Statin Pretreatment and Microembolic Signals in Large Artery Atherosclerosis

Brazilian Angiology and Vascular Surgery Society Guidelines for the treatment of extracranial cerebrovascular disease

Extracranial cerebrovascular disease has been the subject of intense research throughout the world, and is of paramount importance for vascular surgeons. This guideline, written by the Brazilian Society of Angiology and Vascular Surgery (SBACV), supersedes the 2015 guideline. Non-atherosclerotic carotid artery diseases were not included in this document. The purpose of this guideline is to bring together the most robust evidence in this area in order to help specialists in the treatment decision-making process. The AGREE II methodology and the European Society of Cardiology system were used for recommendations and levels of evidence. The recommendations were graded from I to III, and levels of evidence were classified as A, B, or C. This guideline is divided into 11 chapters dealing with the various aspects of extracranial cerebrovascular disease: diagnosis, treatments and complications, based on up-to-date knowledge and the recommendations proposed by SBACV.

Dyslipidemia Treatment and Cerebrovascular Disease: Evidence Regarding the Mechanism of Stroke

Dyslipidemia stands as a significant risk factor for stroke, on par with the impact of hypertension, diabetes, and smoking. While the role of dyslipidemia is firmly established in the context of coronary artery disease, its influence on strokes remains somewhat enigmatic. This complexity likely arises from the diverse mechanisms underpinning strokes, which encompass a heterogeneous spectrum (hemorrhagic and ischemic; large artery atherosclerosis, small vessel occlusion, cardioembolism, and etc.). The extent to which lipid-lowering treatments affect stroke outcomes may vary depending on the specific stroke subtype. For instance, in cases of large artery atherosclerosis (LAA), the optimal target level of low-density lipoprotein cholesterol (LDL-C) is relatively clear. However, when dealing with other stroke subtypes like small vessel occlusion or cardioembolism, the appropriate LDL-C target remains uncertain. Furthermore, reperfusion therapy has emerged as the foremost treatment for acute ischemic stroke. Nevertheless, the precise relationship between LDL-C levels and outcomes in patients undergoing reperfusion therapy remains shrouded in uncertainty. Consequently, we have undertaken an in-depth exploration of the existing evidence supporting the utilization of lipid-lowering medications such as statins, ezetimibe, and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors. Our objective is to elucidate their role in secondary stroke prevention and the management of dyslipidemia across the various stroke subtypes.

Therapeutic Induction of Collateral Flow

Therapeutic induction of collateral flow as a means to salvage tissue and improve outcome from acute ischemic stroke is a promising approach in the era in which endovascular therapy is no longer time-dependent but collateral-dependent. The importance of collateral flow enhancement as a therapeutic for acute ischemic stroke extends beyond those patients with large amounts of salvageable tissue. It also has the potential to extend the time window for reperfusion therapies in patients who are ineligible for endovascular thrombectomy. In addition, collateral enhancement may be an important adjuvant to neuroprotective agents by providing a more robust vascular route for which treatments can gain access to at risk tissue. However, our understanding of collateral hemodynamics, including under comorbid conditions that are highly prevalent in the stroke population, has hindered the efficacy of collateral flow augmentation for improving stroke outcome in the clinical setting. This review will discuss our current understanding of pial collateral function and hemodynamics, including vasoactivity that is critical for enhancing penumbral perfusion. In addition, mechanisms by which collateral flow can be increased during acute ischemic stroke to limit ischemic injury, that may be different depending on the state of the brain and vasculature prior to stroke, will also be reviewed.

Micro-embolic signal monitoring in stroke subtypes: A systematic review and meta-analysis of 58 studies

Introduction

Micro-embolic signals (MESs) detected using transcranial Doppler (TCD) help in risk stratification in stroke patients. A systematic review and meta-analysis were performed to estimate the prevalence of MES and its association with stroke recurrence, functional outcome, and mortality in different stroke subtypes.

