John Denesopolis, Patricia Yau, and Aksim G. Rivera Department of Surgery (Vascular Surgery), Albert Einstein College of Medicine-Jacobi Medical Center, Bronx, NY, USA Thoracic aortic pathology has increasingly become a major cause of mortality in the United States, accounting for at least 13 000 deaths annually, with incidence 5.6–10.4 cases per 100 000 people. Thoracic aortic aneurysm (TAA) is predominantly a disease of the older people, with risk factors similar to that of patients with abdominal aortic aneurysm (AAA), i.e. smoking, hypertension, and atherosclerotic disease. The majority are degenerative in etiology, though approximately 20% are sequelae of chronic aortic dissection. Most diagnosed thoracic aortic and thoracoabdominal aortic aneurysms (TAAA) are not symptomatic, and are incidentally noted on imaging obtained for unrelated reasons [1]. The use of endovascular stent grafting, first popularized for AAAs, has now become a mainstay of treatment for TAA. Thoracic endovascular aortic repair (TEVAR) has been shown to have clear benefit in morbidity and mortality to open repair in more recent literature. In patients with less‐than‐ideal anatomy, e.g. involvement of major aortic branches, tortuous anatomy, large diameter neck, etc., the advantage of endovascular repair over open repair becomes less pronounced. However, with more sophisticated technology, as well as the advent of fenestrated, branching, and hybrid techniques, the use of TEVAR in patients with complex aortic pathology has proven to be safe, effective, and durable. Additionally, the indications for use of TEVAR have expanded to include blunt traumatic aortic injury, aortic dissection, and acute aortic syndromes. The thoracic aorta consists of four main parts: the aortic root, the ascending thoracic aorta, the aortic arch, and the descending thoracic aorta. The aorta normally enlarges as it progresses distally, and moves posterolaterally in the proximal portion, and anteromedially closer to the diaphragm. Aneurysmal dilatation is defined as 1.5 × normal diameter; normal diameter for the descending aorta is 2.0–2.3 cm. Aneurysm morphology is characterized as fusiform or saccular, with saccular aneurysms having a higher risk of rupture. Figure 4.1 Aortic landing ones. Preoperative planning for TEVAR requires consideration of proximal and distal landing zones and the potential for coverage of major aortic branches. At least 20 mm of proximal and distal landing zone is recommended to allow adequate seal. If there is significant tortuosity, a longer sealing zone may be desired. Consideration of aortoiliac anatomy is important for determining arterial access and potential need for iliac conduit for graft delivery. The right iliac artery is the preferred route of graft delivery. The access vessel should be at least 7 mm in diameter. If there is not an adequately sized vessel, or if there is significant atherosclerotic disease, an iliac conduit may be required for device delivery. In rare cases where the entire iliac system is diseased, direct aortic access or an iliac endoconduit may be used (described below). Spinal cord ischemia is a particularly devastating complication that may occur in 3–7% of patients following TEVAR. Rates of spinal cord ischemia have remained the same despite increasing use of endovascular repair. The blood supply to the spinal cord consists of the posterior spinal arteries (arising from the vertebral or posterior inferior cerebellar arteries), anterior spinal artery (originates from the vertebral arteries), and supported by the artery of Adamkiewicz (usually takes off between T8 and L2). This network is reinforced by collaterals from the radicular arteries, which are supplied by inflow vessels: subclavian/vertebrals, thyrocervical and costocervical trunks, intercostals, lumbar arteries, and branches of hypogastric. Thus, the risk of spinal cord ischemia is increased with coverage of the left SCA and coverage of the hypogastric. Increased length of aortic coverage, renal insufficiency, prior abdominal aortic repair, and intraoperative hypotension are other risk factors for spinal cord ischemia. Coverage of the left SCA also significantly increases the risk of stroke, particularly in 60% of patients with a dominant left vertebral artery. Revascularization of the left SCA, usually by carotid to subclavian bypass, is mandatory in these patients if the left SCA is covered. If surgical reconstruction is contraindicated and left SCA coverage is anticipated, preoperative evaluation should include imaging to assess patency of the right vertebral artery and continuity of the circle of Willis. The goal of surgical intervention for asymptomatic TAA/TAAA is the prevention of rupture. The most important risk factors for rupture for TAAs are size, rate of expansion, and saccular morphology. Current criteria for elective repair of asymptomatic TAA are maximum diameter >5.5 or growth >5 mm over six months [2]. TEVAR has largely replaced open repair as first‐line surgical management for BAI. Traditionally, the goal has been for definitive surgical repair as early as possible; however, recent data has shown decreased risk of mortality in delayed (>24 hours) repair. Type B aortic dissection (TBAD): First‐line treatment for uncomplicated TBAD continues to be medical management with tight blood pressure control. However, TBAD with malperfusion may be treated with TEVAR with the goal of sealing the proximal tear and allowing reexpansion of the true lumen [3, 4]. Between 40 and 60% of TBAD which are treated with medical management undergo aneurysmal degeneration of the false lumen, requiring surgical intervention. There may be a role for elective TEVAR in the subacute period. The INSTEAD trial investigated treatment of subacute TBAD, comparing those treated with endograft and medical management. The data revealed that there was no difference in all cause mortality or aortic‐related mortality between the two groups, and the risk of the combined secondary outcome of rupture and progression of disease was the same. Penetrating aortic ulcer (PAU) and Intramural hemorrhage (IMH): PAU and intramural hematoma are two entities that are separate from TBAD but may present with similar symptoms of acute chest/back pain associated with hypertension. Some believe that the three entities are on the same spectrum of disease; however, the natural progression between the three pathologies is unknown. A PAU, as the name implies, is an atherosclerotic ulcer on the aortic wall that erodes into the aortic wall, whereas an intramural hematoma is a collection of blood between the intima and the media. The natural history of these pathologies is not as well understood as dissection, and thus the indications for and timing of surgical intervention are still under investigation. In patients with ideal anatomy, TEVAR seems to be the preferred option for most cases, with current literature demonstrating reduced morbidity and mortality. However, data regarding long‐term (lifelong) follow‐up for TEVAR patients is scarce. In younger, healthier patients with a longer life expectancy, consideration can be made for open repair. As stated previously, the presence of challenging anatomy, such as involvement of major aortic branches, large diameter neck, significant angulation, or circumferential thrombus within the seal zones, may make endovascular repair more difficult. In these cases, a careful risk–benefit assessment must be made, taking into account patient comorbidities and surgeon experience. Endovascular stent grafting for infected TAA is not recommended, but can be considered for patients who are poor surgical candidates. Figure 4.2 Cook Zenith Alpha Graft.
4
Endovascular Repair of Thoracic Aortic Aneurysms: Catheter‐Based Therapy
Introduction
Relevant Anatomy
Aortic Anatomy
Crawford Classification for TAA/TAAA
Landing Zones (Figure 4.1)
Implication of Aortic Anatomy on Spinal Perfusion
Indications/Contraindications to Procedure
Indications
Asymptomatic TAA/TAAA
Blunt Aortic Injury (BAI)
Acute Aortic Syndromes
Contraindications/Caveats
Available Endografts
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
