Clopidogrel Versus Dipyridamole in Addition to Aspirin in Reducing Embolization Detected With Ambulatory Transcranial Doppler

Carotid Artery Stenosis: A Look Into the Diagnostic and Management Strategies, and Related Complications

Carotid stenosis (CS) is a buildup of atherosclerotic plaque within the artery leading to a wide range of symptoms, from mild symptoms, including blurred vision and confusion, to much more life-threatening presentations, including paralysis due to stroke. The presentation is insidious, with symptoms exhibiting predominantly at severe stenosis; hence the emphasis is placed on the importance of early diagnosis, treatment, and lifestyle modifications. CS is seen undergoing almost the same pathogenesis of any atherosclerotic plaque formation, from endothelial damage of the artery lumen to the formation of a fibrous cap with a foam cell, lipid-filled core. The findings of our review article were consistent with the recent literature, depicting that comorbid hypertension, diabetes, and chronic kidney disease (CKD), and lifestyle aspects, including smoking and diet, played the most salient role in plaque development. Among several imaging modalities, duplex ultrasound (DUS) imaging is the widely preferred method in clinical practice. Carotid endarterectomy (CEA) and carotid stenting are the primarily advocated procedures for symptomatic severe stenosis, with similar long-term outcomes. Although, earlier clinical trials showed promising results in mitigating the risk of stroke among asymptomatic severe CS with surgical intervention. However, recent advancements have shifted the focus to medical management alone due to comparable results among the asymptomatic population. Both surgical and medical regimens are beneficial in treating patients, but it is still an ongoing debate as to which is predominantly superior. The currently advancing trials and research will help elucidate definitive guidelines. However, the massive impact of lifestyle modifications advocates some degree of individualized multidisciplinary management strategies.

Dual Antiplatelet Therapy Is Associated with Increased Risk of Bleeding and Decreased Risk of Stroke Following Carotid Endarterectomy

BACKGROUND

Despite many patients undergoing carotid endarterectomy (CEA) being on dual antiplatelet therapy (DAPT) for cardiac or neurologic indications, the impact of such therapy on perioperative outcomes remains unclear. We aim to compare rates of postoperative bleeding, stroke and major adverse events (stroke, death or MI) among patients on Aspirin alone (ASAA) versus DAPT (Clopidogrel and Aspirin).

METHODS

Patients undergoing CEA for carotid artery stenosis between 2010 and 2021 in the Vascular Quality Initiative (VQI) were included. We excluded patients undergoing concomitant or re-do operations or patients with missing antiplatelet information. Propensity score matching was performed between the 2 groups ASAA and DAPT based on age, sex, race, presenting symptoms, major comorbidities [hypertension, diabetes and coronary artery disease (CAD)], degree of ipsilateral stenosis, presence of contralateral occlusion, as well as preoperative medications. Intergroup differences between the treatment groups and differences in perioperative outcomes were tested with the McNemar's test for categorical variables and paired t-test or Wilcoxon matched-pairs signed-rank test for continuous variables where appropriate. Relative risks with 95% confidence intervals were estimated as the ratio of the probability of the outcome event in the patients treated within each treatment group.

RESULTS

A total of 125,469 patients were included [ASAA n = 82,920 (66%) and DAPT n = 42,549 (34%)]. Patients on DAPT were more likely to be symptomatic, had higher rates of CAD, prior percutaneous coronary intervention or coronary artery bypass grafting, and higher rates of diabetes. After propensity score matching, the DAPT group had an increased rate of bleeding complications (RR: 1.6: 1.4-1.8, P < 0.001) as compared with those on ASAA despite being more likely to receive both drains and protamine. In addition, patients on DAPT had a slight decrease in the risk of in-hospital stroke as compared with patients on ASAA (RR: 0.80: 0.7-0.9, P = 0.001).

CONCLUSIONS

This large multi-institutional study demonstrates a modest decrease in the risk of in-hospital stroke for patients on DAPT undergoing CEA as compared with those on ASAA. This small benefit is at the expense of a significant increase in the risk of perioperative bleeding events incurred by those on DAPT at the time of CEA. This analysis suggests avoiding DAPT when possible, during CEA.

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.

Platelet Biomarkers in Patients with Atherosclerotic Extracranial Carotid Artery Stenosis: A Systematic Review

OBJECTIVE

The aim was to enhance understanding of the role of platelet biomarkers in the pathogenesis of vascular events and risk stratifying patients with asymptomatic or symptomatic atherosclerotic carotid stenosis.

DATA SOURCES

Systematic review conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

REVIEW METHODS

A systematic review collated data from 1975 to 2020 on ex vivo platelet activation and platelet function/reactivity in patients with atherosclerotic carotid stenosis.

