Left subclavian artery revascularization: Society for Vascular Surgery Practice Guidelines

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1 Left subclavian artery revascularization: Society for Vascular Surgery Practice Guidelines Jon S. Matsumura, MD, and Adnan Z. Rizvi, MD, Madison, Wisc; and Minneapolis, Minn From the Division of Vascular Surgery, University of Wisconsin School of Medicine and Public Health, Madison; and the Department of Vascular and Endovascular Surgery, Minneapolis Heart Institute at Abbott Northwestern Hospital, Minneapolis. Competition of interest: Dr Matsumura has received funding for research from Abbott Vascular, W.L. Gore, Covidien, and Cook. Correspondence: Jon S. Matsumura, MD, Division of Vascular Surgery, University of Wisconsin School of Medicine and Public Health, G5/325 Clinical Science Center, 600 Highland Ave, Madison, WI ( The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a competition of interest. J Vasc Surg 2010;52:65S-70S /$36.00 Copyright 2010 by the Society for Vascular Surgery. doi: /j.jvs The use of thoracic stent grafts to manage patients with various aortic pathologies is a rapidly expanding area in the field of vascular surgery. It has supplanted traditional open surgery in the treatment of many specific aortic diseases, including descending thoracic aneurysms, acute complicated dissection, traumatic transection, and penetrating ulcers. Because of the need for an adequate proximal seal zone and limitations of current technology of stent grafts, the left subclavian artery (LSA) may need to be covered in 26% to 40% of patients undergoing thoracic endovascular aortic repair (TEVAR). 1,2 In the first United States regulatory trial, 3 all patients were required to undergo prophylactic LSA revascularization before TEVAR if the LSA was covered, but this practice has not become predominant in clinical practice. There is great variability amongst surgeons and interventionalists about which patient undergoes LSA revascularization before TEVAR. Some surgeons perform routine LSA revascularization, whereas others are selective, such as in cases of a left vertebral artery ending at the posterior inferior cerebellar artery, a prior left internal mammary-to-coronary artery bypass, or an absent distal right vertebral artery. Lastly, some surgeons only perform LSA revascularization if symptoms of left arm ischemia or subclavian steal syndrome occur after TEVAR. 1,4,5 Unfortunately, most of the data about LSA coverage during TEVAR and the morbidity and mortality associated with this come from single institutional series or registries, thus the current management of the LSA when coverage is necessary is not uniform. The Society for Vascular Surgery (SVS) recently formed a Committee on Aortic Disease to formulate clinical practice guidelines to aid physicians and patients regarding LSA revascularization during TEVAR. A third-party, the Knowledge and Encounter Research Unit, Mayo Clinic, Rochester, performed a comprehensive literature review and formulated a systematic review and meta-analysis relating the effect of LSA coverage on the morbidity and mortality of patients undergoing TEVAR. 6 The SVS used this review and the consensus of the committee to develop three recommendations regarding LSA revascularization in relationship to TEVAR. 7 This article reviews the potential complications associated with LSA coverage and summarizes the SVS Practice Guidelines in the management of the LSA during TEVAR. COMPLICATIONS ASSOCIATED WITH LSA COVERAGE DURING TEVAR The LSA provides blood flow to the left arm but also provides important additional perfusion pathways to the brain by the left vertebral artery and spinal cord through the left vertebral artery, internal thoracic artery, subscapular artery, and lateral thoracic artery. These LSA collaterals are important during TEVAR, and their disruption can cause significant morbidity and death. Complications associated with coverage of the LSA during TEVAR include stroke, spinal cord ischemia, and left upper extremity ischemia. Stroke. The incidence of stroke after TEVAR ranges from 3.8% to 6.3%. 8 The etiology is multifactorial and is likely related to patient and procedural variables, including: 1. patient age and underlying cerebral vascular disease; 2. periprocedural hypotension or hypertension; 3. etiology of the treated aortic pathology and proximal extent of the disease; 4. embolization of air or atheromatous debris during device manipulation or deployment; and 5. coverage of important vessels with the device for disease involving the arch vessels. Most anterior circulation strokes are likely embolic, whereas posterior circulation strokes tend to be ischemic in origin. Studies have shown that 60% of patients have a dominant left vertebral artery, with the contralateral vertebral either atretic or absent; thus, unknowingly covering the LSA artery in an individual with this anatomic variant has risk. Some studies have demonstrated a higher overall stroke rate (13% vs 2%) and posterior circulation stroke rate (5.5% vs 1.2%) with intentional coverage of the LSA compared with LSA revascularization. 