Effect of combined aspirin and extended-release dipyridamole versus clopidogrel on functional outcome and recurrence in acute, mild ischemic stroke: PRoFESS subgroup analysis

Dual versus mono antiplatelet therapy in mild‐to‐moderate stroke during hospitalization

Objective

Subsequent vascular events are common after acute ischemic stroke during hospitalization. This study aimed to analyze the effectiveness of combination therapy with clopidogrel and aspirin among mild‐to‐moderate ischemic stroke patients treated within 72 h on the basis of a high‐intensity dose of statins.

Methods

In a retrospective and multicenter cohort study, acute (within 72 h of onset) mild‐to‐moderate stroke patients were divided into aspirin and clopidogrel‐aspirin groups on the basis of a high‐intensity dose of statin therapy. The primary outcome was compound vascular events during hospitalization. Cox's proportional hazards model was used to assess differences, with the study center as a random effect.

Results

Among the 506 patients meeting the eligibility criteria, all subjects received a high‐intensity dose of statins, including 20 mg rosuvastatin or 40 mg atorvastatin while in the hospital. In an unadjusted analysis, compound vascular events occurred in 7.2% of patients in the clopidogrel‐aspirin group compared with 13.7% of those in the aspirin group (p = 0.022). In a Cox proportional hazards regression analysis, clopidogrel‐aspirin was associated with a lower risk of compound vascular events (hazard ratio [95% CI], 0.47 [0.25–0.87]; p = 0.017) and ischemic vascular events (p = 0.008). Moderate and severe hemorrhage occurred in four patients (1.07%) in the clopidogrel‐aspirin group and three patients (2.30%) in the aspirin group (p = 0.626).

Interpretation

In this study based on high‐intensity statin therapy, clopidogrel‐aspirin reduced the risk of compound vascular events and did not increase the risk of hemorrhage during patients' hospitalization after mild‐to‐moderate ischemic stroke within 72 h.

Efficacy and Safety of Using Dual Versus Monotherapy Antiplatelet Agents in Secondary Stroke Prevention: Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials

BACKGROUND

Dual antiplatelet treatment (DAPT) with aspirin plus clopidogrel for a limited time is recommended after minor noncardioembolic stroke.

METHODS

We performed a meta-analysis of all major studies that compared the efficacy and safety of DAPT versus monotherapy for the secondary prevention of recurrent stroke or transient ischemic attack. The primary outcomes were stroke and the composite of stroke, transient ischemic attack, acute coronary syndrome, and death from any cause. The safety outcome was major hemorrhage. Relative risk (RR) and 95% CIs were calculated. Heterogeneity was assessed by I² and Cochrane Q statistics.

RESULTS

The analysis included 27 358 patients, the quality of evidence was moderate to low, and the heterogeneity for all the comparisons was low (I²≤25%). Compared with monotherapy, DAPT reduced the risk of recurrent stroke (RR, 0.71 [95% CI, 0.63-0.81]) and composite outcome (RR, 0.76 [95% CI, 0.69-0.83]) but increased the risk of major bleeding (RR, 2.17 [95% CI, 1.45-3.25]). In the subgroup analysis, ≤30 days of DAPT increased the risk of hemorrhage relative to monotherapy (RR, 1.94 [95% CI, 1.08-3.52]). In the sensitivity analysis, the risk for hemorrhage with ≤30 days of DAPT after excluding the combination of aspirin plus ticagrelor was comparable to monotherapy (RR, 1.42 [95% CI, 0.77-2.60]). However, the risk for stroke recurrence and composite outcomes in the subgroup and sensitivity analyses remain decreased compared with monotherapy.

CONCLUSIONS

DAPT decreases the risk of recurrent stroke and composite events compared with monotherapy. DAPT increases the risk of major hemorrhage, except if the treatment is limited to 30 days and does not include the combination of aspirin plus ticagrelor.

Evolution of Clinical Thinking and Practice Regarding Aspirin: What Has Changed and Why?

Aspirin (ASA) is the original antiplatelet agent. Its routine use, long unquestioned for both primary and secondary prevention in cardiovascular disease, is under increasing scrutiny as the risk:benefit balance for ASA becomes less clear and other disease- and risk-modifying approaches are validated. It can be viewed as a significant advance in evidence-based medicine that the use of an inexpensive, readily available, long-validated therapy is being questioned in large, rigorous trials. In this overview we present the important questions surrounding a more informed approach to ASA therapy: duration of therapy, assessment of net clinical benefit, and timing of start and stop strategies. We also consider potential explanations for "breakthrough" thrombosis when patients are on ASA therapy. Other manuscripts in this Supplement address the specifics of primary prevention, secondary prevention, triple oral antithrombotic therapy, and the future of ASA in cardiovascular medicine.

Efficacy of aspirin, clopidogrel, and ticlopidine in stroke prevention: A population-based case-cohort study in Taiwan

Background

In real-world practice settings, there is insufficient evidence on the efficacy of antiplatelet drugs, including clopidogrel, aspirin, and ticlopidine, in stroke prevention.

Purpose

To compare the efficacies between aspirin and clopidogrel and aspirin and ticlopidine in stroke prevention.

