A 19-year-old woman with newly diagnosed Lyme disease presented with complete heart block and an accompanying escape rhythm with a right bundle branch block morphology. With antibiotics, her dysrhythmia resolved completely within 24 hours of presentation. This case highlights an unusual electrocardiographic manifestation of Lyme carditis.

Lyme disease is a multisystem disease caused by the spirochete Borrelia burgdorferi that is spread by the Ixodes scapularis tick.1  In the United States, Lyme disease is the most commonly reported vector-borne disease, with 26,203 confirmed cases (incidence of 8.1 cases/100,000 population) and 36,429 probable cases reported in 2016.2  Between 1993 and 2013, the incidence of Lyme disease in the United States increased 3-fold.3  Lyme disease symptomatology can vary from a localized skin lesion to a multisystem disease, and when there is cardiac involvement, it most commonly presents as atrioventricular (AV) block.2,3 

Lyme carditis manifestations affecting the AV node have been well documented and range from first- to third-degree heart block.2,3  Atrioventricular block is typically confined to the level of the compact AV node with a narrow QRS complex escape rhythm and infrequently results in infranodal block.2,4,5  Described here is the case of a 19-year-old patient presenting with Lyme carditis manifesting as complete heart block with an escape rhythm that has a right bundle branch block (RBBB) morphology.

A 19-year-old woman with a history of chronic headaches, phthisis bulbi with secondary right eye blindness, pseudotumor cerebri, and severe obesity status post–laparoscopic sleeve gastrectomy (3 years prior) presented with a 2-week history of acute on chronic bilateral frontal headaches and 2 days of dyspnea. The patient lived with her family in a heavily wooded area and was referred by her neurologist because of her new-onset dyspnea and worsening headaches despite increased doses of sumatriptan and topiramate. On arrival to the hospital, she also reported neck stiffness, nausea, and frontal headache that were not associated with photophobia, visual disturbances, or aura. She reported that she had no recent fevers or chills, orthopnea, chest pain, palpitations, lightheadedness, or dizziness.

Initial vital signs were significant for the following measurements: blood pressure, 99/46 mm Hg; heart rate, 46 bpm, and oxygen saturation of 100% on room air. Physical exam revealed several round, nonpruritic, painless, erythematous lesions with central clearing on the lower extremities, which were more prominent on the left and consistent with erythema migrans (Fig. 1).

Fig. 1

Left lower extremity showing round, erythematous rash with central clearing, consistent with erythema migrans.

Fig. 1

Left lower extremity showing round, erythematous rash with central clearing, consistent with erythema migrans.

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The results of basic metabolic panel, liver function test, and complete blood count with differential were within normal limits. A head computed tomography (CT) scan without contrast showed persistent right-sided phthisis bulbi (present on previous head CT scans) but no other acute intracranial abnormality. Chest x-ray findings were unremarkable. An electrocardiogram (ECG) showed sinus rhythm with a complete heart block and an escape rhythm at a rate of 51 bpm and a wide QRS (130 ms) with an RBBB morphology (Fig. 2A). Prior ECG reported a narrow QRS and normal PR interval. Echocardiogram showed normal left ventricular systolic and diastolic function, normal pulmonary artery systolic pressures, and no significant valvular pathology. The Suspicious Index in Lyme Carditis (SILC) score was 8, putting the patient at high risk for Lyme carditis (Table I).6 

Fig. 2

Serial ECGs during hospitalization. A) An ECG at presentation shows third-degree AV block with an escape rhythm at a rate of 51 bpm and wide QRS (130 ms) with a right bundle branch block morphology and rightward axis. B) An ECG from day 2 of hospitalization shows 2:1 AV block with narrow QRS (80 ms). C) Day 3 ECG shows sinus rhythm with Mobitz I (Wenckebach) AV block with narrow QRS (80 ms). D) Day 4 ECG shows sinus rhythm with first-degree AV delay with long PR interval (460 ms) and narrow QRS (90 ms) with 1:1 conduction. E) An ECG on day 6 of hospitalization shows complete resolution of AV block with normalization of PR interval (200 ms) and QRS width (90 ms). AV, atrioventricular; ECG, electrocardiogram.

Fig. 2

Serial ECGs during hospitalization. A) An ECG at presentation shows third-degree AV block with an escape rhythm at a rate of 51 bpm and wide QRS (130 ms) with a right bundle branch block morphology and rightward axis. B) An ECG from day 2 of hospitalization shows 2:1 AV block with narrow QRS (80 ms). C) Day 3 ECG shows sinus rhythm with Mobitz I (Wenckebach) AV block with narrow QRS (80 ms). D) Day 4 ECG shows sinus rhythm with first-degree AV delay with long PR interval (460 ms) and narrow QRS (90 ms) with 1:1 conduction. E) An ECG on day 6 of hospitalization shows complete resolution of AV block with normalization of PR interval (200 ms) and QRS width (90 ms). AV, atrioventricular; ECG, electrocardiogram.

