Clopidogrel resistance and the effect of combination cilostazol in patients with ischemic stroke or carotid artery stenting using the VerifyNow P2Y12 Assay

Racial differences in P2Y12 inhibitor responsiveness in patients undergoing neuro-endovascular procedures: A cohort from the Middle East

BACKGROUND

Data on P2Y12 inhibitors responsiveness from the middle east is scarce. We sought to investigate patient responsiveness to P2Y12 inhibitors within a cohort of major races that characterize the UAE population. The secondary objective was to assess risk factors for hyper and hypo-responsiveness in this population.

METHODS

We conducted a cross-sectional study on adults who received either clopidogrel or ticagrelor treatments and had platelet responsiveness testing before undergoing neuro-endovascular interventions at our quaternary care hospital between March 2015 and April 2019.

RESULTS

During the study period, 249 subjects met the inclusion criteria. Overall, 17.3 % were hyper-responsive and 25.7 % were hypo-responsive to P2Y12 inhibitors. When comparing between the P2Y12 inhibitors, rates of hyper-responsiveness were significantly higher to ticagrelor when compared to clopidogrel (11 versus 6 %, p = 0.02 respectively). Contrarily, hypo-responsiveness rates were significantly higher in clopidogrel treated patients compared to their ticagrelor treated counterparts (23 versus 2 %, p < .001 respectively). Patients of Middle-Eastern origin showed a significantly higher rate of hypo-responsiveness to both clopidogrel and ticagrelor when compared to other races (41.1 % and 26.7 %, P < 0.001 respectively). Asians showed the highest rates of hyper-responsiveness for both agents. Multivariate logistic regression analysis showed that proton pump inhibitors and statin combination, (OR: 6.39, 95 %CI [1.60, 25.392]), and Middle East vs. Indian subcontinent patients (OR: 4.67, 95 %CI [1.79-12.14]) were independent predictors of hypo-responsiveness to both P2Y12 inhibitors.

CONCLUSION

This study demonstrated a high rate of hypo-responsiveness to P2Y12 inhibitors in a UAE cohort of patients undergoing neuro-endovascular procedures. In addition, therapeutic responsiveness to P2Y12 inhibitors varied markedly based on the racial background. Future larger studies are needed to evaluate genetic variations that may contribute to this rate of hypo-responsiveness in our population.

Differential inhibition of platelet function by cilostazol in combination with clopidogrel

PURPOSE

To assess the antiplatelet effect of cilostazol clinically, we compared the effects of cilostazol in combination with clopidogrel on various platelet function tests.

METHODS

We recruited patients with ischemic stroke at high risk of recurrence who were treated with clopidogrel alone within 180 days after stroke onset. Subjects underwent baseline platelet function tests, and were then randomly assigned to receive dual antiplatelet therapy (DAPT) comprising clopidogrel and cilostazol or clopidogrel monotherapy (SAPT). After 6 months, platelet function was measured again and compared to that at baseline in each group, and the rate of change was compared between groups.

RESULTS

Thirty-four patients were enrolled, but 4 patients were excluded for various reasons. In total, 30 subjects (13 in DAPT and 17 in SAPT group) were analyzed. Adenosine diphosphate- and collagen-induced aggregation, VerifyNow P2Y12 reaction units, vasodilator-stimulated phosphoprotein (platelet reactivity index: PRI) and plasma p-selectin concentration were significantly lower (P = 0.004, 0.042, 0.049, 0.003 and 0.006 respectively), while VerifyNow % inhibition was significantly higher at 6 months compared to baseline (P = 0.003) in the DAPT group only. Comparison of the rate of change in each parameter from baseline to 6 months showed that while PRI decreased at a greater rate (P = 0.012), VerifyNow % inhibition increased at a greater rate (P = 0.003) in the DAPT group than the SAPT group.

CONCLUSIONS

The inhibitory effects of adjunctive cilostazol added to clopidogrel on platelet function differed by type of platelet function test. VerifyNow % inhibition and PRI were more inhibited than the other platelet function tests.

TRIAL REGISTRATION

CSPS.com substudy in TWMU (UMIN000026672), registered on April 1, 2017. This study was performed as a substudy of CSPS.com (UMIN000012180, registered on October 31, 2013) and was retrospectively registered.

