Reversible atrioventricular block and the importance of close follow-up: Two cases of Lyme carditis

Abstract

Lyme carditis is an uncommon presentation of the early-disseminated phase of Lyme disease, although it is recognizable and often curable. Because of its rarity, diagnosing Lyme carditis requires a high level of suspicion, especially when young patients in certain endemic areas present with symptoms of bradycardia and/or evidence of high-degree atrioventricular (AV) block. Temporary cardiac pacing along with antibiotic therapy has been shown to aid in the management of Lyme carditis until symptoms and conduction blocks have resolved. Herein, we report two cases of Lyme carditis-induced AV block that were successfully managed and reversed with temporary cardiac pacing and antibiotics. In order to monitor for any late sequela that may arise, we also recommend close follow-up for patients treated for Lyme carditis with high-degree AV block.

<Learning objective: Lyme carditis manifests as a conduction system disease, predominantly involving the atrioventricular (AV) node. It can present without the classical signs of Lyme disease. It is critical to have a high suspicion of Lyme carditis in patients who present with symptoms of bradycardia or high-degree AV block in high prevalence areas. Early initiation of antibiotics, along with external temporary pacing, dramatically improves mortality rates. Close follow-up is important in patients that develop high-degree AV block.>

Introduction

Lyme disease is a tick-borne infection caused by the spirochete Borrelia burgdorferi and is most commonly transmitted by the deer tick Ixodes scapularis [1]. It is endemic to the Northeastern and Mid-Atlantic regions of the USA. Acute infection typically presents with erythema migrans at the site of the tick bite as well as fever and constitutional symptoms. Early recognition and treatment prevents dissemination of the infection. However, if treatment is delayed, the infection can spread to affect other organs.

Cardiac involvement affects about 1% of patients with Lyme disease and 4–10% of untreated patients with Lyme disease [2]. While males have a slightly greater incidence of Lyme disease, there is about a 3:1 male predominance of Lyme carditis [3]. Lyme carditis often manifests itself by affecting the electrical conduction system of the heart, specifically the atrioventricular (AV) node, producing varying degrees of AV conduction block [2]. It may progress from first- to third-degree (complete) heart block within minutes to hours, and be fatal if not treated. Patients may present asymptomatic or with chest pain, lightheadedness, syncope, or even sudden cardiac death [2].

Treatment is critical to prevent complications of Lyme disease and reduce the duration of cardiac involvement. Temporary pacing along with antibiotic therapy may be needed in cases of severe or symptomatic AV block and/or hemodynamic instability. We present two cases of Lyme carditis and their successful management with temporary cardiac pacing and antibiotics, as well as the importance of close follow-up in patients that develop high-degree AV block.

Case report #1

A 26-year-old male from upstate New York was evaluated in the emergency department for a two-day history of dizziness, fatigue, and chest pain. Three weeks previously, the patient reported spending time in the woods, although denied any tick bite. However, two weeks previously, he found a tick on his bed. Since that point, he began to develop myalgias, fatigue, and a low-grade fever. He remained asymptomatic until two days before presentation when he began experiencing chest pain and tightness on minimal exertion along with lightheadedness.

Physical examination was unremarkable, except for bradycardia. He was in no distress and had no evidence of any rash or neurological abnormality. He was afebrile with a heart rate of 28 beats/minute and a blood pressure of 160/75 mmHg. Laboratory data, including troponins, complete blood count, and electrolytes were within normal limits. Electrocardiogram showed second-degree AV block Mobitz type 2 with a 4:1 conduction pattern (Fig. 1). The patient was admitted and sent to the cardiac care unit after he had an emergent temporary pacemaker placement along with prompt initiation of 2 g of IV ceftriaxone. Two days after admission, he dropped to first-degree AV block, which then returned to normal sinus rhythm without any evidence of conduction disease after four days. A few days later, serological testing returned positive for Lyme disease. The temporary pacemaker was removed and he was discharged on oral doxycycline for 21 days.

Fig. 1.

Electrocardiogram showing second-degree atrioventricular block Mobitz type 2 with a 4:1 conduction pattern and a heart rate of 28 beats/minute.

Case report #2

An 18-year-old male from upstate New York presented to the emergency department with episodes of lightheadedness and dizziness that began 5–6 h previously. These episodes started when he woke up and continued intermittently, generally lasting a few seconds. However, in one episode he became pale, started shaking, and was unresponsive for two minutes. He remained confused for several minutes and could not recall the events after regaining consciousness.

