Clopidogrel withdrawal is associated with proinflammatory and prothrombotic effects in patients with diabetes and coronary artery disease

Migraine with aura after clopidogrel withdrawal: evidence of inflammation as a migraine trigger? – Case report

This article presents the case of a PFO (patent foramen ovale) closure patient with double antiplatelet therapy in whom aspirin was discontinued before clopidogrel and that, at clopidogrel withdrawal, presented “de novo” migraine with visual aura attacks. Migraines with aura associated with atrial right-to-left shunts (PFO and other atrial septal defects) are attributed to the arrival of vasoactive substances in the brain, since not cleared by the lungs. In this case, discontinuation of clopidogrel one year after PFO closure induced “de novo” migraine with aura. Conclusion Rather than confirming the prophylactic effects of clopidogrel for migraine with aura, its triggering at clopidogrel withdrawal is more likely related to a proinflammatory effect of discontinuing clopidogrel. This proinflammatory effect has been described in cardiological research, and reinforces that patients receiving dual antiplatelet therapy (clopidogrel and aspirin) should always have clopidogrel discontinued before aspirin in order to avoid proinflammatory or pro-thrombotic events.

Impact of diabetes mellitus on the pharmacodynamic effects of prasugrel and ticagrelor after switching from clopidogrel in patients with coronary artery disease

Switching P2Y₁₂ inhibitors is common in clinical practice. However, data on the pharmacodynamic (PD) effects of switching in clinical settings characterized by high platelet reactivity, such as diabetes mellitus (DM), are limited. This is a post-hoc analysis from a prospective, randomized, open-label study conducted in coronary artery disease patients comparing the PD effects of loading dose (LD) and maintenance dose regimens of prasugrel vs ticagrelor according to DM status. A total of 110 patients were enrolled: 42 (38%) with DM and 68 (62%) without DM. All patients were on maintenance dual antiplatelet therapy with aspirin and clopidogrel. PD assessments were performed using whole blood vasodilator-stimulated phosphoprotein (VASP), with results quantified by the platelet reactivity index (PRI), VerifyNow P2Y12 (VN-P2Y12) with results reported as P2Y12 reaction units (PRU), and light transmittance aggregometry (LTA) following 20 and 5 µM adenosine diphosphate stimuli with results reported as maximum platelet aggregation (MPA). PD assessments were performed at baseline (while on clopidogrel), 30 min after LD, 2 h after LD, and 1 week after LD. Overall, platelet reactivity was higher in DM than in non-DM patients while on clopidogrel therapy. After switching to either prasugrel or ticagrelor, platelet reactivity dropped but remained significantly higher among patients with DM at 30 min with all tests (VN-PRU p < 0.01, MPA 20 µM p < 0.01, VASP-PRI p = 0.02) and at 2 h with VN-PRU (p < 0.01) and LTA-MPA 20 µM (p < 0.01) but not with VASP-PRI (p = 0.19). There were no significant differences between prasugrel and ticagrelor both among patients with or without DM, except for lower LTA-MPA 20 at 30 min (p < 0.01) among non-DM patients treated with prasugrel. Patients with DM treated with clopidogrel have higher platelet reactivity compared to patients without DM. Although platelet reactivity markedly reduces to a similar extent after switching to prasugrel or ticagrelor, patients with DM persist with increased platelet reactivity compared to patients without DM.Study registration: ClinicalTrials.gov identifier: NCT01852175.

Platelet reactivity after clopidogrel loading in patients with acute ischemic stroke

Objective

It remains unclear when sufficient antiplatelet effect is achieved after administration of a loading dose of clopidogrel in patients with acute ischemic stroke (AIS). This study aimed to evaluate the clopidogrel response in patients with AIS identified by the platelet function test (PFT).

Methods

P2Y12 reaction unit (PRU) values measured using VerifyNow at baseline and at 6, 24, and 72 h after administration of a loading dose (300 mg) of clopidogrel were compared between patients with AIS and those of other cerebrovascular diseases (CVD). The prevalence of clopidogrel abnormal response and its associated factors were examined.

Results

The PRU value was significantly reduced with time in the other CVD group (p &lt; 0.0001), and also in the AIS group (p = 0.0073). The PRU values were significantly higher in the AIS group than in the other CVD group (p &lt; 0.0001 between the groups, baseline: 314 ± 53 vs. 284 ± 62, p = 0.35; 6 h: 290 ± 66 vs. 214 ± 71, p = 0.016; 24 h: 270 ± 75 vs. 190 ± 70, p &lt; 0.0001; and 72 h: 231 ± 76 vs. 163 ± 93, p = 0.105). The prevalence of clopidogrel hypo-responder (PRU &gt; 240 at 24 h after administration) was higher in the AIS group (79 vs. 33%, p &lt; 0.0001) and associated with the baseline PRU value but not with the cytochrome P450 2C19 genotype or clinical ischemic events.

Conclusions

Residual platelet reactivity at 24 h after clopidogrel loading was substantially higher in patients with AIS than in patients with other CVD. In addition, most patients with AIS were judged to be hypo-responders on PFT. This should be carefully interpreted in patients with AIS because of poor specificity for predicting clinical ischemic events.

Precision medicine in interventional cardiology: implications for antiplatelet therapy in patients undergoing percutaneous coronary intervention

Precision medicine is a medical model that proposes the customization of medical treatments to the individual patient, as opposed to a one-drug-fits-all model. Such a "personalized medicine" approach has been widely adopted in several medical fields, such as cancer medicine, but the implementation of precision medicine in cardiovascular medicine has not been similarly straightforward. Because pharmacogenomics plays an important role in the safety and efficacy of cardiovascular drug therapy, there has been a great interest in the use of tools aiming at personalizing antiplatelet therapy. Moreover, antiplatelet therapy is essential for the treatment of cardiovascular patients to reduce the risk of thrombotic complications, particularly those undergoing percutaneous coronary intervention, but it is inevitably associated with increased bleeding risk. In this review, the authors discuss the rationale, summarize the evidence and discuss the current and future directions for the personalization of antiplatelet treatment regimens in patients undergoing percutaneous coronary intervention.

The Role of Platelets in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is among the most common microvascular complications in patients with diabetes, and it currently accounts for the majority of end-stage kidney disease cases worldwide. The pathogenesis of DKD is complex and multifactorial, including systemic and intra-renal inflammatory and coagulation processes. Activated platelets play a pivotal role in inflammation, coagulation, and fibrosis. Mounting evidence shows that platelets play a role in the pathogenesis and progression of DKD. The potentially beneficial effects of antiplatelet agents in preventing progression of DKD has been studied in animal models and clinical trials. This review summarizes the current knowledge on the role of platelets in DKD, including the potential therapeutic effects of antiplatelet therapies.

Dual Antiplatelet Therapy Discontinuation, Platelet Reactivity, and Adverse Outcomes After Successful Percutaneous Coronary Intervention

OBJECTIVES

The purpose of this study was to assess the extent to which the association between premature dual antiplatelet therapy (DAPT) discontinuation and excess risk of thrombotic events varies according to the reason and timing of DAPT discontinuation and whether high on-treatment platelet reactivity (HPR) influences the risk of thrombotic events after premature DAPT discontinuation.

BACKGROUND

DAPT after percutaneous coronary intervention (PCI) suppresses platelet reactivity, and HPR on clopidogrel after PCI is associated with an increased risk of thrombotic events.

