Clinical Utility of the Rapid Platelet Function Analyzer following OPCAB Surgery

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The purpose of this study is to evaluate the clinical use of a platelet function point-of-care test in patients undergoing Off-Pump Coronary Artery Bypass (OPCAB) surgery. One of the major complications of coronary artery bypass graft surgery is occlusion of vein grafts within the immediate postoperative period that is largely related to platelet aggregation. Aspirin is considered the drug of choice for prophylaxis against early saphenous vein graft closure. Advances in cardiac surgical procedures, particularly myocardial revascularization without the use of a cardiopulmonary bypass (CPB) pump, have raised new questions concerning graft patency in the early postoperative period and the effectiveness of aspirin therapy. Recent studies suggest that OPCAB surgery may result in a "hypercoagulable state" which can lead to acute graft thrombosis despite the standard administration of aspirin during the immediate postoperative period. Even though alterations in platelet function following OPCAB surgery have not been clearly defined, many cardiac surgeons believe that an increased level of platelet activation may play a significant role in the acute graft thrombosis associated with OPCAB surgery despite the routine administration of aspirin. As a result, many cardiac surgeons have started administering the combination of clopidogrel and aspirin during the immediate postoperative period. However, it is currently unknown what effects the administration of clopidogrel with aspirin will have on platelet function in the immediate postoperative period. This clearly demonstrates the need for controlled trials to not only evaluate the safety of the combination of clopidogrel and aspirin in the immediate postoperative period, but also to document the temporal effect of the inhibition of specific but distinct platelet signaling pathways as well as OPCAB surgery itself on platelet function. Flow cytometry can be used to comprehensively evaluate the level of platelet activation in the presence and absence of various exogenous platelet agonists. This type of testing is very accurate and sensitive, but the technical challenges, costs, and time involved prevent it from being a clinically useful tool. Thus, point-of-care (POC) tests have recently become available as an alternative for measuring platelet function in a variety of settings. The Rapid Platelet Function Analyzer (RPFA), in particular, can be used to evaluate the level of platelet activation in the presence and absence of various exogenous platelet agonists similar to flow cytometry. However, the accuracy of this POC test has not been evaluated in patients during the immediate postoperative period following cardiac surgery, and thus the clinical applicability of its results are still in question. We hypothesize that the results from the RPFA point-of-care test will correlate with platelet function results obtained utilizing flow cytometry in patients undergoing OPCAB surgery. To test this hypothesis, we plan to determine the effect of clopidogrel and aspirin administration on ex vivo platelet function in response to ADP, metallic cations and propyl gallate (TXA2-dependent agonist) and TRAP (thrombin receptor-dependent agonist; ADP receptor and TXA2-independent agonist) using flow cytometry and a RPFA. Comparison of the results obtained by flow cytometry and the RPFA will allow us to determine the clinical utility of the RPFA system as a point-of-care test to assess platelet function following off-pump coronary artery bypass surgery. This study will determine if a point-of-care test (RPFA) can measure the level of platelet activation following OPCAB with the same accuracy as flow cytometry. If so, the utilization of a POC test could have an immediate impact on the postoperative care of patients with coronary artery disease undergoing coronary revascularization with OPCAB surgery, specifically by providing real time data to guide the administration of antiplatelet therapy during this critical time period. It could also provide a viable, cost effective alternative to flow cytometry for future research endeavors in this area.
Effective start/end date7/1/046/30/05


  • American College of Clinical Pharmacy Foundation: $15,000.00


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