Translesional Pressure Gradient Alters Relationship Between Blood Pressure and Recurrent Stroke in Intracranial Stenosis

Clinical implications of haemodynamics in symptomatic intracranial atherosclerotic stenosis by computational fluid dynamics modelling: a systematic review

BACKGROUND

Recently, computational fluid dynamics (CFD) has been used to simulate blood flow of symptomatic intracranial atherosclerotic stenosis (sICAS) and investigate the clinical implications of its haemodynamic features, which were systematically reviewed in this study.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Meta-analysis of Observational Studies in Epidemiology statements, we searched PubMed and Embase up to March 2024 and screened for articles reporting clinical implications of haemodynamic parameters in sICAS derived from CFD models.

RESULTS

19 articles met the inclusion criteria, all studies recruiting patients from China. Most studies used CT angiography (CTA) as the source image for vessel segmentation, and generic boundary conditions, rigid vessel wall and Newtonian fluid assumptions for CFD modelling, in patients with 50%-99% sICAS. Pressure and wall shear stress (WSS) were quantified in almost all studies, and the translesional changes in pressure and WSS were usually quantified with a poststenotic to prestenotic pressure ratio (PR) and stenotic-throat to prestenotic WSS ratio (WSSR). Lower PR was associated with more severe stenosis, better leptomeningeal collaterals, prolonged perfusion time and internal borderzone infarcts. Higher WSSR and other WSS measures were associated with positive vessel wall remodelling, regression of luminal stenosis and artery-to-artery embolism. Lower PR and higher WSSR were both associated with the presence and severity of cerebral small vessel disease. Moreover, translesional PR and WSSR were promising predictors for stroke recurrence in medically treated patients with sICAS and outcomes after acute reperfusion therapy, which also provided indicators to assess the effects of stenting treatment on focal haemodynamics.

CONCLUSIONS

CFD is a promising tool in investigating the pathophysiology of ICAS and in risk stratification of patients with sICAS. Future studies are warranted for standardisation of the modelling methods and validation of the simulation results in sICAS, for its wider applications in clinical research and practice.

Hemodynamic effects of bifurcation and stenosis geometry on carotid arteries with different degrees of stenosis

Objective.Carotid artery stenosis (CAS) is a key factor in pathological conditions, such as thrombosis, which is closely linked to hemodynamic parameters. Existing research often focuses on analyzing the influence of geometric characteristics at the stenosis site, making it difficult to predict the effects of overall vascular geometry on hemodynamic parameters. The objective of this study is to comprehensively examine the influence of geometric morphology at different degrees of CAS and at bifurcation sites on hemodynamic parameters.Approach.A three-dimensional model is established using computed tomography angiography images, and eight geometric parameters of each patient are measured by MIMICS. Then, computational fluid dynamics is utilized to investigate 60 patients with varying degrees of stenosis (10%-95%). Time and grid tests are conducted to optimize settings, and results are validated through comparison with reference calculations. Subsequently, correlation analysis using SPSS is performed to examine the relationship between the eight geometric parameters and four hemodynamic parameters. In MATLAB, prediction models for the four hemodynamic parameters are developed using back propagation neural networks (BPNN) and multiple linear regression.Main results.The BPNN model significantly outperforms the multiple linear regression model, reducing mean absolute error, mean squared error, and root mean squared error by 91.7%, 93.9%, and 75.5%, respectively, and increasingR2from 19.0% to 88.0%. This greatly improves fitting accuracy and reduces errors. This study elucidates the correlation and patterns of geometric parameters of vascular stenosis and bifurcation in evaluating hemodynamic parameters of CAS.Significance.This study opens up new avenues for improving the diagnosis, treatment, and clinical management strategies of CAS.

Hemodynamic assessment of intracranial atherosclerotic stenosis: comparison between invasive non-hyperemic pressure ratio and angiography-derived quantitative flow ratio

Objectives

To evaluate the diagnostic accuracy of the quantitative flow ratio (QFR) for hemodynamic exploration of intracranial atherosclerotic stenosis, using the invasive cerebrovascular pressure ratio (CVPR) and resting full-cycle ratio (RFR) as reference standards.