METHODS

ADAPT-DES (Assessment of Dual Antiplatelet Therapy With Drug-Eluting Stents) was a prospective, multicenter registry of 8,582 patients successfully treated with coronary drug-eluting stents that assessed HPR on clopidogrel. For patients who discontinued aspirin or clopidogrel at any time during the study, the reasons for discontinuation were systematically categorized.

RESULTS

Planned DAPT discontinuation occurred within 2 years in 3,203 (37.3%) patients. One thousand four hundred eighteen (16.5%) patients discontinued DAPT for unplanned reasons, including surgery or trauma (n = 768 [8.9%]), patient nonadherence (n = 321 [3.7%]), bleeding complications (n = 264 [3.1%]), and drug allergy or hypersensitivity (n = 113 [1.3%]). Unplanned but not planned DAPT discontinuation was associated with an increased risk of a major adverse cardiac event (MACE, defined as the composite of cardiac death, myocardial infarction, or stent thrombosis); with highest risk within 3 months after PCI (adjusted HR: 7.65, 95% CI: 2.77-21.10 vs adjusted HR: 2.47, 95% CI: 1.70-3.58 for unplanned DAPT discontinuation ≥3 weeks after PCI). MACE risk after DAPT discontinuation was not moderated by HPR (P_interaction = 0.91).

CONCLUSIONS

In this large-scale all-comers registry, premature DAPT discontinuation for unplanned reasons occurred in approximately 1 of 6 patients after DES implantation and was associated with a markedly increased risk of MACEs. (Assessment of Dual AntiPlatelet Therapy With Drug Eluting Stents [ADAPT-DES]; NCT00638794).

Tensile strength assay comparing the resistance between two different autologous platelet concentrates (leucocyte-platelet rich fibrin versus advanced-platelet rich fibrin): a pilot study

Background

Since the leucocyte-platelet rich fibrin (L-PRF) was published in 2001, many studies have been developed, analyzing its properties, and also verifying new possibilities to improve it. Thereby, it emerges the advanced-platelet rich fibrin (A-PRF) with a protocol that optimizes the properties obtained by the L-PRF. Nonetheless, there is a gap in the literature to landmark the evolutive process concerning the mechanical properties in specific the resistance to tensile strength which consequently may influence the time for membrane degradation. Thus, this study had the goal to compare the resistance to the traction of membranes produced with the original L-PRF and A-PRF protocols, being the first to this direct comparison.

Findings

The harvest of blood from a healthy single person, with no history of anticoagulant usage. We performed the protocols described in the literature, within a total of 13 membranes produced for each protocol (n = 26). Afterward, the membranes were prepared and submitted to a traction test assessing the maximal and the average traction achieved for each membrane. The data were analyzed statistically using the unpaired t test. Regarding average traction, A-PRF obtained a value of 0.0288 N mm⁻² and L-PRF 0.0192 N mm⁻² (p < 0.05 using unpaired t test). For maximal traction, A-PRF obtained 0.0752 N mm⁻² and L-PRF 0.0425 N mm⁻² (p < 0.05 using unpaired t test).

Conclusion

With this study, it was possible to conclude that indeed A-PRF has a significative higher maximal traction score and higher average traction compared to L-PRF, indicating that it had a higher resistance when two opposing forces are applied.

Recovery of platelet reactivity following cessation of either aspirin or ticagrelor in patients treated with dual antiplatelet therapy following percutaneous coronary intervention: a GLOBAL LEADERS substudy

Cessation of one component of dual antiplatelet therapy (DAPT) following percutaneous coronary intervention (PCI) has been associated with increased risk of ischemic events but it is uncertain whether discontinuation of aspirin is preferable to discontinuation of the oral P2Y₁₂ inhibitor. The GLOBAL LEADERS study compared two antiplatelet strategies following PCI, cessation of aspirin at 1 month with continued ticagrelor monotherapy for 23 months versus standard DAPT for 12 months followed by aspirin monotherapy for a further 12 months. We assessed recovery of platelet reactivity after withdrawal of either aspirin or ticagrelor at 1 month and 12 months, respectively, in this study. Platelet aggregation (PA) was assessed before cessation of DAPT ('baseline') and after 2, 7, and 14 days post-cessation using Multiplate whole-blood aggregometry with collagen, thrombin-receptor-activating peptide (TRAP), adenosine diphosphate (ADP) and arachidonic acid (AA) as agonists. Following cessation of aspirin at 1 month, there was marked recovery of PA induced by AA (baseline [mean ± SD]: 11.1 ± 7.4 U vs. 14 days: 64.9 ± 19.6 U, p < .0001) and collagen (37.4 ± 22.9 U vs. 79.8 ± 13.8 U, p < .0001), whereas PA induced by ADP (18.6 ± 6.6 vs. 69.1 ± 20.5, p < .0001) and collagen (34.4 ± 18.7 U vs. 43.0 ± 21.0, p = .0018) recovered following cessation of ticagrelor at 12 months. There were no significant changes in TRAP-induced PA in either group. In conclusion, cessation of either component of DAPT leads to substantial increase in platelet reactivity with differential effects on different pathways of platelet activation when aspirin or the P2Y₁₂ inhibitor is stopped. Further work is required to determine which patients receive net benefit from long-term continuation of DAPT.

Nonalcoholic fatty liver disease: implications for endocrinologists and cardiologists

Type 2 diabetes mellitus is not just a risk factor but a progression factor for a plethora of multi-organ complications, including the liver and the vascular system. The profibrogenic-inflammatory liver disease nonalcoholic steatohepatitis affects patient's mortality and overall cardiovascular and liver-related complications. There is an evident overlap between these diseases; therefore, there are important implications for endocrinologists, cardiologists, and hepatologists when treating these patients. In addition, as newly approved nonalcoholic steatohepatitis pharmacotherapy is expected to be available early this year, clinicians need to be able to identify patients with type 2 diabetes mellitus that are at risk of advanced liver fibrosis to establish adequate and efficient management plans to limit or avoid cardiovascular or liver-related complications. In this review, we summarize the current knowledge in the nonalcoholic steatohepatitis field with potential value for clinicians focusing on the implications of the overlap between type 2 diabetes mellitus, cardiovascular disease, and nonalcoholic steatohepatitis, the available diagnostic tools for risk stratification, management pathways, and nonalcoholic steatohepatitis pharmacotherapy, including antidiabetic and cardiovascular drugs that may be beneficial or detrimental to their patients.

Clopidogrel combats neuroinflammation and enhances learning behavior and memory in a rat model of Alzheimer's disease

BACKGROUND AND AIM

Alzheimer's disease (AD) is a progressive neurodegenerative disease. Multiple molecular mechanisms have been employed in its pathogenesis such as Amyloid β (Aβ) formation, tau protein hyperphosphorylation, reduced acetylcholine (ACh) level, and neuroinflammation. This study aimed to assess the possible neuroprotective effect of clopidogrel in AD model induced by aluminum chloride (AlCl₃) in rats.

METHODS

Sixty adult male Sprague-Dawley rats were divided into four different groups: Control, AlCl₃, AlCl₃ + donepezil, and AlCl₃ + Clopidogrel. AlCl₃ and the drugs were given orally once/day for 42 days. The spatial learning and memory and recognition memory were evaluated using Morris Water Maze (MWM) and Novel Object Recognition (NOR) tests, respectively. After euthanasia, hippocampal acetylcholinesterase (AChE) activity, tumor necrosis factor-alpha (TNF-α), and interleukin-1β (IL-1β) levels were biochemically assessed. Moreover, amyloid precursor protein (APP) mRNA gene expression was analyzed in the hippocampi of all rats. Histopathology for amyloid plaques was done.

