Evolving role of platelet function testing in coronary artery interventions

Effect of prediabetes on asprin or clopidogrel resistance in patients with recent ischemic stroke/TIA

OBJECTIVE

Diabetes mellitus (DM) had been discovered as an independent risk factor for high on-treatment platelet reactivity (HPR) in patients with ischemic stroke. However, studies on the relationship between prediabetes and the occurrence of HPR remain scarce. This study is aimed at clarifying the association between prediabetes and HPR among patients with recent ischemic stroke or transient ischemic stroke (TIA).

METHODS

Patients with ischemic stroke or TIA within 90 days after onset were recruited consecutively. All patients were divided into three groups: DM, prediabetes, and normal glucose tolerance according to fasting glucose, HbA1c, or OGTT. Three months later, all patients were performed platelet aggregation inhibition test and screened for high on-treatment platelet reactivity. The effect of prediabetes on HPR was analyzed in a multivariable logistic regression model.

RESULTS

This study recruited 237 patients with ischemic stroke or TIA, including 57 cases with prediabetes, 108 with DM, and 72 with normal glucose tolerance. Aspirin and/or clopidogrel resistance was discovered in 28 cases among prediabetes group, which was significantly more frequent than normal glucose tolerance group(49.1% versus 33.3%, P = 0.046). After adjusting for confounding factors, prediabetes was found as an independent risk factor for high on-treatment platelet reactivity (HPR) among patients with recent ischemic stroke or TIA (odds ratio 2.92; 95% CI, 1.29 to 6.63, P = 0.01).

CONCLUSIONS

Prediabetes was an independent risk factor for high on-treatment platelet reactivity in patients with recent ischemic cerebrovascular disease. Patients with prediabetes should be highlighted for the efficacy test of antiplatelet drugs.

Aspirin Resistance: Cardiovascular Risk Game Changer

BACKGROUND

Aspirin (ASA) is the most used medication on the globe. ASA is a primary pillar of the secondary prevention of cardiovascular atherothromboembolic events. However, a fraction of the population does not respond to ASA as expected in a unique phenomenon called ASA resistance. Multiple mechanisms were described and studied in the literature to explain this phenomenon.

AREA OF UNCERTAINTY

ASA resistance is an interesting phenomenon that is worth studying and reviewing. Mechanisms behind this resistance are various and although the rarity of some, it is crucial for the modern health provider to be aware of such phenomenon and its possible explanations to provide more efficient preventive cardiology practice. Our study aimed to review and conclude the evidence behind ASA resistance and its implication on the cardiovascular health.

DATA SOURCES

We searched databases like PubMed, EMBASE, Ovid by midline, and Google Scholar for published articles and abstracts.

RESULTS

Our systemic search revealed more than 100 articles in relation to ASA resistance. We selected 40 articles, which were relevant for this review. Various mechanisms were described in the literature, with few of them very well documented and understood. Main mechanisms include medication nonadherence, interaction with proton pump inhibitors, esterase-mediated ASA inactivation, post-coronary artery bypass grafting (CABG) MRP-4-mediated ASA consumption, cyclooxygenase-1 (COX-1) polymorphisms, high platelet turnover-associated regeneration of platelet COX-1, and the documented platelet ability of de novo COX-1 synthesis in response to thrombin and fibrinogen.

CONCLUSION

Multiple mechanisms of ASA resistance were described in the literature. Awareness of such interaction is important for medical practitioners. Bottom line, further studies and reviews are needed to further study this phenomenon and its implication on the cardiovascular health and hence reaching a valid evidence-based conclusion that might change the practice and improve the patient preventive health care.

Effects of Ramadan fasting on aspirin resistance in type 2 diabetic patients

Aims

Ramadan fasting (RF) may affect aspirin resistance. We conducted this study in patients with cardiovascular risk (CVR) factors to assess the effect of RF on aspirin resistance and explore whether type 2 diabetes mellitus (DM) would influence this effect.

