Collateral Capacity Research Articles

High relative cerebral blood volume is associated with good long term clinical outcomes in acute ischemic stroke: a retrospective cohort study

BackgroundEndovascular therapy for acute ischemic stroke has been shown to be highly effective in selected patients. However, the ideal criteria for patient selection are still debated. It is well known that collateral flow is an important factor, but the assessment is often subjective and time-consuming. Relative cerebral blood volume (rCBV) is a putative indicator of collateral capacity and can be quickly and easily determined by automated quantitative analysis. We investigated the relationship between rCBV of the affected region and clinical outcome in patients with acute ischemic stroke after endovascular therapy.MethodsWe conducted a retrospective study on consecutive patients between January 2017 and May 2019. Patients with acute ischemic stroke of the anterior circulation who underwent imaging including computed tomography perfusion and were treated with mechanical thrombectomy (MT) were eligible for inclusion. rCBV was calculated automatically with RAPID software by dividing the average cerebral blood volume (CBV) of the affected region (time-to-maximum (Tmax) > 6 s) by the CBV of the unaffected contralateral side. The primary outcome was determined by the modified Rankin Scale (mRS) after 90 days. Good clinical outcome was defined as mRS ≤ 2. We compared means, performed mono- and multivariate logistical regression and calculated a receiver operating characteristic (ROC)-analysis to determine the ideal cutoff value to predict clinical outcomes.Results155 patients were enrolled in this study. 66 patients (42.58%) had good clinical outcomes. Higher rCBV was associated with good clinical outcome (p < 0.001), even after adjustment for the patients’ status according to mRS and National Institute of Health Stroke Scale (NIHSS) age and Alberta stroke program early computed tomography score (ASPECTS) at baseline (p = 0.006). ROC-analysis revealed 0.650 (confidence interval: 0.616–0.778) as the optimal cutoff value.ConclusionHigher rCBV at baseline is associated with good clinical long-term outcomes in patients with acute ischemic stroke treated by MT. In this study we provide the biggest collective so far that gives evidence that rCBV can be a valuable tool to identify patients who might benefit from MT and are able give a threshold to help to offer patients MT in borderline cases.

Assessing the Challenges affecting SMEs' access to Bank Loans in Zambia, a case of Lusaka Town Centre

This research aimed to evaluate the difficulties SMEs face in obtaining credit from banking institutions. Using a descriptive research design, primary data was collected from various SME respondents through a structured, self-administered questionnaire. The literature review, sourced from journals and other materials, provided a deeper understanding of the subject. Data analysis was conducted using frequency tables and descriptive graphics with the assistance of SPSS for data entry, coding, and analysis of quantitative data from closed-ended questions. The findings revealed that while access to credit positively influenced SME performance by enabling proprietors to increase business stocks or acquire assets, significant challenges impeded access to credit. These challenges included inadequate collateral, limited borrowing capacity, high interest rates and processing fees, and stringent terms and procedures. These barriers hindered SMEs' ability to expand, improve cash flow for reinvestment, and ultimately reduced profitability. To address these issues, the researcher recommended that the government, through the Bank of Zambia, consider capping interest rates for SMEs or providing subsidized loans. Additionally, they suggested strengthening the Zambia Credit Guarantee Scheme Limited to offer loan guarantees for SMEs, recognizing their crucial role in the economy. The study recommended that Government create interest Rate Caps where the government should work with the Bank of Zambia to establish an interest rate ceiling for SMEs, making loans more affordable and promoting business growth and stability. Develop subsidized loan programs for SMEs to lessen the impact of high interest rates and processing fees, thereby helping them secure the capital needed for expansion and operational improvements. Enhancing the Credit Guarantee Scheme requires you to improve the structure and operations of the Zambia Credit Guarantee Scheme Limited to provide SMEs with easier access to loan guarantees, addressing issues related to inadequate collateral and limited borrowing capacity.

