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OBJECTIVE There is a reported elevated risk of cerebral aneurysms in patients with intracranial dural arteriovenous fistulas (dAVFs). However, the natural history, rate of spontaneous regression, and ideal treatment regimen are not well characterized. In this study, the authors aimed to describe the characteristics of patients with dAVFs and intracranial aneurysms and propose a classification system. METHODS The Consortium for Dural Arteriovenous Fistula Outcomes Research (CONDOR) database from 12 centers was retrospectively reviewed. Analysis was performed to compare dAVF patients with (dAVF+ cohort) and without (dAVF-only cohort) concomitant aneurysm. Aneurysms were categorized based on location as a dAVF flow-related aneurysm (FRA) or a dAVF non–flow-related aneurysm (NFRA), with further classification as extra- or intradural. Patients with traumatic pseudoaneurysms or aneurysms with associated arteriovenous malformations were excluded from the analysis. Patient demographics, dAVF anatomical information, aneurysm information, and follow-up data were collected. RESULTS Of the 1077 patients, 1043 were eligible for inclusion, comprising 978 (93.8%) and 65 (6.2%) in the dAVF-only and dAVF+ cohorts, respectively. There were 96 aneurysms in the dAVF+ cohort; 10 patients (1%) harbored 12 FRAs, and 55 patients (5.3%) harbored 84 NFRAs. Dural AVF+ patients had higher rates of smoking (59.3% vs 35.2%, p < 0.001) and illicit drug use (5.8% vs 1.5%, p = 0.02). Sixteen dAVF+ patients (24.6%) presented with aneurysm rupture, which represented 16.7% of the total aneurysms. One patient (1.5%) had aneurysm rupture during follow-up. Patients with dAVF+ were more likely to have a dAVF located in nonconventional locations, less likely to have arterial supply to the dAVF from external carotid artery branches, and more likely to have supply from pial branches. Rates of cortical venous drainage and Borden type distributions were comparable between cohorts. A minority (12.5%) of aneurysms were FRAs. The majority of the aneurysms underwent treatment via either endovascular (36.5%) or microsurgical (15.6%) technique. A small proportion of aneurysms managed conservatively either with or without dAVF treatment spontaneously regressed (6.2%). CONCLUSIONS Patients with dAVF have a similar risk of harboring a concomitant intracranial aneurysm unrelated to the dAVF (5.3%) compared with the general population (approximately 2%–5%) and a rare risk (0.9%) of harboring an FRA. Only 50% of FRAs are intradural. Dural AVF+ patients have differences in dAVF angioarchitecture. A subset of dAVF+ patients harbor FRAs that may regress after dAVF treatment.

Background: Cranial dural arteriovenous fistulas with cortical venous drainage are rare lesions that can present with hemorrhage. A high rate of rebleeding in the early period following hemorrhage has been reported, but published long-term rates are much lower. No study has examined how risk of rebleeding changes over time. Our objective was to quantify the relative incidence of rebleeding in the early and later periods following hemorrhage. Methods: Patients with dural arteriovenous fistula and cortical venous drainage presenting with hemorrhage were identified from the multinational CONDOR (Consortium for Dural Fistula Outcomes Research) database. Natural history follow-up was defined as time from hemorrhage to first treatment, rebleed, or last follow-up. Rebleeding in the first 2 weeks and first year were compared using incidence rate ratio and difference. Results: Of 1077 patients, 250 met the inclusion criteria and had 95 cumulative person-years natural history follow-up. The overall annualized rebleed rate was 7.3% (95% CI, 3.2–14.5). The incidence rate of rebleeding in the first 2 weeks was 0.0011 per person-day; an early rebleed risk of 1.6% in the first 14 days (95% CI, 0.3–5.1). For the remainder of the first year, the incidence rate was 0.00015 per person-day; a rebleed rate of 5.3% (CI, 1.7–12.4) over 1 year. The incidence rate ratio was 7.3 (95% CI, 1.4–37.7; P , 0.026). Conclusions: The risk of rebleeding of a dural arteriovenous fistula with cortical venous drainage presenting with hemorrhage is increased in the first 2 weeks justifying early treatment. However, the magnitude of this increase may be considerably lower than previously thought. Treatment within 5 days was associated with a low rate of rebleeding and appears an appropriate timeframe.