Methods

A comprehensive literature search was conducted before 26^th January 2021 in PubMed, Embase, Google Scholar, Cochrane Library, and ClinicalTrials.gov. Studies were identified that used TCD to detect MES in stroke/TIA patients. Pooled prevalence and odds ratio (OR) along with 95% confidence interval (95% CI) were calculated for different outcome measures. The entire statistical analysis was conducted in R version 3.6.2.

Findings

Fifty-eight studies involving 5123 patients (1329 MES+, 3794 MES-) were included in our meta-analysis. The pooled prevalence of MES among all acute stroke/TIA patients was 30% (95% CI 25-34%). The pooled prevalence adjusted after the trim-and-fill analysis among all acute stroke/TIA patients was 18% (95% CI 14-23%). The prevalence of MES was high among all stroke subtypes except in patients with small vessel disease (SVD). In patients with new-onset stroke/TIA, the presence of MES was associated with a high risk of recurrence of cerebral ischemia (OR 4.03; 95% CI 2.38-6.82). Although no significant association was observed for the presence of MES with increased mortality (OR 2.37; 95% CI 0.75-7.50) and poor functional outcome (OR 2.11; 95% CI 0.20-22.50) among patients with new-onset stroke/TIA, this could only be determined in a smaller sample size of 477 patients.

Conclusions

Our meta-analysis showed a 30% prevalence of MES following acute stroke/TIA. The presence of MES increased the chance of recurrence of cerebral ischemia but was not associated with poor functional outcomes and mortality in the studied subgroup.

Premorbid Use of Statin and Outcome of Acute Ischemic Stroke After Intravenous Thrombolysis: A Meta-Analysis

Background: The association between the premorbid use of statin and the early outcomes of acute ischemic stroke (AIS) after intravenous thrombolysis (IVT) remains uncertain. We performed a meta-analysis of observational studies to evaluate the influence of the premorbid use of statin on functional outcome and symptomatic intracranial hemorrhage (SIH) in AIS after IVT. Methods: Relevant studies were identified by search of PubMed, Embase, and Cochrane's Library databases. Only studies with multivariate analyses were included. A random-effect model, incorporating inter-study heterogeneity, was used to pool the results. Results: Twenty observational studies with 20,752 AIS patients who were treated with IVT were included. The pooled results showed that the premorbid use of statin was not associated with improved 3-month favorable functional outcome [odds ratio (OR): 1.05, 95% confidence interval (CI): 0.87-1.26, p = 0.60, I ² = 52%), 3-month functional independence (OR: 1.13, 95% CI: 0.96-1.33, p = 0.15, I ² = 52%), or 3-month mortality (OR: 1.12, 95% CI: 0.94-1.34, p = 0.20, I ² = 20%). Moreover, the premorbid use of statin was associated with an increased risk of SIH in AIS after IVT (OR: 1.48, 95% CI: 1.12-1.95, p = 0.006, I ² = 60%). Subgroup analyses according to study design, adjustment of baseline low-density lipoprotein cholesterol, and definitions of SIH showed consistent results (p-values for subgroup difference all >0.05). Conclusions: The premorbid use of statin is not associated with improved functional outcomes or mortality but is associated with a higher risk of SIH in AIS patients after IVT.

Statins in Neuro-ophthalmology

Statins are effective and well-tolerated hypolipidaemic agents which have been increasingly studied for their pleiotropic immunomodulatory and anti-inflammatory effects. Statins have potential therapeutic benefit in a range of neuro-ophthalmological conditions but may also induce or exacerbate certain neurological disorders. This literature review examines evidence from clinical and in vitro studies assessing the effects of statins in myasthenia gravis, myopathy, multiple sclerosis, neuromyelitis optica, idiopathic intracranial hypertension (pseudotumour cerebri), migraine, giant cell arteritis, Bell's palsy, ocular ischaemia, stroke, Alzheimer's disease and Parkinson's disease.

Statin treatment and accrual of covert cerebral ischaemia on neuroimaging: a systematic review and meta-analysis of randomized trials

BACKGROUND AND PURPOSE

Prevention of ischaemic stroke and cardiovascular events is an established benefit of statin therapy, but the effects of statin treatment on the accrual of magnetic resonance imaging (MRI) markers of ischaemic cerebral injury remain unknown. A systematic review was performed to identify all studies that randomized patients with cardiovascular risk factors to statin treatment and assessed the effect of statin treatment on covert infarcts (asymptomatic, evident only on neuroimaging) and white matter hyperintensity (WMH) accrual on MRI.

