The 'no-reflow' phenomenon after a percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction (STEMI) is a strong predictor of both short- and long-term mortality. Faster antiplatelet activity and increased levels of adenosine provide a theoretical basis for ticagrelor to effectively prevent no-reflow after PCI. We planned to evaluate the effects of ticagrelor on myocardial no-reflow after PCI for STEMI.

Investigators enrolled 240 patients with STEMI who were admitted to the Chinese PLA General Hospital between September 2013 and March 2015. STEMI was defined as typical chest pain lasting N30 min within the previous 12 h, a clear ST-segment elevation of N0.1 mV in ≥2 contiguous electrocardiographic leads, and elevated blood levels of troponin T. We screen high-risk patients through no-reflow risk prediction model， patients were scheduled to undergo diagnostic cardiac angiography or percutaneous coronary interventions. We randomly assigned eligible patients in a 1:1 ratio to receive either ticagrelor 180 mg or clopidogrel 600 mg 30 min before PCI.

The primary efficacy variable was the prevalence of no-reflow assessed immediately post procedure. Secondary efficacy variables were troponin T (TnT), high sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6), superoxide dismutase (SOD), malondialdehyde (MDA), endothelin-1 (ET-1), and nitric oxide (NO) level

Inclusion Criteria:

• patients with STEMI who were admitted to the Chinese PLA General Hospital

Exclusion Criteria:

• 1.unconscious at presentation; 2.had cardiogenic shock, 3.hypoglycemia, 4.diabetic ketoacidosis; 5.had a history of myocardial infarction, stent thrombosis, or renal insufficiency; 6.had previously undergone coronary artery bypass surgery.