OBJECTIVE Cranial dural arteriovenous fistulas (dAVFs) are often treated with endovascular therapy, but occasionally a multimodality approach including surgery and/or radiosurgery is utilized. Recurrence after an initial angiographic cure has been reported, with estimated rates ranging from 2% to 14.3%, but few risk factors have been identified. The objective of this study was to identify risk factors associated with recurrence of dAVF after putative cure. METHODS The Consortium for Dural Arteriovenous Fistula Outcomes Research (CONDOR) data were retrospectively reviewed. All patients with angiographic cure after treatment and subsequent angiographic follow-up were included. The primary outcome was recurrence, with risk factor analysis. Secondary outcomes included clinical outcomes, morbidity, and mortality associated with recurrence. Risk factor analysis was performed comparing the group of patients who experienced recurrence with those with durable cure (regardless of multiple recurrences). Time-to-event analysis was performed using all collective recurrence events (multiple per patients in some cases). RESULTS Of the 1077 patients included in the primary CONDOR data set, 457 met inclusion criteria. A total of 32 patients (7%) experienced 34 events of recurrence at a mean of 368.7 days (median 192 days). The recurrence rate was 4.5% overall. Kaplan-Meier analysis predicted long-term recurrence rates approaching 11% at 3 years. Grade III dAVFs treated with endovascular therapy were statistically significantly more likely to experience recurrence than those treated surgically (13.3% vs 0%, p = 0.0001). Tentorial location, cortical venous drainage, and deep cerebral venous drainage were all risk factors for recurrence. Endovascular intervention and radiosurgery were associated with recurrence. Six recurrences were symptomatic, including 2 with hemorrhage, 3 with nonhemorrhagic neurological deficit, and 1 with progressive flow-related symptoms (decreased vision). CONCLUSIONS Recurrence of dAVFs after putative cure can occur after endovascular treatment. Risk factors include tentorial location, cortical venous drainage, and deep cerebral drainage. Multimodality therapy can be used to achieve cure after recurrence. A delayed long-term angiographic evaluation (at least 1 year from cure) may be warranted, especially in cases with risk factors for recurrence.

OBJECTIVE Cranial dural arteriovenous fistulas (dAVFs) are rare lesions, hampering efforts to understand them and improve their care. To address this challenge, investigators with an established record of dAVF investigation formed an international, multicenter consortium aimed at better elucidating dAVF pathophysiology, imaging characteristics, natural history, and patient outcomes. This report describes the design of the Consortium for Dural Arteriovenous Fistula Outcomes Research (CONDOR) and includes characterization of the 1077-patient cohort. METHODS Potential collaborators with established interest in the field were identified via systematic review of the literature. To ensure uniformity of data collection, a quality control process was instituted. Data were retrospectively obtained. RESULTS CONDOR comprises 14 centers in the United States, the United Kingdom, the Netherlands, and Japan that have pooled their data from 1077 dAVF patients seen between 1990 and 2017. The cohort includes 359 patients (33%) with Borden type I dAVFs, 175 (16%) with Borden type II fistulas, and 529 (49%) with Borden type III fistulas. Overall, 852 patients (79%) presented with fistula-related symptoms: 427 (40%) presented with nonaggressive symptoms such as tinnitus or orbital phenomena, 258 (24%) presented with intracranial hemorrhage, and 167 (16%) presented with nonhemorrhagic neurological deficits. A smaller proportion (224 patients, 21%), whose dAVFs were discovered incidentally, were asymptomatic. Many patients (85%, 911/1077) underwent treatment via endovascular embolization (55%, 587/1077), surgery (10%, 103/1077), radiosurgery (3%, 36/1077), or multimodal therapy (17%, 184/1077). The overall angiographic cure rate was 83% (758/911 treated), and treatment-related permanent neurological morbidity was 2% (27/1467 total procedures). The median time from diagnosis to follow-up was 380 days (IQR 120–1038.5 days). CONCLUSIONS With more than 1000 patients, the CONDOR registry represents the largest registry of cranial dAVF patient data in the world. These unique, well-annotated data will enable multiple future analyses to be performed to better understand dAVFs and their management.

