American Board of Internal Medicine (ABIM) Certification Practice Exam

In cases of Lyme disease with heart block greater than first degree, what is the recommended treatment?

1. Ceftriaxone or intravenous penicillin G

2. Oral amoxicillin

3. Oral doxycycline

4. Oral clarithromycin

The correct answer is: Ceftriaxone or intravenous penicillin G

In cases of Lyme disease where the patient presents with a heart block greater than first degree, the recommended treatment involves the use of intravenous antibiotics such as ceftriaxone or intravenous penicillin G. This recommendation is based on the fact that higher degrees of heart block indicate a more severe manifestation of Lyme carditis, which can potentially lead to serious complications if not treated appropriately. The use of intravenous therapy is deemed necessary in these cases because it ensures adequate penetration of the antibiotic in the central nervous system and in cases where the infection may be more extensive or systemic. This is especially pertinent in patients who may be experiencing significant cardiac symptoms or those with advanced degrees of heart block, as they could benefit from the enhanced efficacy of intravenous medications. In contrast, oral antibiotics like amoxicillin, doxycycline, or clarithromycin, while effective for treating the early stages of Lyme disease or milder cases, are not considered suitable in the presence of a significant heart block. These medications may not achieve the necessary drug levels in serious situations and might lead to inadequate treatment of the Lyme carditis that is causing the heart block. As such, intravenous ceftriaxone or penicillin remains the standard recommendation in these acute settings.