_http://journals.lww.com/em-news/Fulltex ... ree.9.aspx_
(http://journals.lww.com/em-news/Fulltext/2005/11000/Lyme_Carditis__From_Asymptomatic_First_De
gree.9.aspx)
Lyme Carditis: From Asymptomatic First-Degree Heart Block to Dilated
Cardiomyopathy
A previously healthy 17-year-old girl was brought to our ED after a
syncopal episode that occurred while she was standing in her kitchen earlier that
evening. According to her mother, who was speaking to her at the time of
the episode, she suddenly dropped to her knees and then lost consciousness
for approximately 10 to 20 seconds. When she regained consciousness, she
quickly returned to her baseline mental status, denying any confusion or
lethargy. In fact, during our interview with the patient, she reported feeling
great immediately after this event.
Her ECG showed an accelerated junctional rhythm with a rate of 120 beats
per minute. Further history revealed that she had been seen by her
pediatrician on the previous day for evaluation of a rash. She described the rash as
it appeared that day as several erythematous patches approximately 5 cm to
6 cm in diameter that were located on her left forearm, abdomen, and
thighs. She denied any previous skin conditions such as eczema or psoriasis, and
could not recall any recent exposures to plants, ticks, new medications,
or cleaning products. She was given a prescription for diphenhydramine, and
aside from some general fatigue, was doing well up to the time of her
syncopal event.
A repeat ECG showed a first-degree AV block with a markedly prolonged PR
interval of greater than 400 ms. Physical exam revealed multiple annular,
erythematous, macular lesions with central clearing. (Figures 1 and 2.) These
were located on her torso, back, and upper and lower extremities.
Although the patient could not recall any recent tick exposure, she lived
in an area endemic for Lyme disease, and reported being outdoors for much
of each day. The diagnosis of Lyme carditis was made, she was started on
ceftriaxone for presumed disseminated Lyme disease, and she was admitted to
the pediatric ICU for monitoring
Diagnosis
The diagnosis of Lyme carditis can be relatively straightforward when new
onset conduction abnormalities occur simultaneously with other signs and
symptoms of disseminated Lyme disease, as was the case with this patient. If
the cardiac manifestations occur in isolation, however, a high index of
suspicion is necessary to make the diagnosis. The diagnosis can be confirmed
by serology testing using ELISA or Western blot analysis, but it is
important to point out that serology testing will be negative during the first
several weeks of infection. Eliciting a history of tick exposure, erythema
migrans rash, or outdoor activities in an endemic area is important when
considering the diagnosis.
Although any area of the conduction system can be affected, the most
common presentation is a first-degree AV block. One of the hallmarks of Lyme
carditis is the rapidity with which the conduction abnormalities can change.
It is not uncommon to see several different degrees of AV block within a
relatively short period of time. It is estimated that approximately 50 percent
of patients with Lyme carditis will develop complete heart block during
the course of their disease. (Clin Pediatr Emerg Med 2004;5[5].) Those with a
markedly prolonged PR interval (≥300 ms) seem to be at the greatest risk
for progression to complete heart block. The ECGs shown here were all
recorded from another of our patients with Lyme carditis over a period of only 24
hours. (Figures 3-5.) This patient was a 58-year-old man who presented
with atypical chest pain, no rash, and no known tick exposure. The diagnosis
was confirmed by serologic testing, and he recovered completely.
Treatment
Once the diagnosis of Lyme carditis is made, antibiotics effective against
Borrelia burgdorferi should be initiated. Although there is good evidence
that disseminated Lyme disease should be treated with parenteral
antibiotics, there is no consensus regarding treatment for isolated Lyme carditis.
The Infectious Diseases Society of America recommends oral therapy with
doxycycline or amoxicillin for asymptomatic 1st or 2nd degree heart block.
Furthermore, there is no evidence that treatment with antibiotics alters the
course of the conduction abnormalities seen in Lyme carditis. It seems prudent
in patients with high-grade AV block caused by Lyme disease, however, that
parenteral antibiotic therapy should be administered in a monitored setting
Parenteral antibiotic choices include ceftriaxone 2 g QD, cefotaxime 2 g
BID, or penicillin G 200,000 to 400,000 units/kg/day divided into six doses.
Duration of treatment for disseminated disease should be for four weeks.
Oral regimens include doxycycline 100 mg BID or amoxicillin 500 mg TID with
treatment durations ranging from 14 to 21 days. (Clin Infect Dis
2000;31(Suppl: 1):S1-14.)
Symptomatic patients should be admitted to a monitored bed during
initiation of therapy due to the potential of rapid progression to a high-grade
block. It is worth noting that bradycardia in patients with complete heart
block typically will not respond to atropine, and temporary pacing may be
necessary.
The prognosis for patients with Lyme disease and cardiac involvement is
very good. Most conduction abnormalities will resolve within three to six
days. Occasionally a persistent 1st degree AV block persists for several
months after treatment, but these are typically well tolerated and also will
resolve spontaneously. Very rarely, patients can have a persistent high-grade
block that necessitates pacemaker placement. There have been case reports
of dilated cardiomyopathy secondary to Lyme myocarditis, but these appear to
be extremely rare and respond well to appropriate therapy.
Although this case was a relatively straightforward diagnosis given the
multiple erythema migrans lesions in a new conduction abnormality in a young
woman who resided in an area endemic for Lyme disease, Lyme carditis often
can present a challenging diagnostic dilemma, particularly when the cardiac
manifestations of this infection present in isolation. A thorough history
focusing on risk factors and subtle symptoms combined with a high index of
suspicion is necessary for any patient who presents with a newly diagnosed
heart block
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