Clinical importance of aspirin and clopidogrel resistance

Aspirin and clopidogrel resistance; a neglected gap in stroke and cardiovascular practice in Iran: a systematic review and meta-analysis

OBJECTIVE

Antiplatelet drugs, such as Aspirin and Clopidogrel (Plavix) are effective in the primary prevention of thromboembolic events. They are commonly used to reduce the risk of recurrence of thromboembolism. The body's hemostatic system responds differently to these drugs in different people. Resistance testing for aspirin and Clopidogrel is now recommended before starting antiplatelet therapy.

METHODS

A systematic literature search was performed on May 12, 2021, using the medical search engines PubMed, Scopus, and Web of Science, and the local databases SID and Magiran. After data extraction, a meta-analysis was performed using Comprehensive Meta-Analysis (CMA2) software. The I2 statistic was used to measure heterogeneity between estimates.

RESULTS

Among the 949 papers, Clopidogrel resistance was assessed in 136 patients and Aspirin resistance in 400 patients. The prevalence of Aspirin resistance was found to be 52.1% and the prevalence of Clopidogrel resistance was found to be 20.5%.

CONCLUSION

It seems that in Iran, the issue of Aspirin and Clopidogrel resistance is suboptimally addressed. This pattern could also occur in other developing countries in the Middle East region.

The role of clopidogrel resistance-related genetic and epigenetic factors in major adverse cardiovascular events among patients with acute coronary syndrome after percutaneous coronary intervention

Despite patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) and receiving clopidogrel therapy, some patients still experience major adverse cardiovascular events (MACEs). Clopidogrel resistance, which may be regulated by genetic and epigenetic factors, may play a role in MACEs. This study aimed to determine the association between genetic (CYP2C19 and P2Y12 polymorphisms) and epigenetic (DNA methylation of CYP2C19 and P2Y12 and miRNA-26a expression) factors and their effects on MACEs among post-PCI patients. Post-PCI patients who received a standard dosage of clopidogrel at Harapan Kita Hospital between September 2018 and June 2020 were included in this study. MACEs were observed in patients within 1 year after PCI. Platelet aggregation was assessed using light transmission aggregometry (LTA). DNA methylation of CYP2C19 and P2Y12 was assessed using the bisulfite conversion method. CYP2C19 and P2Y12 polymorphisms and miRNA-26a expression were evaluated using quantitative real-time polymerase chain reaction (qRT-PCR). Among a total of 201 subjects, 49.8% were clopidogrel-resistant, and 14.9% experienced MACEs within 1 year after PCI (death was 7.5%). Hypomethylation of CYP2C19 (p = 0.037) and miRNA-26a upregulation (p = 0.020) were associated with clopidogrel resistance. CYP2C19^*2/^*3 polymorphisms (p = 0.047) were associated with MACEs in 1 year. This study demonstrated that hypomethylation of CYP2C19 and miRNA-26a upregulation increased the risk of clopidogrel resistance in post-PCI patients, but there was no correlation between clopidogrel resistance and MACEs. However, CYP2C19^*2/^*3 polymorphisms were the factors that predicted MACEs within 1 year.

Mechanism of platelet activation and potential therapeutic effects of natural drugs

BACKGROUND

Cardiovascular disease is one of the most concerning chronic diseases in the world. Many studies have shown that platelet overactivation is a very important factor in the occurrence and development of cardiovascular diseases. At present, the widely used antiplatelet drugs have some defects, such as drug resistance and adverse reactions.

PURPOSE

The purpose of this article is to summarize the main mechanisms and pathways of platelet activation, the main targets of antiplatelet aggregation, and the antiplatelet aggregation components of natural drugs and their mechanisms of action to provide new research ideas for the development and application of antiplatelet drugs.

STUDY DESIGN AND METHODS

In this review, we systematically searched the PubMed, Google Scholar, Web of Science, and CNKI databases and selected studies based on predefined eligibility criteria. We then assessed their quality and extracted data.

RESULTS

ADP, AA, THR, AF, collagen, SDF-1α, and Ca²⁺ can induce platelet aggregation and trigger thrombosis. Natural drugs have a good inhibitory effect on platelet activation. More than 50 kinds of natural drugs and over 120 kinds of chemical compounds, including flavonoids, alkaloids, saponins, terpenoids, coumarins, and organic acids, have significantly inhibited platelet activation activity. The MAPK pathway, cGMP-PKG pathway, cAMP-PKA pathway, PI3K-AKT pathway, PTK pathway, PLC pathway, and AA pathway are the main mechanisms and pathways of platelet activation.

CONCLUSION

Natural drugs and their active ingredients have shown good activity and application prospects in anti-platelet aggregation. We hope that this review provides new research ideas for the development and application of antiplatelet drugs.

Preparation of injectable clopidogrel loaded submicron emulsion for enhancing physicochemical stability and anti-thrombotic efficacy

Due to the superior safety and therapeutic efficacy, clopidogrel (CLP) has been widely used to prevent postoperative thrombosis. However, limitations of delayed absorption and metabolic activation of clopidogrel after oral administration hinder its clinic use for acute thrombosis treatment in percutaneous coronary intervention (PCI). Although clopidogrel aqueous injection systems were designed and developed, chemical instability under physiological condition or vascular irritation remains to be solved. In this study, we aim to prepare an injectable clopidogrel loaded submicron emulsion to overcome the drawbacks of conventional clopidogrel aqueous formulation and improve the antiplatelet aggregation effects. Results showed that this delivery system exerted inspiring features including uniform particle size, higher drug loading capacity and sustained drug release behavior. It can dramatically upgrade the formulation stability and prevent the drug degradation under sterilization or higher pH environments. No remarkable droplet size increase or drug content decrease was observed during storage. Compared to CLP tablet, the peak drug concentration (C_max) and area under the curve (AUC) of CLP emulsion increased by 12.01-fold and 4.69-fold, respectively. Most importantly, it exerted excellent in vivo anti-thrombotic effect on numerous designed animal models. Conclusively, submicron emulsion is a promising delivery system for improving clopidogrel stability and anti-thrombotic efficacy.

