1. INTRODUCTION

Aspirin and clopidogrel are the two most commonly used antiplatelets in patients undergoing coronary artery bypass grafting (CABG) surgery. Aspirin is administered early after CABG to reduce the risk of death and organ ischaemia of the heart, brain, kidneys and gastrointestinal tract.1 The early administration of aspirin after CABG surgery also has significantly improved the patency of vein grafts without increasing the risk of bleeding.2 Aspirin inhibits the transformation of arachidonic acid into thromboxane A2 (TxA2) by irreversibly acetylating the platelet cyclooxygenase (COX) enzyme. Due to its chemical instability, TxA2 is then converted to stable and inactive thromboxane B2 (TxB2), and its metabolite 11-dehydroTxB2, which can be detected in the urine.
Dual antiplatelet therapy with aspirin and clopidogrel is associated with a reduced risk of thrombotic complications following acute coronary syndrome (ACS).3 Clopidogrel is adenosine diphosphate (ADP) receptor antagonist that irreversibly inhibits by binding to the platelet P2Y12 receptor. Dual antiplatelet therapy leads to reduced all-cause mortality and improved vein graft patency, and their effects are more significant in patients with ACS undergoing CABG surgery.4,5
Antiplatelet resistance in some patients has been linked to early graft failure and identified to be due to the poor responsiveness of these groups of patients to the administered antiplatelet agents.6 A variety of tests are available for the assessment of antiplatelet resistance, however, these tests are neither equally precise nor correlate among themselves.7 The systematic review aims to explore the current practice, application of assessment methods and the effects of antiplatelet resistance in patients undergoing CABG surgery.