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.

Hemodynamic significance of intracranial atherosclerotic disease and ipsilateral imaging markers of cerebral small vessel disease

INTRODUCTION

Cerebral small vessel disease (CSVD) commonly exists in patients with symptomatic intracranial atherosclerotic disease (sICAD). We aimed to investigate the associations of hemodynamic features of sICAD lesions with imaging markers and overall burden of CSVD.

PATIENTS AND METHODS

Patients with anterior-circulation sICAD (50%-99% stenosis) were analyzed in this cross-sectional study. Hemodynamic features of a sICAD lesion were quantified by translesional pressure ratio (PR = Pressurepost-stenotic/Pressurepre-stenotic) and wall shear stress ratio (WSSR = WSSstenotic-throat/WSSpre-stenotic) via CT angiography-based computational fluid dynamics modeling. PR ⩽median was defined as low ("abnormal") PR, and WSSR ⩾ fourth quartile as high ("abnormal") WSSR. For primary analyses, white matter hyperintensities (WMHs), lacunes, and cortical microinfarcts (CMIs) were assessed in MRI and summed up as overall CSVD burden, respectively in ipsilateral and contralateral hemispheres to sICAD. Enlarged perivascular spaces (EPVSs) and cerebral microbleeds (CMBs) were assessed for secondary analyses.

RESULTS

Among 112 sICAD patients, there were more severe WMHs, more lacunes and CMIs, and more severe overall CSVD burden ipsilaterally than contralaterally (all p < 0.05). Abnormal PR and WSSR (vs normal PR and WSSR) was significantly associated with moderate-to-severe WMHs (adjusted odds ratio = 10.12, p = 0.018), CMI presence (5.25, p = 0.003), and moderate-to-severe CSVD burden (12.55; p = 0.033), ipsilaterally, respectively independent of contralateral WMHs, CMI(s), and CSVD burden. EPVSs and CMBs were comparable between the two hemispheres, with no association found with the hemodynamic metrics.

DISCUSSION AND CONCLUSION

There are more severe WMHs and CMI(s) in the hemisphere ipsilateral than contralateral to sICAD. The hemodynamic significance of sICAD lesions was independently associated with severities of WMHs and CMI(s) ipsilaterally.

Abstract WMP84: Symptomatic Intracranial Atherosclerotic Plaques: Different Morphological Features In The Anterior Versus Posterior Circulation

Introduction: We compared the morphology of intracranial atherosclerotic plaques in the anterior versus posterior circulation, using three-dimensional rotational angiography (3DRA).

Methods: We prospectively recruited adult patients with acute ischemic stroke or transient ischemic attack attributed to high-grade (60-99%), atherosclerotic intracranial stenosis as confirmed by 3DRA. We assessed the plaque morphology in 3DRA, including the percentage of luminal stenosis, smooth/irregular/ulcerative plaque surface contour, plaque thickness, length, eccentricity, upstream plaque shoulder angulation, longitudinal distribution of the maximal stenosis, and adjoining branch atheromatous disease (BAD). We compared characteristics of patients with middle cerebral artery-M1 (MCA-M1) and basilar artery (BA) plaques, and the plaque morphology in the two subgroups.

Results: Overall, 164 and 17 patients respectively with MCA-M1 and BA plaques were analyzed, with similar age (medians 60 versus 62 years), sex (male 64.6 versus 52.9%) and history of common vascular risk factors. The percentage of luminal stenosis (medians 77 versus 81%), proportion of smooth/irregular/ulcerative plaque surface contour, upstream plaque shoulder angulation (32.1 versus 25.8 °), longitudinal distribution of the maximal stenosis, and presence of adjoining BAD (56.7 versus 64.7%) were similar between MCA-M1 and BA plaques. However, BA plaques were thicker (1.5 versus 1.3mm; p=0.03) and longer (16.4 versus 8.4mm; p<0.001), but less likely eccentric (70.6 versus 88.4%; p=0.039).

Conclusions: There were differences in the morphology of symptomatic atherosclerotic plaques in anterior and posterior circulations, independent of demographics and common vascular risk factors. Different artery geometry and the hemodynamics may underlie such differences.

