Aspirin responsiveness in acute brain ischaemia: association with stroke severity and clinical outcome

Discovery of 2,3-Dihydro[1,4]dioxino[2,3-g]benzofuran Derivatives as Protease Activated Receptor 4 (PAR4) Antagonists with Potent Antiplatelet Aggregation Activity and Low Bleeding Tendency

Patients with arterial embolic disease have benefited greatly from antiplatelet therapy. However, hemorrhage risk of antiplatelet agents cannot be ignored. Herein, we describe the discovery of 2,3-dihydro[1,4]dioxino[2,3-g]benzofuran compounds as novel PAR4 antagonists. Notably, the isomers 36 and 37 with the chemotype of phenoxyl methylene substituted on the 2,3-dihydro-1,4-dioxine ring exhibited potent in vitro antiplatelet activity (IC50 = 26.13 nM for 36 and 14.26 nM for 37) and significantly improved metabolic stability in human liver microsomes (T1/2 = 97.6 min for 36 and 11.1 min for BMS-986120). 36 also displayed good oral PK profiles (mice: T1/2 = 7.32 h and F = 45.11%). Both of them showed overall potent ex vivo antiplatelet activity at concentrations of 6 and 12 mg/kg, with no impact on the coagulation system and low bleeding liability. Our work will facilitate development of novel PAR4 antagonists as a safer therapeutic option for arterial embolism.

Gut microbiota-derived metabolite trimethylamine-N-oxide and stroke outcome: a systematic review

Introduction

The relationship between baseline trimethylamine N-oxide (TMAO) levels and stroke outcomes remains unclear. Therefore, this systematic review aimed to summarize the existing relevant research.

Methods

We searched for studies on the association between baseline plasma levels of TMAO and stroke outcomes in the PubMed, EMBASE, Web of Science, and Scopus databases from their inception to 12 October 2022. Two researchers independently reviewed the studies for inclusion and extracted the relevant data.

Results

Seven studies were included in the qualitative analysis. Among them, six studies reported the outcome of acute ischemic stroke (AIS) and one study of intracerebral hemorrhage (ICH), respectively. Furthermore, no study reported the outcome of subarachnoid hemorrhage. Among patients with AIS, high baseline TMAO levels were associated with unfavorable functional outcomes or mortality at 3 months, as well as a high hazard ratio of mortality, recurrence, or major adverse cardiac event. Moreover, TMAO levels showed predictive utility for unfavorable functional outcomes or mortality at 3 months. Among patients with ICH, high TMAO levels were associated with unfavorable functional outcomes at 3 months, regardless of whether the TMAO value was considered a continuous or a categorical variable.

Conclusion

Limited evidence indicates that high baseline plasma levels of TMAO may be associated with poor stroke outcomes. Further studies are warranted to confirm the relationship between TMAO and stroke outcomes.

High on-treatment platelet reactivity is associated with poor outcomes after ischemic stroke: A meta-analysis

OBJECTIVES

High on-treatment platelet reactivity (HTPR) determined by platelet function assays is present in certain patients with ischemic stroke or transient ischemic attack (TIA). However, it is unclear whether HTPR is associated with poor clinical outcomes. Our study aimed to investigate the relationship of HTPR with recurrent vascular events in ischemic stroke or TIA.

METHODS

Pubmed (MEDLINE), EMBASE, and Cochrane Library were searched for eligible studies from inception to January 1, 2022. Stata 17.0 software was used to calculate the risk ratio (RR). Subgroup and sensitivity analyses were conducted to assess the source of heterogeneity. A random-effects model was used when heterogeneity was present. Primary endpoint of the meta-analysis was the risk ratio of recurrent vascular events in HTPR Patients. While stroke and TIA, all-cause death, early neurological deterioration, early new ischemic lesions, and stroke severity measured by National Institute of Health Stroke Scale (NIHSS) scores at admission were also pooled.

RESULTS

Thirty articles (7995 patients) were eligible including 28 cohort studies and 2 prospective case-control studies. The prevalence of HTPR varied from 5.9% to 60%. HTPR was associated with an increased risk of recurrent vascular events (RR = 2.94, 95% CI 2.04-4.23), stroke recurrence (RR = 2.05; 95% CI 1.43-2.95), and all-cause mortality (RR = 2.43; 95% CI 1.83-3.22). Subgroup analysis showed that HTPR determined by optical aggregometry, Verify-Now system and 11dh TXB2 is related to a higher risk of recurrent vascular events (RR = 3.53, 95% CI 1.51-9.40; RR = 2.16, 95% CI 1.02-4.56; RR = 3.76, 95% CI 1.51-9.40, respectively). Moreover, patients with HTPR had an increased incidence of early neurological deterioration (RR = 2.75; 95% CI 1.76-4.30) and higher NIHSS scores at admission (Mean difference 0.19, 95% CI 0.01-0.36).