METHODS

A systematic review in MEDLINE and Scopus from inception to 23 October 2019 was performed. A random-effects model was used to calculate the pooled estimates of the crude risk ratios and standardized mean differences.

RESULTS

Data from three randomized controlled trials (1430 participants) were included evaluating the effect of rosuvastatin (10 mg/day) in 668 hypertensive patients older than 60 years of age over 5 years, pravastatin (40 mg/day) in 554 elderly people more than 70 years of age over 3 years and simvastatin (20 mg/day) in 208 patients with asymptomatic middle cerebral artery stenosis over 2 years. Patients randomized to statin treatment had decreased accrual of new covert infarcts (risk ratio 0.63, 95% confidence interval 0.46-0.88) during a mean follow-up of 2-6 years. Only one study reported WMH decreased volume change in patients randomized to statin treatment compared to patients randomized to non-statin treatment (standardized mean difference -1.17; 95% confidence interval -1.33, -1.00).

CONCLUSION

Our findings suggest that, in addition to stroke prevention, statin treatment can reduce the accrual of covert MRI markers of ischaemic cerebral injury.

Statins in Stroke

BACKGROUND

Stroke is a major cause of mortality and disability in modern societies. Statins are effective medications in decreasing cardiovascular events through lipid lowering and pleiotropic effects.

OBJECTIVE

To summarize current evidence regarding the role of statins in the prevention and management of stroke.

METHODS

A narrative review of current evidence regarding the effect of statins in stroke management. Electronic searches of MEDLINE, EMBASE and Cochrane Databases were performed.

RESULTS

In primary prevention of stroke in patients with risk factors but no established cardiovascular disease, potent statins such as atorvastatin and rosuvastatin have shown some benefits, but the clinical relevance of this effect is questionable. In populations at higher risk of stroke, such as patients with established coronary heart disease, the majority of relevant studies have shown a beneficial effect of statins in preventing stroke. Similarly, in patients with a previous cerebrovascular event, there is a clear benefit of statins for the prevention of recurrent events. The use of statins is not associated with an increased risk of intracranial bleeding in primary prevention studies. There may be an increased incidence of non-fatal hemorrhagic stroke with high dose statins in patients with a previous cerebrovascular event. Patients who experience a stroke while on statins should not discontinue statins. In addition, statins are associated with better survival and improved functional outcome when administered during the acute phase of stroke in statin-naive patients. In contrast, statins do not confer any benefit in patients with acute ischemic stroke who receive thrombolysis.

CONCLUSION

Treatment with statins prevents ischemic stroke, especially in patients with high cardiovascular risk and established atherosclerotic disease. It seems that both lipid lowering and pleiotropic effects contribute to these effects.

Relationship between 'on-treatment platelet reactivity', shear stress, and micro-embolic signals in asymptomatic and symptomatic carotid stenosis

BACKGROUND

Assessment of 'high on-treatment platelet reactivity (HTPR)' could enhance understanding of the pathophysiology of first or recurrent vascular events in carotid stenosis patients on antiplatelet therapy.

METHODS

This prospective, multi-centre study assessed antiplatelet-HTPR status and its relationship with micro-emboli signals (MES) in asymptomatic vs. symptomatic ≥ 50-99% carotid stenosis. Platelet function/reactivity was assessed under 'moderately high shear stress' with the PFA-100^® and 'low shear stress' with VerifyNow^® and Multiplate^® analysers. Bilateral 1-h transcranial Doppler ultrasound of the middle cerebral arteries classified patients as MES + ve or MES - ve.