Prevalence and Effect of Cerebral Small Vessel Disease in Stroke Patients With Aspirin Treatment Failure-A Hospital-Based Stroke Secondary Prevention Registry

Background: Breakthrough strokes during treatment with aspirin, termed clinical aspirin treatment failure (ATF), is common in clinical practice. The burden of cerebral small vessel disease (SVD) is associated with an increased recurrent ischemic stroke risk. However, the association between SVD and ATF remains unclear. This study investigated the prevalence and clinical characteristics of SVD in stroke patients with ATF.

Methods: Data from a prospective, and multicenter stroke with ATF registry established in 2018 in Taiwan were used, and 300 patients who developed ischemic stroke concurrent with regular use of aspirin were enrolled. White matter lesions (WMLs) and cerebral microbleeds (CMBs) were identified using the Fazekas scale and Microbleed Anatomical Rating Scale, respectively. Demographic data, cardiovascular comorbidities, and index stroke characteristics of patients with different WML and CMB severities were compared. Logistic regression analyses were performed to explore the factors independently associated with outcomes after ATF.

Results: The mean patient age was 69.5 ± 11.8 years, and 70.0% of patients were men. Among all patients, periventricular WML (PVWML), deep WML (DWML), and CMB prevalence was 93.3, 90.0, and 52.5%, respectively. Furthermore, 46.0% of the index strokes were small vessel occlusions. Severe PVWMLs and DWMLs were significantly associated with high CMB burdens. Patients with moderate-to-severe PVWMLs and DWMLs were significantly older and had higher cardiovascular comorbidity prevalence than did patients with no or mild WMLs. Moreover, patients with favorable outcomes exhibited significantly low prevalence of severe PVWMLs (p = 0.001) and DWMLs (p = 0.001). After logistic regression was applied, severe WMLs predicted less favorable outcomes independently, compared with those with no to moderate PVWMLs and DWMLs [odds ratio (OR), 0.47; 95% confidence interval (CI), 0.25–0.87 for severe PVWMLs; OR, 0.40; 95% CI, 0.21–0.79 for severe DWMLs].

Conclusions: SVD is common in stroke patients with ATF. PVWMLs and DWMLs are independently associated with functional outcomes in stroke patients with ATF. The burden of SVD should be considered in future antiplatelet strategies for stroke patients after ATF.

Safety and Efficacy of Prasugrel in Elderly/Low Body Weight Japanese Patients with Ischemic Stroke: Randomized PRASTRO-II

INTRODUCTION

The safety of prasugrel in elderly and/or low body weight Japanese patients with ischemic stroke who have a relatively high bleeding risk with antiplatelet therapy remains unknown.

OBJECTIVE

We aimed to investigate the safety and efficacy of long-term prasugrel monotherapy for stroke prevention compared with clopidogrel in elderly and/or low body weight Japanese patients with non-cardioembolic ischemic stroke.

METHODS

In this randomized, double-blind, comparative, phase III study, elderly (age ≥75 years) and/or low body weight (≤50 kg) Japanese patients with a previous history of non-cardioembolic ischemic stroke were assigned to a prasugrel 3.75 mg (PRA3.75) group, a prasugrel 2.5 mg (PRA2.5) group, or a clopidogrel 50 mg (CLO50) group and followed up for 48 weeks. The primary safety endpoint was the combined incidence of primary safety events, defined as life-threatening, major, and other clinically relevant bleeding. The efficacy endpoint was a composite of ischemic stroke, myocardial infarction, and death from other vascular causes.

RESULTS

A total of 654 patients (age 76.4 ± 7.3 years, body weight 55.6 ± 9.3 kg, women 43.9%) from 74 medical institutions within Japan were enrolled. The combined incidence (95% CI) of primary safety events was 4.2% (1.9-7.8%), 1.9% (0.5-4.7%), and 3.6% (1.6-6.9%) in the PRA3.75 group (n = 216), PRA2.5 group (n = 215), and CLO50 group (n = 223), respectively (hazard ratios [HR] PRA3.75/CLO50, 1.13 [0.44-2.93]; PRA2.5/CLO50, 0.51 [0.15-1.69]). The incidences of bleeding leading to treatment discontinuation (95% CI) were 2.3% (0.8-5.3%), 0.9% (0.1-3.3%), and 2.2% (0.7-5.2%) in the PRA3.75, PRA2.5, and CLO50 groups, respectively (HRs PRA3.75/CLO50, 1.01 [0.29-3.48]; PRA2.5/CLO50, 0.41 [0.08-2.12]). There was no significant difference in all bleeding events between groups. The incidence of ischemic stroke, myocardial infarction, and death from other vascular causes was lower, but not significantly so, in patients treated with prasugrel than in patients treated with clopidogrel: PRA3.75, 0.0% (0/216); PRA2.5, 3.3% (7/215); and CLO50, 3.6% (8/223; HRs PRA3.75/CLO50, 0.00 [0.00-0.00]; PRA2.5/CLO50, 0.90 [0.32-2.47]).

