Lyme Carditis AV Block Risk Score Calculator

Lyme Carditis AV Block Risk Score: Explanation and Clinical Context The Lyme Carditis Suspicious Index (LCI)—also referred to as the Lyme Carditis AV Block Risk Score—was developed by Besant et al. (Circulation: Arrhythmia and Electrophysiology, 2018) to identify patients with high-grade atrioventricular (AV) block secondary to Lyme carditis. The tool assists clinicians in differentiating reversible Lyme carditis from idiopathic or degenerative causes of conduction disease. The LCI incorporates six clinical features, each contributing to the likelihood of Lyme carditis: male sex (1 point), age <50 years (1 point), outdoor activity or tick exposure (1 point), constitutional symptoms such as fever, malaise, or myalgia (2 points), erythema migrans rash (4 points), and PR interval >300 ms (1 point).

A total score of 0–2 indicates low risk, 3–6 intermediate risk, and 7–12 high risk of Lyme carditis as the cause of AV block. Patients with high scores should receive immediate empiric antibiotic therapy for Lyme disease pending confirmatory testing. The index helps reduce unnecessary permanent pacemaker implantation by distinguishing transient AV block caused by infection.

Clinically, Lyme carditis should be suspected in younger patients, especially men, presenting with high-degree AV block in endemic regions, particularly during tick season. Early identification and antibiotic treatment typically result in full recovery of conduction.