Lyme Carditis: A Reversible Cause of Acquired Third-Degree AV Block

BACKGROUND Lyme borreliosis, caused by spirochetes of the Borrelia burgdorferi genospecies complex, is the most commonly reported tickborne infection in North America and those infected may present with cutaneous, cardiac, articular, and neuropsychiatric abnormalities. The protean nature of many of its clinical manifestations presents a diagnostic conundrum. Lyme disease can affect the heart, albeit rarely, with cardiac abnormalities usually manifesting as varying degrees of heart block or arrhythmias. CASE REPORT We present a case of complete heart block in a young man who participated in outdoor activities in a Lyme-endemic area and developed fatigue and palpitations weeks after a flu-like illness. He noticed that his heart rate was low; he had an intermediate suspicious index in Lyme carditis (SILC) score with positive Lyme serologies. His initial electrocardiogram when he presented to the emergency department showed a complete heart block. In this case, he was successfully managed with intravenous ceftriaxone, amoxicillin, and a transcutaneous pacemaker, obviating the need for a permanent pacemaker. CONCLUSIONS Electrocardiographic changes such as heart block and arrhythmias with or without symptoms may be the initial manifestation of Lyme carditis in a patient who may or may not remember a tick bite or have a typical skin rash. The SILC score may assist in recognizing these cases and prompt initiation of antibiotics usually leads to the resolution of these electrocardiographic abnormalities and symptoms that may be present.