Background Acute complete occlusion of a coronary artery results in progressive ischemia, moving from the endocardium to the epicardium (ie, wavefront). Dependent on time to reperfusion and collateral flow, myocardial infarction (MI) will manifest, with transmural MI portending poor prognosis. Late gadolinium enhancement cardiac magnetic resonance imaging can detect MI with high diagnostic accuracy. Primary percutaneous coronary intervention is the preferred reperfusion strategy in patients with ST‐segment–elevation MI with 121 minutes demonstrated increased infarct size, transmurality index, and transmurality grade (all P121 minutes causes a high grade of transmural necrosis. In this pure ST‐segment–elevation MI population, time to reperfusion to salvage myocardium was less than suggested by current guidelines.