A novel two-stage surgical approach for the treatment of symptomatic supra-aortic artery aneurysms

Introduction

Supra-aortic artery aneurysms represent a rare form of peripheral aneurysms. Though often asymptomatic and discovered incidentally through routine imaging studies, these aneurysms mandate surgical repair in order to prevent subsequent complications resulting from thrombosis or embolization. We describe the case of a patient with a unique constellation of symptomatic supra-aortic artery aneurysms that was not amenable to endovascular repair. Ultimately, the patient was successfully treated with a novel two-stage open surgical approach.

Case report

A 45-year-old Caucasian man with no significant past medical history underwent a chest X-ray as part of an initial work-up for chronic cough which revealed a 3.4-cm right paratracheal rounded opacity (Figure 1). Subsequent conventional arteriography and contrast-enhanced computed tomographic angiography (CTA) of the neck, chest, abdomen and pelvis revealed diffuse aneurysmal disease involving the bilateral subclavian, carotid and vertebral arteries. There was no aneurysmal involvement of the ascending aorta. The vertebrobasilar junctions were noted to be intact. The proximal innominate artery was ectatic, measuring 1.2 cm at its origin and enlarging to 1.5 cm at the level of the trachea. The proximal right common carotid artery had a focal 1.4-cm aneurysmal dilation, and the right subclavian artery had a 3.7-cm fusiform aneurysm extending into the axillary artery. The maximum transverse diameter of the proximal right vertebral artery measured 2.5 cm associated with significant mural thrombus and ulcerated plaque. On the left, the common carotid artery was noted to have a 1.4-cm aneurysmal dilation protruding posteriorly. The left subclavian artery was markedly irregular distal to its origin and featured a 3.7-cm focal aneurysm with mural thrombus and aneurysmal extension into the origin of both the left vertebral (maximal diameter, 1.2 cm) and left internal thoracic (maximal diameter, 0.8 cm) arteries. A three-dimensional reconstruction of the CTA is shown in Figure 2. There was no clinical evidence of atheroembolic or compressive symptoms in any areas related to his aneurysmal disease at the time of the patient's initial presentation. He had equal bilateral carotid pulses and no bruits, but did have prominent pulsation in the supraclavicular areas bilaterally. The patient did not have a personal or family history of any connective tissue diseases such as Marfan's syndrome or Lowes Dietz syndrome. A full genetic work-up was negative, including genetic testing of TGFBR1, TGFBR2 and GLUT10.

OPEN IN VIEWER

Figure 1

Chest X-ray demonstrating 6.2 × 4.3-cm right paratracheal rounded opacity (arrow)

OPEN IN VIEWER

Figure 2

Three-dimensional reconstruction demonstrating aneurysms of the bilateral carotid, subclavian and vertebral arteries. White arrow demonstrates aneurysmal degeneration of the right vertebral artery

Over the course of the patient's extensive diagnostic evaluation, the patient experienced a discrete episode of blurred vision and headache. Computed tomography of the head revealed multiple acute and subacute infarctions in the right cerebellum and bilateral occipital lobes, right side greater than left. Evaluation failed to demonstrate intracardiac sources of emboli or significant carotid artery stenosis.

The patient presented to us for surgical evaluation two months after his stroke. He was since maintained on warfarin and was noted to have a residual left lateral field cut. Interval imaging again demonstrated a very large thrombus-filled innominate artery aneurysm arising very close to its takeoff from a normal aortic arch, and involved nearly the entire course of the right subclavian as well as the proximal right common carotid and origin of the right vertebral artery. Due to the complexity and extent of aneurysmal involvement, a two-stage open surgical approach was planned.

The patient was taken to the operating room where he underwent a right carotid artery to vertebral artery bypass with reverse saphenous vein graft (Figure 3). The vertebral artery was ligated proximally where it was aneurysmal. He tolerated the procedure well. On postoperative day 5, the patient returned to the operating room for the planned second stage of the reconstruction. A right infraclavicular incision was performed in order to access the normal-appearing proximal axillary artery. Next, a median sternotomy was carried out to visualize the ascending aorta and arch vessels. The innominate artery aneurysm had distorted the usual anatomic contour of the great vessels, resulting in inadequate exposure of the normal-appearing right common carotid artery via the transthoracic approach. As such, the right anterolateral neck incision that was used five days earlier to perform the carotid–vertebral bypass was re-opened. The bypass was identified and noted to be widely patent. The innominate artery was then clamped 2 cm above its origin and amputated. In situ reconstruction was then performed utilizing a 16 × 8-mm bifurcated Dacron graft sewn to the proximal aortic arch at the level of the debrided innominate artery stump, with distal extension to the mid right common carotid and proximal right axillary arteries. The proximal axillary artery was amputated, with oversewing of the proximal stump and matching of the distal end to the axillary limb of the Dacron graft. The patient had normal electroencephalogram recordings at the conclusion of the operation.