RESULTS

Clopidogrel co-treatment significantly ameliorated the cognitive deficits induced by AlCl₃ in rats. Besides, clopidogrel significantly reduced AChE activity, TNF-α and IL-1β concentrations, and APP mRNA gene expression in the hippocampi of rats compared to AlCl₃ rats. The decrease of hippocampal TNF-α and IL-1β concentrations by clopidogrel was significant compared to donepezil co-treated rats. Clopidogrel co-treatment lessened amyloid plaque deposition in the hippocampal tissues of rats compared to AlCl₃ rats.

CONCLUSION

These findings demonstrate that clopidogrel could alleviate learning and memory deficit induced by AlCl₃ in rats and significantly reduced AChE activity. The neuroprotective outcome of clopidogrel might be assigned to its anti-inflammatory effect.

Combined aspirin and clopidogrel therapy in phacoemulsification cataract surgery: a risk factor for ocular hemorrhage?

PURPOSE

To evaluate the safety of phacoemulsification cataract surgery in the patients undergoing dual antiplatelet therapy with aspirin and clopidogrel.

METHODS

Consecutive patients undergoing phacoemulsification cataract surgery with a clear corneal incision under topical anesthesia were eligible for inclusion in the study. Thirty-eight eyes from 38 patients on combined aspirin and clopidogrel therapy who continued the treatment were classified into the maintenance group, a matched group of 38 eyes from 38 patients on no antiplatelet/anticoagulant therapy as the control group. The best-corrected visual acuity (BCVA) and incidences of complications were compared between the two groups.

RESULTS

There was no significant difference in final BCVA between the maintenance group and the control group (p = 0.178). No significant difference existed in the incidences of hemorrhagic or non-hemorrhagic complications between the two groups (p = 0.529 and p = 0.589, respectively). Moreover, no surgery was postponed or cancelled due to hemorrhagic complications in either group, and no cardiovascular events occurred during the follow-up. There was no case of anterior chamber hemorrhage, vitreous hemorrhage, or suprachoroidal hemorrhage.

CONCLUSIONS

Our outcomes indicated that phacoemulsification cataract surgery using a clear corneal incision with topical anesthesia could be safely done without stopping dual antiplatelet therapy with aspirin and clopidogrel.

The effect of cessation of 2nd generation P2Y12 inhibitor therapy on platelet reactivity in patients 1 year after acute myocardial infarction

To assess the effect of cessation of dual antiplatelet therapy (DAPT) regimens containing 2nd generation P₂Y₁₂ inhibitors on platelet reactivity, in patients who completed 12 months of DAPT following an acute myocardial infarction. Clinical data has shown an increased cardiovascular risk in the 90 days following cessation of DAPT. One possible explanation is a transient platelet hyper-reactivity after cessation of treatment. Data from patients treated with 2nd generation P₂Y₁₂ inhibitors is scarce. Patients who completed 12 month DAPT with prasugrel/ticagrelor underwent serial assessment of platelet reactivity (on DAPT and 1, 4 and 12 weeks post cessation). The primary outcome was platelet reactivity, expressed as platelet reactivity units (PRU) at each time point. 41 participants were included in this study, (23 ticagrelor, 18 prasugrel). There was no statistically significant differences in baseline characteristics between prasugrel/ticagrelor treated patients . The pattern of platelet reactivity recovery after DAPT cessation differed between the ticagrelor and prasugrel: with ticagrelor, after the initial PRU increase from baseline, the PRU remained stable, while with prasugrel, there was a further increase in PRU between 1 and 4 weeks, with a return to the 1 week level by 12 weeks (p = 0.034 for the time × treatment interaction between ticagrelor and prasugrel). Our results suggest there is a transient platelet hyper-reactivity after cessation of ADP receptor blockers therapy with prasugrel, but not ticagrelor. Further research is required to elucidate the pathophysiologic mechanisms behind these findings and to evaluate potential strategies to prevent or overcome this "rebound" effect.

Platelets, inflammation and anti-inflammatory effects of antiplatelet drugs in ACS and CAD

Platelets play a pivotal role in chronic inflammation leading to progression of atherosclerosis and acute coronary events. Recent discoveries on novel mechanisms and platelet-dependent inflammatory targets underpin the role of platelets to maintain a chronic inflammatory condition in cardiovascular disease. There is strong and clinically relevant crosslink between chronic inflammation and platelet activation. Antiplatelet therapy is a cornerstone in the prevention and treatment of acute cardiovascular events. The benefit of antiplatelet agents has mainly been attributed to their direct anti-aggregatory impact. Some anti-inflammatory off-target effects have also been described. However, it is unclear whether these effects are secondary due to inhibition of platelet activation or are caused by direct distinct mechanisms interfering with inflammatory pathways. This article will highlight novel platelet associated targets that contribute to inflammation in cardiovascular disease and elucidate mechanisms by which currently available antiplatelet agents evolve anti-inflammatory capacities, in particular by carving out the differential mechanisms directly or indirectly affecting platelet mediated inflammation. It will further illustrate the prognostic impact of antiplatelet therapies by reducing inflammatory marker release in recent cardiovascular trials.

The extent of P2Y12 inhibition by clopidogrel in diabetes mellitus patients with acute coronary syndrome is not related to glycaemic control: Roles of white blood cell count and body weight

It was the study objective to determine whether glycaemic control affects the extent of platelet inhibition by thienopyridines as assessed by vasodilator-stimulated phosphoprotein flow cytometry (VASP-FCT) in patients with diabetes mellitus (DM) undergoing percutaneous coronary intervention (PCI) during acute coronary syndrome (ACS). Although the proportion of high on-treatment residual platelet reactivity is higher in DM, the contributions of glycaemic control and other factors associated with DM, such as excess body weight and inflammation, to this impaired platelet inhibition by thienopyridines have not yet been fully characterised. In this study, the extent of P2Y12 ADP receptor pathway inhibition was evaluated by the VASP-FCT. Platelet activation was expressed as the platelet reactivity index (PRI). Low response to clopidogrel (LR) was defined as a PRI of >61%. Four hundred forty-five consecutive ACS patients (DM = 160, NDM = 285) were enrolled. The proportion of LR was higher in DM patients (50 vs. 37.5%). In DM, PRI was not correlated with glycosylated haemoglobin (HbA1c) or glycaemia. In a univariate analysis, LR was associated with age, male sex, overweight, and white blood cell count (WBC). In a multivariate analysis, WBC >10,000 and body weight >80 kg were the sole independent predictors of LR to clopidogrel (hazard ratio (HR) 3.02 [1.36–6.68], p=0.006 and HR 2.47 [1.14–5.35], p = 0.021, respectively). Conversely, in non-DM patients, ST-elevation myocardial infarction was the sole independent predictor of LR. In conclusion, in ACS DM patients undergoing PCI, the extent of P2Y12 inhibition by clopidogrel is not related to glycaemic control but is related to body weight and inflammatory status as assessed by the WBC.