OBJECTIVE Current evidence suggests that intracranial dural arteriovenous fistulas (dAVFs) without cortical venous drainage (CVD) have a benign clinical course. However, no large study has evaluated the safety and efficacy of current treatments and their impact over the natural history of dAVFs without CVD. METHODS The authors conducted an analysis of the retrospectively collected multicenter Consortium for Dural Arteriovenous Fistula Outcomes Research (CONDOR) database. Patient demographics and presenting symptoms, angiographic features of the dAVFs, and treatment outcomes of patients with Borden type I dAVFs were reviewed. Clinical and radiological follow-up information was assessed to determine rates of new intracranial hemorrhage (ICH) or nonhemorrhagic neurological deficit (NHND), worsening of venous hyperdynamic symptoms (VHSs), angiographic recurrence, and progression or spontaneous regression of dAVFs over time. RESULTS A total of 342 patients/Borden type I dAVFs were identified. The mean patient age was 58.1 ± 15.6 years, and 62% were women. The mean follow-up time was 37.7 ± 54.3 months. Of 230 (67.3%) treated dAVFs, 178 (77%) underwent mainly endovascular embolization, 11 (4.7%) radiosurgery alone, and 4 (1.7%) open surgery as the primary modality. After the first embolization, most dAVFs (47.2%) achieved only partial reduction in early venous filling. Multiple complementary interventions increased complete obliteration rates from 37.9% after first embolization to 46.7% after two or more embolizations, and 55.2% after combined radiosurgery and open surgery. Immediate postprocedural complications occurred in 35 dAVFs (15.2%) and 6 (2.6%) with permanent sequelae. Of 127 completely obliterated dAVFs by any therapeutic modality, 2 (1.6%) showed angiographic recurrence/recanalization at a mean of 34.2 months after treatment. Progression to Borden-Shucart type II or III was documented in 2.2% of patients and subsequent development of a new dAVF in 1.6%. Partial spontaneous regression was found in 22 (21.4%) of 103 nontreated dAVFs. Multivariate Cox regression analysis demonstrated that older age, NHND, or severe venous-hyperdynamic symptoms at presentation and infratentorial location were associated with worse prognosis. Kaplan-Meier curves showed no significant difference for stable/improved symptoms survival probability in treated versus nontreated dAVFs. However, estimated survival times showed better trends for treated dAVFs compared with nontreated dAVFs (288.1 months vs 151.1 months, log-rank p = 0.28). This difference was statistically significant for treated dAVFs with 100% occlusion (394 months, log-rank p < 0.001). CONCLUSIONS Current therapeutic modalities for management of dAVFs without CVD may provide better symptom control when complete angiographic occlusion is achieved.

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 the 13 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.

OBJECTIVE The risk-to-benefit profile of treating an unruptured high-grade dural arteriovenous fistula (dAVF) is not clearly defined. The aim of this multicenter retrospective cohort study was to compare the outcomes of different interventions with observation for unruptured high-grade dAVFs. METHODS The authors retrospectively reviewed dAVF patients from 12 institutions participating in the Consortium for Dural Arteriovenous Fistula Outcomes Research (CONDOR). Patients with unruptured high-grade (Borden type II or III) dAVFs were included and categorized into four groups (observation, embolization, surgery, and stereotactic radiosurgery [SRS]) based on the initial management. The primary outcome was defined as the modified Rankin Scale (mRS) score at final follow-up. Secondary outcomes were good outcome (mRS scores 0–2) at final follow-up, symptomatic improvement, all-cause mortality, and dAVF obliteration. The outcomes of each intervention group were compared against those of the observation group as a reference, with adjustment for differences in baseline characteristics. RESULTS The study included 415 dAVF patients, accounting for 29, 324, 43, and 19 in the observation, embolization, surgery, and SRS groups, respectively. The mean radiological and clinical follow-up durations were 21 and 25 months, respectively. Functional outcomes were similar for embolization, surgery, and SRS compared with observation. With observation as a reference, obliteration rates were higher after embolization (adjusted OR [aOR] 7.147, p = 0.010) and surgery (aOR 33.803, p < 0.001) and all-cause mortality was lower after embolization (imputed, aOR 0.171, p = 0.040). Hemorrhage rates per 1000 patient-years were 101 for observation versus 9, 22, and 0 for embolization (p = 0.022), surgery (p = 0.245), and SRS (p = 0.077), respectively. Nonhemorrhagic neurological deficit rates were similar between each intervention group versus observation. CONCLUSIONS Embolization and surgery for unruptured high-grade dAVFs afforded a greater likelihood of obliteration than did observation. Embolization also reduced the risk of death and dAVF-associated hemorrhage compared with conservative management over a modest follow-up period. These findings support embolization as the first-line treatment of choice for appropriately selected unruptured Borden type II and III dAVFs.