CONCLUSIONS

This meta-analysis demonstrates HTPR is associated with higher risk of recurrent vascular events, early neurological deterioration and increased severity in patients with ischemic stroke and TIA. HTPR measured by platelet function assays may guide the use of antiplatelet agents in ischemic stroke and TIA.

Platelet Function Tests Predicting the Efficacy and Safety of Aspirin Secondary Prevention

OBJECTIVE

To precisely prevent stroke, we evaluated three platelet function tests and their associations with clinical outcomes in ischemic stroke patients.

METHODS

On-treatment platelet reactivity of acute minor stroke patients taking aspirin plus clopidogrel was tested by light transmittance aggregometry (LTA), thromboelastography (TEG) and platelet function analyzer (PFA). Mann-Whitney U tests and receiver operating characteristic (ROC) curve analysis were used to assess their associations with recurrent events and clinical outcome prediction.

RESULTS

127 acute minor stroke patients were stringently selected and followed for 13 months. Eight patients (6.3%) self-reported the recurrence and 13 (10.2%) patients self-reported bleeding. Recurrent patients displayed significantly higher on-treatment platelet reactivity when measured with LTA (p = 0.030) and PFA (p < 0.001). Further ROC analysis demonstrated that LTA and PFA had modest-to-fair ability to predict stroke recurrence (LTA: area under the curve [AUC], 0.765; 95% CI, 0.584-0.945, PFA: AUC, 0.832; 95% CI, 0.658-1.000). However, TEG (measured by the platelet inhibition rate) could not detect the difference between recurrent patients and non-recurrent patients (p = 0.515) and predict recurrent events (AUC, 0.569; 95% CI, 0.368-0.770). None of the tests were associated with bleeding except for PFA (p < 0.001), with AUC of PFA reaching 0.772 (0.726-0.818).

CONCLUSIONS

Of the three tests assessed, the predictive accuracies of PFA and LTA were satisfying for aspirin secondary prevention, while TEG's performance was poor. Only PFA could provide accurate prognostic information for bleeding.

Platelet Function Monitoring Performed after Carotid Stenting during Endovascular Stroke Treatment Predicts Outcome

OBJECTIVES

Many studies showed that platelet reactivity testing can predict ischemic events after carotid stenting or ischemic stroke. The aim of our study was to assess the role of early platelet function monitoring in predicting 90-days functional outcome, stent thrombosis and hemorrhagic transformation in patients with ischemic stroke treated with endovascular procedures requiring emergent extracranial stenting.

MATERIALS AND METHODS

We performed a retrospective study on consecutive patients with acute anterior circulation stroke admitted to our hospital between January 2015 and March 2020, in whom platelet reactivity testing was performed within 10 days from stenting. Patients were divided according to validated cutoffs in acetylsalicylic acid and Clopidogrel responders and not responders. Group comparison and regression analyses were performed to identify differences between groups and outcome predictors.

RESULTS

We included in the final analysis 54 patients. Acetylsalicylic acid resistance was an independent predictor of poor 90 days outcome (OR for modified Rankin scale (mRS) ≤ 2: 0.10 95% CI: 0.02 - 0.69) whereas Clopidogrel resistance was an independent predictor of good outcome (OR for mRS ≤ 2: 7.09 95%CI: 1.33 - 37.72). Acetylsalicylic acid resistance was also associated with increased 90-days mortality (OR: 18.42; 95% CI: 1.67 - 203.14).

CONCLUSION

We found a significant association between resistance to acetylsalicylic acid and poor 90-days functional outcome and between resistance to Clopidogrel and good 90-days functional outcome. If confirmed, our results might improve pharmacological management after acute carotid stenting.

Effects of post-interventional antiplatelet therapy on angiographic vasospasm, delayed cerebral ischemia, and clinical outcome after aneurysmal subarachnoid hemorrhage: a single-center experience