The influence of low-grade inflammation on platelets in patients with stable coronary artery disease

Inflammation is likely to be involved in all stages of atherosclerosis. Numerous inflammatory biomarkers are currently being studied, and even subtle increases in inflammatory biomarkers have been associated with increased risk of cardiovascular events in patients with coronary artery disease (CAD). Low-grade inflammation may influence both platelet production and platelet activation potentially leading to enhanced platelet aggregation. Thrombopoietin is considered the primary regulator of platelet production, but it likely acts in conjunction with numerous cytokines, of which many have altered levels in CAD. Previous studies have shown that high-sensitive C-reactive protein (CRP) independently predicts increased platelet aggregation in stable CAD patients. Increased levels of CRP, fibrinogen, interleukin-6, stromal cell-derived factor-1, CXC motif ligand 16, macrophage migration inhibitory factor, RANTES, calprotectin, and copeptin have been associated with increased risk of cardiovascular events in CAD patients. Additionally, some of these inflammatory markers have been associated with enhanced platelet activation and aggregation. However, CRP and other inflammatory markers provide only limited additional predictive value to classical risk factors such as smoking, blood pressure, and cholesterol levels. Existing data do not clarify whether inflammation simply accompanies CAD and increased production and aggregation of platelets, or whether a causal relationship exists. In this review, we provide a comprehensive overview of inflammatory markers in stable CAD with particular emphasis on platelet production, activation, and aggregation in CAD patients.

Similar Impact of Clopidogrel or Ticagrelor on Carotid Atherosclerotic Plaque Inflammation

BACKGROUND

Platelets play an important role in inflammation. Inhibitors of the P2Y₁₂ receptor, which is involved in platelet activation, may have a direct effect on carotid atherosclerotic plaque inflammation.

HYPOTHESIS

We compared the effects of clopidogrel and ticagrelor therapy for carotid atherosclerotic plaque inflammation using ¹⁸ F-fluorodeoxyglucose ( ¹⁸ FDG) positron emission tomography (PET) imaging.

METHODS

Fifty patients with acute coronary syndrome and ≥1 ¹⁸ FDG uptake in the carotid artery (target-to-background ratio [TBR] ≥1.6) were randomized to either clopidogrel or ticagrelor groups. Of these, 46 completed PET examinations at baseline and at 6 months. The primary endpoint was the percent change in TBR of the index vessel at the most diseased segment (MDS).

RESULTS

Baseline characteristics were similar between the 2 groups. At 6-month follow-up, low-density lipoprotein cholesterol and C-reactive protein significantly decreased in both groups (P < 0.001). The TBR of the index vessel and aorta significantly decreased in both groups (P < 0.01). The percent change in the MDS TBR of the index vessel was numerically but not significantly lower in the clopidogrel group than in the ticagrelor group (-9.5 ± 14.6% vs -13.5 ± 19.3%; P = 0.427). Likewise, the percent change in the whole-vessel TBR of the index vessel was not different between the 2 groups (P = 0.166). Similar findings were observed for changes in the MDS TBR (P = 0.412) or whole-vessel TBR of the aorta (P = 0.363).

CONCLUSIONS

Carotid atherosclerotic plaque inflammation significantly decreases to a similar degree following 6 months of either clopidogrel or ticagrelor treatment.

Effects of P2Y12 receptor antagonists beyond platelet inhibition--comparison of ticagrelor with thienopyridines

The effect and clinical benefit of P2Y12 receptor antagonists may not be limited to platelet inhibition and the prevention of arterial thrombus formation. Potential additional effects include reduction of the pro-inflammatory role of activated platelets and effects related to P2Y12 receptor inhibition on other cells apart from platelets. P2Y12 receptor antagonists, thienopyridines and ticagrelor, differ in their mode of action being prodrugs instead of direct acting and irreversibly instead of reversibly binding to P2Y12 . These key differences may provide different potential when it comes to additional effects. In addition to P2Y12 receptor blockade, ticagrelor is unique in having the only well-documented additional target of inhibition, the equilibrative nucleoside transporter 1. The current review will address the effects of P2Y12 receptor antagonists beyond platelets and the protection against arterial thrombosis. The discussion will include the potential for thienopyridines and ticagrelor to mediate anti-inflammatory effects, to conserve vascular function, to affect atherosclerosis, to provide cardioprotection and to induce dyspnea.

Coming safely to a stop: a review of platelet activity after cessation of antiplatelet drugs

The platelet P2Y12 antagonists are widely used, usually in combination with aspirin, to prevent atherothrombotic events in patients with acute coronary syndromes during percutaneous coronary intervention and after placement of arterial stents. Inhibition by clopidogrel or prasugrel lasts for the lifetime of the affected platelets and platelet haemostatic function gradually recovers after stopping the drug, as new unaffected platelets are formed. The optimal durations for dual antiplatelet therapy are prescribed by clinical guidelines. Continuation beyond the recommended duration is associated with an increased mortality, mainly associated with major bleeding. Fear of a 'rebound' of prothrombotic platelet activity on stopping the drug has provoked much discussion and many studies. However, review of the available literature reveals no evidence for production of hyper-reactive platelets after cessation of clopidogrel in patients who are stable. Any increase in acute coronary and other vascular events after stopping seems most likely therefore to be due to premature discontinuation or disruption of treatment while thrombotic risk is still high. No difference in rebound was found with the newer P2Y12 inhibitors, although ticagrelor and prasugrel are more potent platelet inhibitors than clopidogrel. Recent randomized controlled trials confirm it is safe to stop the thienopyridine and continue with aspirin alone in most patients after the duration of treatment recommended by the guidelines. Decisions on when to stop therapy in individuals, however, remain challenging and there is a growing rationale for platelet testing to assist clinical judgement in certain situations such as patients stopping dual antiplatelet therapy before surgery or in individuals at highest bleeding or thrombotic risk.

Clopidogrel response variability is associated with endothelial dysfunction in coronary artery disease patients receiving dual antiplatelet therapy

OBJECTIVES

Dual antiplatelet therapy with aspirin and a platelet P2Y12 ADP receptor antagonist is the cornerstone of treatment following percutaneous coronary intervention (PCI). Several clinical and genetic factors can cause suboptimal clopidogrel response. We examined the impact of endothelial dysfunction on clopidogrel response variability in subjects with stable coronary artery disease (CAD) after PCI.

METHODS

We consecutively enrolled 198 patients with stable CAD one month after successful PCI. All patients were receiving dual antiplatelet therapy (clopidogrel 75 mg and aspirin 100 mg/day). Platelet reactivity was measured by VerifyNow P2Y12 assay (Accumetrics, San Diego, CA). VerifyNow reports its results in P2Y12 reaction units (PRU) and the diagnostic cut-off value is 230. Endothelial function was evaluated by flow mediated dilation (FMD).

RESULTS

Patients with high on treatment platelet reactivity (32% of the study population), compared to subjects with low on treatment platelet reactivity, presented decreased FMD values (4.35 ± 2.22% vs. 5.74 ± 3.29%, p = 0.01). Moreover, an inverse association between endothelial function measurement and platelet reactivity (r = -0.24, p = 0.001) was found. Importantly, multivariate analysis after adjustment for age, gender and confounders revealed by the univariate analysis (left ventricle ejection fraction, body mass index, diabetes, dyslipidemia, coronary lesion number) showed that for every decrease in FMD by 1% there is an anticipated increased in the odds of patients to have HPR by 1.66 (95% CI 1.03-2.57, p = 0.037).