Methods

This population-based case-cohort study utilized the data obtained from a randomized sample of one million subjects in the Taiwan National Health Insurance Research Database. Patients who were hospitalized owing to the primary diagnosis of ischemic stroke from January 1, 2000 to December 31, 2010 and treated with aspirin, ticlopidine, or clopidogrel were included in the study. Propensity score matching with a 1:4 ratio was performed to compare aspirin with ticlopidine and clopidogrel. The criteria for inclusion were the use of one of the three antiplatelet drugs for more than 14 days within the first month after the stroke and then continued use of the antiplatelet drugs until the study endpoint of recurrent stroke.

Results

During the 3-year follow-up period, the recurrent stroke rates were 1.62% (42/2585), 1.48% (3/203), and 2.55% (8/314) in the aspirin, ticlopidine, and clopidogrel groups, respectively. Compared with the patients treated with aspirin, those treated with clopidogrel and ticlopidine showed competing risk-adjusted hazard ratios of recurrent stroke of 2.27 (1.02–5.07) and 0.62 (0.08–4.86), respectively.

Conclusion

Compared with the patients treated with aspirin, those treated with clopidogrel were at a higher risk of recurrent stroke. For stroke prevention, aspirin was superior to clopidogrel whereas ticlopidine was not inferior to aspirin.

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.

Dual versus mono antiplatelet therapy for acute non- cardio embolic ischemic stroke or transient ischemic attack, an efficacy and safety analysis - updated meta-analysis

BACKGROUND

New evidence on the efficacy and safety of dual antiplatelet therapy for secondary stroke prevention have been realized in the recent years. An updated meta analysis was done to determine the effect of the various dual antiplatelets vs aspirin alone on recurrence rate of ischemic stroke, cardiovascular morbidity and mortality, and its safety profile as reported through major bleeding.

METHODS

PubMed, Cochrane and Science Direct data bases were utilized, RCTs evaluating dual antiplatelet vs mono antiplatelet therapy for acute ischemic stroke or transient ischemic attack within < 72 h from ictus were searched up to July 2019. Risk ratio at 95% confidence intervals were calculated to evaluate stroke recurrence, cardiac events and mortality, and major bleeding.

RESULTS

Sixteen randomized controlled trials with a population of 28, 032 patients were pooled into a meta-analysis. Dual antiplatelet therapy was significantly superior over mono antiplatelet therapy in the reduction of stroke (RR 0.75, 95% CI:0.68-0.83, p value< 0.00001) and composite events namely cardiovascular morbidity and mortality (0.73 95% CI: 0.65-0.82, p value < 0.00001), while bleeding events were noted to be not significant (1.22 95% CI: 0.87-1.70, p value = 0.25).

CONCLUSION

In acute non-cardioembolic ischemic strokes or those who have suffered a transient ischemic attack, dual antiplatelet therapy was associated with efficacy in stroke recurrence and composite cardiac events, with a non-significant risk of major bleeding.

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.

Secondary Stroke Prophylaxis with Clopidogrel Produces Sufficient Antiplatelet Response

BACKGROUND

Antiplatelet therapy is a cornerstone prevention strategy for secondary ischemic stroke (IS) and transient ischemic attack (TIA). Yet, a proportion of patients who receive antiplatelet therapy experience recurrent ischemic cerebrovascular events. A recent meta-analysis found an increased risk of recurrent stroke in clopidogrel- or aspirin-treated patients with ischemic stroke who had high on-treatment platelet reactivity (HTPR). Few studies have focused specifically on clopidogrel HTPR. Therefore, the aim of this study was to examine the relationship between clopidogrel HTPR and recurrent ischemic events in a population of Danish patients with IS.

METHODS

We performed a prospective observational study to evaluate the relationship between HTPR defined as platelet reaction units >208 and a composite primary endpoint of recurrent stroke, TIA, acute myocardial infarction (AMI), or vascular death over a 2-year follow-up period.

RESULTS

A total of 142 patients were included in the final statistical analysis, but only 3 patients (2.1%) demonstrated clopidogrel HTPR. The median time of on-treatment platelet testing was 75 days. Recurrent IS, TIA, AMI, or vascular death occurred in 14 patients (10%). Of these, 1 new ischemic event (AMI) occurred in a HTPR patient. There was no difference in the frequency of new ischemic events between the HTPR and non-HTPR groups (P = .27); moreover, the number of patients with HTPR was too small for statistical analysis.

CONCLUSIONS

Clopidogrel HTPR does not seem to be a major contributor to recurrent ischemic events in Danish ischemic stroke patients.

Dual versus mono antiplatelet therapy for acute non-cardioembolic ischaemic stroke or transient ischaemic attack: a systematic review and meta-analysis

Objective

Recent years have seen new evidence on the efficacy and safety of dual antiplatelet therapy for secondary stroke prevention. We updated a meta-analysis of randomised controlled trials evaluating dual antiplatelet versus monotherapy for patients with acute non-cardioembolic ischaemic stroke (IS) or transient ischaemic attack (TIA).

Methods

We searched PubMed and identified randomised controlled trials evaluating dual antiplatelet versus monotherapy for acute non-cardioembolic IS or TIA within 3 days of ictus up to May 2018. Risk ratio (RR) with 95% CI were calculated using random effects models. Clinical endpoints included stroke recurrence, composite vascular events and major bleeding.

