Abstract
Purpose: A case report of a patient who presented with an acute onset, fluctuating atrioventricular (AV) block and was diagnosed with Lyme carditis is presented. Summary: A 55-year-old man with progressively worsening generalized malaise, flu-like symptoms, dyspnea on exertion, and near syncope was admitted with bradycardia (heart rate was between 20 and 30 beats per minute upon admission). He endorsed having several tick bites after which he developed erythema migrans on his arm and abdomen. An electrocardiogram (ECG) revealed a second-degree AV block, fluctuating between Mobitz type I and Mobitz type II heart block, with a P-R interval of 300 ms. A presumptive diagnosis of Lyme carditis was made based on a confirmed history of tick exposure, presence of erythema migrans, and AV block. The patient was started on ceftriaxone. On day 3 of hospitalization, patient's heart rate was between 50 and 60 beats per minute. A diagnosis of Lyme disease was confirmed based on serologic testing. A repeat ECG revealed a first-degree AV block with a P-R interval of 300 ms. On day 5 of hospitalization, a peripherally inserted central catheter line was placed and the patient was discharged to his home on a 28-day course of ceftriaxone. Patient's heart rate was 65 beats per minute on discharge day. Conclusion: Considering Lyme carditis as a differential diagnosis in patients with an AV block of an unknown etiology can result in a timely diagnosis and treatment of Lyme carditis.