CONCLUSIONS

Endothelial dysfunction is associated with clopidogrel response variability in patients after PCI receiving dual antiplatelet therapy. These findings shed some light on the mechanisms affecting individual platelet response to antiplatelet therapy and may explain the non-straight forward association between clopidogrel dose, platelet inhibition and cardiovascular outcome.

The effect of clopidogrel on platelet activity in patients with and without type-2 diabetes mellitus: a comparative study

Background

Although antiplatelet therapy involving clopidogrel is a standard treatment for preventing cardiovascular events after coronary stent implantation, patients can display differential responses. Here, we assessed the effectiveness of clopidogrel on platelet function inhibition in subjects with and without type-2 diabetes and stable coronary artery disease. In addition, we investigated the correlation between platelet function and routine clinical parameters.

Methods

A total of 64 patients with stable coronary heart disease were enrolled in the study. Among these, 32 had known type-2 diabetes, whereas the remaining 32 subjects were non-diabetics (control group). A loading dose of 300 mg clopidogrel was given to clopidogrel-naïve patients (13 patients in the diabetes group and 14 control patients). All patients were given a daily maintenance dose of 75 mg clopidogrel. In addition, all patients received 100 mg ASA per day. Agonist-induced platelet aggregation measurements were performed on hirudin-anticoagulated blood using an impedance aggregometer (Multiple Platelet Function Analyzer, Dynabyte, Munich, Germany). Blood samples were drawn from the antecubital vein 24 h after coronary angiography with percutaneous coronary intervention. The platelets were then stimulated with ADP alone or ADP and prostaglandin-E (ADP and ADP-PGE tests, respectively) in order to evaluate clopidogrel-mediated inhibition of platelet function. The effectiveness of ASA was measured by stimulation with arachidonic acid (ASPI test). In addition, maximal platelet aggregation was assessed via stimulation with thrombin receptor-activating peptide (TRAP test).

Results

Patients with diabetes exhibited significantly less inhibition of platelet function than patients without diabetes (ADP-PGE test p = 0.003; ASPI test p = 0.022). Administering a clopidogrel loading dose of 300 mg did not result in a lower level of ADP-PGE-induced platelet reactivity in comparison to the use of a 75 mg maintenance dose. Moreover, we observed that ADP-PGE-induced platelet inhibition was positively correlated with fasting blood glucose and HbA1c (p < 0.01).

Conclusions

Patients with type-2 diabetes exhibited increased platelet reactivity compared to patients without diabetes despite combined treatment with clopidogrel and ASA. Using a loading dose of clopidogrel rather than small daily doses was not sufficient for adequately overcoming increased platelet reactivity in patients with type-2 diabetes, highlighting the need for more effective anti-platelet drugs for such patients.

The role of P2Y₁₂ receptor and activated platelets during inflammation

Platelets play an important role not only during thrombosis, but also in modulating immune responses through their interaction with immune cells and by releasing inflammatory mediators upon activation. The P2Y12 receptor is a Gi-coupled receptor that not only regulates ADP-induced aggregation but can also dramatically potentiate secretion, when platelets are activated by other stimuli. Considering the importance of P2Y12 receptor in platelet function, a class of antiplatelet drugs, thienopyridines, have been designed and successfully used to prevent thrombosis. This review will focus on the role of activated platelets in inflammation and the effects that P2Y12 antagonism exerts on the inflammatory process. A change in platelet functions was noted in patients treated with thienopyridines during inflammatory conditions, suggesting that platelets may modulate the inflammatory response. Further experiments in a variety of animal models of diseases, such as sepsis, rheumatoid arthritis, myocardial infarction, pancreatitis and pulmonary inflammation have also demonstrated that activated platelets influence the inflammatory state. Platelets can secrete inflammatory modulators in a P2Y12-dependent manner, and, as a result, directly alter the inflammatory response. P2Y12 receptor may also be expressed in other cells of the immune system, indicating that thienopyridines could directly influence the immune system rather than only through platelets. Overall the results obtained to date strongly support the notion that activated platelets significantly contribute to the inflammatory process and that antagonizing P2Y12 receptor can influence the immune response.

The platelet P2 receptors in inflammation

In addition to their well characterized and established role in haemostasis and thrombosis, platelets contribute to the pathogenesis of inflammation. Adenine nucleotides are signalling molecules that regulate the function of virtually every cell in the body, by interacting with P2 receptors. Their important role in inflammation is well established. In the last few years, the pro-inflammatory roles of adenine nucleotides interacting with their platelet P2 receptors has emerged. In particular, it was shown that the platelet P2Y12 receptor for ADP significantly contributed to the pro-inflammatory effects of cysteinyl leukotrienes (CysLT) in experimental models of asthma in mice. More importantly, it was recently shown that P2Y12 variants were associated with lung function in a large family-based asthma cohort and that the P2Y12 antagonist prasugrel tended to decrease bronchial hyper-reactivity to mannitol in patients with allergic bronchial asthma in a randomized, placebo controlled trial.

CONCLUSION

These data strongly suggest that P2Y12 may represent an important pharmacological target for the treatment of patients with allergic bronchial asthma.

Men with lower HDL cholesterol levels have significant increment of soluble CD40 ligand and high-sensitivity CRP levels following the cessation of long-term clopidogrel therapy

AIM

The aim of this study was to examine whether the termination of long-term clopidogrel therapy results in a proinflammatory state and whether lipid parameters influence the inflammatory response after stopping the drug.

METHODS

A prospective, multicenter study was conducted among 200 patients with implanted coronary stents who received dual antiplatelet therapy for one year, without ischemic or bleeding events. According to the guidelines, clopidogrel was discontinued after one year. In all patients, the high-sensitivity C-reactive protein (hsCRP), soluble CD40 ligand (sCD40L) and lipid [total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C)] levels were measured twice: on the day of cessation of clopidogrel and 45 days after the termination of clopidogrel treatment.

RESULTS

In men (n=151), the sCD40L serum levels were significantly higher 45 days after the discontinuation of clopidogrel (p=0.007), while the hsCRP levels were not significantly different (p=0.407). Furthermore, when analyzed across the HDL-C quartiles, the hsCRP and sCD40L values were found to be associated with the levels of HDL-C after the discontinuation of clopidogrel in men. In addition, the men in the first HDL-C quartile exhibited the most pronounced increase in the sCD40L levels (p=0.001) and had significantly higher hsCRP levels (p=0.001) compared to the subjects in the other quartiles. Other lipid parameters did not show any associations with the sCD40L or hsCRP levels.

CONCLUSIONS

The discontinuation of clopidogrel is associated with higher increments in the sCD40L level, and a pronounced proinflammatory response is associated with a lower HDL-C concentration.

Twelve-month results of a randomized trial comparing mono with dual antiplatelet therapy in endovascularly treated patients with peripheral artery disease

PURPOSE

To present the 12-month results of a trial investigating the effects of dual antiplatelet therapy on target lesion revascularization (TLR) after balloon angioplasty ± stenting in the femoropopliteal segment.

METHODS

A prospective, randomized, single-center, double-blinded and placebo-controlled clinical trial randomly assigned 40 patients to receive pre- and postinterventional therapy with aspirin and clopidogrel. Another 40 patients received the same doses of aspirin and placebo instead of clopidogrel. Clopidogrel and placebo were stopped after 6 months, and patients remained on aspirin only. At 12 months after the intervention, 36 clopidogrel patients and 37 placebo patients were reevaluated.