Results

18 randomised controlled trials including 15 515 patients were pooled in the meta-analysis. When compared with monotherapy among patients with acute IS or TIA, dual antiplatelet therapy reduced the risk of stroke recurrence (RR 0.69; 95% CI 0.61 to 0.78; p<0.001) and composite vascular events (RR 0.72; 95% CI 0.64 to 0.80; p<0.001). Dual therapy was associated with a significant increase in the risk of major bleeding (RR 1.77; 95% CI 1.09 to 2.87; p=0.02) when all trial data were combined. However, when all previous trials before the completion of the POINT trial were analysed, dual antiplatelet versus monotherapy was not associated with a significant increase in the risk of major bleeding (RR 1.46; 95% CI 0.77 to 2.75; p=0.25).

Conclusions

Among patients with acute non-cardioembolic IS or TIA within 3 days of ictus, dual antiplatelet therapy was associated with a reduction in stroke recurrence, and composite vascular events, when compared with monotherapy. However, a significant increase in the risk of major bleeding was observed.

Targeting von Willebrand Factor in Ischaemic Stroke: Focus on Clinical Evidence

Despite great efforts in stroke research, disability and recurrence rates in ischaemic stroke remain unacceptably high. To address this issue, one potential target for novel therapeutics is the glycoprotein von Willebrand factor (vWF), which increases in thrombogenicity especially under high shear rates as it bridges between vascular sub-endothelial collagen and platelets. The rationale for vWF as a potential target in stroke comes from four bodies of evidence. (1) Animal models which recapitulate the pathogenesis of stroke and validate the concept of targeting vWF for stroke prevention and the use of the vWF cleavage enzyme ADAMTS13 in acute stroke treatment. (2) Extensive epidemiologic data establishing the prognostic role of vWF in the clinical setting showing that high vWF levels are associated with an increased risk of first stroke, stroke recurrence or stroke-associated mortality. As such, vWF levels may be a suitable marker for further risk stratification to potentially fine-tune current risk prediction models which are mainly based on clinical and imaging data. (3) Genetic studies showing an association between vWF levels and stroke risk on genomic levels. Finally, (4) studies of patients with primary disorders of excess or deficiency of function in the vWF axis (e.g. thrombotic thrombocytopenic purpura and von Willebrand disease, respectively) which demonstrate the crucial role of vWF in atherothrombosis. Therapeutic inhibition of VWF by novel agents appears particularly promising for secondary prevention of stroke recurrence in specific sub-groups of patients such as those suffering from large artery atherosclerosis, as designated according to the TOAST classification.

The Efficacy and Safety of 3 Types of Interventions for Stroke Prevention in Patients With Cardiovascular and Cerebrovascular Diseases: A Network Meta-analysis

PURPOSE

The goal of this study was to compare the relative efficacy and safety of different types of interventions for stroke prevention in patients with cardiovascular and cerebrovascular diseases.

METHODS

This network meta-analysis (NMA) was conducted with a random effects model of Bayesian framework using Stata version 12.0. Odds ratios (ORs) and their credible intervals (CrIs) were applied for the efficacy and safety evaluation of various medical interventions, including aspirin, dipyridamole, ticlopidine, warfarin, and apixaban. In addition, the ranking of probability of every clinical outcome was estimated by comparing the surface under the cumulative ranking curve.

FINDINGS

Compared with dabigatran, both edoxaban and aspirin + warfarin exhibited a higher rate of all-cause stroke (OR, 2.84 [95% CrI, 1.17-6.97]; OR, 3.42 [95% CrI, 1.20-9.84]). With respect to intracranial hemorrhage, aspirin + clopidogrel yielded worse outcomes than 7 treatments, including placebo, apixaban, aspirin, aspirin + dipyridamole, cilostazol, clopidogrel, and dabigatran (OR, 2.21 [95% CrI, 1.45-3.40]; OR, 2.11 [95% CrI, 1.05-4.17]; OR, 1.53 [95% CrI, 1.11-2.15]; OR, 1.78 [95% CrI, 1.01-3.03]; OR, 4.17 [95% CrI, 1.37-14.28]; OR, 1.85 [95% CrI, 1.22-2.86]; and OR, 2.56 [95% CrI, 1.37-4.76]). In terms of ischemic stroke, dabigatran provided better efficacy than placebo, aspirin, and aspirin + dipyridamole (OR, 0.36 [95% CrI, 0.18-0.72]; OR, 0.43 [95% CrI, 0.21-0.84]; and OR, 0.41 [95% CrI, 0.17-0.94]). As for mortality, dabigatran resulted in a lower mortality compared with aspirin, aspirin + clopidogrel, edoxaban, and warfarin (OR, 0.48 [95% CrI, 0.23-0.97]; OR, 0.40 [95% CrI, 0.17-0.92]; OR, 0.27 [95% CrI, 0.10-0.72]; and OR, 0.52 [95% CrI, 0.28-0.92]).

IMPLICATIONS

There are still some limitations to our NMA research. For instance, the lack of direct evidence for some therapies resulted in inconsistencies, particularly for warfarin compared with placebo and clopidogrel under different end points. Moreover, the included randomized controlled trials for patients with cardiovascular and cerebrovascular diseases are relatively broad, involving atrial fibrillation, myocardial infarction, and large-artery atherosclerosis stroke. Although further research is needed, dabigatran is highly recommended based on the present NAM for the treatment of cardiovascular and cerebrovascular diseases due to the drug's efficacy and safety.