CONCLUSIONS

Elderly and/or low body weight -Japanese patients with previous non-cardioembolic ischemic stroke who received PRA3.75 showed similar results in terms of primary safety endpoint, and a numerically lower incidence of ischemic stroke, myocardial infarction, and death from other vascular causes, compared with those who received CLO50.

Pharmacogenetic and clinical predictors of response to clopidogrel plus aspirin after acute coronary syndrome in Egyptians

OBJECTIVES

Dual antiplatelet therapy (DAPT) with aspirin and clopidogrel reduces the risk for recurrent cardiovascular events after acute coronary syndrome (ACS). However, there is significant variation in response to DAPT that may be influenced by both genetic and nongenetic factors. This study aimed to assess the effect of genetic polymorphisms in PON-1, PEAR-1, P2Y12, CES1, and CYP2C19, along with clinical, demographic, and social factors, on variation in response to DAPT in Egyptians.

PARTICIPANTS AND METHODS

This study included 230 Egyptians treated with clopidogrel 75 mg/day and aspirin 81 mg/day for at least 12 months following their first ACS. Simple and multivariable logistic regression analyses were carried out to identify factors associated with major adverse cardiovascular events (MACE), defined as the occurrence of recurrent ACS, ischemic stroke, stent-related revascularization, or death, in clopidogrel-treated participants.

RESULTS

Using multivariable logistic regression analysis, the CYP2C19*2 polymorphism was the only genetic predictor of MACE [odds ratio (OR): 2.23, 95% confidence interval (CI): 1.15-4.33, P=0.01]. In addition, proton pump inhibitor use (OR: 4.77, 95% CI: 1.47-15.54, P=0.009) and diabetes (OR: 1.83, 95% CI: 1.03-3.26, P=0.03) were associated with higher cardiovascular risk, whereas statin use was associated with lower risk (OR: 0.43, 95% CI: 0.25-0.76, P=0.003). The contribution of these four genetic and nongenetic factors explained 19% of the variability in risk for MACE in Egyptians treated with DAPT.

CONCLUSION

These results highlight that CYP2C19*2, along with diabetes, and use of proton pump inhibitor and statin are important factors jointly associated with variability in clinical response to DAPT following ACS in Egyptians.

Prospective Determination of Aspirin Sensitivity in Patients Resistant to Low Dose Aspirin: A Proof of Concept Study

This study tested the capability of an assay to predict aspirin response and reduce ischemic events, and healthcare costs, and delays to optimal treatment. Patients who needed aspirin in the course of normal medical care were included. Patients were excluded if they had disorders affecting platelet function, alcohol use within 24 hours of a test, or NSAID use. Dose escalation of chewable aspirin from 81 mg, to 162 mg, to 325 mg daily occurred based on the results of whole blood impedance aggregation testing to the agonists, collagen (1ug/mL, 5 ug/mL) and arachidonate (0.5 mM) after 10-14 days of treatment. The experimental in vitro test was conducted in triplicate by performing aggregometry on samples spiked to a concentration of 10 uM of aspirin in 0.05% dimethyl sulfoxide. Of the 36 patients who were compliant 16 were found to be resistant to the antiplatelet effects of 81 mg daily aspirin. Nine of these patients were predicted to stay resistant despite dose increase. Once tested at higher doses, ten remained resistant. Seven of the 16 patients were predicted to become sensitive to a higher dose while six actually did. Predicted response to increased doses of aspirin was in good agreement with actual response. Sensitivity of the assay was 83% and specificity was 80%. Results are promising and indicate that it is possible to predict, with reasonable accuracy, if a patient will have an adequate platelet response to aspirin or if the patient will never respond to aspirin necessitating an alternative antiplatelet regimen. Larger, multisite studies are inevitably needed.

On-treatment platelet reactivity in peripheral and coronary blood in patients undergoing primary PCI for ST-segment elevation myocardial infarction (STEMI)

Dual antiplatelet therapy is recommended in patients undergoing primary percutaneous coronary intervention (p-PCI) for ST-segment elevation myocardial infarction (STEMI). Pre-analytical variables may influence platelet function analysis results. Our aim was to evaluate the on-treatment platelet reactivity in peripheral artery vs coronary blood in patients with STEMI. We enrolled one hundred and nine patients who consecutively underwent p-PCI at Cardiology Unit of Padua University Hospital between June 2014 and June 2015. Before the procedure, all patients received intravenous aspirin 250 mg and either of the thienopyridines; clopidogrel 600 mg, prasugrel 60 mg or ticagrelor 180 mg. ASPI-test and ADP-test using multiple electrode aggregometry (MEA) were performed in samples collected from both a peripheral artery and the culprit coronary artery. 'Low responders' were patients with an ASPI-test or ADP-test value greater than or equal to a pre-established normal range. No significant differences were observed in ASPI-test values between peripheral (19 (median) [3-49 (10-90 percentiles)] U) vs coronary (12 [1-40] U, p = .06) blood and in ADP-test (40 [14-82] U vs 33 [7-79] U, p =.68) blood. In peripheral blood, fifteen (14%) patients were 'low aspirin' and forty-one (38%) 'low thienopyridines' responders. The prevalence of 'low clopidogrel' responders was higher (45%) than prasugrel (36%) and ticagrelor (33%). Similar results were observed in coronary blood. In patients undergoing p-PCI for STEMI, MEA platelet function observed in coronary arteries was consistent with peripheral artery blood's independently of the antiplatelet drug used. The clinical significance of peripheral and coronary on-aspirin/thienopyridines platelet reactivity needs further clarification.

