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Upper Extremity Aneurysms
Upper extremity aneurysms are uncommon relative to other peripheral arterial aneurysms. Arch vessel aneurysms, the most frequent type of upper extremity aneurysm, can lead to life-threatening exsanguination as a result of rupture, as well as numerous other complications, including stroke, local nerve compression (leading to hoarseness or brachial plexus palsy), dysphagia from esophageal compression in cases of an aberrant right subclavian artery (ARSA) aneurysm, localized pain, or limb ischemia. More distally located upper extremity aneurysms are manifested primarily by thromboembolic complications of the hand and digits.
The earliest reported attempts at surgical correction of arch vessel aneurysms were common carotid aneurysm ligations by Astley Cooper in 1805 and 1808, followed by ligation of the innominate artery by Valentine Mott in 1818 for the treatment of a subclavian artery aneurysm. Mott’s patient expired within 1 month as a result of hemorrhage from the necrotic aneurysm. The first successful treatment of a subclavian artery aneurysm was achieved in 1864 by Smyth in New Orleans, who ligated the right common carotid and innominate artery. The aneurysm recurred and ruptured 10 years later. Halsted was the first to combine successful ligation with resection of a subclavian artery aneurysm in 1892 at the Johns Hopkins Hospital. In 1913 Matas reported 225 cases of aneurysms treated by endoaneurysmorrhaphy, and seven of these were subclavian aneurysms.
Arch Vessel Aneurysms
Epidemiology and Etiology
Innominate, common carotid, and subclavian artery aneurysms usually arise from degenerative disease. In a series of 74 patients with arch vessel aneurysms, Cury et al. reported that 63% were degenerative in nature and the vast majority were detected in men older than 60 years. Less commonly, these aneurysms can also result from trauma, fibromuscular dysplasia, syphilis, cystic medial necrosis, vasculitis, invasion of the vessel wall by contiguous tuberculous lymphadenitis, and idiopathic congenital causes. Although only 1% of all peripheral arterial aneurysms involve the subclavian and innominate arteries, the majority of patients with nonspecific, degenerative arch vessel aneurysms have aortoiliac or other peripheral aneurysms. , In their review of arch vessel aneurysms in 105 patients at Yale, Brownstein et al. found that 74% had multiple aneurysms with the majority involving the ascending and descending thoracic aorta. Patients presenting with these aneurysms should therefore be evaluated thoroughly for concurrent aneurysms.
Aneurysms of the distal subclavian artery, frequently with extension into the first portion of the axillary artery, are usually associated with a thoracic outlet obstruction, cervical rib, and other bony abnormalities that result in arterial compression and poststenotic dilation. This specific type of aneurysm is discussed in Chapter 125 , Thoracic Outlet Syndrome: Arterial.
Subclavian Artery Aneurysms
True subclavian aneurysms, typically seen in older adult patients, are usually degenerative and are the most common type of arch vessel aneurysm, accounting for up to 50% of the cases in most reported series. , , Pairolero et al. reported the treatment of 31 patients with subclavian artery aneurysms treated over a 20-year period. True degenerative aneurysms were repaired in 12 patients, traumatic pseudoaneurysm in 10, and aneurysms secondary to thoracic outlet obstruction in 6. McCollum et al. also reported their 25-year experience with subclavian artery aneurysm repairs, which included 15 patients, more than half of whom had true degenerative aneurysms. More recently, however, Davidovic et al. reported their experience in treating 25 patients with subclavian artery aneurysm over a 12-year period with thoracic outlet obstruction as the etiology in 72% of cases. Pseudoaneurysms of the subclavian artery frequently occur as a result of blunt and penetrating trauma. Iatrogenic injury from inadvertent cannulation of the subclavian artery and subsequent pseudoaneurysm formation is uncommon but increasing in frequency due to subclavian vein catheterization attempts for various indications. , Although many small-caliber (<7 F) misplaced catheters can be removed and simple compression applied, removal of larger catheters, such as those used for hemodialysis, can lead to significant hemorrhage or pseudoaneurysm formation because of an inability to compress the puncture site beneath the clavicle. Recent reports have described the successful use of endovascular techniques to repair arterial injuries occurring during central venous access using endografts or percutaneous closure devices. ,
Innominate Artery Aneurysms
In their review of the natural history of 147 arch vessel aneurysms, Brownstein et al. found that 43% of true arch aneurysms involved the innominate artery. For their review, they defined an innominate artery diameter greater than 1.8 cm as an aneurysm. Most operative series, however, demonstrate that aneurysms of the innominate artery represent only 2% to 5% of cases of arch vessel aneurysms undergoing repair with the majority of these aneurysms being larger than 3 cm. Bower et al. reported their 40-year experience, which included only four patients with true aneurysms of the innominate artery among 73 patients treated surgically for brachiocephalic aneurysms. Similarly, in the series reported by Cury et al., 2 out of 74 surgically treated supra-aortic aneurysms were of the innominate artery. The largest series of innominate aneurysm repair is by Kieffer et al., in which they found six degenerative aneurysms among 27 patients with innominate artery aneurysms. Other etiologies included mycotic, dissecting, and connective tissue disorders, extension of arch aneurysms, and traumatic and iatrogenic pseudoaneurysms.