Platelet activation has been postulated to be involved in the pathogenesis of delayed cerebral ischemia (DCI) and cerebral vasospasm (CVS) after aneurysmal subarachnoid hemorrhage (aSAH). The aim of this study was to investigate potentially beneficial effects of antiplatelet therapy (APT) on angiographic CVS, DCI-related infarction and functional outcome in endovascularly treated aSAH patients. Retrospective single-center analysis of aSAH patients treated by endovascular aneurysm obliteration. Based on the post-interventional medical regime, patients were assigned to either an APT group or a control group not receiving APT. A subgroup analysis separately investigated those APT patients with aspirin monotherapy (MAPT) and those receiving dual treatment (aspirin plus clopidogrel, DAPT). Clinical and radiological characteristics were compared between groups. Possible predictors for angiographic CVS, DCI-related infarction, and an unfavorable functional outcome (modified Rankin scale ≥ 3) were analyzed. Of 160 patients, 85 (53%) had received APT (n = 29 MAPT, n = 56 DAPT). APT was independently associated with a lower incidence of an unfavorable functional outcome (OR 0.40 [0.19-0.87], P = 0.021) after 3 months. APT did not reduce the incidence of angiographic CVS or DCI-related infarction. The pattern of angiographic CVS or DCI-related infarction as well as the rate of intracranial hemorrhage did not differ between groups. However, the lesion volume of DCI-related infarctions was significantly reduced in the DAPT subgroup (P = 0.011). Post-interventional APT in endovascularly treated aSAH patients is associated with better functional outcome at 3 months. The beneficial effect of APT might be mediated by reduction of the size of DCI-related infarctions.

Prognostic Value of Plasma Trimethylamine N-Oxide Levels in Patients with Acute Ischemic Stroke

Trimethylamine N-oxide (TMAO) has emerged as a newly identified gut microbiota-dependent metabolite contributing to a variety of diseases, such as diabetes, atherosclerosis, and cardiovascular diseases. The aim of our study was to determine whether a relatively high TMAO level is associated with an increased risk of poor outcome in ischemic stroke patients. From June 2018 to December 2018, we prospectively recruited acute ischemic stroke patients diagnosed within 24 h of symptom onset. The plasma TMAO level was measured at admission for all patients. Functional outcome was evaluated at 3 months after the stroke using the modified Rankin Scale (mRS) and then dichotomized as favorable (mRS 0-2) or unfavorable (mRS 3-6). A multivariate logistic regression analysis was conducted to evaluate the association between TMAO concentration and poor functional outcome and mortality at 3 months. Of the 225 acute ischemic stroke patients included in the analysis, the median TMAO concentration was 3.8 µM (interquartile range, 1.9-4.8 µM). At 3 months after admission, poor functional outcome was observed in 116 patients (51.6%), and 51 patients had died (22.7%). After adjusting for potential confounders, patients with TMAO levels in the highest quartile were more likely to have higher risks of poor functional outcome [compared with the lowest quartile, odds ratio (OR) 3.63; 95% confidence interval (CI) 1.34-9.82; P = 0.011] and mortality (OR 4.27; 95% CI 1.07-17.07; P = 0.040). Our data suggest that a high plasma TMAO level upon admission may predict unfavorable clinical outcomes in acute ischemic stroke patients.

Aspirin resistance predicts unfavorable functional outcome in acute ischemic stroke patients

OBJECTIVE

To investigate the prognostic value of aspirin reaction units (ARU) in a 3-month follow-up study in a cohort of Chinese patients with first-ever ischemic stroke.

METHODS

Prospective single-center survey of acute ischemic stroke patients receiving aspirin therapy. Two hundred and seventy-five Chinese patients with first-ever ischemic stroke who previously received aspirin therapy were enrolled. ARU was measured using the VerifyNow system. A cutoff of 550 ARU was used to determine the presence of aspirin resistance (AR).

RESULTS

Median age at study entry was 67 years (IQR: 59-75) and 142(51.6%) were male. A total of 52 of 275 enrolled patients (18.9%) were AR. Median regression estimated a statistically significant increase in NIHSS score of 0.033 point for every 1-point increase in ARU (95% CI, 0.024 to 0.068; P < 0.001). The unfavorable outcomes distribution across the ARU quartiles ranged between 11.8% (first quartile) to 64.8% (fourth quartile). After adjusting for other established risk factors, in multivariate models comparing the third and fourth quartiles against the first quartile of the ARU, levels of ARU were associated with unfavorable outcome, and the adjusted risk of unfavorable outcome increased by 145% (OR = 2.45 [95% CI 1.46-3.87], P = 0.011) and 317% (4.17[2.76-6.15], P < 0.001), respectively. Similarly, the adjusted risk of mortality increased by 215% (OR = 3.15 [95% CI 1.98-4.73], P = 0.008) and 429% (5.29[4.02-8.17], P < 0.001), respectively.

CONCLUSIONS

The results suggest that AR is a meaningful and independent marker to predict short-term functional outcome in patients with ischemic stroke.

