A 47-year-old woman with ...

A 47-year-old woman with a history of tobacco use and ulcerative colitis presents with intermittent palpitations. Over the past 6 months, she experiences a sensation of her heart "flip-flopping" every 2–4 days, lasting around 5 minutes. She denies any precipitating factors, lightheadedness, or chest pain during these episodes. Her physical exam is unremarkable, and a resting ECG shows sinus rhythm without abnormalities. In addition to checking serum electrolytes.