Thromboembolic Risks with Concurrent Direct Oral Anticoagulants and Antiseizure Medications: A Population-Based Analysis

BACKGROUND AND OBJECTIVE

Drug-drug interactions between direct oral anticoagulants (DOAC) and antiseizure medications via the cytochrome P450 (CYP) or the P-glycoprotein (P-gp) systems may lead to under-anticoagulation. The clinical relevance of these interactions is unclear. We aimed to elucidate the risk of thromboembolism with concurrent DOAC and CYP/P-gp modulating antiseizure medications.

METHODS

In this propensity score-weighted population-based retrospective cohort study, we used competing risk regression analyses to determine the risks of ischemic stroke, venous thromboembolism, and death in DOAC recipients taking CYP/P-gp-modulating antiseizure medications (phenytoin, valproate, levetiracetam, carbamazepine, or phenobarbital) versus those taking CYP/P-gp-neutral antiseizure medications (pregabalin, gabapentin, or clobazam). We also performed secondary analyses for the epilepsy and atrial fibrillation subgroups.

RESULTS

Among DOAC users, CYP/P-gp-modulating antiseizure medications were collectively associated with an increased risk of ischemic stroke (adjusted hazard ratio 1.28, 95% confidence interval 1.05-1.57, p = 0.017). In addition, phenytoin (adjusted hazard ratio 1.34, 95% confidence interval 1.07-1.68, p = 0.011) and valproate (adjusted hazard ratio 1.38, 95% confidence interval 1.10-1.74, p = 0.006) were associated with increased mortality. In the epilepsy subgroup, the risk of ischemic stroke and venous thromboembolism did not differ between CYP/P-gp-modulating and CYP/P-gp-neutral antiseizure medications.

CONCLUSIONS

Although CYP/P-gp-modulating antiseizure medications were associated with an increased risk of ischemic stroke when paired with DOAC in the primary analysis, such a phenomenon was not found among patients with epilepsy who took phenytoin, valproate, or levetiracetam with DOAC. Therefore, these antiseizure medication options among patients with epilepsy with concurrent DOAC should not be restricted solely based on their potential drug-drug interactions. Yet, the increased mortality during concurrent use of DOAC with phenytoin or valproate might call for caution.

Abstract P678: Elevated Neutrophil to Lymphocyte Ratio Associated With Increased Risk of Recurrent Vascular Events in Older Minor Stroke or TIA Patients

Background: The risk of recurrent stroke following a minor stroke or transient ischemic attack (TIA) is high, when inflammation might play an important role. We aimed to evaluate the value of neutrophil-to-lymphocyte ratio (NLR) in predicting composite cardiovascular events in patients with minor stroke and TIA.

Methods: Consecutive patients with acute minor stroke or TIA admitted within 24 hours of symptoms onset during a 5-year period in a prospective stroke registry were analyzed. We calculated the NLR dividing absolute neutrophil count by absolute lymphocyte count tested within 24 hours of admission. NLR ≥ 4th quartile was defined as high NLR. A composite outcome was defined as ischemic stroke, acute coronary syndrome or vascular death within 1 year. We investigated associations between NLR and the composite outcome in univariate and multivariate analyses, among all patients and in those aged over 60 years (i.e., older patients).

Results: Overall, 841 patients (median age 68 years; 60.4% males) were recruited. No significant independent association was found between NLR and the composite outcome in multivariate analysis in the overall cohort. Among the 612 older patients (median age 73 years; 59.2% males), the median NLR was 2.76 (interquartile range 1.96-4.00) and 148 (24.2%) patients had high NLR. The composite outcome occurred in 77 (12.6%) older patients, who were more likely to have a high NLR (39.0% versus 22.1%; p=0.001) than those without a composite outcome. In multivariate logistic regression, high NLR (adjusted odds ratio 2.00; 95% confidence interval 1.07-3.75; p=0.031) was independently associated with the composite outcome in older patients.

Conclusions: In older patients with acute minor stroke or TIA, a higher NLR is an independent predictor of subsequent cardiovascular events, indicating inflammation as an important factor and potential therapeutic target for secondary prevention of such patients.