Dose-dependent effect of early antiplatelet therapy in acute ischaemic stroke

Antiplatelet agents are essential in treating patients with acute ischaemic stroke (AIS) to prevent recurrent ischaemic events. The aim of this study was to evaluate the effectiveness of early antiplatelet therapy with different aspirin (ASA) dosages in patients with AIS. This observational study included 454 patients with AIS in whom antiplatelet treatment was initiated. The antiplatelet effect was determined by whole blood aggregometry within 48 hours after antplatelet therapy was initiated. An impedance change exceeding 0 Ω after stimulation with arachidonic acid was defined as ASA low response (ALR) and ≥5 Ω in ADP-stimulated specimen as clopidogrel LR. Of the study group 53.5% patients were treated with 200 mg ASA orally, 27.5% with 500 mg ASA intravenously, 8.6% with 100 mg ASA orally, and 7.7% with 75 mg clopidogrel. A dose-dependent antiplatelet effect of ASA treatment was found: 18.4% of patients with 500 mg ASA intravenously were ALR, in contrast to 32.5% on 200 mg and 35.9% on 100 mg ASA orally. Clopidogrel treatment without a loading dose resulted in a high proportion of LR (45.7%). Using the propensity score method revealed a three times higher risk for ALR for patients treated with ASA 200 mg [odds ratio 2.99 (1.55–5.79)] compared to treatment with ASA 500 mg. In conclusion, initiating antiplatelet therapy in patients with AIS resulted in a dose-dependent insufficient platelet inhibitory effect. Our findings suggest using a loading dose of 500 mg ASA intravenously as this seems to be favourable when a sufficient early platelet inhibitory effect is wanted.

ClinicalTrials.gov Identifier: NCT01273935

Biochemical aspirin resistance is associated with increased stroke severity and infarct volumes in ischemic stroke patients

To explore the correlation of aspirin resistance (AR) with clinical stroke severity and infarct volume using diffusion-weighted imaging (DWI) in 224 Chinese ischemic stroke patients who were taking aspirin before stroke onset. In those patients, the median age was 64 years (IQR, 56-75 years), and males accounting for 54.9%(123)of the total subjects. Fifty of 224 enrolled patients (22.3%; 95% confidence interval (CI), 16.9% to 27.7%) showed AR. In the median regression model, significant increase was estimated in NIHSS score of 0.04 point for every 1-point increase in aspirin reaction units (ARU) (95% CI, 0.02 to 0.06; P<0.001). Diffusion-weighted MRI (DWI)-measured infarct volume were significantly higher in patients with AR as compared with those with AS [13.21 (interquartile ranges [IQR], 8.51-23.88) vs.4.26 (IQR, 1.74-11.62); P<0.001). Furthermore, a statistically significant increase was also measured in NIHSS score of 0.05 point for every 1-point increase in ARU in the median regression model (95% CI, 0.03 to 0.08; P<0.001). The median DWI infarct volume was significantly larger in the highest ARU quartile when compared to that in the low 3 quartiles (P<0.001). In conclusion, stroke patients with AR indicated higher risk of severe strokes and large infarcts compared to patients in the aspirin-sensitive group.

Antiplatelet drug resistance is associated with early neurological deterioration in acute minor ischemic stroke in the Chinese population

To evaluate the prevalence and risk factors of antiplatelet drug resistance and its association with early neurological deterioration (END) and recurrent ischemic stroke (RIS) in patients with acute minor stroke. Antiplatelet drug resistance was assessed by platelet aggregation assay in 426 patients with minor stroke who were receiving combined treatment of aspirin and clopidogrel. All patients were followed up for 90 days. The primary endpoint of the study was END within 10 days after admission. The secondary endpoints included RIS, myocardial infarction and death during 90 days of treatment. The safety endpoints were intracerebral or extracranial hemorrhagic events. Cox proportional hazard regression analysis was performed to determine the risk factors for the primary endpoint and secondary endpoints. Among the 426 patients, 24.4 % exhibited aspirin resistance, 35.9 % exhibited clopidogrel resistance, and 19.2 % displayed concomitant aspirin and clopidogrel resistance. In multivariate analysis, diabetes mellitus and high level of low density lipoprotein-cholesterol were independent risk factors for aspirin resistance, while diabetes mellitus was the only independent risk factor for clopidogrel resistance. END was observed in 93 (21.8 %) patients. Diabetes mellitus, high fasting blood glucose level, and concomitant aspirin and clopidogrel resistance were independent risk factors for END. RIS was observed in 40 (9.4 %) patients. Diabetes mellitus, hypertension, and concomitant aspirin and clopidogrel resistance were independent risk factors for RIS. Antiplatelet drug resistance is common in acute minor ischemic stroke patients and is associated with END and RIS after acute minor ischemic stroke in the Chinese population.

