graft. If near-infrared spectroscopy (NIRS) monitoring shows a significant drop in cerebral oxygenation during this anastomosis, a balloon perfusion catheter can be inserted directly into the Y-graft to perfuse the left common carotid artery. Once the innominate anastomosis is completed, the Rumel tourniquet around its origins is removed. The Y-graft is de-aired and clamped proximally to maintain flow from the axillary artery to the two or three previously anastomosed brachiocephalic arteries while repair continues.

Next, the distal aortic anastomosis is performed using a straight or curved graft to complete an end-to-end distal anastomosis. Commonly, this distal anastomosis is performed in Zone 1 or Zone 2 ( Fig. 23.18 ). This provides better access to achieve a hemostatic anastomosis and places the anastomosis away from the recurrent laryngeal nerve. Once completed, the cross-clamp is moved onto the graft, and the rewarming process begins. After the proximal anastomosis is completed, the primary trunk of the Y-graft is anastomosed to a small opening made in the right anterolateral aspect of the ascending aortic graft in an end-to-side fashion using continuous 4-0 or 5-0 polypropylene suture. The Y-graft is oriented to prevent any kinking of the graft when it is pressurized with blood and compressed by the closed sternum. Although rewarming to 36.5°C can be initiated immediately after CPB is restarted, it is occasionally prudent to delay complete rewarming if extensive reconstruction is needed to repair the aortic valve or root. The retrograde cardioplegia catheter is removed. The patient is separated from bypass as soon as physiologic temperature is reached and appropriate criteria are met.

An illustration shows the aortic arch divided into numbered landing zones with labeled branch arteries. The illustration shows the ascending aorta, aortic arch, and descending thoracic aorta divided into numbered landing zones labeled 0 through 4. Zone 0 is marked on the ascending aorta beneath the origin of the innominate artery. Zone 1 is marked beneath the origin of the left common carotid artery. Zone 2 is marked beneath the origin of the left subclavian artery. Zone 3 is shown as a short curved segment distal to the left subclavian artery, and Zone 4 extends along the descending thoracic aorta beyond that segment. Labels identify the innominate artery, left common carotid artery, and left subclavian artery. — • Figure 23.18

Retrograde perfusion of the cerebral circulation is an alternative approach to ACP and is generally used with deeper levels of HCA, with and without the use of ACP. When it is used intermittently, it is commonly reserved for use at the completion of aortic arch reconstruction to flush debris from the brachiocephalic vessels. The technique involves either bicaval cannulation or placement of a balloon perfusion cannula in the superior vena cava.

Elephant trunk technique.

When the aneurysm involves more than just the very proximal descending thoracic aorta, a two-stage procedure may be considered. The decision whether to address the proximal or distal aorta first is based on symptoms, aneurysm size, and cardiac disease. Whenever possible, the symptomatic segment is addressed first. Borst and colleagues introduced a useful technique for performing the first stage, the “elephant trunk” procedure. ^, Essentially, a free-floating section of graft (the “trunk”) is placed within the proximal descending thoracic aorta (as part of a total aortic arch replacement) to facilitate subsequent repair of the distal aorta.

Important modifications were introduced by Crawford and colleagues and by Svensson, ^, and the technique continued to evolve as commercially available grafts were developed that included a collared skirt and a side-branch to provide distal aortic perfusion. If a grossly aneurysmal arch or substantial distance between branching arteries obscures visualization, the distal anastomosis can be created between arteries using the collared skirt rather than beyond the left subclavian artery (which is left in its native state, bypassed, or debranched). Additionally, a collared skirt compensates for any diameter mismatch between the graft and the aorta and facilitates a tension-free anastomosis (see Fig. 23.17 ).

