Prognosis of Proximal and Distal Vertebrobasilar Artery Stent Placement

Study Participants

In our prospective cohort registry, we conducted a retrospective review of data from patients who underwent VBS at our stroke center between September 2013 and January 2023. The criteria for performing VBS at our stroke center are as follows: 1) Patients with symptomatic vertebrobasilar artery stenosis who are worsening despite the best medial treatment, 2) patients with recurrent symptomatic ischemic stroke despite the best medical treatment, and 3) symptomatic patients who have the unilateral vertebral artery occlusion or posterior inferior cerebellar artery ending in the unilateral vertebral artery, and have severe stenosis in the contralateral vertebral artery. Our study enrolled adult patients aged ≥18 years who underwent either extracranial or intracranial VBS. The exclusion criteria included patients who: 1) presented with asymptomatic vertebrobasilar artery stenosis, 2) underwent emergent VBS, and 3) did not undergo follow-up neurovascular imaging after the stent procedure. The ethics committee of our tertiary hospital approved this study (Approval No. 2022–0348) and waived the requirement for informed consent due to the retrospective nature of the study.

Clinical, Procedure-Related, and Laboratory Variables

This study was single-center retrospective cohort study, and we conducted a retrospective review of data from patients who underwent VBS at our stroke center between September 2013 and January 2023. Clinical factors including preprocedural NIHSS score, postprocedural NIHSS score, and 3-month mRS score were collected. Procedure-related factors included stent location (extracranial vertebral artery and intracranial vertebrobasilar artery), the degree of stenosis before stent placement (severe: ≥70%, moderate: <70%), residual stenosis after stent placement (≥30%; Fig 1), stent diameter, stent length, stent type (closed-cell design versus open-cell design), techniques used for balloon angioplasty (no balloon angioplasty, pre-stent placement balloon angioplasty, post-stent placement balloon angioplasty, and pre-stent and post-stent placement balloon angioplasty), balloon diameter, balloon length, total procedure duration, and the utilization of an embolic protection device (EPD). Extracranial VBS was performed by using Protégé (Covidien), Enterprise (Cerenovus), or Acclino (Acandis), and intracranial VBS was performed by using Acculink (Abbott Laboratories), Precise (Cordis), Wingspan (Stryker Neurovascular), or Neuroform Atlas (Stryker Neurovascular).

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FIG 1.

Schematic diagram of the measurement of residual stenosis after stent placement (≥30%) and in-stent restenosis (>50%) during follow-up period. Residual stenosis after stent placement was defined as the remaining stenotic portion compared with the normal vessel diameter ([a-b]/a × 100). When (a-b)/a × 100 was larger than 30%, we considered it indicative of residual stenosis after stent placement. On the other hand, in-stent restenosis was defined as a stenosis of >50% when compared with the residual stenosis immediately following a procedure during the follow-up period ([b-c]/b × 100). When (b-c)/b × 100 was larger than 50%, we considered it as in-stent restenosis.

Furthermore, we collected laboratory data, including hemoglobin A_1c (HbA_1c), total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol levels. All patients in this study received aspirin and clopidogrel for a minimum of 5 days before undergoing VBS. Resistance to antiplatelet therapy was assessed by evaluating aspirin reaction unit (ARU) and P2Y12 reaction units (PRU). Aspirin resistance was defined as ARU ≥550, whereas clopidogrel resistance was defined as PRU ≥235. Blood samples for ARU and PRU were collected from all patients on the day before or on the day of the procedure, immediately before the VBS.

Follow-up Neurovascular Imaging Protocol

Before the procedure, all patients underwent DSA to assess vertebrobasilar artery stenosis. After the procedure, our routine follow-up neurovascular imaging protocol included the following steps: 1) within 48 hours postprocedure, all patients underwent CTA and DWI to detect acute ischemic stroke or thrombotic occlusion of the VBS; 2) approximately 1 month after discharge, the patients were scheduled for a follow-up CTA; 3) at the 6-month mark, patients underwent follow-up imaging with either CTA or DSA, depending on the clinical judgment of the stroke neurologist; and 4) subsequently, follow-up neurovascular imaging was conducted every 12 months, again at the discretion of the stroke neurologist.

Prognosis of VBS

In our study, we assessed the primary prognostic outcomes, focusing on in-stent restenosis and stented-territory ischemic events. In-stent restenosis was defined as a stenosis of >50% when compared with the residual stenosis immediately after VBS during the follow-up period (Fig 1).^17⇓-19 The occurrence of in-stent restenosis was evaluated by using either CTA or DSA.

A stented-territory ischemic event was characterized as an ischemic stroke or a TIA linked to the stented artery after the procedure. Among various symptoms in posterior circulation TIA including dizziness, imbalance, ataxia, diplopia, hemianopia or quadrantanopia, dysarthria, dysphagia, and hearing loss, we defined posterior circulation TIA as the presence of at least 2 concurrent symptoms. Moreover, to avoid overestimation of posterior circulation TIA, we did not classify the following symptoms as indicative of posterior circulation TIA: 1) isolated symptoms (ie, isolated dizziness, isolated dysarthria, isolated hemiparesis, isolated sensory change, isolated dysphagia); 2) ambiguous visual symptoms (ie, subjective diplopia without EOM limitation, transient total blindness, bilateral visual blurring, unusual visual perceptions); 3) TIA symptoms that can occur in the anterior circulation (ie, hemiparesis with dysarthria, hemiparesis with sensory change); and 4) TIA symptoms with uncertain territories (ie, dizziness with nonfocal symptoms, transient generalized weakness, atypical amaurosis fugax).

Stented territory in intracranial and extracranial vertebral artery stent placement was defined as all posterior circulation infarcts except for contralateral posterior inferior cerebellar artery territory. Also, stented territory in basilar artery stent placement was defined as new infarcts in thalamus, midbrain, and pons. All patients underwent DWI within 48 hours postprocedure. Moreover, during the follow-up period, if patients presented with new neurologic symptoms, additional DWI and CTA were immediately conducted to confirm the occurrence of stented-territory ischemic events. Additionally, we conducted an evaluation to determine the etiology of stented-territory infarction, further characterizing the underlying causes and contributing factors.⁷ Artery-to-artery embolism is characterized by the presence of infarcts distal to the stenosed vessel in the territory supplied by the stented artery, as revealed by DWI. These infarcts typically appeared as multiple scattered lesions. Branch atheromatous disease was identified when infarcts were confined to an area adjacent to the stenosed vessel, often attributed to the occlusion of smaller arteries, such as perforating arteries that stem from the stented artery.

The primary prognostic outcomes were independently analyzed by a neurointerventionist (J.-C.R.) and a stroke neurologist (B.J.K.). These assessments were conducted in a blinded fashion (ie, baseline demographics, vascular risk factors, clinical factors, and laboratory findings) except for the information that can be acquired from neurovascular imaging review.

Statistical Analysis

We analyzed the baseline characteristics, vascular risk factors, procedure-related factors, laboratory findings, and primary study outcomes of all enrolled patients. Subsequently, we stratified patients according to the location of their VBS. Statistical significance regarding differences between extracranial and intracranial VBS was assessed by using appropriate statistical tests, such as the Student t test, Mann-Whitney U test, and χ² test, as applicable.

Kaplan-Meier curves were used to assess the incidence of in-stent restenosis and stented-territory ischemic events during the follow-up period. The cumulative incidence of extracranial and intracranial VBS was compared by using the log-rank test. Statistical significance was set at P < .05. All statistical analyses were performed by using the R Software (version 4.2.3; R Foundation for Statistical Computing).