Lyme Carditis With Complete Heart Block.

Lyme disease, the most common tick-borne infection in North America, can lead to multi-organ involvement, including Lyme carditis. This report describes the case of a 42-year-old male who presented with a third-degree atrioventricular (AV) block due to Lyme carditis. The patient reported a history of a recent tick bite and erythema migrans rash, followed by progressive fatigue, palpitations, and dyspnea. Initial electrocardiogram (EKG) revealed third-degree AV block with ventricular escape rhythm, necessitating temporary transvenous pacing and intravenous ceftriaxone therapy. Within 48 hours, the patient significantly improved, transitioning to first-degree AV block with a decreasing PR interval. After clinical stabilization, intravenous ceftriaxone was switched to oral doxycycline, and the patient was discharged with outpatient follow-up. This case emphasizes the significance of early recognition and treatment of Lyme carditis to prevent life-threatening complications and avoid unnecessary permanent pacemaker implantation.