RESULTS

At 6 months, clopidogrel patients had significantly lower rates of TLR compared to placebo patients [2 (5%) vs. 8 (20%), p=0.04]. After stopping clopidogrel/placebo after 6 months, there was no significant difference in TLR at 12 months after treatment [9 (25%) clopidogrel vs. 12 (32.4%) placebo, p=0.35]. Mortality was 0 vs. 1 in the placebo group at 6 months (p=0.32) and 0 vs. 3 at 12 months (p=0.08).

CONCLUSION

In contrast to the first report of a reduction in the TLR at 6 months, this advantage of dual antiplatelet therapy does not persist after stopping clopidogrel. Prolonged dual therapy (>6 months) should be considered in patients who are at high risk for restenosis.

Overview of pleiotropic effects of platelet P2Y12 receptor inhibitors

Dual antiplatelet therapy consisting of one of the P2Y12 receptor inhibitors in conjunction with aspirin is the mainstay of treatment for patients with acute coronary syndromes (ACS) and those undergoing percutaneous coronary interventions (PCI). In recent years, multiple extra-platelet features of P2Y12 receptor antagonists have been reported in numerous clinical trials. The aim of this review is to summarise reported pleiotropic effects of clopidogrel, prasugrel, ticagrelor and other P2Y12 receptor blockers. We included observations made both in human and in animal models, together with proposed mechanisms of action for described features. If confirmed in randomised studies and properly applied to everyday practice, the observed extra-platelet actions could enable us to improve efficacy of ACS and post-PCI treatment, as well as to confine mortality and occurrence rate of cardiovascular events.

Anti-platelet therapy with clopidogrel prevents endothelial dysfunction and vascular remodeling in aortas from hypertensive rats

The aim was to investigate the beneficial effects of clopidogrel in thoracic aorta function and structure and to characterize if P2Y₁₂ receptors contribute to these effects. Male Sprague Dawley rats were infused with angiotensin II [(Ang II) 60 ng.min⁻¹, 14 days] or saline (control rats) and were simultaneously treated with clopidogrel (10 mg.kg⁻¹.day⁻¹) or vehicle. After 14 days, systolic blood pressure (mmHg) was similar in Ang II-hypertensive rats treated with clopidogrel or vehicle (199±9 vs. 190±11, respectively). Systolic blood pressure in control rats was not altered by clopidogrel treatment (128±1 vs. vehicle, 134±2). Endothelium-dependent relaxation induced by 2-MeS-ADP was decreased in aortas from vehicle-treated Ang II-hypertensive rats, compared to vehicle-treated control rats. This response was elicited via activation of P2Y₁ and P2Y₁₂ receptors. In the presence of L-NAME and indomethacin, 2-MeS-ADP induced contraction and this response was augmented in vehicle-treated Ang II-hypertensive rats, compared to vehicle-treated control rats. The contraction to 2-MeS-ADP was evoked by P2Y₁₃ and P2Y₁₂ receptor activation. Clopidogrel-treatment did not normalize relaxation or contractile responses induced by 2-MeS-ADP in aortas from Ang II-hypertensive rats. P2Y₁ and P2Y₁₂ protein expression was increased, whereas P2Y₁₃ receptor expression was reduced in aorta from vehicle-treated Ang II-hypertensive rats. Endothelium-dependent relaxation upon acetylcholine-stimulation was reduced in vehicle-treated Ang II-hypertensive rats, and clopidogrel treatment was effective in improving endothelial function. Clopidogrel also prevented vascular remodeling, evidenced by augmented media thickness in aortas from Ang II-hypertensive rats. Clopidogrel has beneficial effects on the aortic endothelium of Ang II-hypertensive rats, but its effects do not seem to be directly related to the presence of P2Y₁₂ receptors in this vessel.

Randomised, double-blind trial on the value of tapered discontinuation of clopidogrel maintenance therapy after drug-eluting stent implantation. Intracoronary Stenting and Antithrombotic Regimen: CAUTION in Discontinuing Clopidogrel Therapy--ISAR-CAUTION

There is little evidence on the optimal mode of clopidogrel discontinuation. Epidemiological studies observed clustering of thrombotic events after cessation of chronic clopidogrel therapy. The underlying mechanism has been ascribed to transient platelet hyper-reactivity. Gradual tapering of clopidogrel may have the potential to attenuate this phenomenon. The objective of the present study was to assess whether in patients with drug-eluting stents (DES) gradual discontinuation of clopidogrel maintenance therapy is superior to conventional, abrupt discontinuation. Patients with planned discontinuation of chronic clopidogrel therapy after DES implantation were randomised in a double-blinded fashion to either gradual discontinuation (according to a tapering schema over four weeks) or abrupt discontinuation (after continued clopidogrel therapy for additional four weeks). The primary endpoint was the composite of cardiac death, myocardial infarction, stroke, stent thrombosis, major bleeding or rehospitalisation due to an acute coronary syndrome at 90 days. Enrollment of 3,000 patients was planned. The study was stopped prematurely due to slow recruitment after enrollment of 782 patients. At 90 days, nine of 392 patients (2.3%) with tapered cessation reached the primary endpoint compared to five of 390 patients (1.3%) with abrupt cessation (p=0.284). The composite of death or myocardial infarction occurred in three patients with tapered and three patients with abrupt discontinuation (p=0.764). In conclusion, tapered discontinuation of chronic clopidogrel therapy is not superior to abrupt discontinuation regarding the primary endpoint in this study. However, the results must be interpreted in view of the premature termination of the trial and low event rates.

Effect of platelet reactivity, endothelial function, and inflammatory status on outcomes in patients with stable angina pectoris on clopidogrel therapy

Although high on-treatment platelet reactivity (HTPR) is an important predictor of clinical outcomes in patients undergoing coronary stenting, it is unknown whether endothelial dysfunction and HTPR are associated. We examined the platelet function, peripheral vascular function, endothelial progenitor cell (EPC) number, platelet activation markers, high-sensitivity C-reactive protein (hs-CRP) level, and clinical outcomes in patients receiving chronic clopidogrel therapy. We consecutively enrolled 91 patients who underwent follow-up angiography because of chest discomfort. All patients took aspirin and clopidogrel for an average of 498 ± 138 days. Platelet reactivity was assessed by light transmittance aggregometry (maximal platelet aggregation by 5 μmol/L of adenosine diphosphate ≤50% in group 1 [optimal response] and >50% as group 2 [HTPR]). Flow-mediated dilation of the brachial artery and brachial-ankle pulse wave velocity (PWV), numbers of EPCs isolated from peripheral blood, platelet activation markers (soluble CD40 ligand and soluble P-selectin), and hs-CRP levels were assessed before follow-up angiography. There were no significant differences in baseline characteristics and previous percutaneous coronary intervention (PCI) data between groups 1 (n = 59) and 2 (n = 32). Group 2 showed poorer flow-mediated dilation (6.1 ± 4.1% vs 12.9 ± 6.2%, p <0.001), pulse wave velocity (1925.4 ± 362.2 vs 1571.0 ± 306.5 ms, p <0.001), and lower circulating EPCs by flow cytometry (21.9 ± 14.7 vs 65.2 ± 30.1 per 10 fields, p <0.001) compared with group 1. Significantly higher levels of soluble CD40 ligand, soluble P-selectin, and hs-CRP were observed in group 2. In multivariate analysis, elevated hs-CRP level, but not HTPR, was independently associated with repeated PCI. In patients with angina, HTPR was associated endothelial dysfunction and elevated hs-CRP, although elevated hs-CRP level was significantly associated with poorer outcomes.

