Heart Attack Research Program: Platelet Sub-Study (HARP)

Inclusion Criteria:

* Acute ischemic symptoms compatible with diagnosis of MI, such as chest pain or anginal equivalent symptoms at rest or new onset exertional anginal equivalent symptoms
* Objective evidence of MI (either or both of the following):

  * Elevation of troponin to above the laboratory upper limit of normal (ULN)
  * ST segment elevation of ≥1mm on 2 contiguous ECG leads
* Willing to provide informed consent and comply with all aspects of the protocol
* Administration of aspirin at least 1 hour before cardiac catheterization
* Administration of thienopyridine (e.g., clopidogrel, ticagrelor) at least 1 hour before cardiac catheterization
* Women and men with ≥50% of any major epicardial vessel on invasive angiography may participate

Exclusion Criteria:

* Recent use of vasospastic agents, such as cocaine, triptans, or ergot alkaloids (≤1 month)
* Alternate explanation for troponin elevation, such as hypertensive urgency, acute exacerbation of heart failure, chronic elevation due to kidney disease, pulmonary embolism, cardiac trauma
* Pregnancy
* Thrombolytic therapy for STEMI (qualifying event)
* Use of any of the following medications:
* Platelet antagonists (except aspirin and thienopyridines) within 7 days
* NSAIDs (e.g., ibuprofen, naproxen) within 3 days.
* Thrombocytopenia (platelet count \<100,000)
* Thrombocytosis (platelet count \>500,000)
* Anemia (hemoglobin \<9 mg/dl)
* Hemorrhagic diathesis