Over the previous two weeks, the patient reported generalized body aches and low-grade fever. Further questioning revealed that he and his family live in a wooded area with dogs and cats that were found recently with many ticks. He also spends time outdoors, but denies any tick bite.

Vital signs and physical examination were unremarkable. He had a blood pressure of 120/60 mmHg and heart rate of 84 beats/minute. He was in no distress and had no evidence of any rash or neurological abnormality. Laboratory data, including troponins, complete blood count, and electrolytes were within normal limits. Electrocardiogram showed third-degree (complete) heart block (Fig. 2). He was admitted and had an emergent temporary pacemaker placed along with the prompt initiation of 2 g of IV ceftriaxone. Three days after admission, the patient went from third- to second-degree AV block, and then to first-degree AV block until complete reversion to normal sinus rhythm without any conduction disease after five days. A few days later, serological testing returned positive for Lyme disease. At that point, the temporary pacemaker was removed and he was discharged on oral doxycycline for 21 days.

Fig. 2.

Electrocardiogram showing third-degree (complete) atrioventricular block.

Two months after discharge, the patient returned to the emergency department after an episode of lightheadedness. Complete cardiac workup and electrocardiogram (Fig. 3) were within normal limits. An event monitor was placed to rule out any missed episodes of bradycardia or AV block secondary to potential AV nodal scarring from Lyme carditis, and he was scheduled for a follow-up appointment two weeks later.

Fig. 3.

Electrocardiogram showing normal sinus rhythm.

Discussion

Lyme carditis has a broad timeline for its clinical manifestations. It can manifest within 4–5 days or as late as 6–7 months after a tick bite. The association of Lyme carditis with AV conduction system disease is well known. A study of over 100 patients revealed 12% had first-degree AV block, 16% had second-degree AV block, and 49% had third-degree heart block upon presentation [4]. The remaining 23% of patients had no conduction abnormalities. Of those affected, 35% required temporary pacing and only 5.7% required a permanent pacemaker.

In the early-disseminated stage of Lyme disease, spirochetes spread hematogenously to certain organ systems. At autopsy, spirochetes have been isolated in the myocardial tissue from patients who had myocarditis or pancarditis [5]. The edema and inflammation invoked by spirochetes is a potential cause of the AV nodal disease and consequential conduction defects.

The Infectious Diseases Society of America (IDSA) recommends that patients with AV block and/or myopericarditis be treated with either oral or parenteral antibiotic therapy for 14–21 days [6]. In symptomatic patients or those with second- or third-degree AV block, IDSA recommends hospitalization and continuous cardiac monitoring. This also includes patients with first-degree AV block with a PR interval >300 ms, as they are at risk of rapidly progressing to higher-degree AV blocks [6]. Empiric IV antibiotic treatment (e.g. ceftriaxone) is recommended as the initial treatment for hospitalized patients. For those with symptomatic advanced heart block, a temporary pacemaker may also be required until the block resolves; after which, patients can be discharged on oral antibiotics [6].

In both cases, the patients appeared to develop early-disseminated Lyme disease with cardiac involvement about two weeks after the initial onset of symptoms. Prompt workup, temporary cardiac pacing, and diagnosis of Lyme disease aided in rapid management and treatment. Within a week of antibiotic treatment, they reverted back to normal sinus rhythm and the temporary pacemakers were removed. Both patients were asymptomatic and continued oral antibiotics on discharge.

One of the patients presented two months later feeling lightheaded. His work-up was unremarkable, but an event monitor was placed to rule out the possibility of any undiagnosed episodes of bradycardia or AV block. This raises some new questions. Does a history of Lyme carditis pose a potential risk of chronic AV nodal conduction disease that may reveal itself months later? And, can the presence of this form of AV nodal conduction disease have paroxysmal manifestations, making it difficult to diagnose with a one-time electrocardiogram?

Temporary cardiac pacing along with antibiotic therapy has been found to be useful in the management of symptomatic Lyme carditis until symptoms and conduction blocks resolve. Having a high clinical suspicion allows for timely recognition of Lyme carditis in young patients that present with symptoms of bradycardia and/or AV block in certain geographic areas as well as immediate initiation of treatment. This is key in achieving a favorable prognosis and to avoid worsening heart block and the need for a permanent pacemaker. Close follow-up is important for patients that have been treated for Lyme carditis with high-degree AV block due to the potential risk of late sequela that should be monitored for and managed early to prevent future morbidity and even mortality.

Conflicts of interest

None.