Clopidogrel preserves whole kidney autoregulatory behavior in ANG II-induced hypertension

This study tested the hypothesis that P2Y12 receptor blockade with clopidogrel preserves renal autoregulatory ability during ANG II-induced hypertension. Clopidogrel was administered orally to male Sprague-Dawley rats chronically infused with ANG II. After 14 days of treatment, whole kidney autoregulation of renal blood flow was assessed in vivo in pentobarbital-anesthetized rats using an ultrasonic flow probe placed around the left renal artery. In ANG II-vehicle-treated rats, decreasing arterial pressure over a range from 160 to 100 mmHg resulted in a 25 ± 5% decrease in renal blood flow, demonstrating a significant loss of autoregulation with an autoregulatory index of 0.66 ± 0.15. However, clopidogrel treatment preserved autoregulatory behavior in ANG II-treated rats to levels indistinguishable from normotensive sham-operated (sham) rats (autoregulatory index: 0.04 ± 0.14). Compared with normotensive sham-vehicle-treated rats, ANG II infusion increased renal CD3-positive T cell infiltration by 66 ± 6%, induced significant thickening of the preglomerular vessels and glomerular basement membrane and increased glomerular collagen I deposition, tubulointerstitial fibrosis, damage to the proximal tubular brush border, and protein excretion. Clopidogrel significantly reduced renal infiltration of T cells by 39 ± 9% and prevented interstitial artery thickening, ANG II-induced damage to the glomerular basement membrane, deposition of collagen type I, and tubulointerstitial fibrosis, despite the maintenance of hypertension. These data demonstrate that systemic P2Y12 receptor blockade with clopidogrel protects against impairment of autoregulatory behavior and renal vascular injury in ANG II-induced hypertension, possibly by reducing renal T cell infiltration.

Clopidogrel cessation triggers aspirin rebound in patients with coronary stent

WHAT IS KNOWN AND OBJECTIVE

Premature discontinuation of clopidogrel in patients undergoing percutaneous coronary intervention is a significant risk factor for thrombotic adverse outcomes. However, recent studies indicate that even discontinuation of long-term use of clopidogrel may be associated with multiple adverse outcomes, that is, rebound phenomenon whose mechanism is not definitely clear. The aim of the study was to examine the effect of clopidogrel withdrawal in those on combined aspirin and clopidogrel therapy.

METHODS

This prospective, multicenter study enrolled 200 patients who underwent coronary stent implantation and were on dual antiplatelet therapy (100 mg aspirin + 75 mg clopidogrel) 1 year after the stent placement. In all patients, we measured the platelet aggregation, by multiplate electrode aggregometry, using two agonists [adenosine diphosphate with PGE1 (ADPHS) and arachidonic acid (ASPI)] two times: on the day of cessation of clopidogrel and 90 days after clopidogrel was stopped.

RESULTS AND DISCUSSION

Following clopidogrel discontinuation, we registered an increase in ASPI values (P < 0·001), linear correlation between changes in ASPI and ADPHS values (P = 0·009) and significant difference in the values of ASPI first quartile of ADPHS compared with the other three (P < 0·001, P = 0·016, P < 0·001, I vs. II, I vs. III and I vs. IV quartile of ADPHS, respectively).

WHAT IS NEW AND CONCLUSION

Our findings show that cessation of clopidogrel causes loss of antiplatelet synergism with aspirin, leading to a weakening of the response to aspirin, which may be one explanation for the rebound after the clopidogrel cessation.

A randomized controlled trial of platelet activity before and after cessation of clopidogrel therapy in patients with stable cardiovascular disease

OBJECTIVES

The aim of this randomized placebo-controlled trial was to determine if withdrawing clopidogrel therapy leads to increased platelet activity compared with pre-treatment values in patients with stable coronary artery or peripheral arterial disease.

BACKGROUND

Reports of increased cardiovascular events after planned cessation of clopidogrel therapy have raised concerns over the possible existence of a rebound in platelet activity.

METHODS

In all, 171 patients receiving established aspirin therapy were randomly assigned to placebo or clopidogrel (75 mg daily) for 28 days. Blood samples were taken at pre-treatment baseline, on treatment just before discontinuation of study drug, and on days 7, 14, and 28 after discontinuation. The primary outcome measure was adenosine diphosphate (ADP)-stimulated platelet fibrinogen binding. Six secondary outcomes were assessed: ADP-stimulated platelet P-selectin, unstimulated platelet fibrinogen binding, and light transmission aggregometry with ADP 5 and 10 μmol/l recorded at maximum and at 6 min.

RESULTS

The ADP-stimulated platelet fibrinogen binding, P-selectin expression, and platelet aggregation were lower on treatment with clopidogrel compared with baseline (p < 0.0001), but returned to baseline levels by 7 days after discontinuation. Mixed model analyses excluding the on-treatment timepoint showed no overall differences between the clopidogrel and placebo groups (p > 0.05). Furthermore, there was no evidence of an interaction between platelet inhibition over time and treatment allocation.

CONCLUSIONS

This trial found no evidence for rebound of platelet activity to above baseline after stopping clopidogrel in patients with stable coronary artery disease or peripheral arterial disease. (Is Cessation of Clopidogrel Therapy Associated With Rebound of Platelet Activity in Stable Vascular Disease Patients?; ISRCTN77887299/77887299).

Discontinuation of long-term clopidogrel therapy is associated with death and myocardial infarction after saphenous vein graft percutaneous coronary intervention

OBJECTIVES

This study sought to examine the pattern of death and myocardial infarction (MI) after clopidogrel cessation in patients undergoing percutaneous coronary intervention (PCI) of the saphenous vein graft (SVG).

BACKGROUND

The timing and incidence of adverse events by different durations of clopidogrel therapy after SVG PCI remain unknown.

METHODS

This is a cohort study of patients undergoing SVG PCI between 2000 and 2009, followed for all-cause mortality or MI after stopping clopidogrel. Incidence rates were calculated across different time periods after clopidogrel cessation. Adjusted incidence rate ratios (IRR) were calculated with multivariable regression (piecewise exponential and Poisson).

RESULTS

There were 603 patients who underwent SVG PCI, of which 411 were event-free at the time of clopidogrel cessation. The incidence rate (95% confidence interval: [CI])/1,000 person-days of death or MI after stopping clopidogrel in the time intervals of 0 to 90 days, 91 to 365 days, and 1 to 2 years were 1.26 (95% CI: 0.93 to 1.70), 0.41 (95% CI: 0.30 to 0.56), and 0.41 (95% CI: 0.30 to 0.55), respectively. In multivariable analyses, the overall IRR (95% CI) for death or MI in the 0- to 90-day interval after stopping clopidogrel compared with the 91- to 365-day interval was 2.58 (95% CI: 1.64 to 4.07). Similar results were observed over a broad range of clopidogrel treatment durations (<6 months, 6 months to 1 year, 1 to 2 years, or >2 years). The results were also consistent across subgroups, including sex, stent type, stent diameter, PCI period, and diabetes status. When death alone was evaluated, there remained a significant increase in the event rate in the 0- to 90-day interval compared with the 91- to 365-day interval (IRR: 2.33; 95% CI: 1.32 to 4.11).

CONCLUSIONS

A clustering of events was observed in the initial 0 to 90 days after clopidogrel cessation in all treatment durations of clopidogrel investigated after SVG PCI. These results might have important implications in high-risk cohorts undergoing PCI. Additional studies are needed to elucidate the mechanisms underlying the early clustering of events after clopidogrel cessation.