RESULTS

Forty-three studies met the inclusion criteria; the majority included patients on antiplatelet therapy. Five studies showed increased platelet biomarkers in patients with ≥ 30% asymptomatic carotid stenosis (ACS) vs. controls, with one neutral study. Preliminary data from one study suggested that quantification of "coated platelets" in combination with stenosis severity may aid risk stratification in patients with ≥ 50% - 99% ACS. Platelets were excessively activated in patients with ≥ 30% symptomatic carotid stenosis (SCS) vs. controls (≥ 11 positive studies and one neutral study). Antiplatelet-High on Treatment Platelet Reactivity (HTPR), previously called "antiplatelet resistance", was observed in 23% - 57% of patients on aspirin, with clopidogrel-HTPR in 25% - 100% of patients with ≥ 50% - 99% ACS. Aspirin-HTPR was noted in 9.5% - 64% and clopidogrel-HTPR in 0 - 83% of patients with ≥ 50% SCS. However, the data do not currently support the use of ex vivo platelet function/reactivity testing to tailor antiplatelet therapy outside of a research setting. Platelets are excessively activated (n = 5), with increased platelet counts (n = 3) in recently symptomatic vs. asymptomatic patients, including those without micro-emboli on transcranial Doppler (TCD) monitoring (n = 2). Most available studies (n = 7) showed that platelets become more reactive or activated following carotid endarterectomy or stenting, either as an acute phase response to intervention or peri-procedural treatment.

CONCLUSION

Platelets are excessively activated in patients with carotid stenosis vs. controls, in recently symptomatic vs. asymptomatic patients, and may become activated/hyper-reactive following carotid interventions despite commonly prescribed antiplatelet regimens. Further prospective multicentre studies are required to determine whether models combining clinical, neurovascular imaging, and platelet biomarker data can facilitate optimised antiplatelet therapy in individual patients with carotid stenosis.

Simultaneous assessment of plaque morphology, cerebral micro-embolic signal status and platelet biomarkers in patients with recently symptomatic and asymptomatic carotid stenosis

The relationship between plaque morphology, cerebral micro-embolic signals (MES) and platelet biomarkers in carotid stenosis patients warrants investigation.We combined data from two prospective, observational studies to assess carotid plaque morphology and relationship with cerebral MES and platelet biomarkers in patients with recently symptomatic (≤4 weeks of transient ischaemic attack (TIA)/ischaemic stroke) versus asymptomatic carotid stenosis. Plaque morphology on ultrasound was graded with Grey-Scale Median (GSM) and Gray-Weale (GW) scoring. Bilateral transcranial Doppler ultrasound classified patients as 'MES+ve' or 'MES-ve'. Full blood counts were analysed and flow cytometry quantified CD62P and CD63 expression, leucocyte-platelet complexes and reticulated platelets.Data from 42 recently symptomatic carotid stenosis patients were compared with those from 36 asymptomatic patients. There were no differences in median GSM scores between symptomatic and asymptomatic patients (25 vs. 30; P = 0.31) or between MES+ve vs. MES-ve symptomatic patients (36 vs. 25; P = 0.09). Symptomatic patients with GSM-echodense plaques (GSM ≥25) had higher platelet counts (228 vs. 191 × 10⁹/L), neutrophil-platelet (3.3 vs. 2.7%), monocyte-platelet (6.3 vs. 4.55%) and lymphocyte-platelet complexes (2.91 vs. 2.53%) than 'asymptomatic patients with GSM-echodense plaques' (P ≤ 0.03).Recently, symptomatic carotid stenosis patients with 'GSM-echodense plaques' have enhanced platelet production/secretion/activation compared with their asymptomatic counterparts. Simultaneous assessment with neurovascular imaging and platelet biomarkers may aid risk-stratification in carotid stenosis.

Management of carotid stenosis for primary and secondary prevention of stroke: state-of-the-art 2020: a critical review