Role of Dipyrone in the High On-Treatment Platelet Reactivity amongst Acetylsalicylic Acid-Treated Patients Undergoing Peripheral Artery Revascularisation

OBJECTIVE

To evaluate the effects of dipyrone on sensitivity to aspirin (acetylsalicylic acid [ASA]) in patients who underwent peripheral artery vascular reconstruction.

SUBJECTS AND METHODS

Impedance aggregometry and light transmission aggregometry were used to determine the effects of dipyrone on ASA treatment in 21 patients. Blood samples were drawn in a 7-day period after the surgery. The cut-off value for high on-treatment platelet reactivity (HTPR) was set at < 65% of aggregation inhibition for impedance aggregometry. For light transmission aggregometry the cut-off value for arachidonic acid-induced aggregation was set at > 20% of aggregating platelets, and the cut-off value for epinephrine-induced aggregation was > 44% of aggregating platelets. The cut-off value for each method was derived from a large number of patients treated with a daily dose of 100 mg of ASA.

RESULTS

We found HTPR in 14 (67%) of the 21 patients. None had primary resistance to ASA, i.e., after the addition of ASA in vitro all samples showed antiplatelet efficacy. Regression analysis showed a possible correlation between lower efficacy of ASA treatment and higher daily doses of dipyrone (p = 0.005 for impedance aggregometry, p = 0.04 for light transmission aggregometry), higher platelet count (p = 0.005 for impedance aggregometry), and shorter time from surgery (p = 0.03 for impedance aggregometry).

CONCLUSION

HTPR occurs in 67% of ASA-treated patients after lower limb vascular surgery. The occurrence of HTPR correlates with the daily dose of dipyrone. Therefore, dipyrone should not be used as a postoperative analgesic in ASA-treated patients after peripheral artery revascularisation due to its influence on the effectiveness of ASA.

Capture of anti-coagulant active ingredients from Moutan Cortex by platelet immobilized chromatography and evaluation of anticoagulant activity in rats

Moutan Cortex (MC) is a well-known Chinese medicine for promoting blood circulation and relieving blood stasis. The intent of this study was to evaluate the anticoagulant activity of MC and capture the bioactive compounds by platelet immobilized chromatography. Sprague Dawley (SD) rats were randomly divided into the control group, aspirin group and MC group (1.25, 2.5, 5g/kg/d). Coagulation system and platelet activity were investigated to evaluate the anti-coagulation effect of MC. The effective components of MC were captured by platelet immobilized chromatography. High performance liquid chromatography-diode array detection (HPLC-DAD) and liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) analysis were used to identify the binding ingredients. Meanwhile, the efficacy of active ingredients was assessed through inhibiting platelet adhesion and regulating the expression of platelet related proteins. Principal findings showed that 2.5g/kg/d MC significantly prolonged thrombin time (TT) and 5g/kg/d MC significantly prolonged TT and prothrombin time (PT). MC exhibited an inhibitory potency on adenosine diphosphate-induced platelet aggregation. Four active compounds were found by platelet immobilized chromatography including oxypaeoniflorin, tetragalloylglucose, pentagalloyl glucose and benzoylpaeoniflorin; these active ingredients significantly up-regulated the expression of hsp-70 and coronin-1B, reduced the ratio of adhesion platelets. These results suggest that MC markedly promoted blood circulation and relieved blood stasis by inhibiting platelet activation, as an anti-coagulant, elucidating its potential capacity to treat cardiovascular diseases.

High prevalence of aspirin resistance in elderly patients with cardiovascular disease and metabolic syndrome

Background

Metabolic syndrome is known to be a prothrombotic state. We undertook this study to examine a hypothesis that aspirin resistance may be associated with metabolic syndrome, and to assess other potential determinants of aspirin resistance in patients with cardiovascular disease (CVD).

Methods

A total of 469 elderly patients with CVD were recruited. One hundred and seventy-two patients with metabolic syndrome and 297 without metabolic syndrome (control group) received daily aspirin therapy (≥ 75 mg) over one month. Platelet aggregation was measured by light transmission aggregometry (LTA). Aspirin resistance was defined as ≥ 20% arachidonic acid (AA)- and ≥ 70% adenosine diphosphate (ADP)-induced aggregation according to LTA. Aspirin semi-responders were defined as meeting one (but not both) of these criteria.

Results

By LTA, 38 of 469 (8.1%) patients were aspirin resistant. The prevalence of aspirin resistance was higher in the metabolic syndrome group compared with the control group [11.6 % vs. 6.6%, odds ratio (OR) = 2.039; 95% confidence interval (CI): 1.047–3.973]. In the multivariate logistic regression analysis, metabolic syndrome (OR = 4.951, 95% CI: 1.440–17.019, P = 0.011) was a significant risk factor for aspirin resistance.

Conclusions

A significant number of patients with CVD and metabolic syndrome are resistant to aspirin therapy. This might further increase the risk of cardiovascular morbidity and mortality in these patients.

Laboratory-Based Markers as Predictors of Brain Infarction During Carotid Stenting: a Prospective Study

AIM

New ischemic lesions in the brain can be detected in approximately 50% of patients undergoing carotid artery stenting (CAS). We wished to discover the laboratory-based predictors of new infarctions in the brain after CAS.

