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Clinical efficacy of the antiplatelet drug clopidogrel is hampered by its variable biotransformation into the active metabolite (1,2). The variability in the clinical response to clopidogrel treatment has been attributed to genetic factors, but the specific genes and mechanisms underlying clopidogrel bioactivation remain unclear. Using in vitro metabolomic profiling techniques, we identified paraoxonase-1 (PON1) as the crucial enzyme for clopidogrel bioactivation, with its common Q192R polymorphism determining the rate of active metabolite formation. We tested the clinical relevance of the PON1 Q192R genotype in a population of individuals with coronary artery disease who underwent stent implantation and received clopidogrel therapy. PON1 QQ192 homozygous individuals showed a considerably higher risk than RR192 homozygous individuals of stent thrombosis, lower PON1 plasma activity, lower plasma concentrations of active metabolite and lower platelet inhibition. Thus, we identified PON1 as a key factor for the bioactivation and clinical activity of clopidogrel. These findings have therapeutic implications and may be exploited to prospectively assess the clinical efficacy of clopidogrel., Antiplatelet therapy with the ADP P2Y12 receptor antagonist clopidogrel is recommended by current clinical practice guidelines to prevent atherothrombotic events in patients with coronary artery disease (CAD) undergoing percutaneous coronary [...]

A study was conducted to evaluate the efficacy of platelet function tests in predicting clinical outcome in patients undergoing coronary stent implantation. Results indicated that the predictive accuracy of the tests was only modest and thus were not accurate predictors.

Postoperative coagulopathic bleeding is common in cardiac surgery and associated with increased morbidity and mortality. Platelet function is affected by multiple factors, including patient and procedural characteristics. Point-of-care (POC) multiple electrode aggregometry (MEA) can rapidly detect and quantify platelet dysfunction and could contribute to optimal patient blood management. In patients undergoing CABG and heart valve surgery platelet function was assessed using POC MEA at four different perioperative timepoints in response to stimulation with four specific receptor agonists (ADP, AA, COL, TRAP). Postoperative bleeding was recorded during 24 h after surgery. Regression analyses were performed to establish associations between perioperative platelet function and postoperative blood loss. Ninety-nine patients were included in the study. Fifty-nine patients (60%) were on antiplatelet therapy (APT) at time of surgery. ADP- and AA-induced platelet aggregation declined during CPB and after decannulation from CPB, with a maximum decrease of 55% for ADP (35 vs. 77 AU at baseline; P < 0.001) and 78% for ASPI (14 vs. 64 AU at baseline; P < 0.001). A linear relationship was present between ADP-induced platelet aggregometry at baseline and postoperative blood loss (r = −0.249; P = 0.015). In aspirin users, the maximum decline in platelet function between baseline and CPB decannulation was related to postoperative blood loss (r = 0.308; P = 0.037). In multivariate analysis, a reduced ADP platelet function prior to surgery remained associated with postoperative blood loss (r = −0.239; P = 0.012). Reduced ADP-induced platelet aggregation at baseline is associated with increased postoperative blood loss in high-risk cardiac surgery patients. [ABSTRACT FROM AUTHOR]

Purpose: The POPular Risk Score was developed for the selective intensification of P2Y12 inhibitor treatment with prasugrel instead of clopidogrel in patients undergoing non-urgent percutaneous coronary intervention (PCI) with stent implantation. This score is based on platelet reactivity (VerifyNow P2Y12 assay), CYP2C19 genotyping, and clinical risk factors. Our aim was to determine if the use of this score in clinical practice is associated with a reduction in thrombotic events without increasing bleeding events. Methods: In a single-center prospective cohort study, patients with a high risk score were treated with prasugrel and patients with a low risk score with clopidogrel. The risk score–guided cohort was compared with a historic cohort of clopidogrel-treated patients. The endpoint consisted of all-cause death, myocardial infarction, stroke, or stent thrombosis during 1 year of follow-up. TIMI major and minor bleeding events were also analyzed. Results: The guided cohort contained 1127 patients, 26.9% of whom were switched to prasugrel according to the POPular Risk Score. The historic cohort contained 893 patients. The incidence of the combined thrombotic endpoint was significantly lower in the guided cohort as compared with the historic cohort (8.4% versus 3.7%, p < 0.001). This strategy was safe with respect to bleeding (4.0% versus 1.3%, p < 0.001, for TIMI major or minor bleeding). Results were comparable after multivariate and propensity score matched and weighted analysis. Conclusion: Selective intensification of P2Y12 inhibitor treatment after non-urgent PCI based on the POPular Risk Score is associated with a reduction in thrombotic events without an increase in bleeding events. [ABSTRACT FROM AUTHOR]

Antiplatelet therapy plays a pivotal role in patients with an ST-segment elevation myocardial infarction (STEMI) to prevent further atherothrombotic events, such as stent thrombosis. Although the risk of stent thrombosis is highest in the first hours after primary percutaneous coronary intervention (pPCI), little is known about when an adequate level of platelet inhibition is achieved following a clopidogrel or ticagrelor loading dose in STEMI patients. Patients presenting with STEMI in whom pPCI was performed and who were loaded with 600 mg clopidogrel or 180 mg ticagrelor were eligible for enrolment in this nonrandomized, open label, single-center study. Platelet reactivity was measured before PCI, 6 and 24 hours after loading dose and after 2, 7, and 14 days, using the VerifyNow P2Y12 assay as well as 20 μmol/L adenosine diphosphate stimulated light transmittance aggregometry (LTA). We analyzed the time until a VerifyNow result of < 236 P2Y12 reaction units or LTA maximum platelet aggregation of < 64.5% was reached. A total of 28 patients were participated in this study. Platelet reactivity dropped below the high platelet reactivity cutoff level after 11.4 (VerifyNow) and 5.7 (LTA) hours in patients who were loaded with clopidogrel, and after 2.4 (VerifyNow) and 3.9 (LTA) hours in patients who were loaded with ticagrelor. Despite the administration of a clopidogrel or ticagrelor loading dose, it still takes multiple hours (2-11) to reach adequate platelet inhibition in STEMI patients. This might indicate the need for additional antiplatelet therapy in the first hours after loading in patients undergoing pPCI with stenting. [ABSTRACT FROM AUTHOR]