Treatment options for patients with poor clopidogrel response

The need of a multicomponent guiding approach to personalize clopidogrel treatment

Patients bearing polymorphisms termed CYP2C19 loss of function (LoF) alleles and ABCB1-C3435T may do not properly respond to standard dosage of clopidogrel and have an increased risk of thrombosis. Moreover, co-administration of proton pump inhibitors (PPIs) and clopidogrel may attenuate the antiplatelet effect. The role of pharmacogenetics and PPIs/clopidogrel drug-drug interaction has been extensively investigated in patients with acute coronary syndrome after stent implantation (ACS/PCI), while data in patients undergoing vascular surgery are scarce. Here we have performed a systematic review to evaluate the available literature in such a clinical setting and have discussed the controversies about the use of CYP2C19 pharmacogenetics and platelet function testing to personalize clopidogrel treatment. In addition, we have made a comparison of the literature data with our findings concerning patients eligible for vascular surgery and treated with clopidogrel, in whom we used a combined management based on the CYP2C19 and ABCB1 pharmacogenetic testing with monitoring of therapeutic adherence and PPIs-clopidogrel interaction. Both our data and those produced during both observational studies and randomized clinical trials confirm the validity of pharmacogenetics to personalize clopidogrel treatment and stress the importance to make a drug monitoring considering all the known variables, potentially responsible for treatment failure. However, the American Heart Association and the European Cardiovascular Society recommend against the routine use of clopidogrel pharmacogenetic testing. An update of the international guidelines on antiplatelet therapy, incorporating the evidence related to CYP2C19 pharmacogenetics and PPIs-clopidogrel drug-drug interactions is warranted both in ACS/PCI patients and subjects undergoing vascular surgery.

On-treatment platelet reactivity in the era of new ADP receptor blockers: data from a real-world clinical practice

Objectives: Several studies have questioned the need for platelet function testing in patients treated with new ADP receptor blockers (ADPRB). The aim of this study was to evaluate the prevalence of high on-treatment platelet reactivity (HTPR) among acute ST-elevation myocardial infarction (STEMI) patients treated with newer ADPRB.

Methods: A prospective study enrolling 44 acute previously ADPRB naive STEMI patients (31 men, 13 women) undergoing primary percutaneous coronary intervention (pPCI) was performed. Among the studied population 23 patients received prasugrel and 21 patients received ticagrelor. Antiplatelet response was tested with light transmission aggregometry (LTA) and vasodilator-stimulated phosphoprotein phosphorylation (VASP-P) flow cytometry assay. Samples were taken prior to coronary angiography (sample 1) and on the day after this procedure (sample 2).

Results: The mean platelet aggregation after induction with ADP was 51.7 ± 24.8% in sample 1 and 25.3 ± 20.1% in sample 2. An examination of VASP-P showed a mean platelet reactivity index of 56.8 ± 25.7% in sample 1 and 23.8 ± 23.1% in sample 2, respectively. The study identified 11.4% of patients in sample 2 as ADP receptor blocker non-responders. No significant differences were found between prasugrel-treated to ticagrelor-treated patients.

Conclusions: This pilot study demonstrated HTPR among acute STEMI patients treated with newer ADPRB.

Postoperative Anticoagulation After Neurologic Surgery

Management of anticoagulation and antiplatelet medications after neurosurgery can be complex, especially given that these patients have multiple medical comorbidities. In turn, neurosurgical patients are at high risk for the development of venous thromboembolism after surgery, so neurosurgeons must consider the use of pharmacologic prophylaxis. Developments in endovascular neurosurgery have produced therapies that require close management of antiplatelet medications to prevent postoperative complications. Any of these patient populations may need intrathecal access. This article highlights current strategies for managing these issues in the neurosurgical patient population.

Can Blood Biomarkers Help Predicting Outcome in Transcatheter Aortic Valve Implantation?

Transcatheter aortic valve implantation (TAVI) has become the method of choice for patients with severe aortic valve stenosis, who are ineligible or at high risk for surgery. In this high risk patient population, early and late mortality and rehospitalization rates after TAVI are still relatively high. In spite of recent improvements in procedural TAVI, and establishment of risk models for poor outcome, determining individual risk remains challenging. In this context, current data from several small studies strongly suggest that blood biomarkers of myocardial injury, cardiac mechanical stretch, inflammation, and hemostasis imbalance might play an important role by providing informations on patient risk at baseline, and postprocedural progression of patient clinical conditions from days up to years post-TAVI. Although the role of biomarkers for predicting survival post-TAVI remains to be validated in large randomized studies, implementing biomarkers in clinical practice might improve risk stratification, thereby further reducing TAVI-associated morbidity and mortality.

Ticagrelor overcomes high platelet reactivity in patients with acute myocardial infarction or coronary artery in-stent restenosis: a randomized controlled trial

High on-treatment platelet reactivity (HTPR) is accompanied by an increased risk of adverse outcomes. Direct comparison of the antiplatelet effects between ticagrelor and high-dose clopidogrel has not yet been reported in acute myocardial infarction (AMI) or coronary artery in-stent restenosis (ISR) patients with HTPR. Consecutive patients with AMI or coronary artery ISR treated with standard-dose clopidogrel (75 mg/day) were screened with the VerifyNow assay, defining HTPR as P2Y12 reaction units (PRUs) >208. Of the 102 screened patients, 48 (47.06%) patients with HTPR were randomly assigned to either ticagrelor (180 mg/90 mg twice daily) or high-dose clopidogrel (150 mg/day) for 24 hours. Baseline characteristics and mean PRUs were similar in both groups. After 24 hours, ticagrelor was associated with a significantly lower platelet reactivity than high-dose clopidogrel (44.38 ± 40.26  vs. 212.58 ± 52.34 PRU, P < 0.05). No patient receiving ticagrelor exhibited HTPR, whereas 15 (62.50%) patients after treatment with high-dose clopidogrel remained HTPR (P < 0.05). During the follow-up (mean, 138.42 ± 53.59 days), no patient exhibited a major bleeding event in either treatment group. In conclusion, in patients with AMI or coronary artery ISR exhibiting HTPR after standard clopidogrel treatment, ticagrelor is significantly more effective compared with high-dose clopidogrel in overcoming HTPR.

Contemporary antiplatelet therapy in patients undergoing percutaneous coronary intervention

The proper use of antiplatelet agents in the cardiac catheterization laboratory is important for ensuring optimal results in patients undergoing percutaneous revascularization. Understanding the mechanisms by which these drugs exerts their effects is important for both interventional and non-interventional cardiologists. The effects of these agents on platelet function can be assessed and monitored using a variety of commercially available laboratory assays but so far these tests have not been adopted in routine clinical practice. Currently, aspirin, thienopyridines and glycoprotein IIb/IIIa inhibitors are the primary types of antiplatelet drugs being utilized. The use of these drugs and of several newer antiplatelet drugs in the treatment of patients undergoing percutaneous revascularization in the cardiac catheterization laboratory will be discussed, especially in the light of the recently published guidelines.