Although there is no direct benefit of the ET approach during the initial arch repair, there are several advantages in the stage-2 repair, including easier dissection, shorter durations of aortic clamping, and safer clamping. Adhesions commonly obscure the pulmonary artery and esophagus; avoiding dissection around the distal arch reduces the chance of injury to these structures. During the second stage, a graft-to-graft proximal anastomosis is typical, which makes hemostasis easier to achieve. Lastly, this technique may reduce the risk of stroke (from potential embolization of atherosclerotic debris) because the aorta does not need to be clamped proximal to the left subclavian artery. A drawback of the ET approach is between-stage recovery, during which the unrepaired portion of the aorta could rupture. In general, for patients with a sufficiently dilated distal aorta, there is usually a 3- to 6-week interval between stages; if the patient is symptomatic, this period is commonly shortened. In patients with chronic aortic dissection, the use of the ET approach is sometimes speculative in anticipation of future needs.

ET repairs are typically performed via median sternotomy with standard preparation. ^, Often, the left common femoral artery is used for hemodynamic monitoring, establishing access with micropuncture and ultrasound to place a 4-Fr sheath. Reoperation is common in patients undergoing ET repair, many of whom have chronic aortic dissection or a prior aortic root replacement (i.e., Bentall procedure). If redo repair is complicated by the proximal aorta being directly adjacent to the sternal entry point, HCA may be initiated before chest reentry and at a slightly colder temperature (18°C-20°C) than our standard approach, and the right side may be additionally accessed via the right common femoral vein. The axillary and innominate arteries are common primary cannulation sites to provide ACP during HCA.

Once the sternum is divided, our preference is to place a partial occluding clamp on the distal aspect of the innominate artery (after 5000 units of heparin are given intravenously) and anastomose an 8- or 10-mm Dacron graft end-to-side using 5-0 or 6-0 polypropylene suture as the arterial inflow site. A retrograde cardioplegia cannula is placed via the right atrium in the coronary sinus, with intermittent cardioplegia delivered as described previously. A left ventricular sump is inserted via the right superior pulmonary vein. Once the patient is fully cooled to the target temperature of 22°C to 24°C, the innominate artery is occluded with a Rumel tourniquet, and flows are turned down to 1.2 to 1.5 L/min to initiate ACP. At this time, the aneurysm is directly opened. A 13- to 15-Fr balloon perfusion catheter is added to the left common carotid artery to provide bilateral ACP. A single Y-graft is used with a 12- to 14-mm primary graft and an 8- to 10-mm side branch. The side-branch graft is anastomosed end-to-end to the left common carotid artery using 5-0 or 6-0 polypropylene suture while maintaining cerebral perfusion by moving the balloon perfusion catheter into the side branch. The primary graft is then anastomosed to the very distal innominate artery with continuous 4-0 polypropylene suture. The aorta is transected between the left common carotid artery and the left subclavian artery. As needed in advance of repair, the left subclavian artery may be bypassed to the left common carotid artery; during repair, the left subclavian artery is then completely ligated.

The distal aspect of repair is initiated by placing a 24- to 30-mm ET graft (usually no longer than 10 cm in length) in the proximal portion of the descending thoracic aorta (DTA). In cases of chronic DeBakey type I aortic dissection, the dissecting septum is fenestrated, positioning the trunk so both the true and false lumens are perfused. In creation of the distal anastomosis, the graft’s collar is trimmed to match the diameter of the native aorta and continuous suture is added using 2-0 to 4-0 polypropylene suture; this distal anastomosis is commonly reinforced with either another layer of running polypropylene suture, pledgeted mattress sutures, or strips of Teflon. With the completion of the distal anastomosis, the graft is de-aired, a cross-clamp is applied to the proximal portion of the graft, and distal systemic perfusion is provided by connecting the side-branch of the ET graft as full CPB is reestablished, and the patient is rewarmed to 28°C. Varying portions of the ascending aorta are included as the proximal anastomosis is performed. Repair may additionally include the aortic valve or root. In patients undergoing reoperation, a graft-to-graft anastomosis is made after replacing any residual native aorta. The single Y-graft is sutured end-to-side to the main body of the graft after electrocautery is used to create a hole on the right anterior side of the graft’s ascending portion. The side-branch of the graft is tied flush with the graft; this prevents contrast from entering the residual “stub” of the side-branch during future imaging scans that mimic an anastomotic leak or rupture. Rewarming to 36.5°C begins, and closure is performed as described earlier.

Frozen elephant trunk technique.

