Reversible high-grade atrioventricular block with septal myocardial edema in Lyme carditis

A 34-year-old road builder was admitted to the authors' emergency department due to progressive dyspnoea that had been present for 6 days. The patient had a history of excessive smoking (60 cigarettes/day). The medical history was otherwise unremarkable. A transient rash had occurred during work 2 weeks previously. The patient could not remember a bite. The electrocardiogram showed 2:1 atrioventricular (AV) block with narrow QRS complexes. D‑dimer and C‑reactive protein were slightly elevated; all other laboratory findings were within normal range. Echocardiography revealed normal findings. ELISA and western blot analysis confirmed acute Lyme disease. Cardiac magnetic resonance imaging (MRI) disclosed myocardial edema in the interventricular septum. Antibiotic treatment with ceftriaxone was initiated for 2 weeks. The heart block improved to a first degree AV block (PR interval 274 ms) at day 5 of treatment. At discharge, the patient had a normal PR interval of 190 ms. Follow-up cardiac MRI revealed almost complete regression of the cardiac septal edema.