METHODS

All consecutive patients with internal carotid artery stenosis of ≥70% with indication for CAS were enrolled in a prospective study for 16 months. All patients used dual antiplatelet therapy for ≥7 days before CAS. Neurologic examination and magnetic resonance imaging (MRI) of the brain were undertaken before and at 24 h after CAS. Samples of venous blood were collected at ＜24 h before CAS for the evaluation of hematology, reticulocytes, coagulation markers (PT, APTT, Fbg, Clauss), vWF antigen, PAI-1 activity, PAI-1 polymorphism 4G/5G, and the multiplate (aspirin and clopidogrel) resistance test. Blood samples for the assessment of anti-Xa activity were collected during CAS. Differences in the values of laboratory markers between patients with and without new ischemic lesions of the brain on control MRI were evaluated.

RESULTS

The cohort comprised 81 patients (53 males; mean age, 67.3±7.2 years). New ischemic infarctions in the brain on control MRI were found in 46 (56.8%) patients. Three of seven patients with resistance to aspirin or clopidogrel had a new ischemic infarction in the brain. No significant differences for particular markers were found between patients with and without an ischemic lesion in the brain.

CONCLUSION

A high risk of a new ischemic infarction in the brain was detected in patients undergoing CAS, but a laboratory-based predictor of such an infarction could not be identified.

Anti-platelet Therapy Resistance - Concept, Mechanisms and Platelet Function Tests in Intensive Care Facilities

It is well known that critically ill patients require special attention and additional consideration during their treatment and management. The multiple systems and organ dysfunctions, typical of the critical patient, often results in different patterns of enteral absorption in these patients. Anti-platelet drugs are the cornerstone in treating patients with coronary and cerebrovascular disease. Dual anti-platelet therapy with aspirin and clopidogrel is the treatment of choice in patients undergoing elective percutaneous coronary interventions and is still widely used in patients with acute coronary syndromes. However, despite the use of dual anti-platelet therapy, some patients continue to experience cardiovascular ischemic events. Recurrence of ischemic events is partly attributed to the fact that some patients have poor inhibition of platelet reactivity despite treatment. These patients are considered low- or non-responders to therapy. The underlying mechanisms leading to resistance are not yet fully elucidated and are probably multifactorial, cellular, genetic and clinical factors being implicated. Several methods have been developed to asses platelet function and can be used to identify patients with persistent platelet reactivity, which have an increased risk of thrombosis. In this paper, the concept of anti-platelet therapy resistance, the underlying mechanisms and the methods used to identify patients with low responsiveness to anti-platelet therapy will be highlighted with a focus on aspirin and clopidogrel therapy and addressing especially critically ill patients.

[Clopidogrel resistance in cerebrovascular disease -- results of one-year follow-up]

INTRODUCTION

In an earlier study the authors reported short-term benefits of clopidogrel treatment in patients with cerebrovascular disease.

AIM

The aim of the authors was to analyze findings during a 12-month follow-up period.

METHOD

100 patients with a history of acute stroke or transient ischaemic attack have been included in the study. The efficacy of the therapy was assessed 7 and 28 days as well as 3, 6 and 12 months after initiation of medical therapy. Patients were divided into two parts (clopidogrel responder and resistant) based on their initial laboratory findings. Risk profiles, medical therapy, laboratory parameters and vascular events were compared between the two patient groups.

RESULTS

After 7 days of treatment, clopidogrel seemed to be ineffective in 11 patients (11%). Strong, clinically significant correlations were found among blood pressure values, blood glucose and lipid parameters, serum C-reactive protein levels and platelet aggregation levels. An aggressive secondary preventive therapy resulted in a decrease of clopidogrel resistance and improvement in laboratory parameters. Patients who were clopidogrel resistant at baseline had significantly higher rate of vascular events compared to those who were clopidogrel responders (18.1 vs. 4.5%, p<0.01), although clopidogrel resistance was not an independent risk factor of unfavourable vascular outcome using a multivariate analysis. No adverse events or hemorrhagic complications were observed.

CONCLUSIONS

Clopidogrel resistance and unfavourable outcome seems to be associated with "classical" risk factors underlying the importance of aggressive secondary prevention.

Searching for factors associated with resistance to acetylsalicylic acid used for secondary prevention of stroke

INTRODUCTION

The aim of the study was to evaluate the prevalence of resistance to acetylsalicylic acid (ASA), used for secondary prevention of stroke, including the assessment of risk factors associated with the lack of ASA anti-aggregatory action.

MATERIAL AND METHODS

Patients after a transient ischaemic attack (TIA) or ischaemic stroke in the acute (n = 111) and chronic phase (n = 87) were enrolled in the study. The assessment of platelet function was performed by whole blood impedance aggregometry using a multi-channel platelet function analyser (Multiplate).

RESULTS

A proper response to ASA was found in 121 patients (61.1%) (ASA responders), a partial response to ASA in 59 patients (29.8%) (ASA partial responders), and ASA resistance in 18 patients (9.1%) (ASA non-responders). Acetylsalicylic acid resistance was observed more frequently in the chronic phase. The mean low-density lipoprotein (LDL) concentration was higher in ASA non-responders (p = 0.02). The mean heart rate (p = 0.03) and the mean haematocrit (p = 0.03) were higher in the group of ASA partial responders and ASA non-responders. Angiotensin II receptor antagonists were more often used in the group of ASA partial responders and ASA non-responders (p = 0.04). Diuretics were more rarely used by ASA non-responders, whereas fibrates were more rarely used by ASA partial responders.

CONCLUSIONS

The method enabled the detection of ASA resistance in some patients with cerebrovascular disease. The study revealed some possible risk factors of ASA resistance: long ASA therapy, increased heart rate, higher LDL concentration, and higher haematocrit value. The relationship between the effect of ASA and other medications (angiotensin II receptor blockers, fibrates, diuretics) requires further study. Platelet function monitoring should be considered in patients at a greater risk of ASA resistance.

