Occlusive Processes of the Subclavian Artery
Subclavian stenosis is a rare disease with a prevalence of 1.9% in the general population [1]. In individuals with concomitant peripheral arterial occlusive disease, this percentage increases to 11.5% [2]. In the distribution pattern, the left side is affected 3 to 4 times more frequently than the right, which is presumably due to the turbulences at the steeper left vessel origin, thereby favoring atherosclerotic changes that play a key role in the development of stenoses [3].
The vast majority of patients are asymptomatic with regard to subclavian pathology, but require treatment and control of atherosclerotic risk factors in the sense of secondary prophylaxis: platelet aggregation inhibitors, statins, and ACE inhibitors for blood pressure regulation. In the case of underlying inflammatory diseases (Takayasu arteritis, giant cell arteritis, syphilis), prednisolone equivalents are used.
For invasive measures, endovascular procedures and conventional surgical procedures are available. There is general consensus that the indication for treatment of subclavian stenosis, whether interventional or surgical, is only given if the patient exhibits corresponding symptoms [4].
The indication for intra-, extrathoracic, or interventional reconstruction depends on:
- the patient's general condition
- character and duration of neurological or arm symptoms
- location and extent of the vascular lesion
- number of diseased vessels
- morphology.
Surgical Intervention
Surgical procedures include transposition of the subclavian artery to the common carotid artery, creation of a carotid-subclavian bypass with a synthetic graft (as in the video example), as well as creation of a subclavian-axillary bypass and other extra-anatomic procedures in incomplete aortic arch syndrome.
Regarding access, trans- and extrathoracic techniques are distinguished. The transthoracic access, which requires a sternotomy or thoracotomy, was first described in 1958 by DeBakey, who at that time created an ascending-carotid bypass [5]. Transthoracic surgical techniques have largely been abandoned in favor of less invasive extrathoracic accesses. However, a prerequisite for extrathoracic access is freely patent donor arteries in the neck and shoulder area. Invasive transthoracic accesses are considered in multi-vessel disease with compromise of all three supra-aortic branches, treatable aortic arch aneurysm, or indicated coronary revascularization or valve replacement.
Stent-Supported Angioplasty
The first reports of endovascular angioplasty of the subclavian artery date back to 1980 [6]. Since then, treatment has increasingly developed towards stent-supported angioplasty and is now mostly performed as stent-PTA [6,7]. The transfemoral access for the treatment of stenoses of the subclavian artery or the brachiocephalic trunk is preferably used. In the presence of more complex pathologies, puncture of the brachial artery offers better prospects of crossing the stenosis, but higher complication rates at the puncture site must be accepted (dissection and occlusion of the brachial artery). For isolated subclavian stenoses, balloon-expandable stents are used; for long-segment stenoses > 40 mm, self-expanding ones. To avoid occlusion, but also cerebral embolizations, the vertebral origin should not be overstented if possible. Stents in the movement segment below the clavicle are prone to stent fractures and occlusions.
Results
Transthoracic reconstruction of isolated subclavian stenosis is no longer performed. However, in multi-vessel diseases, it shows low mortality rates and excellent long-term results [8]. Takach et al. evaluated 157 patients with multi-vessel disease [9]. A transthoracic procedure was performed in 113, an extrathoracic in 44 patients. The mortality rate was similarly low in both groups (2.7% transthoracic, 2.3% extrathoracic). After 10 years, bypass failure was shown in the transthoracic group in 6% of patients, while in the extrathoracic group, 40% of the bypasses were intact. Bypass failure is significantly influenced by non-aortic inflow. The same group of authors examined the results after surgical vs. endovascular therapy in 391 patients (229 vs. 162 patients) [10]. Mortality rates were similar (0.9% surgical, 0.6% endovascular), but long-term results after 5 and 10 years were significantly better in the surgical group.
Mortality rates for extrathoracic procedures of the subclavian artery range between 1% and 5%. The main cause of death was cardiovascular comorbidities, which occur significantly more frequently in patients with subclavian stenosis due to atherosclerosis [11, 12]. Cina et al. evaluated in their analysis 511 patients with subclavian-carotid transposition and 516 patients with carotid-subclavian bypass. With an average observation period of 61 months, the patency rate for the subclavian-carotid transposition group was 99%, in the carotid-subclavian bypass group for synthetic bypasses after 58 months 86% and for vein bypasses after 49 months 74% [11].
The success rates of dilation in the 1980s varied for stenoses between 88% and 100% [13 -16], for occlusions between 46% and 100% [16, 17]. Embolic occlusions were observed in 3% [18] and strokes in 2% [19]. Follow-up checks showed that restenoses occurred in 10% to 28.5% of patients [18, 20, 21]. To reduce the rate of recurrent stenoses, stents were implanted [22], which leads to typical complications such as stent dislocation in 9% of cases [23]. In a single-center study, the primary and secondary patency rates after stent angioplasty were 91.7% and 96.5% after 1 year and 77% and 91.7% after 2 years [15]. Henry et al. reported similar results with 79% primary and 86% secondary patency rate after 2 years [24]. Zaytsev et al. showed a restenosis rate of 6% after stent angioplasty of the subclavian artery [25]. Schillinger et al. reported on 76 interventions a technical success rate of 93.3% and the following complications: in one patient each blood pressure drop and bradycardia, second-degree AV block, transient occlusion of a subtotally stenosed innominate artery, and a puncture hematoma not requiring treatment in 4 patients [26].