Carotid atherosclerotic plaque is encountered frequently in patients at high cardiovascular risk, especially in the elderly. When plaque reaches 50% of carotid lumen, it induces haemodynamically significant carotid stenosis, for which management is currently at a turning point. Improved control of blood pressure, smoking ban campaigns, and the widespread use of statins have reduced the risk of cerebral infarction to <1% per year. However, about 15% of strokes are still secondary to a carotid stenosis, which can potentially be detected by effective imaging techniques. For symptomatic carotid stenosis, current ESC guidelines put a threshold of 70% for formal indication for revascularization. A revascularization should be discussed for symptomatic stenosis over 50% and for asymptomatic carotid stenosis over 60%. This evaluation should be performed by ultrasound as a first-line examination. As a complement, computed tomography angiography (CTA) and/or magnetic resonance angiography are recommended for evaluating the extent and severity of extracranial carotid stenosis. In perspective, new high-risk markers are currently being developed using markers of plaque neovascularization, plaque inflammation, or plaque tissue stiffness. Medical management of patient with carotid stenosis is always warranted and applied to any patient with atheromatous lesions. Best medical therapy is based on cardiovascular risk factors correction, including lifestyle intervention and a pharmacological treatment. It is based on the tri-therapy strategy with antiplatelet, statins, and ACE inhibitors. The indications for carotid endarterectomy (CEA) and carotid artery stenting (CAS) are similar: for symptomatic patients (recent stroke or transient ischaemic attack ) if stenosis >50%; for asymptomatic patients: tight stenosis (>60%) and a perceived high long-term risk of stroke (determined mainly by imaging criteria). Choice of procedure may be influenced by anatomy (high stenosis, difficult CAS or CEA access, incomplete circle of Willis), prior illness or treatment (radiotherapy, other neck surgery), or patient risk (unable to lie flat, poor AHA assessment). In conclusion, neither systematic nor abandoned, the place of carotid revascularization must necessarily be limited to the plaques at highest risk, leaving a large place for optimized medical treatment as first line management. An evaluation of the value of performing endarterectomy on plaques considered to be at high risk is currently underway in the ACTRIS and CREST 2 studies. These studies, along with the next result of ACST-2 trial, will provide us a more precise strategy in case of carotid stenosis.

Multiple versus fewer antiplatelet agents for preventing early recurrence after ischaemic stroke or transient ischaemic attack

BACKGROUND

Stroke is a leading cause of morbidity and mortality worldwide. Antiplatelet agents are considered to be the cornerstone for secondary prevention of stroke, but the role of using multiple antiplatelet agents early after stroke or transient ischaemic attack (TIA) to improve outcomes has not been established.

OBJECTIVES

To determine the effectiveness and safety of initiating, within 72 hours after an ischaemic stroke or TIA, multiple antiplatelet agents versus fewer antiplatelet agents to prevent stroke recurrence. The analysis explores the evidence for different drug combinations.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (last searched 6 July 2020), the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 7 of 12, 2020) (last searched 6 July 2020), MEDLINE Ovid (from 1946 to 6 July 2020), Embase (1980 to 6 July 2020), ClinicalTrials.gov, and the WHO ICTRP. We also searched the reference lists of identified studies and reviews and used the Science Citation Index Cited Reference search for forward tracking of included studies.

SELECTION CRITERIA

We selected all randomised controlled trials (RCTs) that compared the use of multiple versus fewer antiplatelet agents initiated within 72 hours after stroke or TIA.

DATA COLLECTION AND ANALYSIS

We extracted data from eligible studies for the primary outcomes of stroke recurrence and vascular death, and secondary outcomes of myocardial infarction; composite outcome of stroke, myocardial infarction, and vascular death; intracranial haemorrhage; extracranial haemorrhage; ischaemic stroke; death from all causes; and haemorrhagic stroke. We computed an estimate of treatment effect and performed a test for heterogeneity between trials. We analysed data on an intention-to-treat basis and assessed bias for all studies. We rated the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 15 RCTs with a total of 17,091 participants. Compared with fewer antiplatelet agents, multiple antiplatelet agents were associated with a significantly lower risk of stroke recurrence (5.78% versus 7.84%, risk ratio (RR) 0.73, 95% confidence interval (CI) 0.66 to 0.82; P < 0.001; moderate-certainty evidence) with no significant difference in vascular death (0.60% versus 0.66%, RR 0.98, 95% CI 0.66 to 1.45; P = 0.94; moderate-certainty evidence). There was a higher risk of intracranial haemorrhage (0.42% versus 0.21%, RR 1.92, 95% CI 1.05 to 3.50; P = 0.03; low-certainty evidence) and extracranial haemorrhage (6.38% versus 2.81%, RR 2.25, 95% CI 1.88 to 2.70; P < 0.001; high-certainty evidence) with multiple antiplatelet agents. On secondary analysis of dual versus single antiplatelet agent therapy, benefit for stroke recurrence (5.73% versus 8.06%, RR 0.71, 95% CI 0.62 to 0.80; P < 0.001; moderate-certainty evidence) was maintained as well as risk of extracranial haemorrhage (1.24% versus 0.40%, RR 3.08, 95% CI 1.74 to 5.46; P < 0.001; high-certainty evidence). The composite outcome of stroke, myocardial infarction, and vascular death (6.37% versus 8.77%, RR 0.72, 95% CI 0.64 to 0.82; P < 0.001; moderate-certainty evidence) and ischaemic stroke (6.30% versus 8.94%, RR 0.70, 95% CI 0.61 to 0.81; P < 0.001; high-certainty evidence) were significantly in favour of dual antiplatelet therapy, whilst the risk of intracranial haemorrhage became less significant (0.34% versus 0.21%, RR 1.53, 95% CI 0.76 to 3.06; P = 0.23; low-certainty evidence).