Background and Purpose— The VERiTAS (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke) study demonstrated posterior circulation distal flow status, determined by quantitative magnetic resonance angiography, is a robust predictor of vertebrobasilar stroke risk in patients with symptomatic atherosclerotic vertebrobasilar disease. Flow-compromised high-risk patients may benefit from flow-restoring endovascular procedures, such as submaximal angioplasty. In this study, we examine the cost-effectiveness of quantitative magnetic resonance angiography screening to identify patients who may benefit from submaximal angioplasty to restore vertebrobasilar flow. Methods— A Markov model was created comparing a no screening strategy with standard medical management alone and a screening strategy involving quantitative magnetic resonance angiography imaging and submaximal angioplasty for treatable patients with low vertebrobasilar flow for a 30-year time horizon. Outcomes included quality-adjusted life years (QALY) and lifetime costs. Rates of stroke and death were obtained from VERiTAS data, and disability rates and costs were derived from VERiTAS and the literature. A sensitivity analysis was performed with periprocedural stroke rate from angioplasty the primary variable of interest. Results— At a 6% periprocedural stroke risk, the screening strategy saved an average of 0.364 QALYs per patient and a lifetime cost savings of $7312 versus the no screening strategy. Among patients with low flow suitable for intervention, the benefit was substantially higher, averaging 1.485 QALYs saved and lifetime cost savings of $21 294. Across the entire cohort, QALY savings were observed at the end of the first year and economic savings at year 6. The benefit of screening declined at higher periprocedural risk. Conclusions— Quantitative magnetic resonance angiography screening and submaximal angioplasty with 6% periprocedural risk in suitable patients are cost effective both in terms of QALY and lifetime costs for patients with symptomatic vertebrobasilar occlusive disease. With potential health and economic savings, a clinical trial examining the periprocedural risk of submaximal angioplasty is warranted. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00590980.

Background and Purpose— Cerebral hypoperfusion symptoms (defined as symptoms related to change in position, effort or exertion, or recent change in antihypertensive medication) have been used in stroke studies as a surrogate for detecting hemodynamic compromise. However, the validity of these symptoms in identifying flow compromise in patients has not been well established. We examined whether hypoperfusion symptoms correlated with quantitative measurements of flow compromise in the prospective, observational VERiTAS study (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke). Methods— VERiTAS enrolled patients with recent vertebrobasilar transient ischemic attack or stroke and ≥50% atherosclerotic stenosis or occlusion in vertebral or basilar arteries. Hemodynamic status using vertebrobasilar large vessel flow was measured using quantitative magnetic resonance angiography, and patients were designated as low, borderline, or normal flow based on distal territory regional flow, incorporating collateral capacity. The presence of qualifying event hypoperfusion symptoms was assessed relative to the quantitatively determined flow status (normal versus borderline/low) and also examined as a predictor of subsequent stroke risk. Results— Of the 72 enrolled subjects, 66 had data on hypoperfusion symptoms available. On initial quantitative magnetic resonance angiography designation, 43 subjects were designated as normal flow versus 23 subjects designated as low flow (n=16) or borderline flow (n=7). Of these, 5 (11.6%) normal flow and 3 (13.0%) low/borderline flow subjects reported at least one qualifying event hypoperfusion symptom ( P =0.99, Fisher exact test). Hypoperfusion symptoms had a positive predictive value of 37.5% and negative predictive value of 65.5% for low/borderline flow status. Compared with flow status, which strongly predicted subsequent stroke risk, hypoperfusion symptoms were not associated with stroke outcome ( P =0.87, log-rank test). Conclusions— These results suggest that hypoperfusion symptoms alone correlate poorly with actual hemodynamic compromise as assessed by quantitative magnetic resonance angiography and subsequent stroke risk in vertebrobasilar disease, and are not a reliable surrogate for flow measurement. Clinical Trial Registration— URL: https://www.clinicaltrials.gov . Unique identifier: NCT00590980.

