American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the appropriate treatment for Lyme disease when there is a first-degree heart block?

1. Ceftriaxone

2. Oral doxycycline

3. Intravenous penicillin G

4. Oral azithromycin

The correct answer is: Oral doxycycline

The appropriate treatment for Lyme disease when there is a first-degree heart block is oral doxycycline. Lyme disease, caused by the Borrelia burgdorferi bacterium, can lead to various manifestations, including cardiac complications such as heart block. In cases where a patient presents with Lyme carditis, which is the term used for the cardiac manifestations of Lyme disease, including first-degree heart block, oral doxycycline is the first-line treatment option. This antibiotic effectively targets the causative organism and is particularly suitable for treating early localized or early disseminated Lyme disease, including instances where the patient exhibits neurologic or cardiac involvement. Doxycycline is often preferred in adults and children over 8 years old because of its efficacy, good bioavailability, and safety profile. It can be administered orally, making it convenient for outpatient management in cases of mild to moderate Lyme carditis without more severe cardiac complications. Other options like ceftriaxone and intravenous penicillin G may be reserved for more severe manifestations of Lyme disease or in patients who are unable to tolerate oral medications or have significant neurological involvement. Azithromycin is not a recommended treatment for Lyme disease and has limited efficacy against the bacteria responsible for the infection. Thus, for a case of Lyme disease presenting