Methods

A total of 177 stable patients with ≥2 CVR factors were recruited. All patients observed RF and were taking aspirin. Physical exam and standard biological tests including glycaemia and serum lipids data were performed before Ramadan (Pre-R), at the last week of Ramadan (R) and four weeks after the end of Ramadan (Post-R). In the same visits caloric intake was calculated and platelet reactivity to aspirin was assessed using Verify Now point-of-care assay.

Results

In the overall population, there was no significant change in absolute aspirin reaction unit (ARU) values and in metabolic parameters. In DM patients (n = 127), ARU change from Pre-R values was+19.7 (p = 0.01) and +14.4 (p = 0.02) respectively at R and Post-R. During Ramadan, glycaemia, triglycerides, and cholesterol levels increased significantly and returned to Pre-R values thereafter. These changes were not observed in non-DM patients.

Conclusions

During RF aspirin resistance increased only in DM patients. This effect persisted one month after Ramadan. Simultaneous alteration of glycemic control and increase of serum lipids levels could potentially be a favorable factor.

Study registration

The protocol was registered at clinicaltrials.gov under: NCT02720133.

Effects of Ramadan fasting on platelet reactivity in diabetic patients treated with clopidogrel

Background

The effects of Ramadan fasting (RF) on clopidogrel antiplatelet inhibition were not previously investigated. The present study evaluated the influence of RF on platelet reactivity in patients with high cardiovascular risk (CVR) in particular those with type 2 diabetes mellitus (DM).

Methods

A total of 98 stable patients with ≥2 CVR factors were recruited. All patients observed RF and were taking clopidogrel at a maintenance dose of 75 mg. Clinical findings and serum lipids data were recorded before Ramadan (Pre-R), at the last week of Ramadan (R) and 4 weeks after the end of Ramadan (Post-R). During each patient visit, nutrients intakes were calculated and platelet reactivity assessment using Verify Now P2Y12 assay was performed.

Results

In DM patients, the absolute PRU changes from baseline were +27 (p = 0.01) and +16 (p = 0.02) respectively at R and Post-R. In addition, there was a significant increase of glycemia and triglycerides levels with a significant decrease of high-density lipoprotein. In non DM patients there was no significant change in absolute PRU values and metabolic parameters. Clopidogrel resistance rate using 2 cut-off PRU values (235 and 208) did not change significantly in DM and non DM patients.

Conclusions

RF significantly decreased platelet sensitivity to clopidogrel in DM patients during and after Ramadan. This effect is possibly related to an increase of glycemia and serum lipids levels induced by fasting.

Trial registration

Clinical Trials.gov NCT02720133. Registered 24 July 2014.Retrospectively registered.

The Personalization of Clopidogrel Antiplatelet Therapy: The Role of Integrative Pharmacogenetics and Pharmacometabolomics

Dual antiplatelet therapy of aspirin and clopidogrel is pivotal for patients undergoing percutaneous coronary intervention. However, the variable platelets reactivity response to clopidogrel may lead to outcome failure and recurrence of cardiovascular events. Although many genetic and nongenetic factors are known, great portion of clopidogrel variable platelets reactivity remain unexplained which challenges the personalization of clopidogrel therapy. Current methods for clopidogrel personalization include CYP2C19 genotyping, pharmacokinetics, and platelets function testing. However, these methods lack precise prediction of clopidogrel outcome, often leading to insufficient prediction. Pharmacometabolomics which is an approach to identify novel biomarkers of drug response or toxicity in biofluids has been investigated to predict drug response. The advantage of pharmacometabolomics is that it does not only predict the response but also provide extensive information on the metabolic pathways implicated with the response. Integrating pharmacogenetics with pharmacometabolomics can give insight on unknown genetic and nongenetic factors associated with the response. This review aimed to review the literature on factors associated with the variable platelets reactivity response to clopidogrel, as well as appraising current methods for the personalization of clopidogrel therapy. We also aimed to review the literature on using pharmacometabolomics approach to predict drug response, as well as discussing the plausibility of using it to predict clopidogrel outcome.