Assessing the Challenges Affecting SMEs' Access to Bank Loans in Zambia, a Case of Lusaka Town Centre

This research aimed to evaluate the difficulties SMEs face in obtaining credit from banking institutions. Using a descriptive research design, primary data was collected from various SME respondents through a structured, self-administered questionnaire. The literature review, sourced from journals and other materials, provided a deeper understanding of the subject. Data analysis was conducted using frequency tables and descriptive graphics with the assistance of SPSS for data entry, coding, and analysis of quantitative data from closed-ended questions. The findings revealed that while access to credit positively influenced SME performance by enabling proprietors to increase business stocks or acquire assets, significant challenges impeded access to credit. These challenges included inadequate collateral, limited borrowing capacity, high interest rates and processing fees, and stringent terms and procedures. These barriers hindered SMEs' ability to expand, improve cash flow for reinvestment, and ultimately reduced profitability. To address these issues, the researcher recommended that the government, through the Bank of Zambia, consider capping interest rates for SMEs or providing subsidized loans. Additionally, they suggested strengthening the Zambia Credit Guarantee Scheme Limited to offer loan guarantees for SMEs, recognizing their crucial role in the economy. The study recommended that Government create interest Rate Caps where the government should work with the Bank of Zambia to establish an interest rate ceiling for SMEs, making loans more affordable and promoting business growth and stability. Develop subsidized loan programs for SMEs to lessen the impact of high interest rates and processing fees, thereby helping them secure the capital needed for expansion and operational improvements. Enhancing the Credit Guarantee Scheme requires you to improve the structure and operations of the Zambia Credit Guarantee Scheme Limited to provide SMEs with easier access to loan guarantees, addressing issues related to inadequate collateral and limited borrowing capacity.

Risk Management with Variable Capital Utilization and Time-Varying Collateral Capacity

We build a risk management model that incorporates variable capital utilization and time-varying collateral capacity. The former lets firms optimally choose capital utilization, and hence production, which affects capital depreciation and risk exposure. The latter means firms’ ability to borrow and hedge increases with expected earnings and thus utilization. Calibrated solutions show both ingredients matter for firm value. We test the novel model predictions using a new data set of oil and gas producers. Consistent with model predictions, we find utilization is negatively correlated with firm liquidity, while hedging is positively correlated with liquidity and expected profitability. This paper was accepted by Lukas Schmid, finance. Funding: Lu and Vij acknowledge financial support from the Terry-Sanford Research Award, University of Georgia. Supplemental Material: The online appendices and data files are available at https://doi.org/10.1287/mnsc.2022.00415 .

Effect of collateral circulation in patients with multiple craniocervical artery stenoses.

Based on previous findings, collateral circulation in the brain is vital in mitigating cerebral ischemia's effects and influencing stroke risk. This retrospective study examined collateral circulation, admission ischemic stroke status, and long-term recurrence in patients with multiple craniocervical artery stenoses. Consecutive symptomatic internal carotid artery (ICA) stenosis patients from the First Affiliated Hospital of Soochow University were recruited. Baseline data including medical histories and neurological function at admission were collected. Imaging techniques assessed collateral compensative capacity. Multivariate logistic regression analysis was used to investigate the association between collateral circulation and case status. A total of 559 patients with symptomatic ICA stenosis were included, among whom 153 (27.4%) had concurrent moderate to severe vertebro-basilar artery (VBA) stenosis. Dizziness, weakness/numbness, and slurring of speech were the primary symptoms in all patients. Over 36 months, 71 (12.7%) patients experienced a recurrence of acute ischemic stroke (AIS). In multivariate analysis, collateral circulation was found to be negatively associated with AIS (regional leptomeningeal collateral [rLMC] scores: OR: 0.798, 95% CI: 0.743-0.857, p < 0.001; Tan scores: OR: 0.478, 95% CI: 0.336-0.679, p < 0.001). Meanwhile, the collateral circulation scores were significantly associated with the recurrence of AIS within 3 years (rLMC scores: OR: 0.926, 95% CI: 0.860-0.997, p = 0.042; Tan scores: OR: 0.467, 95% CI: 0.306-0.712, p < 0.001). Most associations remained significant in the subgroup of patients with VBA stenosis. Favorable collateral circulation in multiple craniocervical artery stenosis patients reduced long-term ischemic event recurrence. Stratifying treatment risks is essential for optimizing outcomes.

Incomplete circle of Willis as a risk factor for intraoperative ischemic events during carotid endarterectomies performed under regional anesthesia - A prospective case-series.

