A 74-year-old man presents to the emergency department after several hours of intermittent lightheadedness and fatigue. He denies chest pain or syncope. His medical history includes hypertension and hyperlipidemia. He takes lisinopril and atorvastatin. Vital signs are stable, and physical examination is otherwise unremarkable.

The ECG obtained in the ED is shown below.

[[sd_correct]] B. Sinus rhythm with second-degree AV block (type-1).  [[/sd_correct]]

  [[sd_short]] [[/sd_short]]

  [[sd_long]] check video below for detailed explanation [[/sd_long]]

  [[sd_lumi]]https://app.lumi.education/api/v1/run/F2Boa1/embed[[/sd_lumi]]