Common Carotid Artery Aneurysms
True aneurysms of the common carotid arteries are very rare. In fact, pseudoaneurysms of the carotid arteries are considerably more frequent and usually result from complications of carotid reconstructions, blunt or penetrating trauma, carotid dissections, or infection. , The vast majority of the true aneurysms of the carotid arteries are degenerative; other less frequent causes include fibromuscular dysplasia, Marfan syndrome, Behçet disease, and Takayasu arteritis. , Bilateral common carotid artery aneurysms are extremely unusual, generally associated with Takayasu arteritis or Cogan syndrome. , Carotid bifurcation and internal carotid artery aneurysms are discussed in Chapter 97 , Carotid Artery Aneurysms.
Clinical Presentation
Symptoms
Given the prevalence of imaging in modern medical practice, most arch vessel aneurysms are discovered incidentally and only 25% demonstrate symptoms at the time of diagnosis. Presenting symptoms include: (1) chest, neck, and shoulder pain from acute expansion or rupture; (2) upper extremity acute and chronic ischemic symptoms from thromboembolism; (3) upper extremity pain and neurologic dysfunction from brachial plexus compression; (4) hoarseness from compression of the right recurrent laryngeal nerve; (5) respiratory insufficiency from tracheal compression; (6) transient ischemic attacks and stroke from thromboembolism in the vertebral and carotid circulations; (7) dysphagia from esophageal compression in cases of aberrant right subclavian artery; and (8) hemoptysis from erosion into the apex of the lung. Tracheobronchial or esophageal fistulization from contiguous arch vessel aneurysms can also occur. In the case of iatrogenic pseudoaneurysms, clinical presentation includes a pulsatile mass, airway or nerve compression, chest pain, upper limb ischemia, or hemodynamic instability.
Signs
Patients without symptoms may be diagnosed through imaging studies for unrelated conditions ( Fig. 86.1 ). In cases of subclavian artery aneurysms, patients may note the presence of a supraclavicular pulsatile mass. However, most asymptomatic pulsatile masses in this area represent tortuous and elongated common carotid and subclavian arteries and not necessarily aneurysmal degeneration. Other physical signs may include: (1) a supraclavicular bruit; (2) absent or diminished pulses in the upper extremity; (3) normal pulses with signs of microembolization (“blue finger” syndrome); (4) sensory and motor signs of brachial plexus compression; (5) vocal cord paralysis; and (6) Horner syndrome resulting from compression of the stellate ganglion and other contributions to the cervical sympathetic chain at the base of the neck.
Imaging
Plain films of the chest may reveal a superior mediastinal mass that may suggest the presence of a neoplasm. Ultrasonography, MR, or CT imaging establishes the diagnosis. Conventional arch and upper extremity angiography, or MR or CT angiography (CTA) are important to delineate the extent of the aneurysm, to assess the sites of vascular occlusion in cases complicated by thromboembolism, to note the patency of the contralateral vertebral circulation if the ipsilateral vertebral artery originates from an aneurysmal vessel, and to assess anatomic suitability for endovascular repair. These points are essential in planning appropriate management (i.e., surgical reconstruction or endovascular repair).