Despite concerns regarding hypoperfusion in patients with large-artery occlusive disease, strict blood pressure (BP) control has become adopted as a safe strategy for risk reduction of stroke. 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.The VERiTAS study enrolled patients with recent vertebrobasilar (VB) transient ischemic attack or stroke and ≥50% atherosclerotic stenosis or occlusion of vertebral or basilar arteries. Hemodynamic status was designated as low or normal based on quantitative magnetic resonance angiography. Patients underwent standard medical management and follow-up for primary outcome event of VB territory stroke. Mean BP during follow-up (140/90 versus ≥140/90 mm Hg) and flow status were examined relative to subsequent stroke risk using Cox proportional hazards analysis.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 of140/90 mm Hg. The BP groups were largely comparable for baseline demographics, risk factors, and stenosis severity. Comparing subgroups stratified by BP and hemodynamic status, we found that patients with both low flow and BP140/90 mm Hg (n = 10) had the highest risk of subsequent stroke, with hazard ratio of 4.5 (confidence interval 1.3-16.0, P = .02), compared with the other subgroups combined.Among a subgroup of patients with VB disease and low flow, strict BP control (BP140/90) may increase the risk of subsequent stroke.

Introduction: Distal territory blood flow is independently associated with subsequent strokes in symptomatic vertebrobasilar atherosclerotic disease. We aimed to assess infarct patterns in relation to hemodynamic status in the prospective Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) study. Methods: Distal territory blood flow was measured using quantitative magnetic resonance angiography (MRA) in 72 patients with symptomatic atherosclerotic vertebrobasilar disease, and then dichotomized into normal (n = 54) and low (n = 18) flow. Patients were followed longitudinally on standard medical management. Two observers blinded to flow status independently reviewed the imaging performed at the time of subsequent strokes, in order to adjudicate the likely mechanism based on infarct patterns. The frequency of stroke mechanisms was qualitatively compared based on flow status. Results: During a median follow-up period of 23 months, 10/72 patients had a subsequent stroke; 5 of these had low distal flow. Infarct patterns were adjudicated to be consistent with hemodynamic (n = 2), embolic (n = 4), and junctional plaque/perforator (n = 4) infarcts. Hemodynamic infarcts were seen in 40% (2/5) low-flow patients, in comparison to 0% (0/5) normal-flow patients. Conclusion: In contrast to normal-flow patients, those with low distal flow seem to be uniquely susceptible to hemodynamic infarctions, although other patterns of infarction can also be seen in these hemodynamically impaired patients.

Introduction: Hypoperfusion symptoms, defined as symptoms related to change in position (i.e. supine to seated), effort or exertion, or recent change in antihypertensive medication have been used in stroke studies as a surrogate for detecting hemodynamic compromise. However, the validity of these symptoms in identifying flow compromise in patients has not been well established. We examined whether hypoperfusion symptoms correlated with quantitative evaluation of flow compromise in the prospective observational Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) study. Methods: VERiTAS enrolled patients with recent vertebrobasilar TIA or stroke and ≥50% atherosclerotic stenosis or occlusion in vertebral and/or basilar arteries. Hemodynamic status using large vessel flow in the vertebrobasilar territory was measured using quantitative magnetic resonance angiography (QMRA), and patients were designated as low, borderline or normal flow based on distal territory regional flow, incorporating collateral capacity, as previously reported. The presence of qualifying event hypoperfusion symptoms was assessed relative to the quantitatively determined flow status (normal vs borderline/low), and also examined as a predictor of subsequent stroke risk. Results: Of the 72 enrolled subjects, 66 had data on hypoperfusion symptoms available. On initial QMRA designation, 43 subjects were designated as normal flow vs. 23 subjects designated as low flow (n=16) or borderline (n=7). Of these, 5 (11.6%) normal flow and 3 (13.0%) low/borderline flow subjects reported at least one qualifying event hypoperfusion symptom (p=0.99, Fisher’s exact test). Hypoperfusion symptoms had a positive predictive value of 37.5% and negative predictive value of 65.5% for low/borderline flow status. Compared to flow status, which strongly predicted subsequent stroke risk, hypoperfusion symptoms were not associated with stroke outcome (p=0.87, log rank test). Conclusions: These results suggest that hypoperfusion symptoms alone correlate poorly with actual hemodynamic compromise, and subsequent stroke risk in vertebrobasilar disease, and are not a reliable surrogate for flow measurement.

