A patient in their 70s presented to the emergency department with acute onset waxing and waning chest pressure that lasted several hours and radiated to both arms. The pressure was accompanied by shortness of breath. The patient’s risk factors for cardiac disease included age, hypertension, active smoking, and peripheral vascular disease. The patient had no known prior cardiac disease. The patient was afebrile with a heart rate of 118 beats/min and blood pressure of 159/98 mm Hg. The patient’s oxygen level was saturating 96% on room air. The results of relevant cardiopulmonary examination were unremarkable. The initial electrocardiogram (ECG) obtained in the emergency department showed sinus rhythm with ST-segment elevations in leads I and aVL, as well as reciprocal depressions in leads II, III, and aVF (Figure, A). A diagnosis of lateral ST-segment–elevation myocardial infarction (STEMI) was made. Laboratory evaluation revealed an initial high-sensitivity troponin T level of 9.685 ng/mL (normal range, <0.048 ng/mL; to convert to μg/L, multiply by 1). The patient was treated with aspirin, ticagrelor, and heparin. They were taken for an emergency coronary angiography and possible percutaneous coronary intervention.