A 24-year-old woman without known medical history presents to the emergency department (ED) with anxiety and palpitations for the past hour. She describes several years of similar symptoms that have been in the past dismissed as panic attacks. She is otherwise asymptomatic. Her vital signs are normal except for a pulse of 160 beats/min. Her 12-lead ECG is displayed in Figure 1:
She converts to sinus rhythm spontaneously and the ED sends her home on verapamil ER 120 mg daily. She presents to her primary care physician 2 weeks later feeling well without recurrent palpitations. Her ECG on verapamil is displayed in Figure 2. She asks her physician if she will need to take the medication for the rest of her life.
Question 1: What is the differential diagnosis of the patient’s arrhythmia?
Question 2: What is the most likely diagnosis of the patient’s arrhythmia based on a comparison between the two presented ECGs?
Question 3: What is the best next step in treating this patient?