We read with great interest the article of Sørensen et al. (1) that reported the efficacy of post-operative clopidogrel treatment in a large patient cohort revascularized with coronary artery bypass graft surgery (CABG) after myocardial infarction. Notwithstanding the criterion of preoperative myocardial infarction, it remains interesting that this result is contrary to the CASCADE (Clopidogrel After Surgery for Coronary Artery DiseasE) trial, where addition of clopidogrel to aspirin revealed no changes on the post-operative outcomes (survival, 1-year intimal hyperplasia) (2). A possible explanation could be the different rates of aspirin and/or clopidogrel resistance between the 2 populations.

Aspirin resistance after cardiac surgery varies between 7% and 54% (depending on the platelet assay) (3). In contrast, clopidogrel response in patients undergoing CABG remains unknown due to the fact that aspirin is the drug of first choice after CABG, and clopidogrel administration (in addition to aspirin) is recommended mainly in patients with acute coronary syndrome (1). However, previous reports indicate that the clopidogrel resistance rate in coronary stent patients varies between 5% and 56% (4). Besides, carriers of defective alleles for CYP2C19 and CYP2C9 and patients undergoing omeprazole and atorvastatin therapy (inhibitors of CYP2C19 and CYP3A4, respectively) are at risk of clopidogrel resistance as well (5).

Certainly, the considerably high prevalence of clopidogrel resistance in noncardiac surgery patients creates the necessity for assessment of clopidogrel nonresponders undergoing CABG. Otherwise, it remains unknown in dual antiplatelet therapies whether the response to clopidogrel covers a possible aspirin resistance or vice versa. Finally, we congratulate the authors for this excellent and well-defined study and for their contribution to the optimization of the clinical outcomes in patients undergoing CABG after myocardial revascularization.