The role of the willisian collaterals during carotid endarterectomies (CEAs) is a debated issue. The aim of the present work was to test whether an incomplete or non-functional circle of Willis (CoW) is a risk factor for ischemic events during CEA. CEAs were performed under local anesthesia. Patients were considered symptomatic (SY) if neurological signs appeared after the cross-clamping phase. In SY patients shunt insertion was performed. CoW on CT angiograms (CTa) were analyzed offline and categorized as non-functional (missing or hypoplastic collaterals) or functional collaterals by three neuroradiologists. Near-infrared spectroscopy (NIRS) was performed throughout the procedure. Based on CTa, 67 incomplete circles were found, 54 were asymptomatic (ASY) and 13 were SY. No complete CoW was found among the SY patients. Significant differences could be detected between incomplete and complete circles between ASY and SY groups (Chi-square: 6.08; p = 0.013). The anterior communicating artery was missing or hypoplastic in 5/13 SY cases. There were no cases of the non-functional anterior communicating arteries in the ASY group (Chi-square: 32.9; p = 10-8). A missing or non-functional bilateral posterior communicating artery was observed in 9/13 SY and in 9/81 ASY patients (Chi-square: 24.4; p = 10-7). NIRS had a sensitivity of 76.9% and a specificity of 74.5% in detecting neurological symptoms. Collateral ability of the CoW may be a risk factor for ischemic events during CEAs. Further studies should delineate whether the preoperative assessment of collateral capacity may be useful in decision-making about shunt use during CEA.

Thrombectomy alone vs thrombectomy with over 2/3-dose intravenous thrombolysis pretreatment in the DIRECT-MT trial

BackgroundThe DIRECT-MT trial showed that endovascular thrombectomy (EVT) alone was noninferior to EVT preceded by intravenous alteplase. However, the infusion of intravenous alteplase was uncompleted before the initiation of EVT in most cases of this trial. Therefore, the additional benefit and risk of over 2/3-dose intravenous alteplase pretreatment remain to be assessed. MethodsWe assessed patients with acute anterior circulation ischemic stroke who received EVT alone or with over 2/3-dose intravenous alteplase pretreatment from the DIRECT-MT trial. Patients were assigned to the thrombectomy-alone group and the alteplase pretreatment group. The primary outcome was the distribution of modified Rankin Scale (mRS) at 90 days. The interaction of treatment allocation and collateral capacity was assessed. ResultsA total of 393 patients (thrombectomy alone: 315; alteplase pretreatment: 78) were identified. The thrombectomy alone was comparable with alteplase pretreatment prior to the thrombectomy on the distribution of mRS at 90 days without significant effect modification by collateral capacity (adjusted common odds ratio (acOR), 1.12; 95% CI, 0.72–1.74; adjusted P for interaction = 0.83). Successful reperfusion before thrombectomy and the number of passes in the thrombectomy alone group differed significantly from the alteplase pretreatment group (2.6% vs. 11.5%; corrected P = 0.02 and 2 vs. 1; corrected P = 0.003). There was no interaction between treatment allocation and collateral capacity on all outcomes. ConclusionsEVT alone and EVT preceded by over 2/3-dose intravenous alteplase might have equal efficacy and safety for patients with acute anterior circulation large vessel occlusion, except for successful perfusion before thrombectomy and the number of passes.

Abstract WMP79: Stroke Risk Prediction In Symptomatic Anterior Circulation ICAS: Post Hoc Analysis Of Regional QMRA Flow From The MYRIAD Study