Materials and methods

Patients with symptomatic unifocal intracranial atherosclerotic stenosis were included. The CVPR was defined as the ratio of the proximal and distal pressures. All patients underwent angioplasty under general anesthesia. The QFR was calculated based on digital subtraction angiography. Using the CVPR as a reference, we compared its correlation with the QFR across different degrees and locations of stenosis.

Results

The CVPR and QFR were measured in 34 vessels of 32 patients. The QFR demonstrated a high correlation and excellent agreement(r = 0.8227, p < 0.001) with the CVPR in distal stenosis before intervention. In the subgroup with diameter stenosis >80%, the QFR showed a high correlation (r = 0.8812, p < 0.001) with the CVPR. In the anterior circulation subgroup, the QFR showed an excellent correlation (r = 0.9066, p < 0.001) with the CVPR. In the posterior circulation subgroup, the QFR showed a high correlation with the CVPR (r = 0.7706, p < 0.001). Diameter stenosis rates showed a moderate negative correlation with the CVPR.

Conclusion

There was a strong correlation between the QFR and wire-based CVPR, especially for anterior circulation lesions before intervention. The QFR may serve as a predictive factor for evaluating hemodynamic changes in intracranial atherosclerotic stenosis.

Intravascular enhancement sign at 3D T1-weighted turbo spin echo sequence is associated with cerebral atherosclerotic stenosis

OBJECTIVE

Intravascular enhancement sign (IVES) at three-dimensional T1-weighted turbo spin echo (3D T1W TSE) sequence may be a simple hemodynamic maker. This study aims to investigate the association between IVES and features of intracranial atherosclerotic stenosis (ICAS).

METHOD

Retrospective analysis of clinical and imaging data of patients who underwent high resolution-vessel wall imaging (HR-VWI) examination from May 2021 to May 2023. The number of IVES vessels and ICAS features at HR-VWI were extracted by two neuroradiologists. Paired comparisons and correlation analysis on these indicators were performed.

RESULTS

A total of 118 patients with ICAS in the first segment of the middle cerebral artery and accompanied by unilateral IVES were enrolled. Compared to the non-IVES side, a higher incidence of ischemic events and intraplaque hemorrhage (IPH), higher degree of vascular stenosis and enhancement, lower remodeling index, and lower signal intensity ratio (SIR) were found in subjects with IVES. In the ICAS with IVES, 79.66 % showed severe stenosis and occlusion; in the ICAS with severe stenosis and occlusion, 89.5 % showed IVES in the distal. A multivariable logistic regression model identified the vascular stenosis degree (OR = 1.922; 95 %CI [1.37-2.692]; P < 0.001), enhanced-degree (OR = 2.486; 95 %CI [1.315-4.698]; P = 0.005), position (OR = 2.869; 95 %CI [1.255-6.560]; P = 0.012), and SIR (OR = 0.032; 95 %CI [0.004-0.275]; P = 0.002) were independent association with the presence of IVES. The area under the curve was 0.911 for the use of IVES vessel quantities to identify severe stenosis and occlusion of arterial lumen.

CONCLUSION

The number of IVES vessels was associated with the local features of ICAS, which may indicate severe stenosis and occlusion in the major branches of the proximal artery.

Characteristics of Atherosclerotic Plaques and Stroke Mechanism in Patients with Border-Zone Infarcts: A High-resolution Magnetic Resonance Imaging Study

BACKGROUND

Relatively little is known about the plaque characteristics of border-zone infarcts and how they differ between cortical border-zone (CBZ) and internal border-zone (IBZ) infarcts.

METHODS

We conducted a retrospective observational cohort study of patients with intracranial atherosclerotic disease who underwent high-resolution magnetic resonance imaging (HR-MRI) examination. Individuals with border-zone infarcts in the middle cerebral artery (MCA) territory, detected by diffusion-weighted imaging, were enrolled. Plaque morphological and compositional parameters of both IBZ and CBZ groups were compared. Independent predictors were identified using a binary logistic regression model, and the sensitivity and specificity of the model were assessed using a receiver operating characteristic curve. Kaplan-Meier survival analysis further explored differences in stroke recurrence between BZ patients with mono or dual antiplatelet therapy.