AUTHORS' CONCLUSIONS

Multiple antiplatelet agents are more effective in reducing stroke recurrence but increase the risk of haemorrhage compared to one antiplatelet agent. The benefit in reduction of stroke recurrence seems to outweigh the harm for dual antiplatelet agents initiated in the acute setting and continued for one month. There is lack of evidence regarding multiple versus multiple antiplatelet agents. Further studies are required in different populations to establish comprehensive safety profiles and long-term outcomes to establish duration of therapy.

Cerebral Microembolism in Intracerebral Hemorrhage: A Prospective Case-Control Study

BACKGROUND

Small and remote acute ischemic lesions may occur in up to one-third of patients with spontaneous intracerebral hemorrhage (ICH). Possible mechanisms include cerebral embolism, small vessel disease, blood pressure variability and others. The embolic mechanism has not been adequately studied. Using transcranial Doppler (TCD), we assessed the incidence of spontaneous microembolic signals (MESs) in patients with acute ICH.

METHODS

Twenty acute ICH patients were prospectively evaluated within 48 h of hospital admission. Clinical and imaging data were collected. Continuous TCD monitoring was performed in both middle cerebral arteries for a one-hour period on days 1, 3 and 7 of hospital admission. Monitoring was performed in the emergency room, ICU or ward, according to patient location. We compared the frequency and risk factors for MES in patients with ICH and in 20 age- and gender-matched controls without history of ischemic or hemorrhagic stroke.

RESULTS

The mean age was 57.5 ± 14.1 years, and 60% were male. MESs were detected in 7 patients with ICH and in one control patient without ICH (35% vs 5%, p = 0.048). The frequency of MES on day 1 was 15% (3 of 20 patients), on day 3, 26% (5 of 19 patients) and on day 7, 37.5% (3 of 8 patients). Among patients with ICH, those with MES had a tendency to higher frequencies of dyslipidemia (83% vs 33%, p = 0.13) and lobar location of hemorrhages (71% vs 30%, p = 0.15). Two out of 6 patients with ICH who also underwent MRI had remote DWI lesions, of whom one showed MES on TCD.

CONCLUSION

Micro-embolic signals occur in over one-third of patients with ICH. Further research is needed to identify the sources of cerebral microembolism and their relationship with small acute infarcts in ICH.

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.

Triple versus guideline antiplatelet therapy to prevent recurrence after acute ischaemic stroke or transient ischaemic attack: the TARDIS RCT

BACKGROUND

Two antiplatelet agents are better than one for preventing recurrent stroke after acute ischaemic stroke or transient ischaemic attack (TIA). Therefore, intensive treatment with three agents might be better still, providing it does not cause undue bleeding.

OBJECTIVE

To compare the safety and efficacy of intensive therapy with guideline antiplatelet therapy for acute ischaemic stroke and TIA.

DESIGN

International prospective randomised open-label blinded end-point parallel-group superiority clinical trial.

SETTING

Acute hospitals at 106 sites in four countries.

PARTICIPANTS

Patients > 50 years of age with acute non-cardioembolic ischaemic stroke or TIA within 48 hours of ictus (stroke).

INTERVENTIONS

Participants were allocated at random by computer to 1 month of intensive (combined aspirin, clopidogrel and dipyridamole) or guideline (combined aspirin and dipyridamole, or clopidogrel alone) antiplatelet agents, and followed for 90 days.

MAIN OUTCOME MEASURES

The primary outcome was the incidence and severity of any recurrent stroke (ischaemic, haemorrhagic; assessed using the modified Rankin Scale) or TIA within 90 days by blinded telephone follow-up. Analysis using ordinal logistic regression was by intention to treat. Other outcomes included bleeding and its severity, death, myocardial infarction (MI), disability, mood, cognition and quality of life.

RESULTS

The trial was stopped early on the recommendation of the Data Monitoring Committee after recruitment of 3096 participants (intensive, n = 1556; guideline, n = 1540) from 106 hospitals in four countries between April 2009 and March 2016. The incidence and severity of recurrent stroke or TIA did not differ between intensive and guideline therapy in 3070 (99.2%) participants with data [93 vs. 105 stroke/TIA events; adjusted common odds ratio 0.90, 95% confidence interval (CI) 0.67 to 1.20; p = 0.47]. Major (encompassing fatal) bleeding was increased with intensive as compared with guideline therapy [39 vs. 17 participants; adjusted hazard ratio (aHR) 2.23, 95% CI 1.25 to 3.96; p = 0.006]. There were no differences between the treatment groups in all-cause mortality, or the composite of death, stroke, MI and major bleeding (aHR 1.02, 95% CI 0.77 to 1.35; p = 0.88).

LIMITATIONS

Patients and investigators were not blinded to treatment. The comparator group comprised two guideline strategies because of changes in national guidelines during the trial. The trial was stopped early, thereby reducing its statistical power.

