Lyme carditis presenting as atrial fibrillation in a healthy young male.

We present a case of a 23-year-old man coming with palpitations, found to be in atrial fibrillation (AF). He was initially managed with metoprolol for rate-controlled therapy-reverted to normal sinus rhythm and discharged home. He returned a few days later-this time in varying degrees of atrioventricular block including transient complete heart block. He was empirically started on intravenous ceftriaxone for suspected Lyme carditis, which subsequently led to the resolution of high-degree heart block. Lyme immunoglobulin G (IgG) and IgM returned positive. Follow-up ECG after the course of antibiotic exhibited normal sinus rhythm. AF is a rare presentation of Lyme disease but still exists. It should be considered in terms of appropriate treatment, especially in Lyme-endemic areas. © BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.