Comparative efficacy and safety of antiplatelet agents in cerebral ischemic disease: A network meta-analysis

We performed a network meta-analysis (NMA) to enhance the corresponding evidence of the relative efficacy and safety of different antiplatelet agents in cerebral ischemic disease. PubMed and EMBASE were searched systematically for relevant studies. Outcomes were compared using odds ratios and 95% credible intervals. Each agent was ranked according to the value of surface under the cumulative ranking curve (SUCRA). Publication bias was evaluated by funnel plots, while consistency between direct and indirect comparison was analyzed by node-splitting and heat plots. Besides, the clustering technique was used to categorize similar agents. A number of 44 eligible studies with 148 578 patients were included in this NMA. In terms of efficacy (including mortality, recurrent stroke, and vascular event), all six interventions were better than placebo. clopidogrel (Clop) and aspirin (ASA)+Clop were the best two interventions from SUCRA. However, the performance of ASA+Clop declined significantly when considering safety (including myocardial infarction, all-cause withdrawal, and intracranial hemorrhage), especially worse in intracranial hemorrhage. In conclusion, Clop was potentially the most preferable treatment for preventing cerebral ischemic in terms of efficacy and safety. However, the addition of ASA was associated with a potential increase in intracranial hemorrhage, therefore, combination therapy of ASA and Clop should be introduced with caution although it may be more effective than the monotherapy of ASA.

Effects of aspirin on risk and severity of early recurrent stroke after transient ischaemic attack and ischaemic stroke: time-course analysis of randomised trials

BACKGROUND

Aspirin is recommended for secondary prevention after transient ischaemic attack (TIA) or ischaemic stroke on the basis of trials showing a 13% reduction in long-term risk of recurrent stroke. However, the risk of major stroke is very high for only the first few days after TIA and minor ischaemic stroke, and observational studies show substantially greater benefits of early medical treatment in the acute phase than do longer-term trials. We hypothesised that the short-term benefits of early aspirin have been underestimated.

METHODS

Pooling the individual patient data from all randomised trials of aspirin versus control in secondary prevention after TIA or ischaemic stroke, we studied the effects of aspirin on the risk and severity of recurrent stroke, stratified by the following time periods: less than 6 weeks, 6-12 weeks, and more than 12 weeks after randomisation. We compared the severity of early recurrent strokes between treatment groups with shift analysis of modified Rankin Scale (mRS) score. To understand possible mechanisms of action, we also studied the time course of the interaction between effects of aspirin and dipyridamole in secondary prevention of stroke. In a further analysis we pooled data from trials of aspirin versus control in which patients were randomised less than 48 h after major acute stroke, stratified by severity of baseline neurological deficit, to establish the very early time course of the effect of aspirin on risk of recurrent ischaemic stroke and how this differs by severity at baseline.

FINDINGS

We pooled data for 15,778 participants from 12 trials of aspirin versus control in secondary prevention. Aspirin reduced the 6 week risk of recurrent ischaemic stroke by about 60% (84 of 8452 participants in the aspirin group had an ischaemic stroke vs 175 of 7326; hazard ratio [HR] 0·42, 95% CI 0·32-0·55, p<0·0001) and disabling or fatal ischaemic stroke by about 70% (36 of 8452 vs 110 of 7326; 0·29, 0·20-0·42, p<0·0001), with greatest benefit noted in patients presenting with TIA or minor stroke (at 0-2 weeks, two of 6691 participants in the aspirin group with TIA or minor stroke had a disabling or fatal ischaemic stroke vs 23 of 5726 in the control group, HR 0·07, 95% CI 0·02-0·31, p=0·0004; at 0-6 weeks, 14 vs 60 participants, 0·19, 0·11-0·34, p<0·0001). The effect of aspirin on early recurrent ischaemic stroke was due partly to a substantial reduction in severity (mRS shift analysis odds ratio [OR] 0·42, 0·26-0·70, p=0·0007). These effects were independent of dose, patient characteristics, or aetiology of TIA or stroke. Some further reduction in risk of ischaemic stroke accrued for aspirin only versus control from 6-12 weeks, but there was no benefit after 12 weeks (stroke risk OR 0·97, 0·84-1·12, p=0·67; severity mRS shift OR 1·00, 0·77-1·29, p=0·97). By contrast, dipyridamole plus aspirin versus aspirin alone had no effect on risk or severity of recurrent ischaemic stroke within 12 weeks (OR 0·90, 95% CI 0·65-1·25, p=0·53; mRS shift OR 0·90, 0·37-1·72, p=0·99), but dipyridamole did reduce risk thereafter (0·76, 0·63-0·92, p=0·005), particularly of disabling or fatal ischaemic stroke (0·64, 0·49-0·84, p=0·0010). We pooled data for 40,531 participants from three trials of aspirin versus control in major acute stroke. The reduction in risk of recurrent ischaemic stroke at 14 days was most evident in patients with less severe baseline deficits, and was substantial by the second day after starting treatment (2-3 day HR 0·37, 95% CI 0·25-0·57, p<0·0001).