Introduction: Intracranial atherosclerotic disease (ICAD) remains a major source of stroke worldwide, with high recurrence risk. Prior evaluation of posterior circulation ICAD patients enrolled in the prospective VERiTAS and MYRIAD studies revealed regional hypoperfusion, assessed by large vessel flow measurements using quantitative MRA (QMRA), predicts subsequent vertebrobasilar stroke risk. We examined whether a similar approach to regional flow assessment using QMRA predicted stroke risk in anterior circulation ICAD patients enrolled in MYRIAD. Methods: MYRIAD enrolled patients with recent TIA or stroke attributable to 50-99% stenosis of proximal intracranial artery; the primary outcome was ischemic stroke in the territory of the stenotic artery with 1 year of follow-up. Secondary outcomes included new in-territory infarcts on MRI at 6-8 weeks. Flow was measured in the major intracranial arteries at baseline using QMRA. We designated patients as low- or normal-flow status based on an algorithm assessing distal flow and collateral capacity using age-normalized MCA and hemispheric (aggregate of ipsilateral ACA, MCA, and PCA) flows. Different thresholds for flow status categorization were tested to determine the optimal algorithm for stroke risk prediction. Results: Of 73 enrolled subjects with symptomatic anterior circulation ICAD, 7 (9.6%) patients had recurrent stroke. Z-score thresholds for age-normalized flow ranging from -0.5 to -1.5 were examined. The optimal thresholds identified were as follows: -1 for the MCA and -0.75 for hemispheric flow. 24 (33%) patients were categorized as low-flow status based on these thresholds; recurrent stroke occurred in 21% of low-flow patients vs. 4% of normal-flow patients (OR 6.2 (95% CI 1.1-34.7, p=0.04). However, flow status was not predictive of recurrent infarct on imaging among 61 patients with 6-8 week MRI (32% in low-flow vs. 26% in normal-flow patients). Conclusions: Similar to the predictive value in the posterior circulation, distal flow status assessed through QMRA regional flow measurement appears to be predictive for recurrent clinical (but not imaging-based) stroke. Identification of high-risk patients has implications for future investigation of therapeutic interventions.

Assessment of malformations, variations and diameters of vessels forming the circle of Willis - An autopsy study in a non-cerebrovascular cohort.

The collateral capacity of the circle of Willis (CoW) may play an important role in the development of ischemic strokes. The occurrence of classical polygon shows wide geographical variations and morphological data on diameters of the Willisian collaterals are scarce. We aimed to assess CoW variations and vessel diameters in a Central European cohort. CoWs were removed during routine autopsy. The morphological pattern of the circles was recorded. The prepared circles were then put between two glass plates and tightly compressed. The length of the vessels and half of the circumference were measured under a light microscope enabling measurement with an approximation of 0.1 mm. Vessel diameters were calculated from vessel circumference. A total of 110 circles were analysed. Incomplete circles (missing one or two segments of CoW) were found in 25 cases (22.7%). Any forms of anatomical variations were detected in 14 cases (12.7%). When applying the <1 mm diameter threshold for analysis, 36 anterior communicating arteries (32.7%), 53 right posterior communicating arteries (48.2%), 73 left posterior communicating arteries (66.4%) and 18 posterior communicating arteries (16.3%) on both the sides were considered hypoplastic. In patients without stroke in their history, complete CoW may be present in >60% of the cases. Our diameter data may serve as reference values for the Central-European population.

Heterogeneous corporate borrowing behaviours during the COVID-19 pandemic: evidence from Korea

ABSTRACT This study investigates the loan financing behaviours of Korean firms during the COVID-19 pandemic. I find that financially unhealthy firms and firms with insufficient collateral capacity borrowed less during the pandemic, suggesting that lenders consider credit risk in their lending decisions. Meanwhile, the results provide evidence of credit misallocation. Particularly, zombie firms were able to increase their borrowings and firms increased their borrowings irrespective of their profitability and uncertainty. These results suggest that, without careful monitoring, lenders will suffer loan loss problems to the extent that they misallocated bank credit.

Collateral Capacity Assessment

Background and PurposeIntracranial collateral capacity is conducive to imply parenchymal perfusion of affected territory after acute vessel occlusion. The Tan collateral score is commonly used to assess the intracranial collateral capacity; however, this score is coarsely grained and interobserver agreement is low, which reduces prognostic value and clinical utility. We introduce and evaluate an alternative extended Tan score based on the conventional Tan scale and assess the agreement with a quantitative score.MethodsWe included 100 consecutive patients with a proven acute single large vessel occlusion of the proximal anterior circulation. Collaterals were graded with the conventional and extended Tan score and an automated quantitative score. The extended Tan score is a finer 6‑scale manual score based on the conventional 4‑point Tan scale. The quantitative score is calculated by an automatic software package (StrokeViewer). Interobserver agreement of the manual scores was assessed with the weighted kappa. The Spearman correlation coefficient was calculated to determine the agreement between the manual and automated collateral scores.ResultsThe interobserver agreement was higher for the extended score than for the conventional score with a weighted kappa of 0.70 and 0.65, respectively. For the extended and conventional score, the Spearman correlation coefficient for the agreement with the automated score was 0.78 and 0.76, respectively.ConclusionBecause of the good interobserver agreement and good agreement with quantitative assessment, the extended collateral score is a strong candidate to improve prognostic value of collateral assessment and implementation in clinical practice.