Objectives: Patients with symptomatic atherosclerotic vertebrobasilar disease are at high risk for recurrent stroke and we have demonstrated that distal flow status is independently associated with this risk. Our aim was to assess the mechanism of recurrent strokes in these patients related to their distal flow status. Methods: Patients with symptomatic atherosclerotic vertebrobasilar disease were enrolled in a prospective longitudinal cohort study (VERiTAS) with a median follow-up of 23 months. Large-vessel flow in the posterior circulation distal to the stenosis and/or occlusion was measured on quantitative MR angiography and dichotomized into normal or low flow. Three observers, who were blinded to the distal flow status, independently reviewed the imaging done at the time of the recurrent stroke to classify the most likely stroke mechanism. Results: Ten out of 72 enrolled patients had a recurrent stroke in the posterior circulation. Four patients were determined to have embolic infarcts, four patients had infarcts caused by plaques that occluded a branch or perforating artery (junctional plaques), and two patients had imaging that suggested hemodynamic infarction. Five of the ten patients with recurrent strokes had low distal flow. Of these, two patients had hemodynamic infarcts, one patient had an embolic infarct, and two patients had a junctional plaque. None of the five patients with normal flow had hemodynamic infarcts, three patients had embolic infarcts, and two patients had a junctional plaque. Conclusion: Despite the small numbers, there seems to be a higher risk of hemodynamic infarction in patients with low flow distal to symptomatic vertebrobasilar disease than in the presence of normal distal flow. This would confirm the hypothesis that in addition to embolic strokes and those related to junctional plaque, patients with low distal flow are at risk for hemodynamic infarction. Further studies are required to determine whether flow measurements could be used to select patients who may benefit from endovascular treatment of atherosclerotic vertebrobasilar disease.

Background: Fractional flow across an atherosclerotic lesion measured with TOF-MRA signal intensity ratio (SIR) may be used to gauge hemodynamic severity and to predict subsequent stroke. The degree of flow impairment may also be ascertained by quantitative MRA (QMRA). We analyzed performance of these noninvasive imaging parameters to estimate risk of subsequent posterior circulation events in VERiTAS. Methods: TOF-MRA data and QMRA were simultaneously acquired in VERiTAS. SIR were derived from TOF source images and normalized for analysis with volume flow ratios (VFR) on QMRA at standard anatomical landmarks and across the maximal stenosis. Statistics analyzed the correlation between SIR and VFR, and the ability of each to predict clinical events. Results: 72 subjects (mean age 65.6±10.3 years, 32 (44%) women) with posterior circulation atherosclerosis were enrolled in VERiTAS. Posterior communicating artery (PCOMM) flow to the posterior circulation was detected in 85% on the right, in 86% on the left, with bilateral PCOMM flow in 78%. Fractional flow measures or SIR across the maximal stenotic lesion evident on TOF MRA was reduced in 43%, increased in 16%, with no change in 40%. SIR from the proximal to distal basilar artery segments increased in 62%, was unchanged in 33% and decreased in 4% of cases. SI and VFR exhibited limited correlation at corresponding arterial segments. QMRA VFR indicative of low distal flow status predicted subsequent clinical events, unlike SIR. Conclusions: Evaluation of hemodynamics in posterior circulation atherosclerosis reveals superiority of QMRA to SIR in prospectively predicting recurrent ischemia. Collateral circulation, tandem disease and unique aspects of vertebrobasilar atherosclerosis likely influence the utility of SIR on TOF MRA.

Introduction: Despite theoretical 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, flow, and risk of subsequent stroke in the prospective Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) Study. Hypothesis: Strict BP control may be less efficacious and safe in flow compromised patients with symptomatic vertebrobasilar (VB) disease. Methods: VERiTAS enrolled patients with recent VB TIA or stroke and ≥50% atherosclerotic stenosis or occlusion of vertebral or basilar arteries. Hemodynamic status using large vessel flow in the VB territory was designated as low or normal flow using quantitative MRA. Patients underwent standard medical management and follow-up for primary outcome event of VB territory stroke. Mean SBP during follow-up ( Results: The 72 enrolled subjects had an average of 3.8±1.2 BP recordings over the 20 ±8 months of follow-up; 40 (56%) had mean SBP of Conclusion: Among a subgroup of patients with VB disease and low flow, strict BP control (SBP

