A man in his 80s with recurrent syncope was admitted to the emergency department. The patient previously underwent an electrophysiological study (the exact procedure was unknown) in another hospital because of syncope, and the result did not suggest the need for pacemaker implantation. He denied a recent medical history of chest pain or dyspnea on exertion. On examination, his oxygen saturation while breathing room air was 98%, and his blood pressure was 120/76 mm Hg. The result of cardiopulmonary examination was unremarkable. Echocardiogram findings revealed a left ventricular ejection fraction of 54% with normal ventricular wall motion. Blood laboratory data, including serial high-sensitivity troponin, D-dimer, renal function, electrolytes, and blood glucose, were unremarkable. The results of the electrocardiogram (ECG) that was performed at admission was recorded (Figure, A).