Long-term outcome after surgical and endovascular management of true and false subclavian artery aneurysms

Introduction

Subclavian artery aneurysms are rare. Dent et al. ¹ found true subclavian artery aneurysms in 0.13% of 1488 patients with atherosclerotic aneurysms of the abdominal aorta and its peripheral branches. Etiological factors for the development of a subclavian artery aneurysm are atherosclerosis, thoracic outlet syndrome, trauma including iatrogenic lesions, collagen disorders and infection. The risk of severe complications as rupture, thrombosis, embolization and compression of adjacent neurovascular structures implicates the necessity of treatment in most cases. Therapeutic options include surgical and endovascular procedures. Open operative techniques have been the standard treatment for subclavian artery aneurysms. Depending on the localization, the extent of the aneurysm and the involvement of adjacent arterial branches, various surgical approaches and techniques are applied, ranging from resection and re-anastomosis to anatomic or extra-anatomic reconstructions. Stent graft implantation requires certain morphological criteria of the aneurysm and has shown itself to be a valuable treatment method for traumatic and iatrogenic cases and patients with high surgical risk. ²

In the literature there are only few long-term follow-up reports after subclavian artery aneurysm treatment. The aim of our study was to show long-term results after open surgical and endovascular techniques, focalizing on technical success, patency rates and periprocedural complications. Also clinical presentation was recorded.

Material and methods

Patients treated for subclavian artery aneurysm at our department from 1996 to 2010 were included in our series. Pre- and postoperative/postinterventional diagnostics included clinical and angiological examination to assess patency rates of the reconstruction and the vertebral arteries, need for secondary treatment and periprocedural complications. All patients underwent pre- and postoperative angiography, either conventional angiography, computed tomography angiography or magnetic resonance angiography. Postoperative control also comprised sonographic evaluation. Pre- and postoperative/postinterventional aneurysm-related symptoms were assessed.

Follow-up consisted in regular clinical and angiological examinations, apart from the postoperative angiographic evaluation further angiographic controls were indicated in symptomatic patients.

Results

From 1996 to 2010 21 patients with subclavian artery aneurysms have been treated at our department. As six patients were lost to follow-up long-term data were available from 15 patients. Nine were men, the mean age was 53 years (range 20–81). The etiology was atherosclerotic in eight patients and post-traumatic in two, in three cases a thoracic outlet syndrome was the underlying disease and in two patients a collagen disorder. Ten aneurysms were located in the right and five in the left subclavian artery. Nine aneurysms were located in the proximal segment, two in the middle segment and four in the distal segment of the subclavian artery. Average aneurysm diameter for patients in the open surgical and endovascular repair group was 2.4 (1–6) cm and 3.2 (2–5.8) cm, respectively.

Primarily 11 patients underwent open surgical reconstruction, four patients were treated endovascularly. Two different surgeons performed all open procedures. All interventional treatments were carried out by different radiologists. In our hospital, an interventional 24-hour service is provided by the department of radiology. The decision between open or endovascular repair was based on the anatomy and etiology of the subclavian artery aneurysm, and co-morbidities. Primary endovascular repair was performed in two emergency cases with rupture of a post-traumatic pseudoaneurysm, in one with a dissecting aneurysm in connective tissue disease and one with high risk for open repair. In cases without adequate proximal aneurysm neck (10–15 mm from the vertebral artery) as anchoring zone for stent graft placement, need for re-implantation of the vertebral artery or operative decompression for thoracic outlet syndrome (TOS) induced subclavian artery aneurysms, open surgery was performed.

For endovascular repair balloon-expanding and self-expanding stent grafts were placed via a transfemoral (n = 1) or a transbrachial (n = 3) access (Table 1). Overstenting of the vertebral artery did not occur in all interventionally treated patients.

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Table 1

Technical details of endovascular treatment

Procedure	n	Technical details	n
Primary endovascular	4	Wallgraft, self-expanding (12/50 mm and 10/50 mm)	2
		Fluency, self-expanding (13,5/100 mm)	1
		Jo-Stent, balloon-expanding (4–9/28 mm)	1
Secondary endovascular	2	Jo-Stent, balloon-expanding (7/39 mm)	1
		Zenith, balloon-expanding (16/37 mm)	1

Open surgical reconstruction was performed via a supraclavicular approach in five patients, treatment of the three subclavian artery aneurysms caused by TOS-included operative decompression by resection of the first rib (n = 2) or claviculotomy (n = 1). In six patients a partial sternotomy was necessary to gain a secure control of the diseased vessels. Surgical techniques were aneurysm resection and direct end-to-end anastomosis in three cases. Interposition of an arterial homograft was used in one case. Synthetic grafts were used in seven patients in total, including one carotid-subclavian bypass and one brachiocephalic trunk-subclavian-carotid bifurcation bypass. In one patient transposition of the vertebral artery to the common carotid artery (end-to-side anastomosis) was performed, in three patients the vertebral artery was re-implanted into the synthetic graft. In all other cases, the vertebral artery was not involved (Table 2).