Update on Cilostazol: A Critical Review of Its Antithrombotic and Cardiovascular Actions and Its Clinical Applications

Cilostazol, a phosphodiesterase III inhibitor, has vasodilating and antiplatelet properties with a low rate of bleeding complications. It has been used over the past 25 years for improving intermittent claudication in patients with peripheral artery disease (PAD). Cilostazol also has demonstrated efficacy in patients undergoing percutaneous revascularization procedures for both PAD and coronary artery disease. In addition to its antithrombotic and vasodilating actions, cilostazol also inhibits vascular smooth muscle cell proliferation via phosphodiesterase III inhibition, thus mitigating restenosis. Accumulated evidence has shown that cilostazol, due to its "pleiotropic" effects, is a useful, albeit underutilized, agent for both coronary artery disease and PAD. It is also potentially useful after ischemic stroke and is an alternative in those who are allergic or intolerant to classical antithrombotic agents (eg, aspirin or clopidogrel). These issues are herein reviewed together with the pharmacology and pharmacodynamics of cilostazol. Large studies and meta-analyses are presented and evaluated. Current guidelines are also discussed, and the spectrum of cilostazol's actions and therapeutic applications are illustrated.

Clinical importance of testing for clopidogrel resistance in patients undergoing carotid artery stenting-a systematic review

Dual antiplatelet therapy is frequently prescribed for patients undergoing carotid artery stenting (CAS), however clopidogrel resistance might cause thromboembolic complications. The role of testing for clopidogrel resistance in patients undergoing CAS is unclear. In this study, we aimed to review the periprocedural thromboembolic outcomes in clopidogrel resistant patients who underwent CAS. We conducted a review of PubMed, EMBASE, and the Cochrane Library up to October 7, 2020. Studies were included that investigated at least ten patients aged 18 years or older with a symptomatic carotid artery stenosis requiring CAS. Studies were excluded that investigated patients with a carotid artery dissection, case reports, case series of less than ten patients, reviews, commentaries, letters to the editors, and conference abstracts. The primary endpoint was the incidence of thromboembolic events. One hundred seventy-seven unique articles were identified of which three studies were included in our systematic review. The sample sizes ranged from 76 to 449 patients and the follow-up duration from 24 hours to 2 years postprocedural. Two retrospective observational studies determined clopidogrel resistance using measurement of P2Y12 reaction units, and one historical cohort study used genetic testing. Two studies concluded that clopidogrel resistance was a risk factor for thromboembolic complications, the other found higher values of P2Y12 reaction units in patients with thromboembolic events compared to those without. In conclusion, current literature supports a possible relationship between clopidogrel resistance and thromboembolic complications in patients who underwent CAS. Preprocedural testing for clopidogrel resistance might therefore be of additional value. Randomized studies using a valid, reliable clopidogrel resistance test and clinical endpoints, are however required to make a definitive statement and to determine the impact of the thromboembolic complications. This study was registered within PROSPERO (CRD42020197318).

High on-clopidogrel platelet reactivity in ischaemic stroke or transient ischaemic attack: Systematic review and meta-analysis

OBJECTIVES

To assess the prevalence of high on-clopidogrel platelet reactivity (HCPR) in patients with ischaemic stroke or transient ischaemic attack (IS/TIA), their outcome and genetic basis of on-treatment response variability in IS/TIA patients.

METHODS

We conducted a comprehensive search of PubMed and EMBASE from their inceptions to March 9, 2019. Studies that reported absolute numbers/percentages of HCRP at any time point after IS/TIA onset evaluated with any type of platelet function tests, clinical outcomes and genotyping data were included.

RESULTS

Among 21 studies of 4312 IS/TIA patients treated with clopidogrel, the pooled prevalence of HCPR was 28% (95%CI: 24-32%; high heterogeneity: I² = 88.2%, p < 0.001). Heterogeneity degree diminished across groups defined by the HCPR testing method. Clopidogrel non-responder IS/TIA patients had poorer outcome compared to responders (RR = 2.09, 95%CI: 1.61-2.70; p = 0.036; low heterogeneity across studies: I² = 27.4%, p = 0.210). IS/TIA carriers of CYP2C19*2 or CYP2C19*3 loss of function alleles had a higher risk of HCPR compared to wild type (RR = 1.69, 95%CI: 1.47-1.95; p < 0.001; I² = 0.01%, p = 0.475).

CONCLUSIONS

This systematic review shows a high prevalence of clopidogrel resistance in IS/TIA and poor outcome in these patients. CYP2C19 polymorphisms may potentially influence clopidogrel resistance.

