A 31-year-old man with no past medical history presented after a pre-syncopal event. He felt increasingly unwell over the four weeks prior to admission with decreased appetite, fatigue, and intermittent night sweats. Several days prior to admission he began experiencing dyspnea on exertion and reduced exercise capacity. Further history elicited that the patient had spent a summer weekend golfing in Massachusetts. He had no history of rash, insect bites, or joint pain. Physical examination, chest X-ray, and laboratory findings were unremarkable aside from a mild leukocytosis with neutrophil predominance. EKG showed Mobitz type I 2nd degree atrioventricular (AV) block with underlying PR interval prolongation. In the ICU, his heart rate dropped to the 30s with periods of Mobitz type II 2nddegree AV block on telemetry. Transthoracic echocardiogram was unremarkable. He was treated with empiric IV ceftriaxone for putative Lyme carditis. Lyme serologies returned positive. AV block and Wenckebach phenomenon gradually resolved and the patient was discharged with a four-week course of PO doxycycline.
AV node dysfunction is typically seen in an older population with structural heart disease. When AV block presents in a young, healthy patient, alternative diagnoses should be considered. Lyme borreliosis is the most common tick-borne infectious disease in North America. Clinical findings include localized and disseminated manifestations: erythema migrans rash, neurologic and cardiac involvement, and arthritis. Lyme carditis occurs in less than 1% of patients and typically affects the conduction system at the AV node, though myocarditis or pericarditis can occur. Serologic testing is generally positive, but if negative with high suspicion for Lyme carditis retesting should occur two to six weeks later. Lyme carditis is usually benign with most patients recovering completely. Though often unresponsive to atropine, with temporary pacing necessary in 30% of patients, permanent heart block and death are rare. Antibiotic treatment has not been shown to prevent Lyme carditis, but is recommended to eradicate disease and prevent late complications.
Lyme carditis is a feared complication of Lyme disease but can be easily treated with antibiotics if properly identified. Given its rarity, it is not often considered as a diagnosis, particularly in non-endemic areas. This example illustrates the importance of recognizing Lyme carditis in cases without classic Lyme symptoms such as rash, fevers, myalgias, or arthragias. Nonspecific symptoms like fatigue, malaise, and syncope in a high-risk patient could represent Lyme disease. Recognition of Lyme carditis is important in areas such as New England, where Lyme disease is particularly common, but the disease can be seen across the United States and should be considered as an etiology for syncope and abnormal heart rhythm, especially in patients with low cardiac risk.
To cite this abstract:Kiss J, Ronan M. Tick…tock? A Rhythm Problem. Abstract published at Hospital Medicine 2015, March 29-April 1, National Harbor, Md. Abstract 569. Journal of Hospital Medicine. 2015; 10 (suppl 2). https://www.shmabstracts.com/abstract/ticktock-a-rhythm-problem/. Accessed January 18, 2020.