2,5 A recent study by Holt et al 9 specifically analyzing their institution s results of treating aortic arch aneurysms (proximal landing zone 0, 9; zone 1, 17; zone 2, 52) with a hybrid approach further enlightens us on the importance of the LSA. The incidence of stroke was 0% in 35 patients who underwent LSA artery revascularization compared with 65S

2 66S Matsumura and Rizvi JOURNAL OF VASCULAR SURGERY October Supplement 2010 Fig 1. Arm ischemia: random-effects meta-analysis. The squares are odds ratios of individual studies, the lines are 95% confidence intervals (CI), the diamond represents the pooled effect, and the width of the diamond is the 95% CI of the pooled estimate. 11.6% in the 43 patients who had intentional LSA coverage (P.046). The combined stroke-paraplegia-death rate comparing the two cohorts was striking: 0% vs 27.9% (P.001). This was not a randomized trial and used historic controls and may be limited by confounding improvements that also occurred at St. George s Vascular Institute, a high-volume institution. Nevertheless, a thorough preoperative understanding of the anatomy of the arch and cerebral anatomy, routine LSA revascularization, and careful manipulation of wires, catheters, and device during stent graft deployment are crucial in minimizing the incidence of stroke during TEVAR. Spinal cord ischemia. The anterior spinal artery is an important vessel for supplying blood to the motor horns of the spinal cord. It receives inflow from branches off the vertebral artery as well as from intercostal and lumbar arteries off the thoracoabdominal aorta. As with stroke, the etiology of spinal cord ischemia after TEVAR is multifactorial. (See the article by Drs Rizvi and Sullivan for a detailed review of spinal cord protection.) Potential contributors to spinal cord ischemia include: 1. periprocedural hypotension; 2. embolization to the intercostal artery; 3. intraspinal hematoma; and 4. lack of adequate perfusion to the anterior spinal artery after coverage of important collaterals, including the intercostal, lumbar, middle sacral, hypogastric, or subclavian arteries. A few recent studies have alluded to the importance of patency of the LSA in reducing the risk of spinal cord ischemia. A review of the European Collaborators on Stent-Graft Techniques for Aortic Aneurysm Repair (EUROSTAR) registry found LSA coverage without revascularization resulted in a 8.4% incidence of spinal cord ischemia or stroke compared with 0% in patients with LSA revascularization (P.049). 1 Left upper extremity ischemia. Upper extremity ischemia is uncommon after acute occlusion of the LSA for TEVAR and is generally tolerated, but symptoms can range from minimal to an acutely ischemic hand. In addition, flow reversal in the left vertebral artery occurs after covering the LSA. Most patients are asymptomatic; however, in certain cases a true steal phenomenon can occur, with resultant symptoms from vertebrobasilar insufficiency of syncope, diplopia, or vertigo. A recent series reported upper extremity ischemia occurred 12% to 20% of the time after LSA coverage; however, 40% of patients with symptoms of arm ischemia underwent delayed LSA revascularization. 10,11 In regards to onset of symptoms, an immediately threatened arm is exceedingly rare, and presentation of ischemic symptoms of the arm is often delayed (range, 2 day-26 months) after TEVAR. 10,11 The delayed presentation of upper extremity ischemia or vertebrobasilar insufficiency means revascularization for these risks can typically be addressed on a less urgent basis. EVIDENCE The systematic review and meta-analysis from the Knowledge and Encounter Research Unit, Mayo Clinic, Rochester, showed that coverage of the LSA without revascularization was associated with a trend toward an increased risk of paraplegia (odds ratio [OR], 2.69; 95% confidence interval [CI], ) and anterior circulation stroke (OR, 2.58; 95% CI, ), and a much higher risk for arm ischemia (OR, 47.7; 95% CI, ) and vertebrobasilar ischemia (OR, 10.8; 95% CI, ) compared