Periprocedural Neuroendovascular Antiplatelet Strategies for Thrombosis Prevention in Clopidogrel-Hyporesponsive Patients

Patients undergoing neuroendovascular procedures such as cerebral aneurysm coiling and intracranial stent deployment are frequently treated with antiplatelet agents to prevent thrombotic complications. The combination of aspirin and a P2Y12 inhibitor such as clopidogrel is often initiated days before elective procedures or as loading doses for emergent procedures; however, some patients may still experience thrombotic complications. Patients identified as clopidogrel hyporesponders are more likely to experience poor outcomes and may require changes to their regimens. Historically, high-dose clopidogrel regimens were used in response to subtherapeutic results of platelet function assays and point-of-care testing despite limited supporting data. Recently, more data have emerged using alternative P2Y12 inhibitors such as prasugrel and ticagrelor. Dosing for neuroendovascular conditions is often extrapolated from the cardiac literature, although outcomes in cardiac patients may not be relevant to neurologic patients, making prophylactic treatment recommendations challenging for these patients. This review summarizes the literature for antiplatelet prophylaxis in patients undergoing neuroendovascular device placement, focusing on alternative regimens for clopidogrel hyporesponders.

Prevalence of poor biological response to clopidogrel

The existence of poor biological response to clopidogrel has been shown in some patients. Despite the increasing number of studies, this phenomenon remains difficult to quantify. We performed a systematic review to estimate the prevalence of poor biological response to clopidogrel and investigate the factors known to modulate this. An exhaustive search was performed. Altogether 171 publications were identified, providing data for a total of 45,664 subjects. The estimated prevalence of poor biological response to clopidogrel ranged from 15.9% to 49.5% according to the platelet function assay employed. The assays most frequently used were light transmittance aggregometry (LTA), the vasodilator-stimulated phosphoprotein (VASP) assay and the Verify -now® assay. For all these assays, higher cut-off values were associated with a lower prevalence of poor biological response to clopidogrel. However, when choosing a fixed cut-off point for each assay, the prevalence of poor biological response to clopidogrel was highly variable suggesting that other factors could modulate poor biological response to clopidogrel. Finally, none of the studied factors could apparently explain the variability of poor biological response to clopidogrel. This meta-analysis shows that the prevalence of poor biological response depends on the assay employed, the cut-off value and on various unidentified additional factors.

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.

Association between Postprocedural Infarction and Antiplatelet Drug Resistance after Coiling for Unruptured Intracranial Aneurysms

BACKGROUND AND PURPOSE

Procedure-related thromboembolism is a major limitation of coil embolization, but the relationship between thromboembolic infarction and antiplatelet resistance is poorly understood. The purpose of this study was to verify the association between immediate postprocedural thromboembolic infarction and antiplatelet drug resistance after endovascular coil embolization for unruptured intracranial aneurysm.

MATERIALS AND METHODS

This study included 338 aneurysms between October 2012 and March 2015. All patients underwent postprocedural MR imaging within 48 hours after endovascular coil embolization. Antiplatelet drug resistance was checked a day before the procedure by using the VerifyNow system. Abnormal antiplatelet response was defined as >550 aspirin response units and >240 P2Y12 receptor reaction units. In addition, we explored the optimal cutoff values of aspirin response units and P2Y12 receptor reaction units. The primary outcome was radiologic infarction based on postprocedural MR imaging.

RESULTS

Among 338 unruptured intracranial aneurysms, 134 (39.6%) showed diffusion-positive lesions on postprocedural MR imaging, and 32 (9.5%) and 105 (31.1%) had abnormal aspirin response unit and P2Y12 receptor reaction unit values, respectively. Radiologic infarction was associated with advanced age (65 years and older, P = .024) only with defined abnormal antiplatelet response (aspirin response units ≥ 550, P2Y12 receptor reaction units ≥ 240). P2Y12 receptor reaction unit values in the top 10th percentile (>294) were associated with radiologic infarction (P = .003). With this cutoff value, age (adjusted odds ratio, 2.29; 95% confidence interval, 1.28-4.08), P2Y12 receptor reaction units (>294; OR, 3.43; 95% CI, 1.53-7.71), and hyperlipidemia (OR, 2.05; 95% CI, 1.04-4.02) were associated with radiologic infarction in multivariate analysis.

CONCLUSIONS

Radiologic infarction after coiling for unruptured aneurysm was closely associated with age. Only very high P2Y12 receptor reaction unit values (>294) predicted postprocedural infarction. Further controlled studies are needed to determine the precise cutoff values, which could provide information regarding the optimal antiplatelet regimen for aneurysm coiling.

Antiplatelet Therapy of Cilostazol or Sarpogrelate with Aspirin and Clopidogrel after Percutaneous Coronary Intervention: A Retrospective Cohort Study Using the Korean National Health Insurance Claim Database

Background/Objectives

Addition of cilostazol or sarpogrelate to the standard dual antiplatelet therapy of aspirin and clopidogrel has been implemented in patients that underwent percutaneous coronary intervention (PCI) with stents in Korea. This study aimed to evaluate the efficacy and safety of triple antiplatelet therapies.

