A 59-year-old man with a history of hypertension and hyperlipidemia was admitted to the hospital for evaluation of extreme fatigue and recurrent syncope. He had a history of syncope 2.5 years before the current admission and again 7 weeks before. The patient was taking atenolol, atorvastatin, and low-dose aspirin at the time of his symptoms. Diagnostic evaluation before admission included normal physical examination findings: He was afebrile with normal blood pressure and heart rate. The patient underwent echocardiography, which demonstrated mild left ventricular hypertrophy and normal cardiac function (online-only Data Supplement Movie I). He was referred for exercise stress testing but was found to be in atrial fibrillation with a slow ventricular response. He spontaneously converted to normal sinus rhythm with first degree-atrioventricular (AV) heart block (PR interval 0.52 seconds) with periods of second-degree AV heart block (Figure 1A). Given the new heart block, atenolol was stopped and the patient was admitted for cardiac monitoring and further diagnostic evaluation.
Initial physical examination on admission was significant for low-grade fever to 100.9°F, blood pressure 140/80 mm Hg, and heart rate 44 bpm and irregular. Remainder of examination was normal including the cardiac examination. Chest x-ray was normal (Figure 2). Laboratory data revealed normal cardiac enzymes and electrolytes and negative blood cultures. Patient denied recent tick bite or exposure and did not present with a rash, but given fever and new AV heart block, Lyme titers were sent and subsequently came back positive for both IgM and IgG antibodies. The patient was started on intravenous ceftriaxone for presumed clinical diagnosis of Lyme carditis. The patient’s symptoms dramatically improved on treatment with no recurrent fevers. However, he continued to demonstrate episodic high-degree AV block, and further evaluation with cardiac magnetic resonance (CMR) imaging was performed for risk stratification and to assess for alternative causes. CMR demonstrated a single linear focus of late gadolinium enhancement in the midwall region of the basal anteroseptal wall (Figures 3A and 4⇓) with corresponding subtle increased signal on T2-weighted turbo spin echo images (Figure 5) consistent with focal myocarditis likely due to Lyme disease given the clinical history. No wall motion abnormalities were detected and cardiac function was normal (online-only Data Supplement Movie IIA).
The patient was noted to have significantly less AV block over his hospital course and was discharged home with a 4-week course of treatment with ceftriaxone. At 6 week follow-up, the patient’s ECG demonstrated first-degree AV block with PR interval of 0.24 seconds (Figure 1B). Follow-up CMR revealed significantly diminished extent of late gadolinium enhancement in the basal anteroseptal wall and again no wall motion abnormalities (Figure 3B and online-only Data Supplement Movie IIB) consistent with the patient’s clinical course.
Lyme Borelliosis is the most common tick-born infection in the northern hemisphere. It is a multisystemic disease caused by infection of Borrelia burgdorferi. Approximately 10% of patients exhibit cardiac complications, the most frequent manifestation of which is transient atrioventricular nodal block.1 Lyme disease is typically diagnosed clinically on the basis of a history of tick bite, characteristic rash (erythema chronicum migrans), and elevated Lyme titers. However, approximately two thirds of patients affected never remember a tick bite or present with a rash, as in our case. Furthermore, serodiagnostic tests are insensitive during the first several weeks of infection.2
Gadolinium-enhanced CMR has proven useful in the evaluation of myocarditis; however, only a few cases have been reported documenting CMR findings in patients with Lyme carditis.3–5 We report a case of late gadolinium enhancement with corresponding subtle increased signal on T2-weighted turbo spin echo images in the midwall region of the basal anteroseptal wall, a site in close proximity to the presumed location of the AV node in a patient with high-degree AV block and positive Lyme titers. We also found significantly diminished extent of late gadolinium enhancement at 6 weeks follow-up, which correlated with significant improvement of AV block after antibiotic treatment. These findings provide a possible pathophysiological imaging correlate for the cardiac manifestations of Lyme disease and suggest a potential role for CMR in noninvasively following up patients with Lyme disease. Additionally, in patients with AV block without clinical or laboratory evidence of Lyme disease, CMR may aid in suggesting the diagnosis of Lyme carditis. Noninvasive diagnosis and monitoring of Lyme carditis, a potentially reversible cause of AV block, is important because it can help guide appropriate therapy with antibiotics that would thereby avoid permanent pacemakers.
The online-only Data Supplement can be found with this article at http://circ.ahajournals.org/cgi/content/full/118/18/1881/DC1.