Kato and colleagues are acknowledged as the earliest innovators to extend a stent-graft into the descending thoracic aorta as part of total aortic arch replacement. However, it was efforts from Hannover that popularized this approach, which has had widespread availability in Europe for over a decade. Before the US Food and Drug Administration (FDA) approved a single-piece hybrid prosthesis for the single-stage repair of extensive aortic disease, we used the skirted ET graft (as described earlier) as part of a standard ET repair and deployed a stent-graft in an open antegrade fashion inside of it as an off-label application. This secures and potentially depressurizes the aneurysm sac and also facilitates any future cannulation of the graft by fixating the free-floating trunk (useful if the second-stage ET procedure is endovascular). The Thoraflex Hybrid device (Terumo Aortic; Sunrise, FL) combines a gelatin-sealed woven polyester collared graft with a nitinol self-expanding stent-graft. In 2022, Thoraflex Hybrid device was approved by the FDA. Two configurations for brachiocephalic reattachment are available: a plain “tube” designed to be used as part of an island reattachment strategy and a branched version. The device is preloaded within a delivery system and available in two sizes based on shaft and stent-graft length (10 cm and 15 cm).

The frozen ET repair ( Fig. 23.19 ) is performed via a standard median sternotomy and using standard procedures as described earlier for total aortic arch. Briefly, after initiating HCA with ACP (as described earlier), the ascending aorta and transverse aortic arch are opened, with transection just beyond the left subclavian artery. A guidewire for the deployment procedure is inserted into the femoral artery and advanced retrograde with subsequent retrieval from the opening of the descending thoracic aorta. The tip of the device is threaded onto the guidewire and advanced into position in the lumen of the descending thoracic aorta in an antegrade fashion. After positioning, the stent-graft portion is deployed, and the delivery system is separated and removed. The distal anastomosis secures the device by suturing the collared skirt to the distal native aorta. Distal aortic perfusion is provided via a side branch. Then, using the nonstented graft portion of the device, the ascending aorta and aortic arch are replaced after incorporating the brachiocephalic arteries into the repair using an island or branched approach. Rewarming to 36.5°C begins, and closure is performed as described earlier.

An illustration labeled A to E shows sequential steps of a frozen elephant trunk approach with graft placement and stent-graft extension in the aortic arch and descending aorta. The illustration labeled A to E shows sequential steps of a frozen elephant trunk approach for total aortic arch replacement. Panel A shows an enlarged thoracic aorta before intervention. Panel B shows proximal and distal transection of the aorta, a balloon catheter placed in the left common carotid artery, and a guide wire introduced from the femoral artery and retrieved from the descending thoracic aorta, with a delivery device advanced into position. Panel C shows the endograft deployed within the descending thoracic aorta, the delivery system removed, a collar sutured to the distal aortic remnant, a proximal anastomosis completed at the sinotubular junction, and the brachiocephalic arteries connected. Panel D shows the completed initial repair with branch grafts to the brachiocephalic arteries, with inset views showing an alternate island patch configuration. Panel E shows additional stent-grafts deployed in the descending thoracic aorta, overlapping with the endograft portion of the device. — • Figure 23.19

Hybrid arch techniques.

Volodos is now acknowledged as performing the earliest hybrid arch repair, although this effort was minimally publicized at the time. ^, Hybrid repairs of the aortic arch have become a relatively mainstream clinical practice; this has largely been driven by efforts to reduce the high morbidity and mortality that are traditionally associated with open arch surgery and with the use of HCA. Hybrid approaches are attractive in high-risk patients with little likelihood of surviving an open repair, either because of emergent scenarios (e.g., rupture) or existing comorbidities (e.g., poor cardiac, pulmonary, or renal function). Hybrid repairs involve “debranching” some or all of the brachiocephalic arteries (which is not unlike a Y-graft approach), essentially lengthening the “tube” portion of the distal ascending aorta that is without branching arteries and using an off-label application of available stent-grafts to treat the diseased portion of the aortic arch. The debranching procedure may avoid using CPB (i.e., off-pump), HCA, and the need for median sternotomy, although in practice, repair on CPB (with and without HCA) is not uncommon.