Methods

This retrospective cohort study was performed using the Korean National Insurance Claim Data of the Health Insurance Review and Assessment Service from January 1, 2009 to December 31, 2014. The study cohort population consisted of patients with ischemic heart diseases and a history of PCI. They were treated with antiplatelet therapy of aspirin, clopidogrel (AC); aspirin, clopidogrel, cilostazol (ACCi); or aspirin, clopidogrel, sarpogrelate (ACSa) during the index period from January 1, 2010 to December 31, 2011. During the follow-up period up to December 31, 2014, the major adverse cardiac or cerebral events (MACCE) including death, myocardial infarction, target lesion revascularization, and ischemic stroke were assessed. Bleeding complications were also evaluated as adverse drug events.

Results

Out of 93,876 patients with PCI during the index period, 69,491 patients started dual (AC) or triple therapy (ACSa or ACCi). The clinical outcomes of comparing ACSa and ACCi therapy showed beneficial effects in the ACSa group in the prevention of subsequent cardiac or cerebral events. After Propensity score-matching between ACSa and ACCi groups, there were significant differences in MI and revascularization, with corresponding HR of 0.38 (95% CI, 0.20–0.73) and 0.66 (95% CI, 0.53–0.82) in ACSa vs. ACCi at 12 months, respectively. At the 24-month follow-up, the triple therapy groups (ACS or ACC) had a higher incidence of MACCE compared to the dual therapy (AC) group; ACSa vs. AC HR of 1.69 (95% CI, 1.62–1.77); ACC vs. AC HR of 1.22 (95% CI, 1.06–1.41). There was no significant difference in severe or life-threatening bleeding risk among three groups; ACSa vs. AC, HR of 0.68 (95% CI, 0.37–1.24), ACCi vs. AC, HR of 0.91 (95% CI, 0.77–1.09).

Conclusion

Sarpogrelate-containing triple antiplatelet therapy demonstrated comparable rates of MACCE prevention to the conventional dual antiplatelet therapy after PCI without significantly increasing bleeding risk during the two-year follow-up period.

Prevalence and risk factors of clopidogrel non-response among Saudi patients undergoing coronary angiography

OBJECTIVES

To estimate the prevalence of clopidogrel non-response and identify its risk factors among Saudi patients. 

METHODS

This cross-sectional study was conducted at Prince Sultan Cardiac Center, Riyadh, Kingdom of Saudi Arabia between January and June 2013, to assess the degree of platelet inhibition using the VerifyNow assay (Accumetrics, San Diego, CA, USA) after receiving clopidogrel standard loading dose. Clopidogrel resistance was defined as ≤15% platelet inhibition or greater than 213 P2Y12 reaction units (PRU). 

RESULTS

Three hundred and four patients were included in the study. The mean age was 60.3 ± 11.4 years, and 73% were males. Clopidogrel doses were 300 mg (57%), 600 mg (27%), and 75 mg (16%). All patients used aspirin (81 mg in 94%). Approximately 66% (200/304) showed in vitro clopidogrel non-response, 54% had low platelet inhibitions, and 61% had high post-loading PRU. Using multivariate regression analysis that included all significant characteristics; only diabetes (odds ratio [OR]: 2.36, 95% confidence interval [CI]: 1.30-4.27, p=0.005) and higher preloading PRU (OR: 2.39, 95% CI: 1.40-4.11, p=0.002) remained significantly associated with higher clopidogrel non-response while myocardial infarction (OR: 0.34, 95% CI: 0.15-0.81, p=0.014) remained significantly associated with lower clopidogrel non-response. The associations of morbid obesity and diuretics use with higher clopidogrel non-response were slightly attenuated.  

CONCLUSION

Our findings indicate a high rate of clopidogrel in-vitro non-response among Saudi patients undergoing coronary angiography.

Predictive value of high residual platelet reactivity by flow cytometry for outcomes of ischemic stroke patients on clopidogrel therapy

