Preoperative Antiplatelet Therapy and Bleeding Risk in Patients Undergoing Off-Pump Coronary Artery Bypass Grafting: A Fine Balance

Antiplatelet agents are classified according to their mechanism of action as cyclooxygenase (COX) inhibitors, P2Y12 receptor blockers, glycoprotein IIb/IIIa blockers, thrombin receptor antagonists, and phosphodiesterase inhibitors. Aspirin irreversibly acetylates COX-1 to inhibit thromboxane-A2 production and reduce platelet aggregation. Metabolites of clopidogrel irreversibly inhibit P2Y12 receptors on the platelet membrane, reducing platelet aggregation and providing more prevention from ischemic stroke, myocardial infarction, or vascular death than aspirin, in patients with atherosclerotic vascular disease (recent ischemic stroke, recent myocardial infarction, or symptomatic peripheral arterial disease). The “new” generation P2Y12 receptor inhibitor ticagrelor was evaluated in the Platelet Inhibition and Patient Outcomes trial which demonstrated a significantly reduced rate of death from vascular causes, myocardial infarction, and stroke in patients with acute coronary syndrome (ACS), with or without ST-segment elevation, compared with clopidogrel treatment. Similarly, in the Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition with Prasugrel– Thrombolysis in Myocardial Infarction (TRITON-TIMI) 38, prasugrel had a faster, more predictable and greater antiplatelet effect compared with clopidogrel in patients with ACS undergoing percutaneous coronary intervention, at the expense of increased rates of fatal and nonfatal bleeding events. Novel thieno(2,3b) pyridine derivatives, currently being tested, show greater activity than clopidogrel, a more effective inhibition of collagen-induced aggregation and a greater activity when used in combination with aspirin. Since its first performance by Kolessov and the popularization by Favaloro, coronary artery bypass grafting (CABG) has become the leading heart operation performed today. There is an ongoing debate on which of the currently methods used “on-pump” or “off-pump” CABG have the most favorable outcomes. The criteria that determine which method will be followed each time may vary among different medical centers. However, studies have reported different advantages and disadvantages when comparing the 2 procedures. For example, on-pump CABG is related to more complete revascularization, increased formation of distal anastomosis, increased long-term survival, is more familiar to the majority of surgeons, and it is considered also an appropriate option in demanding situations. Off-pump CABG, on the other hand, is regarded as technically demanding and requires a prolonged learning curve; however, it has been associated with decreased levels of post-CABG inflammatory cytokines, reduced occurrence of postsurgical microemboli, and lower morbidity. Even so, no single randomized trial has been able to prove off-pump CABG superior to on-pump CABG regarding hard outcomes such as myocardial infarction, stroke, or death. In this issue of Angiology, Cheng et al evaluated the effects of preoperative antiplatelet therapy on the risk of bleeding and ischemia, in a retrospective study of 2012 patients undergoing off-pump CABG. There was an association between age, preoperative hemoglobin and creatinine, postoperative thrombocytopenia, as well as the timing of discontinuation of dual antiplatelet therapy (DAPT), with postoperative bleeding following CABG. In particular, increased postoperative bleeding risk was observed when DAPT was discontinued <3 days before off-pump CABG and this was accompanied by a greater mortality risk. Hypertension, diabetes, hemoglobin, graft number, thrombocytopenia, and male sex were independent predictors of perioperative myocardial ischemia. Subgroup analysis revealed no direct association between bleeding events and myocardial ischemia, despite the intriguing relationship observed between low hemoglobin and perioperative ischemia. The authors are to be congratulated for their attempt to define the optimal time window switching from DAPT to single antiplatelet therapy prior to CABG, a common clinical dilemma.