Thromboembolic events associated with single balloon-, double balloon-, and stent-assisted coil embolization of asymptomatic unruptured cerebral aneurysms: evaluation with diffusion-weighted MR imaging

INTRODUCTION

The introduction of the balloon remodeling and stent-assisted technique has revolutionized the approach to coil embolization for wide-neck aneurysms. The purpose of this study was to determine the frequency of thromboembolic events associated with single balloon-assisted, double balloon-assisted, and stent-assisted coil embolization for asymptomatic unruptured aneurysms.

METHODS

A retrospective review was undertaken by 119 patients undergoing coiling with an adjunctive technique for unruptured saccular aneurysms (64 single balloon, 12 double balloon, 43 stent assisted). All underwent diffusion-weighted imaging (DWI) within 24 h after the procedure.

RESULTS

DWI showed hyperintense lesions in 48 (40%) patients, and ten (21%) of these patients incurred neurological deterioration (permanent, two; transient, eight). Hyperintense lesions were detected significantly more often in procedures with the double balloon-assisted technique (7/12, 58%) than with the single balloon-assisted technique (16/64, 25%, p = 0.05). Occurrence of new lesions was significantly higher with the use of stent-assisted technique (25/43, 58%) than with the single balloon-assisted technique (p = 0.001). Symptomatic ischemic rates were similar between the three groups. The increased number of microcatheters was significantly related to the DWI abnormalities (two microcatheters, 15/63 (23.8%); three microcatheters, 20/41 (48.8%) (p = 0.008); four microcatheters, 12/15 (80%) (p = 0.001)).

CONCLUSION

Thromboembolic events detected on DWI related to coil embolization for unruptured aneurysms are relatively common, especially in association with the double balloon-assisted and stent-assisted techniques. Furthermore, the number of microcatheters is highly correlated with DWI abnormalities. The high rate of thromboembolic events suggests the need for evaluation of platelet reactivity and the addition or change of antiplatelet agents.

Platelet proteomics and its advanced application for research of blood stasis syndrome and activated blood circulation herbs of Chinese medicine

The development of novel and efficient antiplatelet agents that have few adverse effects and methods that improve antiplatelet resistance has long been the focus of international research on the prevention and treatment of cardiovascular and cerebrovascular diseases. Recent advances in platelet proteomics have provided a technology platform for high-quality research of platelet pathophysiology and the development of new antiplatelet drugs. The study of blood stasis syndrome (BSS) and activated blood circulation of traditional Chinese medicine (TCM) is one of the most active fields where the integration of TCM and western medicine in China has been successful. Activated blood circulation herbs (ABC herbs) of Chinese medicine are often used in the treatment of BSS. Most ABC herbs have antiplatelet and anti-atherosclerosis activity, but knowledge about their targets is lacking. Coronary heart disease (CHD), BSS, and platelet activation are closely related. By screening and identifying activated platelet proteins that are differentially expressed in BSS of CHD, platelet proteomics has helped researchers interpret the antiplatelet mechanism of action of ABC herbs and provided many potential biomarkers for BSS that could be used to evaluate the clinical curative effect of new antiplatelet drugs. In this article the progress of platelet proteomics and its advanced application for research of BSS and ABC herbs of Chinese medicine are reviewed.

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.

Genetic variation in PEAR1 is associated with platelet aggregation and cardiovascular outcomes

BACKGROUND- Aspirin or dual antiplatelet therapy with aspirin and clopidogrel is a standard therapy for patients who are at increased risk for cardiovascular events. However, the genetic determinants of variable response to aspirin (alone and in combination with clopidogrel) are not known. METHODS AND RESULTS- We measured ex vivo platelet aggregation before and after dual antiplatelet therapy in individuals (n=565) from the Pharmacogenomics of Anti-Platelet Intervention (PAPI) Study and conducted a genome-wide association study of drug response. Significant findings were extended by examining genotype and cardiovascular outcomes in 2 independent aspirin-treated cohorts: 227 percutaneous coronary intervention patients and 1000 patients of the International Verapamil SR/Trandolapril Study (INVEST) Genetic Substudy (INVEST-GENES). Results from the genome-wide association study revealed a strong association between single-nucleotide polymorphisms on chromosome 1q23 and post-dual antiplatelet therapyplatelet aggregation. Further genotyping revealed rs12041331 in the platelet endothelial aggregation receptor-1 (PEAR1) gene to be most strongly associated with dual antiplatelet therapy response (P=7.66×10(-9)). In white and black patients undergoing percutaneous coronary intervention, A-allele carriers of rs12041331 were more likely to experience a cardiovascular event or death compared with GG homozygotes (hazard ratio, 2.62; 95% confidence interval, 0.96-7.10; P=0.059; and hazard ratio, 3.97; 95% confidence interval, 1.10-14.31; P=0.035, respectively). In aspirin-treated INVEST-GENES patients, rs12041331 A-allele carriers had significantly increased risk of myocardial infarction compared with GG homozygotes (odds ratio, 2.03; 95% confidence interval, 1.01-4.09; P=0.048). CONCLUSION- Common genetic variation in PEAR1 may be a determinant of platelet response and cardiovascular events in patients on aspirin alone or in combination with clopidogrel. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00799396 and NCT00370045.