High residual platelet reactivity (HRPR) assessed by multiple tests has been associated with worse clinical outcomes. However, the clinical impact of HRPR assessed by flow cytometry is unknown. The aim of this study was to validate the predictive value of HRPR measured by flow cytometry for clinical outcomes in ischemic stroke patients during clopidogrel therapy. Overall, 198 consecutive patients with ischemic stroke taking clopidogrel underwent platelet function testing on flow cytometer including adenosine diphosphate (ADP)-induced platelet aggregation (PAg) and platelet activation markers (CD62P, CD63, and PAC-1). Poor outcome was defined as poor prognosis and ischemic events during 12-month follow-up. By receiver operating characteristic curve analysis, residual platelet reactivity assessed by flow cytometry was able to distinguish between patients with and without poor outcomes, when platelet inhibition was evaluated with ADP-PAg (area under the curve [AUC], .77; 95% confidence interval [CI], .69-.84; P < .001), CD62P (AUC, .73; 95% CI, .64-.81; P < .001), CD63 (AUC, .72; 95% CI, .64-.80; P < .001), and PAC-1 (AUC, .70; 95% CI, .62-.78; P < .001). The prevalence of HRPR was 25.8% for ADP-PAg, 32.8% for CD62P, 41.4% for CD63, and 56.1% for PAC-1. The multiple logical regression analysis demonstrated that HRPR was an independent predictor of poor outcomes (ADP-PAg: odds ratio [OR] 13.03, 95% CI 5.66-29.98, P < .001; CD62P: OR 8.55, 95% CI 3.94-18.57, P < .001; CD63: OR 8.74, 95% CI 3.89-19.64, P < .001; PAC-1: OR 4.23, 95% CI 1.98-9.08). In conclusion, HRPR, assessed by flow cytometry, is able to detect ischemic stroke patients at increased risk of 12-month poor outcomes on clopidogrel treatment.

High on-treatment platelet reactivity in patients with ischemic cerebrovascular disease: assessment of prevalence and stability over time using four platelet function tests

High on-treatment platelet reactivity (HTPR), referred to as a higher than expected platelet reactivity in patients under antiplatelet therapy, could influence outcome in cerebrovascular disease (CVD), but its prevalence and its stability over time is uncertain. Platelet reactivity was assessed in 18 patients with ischemic stroke/transient ischemic attack (TIA) 7 days (D7) and 90 days (D90) after prescription of clopidogrel, using four methods: light transmission aggregometry with 5 μmol/l ADP (LTA-ADP), vasodilator-stimulated phosphoprotein (VASP), Verify Now P2Y12 and platelet function analyzer (PFA) P2Y. HTPR was defined as LTA-ADP more than 46%; PFA-100-P2Y closure time less than 106 s; VerifyNow P2Y12, PRU greater than 235, VASP, PRI greater than 50%. Patients displayed, both at D7 and D90, a marked inhibition of platelet reactivity towards ADP in all tests as compared with reference levels. Correlations between the results obtained with all the tests at D7 and D90 and between measurements on each day in each test were low-to-moderate. The prevalence of HTPR for all the tests was 40% at D7 and 42% at D90. There was a moderate degree of agreement (k statistic < 0.5) between tests with regard to categorizing patients as HTPR/No-HTPR (D7 and D90). The on-clopidogrel platelet reactivity phenotype, HTPR/No-HTPR, remained stable in 55-72% of patients, depending on the test. A high prevalence of HTPR is found among CVD patients treated with clopidogrel and this platelet reactivity phenotype remains over time. There is poor agreement between the different platelet function tests for categorizing the platelet reactivity phenotype in these patients. The new PFA-100 P2Y equals other platelet function assays for evaluating HTPR in CVD.

Thromboembolic complications in patients with clopidogrel resistance after coil embolization for unruptured intracranial aneurysms

BACKGROUND AND PURPOSE

Antiplatelet resistance is known to be associated with symptomatic ischemic complication after endovascular coil embolization. The purpose of our study was to evaluate the relationship between antiplatelet resistance and clinically silent thromboembolic complications using DWI in patients who underwent coil embolization for unruptured intracranial aneurysm.

MATERIALS AND METHODS

Between October 2011 and May 2013, 58 patients with 62 unruptured aneurysms who were measured for antiplatelet response using VerifyNow assay and underwent elective coil embolization for an unruptured aneurysm with posttreatment DWI were enrolled. Diffusion-positive lesions were classified into 3 groups according to the number of lesions (n=0 [grade 0], n<6 [grade I], and n≥6 [grade II]). The relationship between antiplatelet resistance and diffusion-positive lesions was analyzed.

RESULTS

Sixty-two endovascular coiling procedures were performed on 58 patients. Clopidogrel resistance was revealed in 23 patients (39.7%) and diffusion-positive lesions were demonstrated in 28 patients (48.3%); these consisted of 19 (32.8%) grade I and 9 (15.5%) grade II lesions. Clopidogrel resistance was not relevant to the development of any diffusion-positive lesion (grade I and II, P=.789) but was associated with the development of multiple diffusion-positive lesions (grade II, P=.002). In the logistic regression prediction model, clopidogrel resistance showed significant correlation with the development of grade II lesions (P=.001).

CONCLUSIONS

Multiple diffusion-positive lesions (≥6 in number) occurred more frequently in patients with clopidogrel resistance after endovascular coiling for unruptured aneurysms.