RESULTS

We reviewed 101 symptomatic patients with border-zone infarcts (BZ) within the MCA territory in the study. Out of the patients meeting the imaging eligibility criteria, we detected 34 cases with isolated IBZ, 23 cases with isolated CBZ, and six cases with both IBZ and CBZ infarcts. Those with IBZ infarcts had a higher plaque burden than those without (p < 0.001), and those with CBZ infarcts exhibited a complicated plaque less frequently than those without (37.9% vs 67.6%, p = 0.018). In those with isolated IBZ or CBZ infarcts, plaque burden was independently associated with isolated IBZ infarcts (odd ratio=1.08; 95% CI, 1.02-1.15; p = 0.023). During the median follow-up period of 37 (27, 50) months, 13.8% of patients receiving early dual antiplatelet treatment and 30.4% of those on single antiplatelet therapy experienced stroke recurrence (p = 0.182).

CONCLUSION

Intracranial atherosclerotic plaque morphology and composition differ between patients with IBZ and those with CBZ infarcts. Higher plaque burden is more associated with IBZ infarcts.

Hemodynamic Stroke: Emerging Concepts, Risk Estimation, and Treatment

Ischemic stroke can arise from the sudden occlusion of a brain-feeding artery by a clot (embolic), or local thrombosis. Hemodynamic stroke occurs when blood flow does not sufficiently meet the metabolic demand of a brain region at a certain time. This discrepancy between demand and supply can occur with cerebropetal arterial occlusion or high-grade stenosis but also arises with systemic conditions reducing blood pressure. Treatment of hemodynamic stroke is targeted toward increasing blood flow to the affected area by either systemically or locally enhancing perfusion. Thus, blood pressure is often maintained above normal values, and extra-intracranial flow augmentation bypass surgery is increasingly considered. Still, current evidence supporting the superiority of pressure or flow increase over conservative measures is limited. However, methods assessing hemodynamic impairment and identifying patients at risk of hemodynamic stroke are rapidly evolving. Sophisticated models incorporating clinical and imaging factors have been suggested to aid patient selection. In this narrative review, we provide current state-of-the-art knowledge about hemodynamic stroke, tools for assessment, and treatment options.

Cerebral Hemodynamics Underlying Artery-to-Artery Embolism in Symptomatic Intracranial Atherosclerotic Disease

Artery-to-artery embolism (AAE) is a common stroke mechanism in intracranial atherosclerotic disease (ICAD), associated with a considerable risk of recurrent stroke. We aimed to investigate cerebral hemodynamic features associated with AAE in symptomatic ICAD. Patients with anterior-circulation, symptomatic ICAD confirmed in CT angiography (CTA) were recruited. We classified probable stroke mechanisms as isolated parent artery atherosclerosis occluding penetrating artery, AAE, hypoperfusion, and mixed mechanisms, largely based on infarct topography. CTA-based computational fluid dynamics (CFD) models were built to simulate blood flow across culprit ICAD lesions. Translesional pressure ratio (PR = Pressurepost-stenotic/Pressurepre-stenotic) and wall shear stress ratio (WSSR = WSSstenotic-throat/WSSpre-stenotic) were calculated, to reflect the relative, translesional changes of the two hemodynamic metrics. Low PR (PR ≤ median) and high WSSR (WSSR ≥ 4th quartile) respectively indicated large translesional pressure and elevated WSS upon the lesion. Among 99 symptomatic ICAD patients, 44 had AAE as a probable stroke mechanism, 13 with AAE alone and 31 with coexisting hypoperfusion. High WSSR was independently associated with AAE (adjusted OR = 3.90; P = 0.022) in multivariate logistic regression. There was significant WSSR-PR interaction on the presence of AAE (P for interaction = 0.013): high WSSR was more likely to associate with AAE in those with low PR (P = 0.075), but not in those with normal PR (P = 0.959). Excessively elevated WSS in ICAD might increase the risk of AAE. Such association was more prominent in those with large translesional pressure gradient. Hypoperfusion, commonly coexisting with AAE, might be a therapeutic indicator for secondary stroke prevention in symptomatic ICAD with AAE.

