Resistance to antiplatelet therapy

Linking triphenylphosphonium cation to a bicyclic hydroquinone improves their antiplatelet effect via the regulation of mitochondrial function

Platelets are the critical target for preventing and treating pathological thrombus formation. However, despite current antiplatelet therapy, cardiovascular mortality remains high, and cardiovascular events continue in prescribed patients. In this study, first results were obtained with ortho-carbonyl hydroquinones as antiplatelet agents; we found that linking triphenylphosphonium cation to a bicyclic ortho-carbonyl hydroquinone moiety by a short alkyl chain significantly improved their antiplatelet effect by affecting the mitochondrial functioning. The mechanism of action involves uncoupling OXPHOS, which leads to an increase in mitochondrial ROS production and a decrease in the mitochondrial membrane potential and OCR. This alteration disrupts the energy production by mitochondrial function necessary for the platelet activation process. These effects are responsive to the complete structure of the compounds and not to isolated parts of the compounds tested. The results obtained in this research can be used as the basis for developing new antiplatelet agents that target mitochondria.

Tongue diagnostic parameters-based diagnostic signature in coronary artery disease patients with clopidogrel resistance after percutaneous coronary intervention

BACKGROUND

Credible diagnostic stratification remains a challenge for coronary artery disease patients with clopidogrel resistance after percutaneous coronary intervention. Tongue diagnostic parameters-based diagnostic signatures might predict clopidogrel resistance.

METHODS

Clinical and tongue diagnostic parameters data were obtained from coronary artery disease patients with clopidogrel resistance after percutaneous coronary intervention patients and then analyzed. Tongue diagnostic parameters-based diagnostic signatures were developed through univariate and multivariate logistic regression analysis. The diagnostic prediction was assessed using a receiver operating characteristic curve.

RESULTS

A total of 101 patients were consecutively identified. Then, tongue diagnostic parameters were identified as significantly associated with clopidogrel resistance diagnosis and were combined with risk factors to develop a model. The receiver operating characteristic curve analysis showed that tongue diagnostic parameters-based diagnostic signatures performed well in diagnosing clopidogrel resistance with an area under the receiver operating characteristic curve value of 0.819.

CONCLUSIONS

This study identified a novel tongue diagnostic parameters-based diagnostic signature to reliably distinguish clopidogrel resistance diagnosis in coronary artery disease patients undergoing percutaneous coronary intervention. Further larger, multicenter prospective studies are desired to validate this model.

Influences of an NR1I2 polymorphism on heterogeneous antiplatelet reactivity responses to clopidogrel and clinical outcomes in acute ischemic stroke patients

Pregnane X receptor (PXR) is a member of nuclear receptor subfamily 1 (NR1I2) that is a transcriptional regulator of several metabolic enzymes involved in clopidogrel metabolism. In this study we identified and evaluated the contributions of single nucleotide polymorphisms (SNPs) in NR1I2 and cytochrome P450 (CYP) 2C19 alleles to clopidogrel resistance (CR) and long-term clinical outcomes in acute ischemic stroke (IS) patients. A total of 634 patients with acute IS were recruited, who received antiplatelet medication (clopidogrel or aspirin) every day and completed a 1-year follow-up. The selected SNPs were genotyped, and platelet function was measured. Modified Rankin Scale (mRS) scores and main adverse cardiovascular and cerebrovascular events (MACCE) were noted to assess the prognosis. We showed that SNPs NR1I2 rs13059232 and CYP2C19 alleles (2*/3*) were related to CR. SNP NR1I2 (rs13059232) was identified as an independent risk factor for the long-term clinical outcomes in the clopidogrel cohorts (P < 0.001), but similar results were not observed in a matched aspirin cohort (P > 0.05). Our results suggest that NR1I2 variant (rs13059232) could serve as biomarker for clopidogrel therapy and individualized antiplatelet medications in the treatment of acute IS patients.

Dose-related effect of aspirin on laboratory-defined platelet aggregation and clinical outcome after coronary stenting

BACKGROUND

Acetylsalicylic acid (aspirin) is widely used in the secondary prevention of coronary artery disease. There is controversy regarding the prevalence of aspirin resistance in patients with coronary artery disease and the effect of dose on resistance. Our primary aims were to determine the degree of platelet responsiveness to aspirin, and to study the influence of dose on platelet inhibition and clinical outcomes after coronary stenting.

METHODS AND RESULTS

We prospectively studied the effect of aspirin on platelet function in 106 stable outpatients 6 months after successful percutaneous coronary angioplasty. Participants were randomized in a double-blind, double-crossover study (80 or 500 mg per day for 6 months). The platelet response to aspirin was determined by 10 micromol/L adenosine-5-diphosphate-induced aggregation with light transmission aggregometry. The clinical outcome was determined by single photon emission computed tomography with Tc-99m, and major adverse cardiac events were recorded (myocardial infarction, death, unstable angina or need for revascularization). In both groups 30.2% of the participants were resistant to aspirin. There was no significant difference between the dose of 80 mg compared to 500 mg aspirin in the incidence of aspirin resistance (P= 0.3). No correlation was found between aspirin resistance and clinical outcome (P= 0.4). Female sex and smoking were strongly associated with aspirin resistance.