Relationship between smoking and responsiveness to clopidogrel in non-cardiogenic ischemic stroke patients

OBJECTIVE

Clopidogrel is used to prevent the recurrence of non-cardiogenic ischemic stroke, but individual responsiveness to the drug varies. Moreover, it is known that smoking, which is a risk factor for ischemic stroke, affects the drug's pharmacokinetics. The objective of the present study was to investigate a possible relationship between smoking and responsiveness to clopidogrel in non-cardiogenic ischemic stroke patients.

METHODS

The study involved 209 non-cardiogenic ischemic stroke patients who were administered oral clopidogrel at a dosage of 75 mg/day for at least 1 week. Platelet aggregation in response to adenosine diphosphate (20 μM) was measured in each patient using the VerifyNow P2Y12 Assay. Platelet aggregation and the incidence of resistance to clopidogrel were compared between a smokers group (70 patients) and a non-smokers group (139 patients). Clopidogrel resistance was defined as a P2Y12 Reaction Units (PRU) value >230 and/or % inhibition <20%.

RESULTS

The mean PRU was 128.3±85.5 in the smokers group and 167.7±86.6 in the non-smokers group (p=0.002). The incidence of PRU >230 was 12.9% (9 patients) in the smokers group and 25.9% (36 patients) in the non-smokers group (p=0.033). The mean % inhibition was 48.6±30.7% in the smokers group and 36.9±27.6% in the non-smokers group (p=0.009). The incidence of patients with % inhibition <20% was 24.3% (17 patients) in the smokers group and 34.5% (48 patients) in the non-smokers group (p=0.155).

CONCLUSION

The incidence of clopidogrel resistance was lower in the non-cardiogenic ischemic stroke patients who were smokers, thus indicating that these patients' responsiveness to this drug may be enhanced.

Response to clopidogrel and its association with chronic kidney disease in noncardiogenic ischemic stroke patients

OBJECTIVE

Noncardiogenic ischemic stroke patients with chronic kidney disease (CKD) are known to have a greater rate of ischemic stroke recurrence than those without. Although clopidogrel is often used to prevent the recurrence of noncardiogenic ischemic stroke, the relationship between the response to clopidogrel and CKD is unclear. In the present study, the relationship between the response to clopidogrel and the presence of CKD was investigated in noncardiogenic ischemic stroke patients.

METHODS

A total of 129 noncardiogenic ischemic stroke patients receiving 75 mg/day of clopidogrel for ≥1 week were evaluated. The VerifyNow P2Y12 Assay was used to measure the level of platelet aggregation induced by 20 μM of adenosine diphosphate, and the degree of platelet aggregation and frequency of clopidogrel resistance were compared between 34 patients with CKD and 95 patients without CKD. Clopidogrel resistance was defined as a P2Y12 Reaction Units (PRU) value of >230 and/or % inhibition <20%.

RESULTS

The PRU value was 201.9±91.3 in the patients with CKD and 163.3±86.4 in the patients without CKD (p=0.035). The frequency of a PRU value of >230 was 44.1% (15 patients) among the patients with CKD and 17.9% (17 patients) among those without CKD (p=0.002). The percent inhibition was 29.9%±28.1% among the patients with CKD and 41.1%±28.0% among the patients without CKD (p=0.030). The frequency of % inhibition <20% was 47.1% (16 patients) among the patients with CKD and 26.3% (25 patients) among those without CKD (p=0.026).

CONCLUSION

The present study showed that noncardiogenic ischemic stroke patients with CKD have a greater frequency of clopidogrel resistance, thus suggesting that the response to clopidogrel is diminished in these patients.

Changes in antiplatelet use prior to incident ischaemic stroke over 7 years in a UK centre and the association with stroke subtype

BACKGROUND

guidelines have changed in relation to the indication of antiplatelet therapy for the primary and secondary prevention of stroke. Of interest is how the proportion of patients who had or had not taken antiplatelet agents prior to an incident stroke has changed over time, whether the type of antiplatelet agents used has altered and whether prior antiplatelet use is associated with a particular ischaemic stroke subtype.

METHODS

a stroke register was retrospectively examined. All ischaemic stroke patients admitted between January 2004 and March 2011 to a single University Hospital with a catchment population of ∼750,000 were included. We excluded those who were on anticoagulants prior to the ischaemic stroke.

RESULTS

a total of 4,307 ischaemic stroke patients [male 47.5%, mean age 77.6 (SD 11.7) years] were included. Of them, 54.7% (SD 2.2%) were not on any antiplatelet therapy prior to their incident stroke. The type and pattern of antiplatelet use prior to stroke did not change significantly during the 7-year study period, and there were no statistically significant differences between different ischaemic stroke subtypes with regards to prior antiplatelet use.

CONCLUSIONS

our findings highlight the requirement to improve currently available risk prediction scores as well as the potential clinical impact of antiplatelet resistance within the at risk population who are already on antiplatelets. These findings also indicate that targeting of multiple risk factors may be very important in stroke prevention.