A Linarin Derivative Protects against Ischemia-Induced Neuronal Injury in Mice by Promoting Cerebral Blood Flow Recovery via KDELR-Dependent CSPG4 Activation.

The cerebral ischemic microvascular response and collateral circulation compensatory capacity are important for the outcome of ischemic stroke. Here, we sought to evaluate the effect of a linarin derivate 4′-benzylapigenin-7-β-rutinoside (BLR) on neurological function and cerebral blood flow restoration in ischemic stroke. A mouse model of middle cerebral artery occlusion (30 min) with reperfusion (24 h) was used to mimic ischemic stroke in vivo, and 2,3,5-triphenyltetrazolium chloride (TTC) staining, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays, and immunofluorescence microscopy were used to assess the protective effects of BLR on infarct volume, neurological function, neuronal apoptosis, and inflammatory damage. Cerebral blood flow was assayed by laser speckle contrast imaging. Double immunostaining of GFAP-collagen IV and brain lucidification were performed to determine the protective effects of BLR on the disruption of brain vasculature. Differential gene expression was assessed by RNA sequencing. Coimmunoprecipitation and western blotting were used to explore the mechanism of BLR-induced neuroprotection. The results of in vivo experiments showed that BLR administration after reperfusion onset reduced infarct volume, improved neurological function, and decreased the neural cell apoptosis and inflammatory response in the ischemic brain, which was accompanied by increased cerebral blood flow and reduced detachment of astrocyte endfeet from the capillary basement membrane. The RNA sequencing data showed that BLR promoted the upregulation of extracellular matrix and angiogenesis pathway-related genes; in particular, BLR significantly increased the expression of the chondroitin sulfate proteoglycan 4 (CSPG4) gene, enhanced the membrane location of CSPG4, and promoted its downstream signaling protein expression, which is associated with KDEL receptor (KDELR) activation. In addition, activated KDELR further increased the phosphorylation of mitogen-activated protein kinases after BLR treatment. Taken together, our data showed that BLR could protect against ischemic brain injury and may serve as a new promising therapeutic candidate drug for ischemic stroke, and that KDELR might act as both a sensor and effector to activate CSPG4 to increase cerebral blood flow.

Abstract 11515: Noninvasive Quantitation of Coronary Collateral Flow Capacity in Patients with Chronic Total Occlusion Treated with External Counter Pulsation: Dobutamine Compared with Vasodilator Stress Pet Identifies Collaterogenesis

Introduction: FDA approved external counterpulsation (ECP) improves coronary collateral flow index measured invasively, using intracoronary wedge pressure beyond a severe stenosis. However, there is presently no noninvasive method to measure coronary collateral flow capacity (CCFC), in patients with total coronary occlusion (CTO). Hypothesis: CCFC can be measured noninvasively by comparing the improvement in flow in the ischemic bed beyond CTO, using dobutamine stress (DBT), which supports supply side pressure, compared with vasodilator stress (DIP), which lowers supply side pressure, causing coronary steal. Methods: Seven patients with CTO were treated with 35 sessions of ECP, and studied with both DIP and DOB stress PET myocardial perfusion imaging. Coronary flow capacity (CFC), which integrates absolute rest and stress flow with coronary flow reserve on a per pixel basis, was measured objectively with FDA approved HeartSee software. Results: As shown in the Table, all patients demonstrated a decrease in the size of the ischemic zone at risk, defined as moderate or severely reduced CFC, when CFC with DIP was compared with DOB: 28% LV mass vs. 5%; p &amp;lt 0.01. Five of 7 patients also demonstrated significant improvement in global CFC by Kolmogorov-Smirnoff analysis. Absolute stress flow into the ischemic zone improved significantly in all ECP treated patients during demand ischemia compared with vasodilator stress (1.9 vs. 1 ml/min/g; p &amp;lt 0.01). One of the two patients who did not improve global CFC, despite ECP treatment, underwent coronary arteriography demonstrating a new flow limiting stenosis in the supply side vessel, which was successfully stented. Conclusion: ECP treatment is associated with improved coronary collateralization in patients with CTO, which can be identified noninvasively with quantitative PET myocardial perfusion imaging.