3 JOURNAL OF VASCULAR SURGERY Volume 52, Number 13S Matsumura and Rizvi 67S Fig 2. Vertebrobasilar ischemia: random-effects meta-analysis. The squares are odds ratios of individual studies, the lines are 95% confidence intervals (CI), the diamond represents the pooled effect, and the width of the diamond is the 95% CI of the pooled estimate. Fig 3. Spinal cord ischemia: random-effects meta-analysis. The squares are odds ratios of individual studies, the lines are 95% confidence intervals (CI), the diamond represents the pooled effect, and the width of the diamond is the 95% CI of the pooled estimate. with patients who underwent preoperative LSA revascularization 6 (Figs 1 to 4). A literature review of patients who underwent LSA revascularization showed the overall incidence of phrenic nerve injury was 4.4% (95% CI, 1.6% %). Coverage of the LSA without revascularization was not associated with an increased risk of death, myocardial infarction, or transient ischemic attack. RECOMMENDATIONS OF THE SVS The Committee reviewed the available data and used the Grading of Recommendation Assessment, Development and Evaluation (GRADE) method, 12 as well as group consensus, to determine its recommendations (Table). The SVS was aware of the limitations of the systematic review, acknowledging that the studies reviewed were observational in nature, the patients in the studies were heterogenous in diagnosis, morbidity, and aortic pathology, the data of interest (stroke, death, spinal cord ischemia) occurred infrequently, and reported data were not consistent or uniform. Despite the low-quality evidence on which to base their recommendations, the Committee understood that neurologic complications (stroke and paraplegia) associated with TEVAR are clinically important, and a high value was placed on avoiding these complications when the guidelines were developed. The SVS guideline recommendations, based on a systematic review and meta-analysis of the literature, are as follows: Recommendation 1: For elective TEVAR where coverage of the LSA is necessary for adequate stent graft seal,

4 68S Matsumura and Rizvi JOURNAL OF VASCULAR SURGERY October Supplement 2010 Fig 4. Anterior circulation stroke: random-effects meta-analysis. The squares are odds ratios of individual studies, the lines are 95% confidence intervals (CI), the diamond represents the pooled effect, and the width of the diamond is the 95% CI of the pooled estimate. Table. Recommendations according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system 12 The GRADE system categorizes recommendations as strong (GRADE 1) denoted by the phrase we recommend, or weak (GRADE 2) denoted by the phrase we suggest. The quality of evidence is graded as high-quality (level A), typically derived from well conducted randomized trials, moderate-quality (level B), typically derived from less rigorous or inconsistent randomized trials, low-quality or very-low quality (level C), derived from observational studies, case series, and unsystematic observations or expert opinion. the SVS suggests routine preoperative revascularization. (Very low-quality evidence, GRADE 2, level C). Recommendation 2: For patients where the anatomy to be treated comprises perfusion to vital organs, the SVS strongly recommends routine preoperative LSA revascularization. (Very low-quality evidence, GRADE 1, level C). Consensus-ranked examples of these circumstances include: Presence of a patent left internal mammary to coronary artery bypass graft Termination of the left vertebral artery into the posterior inferior cerebellar artery Absent, atretic, or occluded right vertebral artery Patent left arm arteriovenous shunt for dialysis Prior infrarenal aortic operation with previously ligated lumbar and middle sacral arteries Planned extensive ( 20-cm) coverage of the descending thoracic aorta Hypogastric artery occlusion Presence of early aneurysmal disease where future therapy involving the distal thoracic aorta may be necessary Recommendation 3: For patients with acute thoracic emergencies where TEVAR is required more urgently and coverage of the LSA will be necessary, the SVS suggests that revascularization should be individualized and addressed according to the patient s anatomy, urgency of the procedure, and availability of surgical expertise for LSA revascularization (GRADE 2, level C). LSA REVASCULARIZATION In the past, LSA revascularization with a carotidsubclavian bypass or transposition was performed typically for atherosclerotic occlusive disease. With the advent of TEVAR, this operation has become much more common for surgeons. Although not completely benign, LSA revascularization, especially in the setting of TEVAR, has a very low associated morbidity and mortality. The recent systematic review reported the overall incidence of phrenic nerve injury was low, at 4.4%. 6 The University of Pennsylvania group recently reviewed their experience of LSA revascularization in patients undergoing TEVAR. In their series, 42 of 70 patients (60%) required LSA revascularization (5 transpositions, 37 bypasses), and the only complication was a patient (2.4%) with phrenic nerve palsy. Similarly, Peterson et al 5 reported their experience of 23 patients who underwent LSA revascularization, comprising 21 transpositions and 2 bypasses, before TEVAR. Vocal paralysis developed in two patients (8.7%) related to the operation, of which one resolved spontaneously. A systematic review of the literature by Cina et al 13 evaluated carotid-subclavian bypasses or transpositions reported between 1996 and The reported patency at a mean of 59 months was superior with subclavian-carotid transposition

