A 30-year-old man presented to the emergency department with palpitations and tachycardia. He had been experiencing sore throat, fevers, and myalgias for the past day. He became alarmed when he awoke from sleep with strong palpitations and a heart rate greater than 200/min documented on his smartwatch. He had similar symptoms 1 year ago and was diagnosed with and treated for supraventricular tachycardia (SVT). A subsequent outpatient echocardiogram revealed a structurally normal heart; results of a follow-up electrocardiogram (ECG) were also normal (Figure 1, top).