The role of Glycoprotein IIb/IIIa inhibitors in acute coronary syndromes and the interference with anemia

The role played by glycoprotein (GP) IIb/IIIa inhibitors (GPI) has continuously evolved until the most recent Guidelines whereby they were stepped down from class I to class II recommendation for treating acute coronary syndromes (ACS). GPI compete with a wider use of ADP inhibitors and novel anticoagulant drugs although GPI use has greatly narrowed. However, GPI may still have a role. Several criteria were proposed to define post-PCI anemia which is strictly related to bleeding and transfusion. In ACS, it should be important to define anemia in comparative terms versus baseline levels: ≥ 15% of red blood cell decrease should be a practical cut-off value. If one wishes to concentrate on hemoglobin (Hb), a≥2g/dl Hb decrease from baseline should be considered. It is important to recognize post-PCI anemia in the setting of ACS. There are sub-populations exposed to short-term hemorrhagic and/or long-term ischemic risks. Ischemic and hemorrhagic risks need to be carefully evaluated along with thrombocytopenia and its prognostic significance in order to put all these blood and rheological parameters into a clinically oriented perspective on which therapeutical decisions should be based. Definition of high risk procedures (complexity, angiographic characteristics and patient's risk profile, regardless whether STEMI or NSTEMI) may help selecting GPI. There are positive elements in GPI use: efficacy, rapid onset and reversibility of action, absence of pharmacogenomic variability, pharmacoeconomic considerations and the possibility of intracoronary administration. All these elements should be evaluated when selecting these agents for therapeutics.

Coadministration of ticagrelor and ritonavir: Toward prospective dose adjustment to maintain an optimal platelet inhibition using the PBPK approach

Ticagrelor is a potent antiplatelet drug metabolized by cytochrome (CYP)3A. It is contraindicated in patients with human immunodeficiency virus (HIV) because of the expected CYP3A inhibition by most protease inhibitors, such as ritonavir and an increased bleeding risk. In this study, a physiologically based pharmacokinetic (PBPK) model was created for ticagrelor and its active metabolite (AM). Based on the simulated interaction between ticagrelor 180 mg and ritonavir 100 mg, a lower dose of ticagrelor was calculated to obtain, when coadministered with ritonavir, the same pharmacokinetic (PK) and platelet inhibition as ticagrelor administered alone. A clinical study was thereafter conducted in healthy volunteers. Observed PK profiles of ticagrelor and its AM were successfully predicted with the model. Platelet inhibition was nearly complete in both sessions despite administration of a fourfold lower dose of ticagrelor in the second session. This PBPK model could be prospectively used to broaden the usage of ticagrelor in patients with ritonavir-treated HIV regardless of the CYP3A inhibition.

Platelet function testing to predict hyporesponsiveness to clopidogrel in patients with chest pain seen in the emergency department

Background

A dual antiplatelet regimen has been shown to reduce the risk of major adverse cardiovascular events after percutaneous coronary intervention. However, there is little information available on inhibition of platelet aggregation in patients with a prior coronary stent presenting with chest pain. This study evaluated the prevalence of hyporesponsiveness to clopidogrel and factors associated with this in patients presenting to our emergency department with chest pain who had previously undergone coronary stent placement and were prescribed dual antiplatelet therapy.

Methods

Responsiveness to clopidogrel was evaluated in a cohort of 533 consecutive stented patients presenting to the emergency department with chest pain. P2Y12 reaction units (PRU) and percent P2Y12 inhibition with clopidogrel were measured in all patients. Of 533 patients, 221 (41.6%) had PRU ≥ 230. A multivariate logistic regression model was used to determine the relationship between hyporesponsiveness to clopidogrel (defined as PRU ≥ 230) and several potential risk factors, ie, gender, age, race, type 1 or type 2 diabetes, hypertension, smoking, chronic renal failure, and obesity.