Correlations between intravascular pressure gradients and cerebral blood flow in patients with symptomatic, medically refractory, anterior circulation artery stenosis: an exploratory study

BACKGROUND

Fractional flow reserve is widely used in coronary disease management, with a threshold of 0.80. However, similar thresholds are unclear in functional assessment of intracranial atherosclerotic stenosis (ICAS).

OBJECTIVE

To investigate the potential threshold values in functional assessment of ICAS by studying the relation between pressure-derived indexes and perfusion parameters derived from arterial spin labeling (ASL).

METHODS

Patients were consecutively screened between June 2019 and December 2020. The translesional gradient indices were measured by pressure guidewire under resting-state conditions and recorded as mean distal/proximal pressure ratios (Pd/Pa) and translesional pressure difference (Pa-Pd). Preoperative and postoperative cerebral blood flow (CBF) bilaterally and the relative cerebral blood flow ratio (rCBF) were measured and recorded by ASL imaging. Patients were defined as having reversible hemodynamic insufficiency only if the preoperative rCBF was <0.9 and the postoperative rCBF≥0.9. Preoperative and postoperative Pd/Pa or Pa-Pd values of those patients were used to calculate the threshold.

RESULTS

Twenty-five patients (19 men, 6 women) with a mean age of 56.7±9.4 years were analyzed. Seventeen patients (68%) had lesions at the M1 segment of the middle cerebral artery, eight patients (32%) had lesions in the intracranial internal carotid artery. In 14 of the 25 patients, the preoperative rCBF was <0.9 and the postoperative rCBF≥0.9. Cut-off values of Pd/Pa=0.81 and Pa-Pd=8 mm Hg were suggested to be associated with hemodynamic insufficiency.

CONCLUSIONS

In a highly selected subgroup with ICAS, cut-off values of translesional pressure gradients (Pd/Pa=0.81 or Pa-Pd=8 mm Hg) were preliminarily established, which may facilitate clinical decision-making in the management of ICAS.

Cerebral hemodynamics and stroke risks in symptomatic intracranial atherosclerotic stenosis with internal versus cortical borderzone infarcts: A computational fluid dynamics study

There may be different mechanisms underlying internal (IBZ) and cortical (CBZ) borderzone infarcts in intracranial atherosclerotic stenosis. In 84 patients with symptomatic, 50-99% atherosclerotic stenosis of M1 middle cerebral artery (MCA-M1) with acute borderzone infarcts in diffusion-weighted imaging, we classified the infarct patterns as isolated IBZ (n = 37), isolated CBZ (n = 31), and IBZ+CBZ (n = 16) infarcts. CT angiography-based computational fluid dynamics models were constructed to quantify translesional, post-stenotic to pre-stenotic pressure ratio (PR) in the MCA-M1 lesion. Those with IBZ infarcts were more likely to have a low PR (indicating impaired antegrade flow across the lesion) than those without (p = 0.012), and those with CBZ infarcts were more likely to have coexisting small cortical infarcts (indicating possible embolism) than those without (p = 0.004). In those with isolated IBZ or CBZ infarcts, low PR was independently associated with isolated IBZ infarcts (adjusted odds ratio = 4.223; p = 0.026). These two groups may also have different trajectories in the stroke risks under current medical treatment regimen, with a higher risk of same-territory ischemic stroke recurrence within 3 months in patients with isolated IBZ infarcts than isolated CBZ infarcts (17.9% versus 0.0%; log-rank p = 0.023), but similar risks later in 1 year.

CT-derived fractional flow reserve in intracranial arterial stenosis: A pilot study based on computational fluid dynamics

BACKGROUND

CT-derived fractional flow reserve (CT-FFR) has been widely applied in coronary hemodynamic assessment. However, the feasieablity and standardization measurement in intracranial artery stenosis (ICAS) remains to be defined.