CLINICAL TRIAL REGISTRATION INFORMATION

http://www.chictr.org/ . Unique Identifier: ChiCTR-OCH-14004724.

Aspirin resistance is associated with increased stroke severity and infarct volume

OBJECTIVES

To investigate whether aspirin resistance is associated with initial stroke severity and infarct volume, using diffusion-weighted imaging (DWI) in patients with acute ischemic stroke that occurred while taking aspirin.

METHODS

We studied a total of 310 patients who were admitted within 48 hours of acute ischemic stroke onset. All patients had been taking aspirin for at least 7 days before stroke onset. Aspirin resistance, defined as high residual platelet reactivity (HRPR) on aspirin treatment, was measured using the VerifyNow assay and defined as an aspirin reaction unit ≥550. Initial stroke severity was assessed using the NIH Stroke Scale (NIHSS) score. Infarct volume was measured using DWI.

RESULTS

HRPR occurred in 86 patients (27.7%). The initial NIHSS score (median [interquartile range]) was higher in patients with HRPR than in the non-HRPR group (6 [3-15] vs 3 [1-8], p < 0.001). DWI infarct volumes were also larger in the HRPR group compared to the non-HRPR group (5.4 [0.8-43.2] vs 1.7 [0.4-10.3], p = 0.002). A multivariable median regression analysis showed that HRPR was significantly associated with an increase of 2.1 points on the NIHSS (95% confidence interval 0.8-4.0, p < 0.001) and an increase of 2.3 cm(3) in DWI infarct volume (95% confidence interval 0.4-3.9, p < 0.001).

CONCLUSIONS

Aspirin resistance is associated with an increased risk of severe stroke and large infarct volume in patients taking aspirin before stroke onset.

The prognostic utility of tests of platelet function for the detection of 'aspirin resistance' in patients with established cardiovascular or cerebrovascular disease: a systematic review and economic evaluation

BACKGROUND

The use of aspirin is well established for secondary prevention of cardiovascular disease. However, a proportion of patients suffer repeat cardiovascular events despite being prescribed aspirin treatment. It is uncertain whether or not this is due to an inherent inability of aspirin to sufficiently modify platelet activity. This report aims to investigate whether or not insufficient platelet function inhibition by aspirin ('aspirin resistance'), as defined using platelet function tests (PFTs), is linked to the occurrence of adverse clinical outcomes, and further, whether or not patients at risk of future adverse clinical events can be identified through PFTs.

OBJECTIVES

To review systematically the clinical effectiveness and cost-effectiveness evidence regarding the association between PFT designation of 'aspirin resistance' and the risk of adverse clinical outcome(s) in patients prescribed aspirin therapy. To undertake exploratory model-based cost-effectiveness analysis on the use of PFTs.

DATA SOURCES

Bibliographic databases (e.g. MEDLINE from inception and EMBASE from 1980), conference proceedings and ongoing trial registries up to April 2012.

METHODS

Standard systematic review methods were used for identifying clinical and cost studies. A risk-of-bias assessment tool was adapted from checklists for prognostic and diagnostic studies. (Un)adjusted odds and hazard ratios for the association between 'aspirin resistance', for different PFTs, and clinical outcomes are presented; however, heterogeneity between studies precluded pooling of results. A speculative economic model of a PFT and change of therapy strategy was developed.

RESULTS

One hundred and eight relevant studies using a variety of PFTs, 58 in patients on aspirin monotherapy, were analysed in detail. Results indicated that some PFTs may have some prognostic utility, i.e. a trend for more clinical events to be associated with groups classified as 'aspirin resistant'. Methodological and clinical heterogeneity prevented a quantitative summary of prognostic effect. Study-level effect sizes were generally small and absolute outcome risk was not substantially different between 'aspirin resistant' and 'aspirin sensitive' designations. No studies on the cost-effectiveness of PFTs for 'aspirin resistance' were identified. Based on assumptions of PFTs being able to accurately identify patients at high risk of clinical events and such patients benefiting from treatment modification, the economic model found that a test-treat strategy was likely to be cost-effective. However, neither assumption is currently evidence based.

LIMITATIONS

Poor or incomplete reporting of studies suggests a potentially large volume of inaccessible data. Analyses were confined to studies on patients prescribed aspirin as sole antiplatelet therapy at the time of PFT. Clinical and methodological heterogeneity across studies precluded meta-analysis. Given the lack of robust data the economic modelling was speculative.