INTERPRETATION

Our findings confirm that medical treatment substantially reduces the risk of early recurrent stroke after TIA and minor stroke and identify aspirin as the key intervention. The considerable early benefit from aspirin warrants public education about self-administration after possible TIA. The previously unrecognised effect of aspirin on severity of early recurrent stroke, the diminishing benefit with longer-term use, and the contrasting time course of effects of dipyridamole have implications for understanding mechanisms of action.

FUNDING

Wellcome Trust, the National Institute of Health Research (NIHR) Biomedical Research Centre, Oxford.

Comparative Efficacy and Safety of Nine Anti-Platelet Therapies for Patients with Ischemic Stroke or Transient Ischemic Attack: a Mixed Treatment Comparisons

Anti-platelet treatments, an effective anti-thrombotic therapy, are widely used in non-cardioembolic ischemic stroke or transient ischemic attack (TIA), including aspirin, cilostazol, clopidogrel, and other mono or dual therapies, while the optimal choice remains uncertain. All the literatures of 38 eligible randomized control trials were searched in PubMed, Embase, and China National Knowledge Internet (CNKI) without language limitation. And, nine anti-platelet therapies were assessed, including aspirin, clopidogrel, cilostazol, ticlopidine, triflusal, terutroban, sarpogrelate, dipyridamole plus aspirin, and clopidogrel plus aspirin. Additionally, we extract data of composite vascular events, major bleeding, ischemic stroke, intracranial hemorrhage, and all-cause death, as indicators of efficacy and safety. And among them, composite vascular events were the primary outcome. The binary outcomes were expressed as odds ratios (ORs) with corresponding 95 % confidence intervals (CIs). Both traditional meta-analysis and network meta-analysis were performed. Besides, for each outcome, the rank order was applied to reflect the superiority of every therapy compared with others, using the surface under the cumulative ranking curve (SUCRA). A cluster analysis was also conducted. Through the network meta-analysis, the synthesized data shows that cilostazol performed best on composite vascular events compared with placebo (OR = 0.62, 95 % CI 0.46-0.83) and aspirin (OR = 0.71, 95 % CI 0.53-0.95). In terms of ischemic stroke, clopidogrel plus aspirin seems the optimal, and it has significant difference between placebo (OR = 0.53, 95 % CI 0.35-0.74) and aspirin (OR = 0.75, 95 % CI 0.61-0.95). Meanwhile, cilostazol is also the first rank in major bleeding, especially when it is in contrast to aspirin (OR = 0.13, 95 % CI 0.02-0.70) and clopidogrel plus aspirin (OR = 0.09, 95 % CI 0.01-0.50). There is no significant difference among these nine treatments and placebo, as to all-cause death and intracranial hemorrhage. According to the cluster analysis, cilostazol can be the best choice with comprehensive assessment of composite vascular events, ischemic stroke and major bleeding. Based on this network meta-analysis, cilostazol was recommended as the optimal choice with good performance in both efficacy and safety for patient with ischemic stroke or TIA among nine anti-platelet therapies.

Safety and efficacy of intensive vs. guideline antiplatelet therapy in high-risk patients with recent ischemic stroke or transient ischemic attack: rationale and design of the Triple Antiplatelets for Reducing Dependency after Ischaemic Stroke (TARDIS) trial (ISRCTN47823388)

RATIONALE

The risk of recurrence following a stroke or transient ischemic attack is high, especially immediately after the event.

HYPOTHESIS

Because two antiplatelet agents are superior to one in patients with non-cardioembolic events, more intensive treatment might be even more effective.

SAMPLE SIZE ESTIMATES

The sample size of 4100 patients will allow a shift to less recurrence, and less severe recurrence, to be detected (odds ratio 0·68) with 90% power at 5% significance.

METHODS AND DESIGN

Triple Antiplatelets for Reducing Dependency after Ischaemic Stroke (ISRCTN47823388) is comparing the safety and efficacy of intensive (combined aspirin, clopidogrel, and dipyridamole) vs. guideline antiplatelet therapy, both given for one-month. This international collaborative parallel-group prospective randomized open-label blinded-end-point phase III trial plans to recruit 4100 patients with acute ischemic stroke or transient ischemic attack. Randomization and data collection are performed over a secure Internet site with real-time data validation and concealment of allocation. Outcomes, serious adverse events, and neuroimaging are adjudicated centrally with blinding to treatment allocation.

STUDY OUTCOME

The primary outcome is stroke recurrence and its severity ('ordinal recurrence' based on modified Rankin Scale) at 90 days, with masked assessment centrally by telephone. Secondary outcomes include vascular events, functional measures (disability, mood, cognition, quality of life), and safety (bleeding, death, serious adverse events).

DISCUSSION

The trial has recruited more than 50% of its target sample size (latest number: 2399) and is running in 104 sites in 4 countries. One-third of patients presented with a transient ischemic attack.

Characteristic adverse events and their incidence among patients participating in acute ischemic stroke trials

BACKGROUND AND PURPOSE

Adverse events (AE) in trial populations present a major burden to researchers and patients, yet most events are unrelated to investigational treatment. We aimed to develop a coherent list of expected AEs, whose incidence can be predicted by patient characteristics that will inform future trials and perhaps general poststroke care.