Abstract WP121: An Evaluation of Hemodynamics Across Intracranial Steno-occlusive Lesions by Computational Fluid Dynamics

Introduction: Intracranial atherosclerotic steno-occlusive disease (ICAS) is a major cause of stroke worldwide and portends a high risk of recurrence. Computational fluid dynamics (CFD) is a novel technique developed to solve and analyze the dynamic effects of fluid flow. We aimed to analyse hemodynamics across ICAS using CFD on processed CTA images and explore the correlation between the degree of arterial stenosis and hemodynamic flow status.

Methods: We recruited patients with symptomatic ICAS from Acute Stroke Unit, Prince of Wales Hospital. All patients received CTA and DSA as vascular workup. Using CFD analysis of processed CTA images, we first defined the hemodynamic parameters, including pressure difference, pressure ratio, pressure gradient, shear strain rate ratio (SSR), wall shear stress (WSS) ratio and velocity ratio, across the stenosed vessels, and then we correlated the severity of stenosis as defined by DSA, with these parameters.

Results: Among the 53 recruited patients (mean age 62.9 years, 69.8% males), 45 (85%) had lesions in the anterior circulation. The severity of stenosis showed a weak-to-moderate correlation with pressure difference (rs=0.392, p=0.004), pressure ratio (rs=-0.429, p=0.001) and pressure gradient (rs=0.419, p=0.002). There was no significant correlation between the severity of stenosis with SSR ratio, WSS ratio and velocity ratio. Among patients with anterior circulation stroke or TIA, the severity of stenosis showed a weak to moderate correlation with pressure difference (rs=0.381, p=0.01), pressure ratio (rs=-0.426, p=0.004) and pressure gradient (rs=0.407, p=0.005). For patients with posterior circulation stroke or TIA, the severity of stenosis was strongly correlated with pressure difference (rs=0.714, p=0.047) and pressure ratio (rs=-0.714, p=0.047); and very strongly correlated with velocity ratio (rs=0.833, p=0.01).

Conclusions: The severity of ICAS showed only weak-to-moderate correlation with hemodynamic parameters across the culprit lesion. Thus, risk stratification and treatment based solely on stenotic severity may be inadequate. Our findings may guide further research in estimating stroke risks and selection of high-risk patients who may benefit from adjunctive treatments.

Abstract T P104: Remodeling of Intracranial Atherosclerotic Plaques

Background: Rupture-prone plaques may cause recurrent thrombo-embolic stroke. Little is known how symptomatic intracranial atherosclerotic plaques would remodel under current treatment.

Method: We recruited acute stroke patients with high-grade (>70%) symptomatic intracranial atherosclerotic stenosis for optimal medical treatment. Interval changes of plaque morphology were assessed by 3D-rotational angiography at baseline and 12 months. Morphological parameters included plaque surface (smooth/irregular/ulcerated), thickness, length (total length, maximal stenosis length), maximal stenosis distribution (proximal/central/distal), thickness-to-length ratio (ratio=thickness/total length), eccentricity, and plaque upstroke angulation. We stratified angiographic outcomes into 1) Progressive (surface morphology evolved from smooth to become irregular/ulcerated); 2) Static (surface morphology unchanged); and 3) Regressive (surface morphology from irregular/ulcerated to smooth).

Results: Among the recruited 32 patients (age 66.3±8.9yrs, male 71.9%), we observed significant difference in plaque surface (ulcerated: 21.9% to 9.4%, p=0.01), thickness (1.54±0.41mm to 1.33±0.45mm, p=0.01), maximal stenosis distribution (central: 50.0% to 65.6%, p<0.001), and thickness-to-length ratio (0.30±0.13 to 0.26±0.10, p=0.046). Plaque surface morphology remained unchanged in 25 patients (78.1%), progressive in 2 patients (6.3%), and regressive in 5 patients (15.6%, Figure). One patient (3%) developed recurrent ischemic stroke.

Conclusion: Symptomatic intracranial atherosclerotic plaques may regress with medical therapy alone. Healing of ulcers and positive remodeling are evident in some plaques.