CONCLUSIONS

The use of three antiplatelet agents is associated with increased bleeding without any significant reduction in recurrence of stroke or TIA.

FUTURE WORK

The safety and efficacy of dual antiplatelet therapy (combined aspirin and clopidogrel) versus aspirin remains to be defined. Further research is required on identifying individual patient response to antiplatelets, and the relationship between response and the subsequent risks of vascular recurrent events and bleeding complications.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN47823388.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 22, No. 48. See the NIHR Journal Library website for further project information. The Triple Antiplatelets for Reducing Dependency after Ischaemic Stroke (TARDIS) vanguard phase was funded by the British Heart Foundation (grant PG/08/083/25779, from 1 April 2009 to 30 September 2012) and indirect funding was provided by the Stroke Association through its funding of the Stroke Trials Unit, Division of Clinical Neuroscience, University of Nottingham, Nottingham, UK. There was no commercial support for the trial and antiplatelet drugs were sourced locally at each site. The trial was sponsored by the University of Nottingham.

Optimal Antiplatelet Therapy in Moderate to Severe Asymptomatic and Symptomatic Carotid Stenosis: A Comprehensive Review of the Literature

OBJECTIVES

Carotid stenosis patients are at risk of vascular events despite antiplatelet therapy. Data on prescribed antiplatelet regimens have not been comprehensively collated from trials to guide optimal therapy in this population.

METHODS

This review was conducted in line with the current Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Medline, Ovid, Embase, Web of Science, and Google Scholar from 1988 to 2018 were searched using the search terms "carotid stenosis", "asymptomatic", "symptomatic", "antiplatelet", and "anti-platelet" to identify randomised trials in patients with asymptomatic or symptomatic extracranial moderate-severe carotid stenosis on any form of antiplatelet therapy in which vascular events and pre specified composite outcome events were reported.

RESULTS

Twenty-five studies were judged eligible for inclusion. Data from one randomised controlled trial showed no significant difference in benefit with aspirin versus placebo in asymptomatic carotid stenosis, but it is still reasonable to recommend aspirin (81-325 mg daily) for prevention of vascular events in these patients. Low to medium dose aspirin (81-325 mg daily) is superior to higher doses (>650 mg daily) at preventing recurrent vascular events in patients undergoing endarterectomy. Data from endovascular treatment (EVT) trials support peri-procedural treatment of asymptomatic and symptomatic patients with 81-325 mg of aspirin daily. The use of peri-procedural aspirin-clopidogrel in patients undergoing EVT is based on one pilot trial, but appears safe. Short-term aspirin-dipyridamole or aspirin-clopidogrel treatments are equally effective at reducing micro-embolic signals on transcranial Doppler ultrasound in patients with ≥50% symptomatic carotid stenosis. There is insufficient evidence to recommend routine aspirin-clopidogrel combination therapy to reduce the risk of recurrent clinical ischaemic events in patients with symptomatic moderate-severe carotid stenosis.

CONCLUSIONS

This comprehensive review outlines an evidence based approach to antiplatelet therapy in carotid stenosis patients. Future trials should randomise such patients to receive different antiplatelet regimens to assess their efficacy and safety and to optimise peri-procedural and long-term preventive treatment in this patient cohort.

Aspirin plus clopidogrel as secondary prevention after stroke or transient ischemic attack: a systematic review and meta-analysis

BACKGROUND

Antiplatelet agents are the mainstay for secondary prevention of non-cardioembolic stroke. This systematic review examined the safety and efficacy of short-, middle-, and long-term aspirin in combination with clopidogrel as secondary prevention of stroke or transient ischemic attack (TIA) of presumed arterial origin.

METHODS

PubMed, EmBase, and CENTRAL were searched up to May 2014. Randomized controlled trials (RCTs) that compared aspirin plus clopidogrel versus aspirin or clopidogrel as secondary prevention of stroke or TIA of arterial origin were included. The analyses were stratified into short-term (≤3 months), middle-term (>3 months and <1 year), and long-term (≥1 year). Outcomes were compared using risk ratio (RR) and 95% confidence interval (95% CI).

