What to know
- Lyme carditis occurs when Lyme disease bacteria enter the tissues of the heart. This can interfere with the normal movement of electrical signals from the heart’s upper to lower chambers, a process that coordinates the beating of the heart. The result is something physicians call “heart block,” which can vary in degree and change rapidly.
- Lyme carditis can either be treated with oral or intravenous (IV) antibiotics, depending on severity.

Symptoms
Lyme carditis can cause light-headedness, fainting, shortness of breath, heart palpitations, or chest pain. Patients with Lyme carditis usually have other symptoms such as fever and body aches, and they may have more specific symptoms of Lyme disease, such as the erythema migrans rash. Lyme carditis occurs in approximately one out of every hundred Lyme disease cases reported to ÐÇ¿ÕÓéÀÖ¹ÙÍø.
Third degree heart block

The heart on the top shows how an electrical signal flows from the atrioventricular node (AV node) to the chambers in the lower half of the heart, called the ventricles.
The heart on the bottom shows a case of third degree heart block. In this illustration, the electrical signal from the AV node to the ventricle is completely blocked. When this happens, the electrical signal of the atria (chambers at the top of the heart) does not transmit to the ventricles (chambers at the bottom of the heart), which causes the ventricles to beat at their own, slower rate.
ÐÇ¿ÕÓéÀÖ¹ÙÍø Expert Commentary
Dr. Joseph D. Forrestor, an Epidemic Intelligence Service Officer in the Bacterial Diseases Branch of ÐÇ¿ÕÓéÀÖ¹ÙÍø's Division of Vector-Borne Diseases.
Treatment
Lyme carditis can either be treated with oral or intravenous (IV) antibiotics, depending on severity (see tables below). Some patients might need a temporary pacemaker. Patients generally recover within 1-6 weeks.
Key points for healthcare providers
- Ask all patients with suspected Lyme disease about cardiac symptoms, e.g., palpitations, chest pain, light headedness, fainting, shortness of breath, and difficulty breathing with exertion.
- Ask patients with acute, unexplained cardiac symptoms about possible tick exposure and symptoms of Lyme disease.
- Treat patients with suspected Lyme carditis with appropriate antibiotics immediately – do not wait for Lyme disease test results. Patients with suspected severe Lyme carditis require immediate hospitalization for cardiac monitoring and intravenous antibiotics.
- Talk to patients about tick bite prevention.

Antibiotic treatment of Lyme carditis
Table 1. Mild (1st degree AV block with PR interval <300 milliseconds)
Age Category | Drug | Dosage | Maximum | Duration (days) | References |
---|---|---|---|---|---|
Adults | Doxycycline | 100 mg, twice per day orally | N/A | 14-21 | 4; 6-7; 13 |
Amoxicillin | 500 mg, three times per day orally | N/A | 14-21 | ||
Cefuroxime | 500 mg, twice per day orally | N/A | 14-21 | ||
Children (any age) |
Doxycycline | 4.4 mg/kg per day orally, divided into 2 doses | 100 mg per dose | 14-21 | 3; 5 |
Amoxicillin | 50 mg/kg per day orally, divided into 3 doses | 500 mg per dose | 14-21 | 3 | |
Cefuroxime | 30 mg/kg per day orally, divided into 2 doses | 500 mg per dose | 14-21 | 3 |
Table 2. Severe (symptomatic, 1st degree AV block with PR interval ≥300 milliseconds, 2nd or 3rd degree AV block)*
Age Category | Drug | Dosage | Maximum | Duration (days) | References |
---|---|---|---|---|---|
Adults | Ceftriaxone | 2 grams intravenously, once a day* | N/A | 14–21 | 1-2; 6-11; 13 |
Children (any age) |
Ceftriaxone | 50–75 mg/kg intravenously, once a day* | 2 grams per day | 14–21 | 3; 5; 12 |
*After resolution of symptoms and high-grade AV block, consider transitioning to oral antibiotics to complete treatment course (Table 1).
Treatment references
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