CONCLUSIONS

Although evidence indicates that some PFTs may have some prognostic value, methodological and clinical heterogeneity between studies and different approaches to analyses create confusion and inconsistency in prognostic results, and prevented a quantitative summary of their prognostic effect. Protocol-driven and adequately powered primary studies are needed, using standardised methods of measurements to evaluate the prognostic ability of each test in the same population(s), and ideally presenting individual patient data. For any PFT to inform individual risk prediction, it will likely need to be considered in combination with other prognostic factors, within a prognostic model.

STUDY REGISTRATION

This study is registered as PROSPERO 2012:CRD42012002151.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

The Interplay between Stroke Severity, Antiplatelet Use, and Aspirin Resistance in Ischemic Stroke

BACKGROUND

The issue of whether prior antiplatelet use favorably affects stroke severity is currently unresolved. In this study, we evaluated the effect of antiplatelet use on clinical stroke severity and ischemic lesion volume, and assessed the confounding effect of laboratory-defined aspirin resistance on this relationship.

METHODS

Admission National Institutes of Health Stroke Scale (NIHSS) score, ischemic lesion volumes on diffusion-weighted imaging (DWI), and in vitro aspirin resistance, in addition to other pertinent stroke features, were determined in a series of ischemic stroke patients. Univariate and multivariate analyses were performed to compare clinical and imaging markers of stroke severity among patients with and without prior antiplatelet use, taking into consideration the presence or absence of aspirin resistance.

RESULTS

Antiplatelet users experienced more severe strokes, per NIHSS score, in comparison to antiplatelet-naive patients (P = .007). No significant difference was observed with respect to admission DWI lesion volume. When analyses were repeated after adjustment for stroke subtype and other confounders, no association was observed between antiplatelet use and stroke severity. On the other hand, NIHSS scores were significantly higher in aspirin-unresponsive patients than in both aspirin responders (P = .049) and aspirin nonusers (P = .005).

CONCLUSION

We were unable to demonstrate a substantial positive influence of prestroke antiplatelet usage on stroke severity. Although the presence of more severe strokes among patients with laboratory resistance suggests a protective influence of aspirin sensitivity on stroke severity, the hypothesis could not be validated as no difference was observed among aspirin-naive and aspirin-sensitive patients with respect to admission NIHSS score or DWI lesion volume.

Antiplatelet strategies for secondary prevention of stroke and TIA

Stroke is a major public health issue, and stroke recurrence accounts for a quarter of all events. Antiplatelet therapy has been extensively studied for secondary stroke prevention and is established as effective in this high-risk population. Several agents have been evaluated in this setting, both in isolation and combination. The most widely used antiplatelet medications are aspirin, clopidogrel, and aspirin plus extended-release dipyridamole. However, new agents and combinations continue to be evaluated. A detailed review of the evidence supporting various antiplatelet regimens for secondary stroke prevention is outlined with special focus on recent developments that may impact clinical management of patients with stroke or TIA.

Aspirin resistance in the acute stages of acute ischemic stroke is associated with the development of new ischemic lesions

BACKGROUND

Aspirin is a primary antiplatelet agent for the secondary prevention of ischemic stroke. However, if aspirin fails to inhibit platelet function, as is expected in acute ischemic stroke (AIS), it may increase the rate of early clinical events. Therefore, we sought to determine whether aspirin resistance in the acute stage was associated with early radiological events, including new ischemic lesions (NILs).

METHODS

This study was a single-center, prospective, observational study conducted between April 2012 and May 2013. Aspirin 300 mg was initially administered followed by maintenance doses of 100 mg daily. The acute aspirin reaction unit (aARU) was consistently measured after 3 hours of aspirin loading. An aARU value ≥550 IU was defined as biological aspirin resistance (BAR). NILs on follow-up diffusion-weighted imaging (DWI) were defined as lesions separate from index lesions, which were not detected on the initial DWI.

RESULTS

A total of 367 patients were analyzed in this study. BAR in aARU was detected in 60 patients (16.3%). On follow-up DWI, 81 patients (22.1%) had NILs, which were frequently in the same territory as the index lesions (79%), pial infarcts (61.7%), and located within the cortex (59.3%). BAR was independently associated with NILs on follow-up DWI (adjusted OR 2.00, 95% CIs 1.01-3.96; p = 0.047).

CONCLUSION

In conclusion, BAR in aARU could be associated with NILs on follow-up DWI in AIS. Therefore, a further prospective study with a longer follow-up period is necessary to evaluate the clinical implications of aARU in AIS.