Introduction: The role of regional hypoperfusion as an important contributor to stroke risk in atherosclerotic vertebrobasilar (VB) disease has recently been confirmed by the observational Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) Study. We examined the stability of hemodynamic status over time and relationship to stroke risk in patients followed in this prospective cohort. Methods: VERiTAS enrolled patients with recent VB TIA or stroke and ≥50% atherosclerotic stenosis or occlusion of vertebral and/or basilar arteries. Large vessel flow in the vertebrobasilar territory was assessed using quantitative MRA, and patients were designated as low flow 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 VB territory stroke. QMRA 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 survival analysis. Results: Of 72 enrolled subjects, 50, 45 and 28 had follow-up QMRA at 6, 12 and 24 months respectively. 18 (25%) were characterized as low flow at baseline, 10% at 6 m, 20 % at 12m and 11% at 24m. Over 18±7months of follow-up, 7 of the 12 low flow patients (58%) with follow-up imaging had improved their flow status (low to normal) while only 3 of 44 normal flow patients (7%) had worsened. Baseline flow status has previously been demonstrated to be an independent stroke risk predictor; flow status at latest follow-up and prior to event remained a strong predictor of subsequent stroke (HR 4.9, CI 1.4 to16.9, p=0.01). Conclusions: There is potential both for improvement and worsening of hemodynamics in patients with atherosclerotic VB disease; improvement, likely attributable to development of collateral supply, was evident more frequently than worsening, presumably due to progression of disease. Flow status, both at baseline and over time, remains a robust risk factor for subsequent stroke, thus serving as an important prognostic marker.

Background and Purpose— Atherosclerotic vertebrobasilar disease is an important cause of posterior circulation stroke. To examine the role of hemodynamic compromise, a prospective multicenter 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 vertebrobasilar transient ischemic attack or stroke and ≥50% atherosclerotic stenosis or occlusion in vertebral or basilar arteries (BA) were enrolled. Large-vessel flow in the vertebrobasilar territory was assessed using quantitative MRA. Results— The cohort (n=72; 44% women) 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 P 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 with 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.

Introduction: Atherosclerotic vertebrobasilar disease (VBD) is a significant etiology of posterior circulation stroke. In addition to thromboembolism, regional hypoperfusion is considered an important potential contributor to stroke risk. To examine the role of hemodynamic compromise in VBD, a prospective observational multi-center study, Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS), has recently been conducted. Here we report baseline features and vessel flow measurements from the study cohort. Methods: Baseline demographic and clinical data was collected in patients with recent vertebrobasilar TIA or stroke and ≥50% atherosclerotic stenosis or occlusion in vertebral and/or basilar arteries. Large vessel flow in the vertebrobasilar territory was assessed using quantitative MRA (QMRA). Results: The cohort (n=75, 56% male) had a mean age of 65.5 (range 40 to 90) years; two thirds presented with ischemic stroke. Hypertension (93%) and hyperlipidemia (79%) were the most prevalent vascular risk factors. Vertebral and basilar artery flows correlated negatively with degree of stenosis in the affected vessel, and positively to the minimal diameter at the site of stenosis (p Conclusions: Flow in stenotic posterior circulation vessels correlate with residual diameter and stenosis and drop significantly in the setting of tandem disease. However, distal flow status, incorporating collateral capacity, is not well predicted by the severity or location of the disease. Final clinical outcome results from the ongoing VERiTAS study will further clarify the relevance of anatomic stenosis and hemodynamic assessment to predicting stroke risk in patients with vertebrobasilar disease.

Background Over one-third of ischaemic strokes occur in the posterior circulation, and a leading cause is atherosclerotic vertebrobasilar disease. Symptomatic vertebrobasilar disease carries a high annual recurrent stroke risk, averaging 10–15% per year. Endovascular angioplasty and stenting are increasingly used 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 vertebrobasilar disease is strongly related to haemodynamic compromise, which can be measured noninvasively using quantitative magnetic resonance angiography. Methods/study design The Vertebrobasilar Flow Evaluation and Risk of Transient Ischaemic Attack and Stroke (VERiTAS) study, a prospective multicentre 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 quantitative magnetic resonance angiography are at higher stroke risk. The study will recruit 80 patients at six sites in North America over 4-years. Upon enrollment, subjects will undergo haemodynamic assessment with blinded quantitative magnetic resonance angiography to assess large vessel flow in the vertebrobasilar territory, and be prospectively designated as compromised or normal flow. Patients will be re-imaged with quantitative magnetic resonance angiography at 6-, 12-, and 24-months, and followed for 12–24-months for the primary end-point of stroke in the vertebrobasilar territory. Conclusion The VERiTAS study is the first prospective study of haemodynamics 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.