OPEN IN VIEWER

Figure 3

Stage one of the reconstruction: right carotid (long arrow) to vertebral artery bypass with reverse saphenous vein graft (short arrow)

Postoperatively, the patient recovered without complications. He remained neurologically intact. Pathology of the resected innominate artery demonstrated non-specific mild intimal hyperplasia and chronic periadventitial inflammation. Intraoperative tissue cultures from the second operation were positive for rare Propionibacterium acnes. An infectious disease consultation was obtained. Given the absence of fever or leukocytosis, the positive cultures were felt likely to be a contaminant; however, in light of the patient's risk and the potential of not treating a vascular infection, six weeks of clindamycin was recommended. He was discharged home on postoperative day 20 from the first stage of the reconstruction. Follow-up at six weeks found the patient to be well, and without clinical signs or symptoms of ischemia or neurological impairment. He has since discontinued antibiotic therapy.

Discussion

Aneurysms of the supra-aortic vessels are quite uncommon when compared with other peripheral arteries, and are estimated to account for less than 4% of all peripheral aneurysms. ^1–4 In a retrospective review of the Mayo Clinic records spanning 40 years, Bower et al. ² found only 73 patients treated surgically for supra-aortic aneurysms, including 38 subclavian, 25 extracranial carotid, six innominate, three aberrant right subclavian and one vertebral artery aneurysm. Only five of these patients had additional untreated supra-aortic aneurysms. In addition, Dent et al., ⁵ performed an extensive review at the University of Michigan and discovered the incidence of innominate or subclavian artery aneurysms to be only 0.27% among 1488 patients with other atherosclerotic aneurysms. No carotid or vertebral artery aneurysms were observed in this analysis. The most recent series to date, conducted by Cury et al., ⁶ identified 74 patients with supra-aortic aneurysms over a 17-year period (1990–2007) at the Cleveland Clinic. Subclavian artery aneurysms were most commonly encountered, accounting for 50% of all aneurysms in this series, followed by aneurysms of the common carotid (36%), internal carotid (10%), innominate (3%) and vertebral (1%) arteries. To our knowledge, there has been no previous report of a single patient with such diffuse supra-aortic aneurysmal disease with involvement extending to the innominate, carotid, subclavian and vertebral arteries.

Supra-aortic arterial aneurysms most often stem from underlying atherosclerotic disease. The predominance of other etiological factors varies by vessel type, but commonly includes connective tissue disorders, vasculitis, trauma, iatrogenic and infection. ^4,6 Kieffer et al. ⁷ reported the experience of treating 27 patients with innominate artery aneurysms over nearly three decades. Common pathologies in this experience included Takayasu's disease in seven, followed by atherosclerosis in six, syphilis in five and chronic dissection in three patients. In a 20-year experience with the treatment of 31 patients with subclavian artery aneurysms by Pairolero et al., ⁸ underlying causes included atherosclerosis in 12, traumatic pseudoaneurysm in 10 and thoracic outlet obstruction in six patients. Development of carotid artery aneurysms, on the other hand, has been related to fibromuscular dysplasia, kinking or stenosis with poststenotic dilation, spontaneous dissection or post-traumatic changes as a result of cervical hyperextension or rotational injury. ^9,10 Aneurysms of the extracranial vertebral artery are exceedingly rare, with only isolated case reports citing head and neck trauma as the primary causal factor. ^11,12 Other less common causes of vertebral artery aneurysms include connective tissue disorders, chiropractic manipulation, congenital and infection. ^13–17