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TABLE I

Suspicious Index in Lyme Carditis Risk Score

Suspicious Index in Lyme Carditis Risk Score
Suspicious Index in Lyme Carditis Risk Score

Lyme screen total antibody test results were positive for immunoglobulin M (IgM) and immunoglobulin G (IgG) (Lyme Index IgM/IgG was >8.0, suggesting acute infection). On lumbar puncture, clear, colorless cerebrospinal fluid containing normal glucose levels and a finding of lymphocytic pleocytosis was obtained, both of which are consistent with Lyme meningitis.

Ceftriaxone (2 g/d) was started on day 1 of hospitalization, and 7 doses were administered during hospitalization. Atrioventricular block associated with Lyme carditis most commonly resolves with antibiotics and does not require pacemaker placement.2  In this patient, daily ECGs demonstrated resolution of RBBB morphology after 24 hours of antibiotic therapy and stepwise improvement of AV block over the following 6 days, along with near-complete resolution of symptoms (Fig. 2). By antibiotic day 2, the patient reported increased strength and ability to walk around her room without the significant fatigue that she had experienced before hospitalization. For these reasons, pacemaker placement was deemed not necessary. The patient's erythematous lesions, headache, and neck stiffness also improved with antibiotic therapy. By discharge, her dyspnea had resolved and her heart rate had normalized. Given evidence of Lyme meningitis (ie, positive results of Lyme titer, lymphocytic pleocytosis in cerebrospinal fluid, and positive response to treatment), it was recommended to continue ceftriaxone for a full 14-day course.

The patient had multiple follow-up appointments with her cardiologist after discharge from the hospital, and ECGs consistently showed sinus rhythm with heart rates in the 60s and normal PR interval. The patient continued to see an infectious disease specialist as an outpatient and has reported some mild lingering fatigue since the completion of treatment. She was considered to have “post-Lyme syndrome” and continues to follow up with both cardiology and infectious disease specialists.

Lyme carditis was first described in 1980 and is considered a rare complication of Lyme disease affecting 1.5% to 10% of patients with Lyme disease in the United States.4,7  Lyme carditis tends to occur more often in males than in females by an estimated ratio of 3:1.8  The disease can present as myocarditis, myopericarditis, and/or endocarditis, but the most common presentation is AV block (~90%).9,10  Lyme carditis is a clinical diagnosis that can be aided by the use of tools such as the SILC risk score system, which uses symptomology, recent activity, and patient demographics to guide the diagnosis. The pathophysiology of Lyme myocarditis involves direct invasion of the spirochete into cardiac tissue, as demonstrated by autopsies.11  The mechanism by which Lyme disease affects the AV node is believed to involve direct invasion of the AV node by the spirochete.2  Varying degrees of AV block are often observed, and the level of block is most commonly at the AV node, with rare reports involving block below this level.2 

Although several cases of Lyme disease presenting as left or alternating left and RBBB exist in the literature, few cases of Lyme disease presenting with an RBBB morphology have been reported. One case had a preexisting RBBB, and another case described a new-onset RBBB that resolved over 7 days.12,13  A more recently published case report involved a patient with Lyme carditis who had high-grade AV block and possible phase 4 block of the right bundle branch.14  Although the case here is not the first to describe rapid resolution of Lyme carditis–related ECG abnormalities, this case highlights an unusual presentation of Lyme carditis in which there is complete heart block and an escape rhythm with an RBBB morphology.15  Although an electrophysiologic study was not performed, multiple possible mechanisms for the right bundle escape morphology exist that may include either block within the distal portion of the AV node or infranodal block. One study recommends pre-discharge (or within 10 days of discharge) stress testing upon achievement of 1:1 conduction to assess for AV conduction stability2 ; however, stress testing was not performed in this case, which is a limitation. With antibiotic therapy, serial ECGs showed stepwise improvement in AV conduction and full resolution of the patient's presenting symptoms over the following week.

Lyme carditis is an uncommon, but clinically significant manifestation of infection with B burgdorferi. Identification of the electrocardiographic manifestations of Lyme carditis is paramount and may be the initial clinical manifestation recognized by the treating physician. Although AV block due to Lyme disease is typically confined to the AV node with a narrow QRS complex, additional block resulting in an RBBB morphology is also possible and can resolve rapidly with antibiotic therapy, as evidenced in this case.

Conflict of Interest Disclosure: None

Funding/Support: None

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