RESULTS

Eight RCTs (20,728 patients) were included in the overall analysis. Compared with aspirin or clopidogrel alone, the complete analysis of all the data indicated that the combination therapy significantly reduced the risk of stroke recurrence (RR, 0.82; 95% CI 0.70-0.96, p = 0.01) and major vascular events (RR, 0.84; 95% CI 0.73-0.96, p < 0.01). But the risk of hemorrhagic stroke (RR, 1.59; 95% CI 1.08-2.33, p = 0.02) and major bleeding (RR, 1.83; 95% CI 1.37-2.45, p < 0.01) was increased. No RCT studied middle-term combination therapy. The analyses were therefore stratified into only two subgroups, short- and long-term treatment. Stratified analysis of short-term treatment showed that relative to monotherapy, the drug combination reduced the risk of stroke recurrence (RR, 0.69; 95% CI 0.59-0.81, p < 0.01) and did not increase the risk of hemorrhagic stroke (RR, 1.23; 95% CI 0.50-3.04, p = 0.65) and major bleeding events (RR, 2.17; 95% CI 0.18-25.71, p = 0.54). Short-term combination therapy was associated with a significantly lower risk of major vascular events (RR, 0.70; 95% CI 0.69 to 0.82, p < 0.01). Stratified analysis of long-term treatment revealed that the combination treatment did not decrease the risk of stroke recurrence (RR, 0.92; 95% CI 0.83-1.03, p = 0.15), but was associated with a significantly higher risk of hemorrhagic stroke (RR, 1.67; 95% CI 1.10-2.56, p = 0.02) and major bleeding events (RR, 1.90; 95% CI 1.46-2.48, p < 0.01). Long-term combination therapy failed to reduce the risk of major vascular events (RR, 0.92; 95% CI 0.84-1.03, p = 0.09).

CONCLUSIONS

Compared with monotherapy, short-term aspirin in combination with clopidogrel is more effective as secondary prevention of stroke or TIA without increasing the risk of hemorrhagic stroke and major bleeding events. Long-term combination therapy does not reduce the risk of stroke recurrence, and is associated with increased major bleeding events. The clinical applicability of the findings of this systematic review, however, needs to be confirmed in future clinical trials.

Variants of COL3A1 are associated with the risk of stroke recurrence and prognosis in the Chinese population: a prospective study

Type III collagen plays an important role in activating platelets, forming thrombus, and maintaining the mechanical properties of arteries. This study aimed to test the hypothesis that genetic variants of COL3A1 (gene encoding type III collagen) contribute to recurrence and prognosis of stroke. We investigated the associations of three variants (rs2138533, rs11887092, and rs1800255) in the COL3A1 gene with stroke recurrence and prognosis in 1,544 patients with three subtypes of stroke: lacunar infarction (n = 442), atherothrombotic infarction (n = 670), and hemorrhage (n = 432). These associations were evaluated by Kaplan-Meier analysis and Cox regression models. Patients were followed up for 4.5 years. The A allele of rs1800255 in the COL3A1 gene coding region was significantly associated with a reduced risk of stroke recurrence in patients with lacunar infarction (adjusted hazard ratio [HR] 0.58, 95 % confidence interval [CI] 0.36-0.93, P = 0.024), but there was an increased risk of all-cause mortality of atherothrombotic patients (adjusted HR 1.43, 95 % CI 1.01-2.00, P = 0.044). The TT genotype of rs2138533 showed a significantly increased risk of death caused by cardiovascular disease or stroke in lacunar infarct patients (adjusted HR 2.98, 95 % CI 1.27-6.98, P = 0.012), but there was a reduced risk of all-cause mortality for patients with intracerebral hemorrhage (adjusted HR 0.34, 95 % CI 0.12-0.93, P = 0.036). The G allele of rs11887092 increased the risk of stroke recurrence in patients with atherothrombotic stroke (adjusted HR 1.59, 95 % CI 1.04-2.44, P = 0.035). In conclusion, variants of COL3A1 might play a vital role in determining the risk of recurrence and prognosis after stroke.

Increased platelet activation in early symptomatic vs. asymptomatic carotid stenosis and relationship with microembolic status: results from the Platelets and Carotid Stenosis Study

BACKGROUND

Cerebral microembolic signals (MES) may predict increased stroke risk in carotid stenosis. However, the relationship between platelet counts or platelet activation status and MES in symptomatic vs. asymptomatic carotid stenosis has not been comprehensively assessed.

SETTING

University teaching hospitals.

METHODS

This prospective, pilot observational study assessed platelet counts and platelet activation status, and the relationship between platelet activation and MES in asymptomatic vs. early (≤ 4 weeks after TIA/stroke) and late phase (≥ 3 months) symptomatic moderate or severe (≥ 50%) carotid stenosis patients. Full blood count measurements were performed, and whole blood flow cytometry was used to quantify platelet surface activation marker expression (CD62P and CD63) and circulating leucocyte-platelet complexes. Bilateral simultaneous transcranial Doppler ultrasound monitoring of the middle cerebral arteries was performed for 1 h to classify patients as MES positive or MES negative.