PURPOSE

To demonstrate the feasibility of CT-FFR in ICAS functional assessment and explore the optimal CT-FFR measurement position with invasive FFR as reference standard.

MATERIALS AND METHODS

Nineteen patients (mean age, 58.6 years ± 1.9 [SD]; 13 men) with moderate to severe (≥50 %) ICAS undergoing guidewire-based pressure measurement and preoperative head CT angiography (CTA) were retrospectively enrolled. CT-FFR was measured in the following standard measurement positions, including the end of stenosis (D0), 1 cm distal to the stenosis (D1) and 2 cm distal to the stenosis (D2). Diagnostic performance of CT-FFR was assessed by the area under the curve (AUC) of receiver operating characteristic curves by assuming invasive FFR ≤ 0.80 or 0.75 as hemodynamically significant stenosis.

RESULTS

Excellent intra- and inter-observer agreement (ICC range, 0.930-0.992) was observed for CT-FFR measurement in different positions. Under different FFR thresholds, the diagnostic performance of CT-FFRD1 showed perfect prediction with AUC values of 1.000 (95 % CI: 0.824, 1.000). The sensitivity, specificity and AUC of CT-FFRD1 ≤ 0.80 in detecting FFR ≤ 0.80 was 0.94 (95 % CI: 0.68, 1.00), 1.00 (95 % CI: 0.31, 1.00) and 0.969 (95 % CI: 0.772, 1.000), respectively. Similar performance of CT-FFRD1 ≤ 0.75 was obtained for identifying FFR ≤ 0.75 with the AUC of 0.964. The strongest correlation (r = 0.915, p < 0.001) and agreement (mean difference: 0.02, 95 % limits of agreement: -0.16 to 0.19) were observed between CT-FFRD1 and FFR.

CONCLUSION

Cerebral CT-derived fractional flow reserve (CT-FFR) measured 1 cm distal to stenosis achieved the most comparable results with invasive FFR, which indicated its potentially promising clinical application for evaluating the functional relevance of intracranial artery stenosis.

Cerebral haemodynamics in symptomatic intracranial atherosclerotic disease: a narrative review of the assessment methods and clinical implications

Intracranial atherosclerotic disease (ICAD) is a common cause of ischaemic stroke and transient ischaemic attack (TIA) with a high recurrence rate. It is often referred to as intracranial atherosclerotic stenosis (ICAS), when the plaque has caused significant narrowing of the vessel lumen. The lesion is usually considered 'symptomatic ICAD/ICAS' (sICAD/sICAS) when it has caused an ischaemic stroke or TIA. The severity of luminal stenosis has long been established as a prognostic factor for stroke relapse in sICAS. Yet, accumulating studies have also reported the important roles of plaque vulnerability, cerebral haemodynamics, collateral circulation, cerebral autoregulation and other factors in altering the stroke risks across patients with sICAS. In this review article, we focus on cerebral haemodynamics in sICAS. We reviewed imaging modalities/methods in assessing cerebral haemodynamics, the haemodynamic metrics provided by these methods and application of these methods in research and clinical practice. More importantly, we reviewed the significance of these haemodynamic features in governing the risk of stroke recurrence in sICAS. We also discussed other clinical implications of these haemodynamic features in sICAS, such as the associations with collateral recruitment and evolution of the lesion under medical treatment, and indications for more individualised blood pressure management for secondary stroke prevention. We then put forward some knowledge gaps and future directions on these topics.

Characteristics and evaluation of atherosclerotic plaques: an overview of state-of-the-art techniques

Atherosclerosis is an important cause of cerebrovascular and cardiovascular disease (CVD). Lipid infiltration, inflammation, and altered vascular stress are the critical mechanisms that cause atherosclerotic plaque formation. The hallmarks of the progression of atherosclerosis include plaque ulceration, rupture, neovascularization, and intraplaque hemorrhage, all of which are closely associated with the occurrence of CVD. Assessing the severity of atherosclerosis and plaque vulnerability is crucial for the prevention and treatment of CVD. Integrating imaging techniques for evaluating the characteristics of atherosclerotic plaques with computer simulations yields insights into plaque inflammation levels, spatial morphology, and intravascular stress distribution, resulting in a more realistic and accurate estimation of plaque state. Here, we review the characteristics and advancing techniques used to analyze intracranial and extracranial atherosclerotic plaques to provide a comprehensive understanding of atheroma.