Results

There was a greater risk of hyporesponsiveness in African Americans than in non-African American patients (adjusted odds ratio [OR] = 2.165), in patients with type 2 diabetes than in those without (adjusted OR = 2.109), and in women than in men (adjusted OR = 1.813), as well as a greater risk of hyporesponsiveness with increasing age (adjusted OR = 1.167 per decade).

Conclusion

There was a high prevalence of hyporesponsiveness to clopidogrel in patients presenting with chest pain and a prior coronary stent. Non-insulin-dependent diabetes mellitus and African American race were the strongest predictors of hyporesponsiveness to clopidogrel, followed by gender and age.

Brodde M. State of the art in platelet function testing

Platelets perform many functions in hemostasis but also in other areas of physiology and pathology. Therefore, it is obvious that many different function tests have been developed, each one conceived and standardized for a special purpose. This review will summarize the different fields in which platelet function testing is currently in use; diagnostics of patients with bleeding disorders, monitoring patients' response to anti-platelet therapy, monitoring in transfusion medicine (blood donors, platelet concentrates, and after transfusion), and monitoring in perioperative medicine to predict bleeding tendency. The second part of the review outlines different methods for platelet function testing, spanning bleeding time, and platelet counting as well as determining platelet adhesion, platelet secretion, platelet aggregation, platelet morphology, platelet signal transduction, platelet procoagulant activity, platelet apoptosis, platelet proteomics, and molecular biology.

P2Y12 Receptor Inhibitors in Acute Coronary Syndromes: What Is New on the Horizon?

Dual antiplatelet therapy with aspirin and a P2Y₁₂ receptor inhibitor represents the cornerstone therapy for patients with acute coronary syndromes or undergoing percutaneous interventions, leading to a reduction of subsequent ischemic events. Variable response to clopidogrel has received close attention, and pharmacokinetic, pharmacodynamic, and pharmacogenomic factors have been identified as culprits. This led to the introduction of newer, potentially safer, and more effective antiplatelet agents (prasugrel and ticagrelor). Additionally, several point-of-care assays of platelet function have been developed in recent years to rapidly screen individuals on antiplatelet therapy. While the routine use of platelet function testing is uncertain and not currently recommended, it may be useful in instances when the degree of platelet inhibition may be uncertain such as high-risk patients undergoing percutaneous coronary intervention or when there may be a suspected pharmacodynamic interaction with other drugs. The current paper focuses on the P2Y₁₂ receptor inhibitors and their pharmacogenetics and indications in patients with acute coronary syndromes or receiving percutaneous coronary interventions as well as the applicability of platelet function testing in this clinical context.

Is There Still a Role for Glycoprotein IIb/IIIa Antagonists in Acute Coronary Syndromes?

The role played by glycoprotein (GP) IIb/IIIa inhibitors has continuously evolved from the initial introduction in mid 90 s until the most recent guidelines for treating acute coronary syndromes, and competed with a wider use of ADP inhibitors and novel anticoagulant drugs, to the extent that they stepped down from class I to class II recommendation in the routine setting of acute coronary syndromes. As a consequence, GP IIb/IIIa use was greatly narrowed. The purpose of this review is to define the roles that GP IIb/IIIa inhibitors may still have in acute ischemic settings by explaining why in high risk patients they might be preferable and/or whether they might be added to ADP inhibitors also emphasizing the underlying mechanistic actions. It is concluded that there might be a more extensive use of GP IIb/IIIa inhibitors in patients presenting with acute coronary syndromes, strictly based on the definition for a high risk procedure: complexity, angiographic characteristics and patient's risk profile, regardless whether STEMI or NSTEMI. The positive elements one should appreciate in GP IIb/IIIa inhibitors are: efficacy, rapid onset and reversibility of action, absence of pharmacogenomic variability, pharmacoeconomic considerations and the possibility of intracoronary administration.