RESULTS

Data from 34 asymptomatic patients were compared with 43 symptomatic patients in the 'early phase' (≤ 4 weeks) and 37 patients in the 'late phase' (≥ 3 months) after TIA/ischaemic stroke. Median daily aspirin doses were higher in early symptomatic (225 mg; P < 0.001), but not late symptomatic (75 mg; P = 0.62) vs. asymptomatic patients (75 mg). There was a lower prevalence of aspirin-HTPR in early (28.6%; P = 0.028), but not late symptomatic (38.9%; P = 0.22) compared with asymptomatic patients (56.7%) on the PFA-100^®, but not on the VerifyNow^® or Multiplate^® (P ≤ 0.53). Early symptomatic patients had a higher prevalence of aspirin-HTPR on the PFA-100^® (28.6%) vs. VerifyNow^® (9.5%; P = 0.049), but not Multiplate^® assays (11.9%, P = 0.10). There was no difference in aspirin-HTPR prevalence between any symptomatic vs. asymptomatic MES + ve or MES - ve subgroup.

DISCUSSION

Recently symptomatic moderate-severe carotid stenosis patients had a lower prevalence of aspirin-HTPR than their asymptomatic counterparts on the PFA-100^®, likely related to higher aspirin doses. The prevalence of antiplatelet-HTPR was positively influenced by higher shear stress levels, but not MES status.

Asymptomatic Carotid Stenosis Is Associated With Circadian and Other Variability in Embolus Detection

Background and Purpose: Variability in transcranial Doppler (TCD) detection of embolic signals (ES) is important for risk stratification. We tested the effect of time of day on ES associated with 60–99% asymptomatic carotid stenosis.

Materials and Methods: Subjects were from the Asymptomatic Carotid Stenosis Embolus Detection (ASED) Study such that half were previously ES-positive and half ES-negative with 6-monthly 60-min TCD monitoring. All underwent bilateral TCD monitoring for two 12-h sessions separated by 24 h. ES detection rates were calculated using 6 and 4-h intervals from midnight and effective TCD monitoring time.

Results: Ten subjects (8 male, mean age 79.5 years) were monitored. Over 24 h, 5/10 study arteries with 60–99% asymptomatic carotid stenosis were ES-positive (range 1–28 ES/artery, 56 total ES from 177.9 total effective monitoring hours). The remaining five study arteries and all eight successfully monitored contralateral arteries were ES-negative. Using 6-h intervals the mean ES detection rate peaked at 0600-midday (0.64/h) and was lowest 1800-midnight (0.09/h) with an incidence rate ratio of 7.26 (95% CI 2.52–28.64, P ≤ 0.001). Using 4-h intervals the mean ES detection rate peaked at 0800-midday (0.64/h) and was lowest midnight-0400 (0.12/h) with an incidence rate ratio of 5.51 (95% CI 1.78–22.67, P = 0.001).

Conclusions: Embolism associated with asymptomatic carotid stenosis shows circadian variation with highest rates 4–6 h before midday. This corresponds with peak circadian incidence of stroke and other vascular complications. These and ASED Study results show that monitoring frequency, duration, and time of day are important in ES detection.

Association of statin pretreatment with collateral circulation and final infarct volume in acute ischemic stroke patients: A meta-analysis

BACKGROUND AND AIMS

Statin pretreatment (SP) is associated with improved outcomes in acute ischemic stroke (AIS) patients. Collateral circulation status and final infarct volume (FIV) are independent predictors of functional outcome in AIS.

METHODS

We sought to evaluate the association of SP with collateral circulation and FIV in AIS patients. We used a random-effects model for all the analyses, and pooled standardized mean differences (SMDs) and odds ratios (OR) on the FIV and collateral status according to SP history, respectively.

RESULTS

We identified 9 eligible studies (1186 AIS patients). History of SP was associated with lower FIV (SMD = 0.25, 95%CI: 0.07-0.42, p = 0.005) compared to negative history of SP. A trend towards good collateral scores was observed in the SP group (OR = 1.45; 95% CI, 0.92-2.29, p = 0.11). Subgroup analysis demonstrated reduced FIV among atherosclerotic stroke patients with history of SP (SMD = 0.49; 95% CI, 0.19-0.80, p = 0.001).

CONCLUSIONS

SP appears to be associated with decreased FIV, especially in atherosclerotic AIS.