RESULTS

Data from 31 asymptomatic patients were compared with 46 symptomatic patients in the early phase, and 35 of these patients were followed up to the late phase after symptom onset. The median platelet count (211 vs. 200 × 10(9)  L(-1) ; P = 0.03) and the median percentage of lymphocyte-platelet complexes was higher in early symptomatic than asymptomatic patients (2.8 vs. 2.4%; P = 0.001). The percentage of lymphocyte-platelet complexes was higher in early symptomatic than in asymptomatic patients with ≥ 70% carotid stenosis (P = 0.0005) and symptomatic patients recruited within 7 days of symptom onset (P = 0.028). Complete TCD data were available in 25 asymptomatic, 31 early phase symptomatic and 27 late phase symptomatic patients. Twelve per cent of asymptomatic vs. 32% of early phase symptomatic (P = 0.02) and 19% of late phase symptomatic patients (P = 0.2) were MES positive. Early symptomatic MES-negative patients had a higher percentage of lymphocyte-platelet complexes than asymptomatic MES-negative patients (2.8 vs. 2.3%; P = 0.0085).

DISCUSSION

Recently, symptomatic carotid stenosis patients have had higher platelet counts (potentially reflecting increased platelet production, mobilization or reduced clearance) and platelet activation status than asymptomatic patients. MES were more frequently detected in early symptomatic than asymptomatic patients, but the differences between late symptomatic and asymptomatic groups were not significant. Increased lymphocyte-platelet complex formation in recently symptomatic vs. asymptomatic MES-negative patients indicates enhanced platelet activation in this early symptomatic subgroup. Platelet biomarkers, in combination with TCD, have the potential to aid risk-stratification in asymptomatic and symptomatic carotid stenosis patients.

Circulating microRNAs as novel biomarkers for platelet activation

RATIONALE

MicroRNA (miRNA) biomarkers are attracting considerable interest. Effects of medication, however, have not been investigated thus far.

OBJECTIVE

To analyze changes in plasma miRNAs in response to antiplatelet therapy.

METHODS AND RESULTS

Profiling for 377 miRNAs was performed in platelets, platelet microparticles, platelet-rich plasma, platelet-poor plasma, and serum. Platelet-rich plasma showed markedly higher levels of miRNAs than serum and platelet-poor plasma. Few abundant platelet miRNAs, such as miR-24, miR-197, miR-191, and miR-223, were also increased in serum compared with platelet-poor plasma. In contrast, antiplatelet therapy significantly reduced miRNA levels. Using custom-made quantitative real-time polymerase chain reaction plates, 92 miRNAs were assessed in a dose-escalation study in healthy volunteers at 4 different time points: at baseline without therapy, at 1 week with 10 mg prasugrel, at 2 weeks with 10 mg prasugrel plus 75 mg aspirin, and at 3 weeks with 10 mg prasugrel plus 300 mg aspirin. Findings in healthy volunteers were confirmed by individual TaqMan quantitative real-time polymerase chain reaction assays (n=9). Validation was performed in an independent cohort of patients with symptomatic atherosclerosis (n=33), who received low-dose aspirin at baseline. Plasma levels of platelet miRNAs, such as miR-223, miR-191, and others, that is, miR-126 and miR-150, decreased on further platelet inhibition.

CONCLUSIONS

Our study demonstrated a substantial platelet contribution to the circulating miRNA pool and identified miRNAs responsive to antiplatelet therapy. It also highlights that antiplatelet therapy and preparation of blood samples could be confounding factors in case-control studies relating plasma miRNAs to cardiovascular disease.

Platelet activation, function, and reactivity in atherosclerotic carotid artery stenosis: a systematic review of the literature

An important proportion of transient ischemic attack or ischemic stroke is attributable to moderate or severe (50-99%) atherosclerotic carotid stenosis or occlusion. Platelet biomarkers have the potential to improve our understanding of the pathogenesis of vascular events in this patient population. A detailed systematic review was performed to collate all available data on ex vivo platelet activation and platelet function/reactivity in patients with carotid stenosis. Two hundred thirteen potentially relevant articles were initially identified; 26 manuscripts met criteria for inclusion in this systematic review. There was no consistent evidence of clinically informative data from urinary or soluble blood markers of platelet activation in patients with symptomatic moderate or severe carotid stenosis who might be considered suitable for carotid intervention. Data from flow cytometry studies revealed evidence of excessive platelet activation in patients in the early, sub-acute, or late phases after transient ischemic attack or stroke in association with moderate or severe carotid stenosis and in asymptomatic moderate or severe carotid stenosis compared with controls. Furthermore, pilot data suggest that platelet activation may be increased in recently symptomatic than in asymptomatic severe carotid stenosis. Excessive platelet activation and platelet hyperreactivity may play a role in the pathogenesis of first or subsequent transient ischemic attack or stroke in patients with moderate or severe carotid stenosis. Larger longitudinal studies assessing platelet activation status with flow cytometry and platelet function/reactivity in symptomatic vs. asymptomatic carotid stenosis are warranted to improve our understanding of the mechanisms responsible for transient ischemic attack or stroke.

