ABSTRACT
WHAT IS KNOWN AND OBJECTIVE: Premature discontinuation of clopidogrel in patients undergoing percutaneous coronary intervention is a significant risk factor for thrombotic adverse outcomes. However, recent studies indicate that even discontinuation of long-term use of clopidogrel may be associated with multiple adverse outcomes, that is, rebound phenomenon whose mechanism is not definitely clear. The aim of the study was to examine the effect of clopidogrel withdrawal in those on combined aspirin and clopidogrel therapy. METHODS: This prospective, multicenter study enrolled 200 patients who underwent coronary stent implantation and were on dual antiplatelet therapy (100 mg aspirin + 75 mg clopidogrel) 1 year after the stent placement. In all patients, we measured the platelet aggregation, by multiplate electrode aggregometry, using two agonists [adenosine diphosphate with PGE1 (ADPHS) and arachidonic acid (ASPI)] two times: on the day of cessation of clopidogrel and 90 days after clopidogrel was stopped. RESULTS AND DISCUSSION: Following clopidogrel discontinuation, we registered an increase in ASPI values (P < 0·001), linear correlation between changes in ASPI and ADPHS values (P = 0·009) and significant difference in the values of ASPI first quartile of ADPHS compared with the other three (P < 0·001, P = 0·016, P < 0·001, I vs. II, I vs. III and I vs. IV quartile of ADPHS, respectively). WHAT IS NEW AND CONCLUSION: Our findings show that cessation of clopidogrel causes loss of antiplatelet synergism with aspirin, leading to a weakening of the response to aspirin, which may be one explanation for the rebound after the clopidogrel cessation.