Hybrid arch repairs are typically described as either a Zone 0 or Zone 1 repair, with Zone 0 repair being more extensive ( Fig. 23.20 ). Zone 0 designates a repair that involves the entire aortic arch, essentially rerouting all the brachiocephalic vessels because the stent-graft will cover their origins; the stent-graft lands proximally in the ascending aorta, which may be additionally replaced if it is dilated or to reduce the risk of a stent-graft induced aortic dissection. Zone 1 indicates a more limited repair involving the distal arch. When Zone 1 is designated as the landing zone, both the left common carotid and left subclavian arteries are rerouted because the stent-graft will cover their origins; here, the stent-graft lands just distal to the innominate artery. For saccular aneurysms, hybrid arch repair is particularly attractive because the disease is localized, and healthy aortic tissue is usually readily available for adjacent proximal and distal landing zones. Commonly, such repairs are generally performed in specially designed hybrid operative suites that combine standard cardiothoracic operative equipment with specialty imaging devices. In patients who are undergoing Zone 0 repair, iatrogenic retrograde dissection of the ascending aorta is a potentially lethal complication; thus, meticulous blood pressure management and wire manipulation are recommended to avoid this problem. Patients with an ascending aortic diameter of 4 cm or greater are considered at increased risk of retrograde type A dissection.

An anatomical diagram of a three-stage Zone 0 hybrid arch repair. The anatomical diagram presents three labeled sections of a Zone 0 hybrid arch repair. Panel A shows the aortic arch with a bulging distal arch aneurysm extending into the descending thoracic aorta. Panel B shows the brachiocephalic vessels connected to a Y-shaped graft, with a separate conduit positioned for endovascular deployment. A guide wire and delivery system are shown within the thoracic aorta. Panel C shows the completed repair, with the endograft expanded within the aortic arch and descending thoracic aorta, and the proximal end of the endograft positioned within the labeled landing area. — • Figure 23.20

Later, we describe our Zone 0 hybrid repair. ^, Prior to initiation of repair, a cerebrospinal fluid (CSF) drain is used in patients when repair calls for more than 15 cm of the descending aorta to be covered or will extend below the T8 intercostal artery. Standard preparations for median sternotomy and endovascular repair (described in the section Descending Thoracic Repair: Endovascular) are followed to provide suitable exposure to reroute brachiocephalic vessels and to restore inflow from the ascending aorta (similar to the Y-graft debranching techniques described earlier). Near-infrared spectroscopy aids cerebral monitoring during mobilization of the brachiocephalic arteries during debranching procedures, with the systemic mean aortic pressure kept at 80 to 100 mmHg during reconstruction using a prefabricated or a custom-made Y-graft prepared at the operating table. The main body of the Y-graft is anastomosed to the right anterolateral aspect of the ascending aorta. During reconstruction, we keep the mean arterial pressure low (50–60 mmHg). Debranching is performed distally to proximally by revascularizing the left subclavian artery first (end-to-end anastomosis), followed by the left common carotid and innominate arteries. The mean arterial pressure is kept between 80 and 100 mmHg as these arteries are rerouted. If the left subclavian artery is not accessible through the median sternotomy, a left carotid-to-subclavian bypass or left subclavian-to-carotid transposition is performed via a left supraclavicular incision during the same operation or delayed until after the primary repair is performed. As needed, when the left vertebral artery arises from the arch, it is directly reattached to the side of the Y graft, the left common carotid artery, or the left subclavian artery.

The endovascular coverage of the arch is performed by delivering an endograft either in an antegrade or retrograde fashion, according to preference and the quality of the iliofemoral vessels. Antegrade delivery is performed through a sheath inserted directly into the ascending aorta or via a 10-mm Dacron graft sutured to the main trunk of the debranching graft or directly to the aorta. If the ascending aorta is more than 4 to 4.5 cm in diameter and we believe that the patient can tolerate CPB, we tend to replace the ascending aorta under CPB to minimize the likelihood of inadvertently creating retrograde ascending aortic dissection. Retrograde delivery relies on ultrasound and a micropuncture technique to gain vascular access to the femoral or iliac arteries; as needed, a conduit graft can be sewn to the artery in an end-to-side fashion to deploy the endograft. In arteries without a great deal of calcification and otherwise anatomically suitable, a percutaneous approach that relies on pre-close devices is routinely used. The stent-graft is then advanced into the aorta and suitably positioned. The endograft is ballooned if necessary, and the stent-graft is oversized by 10% to 20%; care is taken to avoid oversizing the endograft. After stent-graft deployment, we protect the spinal cord by increasing the mean arterial pressure to 90 to 100 mmHg.