Dual or mono antiplatelet therapy for patients with acute ischemic stroke or transient ischemic attack: systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND PURPOSE

Antiplatelets are recommended for patients with acute noncardioembolic stroke or transient ischemic attack. We compared the safety and efficacy of dual versus mono antiplatelet therapy in patients with acute ischemic stroke or transient ischemic attack.

METHODS

Completed randomized controlled trials of dual versus mono antiplatelet therapy in patients with acute (≤3 days) ischemic stroke/transient ischemic attack were identified using electronic bibliographic searches. The primary outcome was recurrent stroke (ischemic, hemorrhagic, unknown; fatal, nonfatal). Comparison of binary outcomes between treatment groups was analyzed with random effect models and described using risk ratios (95% CI).

RESULTS

Twelve completed randomized trials involving 3766 patients were included. In comparison with mono antiplatelet therapy, dual therapy (aspirin+dipyridamole and aspirin+clopidogrel) significantly reduced stroke recurrence, dual 58 (3.3%) versus mono 91 (5.0%; risk ratio, 0.67; 95% CI, 0.49-0.93); composite vascular event (stroke, myocardial infarction, vascular death), dual 74 (4.4%) versus mono 106 (6%; risk ratio, 0.75; 95% CI, 0.56-0.99); and the combination of stroke, transient ischemic attack, acute coronary syndrome, and all death, dual 100 (1.7%) versus mono 136 (9.1%; risk ratio, 0.71; 95% CI, 0.56-0.91); dual therapy was also associated with a nonsignificant trend to increase major bleeding, dual 15 (0.9%) versus mono 6 (0.4%; risk ratio, 2.09; 95% CI, 0.86-5.06).

CONCLUSIONS

Dual antiplatelet therapy appears to be safe and effective in reducing stroke recurrence and combined vascular events in patients with acute ischemic stroke or transient ischemic attack as compared with mono therapy. These results need to be tested in prospective studies.

Clopidogrel is not associated with major bleeding complications during peripheral arterial surgery

OBJECTIVES

Persistent variation in practice surrounds preoperative clopidogrel management at the time of vascular surgery. While some surgeons preferentially discontinue clopidogrel citing a perceived risk of perioperative bleeding, others will proceed with surgery in patients taking clopidogrel for an appropriate indication. The purpose of this study was to determine whether preoperative clopidogrel use was associated with significant bleeding complications during peripheral arterial surgery.

METHODS

We reviewed a prospective regional vascular surgery registry recorded by 66 surgeons from 15 centers in New England from 2003 to 2009. Preoperative clopidogrel use within 48 hours of surgery was analyzed among patients undergoing carotid endarterectomy (CEA), lower extremity bypass (LEB), endovascular abdominal aortic aneurysm repair (EVAR), and open abdominal aortic aneurysm repair (oAAA). Ruptured AAAs were excluded. Endpoints included postoperative bleeding requiring reoperation, as well as the incidence and volume of blood transfusion. Statistical analysis was performed using analysis of variance, Fisher exact, χ(2), and Wilcoxon rank-sum tests.

RESULTS

Over the study interval, a total of 10,406 patients underwent surgery, including 5264 CEA, 2883 LEB, 1125 EVAR, and 1134 oAAA repair. Antiplatelet use among all patients varied, with 19% (n = 2010) taking no antiplatelet agents, 69% (n = 7132) taking aspirin (ASA) alone, 2.2% (n = 229) taking clopidogrel alone, and 9.7% (n = 1017) taking both ASA and clopidogrel. Clopidogrel alone or as dual antiplatelet therapy was most frequently used prior to CEA and least frequently prior to oAAA group (CEA 16.1%, LEB 9.0%, EVAR 6.5%, oAAA 5%). Reoperation for bleeding was not significantly different among patients based on antiplatelet regimen (none 1.5%, ASA 1.3%, clopidogrel 0.9%, ASA/clopidogrel 1.5%, P = .74). When analyzed by operation type, no difference in reoperation for bleeding was seen across antiplatelet regimens. There was also no difference in the incidence of transfusion among antiplatelet treatment groups (none 18%, ASA 17%, clopidogrel 0%, ASA/clopidogrel 24%, P = .1) and none when analyzed by individual operation type. Among patients who did require transfusion, there was no significant difference in the mean number of units of packed red blood cells required (none 0.7 units, ASA 0.5 units, clopidogrel 0 units, ASA/clopidogrel 0.6 units, P = .1) or when stratified by operation type.

CONCLUSIONS

Patients undergoing peripheral arterial surgery in whom clopidogrel was continued either alone or as part of dual antiplatelet therapy did not have significant bleeding complications compared with patients taking no antiplatelet therapy or ASA alone at the time of surgery. These data suggest that clopidogrel can safely be continued preoperatively in patients with appropriate indications for its use, such as symptomatic carotid disease or recent drug-eluting coronary stents.