An older adult with a history of hypertension and diabetes presented to the emergency department with paroxysmal chest pain. The chest pain had occurred 6 times during the day and was relieved by sublingual nitroglycerin. On arrival, the patient’s blood pressure and pulse rate were 160/86 mmHg and 45 beats per minute (bpm), respectively. Results of a hemogram, serum electrolyte, kidney, liver, troponin I, B-type natriuretic peptide, and D-dimer tests were all within normal limits. The chest pain resolved before the initial electrocardiogram (ECG) was performed (Figure, A). The diagnosis was unstable angina, and loading doses of aspirin, ticagrelor, and atorvastatin were prescribed. On the second day of hospitalization, the chest pain recurred. A repeat ECG was performed at the onset of chest pain (Figure, B).