The patient presents with an acute inferior ST-elevation myocardial infarction (STEMI), evidenced by ST elevation in leads II, III, and aVF. The most urgent management is to administer aspirin 300 mg, which inhibits platelet aggregation, reducing clot propagation. Immediate primary percutaneous coronary intervention (PCI) is the preferred reperfusion therapy to restore coronary blood flow and limit myocardial damage. Early PCI significantly improves survival and reduces complications compared to fibrinolysis or medical therapy alone. Other interventions like beta-blockers or morphine are adjuncts but not the priority. Time to reperfusion is critical in reducing infarct size.

Reference: Braunwald's Heart Disease, Douglas L. Mann et al., 12th Edition.