Triple antiplatelet therapy with addition of cilostazol to aspirin and clopidogrel for Y-stent-assisted coil embolization of cerebral aneurysms

BACKGROUND

Dual antiplatelet therapy for stent-assisted coiling of cerebral aneurysms is essential to prevent thromboembolic complications. There is concern that Y-stent-assisted coiling may increase thromboembolic complications compared with coiling with a single stent. Several reports have demonstrated that cilostazol may improve clopidogrel responsiveness. We investigated whether triple antiplatelet therapy with addition of cilostazol to aspirin plus clopidogrel for Y-stents can prevent thromboembolic events.

METHODS

Between July 2010 and October 2012, we treated 40 consecutive aneurysms with coil embolization using Enterprise stents. At the peri-procedural period, dual antiplatelet agents (100 mg aspirin and 75 mg clopidogrel) were used for the single stent group (n = 36), and triple antiplatelet agents (addition of 200 mg cilostazol) were used for the Y-stent group (n = 4). We evaluated post-operative diffusion-weighted imaging (DWI) and any complications. We assessed the following for statistical analysis: age, sex, aneurysm location, shape, and size, neck size, size of parent vessels, and stent length.

RESULTS

We found two neurological peri-procedural complications: one transient ischemic attack and one infarction. Both complications belonged to the Y-stent group, which was a significant factor of thromboembolic events (P = 0.008). There were no other significant factors related to neurological complications or positive DWI. For subgroup analysis of the single stent group, stent length was significantly longer in positive DWI than negative DWI (P = 0.04). In the follow-up period of 20 ± 8.6 months, there were no symptomatic late complications in any patients.

CONCLUSIONS

Although the number of patients in the Y-stent group is small, this group had a significantly higher risk of thromboembolic complications. While our protocol of a routine dose of dual antiplatelet therapy may be sufficient for single stent therapy, our protocol of a routine dose of triple antiplatelet therapy for Y-stents may not prevent thromboembolic events. This suggests that evaluation of platelet function may be essential, especially for Y-stents.

Clopidogrel resistance is associated with thromboembolic complications in patients undergoing neurovascular stenting

BACKGROUND AND PURPOSE

Antiplatelet drug resistance has been associated with thromboembolic complications in patients after coronary stent placement. It has not been well-studied in patients who have neurovascular stent-placement procedures. This study aimed to analyze the relationship between antiplatelet drug resistance and neurovascular stent-placement complications.

MATERIALS AND METHODS

A prospective data base of all patients treated at our institution was used to identify patients with neurovascular stent-placement procedures. During a 4.5-year period, all patients undergoing neurovascular stent placement were evaluated for aspirin and clopidogrel resistance by using the VerifyNow assay. During an observational phase, all patients received 75 mg of clopidogrel and aspirin (group A). During the intervention phase (group B), patients were given additional clopidogrel on the basis of the clopidogrel resistance assay. We assessed the development of thromboembolic complications within 30 days of the procedure in patients who were resistant-versus-nonresistant to clopidogrel.

RESULTS

Of 96 patients who had neurovascular stent placement, 5.2% were resistant to aspirin and 36.5% were resistant to clopidogrel. Periprocedural thromboembolic complications were seen in 7 patients (7.3%). In a multivariate logistic regression model, clopidogrel resistance, higher diastolic blood pressure, and lack of statin use were significantly associated with periprocedural thromboembolic complication. There was a nonsignificant decrease in thromboembolic complications in patients whose clopidogrel dosage was tailored to the assay.

CONCLUSIONS

In our series, clopidogrel resistance was associated with increased periprocedural thromboembolic complications from neurovascular stent-placement procedures. Targeting the clopidogrel dose to platelet inhibition assays may improve clinical outcomes and requires further study.

Dual antiplatelet therapy clopidogrel with low-dose cilostazol intensifies platelet inhibition in patients with ischemic stroke

OBJECTIVE

We previously reported that the antiplatelet action is intensified with combined use of clopidogrel and cilostazol in ischemic stroke patients using the VerifyNow P2Y12 Assay. In this study, the relationship between the cilostazol dose and the platelet function achieved with combination therapy was investigated.

