Full Length ArticlePlatelet function one and three months after coronary bypass surgery in relation to once or twice daily dosing of acetylsalicylic acid

•Platelet activation was enhanced one and three months after CABG.•ASA 160 mg OD and 75 mg BID most effectively suppressed thromboxane production.•Platelet aggregation was least effectively inhibited by ASA 75 mg OD.•ASA higher than 75 mg OD should be considered the first 3 months after CABG.•Twice daily dosing of ASA is of interest for further evaluation.

IntroductionCurrent guidelines recommend acetylsalicylic acid (ASA) treatment after coronary artery bypass grafting (CABG) to reduce thrombotic vein graft occlusion. The optimal dosage of ASA is not known.Materials and methodsForty-two patients undergoing elective CABG were randomized to receive either ASA 75 mg or 160 mg once daily (OD) or 75 mg twice daily (BID) after the operation. Platelet function testing was performed before, and one and three months after the operation.ResultsWhite blood cell counts increased during the initial postoperative days whereas platelet counts were initially slightly reduced after the operation but increased after one month without any major changes of mean platelet volumes. Serum thromboxane B2 was more effectively suppressed at one and three months after the operation with ASA 75 mg BID or 160 mg OD than with 75 mg OD (p < 0.001). ASA 75 mg BID and 160 mg OD were equally effective. Adenosine diphosphate stimulated platelet aggregation in whole blood (Multiplate®) was increased one and three months after the operation, and this was counteracted by ASA 75 mg BID but not by 75 or 160 mg OD. Arachidonic acid-induced aggregation was more effectively inhibited by 75 mg BID or 160 mg OD compared to 75 mg OD at three months.ConclusionsLess effective inhibition of platelet activation was obtained with ASA 75 mg OD than with ASA 160 mg OD or 75 mg BID up to three months after CABG. Especially the latter dose is of interest for further studies of efficacy and clinical outcomes after CABG.