METHODS

We analyzed raw AE data from patients participating in acute ischemic stroke trials. We identified events that occurred with a lower 99% confidence bound greater than nil. Among these, we applied receiver operating characteristic principles to select the fewest types of events that together represented the greatest number of reports. Using ordinal logistic regression, we modeled the incidence of these events as a function of patient age, sex, baseline National Institutes of Health Stroke Scale, and multimorbidity status, defining P<0.05 as statistically significant.

RESULTS

We analyzed 5775 placebo-treated patients, reporting 21 217 AEs. Among 756 types of AEs, 132 accounted for 82.7%, of which 80% began within 10 days after stroke. Right hemisphere (odds ratio [OR], 1.67), increasing baseline National Institutes of Health Stroke Scale (OR, 1.11), multimorbidity status (OR, 1.09 per disease), patient age (OR, 1.01 per year), height (OR, 1.01 per centimeter), diastolic blood pressure (OR, 0.99 per mm Hg), and smoking (OR, 0.82) were independently associated with developing more AEs but together explained only 13% of the variation.

CONCLUSIONS

A list of 132 expected AEs after acute ischemic stroke may be used to simplify interpretation and reporting of complications. AEs can be modestly predicted by patient characteristics, facilitating stratification of patients by risk for poststroke complications.

Antiplatelet strategy for acute ischemic stroke: A mini review

Transient ischemic attacks and minor ischemic strokes have a high risk of an unstable clinical course in the initial 48-72 h after symptom onset. Early antiplatelet treatment is recommended to treat most patients with acute ischemic stroke because few patients can be treated with thrombolysis due to the limit of strict indications, such as a time window. Antiplatelets aim to prevent recurrence or deterioration of stroke. The guidelines recommend the use of aspirin in the acute stage based on two clinical trials. However, some patients still developed recurrence or deterioration of stroke despite timely aspirin administration. Thus, the question remains unclear whether another effective and safe antiplatelet strategy for the treatment of acute ischemic stroke exists. Growing evidence shows that combination antiplatelets may be superior to mono antiplatelets in the treatment of acute ischemic stroke.

Early Dual Versus Mono Antiplatelet Therapy for Acute Non-Cardioembolic Ischemic Stroke or Transient Ischemic Attack

Background—

Emerging studies suggest that early administration of dual antiplatelet therapy may be better than monotherapy for prevention of early recurrent stroke and cardiovascular outcomes in acute ischemic stroke and transient ischemic attack (TIA). We performed a meta-analysis of randomized, controlled trials evaluating dual versus mono antiplatelet therapy for acute noncardioembolic ischemic stroke or TIA.

Methods and Results—

We assessed randomized, controlled trials investigating dual versus mono antiplatelet therapy published up to November 2012 and the CHANCE trial (Clopidogrel in High-risk patients with Acute Non-disabling Cerebrovascular Events), for efficacy and safety outcomes in adult patients with acute noncardioembolic ischemic stroke or TIA with treatment initiated within 3 days of ictus. In total, 14 studies of 9012 patients were included in the systematic review and meta-analysis. Dual antiplatelet therapy significantly reduced risk of stroke recurrence (risk ratio, 0.69; 95% confidence interval, 0.60–0.80; P <0.001) and the composite outcome of stroke, TIA, acute coronary syndrome, and all death (risk ratio, 0.71; 95% confidence interval, 0.63–0.81; P <0.001) when compared with monotherapy, and nonsignificantly increased risk of major bleeding (risk ratio, 1.35; 95% confidence interval, 0.70–2.59, P =0.37). Analyses restricted to the CHANCE Trial or the 7 double-blind randomized, controlled trials showed similar results.

Conclusions—

For patients with acute noncardioembolic ischemic stroke or TIA, dual therapy was more effective than monotherapy in reducing risks of early recurrent stroke. The results of the CHANCE study are consistent with previous studies done in other parts of the world.

Antiplatelet therapy for carotid artery stenting

Carotid artery stenting (CAS) is less invasive and has a lower incidence of systemic complications such as myocardial infarction compared with carotid endarterectomy. However, CAS is known to have a high incidence of ischemic complications due to distal thromboembolism. Progress has been made in the development of various distal protection devices and protection methods aimed at preventing thromboembolism. Similar to these methods, perioperative antiplatelet therapy is also able to play a very important role in the prevention of ischemic events. Dual antiplatelet therapy has become standard for perioperative management of CAS.

Cilostazol for the prevention of acute progressing stroke: a multicenter, randomized controlled trial

BACKGROUND

Progressing stroke is one of the major determinants of outcome after acute ischemic stroke. A pilot randomized controlled trial was conducted to investigate the effect of cilostazol on progressing stroke.

METHODS

Adult patients with noncardioembolic ischemic stroke within 24 hours after onset were randomized to receive cilostazol 200 mg/day (cilostazol group) or no medication (control group) in addition to the optimum medical treatments (a free radical scavenger plus an antiplatelet agent or an antithrombin agent). The primary endpoints were the rate of progressing stroke, defined as aggravation of the National Institutes of Health Stroke Scale (NIHSS) score by ≥ 4 points on days 3 and/or 5 and a modified Rankin Scale score of 0 to 1 at 3 months after enrollment. Aggravation caused by systemic complications, edema, hemorrhagic infarction, or recurrent stroke was not considered as progressing stroke. This trial was registered as UMIN000001630.