5 JOURNAL OF VASCULAR SURGERY Volume 52, Number 13S Matsumura and Rizvi 69S (98%) vs carotid-subclavian bypass (84%). Of note, however, is that most of the operations in this systematic review were for occlusive disease rather than for LSA revascularization before TEVAR. A more in depth discussion of debranching of all three arch vessels is covered in the article by Drs Vallabhaneni and Sanchez. Finally, numerous case reports have been published on various techniques for percutaneous management of the arch vessels when planned coverage is anticipated (See the article by Drs Longo and Pipinos). Although premade fenestrated stent grafts have been well described, they have limited availability to practicing clinicians 14 (See the article by Drs Greenberg and Qureshi). Additional techniques to percutaneously manage planned LSA coverage with stent grafts include the double-barrel or chimney technique. Typically with this technique, a covered stent is positioned from a retrograde left brachial approach and deployed in a kissing fashion, traversing the origin of the LSA when the thoracic stent graft is deployed. The thoracic stent graft forms a seal around the LSA stent, maintaining antegrade flow. In the short-term, the reported cases demonstrate 100% patency and no type I endoleak. 15,16 Equally novel is in situ fenestration for TEVAR involving the arch vessels, which is detailed in the article by Drs Longo and Pipinos. Various techniques have been described using a retrograde approach to create an in situ fenestration in the stent graft fabric. The final step is placing a covered stent to bridge the hole in the stent graft to the target vessel being treated Although in their infancy, and without any data on durability and effect on graft structural integrity, these may be novel endovascular techniques to maintain antegrade flow in the arch vessels and obviate the need for surgical debranching procedures. CONCLUSIONS The Society for Vascular Surgery Practice Guidelines suggest routine preoperative revascularization when the left subclavian artery is covered during TEVAR and provide a stronger recommend for routine revascularization in circumstances where collateral perfusion may be compromised. Exceptions include emergent TEVAR and when other circumstances preclude preoperative LSA revascularization. These guidelines are based on the analysis of 51 eligible studies by the Mayo Clinic Knowledge and Encounter Research Unit, which found risk increases of 48- fold for arm ischemia, 11-fold for vertebrobasilar ischemia, 2.7-fold for spinal cord ischemia, and 2.6-fold for anterior circulation stroke when the LSA was covered without revascularization during TEVAR compared with revascularization. However, the latter two risk increases are not statistically significant, and the quality of evidence is very low. Taken together with other emerging data, understanding the detailed anatomy, and considering the devastating nature of neurologic complications, it seems prudent to preserve antegrade flow in the left subclavian artery. AUTHOR CONTRIBUTIONS Conception and design: JS, AR Analysis and interpretation: JS, AR Data collection: JS, AR Writing the article: JS, AR Critical revision of the article: JS, AR Final approval of the article: JS, AR Statistical analysis: JS, AR Obtained funding: Not applicable Overall responsibility: JS REFERENCES 1. Buth J, Harris PL, Hobo R, van Eps R, Cuypers P, Duijm L, et al. Neurologic complications associated with endovascular repair of thoracic aortic pathology: Incidence and risk factors. a study from the European Collaborators on Stent/Graft Techniques for Aortic Aneurysm Repair (EUROSTAR) registry. J Vasc Surg 2007;46: ; discussion Feezor RJ, Martin TD, Hess PJ, Klodell CT, Beaver TM, Huber TS, et al. Risk factors for perioperative stroke during thoracic endovascular aortic repairs (TEVAR). J Endovasc Ther 2007;14: Makaroun MS, Dillavou ED, Kee ST, Sicard G, Chaikof E, Bavaria J, et al. 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