Percutaneous Transluminal Angioplasty and Stenting of the Proximal Vertebral Artery for Symptomatic Stenosis

Clinical Evaluation and Indication for PTA

Our population had a wide variety of symptoms of posterior fossa and posterior cerebral ischemia. Symptoms were refractory to medical therapy, including antiplatelet and anticoagulant medication, in all patients. The Table summarizes the patients' clinical data.

Radiologic Evaluation

CT or MR imaging of the brain was performed before digital subtraction angiography. One patient underwent an hexametazime single-photon emission CT brain study. This showed cerebellar hypoperfusion. Aortic arch angiography and four-vessel digital subtraction angiography were performed to evaluate extra- and intracranial arteries in all patients. Special attention was paid to the subclavian and vertebral arteries and to the collateral blood flow to posterior cerebral circulation. Vertebral artery stenosis was considered to be angiographically significant when greater than 70%, but only if the other vertebral artery was equally diseased or absent. The angiographic appearance of the atherosclerotic vertebral lesions in this series was uniform, showing smooth luminal stenosis without plaque ulceration at the origin of the vessel. There was no evidence of distal vertebral or basilar artery stenosis in any patient.

PTA and Stent Implantation

In all except one case, therapeutic procedures were performed during a second angiographic session. In six cases, the endovascular approach was performed via a transfemoral route with the patients under local anesthesia. In one case, a brachial approach was preferred because proximal vessel tortuosity made access too difficult via a transfemoral route.

After arterial puncture, a 7F sheath was inserted and systemic anticoagulation was achieved with IV administered heparin (5000 IU) and aspirin (250 mg). A 7F guiding catheter was then navigated into the subclavian artery, and an “angiographic roadmap” was made of the subclavian and the vertebral arteries. The narrowed arterial segment was then crossed with a 160-cm-long 0.014-inch guidewire (Transend 14; Scimed, Maplegrove, MA) that was navigated into the normal distal cervical vertebral artery. The PTA balloon catheter, with the crimped stent, was then placed over the guidewire and directed across the lesion site. The balloon was inflated up to the maximum recommended pressure to deploy and impact the stent into the inner arterial wall. Balloon inflation never lasted longer than 20 to 30 seconds.

The vertebral arteries in our patients had diameters of 3 to 5 mm, which is a caliber similar to that of coronary arteries. In the first two cases, we used Palmaz-Schatz (Johnson and Johnson, Warren, NJ) and NIR (Boston Scientific Corporation, Natick, MA) coronary stents that were manually crimped on a 5-mm-diameter coronary balloon catheter (Viva, Boston Scientific Corporation). In the five remaining cases, we used premounted NIR stents (NIR PRIMO; Boston Scientific Corporation). These allowed for easy navigation across the stenotic arterial segment and immediate, rapid, and accurate stent placement without the use of balloon predilation.

Post-PTA Medical Regimen and Follow-up

Immediately after stent placement, digital subtraction angiography was performed to assess the treated vessel. Careful attention was also paid to the intracranial circulation to rule out any sign of distal embolization. Patients were discharged from the neurologic ward 2 to 7 days (mean, 4 days) after the procedure, when their neurologic condition was determined to be stable. They received 500 mg of ticlopidine daily (Ticlid; Sanofi Winthrop, Gentilly, France) for at least 3 months after PTA. The follow-up duration ranged from 4 to 36 months (mean, 15 months) after stent implantation. Duplex Doppler sonography was used during the follow-up period to assess stent patency.

Patient Selection for Vertebral PTA

Symptomatic posterior circulation atheromatous lesions are now treatable by an endovascular approach (1). PTA of the vertebral artery may be indicated when vertebral arterial flow–obstructing lesions are found in patients with brain stem ischemia (2). Our patients presented with symptoms suggesting vertebrobasilar insufficiency, such as vestibular ataxia, vegetative disturbance (presyncopal episode), nausea, gait disturbance, and drop attacks (Table). The combination of symptoms made the diagnosis of posterior fossa ischemia almost pathognomonic. Medical therapy (anticoagulation) failed to resolve the symptoms, and endovascular revascularization (PTA and stenting) was prompted. The majority of patients with symptoms of posterior cerebral circulation ischemia, however, can be managed by conservative treatment, including anticoagulation and antiplatelet medication (3). Most patients tolerate occlusion of one vertebral artery because there is usually sufficient blood perfusion from the contralateral side. For patients presenting with bilateral vertebral stenosis who are refractory to medical treatment, PTA is a viable alternative to surgery. The goals are to improve blood flow to the posterior cerebral circulation and to reduce the risk of distal embolization (4).

Exhaustive angiography of both the posterior and anterior cerebral circulations is required before performing angioplasty. Special attention must be paid to collateral supply from the contralateral vertebral artery, as well as the external carotid artery, from which collaterals may restitute the distal vertebral artery in cases of vertebral occlusion or severe stenosis. Also, patients may have excellent filling of the posterior circulation via the posterior communicating arteries and may tolerate stenosis of one or both vertebral arteries. Considering these possibilities for collateral blood flow, it is not surprising that lesions in the vertebrobasilar system are often asymptomatic and that only the minority of patients will benefit from treatment.

PTA and Stenting of the Proximal Vertebral Artery

There have been reports of the use of PTA to treat proximal vertebral artery stenosis (1, 5–10). PTA is now a well established therapeutic alternative to operative reconstruction of proximal vertebral artery stenoses and seems to be relatively safe. No mortality has been reported after PTA. Spasm, immediate occlusion secondary to dissection, and long-term restenosis may occur after PTA. These may be asymptomatic or may lead to transient or permanent neurologic complications. Higashida et al (1) reported that 8.8% of their patients had transient neurologic complications after PTA of the proximal vertebral artery. In this series of 34 patients who underwent angioplasty without stenting, the restenosis rate was 8.8% (three patients, two of whom were symptomatic). The cases of restenoses were successfully treated with repeat balloon angioplasty. Bruckman et al (5) reported a restenosis rate of 15% after proximal vertebral artery PTA, again without stenting. Storey et al (11) implanted stents in the proximal vertebral artery in two patients to treat symptomatic restenosis. This resulted in immediate reversal of stenosis and resolution of symptoms in both patients (11). Angiographic follow-up at 1 year showed continued patency of vertebral artery lumina. Feldman et al (12) reported the case of a patient presenting with bilateral proximal vertebral artery stenoses. These lesions were treated with Palmaz-Schatz coronary stents immediately after balloon angioplasty alone failed to achieve a good anatomic result (12).

Repeat angioplasty with stent placement may be a solution to treat immediate or delayed restenosis, but primary stent placement, as it was performed in our series, may obviate the need for repeat angioplasty. Distal embolization in the cerebral circulation is always a major concern when treating diseased vessels of the cerebral circulation. Stent placement may lower the potential for embolism by smoothing luminal irregularities, decreasing turbulence, and increasing flow. Furthermore, fibrous tissue and neointimal growth over the stent mesh has been shown to cover atheromatous tissue in experimental models, thereby lowering the risk for thrombus formation and further distal embolization (13). Also, significantly lower incidence of restenosis has been shown in coronary arteries of patients after the placement of stents greater than 3 mm in diameter (14). Patients in our series underwent stent placement in vessels of 3 to 5 mm in diameter, which is a caliber similar to that of coronary arteries. Coronary stent flexibility allowed for ease of tracking along vessel tortuosity, especially when a brachial approach was used.