Low-molecular-weight heparin or dual antiplatelet therapy is more effective than aspirin alone in preventing early neurological deterioration and improving the 6-month outcome in ischemic stroke patients

BACKGROUND AND PURPOSE

Dual antiplatelet therapy (DAT) with clopidogrel and aspirin has been shown to confer greater protection against early neurological deterioration (END) and early recurrent ischemic stroke (ERIS) than aspirin alone in patients who have experienced an acute ischemic stroke. However, few studies have compared the effects of anticoagulation therapy with low-molecular-weight heparin (LMWH), DAT, and aspirin.

METHODS

Patients with acute ischemic stroke (n=1,467) were randomized to therapy groups receiving aspirin (200 mg daily for 14 days, followed by 100 mg daily for 6 months), DAT (200 mg of aspirin and 75 mg of clopidogrel daily for 14 days, then 100 mg of aspirin daily for 6 months), or LMWH (4,000 antifactor Xa IU of enoxaparin in 0.4 mL subcutaneously twice daily for 14 days, followed by 100 mg of aspirin daily for 6 months). The effects of these treatment strategies on the incidence of END, ERIS, and deep-vein thrombosis (DVT) were observed for 10-14 days after treatment, and their impacts on a good outcome were evaluated at 6 months.

RESULTS

The DAT and LMWH were associated with a more significant reduction of END and ERIS within 14 days compared with aspirin-alone therapy. In addition, LMWH was associated with a significantly lower incidence of DVT within 14 days. At 6 months, DAT or LMWH improved the outcome among patients aged >70 years and those with symptomatic stenosis in the posterior circulation or basilar artery compared with aspirin.

CONCLUSIONS

LMWH or DAT may be more effective than aspirin alone for reducing the incidence of END and ERIS within 14 days, and is associated with improved outcomes in elderly patients and those with stenosis in the posterior circulation or basilar artery at 6 months poststroke.

Clopidogrel Plus Aspirin Prevents Early Neurologic Deterioration and Improves 6-Month Outcome in Patients With Acute Large Artery Atherosclerosis Stroke

Aims:

To evaluate the effects of treatments with clopidogrel plus aspirin (dual therapy) on early neurological deterioration (END) and outcomes at 6 months in patients with acute large artery atherosclerosis (LAA) stroke.

Methods:

A total of 574 patients with LAA stroke were randomly assigned to receive either dual therapy or aspirin alone (monotherapy). The primary outcome was END. Secondary outcomes included recurrent ischemic stroke (RIS) and outcomes at 6 months.

Results:

The prevalence of END and RIS was lower in patients on dual therapy than in those on monotherapy during the 30 days. At 6 months, dual therapy improved outcomes among older patients and those with symptomatic stenosis in the posterior circulation and basilar artery.

Conclusion:

Clopidogrel plus aspirin is superior to aspirin alone for reducing END and RIS within 30 days and improves outcomes in certain subgroups at 6 months.

A comparative study of dual versus monoantiplatelet therapy in patients with acute large-artery atherosclerosis stroke

BACKGROUND

Antiplatelet drugs are recommended for patients with acute noncardioembolic stroke. However, few randomized clinical trials have investigated the safety and efficacy of dual antiplatelet therapy for these patients. The aim of this study was to evaluate the effects of treatment with clopidogrel and aspirin (combination therapy) and aspirin alone (monotherapy) on neurologic deterioration, platelet activation, and other short-term outcomes in patients with acute large-artery atherosclerosis stroke.

MATERIALS AND METHODS

Altogether 574 patients with acute (≤2 days) large-artery atherosclerosis stroke were randomly assigned to receive either combined clopidogrel and aspirin or aspirin alone. Platelet aggregation and platelet-leukocyte aggregation studies were performed at days 1 and 30. Primary outcomes including recurrent ischemic stroke, neurologic deterioration, periphery vascular events, and myocardial infarction were monitored. Safety endpoints were hemorrhagic episodes and death.

RESULTS

The prevalence of neurologic deterioration and recurrent ischemic stroke were lower in patients in the combination therapy group than in those of the monotherapy group (3.52% versus 9.78% and 1.76% versus 6.29%, respectively). At day 30 of treatment, the platelet aggregations and platelet-leukocyte aggregates were lower in patients who were treated with clopidogrel and aspirin than in patients given aspirin alone (P < .001).

CONCLUSIONS

For patients with acute large-artery atherosclerosis stroke, treatment with clopidogrel and aspirin for 1 month provided significantly greater inhibition of platelet activity than aspirin alone. Thus, dual therapy can be safer and more effective in reducing ischemic stroke recurrence and neurologic deterioration.

