for the Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) Study Group IMPORTANCE Atherosclerotic vertebrobasilar (VB) occlusive disease is a significant etiology of posterior circulation stroke, with regional hypoperfusion as an important potential contributor to stroke risk.OBJECTIVE To test the hypothesis that, among patients with symptomatic VB stenosis or occlusion, those with distal blood flow compromise as measured by large-vessel quantitative magnetic resonance angiography (QMRA) are at higher risk of subsequent posterior circulation stroke. DESIGN, SETTING, AND PARTICIPANTSA prospective, blinded, longitudinal cohort study was conducted at 5 academic hospital-based centers in the United States and Canada; 82 patients from inpatient and outpatient settings were enrolled. Participants with recent VB transient ischemic attack or stroke and 50% or more atherosclerotic stenosis or occlusion in vertebral and/or basilar arteries underwent large-vessel flow measurement in the VB territory using QMRA. Physicians performing follow-up assessments were blinded to QMRA flow status. Follow-up included monthly telephone calls for 12 months and biannual clinical visits (for a minimum of 12 months, and up to 24 months or the final visit). Enrollment took place from

Background Over one third of ischemic strokes occur in the posterior circulation, a leading cause of which is atherosclerotic vertebrobasilar disease (VBD). Symptomatic VBD carries a high annual recurrent stroke risk, averaging 10–15% per year. Endovascular angioplasty and stenting are increasingly employed, but carry risks, and the benefit remains unproven. Determining stroke predictors in this population is critical to identifying high risk patients for future trials of intervention. Preliminary studies indicate that stroke risk in VBD is strongly related to hemodynamic compromise, which can be measured noninvasively using quantitative magnetic resonance angiography (QMRA). Methods/Study Design The VERiTAS Study, a prospective multi-center NIH funded observational study of symptomatic vertebrobasilar stenosis (≥ 50%) or occlusion, is designed to test the hypothesis that patients demonstrating compromised blood flow as assessed by QMRA are at higher stroke risk. The study will recruit 80 patients at 6 sites in North America over four years. Upon enrollment, subjects will undergo hemodynamic assessment with blinded QMRA to assess large vessel flow in the vertebrobasilar territory, and be prospectively designated as compromised or normal flow. Patients will be reimaged with QMRA at 6, 12 and 24 months, and followed for 12 to 24 months for the primary endpoint of stroke in the vertebrobasilar territory. Conclusion VERiTAS is the first prospective study of hemodynamics and stroke risk in the posterior circulation. The results may impact the selection criteria for interventional candidates and also define a low risk population in whom the risks of invasive interventions would be unnecessary.

Background and Purpose Atherosclerotic vertebrobasilar (VB) disease is an important etiology of posterior circulation stroke. To examine the role of hemodynamic compromise, a prospective multi-center study, Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS), was conducted. Here we report clinical features and vessel flow measurements from the study cohort. Methods Patients with recent VB TIA or stroke and ≥50% atherosclerotic stenosis or occlusion in vertebral (VA) and/or basilar (BA) arteries were enrolled. Large vessel flow in the VB territory was assessed using quantitative MRA. Results The cohort (n=72, 44% female) had a mean age of 65.6 years; 72% presented with ischemic stroke. Hypertension (93%) and hyperlipidemia (81%) were the most prevalent vascular risk factors. BA flows correlated negatively with percentage stenosis in the affected vessel, and positively to the minimal diameter at the stenosis site (p<0.01). A relative threshold effect was evident, with flows dropping most significantly with ≥80% stenosis/occlusion (p<0.05). Tandem disease involving the BA and either/both VAs had the greatest negative impact on immediate downstream flow in the BA (43 ml/min vs. 71 ml/min, p=0.01). Distal flow status assessment, based on an algorithm incorporating collateral flow by examining distal vessels (BA and posterior cerebral arteries), correlated neither with multifocality of disease nor severity of the maximal stenosis. Conclusions Flow in stenotic posterior circulation vessels correlates with residual diameter, and drops significantly with tandem disease. However, distal flow status, incorporating collateral capacity, is not well predicted by the severity or location of the disease.

Background Despite concerns regarding hypoperfusion in patients with large artery occlusive disease, strict blood pressure (BP) control has become adopted as a safe strategy for stroke risk reduction.We examined the relationship between BP control, blood flow, and risk of subsequent stroke in the prospective Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) Study. Methods VERiTAS enrolled patients with recent vertebrobasilar (VB) TIA or stroke and ≥50% atherosclerotic stenosis/occlusion of vertebral or basilar arteries. Hemodynamic status was designated as low or normal based on quantitative MRA. Patients underwent standard medical management and follow-up for primary outcome event of VB territory stroke. Mean BP during follow-up (<140/90 vs. ≥140/90 mm Hg) and flow status were examined relative to subsequent stroke risk using Cox proportional hazards analysis. Results The 72 subjects had an average of 3.8±1.2 BP recordings over 20±8 months of follow-up; 39 (54%) had mean BP of <140/90 mm Hg. The BP groups were largely comparable for baseline demographics, risk factors, and stenosis severity. Comparing subgroups stratified by BP and hemodynamic status, patients with both low flow and BP <140/90 mm Hg (n=10) had the highest risk of subsequent stroke with HR 4.5 (CI 1.3-16.0, p=0.02) compared to the other subgroups combined. Conclusions Among a subgroup of patients with VB disease and low flow, strict BP control (BP <140/90) may increase the risk of subsequent stroke.

Background and Purpose: The role of regional hypoperfusion as a contributor to stroke risk in atherosclerotic vertebrobasilar disease has recently been confirmed by the observational VERiTAS (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke) Study. We examined the stability of hemodynamic status over time and its relationship to stroke risk in patients from this prospective cohort. Methods: VERiTAS enrolled patients with recently symptomatic ≥50% atherosclerotic stenosis/occlusion of vertebral and/or basilar arteries. Large vessel flow in the vertebrobasilar territory was assessed using quantitative magnetic resonance angiography, and patients were designated as low or normal flow based on distal territory regional flow, incorporating collateral capacity. Patients underwent standard medical management and follow-up for primary outcome event of vertebrobasilar territory stroke. Quantitative magnetic resonance angiography imaging was repeated at 6, 12, and 24 months. Flow status over time was examined relative to baseline and relative to subsequent stroke risk using a cause-specific proportional hazard model, with flow status treated as a time-varying covariate. Mean blood pressure was examined to assess for association with changes in flow status. Results: Over 19±8 months of follow-up, 132 follow-up quantitative magnetic resonance angiography studies were performed in 58 of the 72 enrolled patients. Of the13 patients with serial imaging who had low flow at baseline, 7 (54%) had improvement to normal flow at the last follow-up. Of the 45 patients who had normal flow at baseline, 3 (7%) converted to low flow at the last follow-up. The mean blood pressure did not differ in patients with or without changes in flow status. The time-varying flow status remained a strong predictor of subsequent stroke (hazard ratio,10.3 [95% CI, 2.2–48.7]). Conclusions: There is potential both for improvement and worsening of hemodynamics in patients with atherosclerotic vertebrobasilar disease. Flow status, both at baseline and over time, is a risk factor for subsequent stroke, thus serving as an important prognostic marker. REGISTRATION: URL: https://clinicaltrials.gov . Unique identifier: NCT00590980.