RESULTS

A total of 510 patients were enrolled from 55 institutions in Japan between February 2009 and July 2010. The rate of progressing stroke was 3.2% and 6.3% in the cilostazol and control groups, respectively (P = .143). The modified Rankin Scale score of 0 to 1 at 3 months did not differ between the groups.

CONCLUSIONS

Cilostazol failed to show a preventive effect against acute progressing stroke. However, the tendency to reduce progressing stroke and the results of stratified analyses may encourage additional studies to clarify the effect of cilostazol in the treatment of acute ischemic stroke.

Blood pressure lowering in acute phase of stroke: latest evidence and clinical implications

Persistent controversy exists as to whether there are worthwhile beneficial effects of early, rapid lowering of elevated blood pressure (BP) in acute stroke. Elevated BP or 'hypertension' (i.e. systolic >140 mmHg) is common in stroke, especially in patients with pre-existing hypertension and large strokes, due to variable 'autonomic stress' and raised intracranial pressure. While positive associations between BP levels and poor outcomes are evident across a range of studies, very low BP levels and large reductions in BP have also been shown to predict death and dependence, more so for ischaemic stroke (IS) than intracerebral haemorrhage (ICH). Accumulating evidence indicates that early BP lowering can reduce haematoma expansion in ICH, but there is uncertainty over whether this translates into improved clinical outcomes, particularly since such an effect was not evident from haemostatic therapy in clinical trials. Guidelines generally recommend control of high systolic BP (>180 mmHg), but recent evidence indicates that even more modest elevation (>140 mmHg) increases risks of cerebral oedema and haemorrhagic transformation following thrombolysis in IS. Thus, any potential benefits of rapid BP lowering in acute stroke, particularly in IS, must be balanced against the potential risks of worsening cerebral ischaemia from altered autoregulation/perfusion. This paper explores current knowledge regarding the management of hypertension in acute stroke and introduces ongoing clinical trials aimed at resolving such a critical issue in the care of patients with acute stroke.

Adenosine-diphosphate (ADP) receptor antagonists for the prevention of cardiovascular disease in type 2 diabetes mellitus

BACKGROUND

Cardiovascular disease (CVD) is the most prevalent complication of type 2 diabetes with an estimated 65% of people with type 2 diabetes dying from a cause related to atherosclerosis. Adenosine-diphosphate (ADP) receptor antagonists like clopidogrel, ticlopidine, prasugrel and ticagrelor impair platelet aggregation and fibrinogen-mediated platelet cross-linking and may be effective in preventing CVD.

OBJECTIVES

To assess the effects of adenosine-diphosphate (ADP) receptor antagonists for the prevention of cardiovascular disease in type 2 diabetes mellitus.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (issue 2, 2011), MEDLINE (until April 2011) and EMBASE (until May 2011). We also performed a manual search, checking references of original articles and pertinent reviews to identify additional studies.

SELECTION CRITERIA

Randomised controlled trials comparing an ADP receptor antagonist with another antiplatelet agent or placebo for a minimum of 12 months in patients with diabetes. In particular, we looked for trials assessing clinical cardiovascular outcomes.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data for studies which fulfilled the inclusion criteria, using standard data extraction templates. We sought additional unpublished information and data from the principal investigators of all included studies.

MAIN RESULTS

Eight studies with a total of 21,379 patients with diabetes were included. Three included studies investigated ticlopidine compared to aspirin or placebo. Five included studies investigated clopidogrel compared to aspirin or a combination of aspirin and dipyridamole, or compared clopidogrel in combination with aspirin to aspirin alone. All trials included patients with previous CVD except the CHARISMA trial which included patients with multiple risk factors for coronary artery disease. Overall the risk of bias of the trials was low. The mean duration of follow-up ranged from 365 days to 913 days.Data for diabetes patients on all-cause mortality, vascular mortality and myocardial infarction were only available for one trial (355 patients). This trial compared ticlopidine to placebo and did not demonstrate any statistically significant differences for all-cause mortality, vascular mortality or myocardial infarction. Diabetes outcome data for stroke were available in three trials (31% of total diabetes participants). Overall pooling of two (statistically heterogeneous) studies showed no statistically significant reduction in the combination of fatal and non-fatal stroke (359/3194 (11.2%) versus 356/3146 (11.3%), random effects odds ratio (OR) 0.81; 95% confidence interval (CI) 0.44 to 1.49) for ADP receptor antagonists versus other antiplatelet drugs. There were no data available from any of the trials on peripheral vascular disease, health-related quality of life, adverse events specifically for patients with diabetes, or costs.

AUTHORS' CONCLUSIONS

The available evidence for ADP receptor antagonists in patients with diabetes mellitus is limited and most trials do not report outcomes for patients with diabetes separately. Therefore, recommendations for the use of ADP receptor antagonists for the prevention of CVD in patients with diabetes are based on available evidence from trials including patients with and without diabetes. Trials with diabetes patients and subgroup analyses of patients with diabetes in trials with combined populations are needed to provide a more robust evidence base to guide clinical management in patients with diabetes.

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.

