A Curious Presentation of Chronic Chest Pain

A 68-year-old male patient presented to the hospital with a complaint of chest pain that started 2 to 3 months ago.He described the pain as intermittent and located substernally, with radiation to his neck and left arm.The patient had a dual-chamber pacemaker implanted 7 months previously for complete heart block.No abnormalities were detected on physical examina-tion.An echocardiogram performed on the same day indicated normal cardiac function, and a subsequent coronary angiography revealed no significant coronary artery disease.The patient's admission ECG is shown in Figure 1.No prior ECGs were available for review.How should we interpret the ECG?What is the most likely diagnosis?How should we manage this patient?Please turn the page to read the diagnosis.