Lyme Carditis Beyond Atrioventricular Block: Cardiac Arrest and Transient Atrial Fibrillation With Preserved Atrioventricular Conduction.

Lyme disease may involve the heart during early dissemination and most commonly produces atrioventricular (AV) conduction abnormalities. PR interval prolongation, therefore, frequently guides clinical suspicion and management. We describe a previously healthy man who presented with seizure-like activity, aborted cardiac arrest, transient atrial fibrillation, and cardiac magnetic resonance findings consistent with acute myocarditis, although AV conduction remained normal. Serologic testing subsequently confirmed Lyme carditis. The patient recovered completely with oral doxycycline. This case illustrates that electrical instability may occur despite preserved PR intervals and reinforces the need for suspicion in patients with compatible systemic features.