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first-degree AV block and have a P-R interval of ≥300 ms
should be hospitalized.9 Continuous monitoring is recommended for all hospitalized patients.
Antibiotic therapy. Lyme carditis can be self-limited; however, antibiotics are required to shorten the disease course,
minimize cardiovascular complications, and prevent other
sequelae of Lyme disease.3 With appropriate treatment, resolution generally occurs within 3 to 4 weeks, but may take
considerably longer when diagnosis and treatment are
delayed.3 Recommended classes of antibiotics include those
that have demonstrated the greatest effectiveness against
Borrelia spirochete, with β-lactams, particularly cephalosporins, and tetracyclines as preferred agents.3 Treatment guidelines established by the Infectious Diseases Society of
America recommend that patients with Lyme carditis be
treated with either oral or parenteral antibiotic therapy for a
duration of 14 days.9 The preferred parenteral agent for Lyme
carditis is ceftriaxone, and the preferred oral agents include
amoxicillin, doxycycline, and cefuroxime axetil.9 Even
though no evidence exists to suggest that parenteral antibiotic therapy is more efficacious than oral antibiotic therapy,
a parenteral antibiotic is recommended for initial treatment
of hospitalized patients.9 The parenteral antibiotic should be
continued until the high-degree AV block has resolved and
the P-R internal has deceased to <300 ms, after which the
patient should be transitioned to an oral antibiotic for completion of therapy.9
Device therapy. A temporary pacemaker may be required in
patients with advanced heart block during the duration of the
block, and the pacemaker may be discontinued when the
advanced heart block has resolved.9 Implantation of a permanent pacemaker is rare. An evaluation of 105 case reports of
patients with Lyme carditis revealed that 35% of patients
required a temporary pacemaker, and only 5.7% of patients
required a permanent pacemaker of which only 1 patient
remained pacer dependent.7 In a systematic review of 45
patients with Lyme carditis, only 2 patients required a permanent pacemaker.6
The patient in this case report was treated with ceftriaxone, as he required hospitalization due to the severity of his
symptoms. He received ceftriaxone for a total duration of 33
days, which includes 5 days of therapy during hospitalization
and 28 days of therapy on an outpatient basis, even though
the guidelines recommend only 14 days of therapy. Arguably,
he could have been transitioned to oral therapy upon discharge as his second-degree AV block had reverted to firstdegree AV block 2 days prior to discharge. It is unclear why
the patient received a longer than recommended duration of
antibiotic therapy and why he was not transitioned to oral
therapy upon discharge. This highlights the importance of
health care practitioners being aware of and adhering to the
guideline recommendations, and presents an opportunity for
pharmacists to ensure that the discharge pharmacologic therapy is in accordance with guideline recommendations.

This case report illustrates an acute onset, rapidly fluctuating AV block in a patient with Lyme carditis. As the AV block
in Lyme carditis can progress rapidly from a first-degree to a
complete block within minutes, especially when the P-R interval is ≥300 ms, it is vital that hospitalized patients with a presumptive diagnosis of Lyme carditis are admitted to the
telemetry unit for close monitoring. In addition, Lyme carditis
should be considered as a differential diagnosis in patients with
an AV block of an unknown etiology. Appropriate antibiotic
therapy should be initiated soon after establishing a diagnosis
of Lyme carditis to minimize cardiovascular complications and
prevent other sequelae of Lyme disease.

Conclusion
This case report highlights the importance of considering
Lyme carditis as an etiology of acute onset, fluctuating AV
block. An accurate and timely diagnosis of Lyme carditis can
result in appropriate treatment which can prevent potentially
severe cardiac arrhythmias; unnecessary interventions, such
as pacemaker insertion; and later complications of Lyme
disease.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.

Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.

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