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Table 2

Treatment modalities according to aneurysm characteristics and preoperative diagnosis

Aneurysm characteristics/preoperative diagnosis	Localization of the aneurysm in the SA (segment)	Endovascular treatment	Access	Open surgery	Access	n
True, atherosclerotic	Proximal, including proximal VA	–	–	Resection and EEA of SA, transposition of VA to the common carotid artery (ESA)	Sternotomy	1
True, suspected mycotic aneurysm, collagen disorder	Proximal	Secondary (stent graft and coil embolization)	Transfemoral	Homograft interposition	Sternotomy	1
Dissecting aneurysm, collagen disorder, previous cardiac surgery	Middle	Primary	Transfemoral	–	–	1
True, TOS, peripheral embolization	Distal	–	–	Resection and EEA, rib resection, embolectomy	Supraclavicular	1
True, TOS, peripheral embolization	Distal	–	–	Synthetic graft interposition, rib resection, embolectomy	Supraclavicular	1
True, TOS, peripheral embolization	Distal	–	–	Synthetic graft interposition, claviculotomy, embolectomy	Supraclavicular	1
Pseudoaneurysm, posttraumatic	Distal	Primary	Transbrachial	–	–	1
True, atherosclerotic, peripheral embolization (finger artery)	Proximal, including BT	–	–	BT – subclavian-carotid bifurcation bypass	Sternotomy	1
True, atherosclerotic, stenotic SA origin	Proximal, including VA origin	–	–	Carotid-subclavian bypass, VA reimplantation	Supraclavicular	1
Pseudoaneurysm, post-traumatic, sternum an rib fractures, hematothorax	Proximal, including BT	Primary + re-intervention (stent graft)	Transbrachial	–	–	1
True, atherosclerotic	Proximal, including VA origin	–	–	Synthetic graft interposition, VA reimplantation	Supraclavicular	1
True, atherosclerotic, high number of co-morbidities	Middle	Primary	Transbrachial	–	–	1
True, atherosclerotic	Proximal, including VA origin	–	–	Synthetic graft interposition, VA reimplantation	Sternotomy	1
True, atherosclerotic	Proximal	–	–	Synthetic graft interposition	Sternotomy	1
True, atherosclerotic	Proximal	–	–	Sesection and EEA	Sternotomy	1

The mean follow-up period was 77 months (83 months for the open surgical group, 38 months for the endovascular group). Ten of 11 reconstructions after open surgery and all stent grafts were patent in the follow-up controls. All vertebral arteries in both treatment groups remained open.

Secondary interventions consisted of one coil embolization and following stent graft implantation after primary open surgery, and one endovascular re-intervention: The homograft that was primarily implanted under the assumption of a mycotic aneurysm, which finally turned out to be a Behcet's disease, degenerated. The following false aneurysm was treated by stent graft implantation and coil embolization that occluded later without symptoms. An endovascular re-intervention was necessary in one patient with dissection of the brachiocephalic trunk.

One type II endoleak (caused by the suprascapular artery) after stent graft implantation disappeared in the following period. After open surgery, one synthetic graft occluded without symptoms. One patient developed a synthetic graft MRSA (methicillin-resistant staphylococcus aureus) infection with fistulization into the upper mediastinum. An operative revision was refrained because of the necessity of an extended procedure in this critically ill patient, who died a few weeks later. Procedure-related complications consisted in an incomplete Horner`s syndrome (miosis) in one patient, in another case a recurrent peripheral embolization occurred (Table 3). There was no 30-day mortality for both treatment groups. Four patients died in the follow-up period: the patient with the graft infection died 123 months postoperatively. One patient died 70 months postoperatively because of an amyotrophic lateral sclerosis and two patients died for unknown reasons five and 14 months postoperatively, respectively, showing normal findings concerning the subclavian artery aneurysm reconstruction.

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Table 3

Procedure related complications

Procedure	Complication	n
Endovascular treatment	Residual dissection	1
	Type II endoleak (regressive)	1
	Occlusion of secondarily implanted stent graft	1*
Open surgery	Postoperative aneurysm formation	1*
	Asymptomatic occlusion of the reconstruction	1
	Recurrent peripheral embolization	1
	Vascular prosthesis infection	1
	Horner's syndrome	1

Preoperative complaints were peripheral neurovascular symptoms (upper extremity paraesthesia, ischemia or swelling), cervicothoracic pain, subclavian steal syndrome and one Horner's syndrome; three subclavian artery aneurysms were incidental findings.

Seven out of 10 patients with preoperative subclavian artery aneurysm related complaints were free from symptoms after the aneurysm repair, in three patients peripheral neurovascular symptoms persisted (Table 4). Both graft occlusions were asymptomatic.