The relationship between geometry and hemodynamics of the stenotic carotid artery based on computational fluid dynamics

OBJECTIVE

The purpose of this work was to investigate the relationship between the geometric factors and the hemodynamics of the stenotic carotid artery.

METHODS

We retrospectively reviewed data of patients with carotid stenosis (40%-95%). The Navier-Stokes equations were solved using ANSYS CFX 18.0. Correlation analysis was based on Spearman's test. Geometric variables (p < 0.1 in the univariate analysis) were entered into the logistical regression. A receiver-operating characteristics analysis was used to detect hemodynamically significant lesions.

RESULTS

81 patients (96 arteries) were evaluated. The logistic regression analysis revealed that the translesional pressure ratio was significantly correlated with the stenosis degree (OR = 1.147, p < 0.001) and the angle between internal carotid artery and external carotid artery (angle γ) (OR = 0.933, p = 0.01). The translesional wall shear stress ratio was significantly correlated with stenosis degree (OR = 1.094, p < 0.001), lesion length (OR = 0.873, p = 0.01), lumen area of internal carotid artery (OR = 0.867, p = 0.002), and lumen area of common carotid artery (OR = 1.058, p = 0.01). For predicting low translesional pressure ratio, the AUC was 0.71 (p < 0.001) for angle γ, and was 0.87 (p < 0.001) for stenosis degree. For predicting high translesional wall shear stress ratio, the AUC was 0.62 (p = 0.04) for lumen area of internal carotid artery, and was 0.77 (p < 0.001) for stenosis degree.

CONCLUSIONS

Apart from stenosis degree, other geometric characteristics of lesions may also have an influence on hemodynamics of the stenotic carotid artery.

Large Vessel Occlusion Stroke due to Intracranial Atherosclerotic Disease: Identification, Medical and Interventional Treatment, and Outcomes

Large vessel occlusion stroke due to underlying intracranial atherosclerotic disease (ICAD-LVO) is prevalent in 10 to 30% of LVOs depending on patient factors such as vascular risk factors, race and ethnicity, and age. Patients with ICAD-LVO derive similar functional outcome benefit from endovascular thrombectomy as other mechanisms of LVO, but up to half of ICAD-LVO patients reocclude after revascularization. Therefore, early identification and treatment planning for ICAD-LVO are important given the unique considerations before, during, and after endovascular thrombectomy. In this review of ICAD-LVO, we propose a multistep approach to ICAD-LVO identification, pretreatment and endovascular thrombectomy considerations, adjunctive medications, and medical management. There have been no large-scale randomized controlled trials dedicated to studying ICAD-LVO, therefore this review focuses on observational studies.

Risk stratification in symptomatic intracranial atherosclerotic disease with conventional vascular risk factors and cerebral haemodynamics

BACKGROUND AND PURPOSE

Symptomatic intracranial atherosclerotic stenosis (sICAS) is associated with a considerable risk of recurrent stroke despite contemporarily optimal medical treatment. Severity of luminal stenosis in sICAS and its haemodynamic significance quantified with computational fluid dynamics (CFD) models were associated with the risk of stroke recurrence. We aimed to develop and compare stroke risk prediction nomograms in sICAS, based on vascular risk factors and these metrics.

METHODS

Patients with 50%-99% sICAS confirmed in CT angiography (CTA) were enrolled. Conventional vascular risk factors were collected. Severity of luminal stenosis in sICAS was dichotomised as moderate (50%-69%) and severe (70%-99%). Translesional pressure ratio (PR) and wall shear stress ratio (WSSR) were quantified via CTA-based CFD modelling; the haemodynamic status of sICAS was classified as normal (normal PR&WSSR), intermediate (otherwise) and abnormal (abnormal PR&WSSR). All patients received guideline-recommended medical treatment. We developed and compared performance of nomograms composed of these variables and independent predictors identified in multivariate logistic regression, in predicting the primary outcome, recurrent ischaemic stroke in the same territory (SIT) within 1 year.