Is Agricultural Credit Programme Effective in Boro Cultivation? Evidence from State-owned Bank of Mymensingh District

High input-intensive Boro rice cultivation needs substantial agricultural credit for the resource-poor Bangladeshi farmers. An investigation was conducted at Fulbaria upazila of Mymensingh district to assess loan attainment cost from Bangladesh Krishi Bank (BKB) and its utilization pattern; evaluate the effects of credit on Boro cultivation, and identify the major drivers of the agricultural credit programme. For the study, 140 farmers were divided into two groups: those who took a loan from BKB and those who did not. Results revealed that the borrowers had to pay Tk 10.23 for getting a hundred taka loan from BKB most of which was an unofficial cost. More than half of the obtained loan was used for Boro cultivation whereas 21% was used for family consumption and the rest (25%) was used for other purposes such as reimbursement of the previous loan from formal and informal sources, wedding and other income-generating activities including petty business. BKB credit borrowers obtained more benefits through Boro cultivation than non-borrowers. The major strengths of the BKB’s agricultural credit programme were well-established infrastructure, experienced manpower, country-wide network, and lower interest rate. Whereas complex and lengthy institutional procedures, the inevitability of collateral and poor institutional capacity were being revealed as the weaknesses of the programme. Prevalence of brokers or corrupt officials and political influence were identified as the major constraints for the loan acquirement. More advanced research is recommended, with an emphasis on agricultural credit programmes, to ensure their effectiveness.&#x0D; Bangladesh Rice J. 24 (1): 85-95, 2020

Hedging, Liquidity, and Productivity

to study the effects of liquidity and productivity on corporate hedging, we extend dynamic risk management models by incorporating procyclical collateral capacity and units-of-production depreciation and test the key predictions by using a comprehensive data set of oil and gas producers. After carefully isolating unpredictable shocks to firm liquidity and productivity, we find hedging intensity is positively correlated with liquidity and productivity. Furthermore, firms with more procyclical collateral capacity exhibit a more positive hedging-productivity correlation and firms with more flexible production technologies exhibit a more negative correlation between hedging and operating cash flows. These results challenge existing models but are consistent with our theory.

Variations in the Circle of Willis in a large population sample using 3D TOF angiography: The Tromsø Study.

The main arteries that supply blood to the brain originate from the Circle of Willis (CoW). The CoW exhibits considerable anatomical variations which may have clinical importance, but the variability is insufficiently characterised in the general population. We assessed the anatomical variability of CoW variants in a community-dwelling sample (N = 1,864, 874 men, mean age = 65.4, range 40–87 years), and independent and conditional frequencies of the CoW’s artery segments. CoW segments were classified as present or missing/hypoplastic (w/1mm diameter threshold) on 3T time-of-flight magnetic resonance angiography images. We also examined whether age and sex were associated with CoW variants. We identified 47 unique CoW variants, of which five variants constituted 68.5% of the sample. The complete variant was found in 11.9% of the subjects, and the most common variant (27.8%) was missing both posterior communicating arteries. Conditional frequencies showed patterns of interdependence across most missing segments in the CoW. CoW variants were associated with mean-split age (P = .0147), and there was a trend showing more missing segments with increasing age. We found no association with sex (P = .0526). Our population study demonstrated age as associated with CoW variants, suggesting reduced collateral capacity with older age.

Natural History of Hemodynamics in Vertebrobasilar Disease: Temporal Changes in the VERiTAS Study Cohort.

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. 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. 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]). 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.

Optimized Hemodynamic Assessment to Predict Stroke Risk in Vertebrobasilar Disease: Analysis From the VERiTAS Study.