Descending thoracic aorta repair

Contemporary repair of the descending thoracic aorta may be performed as an open or endovascular procedure. Although traditional open repair was once the preferred approach, endovascular repair of the thoracic aorta (TEVAR) has largely supplanted its use, except in patients with heritable disease, infection, complex anatomy (including a patient with prior repair for aortic coarctation, when complications of prior endovascular repair are present, and other select scenarios). Additionally, one should consider if patients with chronic aortic dissection may be better served by open repair. ^, ^, ^,

Open replacement.

Descending thoracic aortic aneurysms involve the aortic segment between the left subclavian artery and the diaphragm. Open replacement of the descending thoracic aorta has been largely unchanged since the 1950s. For most patients, a clamp-and-sew approach (i.e., without circulatory support or specialized supportive techniques) is sufficient if the repair can be hastened to minimize aortic clamping time ( Fig. 23.21 ). However, in some patients, distal aortic perfusion may be provided using left heart bypass (LHB), which additionally reduces strain on the heart. If the location and severity of aortic disease are such that clamps cannot be safely placed on the aorta (e.g., because of rupture, very large aneurysm size, a need to include the distal arch, or because a prior endovascular repair hinders clamping), then CPB with HCA is used; specific centers may use this approach as their standard because of the well-established benefits of hypothermia to buffer ischemia. ^, In select patients, use of CSF drainage may be appropriate, such as in patients with previous open repair of the descending thoracic, thoracoabdominal, or abdominal aorta (see Chapter 24 ).

An anatomical diagram shows four stages of an open graft replacement procedure for a descending thoracic aneurysm. The anatomical diagram presents four sequential stages of open graft replacement for a descending thoracic aneurysm using a clamp-and-sew approach. Panel A shows the thoracic aorta clamped above the descending portion, with a smaller clamp placed on the branch vessel near the upper arch. Panel B shows a distal cross-clamp applied and the descending thoracic aorta opened longitudinally. Panel C shows sutures placed for the proximal anastomosis with a graft positioned at the upper end of the opened segment and several intercostal arteries ligated. Panel D shows the proximal anastomosis completed, the smaller clamp removed, the main aortic clamp repositioned onto the graft, and the distal anastomosis completed. — • Figure 23.21

We use a double-lumen endobronchial tube for selective ventilation of the right lung and deflation of the left lung to improve exposure, mild permissive hypothermia (32°C-34°C), and moderate systemic heparinization (1.0 mg/kg) to prevent small-vessel thrombosis. The radial arterial catheter is placed in the right radial artery because the left subclavian artery may be interrupted during repair. After standard preparations are completed, the patient is placed in the right lateral decubitus position, with the left hip rotated posteriorly. In general, the resection of a rib is unnecessary. A left posterolateral thoracotomy incision is made, and the pleural space is entered through the top of the bed of the nonresected fifth or sixth rib; in select scenarios, the fourth rib may be entered, such as in a complication of prior coarctation repair. If the aortic disease is limited to the upper portion of the descending thoracic aorta, the chest is entered through the top of the nonresected fifth rib. If the entire descending thoracic aorta is involved, a longer incision is made, curving slightly inferiorly at the anterior portion, and the pleural space is entered through the top of the nonresected sixth rib. Exposure can be enhanced by dividing the sixth rib or the fifth rib posteriorly. If the distal clamp must be placed at or near the diaphragm, a second entrance into the pleural space can be made through the top of the bed of the nonresected eighth rib. Alternatively, the costal margin can be divided. As needed to obtain adequate exposure, crossing the costal margin without entering the abdomen is an option in patients with elongated chests. This will substantially enlarge the single opening into the chest, exposing the entire descending thoracic aorta.

