Background It is not reasonable to administrate the same dosage of antiplatelet medicine to all patients with ACS regardless of patients’ height, weight, metabolism and effectiveness of those medicines. And thromboelastography (TEG) has provided a relatively stable, convenient, duplicable method for testing activity of platelet in recent years.

Objective To investigate the inhibition levels and characteristics of frequency distributions of platelet aggregation after antiplatelet therapy with aspirin and clopidogrel in Chinese patients with ACS undergoing PCI.

Methods High risk Patients with ACS received PCI after administration of loading dosage of clopidogrel (600 mg) and aspirin (300 mg) subsequence with maintenance dose of clopidogrel (75 mg per day) and aspirin (100 mg per day) for one year. Blood sample was gotten 24–48 h after PCI for the test of TEG-mapping in order to detect the residual activities of platelet induced by thrombin AA or ADP. And then the inhibition ratios of platelet after therapy were calculated and the characteristics of their distribution were analysed.

Results 1) The maximal potential activities of platelet are not homogeneous. Among the patients enrolled in this study, 7.1% is in very low activity while 14.3% is in very high. 2) The inhibition on aggregation of platelet also differs in ADP pathway and AA pathway. The frequency fractional of aspirin is more lower when the inhibition rate is under 30% and more higher when it is between 70%–79.9% (p<0.05). 3) The actual frequency fractional variation of each intensity of inhibition also differs significantly (p=0.0026). 4) Even in the same patient the inhibition of platelet aggregation of the two pathways, AA and ADP, is not synchronous. 5) Only 1.6% of the patients experienced resistance in both aspirin and clopidogrel pathway, and 3.8% of them are over-sensitive in both.

Conclusion We should assess basic activity of platelet and the reacts to remedies on every patient individually because they differ significantly in each case. Even in same patient, the change of inhibition on aggregation of platelet by aspirin or clopidogrel is not synchronous. So, we should assess the effects of aspirin and clopidogrel respectively in each patient. In Chinese patients with ACS, the inhibition intensity of platelet by aspirin with regular dosage is higher than that of clopidogrel. Only 1.6% patients with both aspirin and clopidogrel resistance, who are at high risk of thrombosis, while 3.8% patients over-sensitive to both aspirin and clopidogrel, who are at high risk of haemorrhage. All of these mean that the individual assessment on activity of platelet and reaction of antiplatelet therapy should been done in order to adjust medicine and dosages.