Superficial temporal artery-middle cerebral artery anastomosis for internal carotid artery occlusion by subacute in-stent thrombosis after carotid artery stenting

Alternative to carotid endarterectomy, carotid artery stenting (CAS) can be performed for symptomatic severe stenosis of internal carotid artery, especially for high-risk patients. Among several complications after CAS, subacute in-stent thrombosis is rare but important, because patient's condition can deteriorate rapidly. Subacute in-stent thrombosis with carotid artery occlusion can be managed by superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis. We report two cases of STA-MCA anastomosis for internal carotid artery occlusion by subacute in-stent thrombosis after CAS.

Frequency, risk factors, prognosis, and genetic polymorphism of the cyclooxygenase-1 gene for aspirin resistance in elderly Chinese patients with cardiovascular disease

BACKGROUND

Cardiovascular disease (CVD) is an important cause of mortality in elderly patients worldwide. Aspirin resistance has been well reported in CVD.

OBJECTIVE

The frequency, risk factors, prognosis, and genetic polymorphism of the cyclooxygenase-1 (COX-1) gene for aspirin resistance have not been reported in elderly patients with CVD. We therefore undertook this study to evaluate these associations among elderly Chinese patients with CVD.

METHODS

Four hundred thirty-one elderly Chinese patients with CVD receiving daily aspirin therapy (≥75 mg) over 1 month were enrolled. Platelet aggregation was measured by light transmission aggregometry (LTA) and thromboelastography platelet mapping assay (TEG) using arachidonic acid (AA) as a stimulus. The median follow-up was 1.8 years.

RESULTS

After the median follow-up, aspirin-resistant patients were at an increased risk of the composite endpoint compared to nonresistant patients by LTAAA + TEGAA (23.7 vs. 9.2%, p = 0.025). Additionally, Cox proportional hazards regression modeling demonstrated that aspirin resistance and cerebrovascular disease were associated with major adverse long-term outcomes (HR for aspirin resistance = 2.31, 95% CI 1.11-4.81, p = 0.026). The variant G-allele of COX-1 rs1330344 (-1676 A/G) significantly increased the risk of aspirin resistance defined by LTAAA + TEGAA (OR = 1.82, 95% CI 1.13- 2.92, p = 0.01).

CONCLUSIONS

Aspirin resistance, evaluated by LTAAA + TEGAA, is associated with an increased risk of adverse clinical events in elderly Chinese patients with CVD. The variant G-allele of COX-1 rs1330344 is significantly associated with aspirin resistance defined by LTAAA + TEGAA.

The prevalence, risk factors and prognosis of aspirin resistance in elderly male patients with cardiovascular disease

AIM

Aspirin resistance is recognized in different population. However, the prevalence and clinical events of aspirin resistance in elderly male patients with cardiovascular disease (CVD) have not been reported.

METHODS

We enrolled 304 elderly male patients with CVD receiving daily aspirin therapy (≥ 75 mg) more than 1 month. Platelet aggregation was measured by light transmission aggregometry (LTA) and thrombelastography platelet mapping assay (TEG). The median follow-up time was 1.8 years. The primary outcome was the composite of death, myocardial infarction, unstable angina, stroke and transient ischemic attack.

RESULTS

By LTA, 25 (8.2%) of elderly patients were aspirin resistant and 106 (34.9%) patients were semiresponders. According to TEG, 62 patients (20.4%) were found to be resistant to aspirin therapy. Of the 62 patients with aspirin resistance by TEG, 21 patients were aspirin resistant by LTA. Twenty-two of the 106 semiresponders by LTA were aspirin resistant by TEG. Patients with aspirin resistance or aspirin semiresponders were at increased risk of the composite outcome compared with aspirin-sensitive patients by LTA (18.3% vs 9.8%, Hazard ratio (HR) = 1.864, 95% confidence interval (CI): 1.046-3.324 p = 0.039). However, aspirin resistance was not associated with an increased risk of clinical vascular events compared to aspirin-sensitive patients by TEG (17.7% vs 10.9%, p = 0.452). In addition, Cox proportional hazard regression modeling demonstrated that aspirin resistance or semiresponders (HR = 3.050, 95% CI: 1.464-6.354, p = 0.003) and diabetes (HR = 2.055, 95% CI: 1.060-3.981, p = 0.033) were associated with major adverse long-term outcomes.

CONCLUSIONS

Aspirin resistance or semiresponders, defined by LTA, are associated with an increased risk of adverse clinical events in elderly male patients with CVD.

Genetic Polymorphisms of HO-1 and COX-1 Are Associated With Aspirin Resistance Defined by Light Transmittance Aggregation in Chinese Han Patients

Background:

Cyclooxygenase 1 ( COX-1), COX-2, and HO-1 are involved in the process of aspirin’s effect. The genetic susceptibility of these enzymes to aspirin resistance (AR) is unclear. Methods: A total of 431 patients took aspirin. Using arachidonic acid-induced light transmittance aggregation combined with adenosine diphosphate-induced light transmittance aggregation, 36 participants served for AR, 164 participants for semi-AR, and 231 participants for aspirin sensitivity (AS). The AR with 9 single-nucleotide polymorphism in COX-1, COX-2, and HO-1 genes was investigated.

Results:

COX-1 rs1330344 (−1676A>G) is associated with AR. G-Allele carriers significantly increased the risk of AR. For patients with AS as control, P is .02 (odds ratio [OR] = 1.77, confidence interval [CI]: 1.07-2.92). For patients with semi-AR as control, P is .05. HO-1 rs2071746 (−413A>T) is associated with AR. T-Allele carriers significantly increased the risk of AR. For patients with AS as control, P is .04 (OR = 1.70, CI: 1.02-2.79). For patients with semi-AR as control, P is .05 (OR = 1.68, CI: 1.00-2.80).

