Lyme Carditis

Description of Clinical Presentation: A 35-year-old male, without significant past medical history, consulted a health care center with fatigue, chest discomfort, dizziness and presyncope in the last two weeks. He was referred to the emergency department because ECG demonstrated sinus brady-cardia with AV heart block Mobitz Type II. High-sensitivity troponin series (7-7-7 ng/L), as well as C-reactive protein, (11 mg/L); erythrocyte sedimentation rate, (9 mm/hour) were all normal. During hospitalization the patient presented asystole requiring CPR and intravenous isuprenalin treatment. Since the patient was a pacemaker candidate, additional investigations were ordered.





Diagnostic Techniques and Their Most Important Findings: Echocardiography showed a normal sized left ventricle with normal global and regional systolic function, EF 62 %, GLS – 17%.

Cardiac MRI revealed increased signal on STIR (edema-) -sequence at the basal inferoseptal segment in 4ch- and short-axis views. T 1 and T 2 were increased, 1100 ms and 75 ms respectively, and extracellular volume (EVC) was 35 %. Late Gadolinium Enhancement (LGE) showed a small area of increased enhancement of non-ischemic origin in corresponding areas. The left ventricle was of normal size having normal global and regional systolic function, EF 69%, strain -22 %.

Borrelia IgG was elevated 449AU/mL (ref. 10-14.9 AU/mL).

The patient was treated with ceftriaxone and doxycycline and the AV-block resolved. Implantation of a permanent pacemaker was not indicated. At 4-week follow-up ECG was normalized and during 2-year additional follow up, no cardiac events were documented.

Learning Points from this Case: Lyme carditis (LC) is an uncommon complication of Lyme disease and is estimated to occur in 0,5 % to 10 % in all cases in Europe and North America (1). Lyme disease results from an infection by the spirochete Borrelia burgdorferi following a bite of the infected Ixodes tick (2). Lyme disease affects multiple organ systems such as the skin, the heart and the neurological- and musculoskeletal systems. It is mostly seen in countries with a temperate climate. It is the most prevalent vector-borne disease in North America and Europe (3) and it is increasing in both areas (4, 5).

It is a clinical challenge to diagnose LC since it has a variation of non-specific, easily overlooked symptoms, and often the patient is not aware of a tick bite. Early treatment is crucial as LC can resolve without complications if treated with antibiotics, and if not treated it can be fatal to the patient.

Cardiac MRI is crucial in diagnosing LC due to its ability to visualize tissue edema. Parametric mapping techniques such as T1, T2 mapping and extracellular volume measurements enable quantification. Furthermore, cardiac MRI allows for detection of necrosis/scarring through LGE, where it also enables characterization of LGE´s intramural pattern and distribution, and is capable of prognostication through ventricular dysfunction. However, to determine the etiology of imaging findings complementing methods such as PCR/serology is needed.

A well-defined area with high signal was revealed at the basal inferoseptal segment of the left ventricle with STIR (edema-) sequence.
Corresponding area with Late Gadolinium Enhancement showed only discrete enhancement of non-ischemic character.
Schematic drawing of the conduction system of the heart on the STIR (edema-) image, showing intense signal at the area of, or close to, the AV-node revealing an active inflammation. This finding can explain the AV heart block of the patient.