A Pilot Randomized Controlled Trial of Intravenous N-acetyl Cysteine in STEMI

Inclusion Criteria: Patients presenting with STEMI within 3 hours of symptom onset and satisfying all of the following criteria: 1. Patient age ≥ 18 years 2. Have received thrombolysis, with intend to pursue a pharmaco-invasive reperfusion strategy. Onset of chest pain to reperfusion time of \< 3hrs. 3. STEMI involving anterior and/or inferior wall 4. An absence of baseline Q-waves on the initial ECG: The presence of Q waves defined at baseline using the Selvester QRS screening criteria 5. Have a high-risk STEMI ECG defined as: * ≥2mm ST-segment elevation in 2 anterior or lateral leads; or * ≥2 mm ST-segment elevation in 2 inferior leads coupled with ST-segment depression in 2 contiguous anterior leads for a total ST-segment deviation of ≥4 mm Exclusion Criteria: 1. Previous myocardial infarction 2. Known to have moderate to severe LV systolic dysfunction (LV EF\< 45%) 3. Known allergy to thrombolytic therapy or NAC 4. Presence of left bundle branch block 5. Cardiogenic shock (defined as systolic blood pressure of \< 90mm Hg, for at least 30 minutes, not responsive to fluid resuscitation) 6. Permanent pacemaker or cardioverter defibrillator implanted previously 7. Patients with contra-indications to thrombolytic therapy 8. Patients with loss of consciousness or confusion 9. Patients with known chronic kidney disease (GFR \< 30ml/min/m2) or on dialysis 10. Current pregnancy 11. Planned therapy with primary PCI