BackgroundAtherosclerotic vertebrobasilar disease is a significant etiology of posterior circulation stroke. The prospective observational VERiTAS (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke) study demonstrated that distal hemodynamic status is a robust predictor of subsequent vertebrobasilar stroke risk. We sought to compare predictive models using thresholds for posterior circulation vessel flows standardized to age and vascular anatomy to optimize risk prediction.Methods and Results VERiTAS enrolled patients with recent vertebrobasilar transient ischemic attack or stroke and ≥50% atherosclerotic stenosis/occlusion in vertebral and/or basilar arteries. Quantitative magnetic resonance angiography measured large‐vessel vertebrobasilar territory flow, and patients were designated as low or normal flow based on a prespecified empiric algorithm considering distal territory regional flow and collateral capacity. For the present study, post hoc analysis was performed to generate additional predictive models using age‐specific normalized flow measurements. Sensitivity, specificity, and time‐to‐event analyses were compared between the algorithms. The original prespecified algorithm had 50% sensitivity and 79% specificity for future stroke risk prediction; using a predictive model based on age‐normalized flows in the basilar and posterior cerebral arteries, standardized to vascular anatomy, optimized flow status thresholds were identified. The optimized algorithm maintained sensitivity and increased specificity to 84%, while demonstrating a larger and more significant hazard ratio for stroke on time‐to‐event analysis.ConclusionsThese results indicate that flow remains a strong predictor of stroke across different predictive models, and suggest that prediction of future stroke risk can be optimized by use of vascular anatomy and age‐specific normalized flows.

Transcranial doppler methods in the assessment of cerebral vasomotor reactivity

Introduction. Transcranial Doppler is the only non-invasive neuroimaging modality in the diagnosis and monitoring of various neurovascular diseases. Apart from assessing cerebral hemodynamics of blood flow in the basal brain arteries, transcranial Doppler provides physiological data and anatomical images. Quantification analysis of vasomotor reactivity. Various transcranial Doppler methods evaluate cerebral vasomotor reactivity, providing important information on the properties of arterioles under induced hemodynamic conditions. Exogenous and endogenous vasoactive stimuli of different potency (apnea, acetazolamide, carbon dioxide, L-arginine) are most commonly used, making transcranial Doppler a prognostic indicator of future ischemic events. This article reviews principles of various transcranial Doppler methods in the evaluation of vasomotor reactivity, emphasizing their advantages and disadvantages. Transcranial Doppler in the field of reduced vasomotor reactivity. Evaluation of vasomotor reactivity has a role in the prediction of future ischemic events, evaluation of revascularization effect after carotid endarterectomy, but also in the increasingly significant choice of the right time to perform it. In recent years, transcranial Doppler methods have found application in other areas of dysfunctional cerebral hemodynamics: dementia, hypertension, migraines, and sepsis. Conclusion. Due to an excellent temporal resolution, non-invasive approach, good cost-benefit ratio, bedside monitoring, relative simplicity in terms of interpretation and performance, and portability, transcranial Doppler in vasomotor reactivity may be the ideal tool in the evaluation of cerebral hemodynamics, arterial perfusion integrity and collateral capacity.

Clip-wrapping of ruptured blood blister-like aneurysms of the internal carotid artery.

To evaluate the safety and validity of microsurgical Gore-Tex clip-wrapping for ruptured blood blister-like aneurysms (BBAs) of the internal carotid artery (ICA). Single-surgeon series. Retrospective study. Data analyzed were patient age, sex, Hunt and Hess grade (H&H), Fisher grade, time from rupture to hospitalization, aneurysm size and location, collateral capacity of the circle of Willis, time from hospitalization to aneurysm repair, aneurysm obliteration, complications, and modified Rankin scale (mRS) at follow-up. Six patients (2 males, 4 females) with ICA BBAs underwent clip-wrapping between 2011 and 2016. Median age was 50.0years (range 31.7-54.0). H&H was grade 1 or 2 in 5 patients and grade 4 in 1 patient. All aneurysms were small (≤ 0.3cm), without relation to vessel bifurcations, and located anteromedially, anterolaterally, and superomedially on the ICA trunk. Right side was most frequent (66%). All aneurysms could be clip-wrapped without intraoperative ruptures and all parent arteries could be preserved in the acute phase. Clip-wrapping completely eliminated the BBAs in five patients, whereas one patient underwent additional stent-assisted coiling. There were no re-ruptures, delayed infarctions, or deaths postoperatively. After a median follow-up of 57months (range 20-90), outcome was favorable (mRS score 0-2) in all patients without radiographic signs of recurrences. Using the Gore-Tex clip-wrapping technique for ruptured ICA BBAs, the aneurysm could be treated without intraoperative ruptures or parent artery sacrifice in the acute phase. The outcomes were similar to other SAH patients and on follow-up, there were no aneurysm recurrences, indicating a durable long-term outcome.