A patient in their 40s with a history of hypertension and smoking presented to the emergency department with sudden-onset palpitations and chest tightness after an argument. The symptoms relieved spontaneously after 50 minutes. The patient was asymptomatic on arrival, and all vital signs were within normal limits except for an elevated blood pressure of 160/92 mm Hg. The patient’s hemogram; levels of serum electrolytes; renal, hepatic, and thyroid function; and levels of troponin I, B-type natriuretic peptide, and D-dimer were within normal limits. A 12-lead electrocardiogram (ECG) was obtained (Figure, A).