Given the role of atherosclerotic degeneration in the development of these aneurysms, such patients are frequently elderly. Most supra-aortic aneurysms are asymptomatic. Incidental diagnosis has become increasingly common, as occurred in our case, with these aneurysms often initially being detected as a mediastinal mass on plain chest X-ray or during routine radiographic evaluation of other thoracic aortic pathology. ^6,18,19 Definitive diagnosis requires utilization of CTA and/or conventional arteriography. When present, clinical signs and symptoms may feature pulsatile supraclavicular masses, chest pain, or upper extremity rest or exertional pain. In addition, a wide range of compressive syndromes may be present characterized by dysphagia, dyspnea, hoarseness, Horner's syndrome or superior vena cava syndrome. ^3,6,19,20 In more severe cases, symptomatic manifestations can progress to include digital ischemia, transient ischemic attacks, stroke or hemodynamic instability as a result of thrombosis, embolization or, rarely, rupture. ^2,7

Elective surgical treatment is required for supra-aortic arterial aneurysms, even when asymptomatic, as their natural history is one of aneurysmal expansion and increased risk of complications if left untreated. ^21,22 The optimal approach to surgical intervention varies on the location and size of the aneurysm(s), with special attention to the preservation of adequate cerebral perfusion in cases involving the innominate artery. Exposure of the innominate and proximal subclavian and carotid vessels is best achieved via a median sternotomy, whereas more distal aneurysms of the extrathoracic subclavian or carotid arteries often require supraclavicular, infraclavicular or anterolateral neck approaches. A thoracotomy is rarely indicated. The gold standard open surgical technique for supra-aortic aneurysms involves the use of an interposition graft. A wide variety of other open techniques have been described in the literature, such as ligation alone, patch angioplasty and aneurysm resection with end-to-end anastomosis. ^7,19,22,23 While early series noted mortality rates in excess of 40%, ²⁴ advances in surgical methods and perioperative care have reduced these rates to 0–11% in more contemporary reports. ^6,7,23

With the advent of endovascular technology, the approach to supra-aortic artery aneurysms has evolved to include commercially available stent grafts. Numerous case reports and case series have advocated stent grafts as a safe and effective alternative therapeutic modality for the exclusion of supra-aortic aneurysms. ^6,15,25–27 Despite these successful accounts, anatomic limitations prohibit the widespread use of stent grafts in these settings, particularly for more proximal supra-aortic aneurysms. Aneurysms of the innominate and subclavian arteries often lack adequate proximal and distal landing zones. Moreover, coverage of some brachiocephalic vessels, namely the right carotid, vertebral and left internal thoracic (when used in setting of coronary bypass) arteries, are not well tolerated in some individuals. Hybrid procedures have been described in such cases to maximize the therapeutic benefits of this minimally invasive technique. ^6,28

Our case features a patient with a unique constellation of multiple symptomatic supra-aortic aneurysms. The multiplicity and distribution of cerebral infarcts seen in our patient favored an embolic etiology from disrupted plaque originating in an aneurysmal right vertebral artery. We felt that the right-sided supra-aortic aneurysms warranted initial repair as they served as the source of the patient's prior embolic event and, moreover, their larger size relative to the left side served as an independent risk factor for rupture. Endovascular repair was not a viable option in this patient due to the diffuse and bilateral nature of aneurysmal disease, including the notable involvement of the right vertebral artery. An open technique involving utilization of a bifurcated graft for innominate artery aneurysms extending into the right subclavian and carotid arteries has previously been reported. ^1,29 This open approach alone, however, would not address the right vertebral artery aneurysm in our case. As such, we felt a two-stage approach beginning with a right carotid to vertebral artery bypass would successfully achieve exclusion of all right supra-aortic artery aneurysms in this patient and provide adequate vertebrobasilar, cerebral and peripheral re-vascularization. Given that the left-sided supra-aortic artery aneurysms remain small and asymptomatic, we plan to follow these for now with CTA at six-month intervals. New onset of symptoms and/or aneurysmal growth will prompt future surgical intervention.

In conclusion, we successfully treated a patient with diffuse symptomatic supra-aortic aneurysms using a novel two-stage open surgical approach characterized by initial carotid–vertebral artery bypass, followed by in situ reconstruction of the innominate trunk with a bifurcated Dacron graft off the proximal aortic arch to the mid right common carotid and proximal right axillary arteries. The advent of new endovascular techniques and devices may evolve in the future to provide a suitable alternative therapeutic option for patients like ours whose anatomic constraints effectively prohibit repair by currently available endovascular means.