Antiplatelet therapy in cerebrovascular disorders

Antiplatelet treatment is a mainstay in acute and long-term secondary stroke prevention. Aspirin is still most widely used worldwide, however, there is increasing evidence from small randomised trials that dual antiplatelet therapy combining aspirin with dipyridamole or clopidogrel might be more effective in the acute and early chronic post-ischemic phase (i.e. first 90 days). Both clopidogrel and the combination of aspirin and extended-release dipyridamole are recommended by current guidelines in long-term secondary stroke prevention in patients who are at high risk for a recurrent ischemic stroke, since they are more effective compared with aspirin monotherapy. Antiplatelet agents are the therapy of choice in patients with ischemic stroke due to intracranial stenosis and patent foramen ovale. In contrast, oral anticoagulation is clearly superior to single or double antiplatelet therapy in patients with cardioembolic stroke, mainly caused by atrial fibrillation.Concerning newer antiplatelet agents, only cilostazol appears to be a promising therapeutic option in patients with ischemic stroke in the near future, but so far, only studies in Asian stroke patients have been performed.

Current therapies in ischemic stroke. Part A. Recent developments in acute stroke treatment and in stroke prevention

Stroke is the third leading cause of death with an increasing prevalence. In previous years many important achievements and new therapeutic strategies have been established. This article provides an overview on recent developments and is an update to the article of Green et al. that was published in 2004. As this article is a comprehensive review we divided it in two parts. In this Part A of our review, recent developments in acute stroke treatment and in stroke prevention are described. In Part B we will reflect on neuroprotection.

Antiplatelet therapy in secondary stroke prevention--state of the art

Our objective is to provide the reader with an overview as well as an update on current antiplatelet therapy for secondary stroke prevention. Relevant journals were hand-searched by the authors to compile a broad but by far not comprehensive summary of innovative and clinically relevant studies. Aspirin, clopidogrel and the combination of dipyridamole plus aspirin are the cornerstone therapy in secondary prevention after non-cardio-embolic stroke or transient ischaemic attack. A head-to-head comparison showed no difference in the prevention of recurrent stroke between dipyridamole plus aspirin and clopidogrel. More potent antiplatelet drugs or the combination of aspirin and clopidogrel prevent more ischaemic events, but also lead to more bleeding complications. For secondary stroke prevention in patients with atrial fibrillation, oral anticoagulation is more effective than aspirin or the combination of aspirin and clopidogrel.

Dipyridamole reverses peripheral ischemia and induces angiogenesis in the Db/Db diabetic mouse hind-limb model by decreasing oxidative stress

Dipyridamole anti-platelet therapy has previously been suggested to ameliorate chronic tissue ischemia in healthy animals. However, it is not known if dipyridamole therapy represents a viable approach to alleviating chronic peripheral tissue ischemia associated with type 2 diabetes. Here we examine the hypothesis that dipyridamole treatment restores reperfusion of chronic hind-limb ischemia in the murine B6.BKS-Lepr(db/db) diabetic model. Dipyridamole therapy quickly rectified ischemic hind-limb blood flow to near preligation levels within 3 days of the start of therapy. Restoration of ischemic tissue blood flow was associated with increased vascular density and endothelial cell proliferation observed only in ischemic limbs. Dipyridamole significantly increased total nitric oxide metabolite levels in tissue, which were not associated with changes in endothelial NO synthase expression or phosphorylation. Interestingly, dipyridamole therapy significantly decreased ischemic tissue superoxide and protein carbonyl levels, identifying a dominant antioxidant mechanistic response. Dipyridamole therapy also moderately reduced diabetic hyperglycemia and attenuated development of dyslipidemia over time. Together, these data reveal that dipyridamole therapy is an effective modality for the treatment of chronic tissue ischemia during diabetes and highlights the importance of dipyridamole antioxidant activity in restoring tissue NO bioavailability during diabetes.

Adenosine derived from ADP can contribute to inhibition of platelet aggregation in the presence of a P2Y12 antagonist

OBJECTIVE

To investigate whether adenosine diphosphate (ADP)-derived adenosine might inhibit platelet aggregation, especially in the presence of a P2Y₁₂ antagonist, where the effects of ADP at the P2Y₁₂ receptor would be prevented.

METHODS AND RESULTS

Platelet aggregation was measured in response to thrombin receptor activator peptide by platelet counting in platelet-rich plasma (PRP) and whole blood in the presence of ADP and the P2Y₁₂ antagonists cangrelor, prasugrel active metabolite, and ticagrelor. In the presence of a P2Y₁₂ antagonist, preincubation of PRP with ADP inhibited aggregation; this effect was abolished by adenosine deaminase. No inhibition of aggregation occurred in whole blood except when dipyridamole was added to inhibit adenosine uptake into erythrocytes. The effects of ADP in PRP and whole blood were replicated using adenosine and were directly related to changes in cAMP (assessed by vasodilator-stimulated phosphoprotein phosphorylation). All results were the same irrespective of the P2Y₁₂ antagonist used.

CONCLUSIONS

ADP inhibits platelet aggregation in the presence of a P2Y₁₂ antagonist through conversion to adenosine. Inhibition occurs in PRP but not in whole blood except when adenosine uptake is inhibited. None of the P2Y₁₂ antagonists studied replicated the effects of dipyridamole in the experiments that were performed.