The role of anticoagulants, antiplatelet agents, and their reversal strategies in the management of intracerebral hemorrhage

New anticoagulant and antiplatelet medications have been approved and are prescribed with increased frequency. Intracranial hemorrhage is associated with the use of these medications. Therefore, neurosurgeons need to be aware of these new medications, how they are different from their predecessors, and the strategies for the urgent reversal of their effects. Utilization of intraluminal stents by endovascular neurosurgeons has resulted in the need to have a thorough understanding of antiplatelet agents. Increased use of dabigatran, rivaroxaban, and apixaban as oral anticoagulants for the treatment of atrial fibrillation and acute deep venous thrombosis has increased despite the lack of known antidotes to these medications.

Clinical outcomes using a platelet function-guided approach for secondary prevention in patients with ischemic stroke or transient ischemic attack

BACKGROUND AND PURPOSE

Antiplatelet therapy nonresponse is associated with worse clinical outcomes. We studied the clinical outcomes associated with platelet function-guided modifications in antiplatelet therapy in patients with ischemic stroke or transient ischemic attack.

METHODS

From January 2005 to August 2007, 324 patients with ischemic stroke underwent platelet function testing using platelet aggregometry. Aspirin nonresponse was defined as a mean platelet aggregation ≥20% with 0.5 mg/mL arachidonic acid and/or ≥70% with 5 μmol/L adenosine diphosphate. Clopidogrel nonresponse was defined as a mean platelet aggregation ≥40% with 5 μmol/L adenosine diphosphate. A modification was any increase in antiplatelet therapy occurring after testing. Clinical outcomes were compared between patients with and without platelet function-guided antiplatelet therapy modifications using univariate and propensity score-adjusted analyses.

RESULTS

In patients with ischemic stroke or transient ischemic attack, 43% (n=128) and 35% (n=54) were nonresponders to aspirin and clopidogrel, respectively. After platelet function testing, antiplatelet therapy was increased in 23% of patients (n=73). After propensity score matching (n=61 in each group), antiplatelet therapy modification was associated with significantly increased rates of death, ischemic events, or bleeding (hazard ratio, 2.24; 95% CI, 1.12-4.47; P=0.02) compared with no modification in antiplatelet therapy and a trend toward increased bleeding (hazard ratio, 3.56; 95% CI, 0.98-12.95; P=0.05). No differences in ischemic events were observed.

CONCLUSIONS

Platelet function-guided modification in antiplatelet therapy after an ischemic stroke or transient ischemic attack was associated with significantly higher rates of adverse clinical outcomes.

ADP-induced platelet aggregation in acute ischemic stroke patients on aspirin therapy

BACKGROUND AND PURPOSE

Aspirin is an important therapeutic regimen to prevent the recurrent ischemic events or death after acute ischemic stroke. In this study, we evaluated the relationship between the extent of adenosine diphosphate (ADP)-induced platelet aggregation and outcome in acute ischemic stroke patients on aspirin therapy.

METHODS

We selected 107 acute ischemic stroke patients who had been prescribed aspirin and evaluated platelet function test by using optic platelet aggregometer test after 5 days of taking it and investigated the prognosis 90 days after ischemic events. Kaplan-Meyer curve was used for survival analysis.

RESULTS

After stratification of the subjected patients by tertiles of ADP-induced platelet aggregation, the events rates were 7.4%, 9.3% and 30.8% (P = 0.023). In multiple logistic regression analysis, old age over 70 years (OR, 13.7; 95% CI, 2.14-88.07; P = 0.001) and the increased ADP-induced platelet aggregation had independent significance to the risk of primary end-points after acute ischemic stroke (OR, 1.1; 95% CI 1.01 to 1.20; P = 0.026).

CONCLUSIONS

This study showed that the increased ADP-induced platelet aggregation under using aspirin is associated with poor outcome after acute ischemic stroke.

Monitoring oral antiplatelet therapy: is it justified?

Platelets play a key role in the initial formation and progression of intravascular thrombus. During coronary and peripheral vascular interventions, antiplatelet therapy is used to impair platelet reactivity in order to minimize adverse ischemic events. Chronic antiplatelet therapy is also administered to decrease the long term risk of major adverse cardiovascular events in patients with high atherothrombotic burden. However, due to a heterogeneous response to antiplatelet agents, a substantial number of patients with cardiovascular disease remain at risk despite adherence to therapy. Since the availability of point-of-care rapid platelet function assays, quick and reproducible evaluation of platelet function after the administration of aspirin, thienopyridines, and glycoprotein IIb/IIIa inhibitors is possible. Various definitions of suboptimal platelet inhibition with oral antiplatelet therapy and associated risk factors are presented here. An algorithm to guide optimal antiplatelet therapy based on rapid platelet function testing during cardiovascular interventions is also presented.