0321: In the aera of new P2Y12 inihibitors, high platelet reactivity on aspirin in patients with ST elevation myocardial infarction remains a predictor of ischemic events

Background Despite dual antiplatelet treatment with the new P2Y12 platelet receptor antagonists (P2Y12i), major ischemic events are common following ST elevation myocardial infarction (STEMI). Objectives To assess separately resistance to aspirin (HPR-aspirin), resistance to P2Y12i (HPR-P2Y12i) and their association during the acute phase of STEMI in relation to the occurrence of ischemic events. Methods We included all consecutive patients admitted for STEMI in our center between January 2013 and December 2013. All patients received a loading dose followed by a maintenance dose of aspirin (75mg/day) and either clopidogrel, prasugrel or ticagrelor. Platelet reactivity was assessed 4±1 days and 75±15 days after admission using light transmission aggregometry (LTA) with arachidonic acid (AA) and serum Thromboxane-B2 concentration to assess HPR-aspirin and LTA-ADP and VASP index to assess HPR-P2Y12i. Major cardiac and cerebrovascular events (MACCE) were recorded during one year. Results 106 patients (61years old, 76% male, 20% with diabetes) were included. STEMI was anterior in 52% and LV ejection fraction at discharge was 51±9%. At day 4 after STEMI, HPR-aspirin measured by LTA-AA alone was found in 23% patients and was correlated with serum thromboxane inhibition, HPR-P2Y12i (VASP≥50% and LTA-ADP≥65%) was observed only in 7% and combined resistance was present in 4% of the patients. Diabetes and age were predictors of HPR-aspirin. The large use of ticagrelor (34%) and prasugrel (50%) explained the low rate of P2Y12i resistance. HPR-aspirin was persistent 75 days later in 36% patients who were resistance at day 4. At 1 year, 7.9% patients had experienced MACCE. HPR-aspirin alone and HPR for both aspirin and P2Y12i were significantly associated with MACCE. Conclusion Aspirin resistance is frequent just after STEMI and is associated with MACCE especially when associated with P2Y12i resistance.