General Description

Vertebral artery (VA) stenosis often presents with posterior circulation stroke or with symptoms of vertebrobasilar insufficiency. Nearly a quarter of patients presenting with such symptoms are found to have > 50% stenosis in the vertebrobasilar system. Duplex ultrasound imaging may reveal to-and-fro flow patterns, diminished waveforms, or even retrograde flow, indicating subclavian artery steal. The most common area of VA stenosis is at its origin off the subclavian artery. Stenting has been used to reduce stenosis, restore flow patterns, and reduce the overall risk of recurring symptoms.

Indications

The decision to open a stenosed VA is guided by (1) the degree of stenosis in the impacted vessel, (2) the presence of symptoms or magnetic resonance–verified strokes attributable to the stenosis, and (3) the relative dependency on the affected vessel. Symptoms may be from one of two etiologies, namely, flow-related because of reduced flux through a fixed stenosis, or thromboembolic because of plaque rupture or turbulent flow across the plaque. The former should be augmented with stenting, whereas the latter may be reasonably treated with maximal medical management consisting of dual antiplatelet and high-dose statin therapies. Because the posterior circulation typically has a redundant supply, an atretic or compromised contralateral vessel increases the need for revascularization, whereas a robust or even dominant contralateral supply may decrease the need. The neurointerventionist’s judgment should be personalized based on the confluence of patient factors.

Neuroendovascular Anatomy

The paired VAs arise from the subclavian arteries. They course caudally and enter the foramen transversaria at approximately the level of the C6 vertebra. Within the bony foramen, they rise to the C2 level before exiting to cross the C1 arch, run through the suboccipital triangle, and enter the foramen magnum. The VAs join at the vertebrobasilar junction anterior to the brainstem to form the basilar artery. The VA can be divided into four segments as follows: V1 (pre-foraminal) extending from the origin off the subclavian artery to insertion into the foramina of the transverse processes, V2 (foraminal) extending from C6 to where the artery exits at C2, V3 (extradural) encompassing the segment extending from the foraminal exit at C2 to where the artery pierces the dura at the foramen magnum, and V4 (intradural) extending from the dural origin to the vertebrobasilar junction anterior to the brainstem.

Specific Technique and Key Steps

1. 
   

   Noninvasive imaging consisting of computed tomography angiography extending from the aortic arch to the vertex is invaluable in assessing the access route and planning the intervention. Often, the VA is more easily accessed using an ipsilateral radial or distal radial artery approach, particularly for right-sided lesions. However, a proximal takeoff from the subclavian artery or the arch origin of the left VA may make transfemoral approaches more technically desirable. The route of choice is selected, and 6 French (F) access is obtained with a long sheath (Fig. 15.1, Video 15.1).

   
   
2. 
   

   The long sheath is advanced over a 0.035-inch wire under roadmap guidance to a position just proximal to the VA origin. The wire is then removed.

   
   
3. 
   

   To evaluate the vasculature and obtain proper views for placement of the stent, angiographic runs of the cervical and intracranial vessels are obtained prior to placing the stent. Ideally, the VA origin will be visible on the anteroposterior images, and the lateral images can help to show the vertebral arch around C1, which will be the destination for distal wire access in cases of VA origin stenting (Video 15.1).

   
   
4. 
   

   A balloon-mounted stent is backloaded on the microwire system, and a slight hockey stick shape is placed in the wire to guide it through the stenosis (Fig. 15.1, Video 15.1).

   
   
5. 
   

   The stent and wire are advanced to the tip of the guide catheter within the subclavian artery, and fresh runs are obtained.

   
   
6. 
   

   Under roadmap guidance, the wire is advanced through the stenosis and into the distal cervical VA, usually just proximal to the C1 arch.

   
   
7. 
   

   The stent is advanced into the stenosis and placed two-thirds within the vessel with one-third overhanging into the subclavian artery. The balloon is inflated to the appropriate pressure as described in the manufacturer’s guidelines to obtain adequate wall apposition and opening of the stenosis (Fig. 15.1, Video 15.1).

   
   
8. 
   

   The balloon is deflated while aspirating from the guide catheter to avoid distal emboli (Video 15.1).

   
   
9. 
   

   Follow-up runs are obtained of the cervical and intracranial vasculature to ensure adequate placement of the stent, resolution of the stenosis, and that no distal emboli have resulted (Video 15.1).

   
   
10. 
    

    The wire and guide catheter are withdrawn, and the access point is closed.