CONCLUSION

The frequency of aspirin resistance is not dependent on the dose of aspirin. Female sex and smoking were the strongest predictors of aspirin resistance. Aspirin resistance is not a predictor of poor clinical outcome in patients who received double antiplatelet therapy.

Antiplatelet therapy in percutaneous coronary intervention: a critical review of the 2007 AHA/ACC/SCAI guidelines and beyond

Antiplatelet therapy is a mainstay in the treatment of patients who have undergone percutaneous coronary intervention (PCI). Although the 2007 PCI treatment guidelines were published by the American College of Cardiology, the American Heart Association, and the Society for Cardiovascular Angiography and Interventions, new clinical evidence has emerged, expanding our understanding of antiplatelet use and potentially affecting the treatment guidelines. For example, clinical trial results prompted a Science Advisory to recommend that dual therapy with aspirin and clopidogrel be used for longer periods-up to 1 year in patients who receive bare metal stents and at least 1 year in patients receiving drug-eluting stents. New trial results have also emerged regarding the use of glycoprotein IIb/IIIa antagonists such as abciximab, eptifibatide, and tirofiban. This article reviews the current recommendations for antiplatelet therapy in PCI patients, recent trial results, newly developed agents, ongoing clinical trials, and the future direction of antiplatelet therapy in patients who undergo PCI.

Facts and controversies of aspirin and clopidogrel therapy

Because of the central role of platelets in mediating ischemic events, antiplatelet agents are critical components of atherothrombosis prevention. Given their robust safety and efficacy profiles, aspirin and clopidogrel are consistently recommended by evidence-based treatment guidelines. Despite these recommendations, controversies surrounding the appropriate application of aspirin and clopidogrel remain. Questions of appropriate dosing, length of therapy, and use of combination therapy are most pressing, and considerable debate exists regarding the variability of response to antiplatelet therapy, including the definition, measurement, and clinical relevance of responsiveness. This review discusses the facts and controversies surrounding the use of aspirin and clopidogrel. Overall, despite the existing controversies, antiplatelet therapy with aspirin and/or clopidogrel remains a proven and essential therapeutic tool for safe and effective management of atherothrombotic risk in specific clinical settings.

Destination therapy: does progress depend on left ventricular assist device development?

The role of therapy using mechanical circulatory support devices has evolved rapidly over the last two decades. New developments in the field achieved smaller adverse events, but, currently, only minor improvements in survival were observed in published observational data. The authors discuss the development of mechanical circulatory support devices as a "destination therapy" option for patients who have end-stage heart failure and are ineligible for heart transplantation as it relates to left ventricular assist device development.

Clopidogrel resistance

Clopidogrel resistance has been used as one of the terms employed in the literature to describe different degrees of ex vivo low platelet inhibition after clopidogrel administration. In addition to the diverse nomenclature, the characterisation of clopidogrel resistance has also been problematic because different authors have given different definitions. The mechanisms responsible for this decreased platelet response are not yet clearly defined, some hypotheses have been put forward but not yet demonstrated. Although there have been no large prospective studies demonstrating that the degree of platelet inhibition is directly related to clinical outcomes, several recent studies and reports have shown an association between less platelet inhibition and more adverse events after percutaneous coronary interventions with clopidogrel therapy suggesting that clopidogrel resistance may be a marker for increased risk of recurrent cardiovascular events. Larger scale investigations are needed to support these findings.

Long-term care after percutaneous coronary intervention: focus on the role of antiplatelet therapy

Arterial wall injury caused by percutaneous coronary intervention (PCI) triggers transient platelet activation and mural thrombosis; these effects are superimposed on the preexisting platelet hyperreactivity associated with underlying atherothrombosis. Platelet activation has been implicated in the major complications of PCI: acute and subacute thrombosis and restenosis. Antithrombotic and anticoagulant therapy minimizes thrombotic complications after PCI. Aspirin plus a thienopyridine (ticlopidine or clopidogrel) is more effective than aspirin plus heparin and extended warfarin therapy in preventing periprocedural ischemic events and subsequent stent thrombosis and results in less major and minor bleeding. Dual antiplatelet therapy with aspirin and clopidogrel (the preferred thienopyridine because of its superior hematologic safety) is recommended for at least 4 weeks to prevent subacute stent thrombosis with bare-metal stents and 3 to 6 months to prevent late-stent thrombosis with drug-eluting stents. Coronary atherothrombosis is a diffuse vascular disease, and reduction of the risk of future ischemic events requires strategies that extend beyond the focal treatment of stenotic lesions. Optimal long-term care after PCI requires aggressive systemic pharmacotherapy (antiplatelet agents, statins, beta-blockers, and angiotensin-converting enzyme Inhibitors) in conjunction with therapeutic lifestyle changes (smoking cessation, weight reduction, dietary measures, and exercise). In this context, dual antiplatelet therapy (aspirin plus clopidogrel) is recommended for at least 12 months after PCI for prophylaxis of future atherothrombotic events.