Repair varies according to location and extent of aortic disease. A limited dissection is performed around the aorta just proximal and distal to the diseased segment to permit placement of clamps. If the aortic disease begins at or near the origin of the left subclavian artery, mobilizing the aortic arch between origins of the left common carotid and left subclavian arteries is required. The parietal pleura is incised between the left phrenic and left vagus nerves, and the aorta is isolated circumferentially and separated from the esophagus. The pulmonary artery is juxtaposed to the lesser curvature of the aortic arch; in patients with prior distal ascending or arch surgery, careful dissection is needed to avoid injuring this vessel. The left vagus and left recurrent laryngeal nerves are identified and protected. Access to the more proximal aorta can be improved by opening the pericardium, particularly if an aortic cannula is to be inserted proximal to the clamp site. Appropriate clamps are selected. The segment of aorta that is replaced should be no longer than necessary to avoid sacrificing patent intercostal arteries. In patients with infection, it may be necessary to radically debride the aortic wall and use a larger exposure (using more of a thoracoabdominal incision).

An appropriately sized Dacron graft is chosen, usually between 24 to 28 mm in diameter, which is soaked in rifampin if infection is suspected or soaked in rifampin as a routine prophylactic measure. The proximal aortic clamp is typically placed just distal to the left subclavian artery; when it is placed proximal to this artery, an arterial bulldog clamp is commonly placed across it. When LHB is used, the distal aortic clamp is initially placed as close as possible to the proximal clamp to permit perfusion of as many of the intercostal arteries as possible. In case of a prior ET or frozen ET repair, the proximal clamp is placed on the trunk using epiaortic ultrasonography to guide placement. The aorta is opened between the clamps and is transected proximally. The patent intercostal and bronchial arteries in the aortic segment that will be excluded are ligated with silk suture. The graft is sutured to the proximal aorta with a continuous 3-0 or 4-0 polypropylene suture. If the left subclavian artery is occluded, the proximal aortic clamp is repositioned onto the aortic graft to permit early perfusion of the left subclavian artery. Additionally, the left subclavian artery may contribute to the anterior spinal artery via the vertebral artery. When infection is present, the aortic cross-clamp should be removed slowly, and it may be necessary to bring omentum into the field to cover the graft. After this anastomosis is completed, the distal clamp can be repositioned at a lower level if necessary, and the aorta opened longitudinally. Location and patency of intercostal arteries, particularly those below the seventh intercostal space, are determined. The distal aorta is transected obliquely whenever possible to permit preservation of the lower patent intercostal arteries. The aortic graft is beveled appropriately and sutured to the aorta. If an oblique incision is not possible, the lower intercostal arteries are detached from the aorta with a small, full-thickness cuff of the adjacent aorta using electrocautery. The aortic graft is stretched, and a hole is made in the graft opposite the intercostal artery island, which is sutured to the graft with a continuous 3-0 or 4-0 polypropylene suture. The graft is flushed to remove air by removing the proximal clamp. This clamp is then repositioned below to permit perfusion of the intercostal arteries. The distal aorta is transected at the appropriate level, and if chronic dissection is present, the septum is fenestrated to avoid distal malperfusion. The graft is sutured to the aorta with a continuous 3-0 or 4-0 polypropylene suture. As needed, the anastomoses may be additionally secured using a strip of felt or bovine pericardial pledgets if infection is present. Central and peripheral cannulae are removed, and two intercostal drainage catheters are placed, one posteriorly and inferiorly and one anteriorly, at the apex of the pleural cavity. If infection is suspected, antibiotic beads are placed, tissue is sent for culture, and any suitable residual aortic wall may be placed around the graft to give separation. The incision is closed.

Endovascular repair.

