A 53-yr-old woman comes to the office because of palpitations. She is a current patient there and has a history of well-controlled hypertension, type 2 diabetes, and tension headaches. She states that she has noticed intermittent palpitations over the past 2 mo. She describes the episodes as a sensation of irregular and racing heartbeats that are accompanied by fatigue. She denies any chest pain, shortness of breath, light-headedness, or syncope. The episodes last from 10 min to several hours, occur once or twice/wk, and resolve on their own. The last episode was 3 days ago. She cannot identify any particular triggers. She is generally active and walks 3 miles several days/wk without any exertional symptoms including chest pain and dyspnea. She has no family history of early cardiac disease or sudden death. She denies any recent fever or infectious symptoms.