RESULTS

Among 245 sICAS patients, 20 (8.2%) had SIT. The D₂H₂A nomogram, incorporating diabetes, dyslipidaemia, haemodynamic status of sICAS, hypertension and age ≥50 years, showed good calibration (P for Hosmer-Lemeshow test=0.560) and discrimination (C-statistic 0.73, 95% CI 0.60 to 0.85). It also had better performance in risk reclassification and provided larger net benefits in decision curve analysis, compared with nomograms composed of conventional vascular risk factors only, and plus the severity of luminal stenosis in sICAS. Sensitivity analysis in patients with anterior-circulation sICAS showed similar results.

CONCLUSIONS

The D₂H₂A nomogram, incorporating conventional vascular risk factors and the haemodynamic significance of sICAS as assessed in CFD models, could be a useful tool to stratify sICAS patients for the risk of recurrent stroke under contemporarily optimal medical treatment.

Systolic blood pressure and recurrent stroke in patients with different lesion patterns on diffusion weighted imaging

Little is known about the relationship between baseline systolic blood pressure (SBP) and subsequent clinical events in patients with different lesion patterns on diffusion weighted imaging (DWI). We analyzed the Acute Non‐disabling Cerebrovascular Events (CHANCE) trial dataset. Patients were categorized into negative DW imaging (no detectable lesions), lacunar infarction (single lesion ≤15 mm) and non‐lacunar infarction (single lesion >15 mm or multiple lesions) based on lesion patterns on DWI. The primary outcome was recurrent stroke within 90 days. Cox proportional hazards models were used to assess the association between SBP levels and stroke outcomes in patients with different lesion patterns. A total of 1089 patients were analyzed. We found 258 cases (23.7%) with negative DW imaging, 392 (36.0%) with lacunar infarction and 439 (40.3%) with non‐lacunar infarction. Patients with non‐lacunar infarction had the highest incidence of stroke at 90‐day (P < .001). In non‐lacunar infarction group, compared with SBP < 160 mmHg, patients with SBP ≥ 160 mmHg had significantly higher risk of 90‐day recurrent stroke (20.3% vs. 10.7%; adjusted hazard ratio 1.81, 95% confidence interval 1.09–3.00). No significant association was found between SBP and clinical outcomes in patients with negative DWI and lacunar stroke groups. The result at 1 year was similar as at 90‐day. Therefore, non‐lacunar infarction, the most common lesion pattern in CHANCE study, had the highest risk of recurrent stroke and combined vascular events both in 90 days and 1 year. High baseline SBP was significantly associated with increased risk of short‐ and long‐term recurrent strokes in patients with non‐lacunar infarction.

Stroke Prevention in Symptomatic Large Artery Intracranial Atherosclerosis Practice Advisory: Report of the AAN Guideline Subcommittee

BACKGROUND AND OBJECTIVES

To review treatments for reducing the risk of recurrent stroke or death in patients with symptomatic intracranial atherosclerotic arterial stenosis (sICAS).

METHODS

The development of this practice advisory followed the process outlined in the American Academy of Neurology Clinical Practice Guideline Process Manual, 2011 Edition, as amended. The systematic review included studies through November 2020. Recommendations were based on evidence, related evidence, principles of care, and inferences.

