TIMES: Ticagrelor vs. Placebo/ Clopidogrel With Aspirin in Anterior STEMI Patients Treated With Primary PCI

Inclusion Criteria: 1. Provision of informed verbal consent prior to any study specific procedures taking place with written consent confirmed prior to in-patient cardiac MRI. 2. Male or female adult patient aged 18 - 90 years old 3. Anterior STEMI (ST elevation ≥ 2mmHg in contiguous chest leads) with chest pain symptom onset \< 12 hours Exclusion Criteria: 1. Cardiogenic shock\* 2. Previous anterior myocardial infarction 3. Unfavourable coronary anatomy for PCI: left main / surgical or distal coronary disease 4. Already prescribed Ticagrelor at the time of admission 5. Factors affecting study drug administration/ absorption: vomiting or allergy 6. Concomitant use of potent CYP3A4 inhibitors/ inducers (e.g ketoconazole and rifampicin) or CYP3A4 substrates with a narrow therapeutic window (e.g. cisapride and ergot alkaloids) or simvastatin / lovostatin \>40mg oral dose. 7. Severe bleeding diathesis or current active bleeding\* 8. History of intracranial haemorrhage 9. Moderate or Severe hepatic impairment 10. Severe asthma or bradycardia/ complete heart block (contraindications to adenosine)\* 11. Severe co-morbidity with a life expectancy \< 3 months. 12. Women of child bearing potential (as determined by direct questioning of the patient to confirm and this will be documented in the medical notes). * Patients that are found to have any excluding factor (e.g., unfavourable coronary anatomy for PCI) or develop any excluding factor (e.g., vomiting or cardiogenic shock) before the point of final IMR assessment will be discontinued from the study and followed up at discharge and by telephone at 3 and 12 months for adverse event monitoring purposes only.