Clopidogrel tapering as a strategy to attenuate platelet rebound phenomenon in patients with bare-metal stents

Early clustering of adverse cardiovascular events after abrupt cessation of clopidogrel has been reported in patients with acute coronary syndromes. A platelet rebound phenomenon may contribute to this increased thrombotic risk and a gradual drug tapering may attenuate this proposed platelet effect. Accordingly, we aimed to assess the effect of clopidogrel tapering on platelet reactivity. Twenty patients who underwent elective percutaneous coronary interventions with bare metal stents receiving 3 months of clopidogrel therapy (75 mg daily) were randomized to either of two discontinuation strategies: (1) Off group-abrupt drug cessation or (2) Tapering group-receiving clopidogrel 75 mg every other day for 4 weeks duration. Light transmission aggregometry, induced by ADP (5 and 10 μM) and collagen, was measured at four time-points (at baseline and 2, 4 and 6 weeks after randomization). In the off group, there was an early rise in platelet reactivity at 2 weeks after abrupt drug cessation compared to baseline, as measured by ADP 5 μmol/l (39.6 ± 2.8 vs. 67.9 ± 6.0, P < 0.001). The tapering regimen suppressed this rebound platelet aggregation by ADP 5 μmol/l at 2 weeks (P = 0.001) and 4 weeks (P = 0.001). Similar results were found with ADP 10 μmol/l and collagen agonists. Abrupt cessation of clopidogrel results in an early rise in platelet aggregability in patients with BMS that is attenuated by a tapering regimen. Clopidogrel administration every other day may achieve similar levels of platelet inhibition as full dose therapy. Further investigations evaluating clopidogrel tapering strategies and their potential clinical impact are warranted.

Perioperative management of a patient with recently placed drug-eluting stents requiring urgent spinal surgery

Patients receiving drug-eluting coronary stents (DES) require antiplatelet therapy for at least 12 months to prevent stent thrombosis (ST), a potentially calamitous event. Since interruption of antiplatelet therapy is the greatest risk factor for ST, it is imperative that the decision to discontinue these agents be based on an accurate assessment of the patient's risk for bleeding complications. Individuals who are regarded as being at a high risk are those undergoing intracranial, spinal or intraocular surgeries. These patients require alternative agents during the perioperative period to minimize both their risk of perioperative thrombosis and intraoperative hemorrhage. We report the case of a woman who required spinal surgery 3 months after she underwent placement of two drug-eluting stents. The patient's clopidogrel was stopped 5 days prior to surgery and an infusion of eptifibatide was used to "bridge" antiplatelet therapy during the perioperative period. Postoperatively, anticoagulation therapy was reinstituted using aspirin with clopidogrel. This case serves as a successful example of bridging therapy using a short acting and gycoprotein (GP) IIb/IIIa inhibitor as a means of maintaining antiplatelet therapy during the perioperative period to minimize the risk of stent thrombosis and the risk of intraoperative bleeding.

Perioperative antiplatelet management in patients with coronary artery stenting

Coronary artery disease is the primary cause of mortality in men and women in the United States. Transcatheter coronary intervention is the mainstay of treatment for patients with acute coronary artery disease presentations and patients with stable disease. Although percutaneous intervention initially only included balloon angioplasty, it now typically involves the placement of intracoronary stents. To overcome the limitations of bare-metal stents, namely in-stent restenosis, stents have been developed that remove pharmaceuticals that reduce neointimal hyperplasia and in-stent restenosis. However, these pharmaceutical agents also delay stent endothelialization, posing a prolonged risk of in situ thrombosis. Placement of an intracoronary stent (eg, bare-metal or drug-eluting stent) requires dual antiplatelet therapy to prevent the potentially life-threatening complication of stent thrombosis. The optimal duration of dual antiplatelet therapy following stent placement is unknown. This article discusses the factors to be considered when deciding when dual antiplatelet therapy can be safely discontinued. Unfortunately, in the hospital setting, this decision to interrupt dual antiplatelet therapy frequently must be made shortly after stent placement because of unanticipated surgical procedures or other unforeseen complications. The decision of when dual antiplatelet therapy can be safely interrupted needs to be individualized for each patient and involves factoring in the type of stent; the location and complexity of the lesion stented; post-stent lesion characteristics; the amount of time since stent placement; and the antiplatelet regimen currently in use, along with its implication for bleeding during the proposed procedure. Having a protocol in place, such as the protocol described in this article, can help guide this decision-making process and avoid confusion and potential error.

Platelet biology and response to antiplatelet therapy in women: implications for the development and use of antiplatelet pharmacotherapies for cardiovascular disease

Women are underrepresented in cardiovascular studies, even as their preponderance in the aging population steadily increases. Although concerns have been raised about the differential benefit of antiplatelet medications for women, the propensity for increased bleeding among women has also been recognized. A better understanding of the factors contributing to the observed sex-related differences in platelet biology is warranted. These factors include differences in the frequency and expression of genetic polymorphisms affecting platelet responsiveness to agonists (with and without antiplatelet therapies), which might be obtained through population-based studies and in large controlled clinical trials; inflammatory marker levels and their influence on atherothrombotic risk, and the role of specific hormones in mediating platelet activation and function. Knowledge gained about these mechanistic factors might inform the development of sex-specific antithrombotic treatment regimens that confer optimized safety and efficacy.

Clopidogrel, a P2Y12 receptor antagonist, potentiates the inflammatory response in a rat model of peptidoglycan polysaccharide-induced arthritis

The P2Y12 receptor plays a crucial role in the regulation of platelet activation by several agonists, which is irreversibly antagonized by the active metabolite of clopidogrel, a widely used anti-thrombotic drug. In this study, we investigated whether reduction of platelet reactivity leads to reduced inflammatory responses using a rat model of erosive arthritis. We evaluated the effect of clopidogrel on inflammation in Lewis rats in a peptidoglycan polysaccharide (PG-PS)-induced arthritis model with four groups of rats: 1) untreated, 2) clopidogrel-treated, 3) PG-PS-induced, and 4) PG-PS-induced and clopidogrel-treated. There were significant differences between the PG-PS+clopidogrel group when compared to the PG-PS group including: increased joint diameter and clinical manifestations of inflammation, elevated plasma levels of pro-inflammatory cytokines (IL-1 beta, interferon (IFN) gamma, and IL-6), an elevated neutrophil blood count and an increased circulating platelet count. Plasma levels of IL-10 were significantly lower in the PG-PS+clopidogrel group compared to the PG-PS group. Plasma levels of platelet factor 4 (PF4) were elevated in both the PG-PS and the PG-PS+clopidogrel groups, however PF4 levels showed no difference upon clopidogrel treatment, suggesting that the pro- inflammatory effect of clopidogrel may be due to its action on cells other than platelets. Histology indicated an increase in leukocyte infiltration at the inflammatory area of the joint, increased pannus formation, blood vessel proliferation, subsynovial fibrosis and cartilage erosion upon treatment with clopidogrel in PG-PS-induced arthritis animals. In summary, animals treated with clopidogrel showed a pro-inflammatory effect in the PG-PS-induced arthritis animal model, which might not be mediated by platelets. Elucidation of the mechanism of clopidogrel-induced cell responses is important to understand the role of the P2Y12 receptor in inflammation.