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Table 4

Pre- and postoperative subclavian artery aneurysm-related symptoms

Symptoms	Preoperatively (n)	Postoperatively (n)
None	5	10
Peripheral neurovascular symptoms	6*	3
Cerebral ischemia	3*	0
Cervicothoracic pain and swelling	3*	1
Horner's syndrome	1*	1

Discussion

Standard management of subclavian artery aneurysm has been conventional surgical repair by now. Promising results have been shown with endovascular techniques over the last years. Endovascular therapy of a subclavian artery injury was first reported by Becker et al. ³ in 1991. Since then several reports of endovascular treatment of the subclavian artery have been published.^4–9

Outcomes after subclavian artery aneurysm management documented in literature are mostly restricted to case reports. The objective of our single centre study was to show long-term follow-up results of surgical and endovascular therapy of subclavian artery aneurysms. The limitation of our study is the rather small number of patients, nevertheless, for this rare disease, encouraging results concerning long-term patency and technical success could be shown years after different surgical techniques and after intervention.

In their investigation of 12 patients with interventionally-treated subclavian artery aneurysms, Schoder et al. ⁷ found a primary patency rate of 100% after a mean follow-up of 11.6 months. In their series of nine patients with subclavian artery aneurysm treated with stent grafts Hilfiker et al. ⁴ described primary and secondary patency rates of 89 and 100%, respectively, after a mean follow-up of 29 months. In our series all primarily implanted stent grafts remained open during the mean follow-up period of 38 months. The only stent-graft occlusion occurred in a patient with connective tissue disease after secondary treatment of a false aneurysm of the implanted arterial homograft. All vertebral arteries remained open.

Recently Naz et al. ¹⁰ reported an early patency rate of 100% after open surgical treatment of 10 patients with subclavian artery aneurysms. Also in our experience good patency rates were observed after surgery, with 10 of 11 reconstructions open after a mean follow-up period of 83 months.

In their review of 381 subclavian artery aneurysm patients Vierhout et al. found complication rates of 26 and 28%, respectively, after open surgery and endovascular repair. Cardiopulmonary complications were restricted to open repair. The authors showed a similar mortality rate for open and endovascular procedures of 5%. Mortality rates for conventional elective and emergency procedures were 3 and 13%, respectively and for endovascular repair 4 and 8%. ² We did not observe access related complications after endovascular treatment. Complications were limited to one residual dissection, one type II endoleak (regressive) and one occlusion of a secondarily implanted stent graft. Cardiopulmonary complications did not occur after both endovascular and open surgery. Following open surgery one case of a partial Horner`s syndrome was seen, the one vascular prosthesis infection occurred ten years postoperatively. In our study 30-day mortality for both treatment groups was 0%. In total, four patients died in the follow-up period, between five and 123 months postoperatively: one because of a graft infection, one because of an amyotrophic lateral sclerosis and two patients died for unknown reasons, showing normal findings concerning the subclavian artery aneurysm reconstruction in the controls.

Although due to the small number of patients in our study, it is not possible to draw statistical conclusions as to which operative procedure should be applied for which special case, we show our recommendations for treatment according to our experience in Table 5.

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Table 5

Recommendations for treatment of subclavian artery aneurysms

Patient/aneurysm characteristics	Endovascular treatment	Open surgery
Young age/long life-expectancy		+
High operational risk (relevant co-morbidities)	+
Emergency patient with concomitant injuries requiring surgical treatment		+
Emergency patient with local edema/hematoma, without concomitant injuries requiring surgical treatment	+
TOS requiring surgical decompression		+
Adequate proximal landing zone (aneurysm at a distance of ≥10–15 mm from vertebral artery)	+
Embolic complications requiring surgical treatment		+
Pseudoaneurysm, dissecting aneurysm	+
Infectious cause		+
Secondary procedure	+

For the elective treatment of young patients with long life-expectancy and low-operational risk, open surgery should be preferred. In our study, good long-term patency rates were observed also after endovascular treatment. Nevertheless, large sample long-term investigations concerning patency rates are still missing. With indication for open surgical treatment, especially the cardiopulmonary risk has to be considered.

To provide an adequate proximal landing zone for stent graft implantation, the distance between aneurysm and vertebral artery should not come below 10–15 mm. We try to avoid elective overstenting of the vertebral artery to reduce neurovascular complications and the type II endoleak incidence. In case of necessary overstenting of the vertebral artery, we recommend additional embolization because of the otherwise high endoleak risk due to its diameter. If the type II endoleak in our patient (caused by the suprascapular artery) would not have disappeared spontaneously, coil embolization would have been performed after localization of the main feeding vessel by a microcatheter.

Pseudoaneurysms are mainly caused by trauma or infection. Regardless of age, we recommend endovascular repair for trauma patients without concomitant injuries requiring surgical treatment, in order to avoid additional tissue damage, blood loss and long-term anaesthesia. We would recommend open surgical treatment of mycotic pseudoaneurysms in young patients (with a long life-expectancy) without high operational risk, to prevent recurrent/persistent infection.

Conclusion

In our retrospective study good long-term patency rates, low periprocedural morbidity and low secondary intervention rates could be shown in both treatment groups. With correct indication, both open surgery and endovascular techniques allow for successful and safe subclavian artery aneurysm therapy.