Phase 4 Block of the Right Bundle Branch Suggesting His-Purkinje System Involvement in Lyme Carditis

Open AccessPublished: December 01, 2020DOI:
We describe an adolescent with symptomatic high-grade AV block and evidence of phase 4 right bundle branch block, a previously unreported manifestation of infra-nodal conduction system involvement in LC.

A previously healthy 14-year-old boy presented via emergency medical services in mid-summer because of syncope (fainting).

Interesting findings:

  • Patient frequently hunts and fishes in wooded, Lyme-endemic region 
  • Didn’t remember tick bites or EM rash
  • Two weeks prior to ER visit patient had a runny nose, cough, abdominal pain, followed by headache and nausea.
  • In the ER he had bradycardia, altered mental status, headache, and vomiting.
  • Initial ECG showed complete heart block
  • He was given 2,000mg of IV Ceftriaxone every 24 hours
  • Testing supported clinical suspicion of Lyme
  • He was given a temporary pace-maker which was removed after 5 days of IV antibiotics and he was switched to oral doxycycline to complete a total of 21 days of antibiotics
  • After being monitored in hospital for 7 days, he was discharged with an auto-detecting wireless monitor until a follow-up appointment and stress test
  • Follow-up appointment patient was well with normal ECG



Case study states: 

Significant AV block due to LC occurs in about 1% of LD cases.

I believe this statistic is premature considering many do not test positive and therefore are undiagnosed. I’ve posted numerous articles where patients are sent packing even when they present with positive test results three times in a row! We will never know how many patients with AV block have an underlying tick-borne illness due to abysmal testing and the lack of training and experience of most doctors with tick-borne illness.

And then there’s that nagging concern about long-term effects and if 21 days of antibiotics were enough for his patient. It often isn’t.

Please see:

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