Following a tick bite, the bacteria that cause Lyme disease (Borrelia) can spread to various organs and tissues in the body. When the heart becomes infected with Borrelia, the disease state is called Lyme carditis. Between 4%-10% of people with untreated Lyme disease develop Lyme carditis, but only 1% of people with known Lyme disease will develop Lyme carditis because of treatment. Lyme carditis symptoms occur about one to two months after the onset of infection, making it difficult to associate the symptoms with a tick bite that occurred weeks before. Lyme carditis is three times more common in men than women. All age groups are at risk for Lyme carditis, but people under 50 years-old (including children) are affected more frequently.
How Does Lyme Carditis Occur?
When the spirochete bacteria Borrelia burgdorferi invades the heart tissue, it causes Lyme carditis. The bacteria can affect all the components of the heart, including the conduction system, the inner and outer membranes, the cardiac muscle, blood vessels, and heart valves. The immune system responds to the bacteria’s presence with a cascade of immune cells and cytokines, which results in oxidative damage and inflammation.
The most common manifestation of Lyme carditis is an electrical conduction block from the upper heart chambers to the lower heart chambers called an atrioventricular (AV) block. The electrical signal to the chamber that pumps blood throughout the body is delayed contributing to cardiovascular symptoms. Heart blocks are classified as first, second, and third-degree (complete) AV blocks and can rapidly fluctuate between degrees.
People with higher degree AV blocks are more likely to have more severe symptoms. One study found 54% of people with Lyme carditis had high-grade or complete AV block. In another study, 49% of people with Lyme carditis developed complete AV block. This means about half of people with Lyme carditis will develop complete heart block and require a pacemaker if treatment for Lyme disease is not promptly initiated.
Symptoms of Lyme Carditis
It can take one to two months for the bacteria that causes Lyme disease to affect the heart and cause Lyme carditis symptoms. Common symptoms include:
- Lightheadedness, dizziness
- Shortness of breath
- Chest pain
Although rare, Lyme carditis can be fatal if not diagnosed and treated promptly. Cardiac symptoms may be the only manifestation of Lyme disease, or a person may also experience other common Lyme disease symptoms such as pain, a rash, fevers, and neurological symptoms.
Case report: 16-year-old boy with Lyme carditis presenting with only palpitations Infectious disease doctors from the University of Minnesota report a case of a 16-year-old male with acute-onset palpitations and chest pain. Although the boy did not mention a rash on his leg and shoulder, the physicians discovered the rashes during an exam. An EKG detected an AV block. His blood count was normal, negative for a streptococcus infection, positive for Lyme disease, and negative for other tickborne infections. He was treated with intravenous ceftriaxone (an antibiotic) for ten days. When his EKG stabilized, he was discharged with a 28-day course of doxycycline. The authors concluded Lyme carditis in children has increased in the past two decades and suggest the importance of maintaining clinical suspicion in children with cardiac symptoms.
Diagnosis of Lyme Carditis
A Lyme carditis diagnosis should be considered in anyone who develops the above symptoms within one to two months of a tick bite. Lyme carditis should be included as a differential diagnosis in anyone who has engaged in outdoor activity and begins to experience the above symptoms one to two months later. Diagnosing Lyme carditis should not be limited to the northeastern United States since Lyme disease is found throughout the country.
A Lyme carditis diagnosis can be delayed (or not considered) in states like California, where Lyme disease is much more common than most physicians recognize.
An electrocardiogram (ECG or EKG) will detect an electrical conduction issue, including an AV block. A diagnosis of Lyme carditis would also include a positive blood test for Lyme disease. The conventional two-tiered test for Lyme is remarkably insensitive and, unfortunately, is the test most likely to be run in an emergency room or hospital setting. A western blot test for Lyme disease is more sensitive and should be requested. The most sensitive testing is performed through specialty laboratories but may not be practical for diagnosing Lyme carditis due to a longer turnaround time for results.
Suspicious Index in Lyme Carditis (SILC)
Lyme-literate cardiologist Adrian Baranchuk, MD, and colleagues developed a scoring system to evaluate the likelihood a patient’s AV block is caused by Lyme carditis. The Suspicious Index in Lyme Carditis (SILC) score is based on 108 clinically relevant Lyme carditis cases from the medical literature. Six criteria that increased Lyme carditis’s likelihood were extracted from the cases and given a weighted value. The mnemonic COSTAR is used for the following criteria with the clinical significance value in parenthesis:
- Constitutional symptoms – fever, fatigue, joint pain (2)
- Outdoor activity/endemic area (Northeast, upper Midwest, Northwest) (1)
- Sex – 3:1 male (1)
- Tick bite – (3)
- Age – <50 years old (1)
- Rash – erythema migrans rash present (4)
A high SILC score is 7-12, an intermediate SILC score is 3-6, and a low SILC score is 0-2. For example, a 15-year-old (1) male (1), in northern California, who plays golf (1), has a rash (4) on his leg and presents to the emergency room complaining of dizziness and shortness of breath would have a high SILC score. In addition to a standard cardiac workup, physicians should order a tickborne infection panel including Lyme disease.
Note, a rash caused by Lyme disease rarely presents as a stereotypical bullseye rash. Often the rash can be an oval-shaped and solid color. You can see images of a variety of Lyme disease rashes here.
Treatment for Lyme Carditis
The most common treatment for a cardiac electrical conduction disturbance such as atrioventricular block is the pacemaker’s insertion. However, if Lyme carditis is suspected and laboratory testing confirms the suspicion, the treatment of choice is antibiotics. Antibiotic therapy for Lyme carditis can reverse AV block and prevent a permanent pacemaker from being implanted. The proper diagnosis and treatment need to be executed swiftly to reverse heart block. Occasionally a temporary pacemaker is required while the antibiotics are working to resolve the infection.
A 2018 paper titled Lyme Carditis and Atrioventricular Block describes five cases of Lyme carditis. All five cases were men under the age of 35 years old. All the men had been exposed to outdoor activity in an endemic area. Only three men recalled a tick bite, and just one experienced the classic erythema migrans rash. All men had at least one constitutional symptom: fatigue, fever, headaches, neck stiffness, nausea, joint pain, or flu-like symptoms. The men had reported to the emergency department more than once before Lyme disease was finally suspected. Three of the men had complete heart block, and the other two developed second-degree AV block. Four of the men received intravenous ceftriaxone, and one received oral doxycycline. Two of the men required a temporary pacemaker, while all of the men avoided a permanent pacemaker. On average, AV block resolved within five days of initiating antibiotics.
What You Need to Know
Lyme carditis occurs in up to 10% of cases of Lyme disease. The onset of symptoms is usually one to two months after the onset of infection. Cardiac symptoms may be the only manifestation of Lyme carditis, or someone may also experience Lyme disease’s constitutional symptoms. Atrioventricular heart block is the most common Lyme carditis presentation and can cause lightheadedness, chest pain, shortness of breath, palpitations, and rarely death.
Lyme carditis should be suspected in anyone with a sudden onset of cardiac symptoms, mainly if they engaged in an outdoor activity one to two months before the onset of symptoms. Lyme carditis occurs more commonly in men under 50 years-old. A rash associated with Lyme disease can present with different characteristics than a bullseye rash. If a conduction disorder is diagnosed, physicians should immediately order a Lyme western blot test. Lyme carditis treated early with antibiotics can prevent the implantation of a permanent pacemaker and lead to a quick resolution of cardiac disease.