Impact of clopidogrel in coronary artery bypass grafting

The recent article by Carrel et al. [1] entitled ‘Impact of clopidogrel in coronary artery bypass grafting’ highlights an emerging problem faced by surgeons operating on patients continued on clopidogrel until surgery. The results of this prospective observational study suggest that clopidogrel therapy within three days of cardiac surgery increases post-operative blood loss and the need for blood products. We wish to congratulate the authors on a very interesting paper; however, we feel that certain issues must be addressed before we are able to give credence to their conclusions. Given that this is an observational study, it would be reasonable to assume that the clopidogrel group is not homogenous, with patients having had clopidogrel stopped anywhere between 0–72h prior to surgery. What percentage had it stopped 1–3 days prior to surgery. For the no clopidogrel group, what was the median time at which clopidogrel was stopped prior to surgery? Was the mean time in the no clopidogrel group less than seven days? Clopidogrel irreversibly inhibits platelet aggregation and hence its effect is present for the life of the platelet (7–10 days) [2]. Taking this into account, it is essential that the authors demonstrate a difference in platelet function between the two groups before conclusions are drawn. Also, the authors failed to mention how many patients in the clopidogrel compared to the no clopidogrel groups were on combined aspirin and clopidogrel therapy. Secondly, although aprotinin is widely used to reduce post-operative blood loss, the issue of graft patency has not been fully addressed. Hence we feel that administering aprotinin to patients who are not at an increased risk of bleeding is not justified in view of concerns about its effect on reducing graft patency [3]. Do the authors routinely use aprotinin on patients who are not at an increased risk of post-operative blood loss? In addition, because this study was not randomized, perhaps, practice was divided amongst the unit with regard to stopping clopidogrel prior to surgery and hence what is presented is in fact a comparision between the practices of two groups of surgeons within a surgical unit; one group that routinely stops clopidogrel at least 3 days prior to surgery and the other group that continues clopidogrel until surgery. This would invariably enter bias with regards to different surgical techniques and details to achieving haemostasis. The important issue of clopidogrel and post-operative blood loss needs to be addressed by a well-designed prospective randomised controlled trial.