Background: Lyme disease is the most common tick-borne illness in the United States, with a prevalence of approximately 500,000 cases annually. Myocarditis is a rare Lyme complications recent data demonstrated prevalence of Lyme myocarditis to be 1% and usually appears 1-2 months after initial infection. We hereby present a rare case of early-onset Lyme Myocarditis.

Case Presentation: A 35-year-old male with no significant past medical history presented to the hospital with four days of fever, myalgia, and headache. The day prior to admission, he found a tick at his home and developed a circular rash. He denies chest pain, SOB, palpitations, dizziness. He had no prior medical or family history of cardiac disease and denied tobacco, alcohol, and illicit drug use. He lives with his wife and owns a dog. On physical examination, T 102.6F, HR 103, BP 109/68, RR 19, SpO2 96% on room air. A target lesion was noted on his right thigh; rest of the physical examination was benign. His labs revealed positive serology for B. Burgdorferi IgM antibody, positive western blot, high sensitivity troponin 240; EKG was normal sinus rhythm with no ST or T wave changes. The patient was diagnosed with early localized Lyme disease and discharged home on doxycycline; the troponin elevation was attributed to the fever. He returned to the hospital the next day with chest pain and palpitations; exam was normal, high sensitivity troponin was 267 and ECG was unchanged. Echocardiogram demonstrated EF of 60% without any valvular abnormalities or effusions. He declined cardiac catheterization; a pharmacological nuclear stress test did not show perfusion defects. He was diagnosed with Lyme myocarditis and treated with two-weeks course of ceftriaxone with clinical improvement.

Discussion: Myocardial involvement in Lyme disease results from spirochete colonization in cardiac tissue and subsequent exaggerated immune response, most commonly leading to myocarditis and subsequent heart block; which occurs 1-2 months after Borrelia infection. Typical clinical manifestations of Lyme myocarditis include palpitations, chest pain, conduction abnormalities, pericarditis and heart failure. The diagnosis is clinical and made by, positive Lyme serology accompanied by EKG changes and symptoms. other tests that can point to cardiac involvement include troponins, positive echocardiogram, and negative CAD testing. Treatment depends on clinical status; asymptomatic patients with 1° AV block can be treated with oral antibiotics, whereas symptomatic patients will require IV antibiotics, and patients with 3° heart block may require temporary pacemakers.