METHODS

The subjects included 231 patients with noncardiogenic ischemic stroke treated at our hospital (18 patients treated with a combination of clopidogrel (75 mg) and cilostazol (100 mg), 52 patients treated with a combination of clopidogrel (75 mg) and cilostazol (200 mg), 126 patients treated with clopidogrel (75 mg) alone and 35 patients treated with cilostazol (200 mg) alone). The platelet function achieved with 20 μM of adenosine diphosphate was measured using the VerifyNow P2Y12 Assay. Clopidogrel resistance was defined as P2Y12 Reaction Units (PRU) >230 and/or % inhibition <20%. Results The PRU was >230 in 32 patients (25.4%) receiving clopidogrel alone, one patient (5.6%) receiving combination therapy with cilostazol (100 mg) and one patient (1.9%) receiving combination therapy with cilostazol (200 mg). The rate of PRU >230 was significantly lower in both of the cilostazol combination groups than in the clopidogrel alone group. The percent inhibition was <20% in 41 patients (32.5%) receiving clopidogrel alone, one patient (5.6%) receiving a combination with cilostazol (100 mg) and one patient (1.9%) receiving a combination with cilostazol (200 mg). The rate of % inhibition <20% was significantly lower in both of the cilostazol combination groups than in the clopidogrel alone group.

CONCLUSION

Clopidogrel resistance was clearly decreased with combination clopidogrel (75 mg) and low-dose (100 mg) cilostazol therapy. The use of combination therapy with clopidogrel and low-dose cilostazol may be one means of overcoming clopidogrel resistance.

Laser-induced thrombus formation in mouse brain microvasculature: effect of clopidogrel

Antiplatelet drugs have been evaluated by measuring platelet aggregation ex vivo, but in vivo studies were scanty. The purpose of this study was to observe the effects of an antiplatelet agent (clopidogrel) on the process of laser-induced thrombus formation in mice using intravital fluorescence microscopy. C57 BL/6J mice (n = 19) were anesthetized using chloral hydrate. The head of each mouse was fixed with a head holder, and a cranial window was made in the parietal region. Platelets were labeled in vivo by intravenous administration of carboxyfluorescein diacetate succinimidyl ester. Clopidogrel (1 mg/kg, n = 6; 10 mg/kg, n = 6) was administered orally for 2 days before the experiment. Another seven mice were used as controls. Laser irradiation (1,000 mA, 9.8 mW, diode-pumped solid-state (DPSS) laser 532 nm) was directed for 4 s at pial arteries to induce thrombus formation. Labeled platelets and thrombus were observed continuously under fluorescence microscopy. We recorded the area of thrombus after 30 min and determined the complete occlusion rate. After laser irradiation to the pial artery, complete occlusion rate was significantly lower in the clopidogrel (10 mg/kg) group (16%, 4/25 vessels) than in the control group (60%, 12/20 vessels) or clopidogrel (1 mg/kg) group (55%, 11/20 vessels). Area of platelet thrombus at 30 min after laser irradiation was significantly smaller in the clopidogrel (10 mg/kg) group (209 ± 128 μm(2)) than in the control group (358 ± 256 μm(2)) or clopidogrel (1 mg/kg) group (355 ± 57 μm(2)). The apparatus which we developed is convenient for inducing thrombus formation by causing endothelial cell damage to the brain surface vasculature in small animals without damage of extravascular tissue. Clopidogrel significantly inhibited laser-induced thrombus formation in pial arteries of mice in a dose-dependent manner.

Secondary prevention of stroke: Pleiotropic effects of optimal oral pharmacotherapy

Stroke is a major cause of mortality and disability worldwide. During the past three decades, major advances have occurred in secondary prevention, which have demonstrated the broader potential for the prevention of stroke. Risk factors for stroke include previous stroke or transient ischemic attack, hypertension, high blood cholesterol and diabetes. Proven secondary prevention strategies are anti-platelet agents, antihypertensive drugs, statins and glycemic control. In the present review, we evaluated the secondary prevention of stroke in light of clinical studies and discuss new pleiotropic effects beyond the original effects and emerging clinical evidence, with a focus on the effect of optimal oral pharmacotherapy.

Antiplatelet resistance and thromboembolic complications in neurointerventional procedures

Antiplatelet resistance is emerging as a significant factor in effective secondary stroke prevention. Prevalence of aspirin and clopidogrel resistance is dependent upon laboratory test and remains contentious. Large studies in cardiovascular disease populations have demonstrated worse ischemic outcomes in patients with antiplatelet resistance, particularly in patients with coronary stents. Thromboembolism is a complication of neurointerventional procedures that leads to stroke. Stroke rates related to aneurysm coiling range from 2 to 10% and may be higher when considering silent ischemia. Stroke associated with carotid stenting is a major cause of morbidity. Antiplatelet use in the periprocedure setting varies among different centers. No guidelines exist for use of antiplatelet regimens in neurointerventional procedures. Incidence of stroke in patients post procedure may be partly explained by resistance to antiplatelet agents. Further research is required to establish the incidence of stroke in patients with antiplatelet resistance undergoing neurointerventional procedures.