MAJOR RECOMMENDATIONS

Clinicians should recommend aspirin 325 mg/d for long-term prevention of stroke and death and should recommend adding clopidogrel 75 mg/d to aspirin for up to 90 days to further reduce stroke risk in patients with severe (70%-99%) sICAS who have low risk of hemorrhagic transformation. Clinicians should recommend high-intensity statin therapy to achieve a goal low-density lipoprotein cholesterol level <70 mg/dL, a long-term blood pressure target of <140/90 mm Hg, at least moderate physical activity, and treatment of other modifiable vascular risk factors for patients with sICAS. Clinicians should not recommend percutaneous transluminal angioplasty and stenting for stroke prevention in patients with moderate (50%-69%) sICAS or as the initial treatment for stroke prevention in patients with severe sICAS. Clinicians should not routinely recommend angioplasty alone or indirect bypass for stroke prevention in patients with sICAS outside clinical trials. Clinicians should not recommend direct bypass for stroke prevention in patients with sICAS. Clinicians should counsel patients about the risks of percutaneous transluminal angioplasty and stenting and alternative treatments if one of these procedures is being contemplated.

Comparison of Newtonian and Non-newtonian Fluid Models in Blood Flow Simulation in Patients With Intracranial Arterial Stenosis

Background

Newtonian fluid model has been commonly applied in simulating cerebral blood flow in intracranial atherosclerotic stenosis (ICAS) cases using computational fluid dynamics (CFD) modeling, while blood is a shear-thinning non-Newtonian fluid. We aimed to investigate the differences of cerebral hemodynamic metrics quantified in CFD models built with Newtonian and non-Newtonian fluid assumptions, in patients with ICAS.

Methods

We built a virtual artery model with an eccentric 75% stenosis and performed static CFD simulation. We also constructed CFD models in three patients with ICAS of different severities in the luminal stenosis. We performed static simulations on these models with Newtonian and two non-Newtonian (Casson and Carreau-Yasuda) fluid models. We also performed transient simulations on another patient-specific model. We measured translesional pressure ratio (PR) and wall shear stress (WSS) values in all CFD models, to reflect the changes in pressure and WSS across a stenotic lesion. In all the simulations, we compared the PR and WSS values in CFD models derived with Newtonian, Casson, and Carreau-Yasuda fluid assumptions.

Results

In all the static and transient simulations, the Newtonian/non-Newtonian difference on PR value was negligible. As to WSS, in static models (virtual and patient-specific), the rheological difference was not obvious in areas with high WSS, but observable in low WSS areas. In the transient model, the rheological difference of WSS areas with low WSS was enhanced, especially during diastolic period.

Conclusion

Newtonian fluid model could be applicable for PR calculation, but caution needs to be taken when using the Newtonian assumption in simulating WSS especially in severe ICAS cases.

Hemodynamic Versus Anatomic Assessment of Symptomatic Atherosclerotic Middle Cerebral Artery Stenosis: the Relationship Between Pressure Wire Translesional Gradient and Angiographic Lesion Geometry

Background: Intracranial cerebral atherosclerosis (ICAS) is a leading etiology of ischemic stroke. The diagnosis and assessment of intracranial stenosis are shifting from anatomic to hemodynamic for better risk stratification. However, the relationships between lesion geometry and translesional pressure gradient have not been clearly elucidated.

Methods: Patients with symptomatic unifocal M1 middle cerebral artery (M1-MCA) stenosis were consecutively recruited. The translesional pressure gradient was measured with a pressure wire and was recorded as both mean distal/proximal pressure ratios (Pd/Pa) and translesional pressure difference (Pa–Pd). Lesion geometry measured on angiography was recorded as diameter stenosis, minimal lumen diameter, and lesion length. The correlations between pressure-derived and angiography-derived indices were then analyzed.

Results: Forty-three patients were analyzed. A negative correlation was found between Pd/Pa and diameter stenosis (r = −0.371; p = 0.014) and between Pa – Pd and minimal lumen diameter (r = −0.507; p = 0.001). A positive correlation was found between Pd/Pa and minimal lumen diameter (r = 0.411; p = 0.006) and between Pa – Pd and diameter stenosis (r = 0.466; p = 0.002).

Conclusions: In a highly selected ICAS subgroup, geometric indices derived from angiography correlate significantly with translesional pressure gradient indices. However, the correlation strength is weak-to-moderate, which implies that anatomic assessment could only partly reflect hemodynamic status. Translesional pressure gradient measured by pressure wire may serve as a more predictive marker of ICAS severity. More factors need to be identified in further studies.