In the contemporary era, endovascular techniques dominate repair of the descending thoracic aorta. Numerous stent grafts are FDA-approved, including devices that incorporate a branch that could be located in the left subclavian artery, and several devices are being developed. ^, Repair depends on having suitable proximal and distal landing zones that are ideally at least 2 centimeters long and comprise healthy tissue. Historically, the proximal landing zone is distal to the left subclavian artery ( Fig. 23.22 A) in Zone 3 or 4, but contemporary approaches often push that landing zone into Zone 2, which necessitates covering the left subclavian artery bypass and should prompt carotid-to-left subclavian bypass in advance of surgery ( Fig. 23.22 B-C) to maintain vertebral artery blood flow and minimize neurologic injury. Additionally, conformable devices may be useful when repair approaches the distal arch. Distally, the celiac axis tends to serve as the lower boundary of repair, and its coverage remains controversial; large diameter “bare” stents may be used to cover the celiac axis, which is useful in patients with chronic aortic dissection to aid remodeling. For optimal outcomes, the proximal and distal neck diameters should fall within a range that will allow a secure seal. Tortuosity of the aorta and access vessels can make these procedures technically challenging. Successful deployment of current endovascular devices depends on good vascular access—the femoral and iliac arteries have to be sufficiently large to accommodate the sheaths that are used to deploy the stent-grafts. Newer devices aim to use smaller sheaths or “sheathless” (self-deployed stent-grafts) technology to accommodate smaller arteries. Occasionally, an 8- or 10-mm polyester graft conduit is anastomosed end-to-side to the iliac artery through a retroperitoneal incision if the femoral vessels are too small to appropriately access. When chronic dissection is present, care must be taken to land the stent-graft inside the true lumen to avoid malperfusion and to aid any subsequent repair that may be needed in the future.

An anatomical diagram shows three sections of thoracic endovascular aortic repair using different landing zones and a bypass graft. The anatomical diagram presents three sections labeled A, B, and C illustrating thoracic endovascular aortic repair. Panel A shows a stent-graft within the thoracic aorta extending into the descending portion, with the proximal edge landing in Zone 3 and not covering the left subclavian artery. Panel B shows a bypass graft connecting the left subclavian artery to the left common carotid artery prior to stent deployment. Panel C shows a stent-graft positioned with its proximal edge landing in Zone 2, covering the origin of the left subclavian artery, while the bypass graft remains in place above the arch. — • Figure 23.22

Prior to initiation of repair, a CSF drain is typically placed in patients considered at greater risk, such as patients with prior distal aortic repair, and in those patients whose CTA or MRA imaging identifies large intercostal arteries within the lower descending aorta. Most patients do not need a CSF drain and can be evaluated in the OR upon wakening, with rescue measures initiated as needed. Intravascular ultrasound and aortography are commonly used during repair. After standard preparations are completed, the patient is placed in the supine position with general endotracheal anesthesia. Appropriate vascular access for stent-graft deployment is obtained. Ultrasound and a micro-puncture technique are common, followed by vascular devices to assist in percutaneous closure. If the femoral artery does not accommodate the sheath, then an iliac artery is exposed. As needed, a conduit graft can be sewn to the artery in an end-to-side fashion to ease deployment of the endograft. Moderate heparin (5000 to 10,000 units) is administered, and under fluoroscopic guidance (aortography), a guidewire and the delivery sheath are commonly inserted into the access artery. The stent-graft is then advanced into the aorta and suitably positioned. A left anterior oblique position (at an angle of approximately 40 to 60 degrees) typically gives the best view of the distal arch and descending thoracic aorta. The endograft is then deployed, and to better appose the proximal and distal ends to the aortic wall, they can be reshaped by manipulating a balloon catheter. It is important to keep the mean arterial pressure within a narrow range (typically between 90 and 110 mmHg) after the endograph is deployed. An aortogram is then performed to rule out any endoleak, and protamine is administered to neutralize heparin. In patients with substantial renal disease, IVUS can be used as an alternative to aortography to identify the proximal and distal landing zones, allowing the entire procedure to be performed with minimal or no contrast. IVUS is particularly useful in aortic dissection to identify the true and false lumen.

Thoracoabdominal aorta replacement

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Tags: Joseph S. Coselli, Kirklin/Barratt-Boyes Cardiac Surgery

Apr 21, 2026 | Posted by drzezo in CARDIAC SURGERY | Comments Off

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