RESUMO
BACKGROUND Lyme disease is a tick-borne illness caused by bacteria of the Borrelia genus, endemic to the northeastern region of the United States. It typically presents with fevers, myalgias, and erythema migrans, but it can result in disseminated symptoms if left untreated. Lyme carditis is a rare, but potentially fatal complication of Lyme disease, occurring in up to 4-10% of untreated cases. Typically, it presents with atrioventricular conduction abnormalities, which resolve with intravenous antibiotics and temporary pacing if indicated. Diverse cardiac pathology, however, has been associated with Lyme carditis, which may be underrecognized in practice. CASE REPORT A 34-year-old woman with no significant medical history presented with fatigue, dizziness, and shortness of breath, 2 weeks after camping in Rhode Island. Her presenting electrocardiogram demonstrated third-degree heart block. She was noted to have targetoid rashes on her left shoulder and breast on physical examination. On laboratory work-up, she was found to have positive Lyme total antibody enzyme immunoassay and positive Lyme western immunoblot. The findings were diagnostic for Lyme carditis. The patient's cardiac rhythm subsequently converted to slow atrial flutter with variable ventricular response unresponsive to antibiotic therapy. Given evidence suggesting that atrioventricular conduction was preserved, synchronized electrical cardioversion was pursued and was ultimately successful in rhythm conversion to normal sinus rhythm. CONCLUSIONS Although Lyme carditis is rare, this diagnosis should be of high clinical consideration in presentations of cardiac conduction abnormalities with acute onset and without other obvious cause, particularly in Lyme-endemic regions such as the northeastern United States.