Open Surgical Repair
Contemporary surgical repair of arch vessel aneurysms involves resection or endoaneurysmorrhaphy and reestablishment of arterial continuity with an end-to-end anastomosis (for very small aneurysms) or, more commonly, an interposition arterial prosthetic graft or femoral vein graft. , Although proximal and distal ligation of arch vessel aneurysms occasionally has been successful in the past, ligation without direct or extra-anatomic reconstruction generally should not be performed because ischemic symptoms develop in 25% of cases so treated.
Innominate Artery Aneurysms
An anatomic classification of the extent of the aneurysm has been proposed by Kieffer et al. to guide the surgical repair of aneurysms of the innominate artery ( Fig. 86.2 ). Type A is confined to the innominate artery distal to its origin. Type B is the most common and involves the innominate artery and its origin, whereas type C involves both the innominate artery and the ascending aorta. The innominate and proximal right subclavian arteries are usually exposed through a median sternotomy extended into the right neck along the medial edge of the sternocleidomastoid muscle. Proximal control of the innominate is obtained at the aortic arch. The right subclavian and right common carotid arteries are exposed and dissected for distal control. The aneurysm is resected, and reconstruction with a prosthetic graft is usually performed. For type A and B aneurysms, the proximal graft anastomosis is usually performed to the native ascending aorta proximal to the innominate origin. The graft is then anastomosed to the uninvolved distal innominate artery ( Fig. 86.3 ). The origin of the innominate artery is oversewn with a running suture, or patch angioplasty of the aorta may occasionally be required. For lesions extending into the origins of the right subclavian or common carotid artery, a bifurcated graft can be used, or a branch graft to the subclavian artery can be sewn onto the graft going into the common carotid artery. The bifurcated configuration may sometimes be prone to compression or kinking when the sternum is closed, so caution should be taken to perform the proximal anastomosis in the lateral aspect of the ascending aorta. In cases of a bovine arch, additional graft reconstruction of the left common carotid artery may be necessary. Type C innominate artery aneurysms usually require aortic arch and innominate artery prosthetic graft replacement using cardiopulmonary bypass and hypothermic circulatory arrest.
Subclavian Artery Aneurysms
Subclavian artery aneurysms can be divided into proximal, typically degenerative, or distal, usually related to thoracic outlet syndrome. For proximal right subclavian aneurysms, median sternotomy with extension into the supraclavicular fossa is usually necessary to gain adequate exposure for proximal control. Supraclavicular and infraclavicular incisions may be used to mobilize the proximal and distal subclavian artery. Resection of the clavicle also offers excellent exposure of the subclavian artery. Partial medial clavicular resection is rarely necessary, although it may be helpful for proximal subclavian artery exposure when median sternotomy is not feasible. The supraclavicular incision is extended medially, and the fascia and periosteum are incised. The origins of the sternocleidomastoid and pectoralis major muscles are reflected subperiosteally, the first superiorly and the second inferiorly. The medial third of the clavicle is disarticulated and subperiosteally resected with care to avoid injury to the subclavian vein. In cases of proximal left subclavian aneurysms, a left thoracotomy combined with supraclavicular exposure may be necessary.
Extra-anatomic reconstruction combined with proximal and distal aneurysm ligation has also been described in unusual circumstances. For aneurysms involving the mid subclavian artery and the distal subclavian artery, a supraclavicular incision often gives adequate exposure and may be complemented by an infraclavicular incision for distal control. Alternatively, proximal and distal control may be obtained endovascularly using balloon-occlusion catheters placed angiographically. Division or resection of the midportion of the clavicle may be necessary to gain additional exposure; if so, the clavicle may be reconstructed at the completion of the operation. If the aneurysm involves the origin of the vertebral artery, reconstruction by reimplantation or other means is appropriate, particularly if it is the dominant vertebral artery.
