text: Subjects with acute coronary syndromes scheduled for cardiac catheterization will be enrolled in this study. Subjects that are to be treated clinically with coronary artery stenting will be randomized to receive a loading dose of clopidogrel versus ticagrelor after diagnostic angiography but prior to stenting. Optical coherence tomography (OCT) will be performed after stenting and the presence of blood clots inside the new stent will be measured and compared between the groups.
  
  Total thrombus burden as measured by the volume of in-stent thrombus quantified by planimetry. [ Time Frame: Thrombus burden will be measured at the end of the coronary artery stenting procedure. ] [ Designated as safety issue: No ]
  
  The total thrombus burden measured on OCT images will be assessed. The volume of in-stent thrombus will be quantified by planimetry.
  
  Secondary Outcome Measures:
  
  PRI (platelet reactivity index) as measured by the PLT-VASP assay. [ Time Frame: PRI will be measured at the time of OCT image acquistion (which will occur at the end of the coronary artery stenting procedure). ] [ Designated as safety issue: No ]
  
  The extent of platelet inhibition will be measured by PLT-VASP and VerifyNow P2Y12 assays.
  
  P2Y12 Reaction Units as measured by the VerifyNow P2Y12 assay. [ Time Frame: P2Y12 will be measured at the time of OCT image acquistion (which will occur at the end of the coronary artery stenting procedure). ] [ Designated as safety issue: No ]
  
  The extent of platelet inhibition will be measured by PLT-VASP and VerifyNow P2Y12 assays.
  
  Other Outcome Measures:
  
  PCI- related myocardial infarction (MI) [ Time Frame: PCI-related MI will be assessed within 24 hours after the end of the coronary artery stenting procedure. ] [ Designated as safety issue: No ]
  
  PCI related myocardial infarction is defined by the third Universal defintion of myocardial infarction.
  
  Hepatic insufficiency defined as liver cirrhosis, AST/ALT/Alkaline Phosphatase greater than 3 times the upper limit of normal or hyperbilirubinemia.
  
  Lesion Specific Exclusion Criteria These exclusion criteria apply to the target lesion to be imaged by OCT.
  
  Lesion located in the left main coronary artery
  
  Lesions that are heavily calcified
  
  Lesions where OCT cannot be performed due to technical difficulties
  
  Other lesions that the investigator deems inappropriate for the procedure such as sites with excessive tortuosity or low flow by TIMI grade.
  
  Lesion in saphenous vein or arterial conduit
  
  Contacts and Locations
  
  Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study.
  To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below.
  For general information, see Learn About Clinical Studies.
  
  Please refer to this study by its ClinicalTrials.gov identifier: NCT01826175