A 24-year-old woman presents to the emergency department reporting an abrupt onset of rapid, regular heart palpitations that began about an hour ago. She feels anxious and lightheaded. She denies any chest pain, shortness of breath, or syncope. She has experienced several similar episodes in the past, but they were brief and resolved spontaneously. Her past medical history is unremarkable, and she takes no regular medications. There is no family history of arrhythmias or sudden cardiac death.