Results
Aneurysm resection with graft replacement is durable and yields excellent long-term results. In one of the largest reported series, normal upper extremity circulation was maintained and there were no procedure-related complications during a mean follow-up of 9.2 years. Although open repair frequently results in durable and excellent long-term outcomes, considerable associated morbidity and mortality has been reported. In-hospital mortality could be as high as 11% according to a report of open repair of innominate artery aneurysms, in which 18% of patients required prolonged ventilation. Because many patients with true aneurysms are unfit for open repair given their advanced age and multiple comorbidities, careful patient selection is mandatory to improve outcomes. Relative contraindications to open repair also include severely compromised pulmonary function, prior sternotomy or left thoracotomy, and hemodynamic instability secondary to multiple trauma.
Endovascular Repair
Endovascular repair is an attractive option for patients unfit for open repair because it is associated with lower morbidity and mortality. Many reports of endovascular repair of arch vessel aneurysms, particularly those involving the innominate and the subclavian artery, have been published in recent years. , This has led to treatment of better-risk patients with appropriate anatomy, to avoid the morbidity of open surgery. Aneurysms secondary to connective tissue disorders may also be more suitable for endovascular repair to avoid direct resection and anastomoses to diseased vessels, although long-term outcomes are not known.
Anatomic Considerations
The proximal portion and midportion of the subclavian artery are most amenable to endovascular treatment. However, several anatomic limitations exist. It is unusual for true subclavian or innominate artery aneurysms to have adequate proximal and distal landing zones. Also, coverage of branch vessels, such as the right carotid, vertebral arteries, and left internal mammary when it has been used for coronary bypass, may not be feasible. Endografts crossing the first rib may be subject to extrinsic compression. The distal subclavian artery is located between the clavicle and the first rib, and endografts in this location are subject to compression, deformation, and fracture. Another potential complication of endograft placement in the right subclavian artery is stroke from embolic debris dislodged into the right common carotid artery. The vertebral artery origin is vulnerable on both sides and may be covered during stent-graft deployment. This usually is well tolerated when the contralateral vertebral artery is patent and of adequate size. However, posterior circulation stroke may occur when the contralateral vertebral artery is highly stenotic, hypoplastic, or occluded. In this circumstance, the ipsilateral vertebral artery should be revascularized by end-to-side anastomosis to the common carotid artery or other means. Whenever the origin of the vertebral artery is involved by the aneurysm, coil embolization of the ipsilateral vertebral artery is desirable to prevent future branch vessel endoleaks.
Technique
Endovascular repair of subclavian or innominate artery aneurysms is usually performed through a transbrachial or transfemoral approach. A transaxillary or transcarotid approach has occasionally been necessary. , Both balloon-mounted and self-expandable endografts have been used off label for endovascular repair of arch vessel aneurysms. The most frequently used endografts include the Wallgraft (Boston Scientific, Natick, MA); Viabahn (W.L. Gore & Assoc, Flagstaff, AZ); or Fluency (C.R. Bard, Inc, Murray Hill, NJ). Most contemporary endografts usually require 7- to 9 -F delivery sheaths, depending on endograft diameter. However, larger endografts, such as those required for endovascular repair of innominate artery aneurysms, require still larger introducer sheaths, usually 11 or 12 F. The more flexible Viabahn endograft may be more suitable in cases of considerable arterial tortuosity. Lower-profile devices, such as the balloon-mounted iCast endograft (Atrium Medical, Hudson, NH) or Viabahn Balloon Expandable [VBX] (W.L. Gore & Assoc.), which is currently available up to 11 mm in diameter, can be delivered through 7- to 8-F sheaths. Of note, the largest iCast endograft can potentially be dilated up to 14 mm in diameter and the VBX graft to 16 mm. Because of discrepancy in proximal and distal landing zone diameters, a combination of endografts of different sizes may be necessary. Furthermore, given the rigidity of balloon-mounted endografts, these may be used for accurate proximal deployment at the level of the ostium of the vessel and combined with more flexible distal self-expanding endografts.
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