Platelet activity before and after coronary artery bypass grafting

The normal response of the platelet can be altered either by increased pro-aggregatory stimuli or by diminished anti-aggregatory substances. Increased platelet activation occurs in the cardiovascular disease states of stable angina pectoris and acute coronary syndromes. Also, cardiac surgery involving cardiopulmonary bypass is associated with extensive contact between blood and synthetic surfaces and leads to a strong activation of platelets. Using light transmission aggregometry method, we tested platelet sensitivity to ADP and spontaneous activity in the platelet-rich plasma of patients before and after coronary artery bypass grafting (CABG). The median values of EC50 for ADP were significantly lower at days 3 and 5 after surgery (0.33 and 0.37 microM, respectively) than before surgery (0.65 microM). The medians percentages of spontaneous platelet aggregation were significantly higher after than before surgery (16 and 15% at days 3 and 5 after surgery, respectively, vs. 5% before surgery). Thus, there is a significant increase of spontaneous platelet aggregation and platelet hyperreactivity to ADP in patients after CABG compared with those before surgery.