Conclusion:

rs2071746 in HO-1 gene, rs1330344 in COX-1 gene contribute to AR.

Platelet function profile post-clopidogrel therapy in patients with type 2 diabetes undergoing coronary stent implantation

Platelet dysfunction contributes to the increased risk of thromboischemic complications after percutaneous coronary intervention (PCI), particularly in type 2 diabetes. Little is known about the effects of glycemic control on platelet reactivity. We assessed adenosine diphosphate-induced platelet aggregation and flow cytometric expression of P-selectin in 90 patients (56 diabetic and 34 nondiabetic patients) undergoing coronary stent implantation after administration of clopidogrel as a potential predictor of poststent complications and its relation to glycemic control. Posttreatment platelet reactivity was significantly elevated in diabetic compared with nondiabetic participants and was associated with smoking, hypercholesterolemia, overweight, and cardiovascular ischemic events. A linear relationship was found between hemoglobin A1c in diabetic patients and platelet reactivity. Both methods (standard aggregometry and P-selectin expression) used for assessment of platelet function were positively correlated. Low responsiveness to clopidogrel detected by posttreatment platelet reactivity is a risk factor for ischemic events after PCI in diabetic patients.

Paraoxonase 1 (PON1) gene variants are not associated with clopidogrel response

A common functional variant in paraoxonase 1 (PON1), Q192R, was recently reported to be a major determinant of clopidogrel response. This variant was genotyped in 566 participants of the Amish Pharmacogenomics of Anti-Platelet Intervention (PAPI) study and in 227 percutaneous coronary intervention (PCI) patients. Serum paraoxonase activity was measured in a subset of 79 PAPI participants. PON1 Q192R was not associated with pre- or post-clopidogrel platelet aggregation in the PAPI study (P = 0.16 and P = 0.21, respectively) or the PCI cohort (P = 0.47 and P = 0.91, respectively). The Q192 allele was not associated with cardiovascular events (hazard ratio (HR) 0.46, 95% confidence interval (CI) 0.20-1.06; P = 0.07). No correlation was observed between paraoxonase activity and post-clopidogrel platelet aggregation (r(2) < 0.01, P = 0.78). None of 49 additional PON1 variants evaluated was associated with post-clopidogrel platelet aggregation. These findings do not support a role for PON1 as a determinant of clopidogrel response.

Significance of clopidogrel resistance related to the stent-assisted angioplasty in patients with atherosclerotic cerebrovascular disease

OBJECTIVE

To evaluate the prevalence and risk factors of clopidogrel resistance, and association between thromboembolic complications and clopidogrel resistance in patient with stent-assisted angioplasty for atherosclerotic cerebrovascular disease.

METHODS

Between September 2006 and June 2008, clopidogrel resistance test was performed on 41 patients who underwent stent-assisted angioplasty for atherosclerotic cerebrovascular disease. It was performed before drug administration and about 12 hours after drug administration (loading dose : 300 mg, maintain dose : 75 mg). Two patients were excluded, and 41 patients were included (mean : 67.59±7.10 years, age range : 41-79). Among 41 patients, 18 patients had intracranial lesions, and 23 had extracranial lesions. We evaluated the prevalence, risk factors and complications related to clopidogrel resistance.

RESULTS

Twenty-one patients (51.2%) showed clopidogrel resistance [intracranial : 10 patients (55.6%), extracranial : 11 patients (47.8%)] and no clopidogrel resistance was seen in 20 patients. Hypercholesterolemia was an indepedent risk factor of clopidogrel resistance. Stent-assisted angioplasty was technically successful in all patients, but acute in-stent thrombosis occurred in 5 patients with intracranial lesions (4 patients with clopidogrel resistance and 1 without clopidogrel resistance). Acute thrombi were completely lysed after intra-arterial infusion of abciximab.

CONCLUSION

There was relatively high prevalence of clopidogrel resistance in patients with atherosclerotic cerebrovascular disease. Hypercholesterolemia was an independent predictive factor of clopidogrel resistance. Acute in-stent thrombosis was more frequently seen in the clopidogrel resistant group. Therefore, clopidogrel resistance test should be performed to avoid thromboembolic complications related to stent-assisted angioplasty for atherosclerotic cerebrovascular disease, especially patients with hypercholeterolemia and intracranial lesion.

Clinical evidence of interaction between clopidogrel and proton pump inhibitors

Clopidogrel is approved for reduction of atherothrombotic events in patients with cardiovascular (CV) and cerebrovascular disease. Dual antiplatelet therapy with aspirin and clopidogrel decreases the risk of major adverse cardiac events after acute coronary syndrome or percutaneous coronary intervention, compared with aspirin alone. Due to concern about gastrointestinal bleeding in patients who are receiving clopidogrel and aspirin therapy, current guidelines recommend combined use of a proton pump inhibitor (PPI) to decrease the risk of bleeding. Data from previous pharmacological studies have shown that PPIs, which are extensively metabolized by the cytochrome system, may decrease the ADP-induced platelet aggregation of clopidogrel. Results from retrospective cohort studies have shown a higher incidence of major CV events in patients receiving both clopidogrel and PPIs than in those without PPIs. However, other retrospective analyses of randomized clinical trials have not shown that the concomitant PPI administration is associated with increased CV events among clopidogrel users. These controversial results suggest that large specific studies are needed. This article reviews the metabolism of clopidogrel and PPIs, existing clinical data regarding the interaction between clopidogrel and PPIs, and tries to provide recommendations for health care professionals.