Determination of platelet response to dual anti-platelet therapy in percutaneous coronary intervention (PCI) patients

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Determination of platelet response to dual anti-platelet therapy in percutaneous coronary intervention (PCI) patients

 

Author: Mak, Hau Man
Title: Determination of platelet response to dual anti-platelet therapy in percutaneous coronary intervention (PCI) patients
Degree: M.Sc.
Year: 2012
Subject: Coronary heart disease -- Treatment.
Blood platelets.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: 76 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2520216
URI: http://theses.lib.polyu.edu.hk/handle/200/6559
Abstract: Coronary artery disease (CAD) is the most common disease worldwide. Patients undergoing percutaneous coronary intervention (PCI) for CAD are treated with dual anti-platelet agents such as aspirin and clopidogrel to reduce the risk of coronary thrombosis. However, patients' response to this anti-platelet therapy has been variable and the inadequate suppression of platelet activity is observed an important risk factor for future coronary thrombosis event. Many previous studies had used light transmission aggregometry to investigate the effect of antiplatelet agent and platelet function. Aspirin Resistance and Adverse Clinical Events in Patients with Coronary Artery Disease are only very few studies on the effect of antiplatelet agent using whole blood transmission aggregometry (WBA) assay in PCI patients. Here, we described our experience in using WBA assay to study the response of platelet to dual anti-platelet agents. The platelet aggregation response is recording the electrical resistance between the two electrodes. The assay performance of WBA will be bench marked against that of Vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, VASP phosphorylation assay is a method for measuring adenosine diphosphate (ADP) pathway activation after clopidogrel therapy. All PCI patients took a 300 mg loading dose of clopidogrel and then maintained with 75mg clopidogrel plus 160 mg aspirin (acetylsalicylic acid, ASA). Samples from 23 healthy subjects, were used to derive the cutoff aspirin and clopidogrel resistance (the mean ±2SD) in WBA assay. WBA impedance >4Ω after arachidonic acid and >9Ω after collagen as an agonists were denoted as aspirin resistance; and impedance >3Ω after ADP as an agonist denoted as clopidogrel resistance. Of 61 PCI patients, 0% (n=0) patient was aspirin resistance by using arachidonic acid as platelet agonist. 30% (n=18) patients were clopidogrel resistance by using ADP as platelet agonist. Using collagen as platelet agonist showed 74% (n=45) patients sensitive to aspirin.
With VASP phosphorylation assay, using a cut off of as recommended by international studies for optimal cardioprotection; 72% (n=44) of the patients would be defined as clopidogrel resistance. The correlation coefficient between ADP-WBA assay and VASP phosphorylation assay was only 0.414 (P=0.001). In conclusion, WBA assays showed that prevalence of clopidogrel resistance was 30%. No patients were found aspirin resistance by arachidonic acid-WBA. 26% of PCI patients in collagen-WBA assay were defined as aspirin resistance. On the other hand, VASP has identified a higher number of patients with clopidogrel resistance (72%). To some extent, the discordance can be related to the different criteria used to define the cut-off of antiplatelet resistance in these two assays. The relative utility of one assay over the other in the clinical prediction of risk of coronary events can be determined by a large follow- up study.

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