Can Lyme Disease Cause Heart Block? SILC Score and Lyme Carditis
Lyme carditis can cause heart block and abnormal heart rhythms
The SILC score may help identify suspected Lyme-induced AV block
Early recognition may prevent serious cardiac complications
Lyme disease can occasionally spread to the heart and cause Lyme carditis, a serious complication that may affect the heart’s electrical conduction system.1
One important cardiac manifestation is atrioventricular block, also called AV block or heart block. In some patients, this can lead to bradycardia, lightheadedness, fainting, chest symptoms, or hospitalization.1
For a broader overview of cardiac complications, visit our Lyme Carditis hub.
Lyme Disease Heart Block in a Young Adult
Kerndt and colleagues described a 20-year-old camp counselor in Wisconsin who developed early disseminated Lyme carditis with high-degree atrioventricular block.1
The patient first developed a circular rash on his arm, extreme fatigue, and a fever of 101°F. When admitted to the hospital, he reported malaise and lightheadedness.1
He also developed intermittent symptomatic bradycardia, with an average heart rate of 40 beats per minute and one severe episode dropping to 15 beats per minute over five seconds.1
His examination revealed multiple rashes on his arms, legs, and back. The lesions had raised borders and central clearing consistent with erythema migrans, the classic rash of Lyme disease.1
ECG Findings and Lyme Carditis Diagnosis
An electrocardiogram showed sinus bradycardia with first-degree AV block.1
Doctors suspected Lyme disease had induced the heart block and prescribed a 28-day course of intravenous ceftriaxone.1
Western blot testing was positive for Lyme disease, with IgM reactivity to bands 23, 39, and 41 and IgG reactivity to bands 18, 23, 39, 41, and 93.1
Given the ECG findings and serology, the patient was diagnosed with early disseminated Lyme carditis.1
Early Treatment Helped Reverse the Heart Block
Within days of treatment, the patient’s heart block progressively improved from high-grade AV block to second-degree AV block.1
At follow-up, his symptoms had completely resolved. Repeat ECG showed normal sinus rhythm with complete resolution of the previous AV block.1
This case highlights the importance of recognizing Lyme carditis early, especially in young patients with new-onset AV block, rash, outdoor exposure, or symptoms suggestive of tick-borne illness.
What Is the SILC Score?
The Suspicious Index in Lyme Carditis, known as the SILC score, is a clinical scoring system developed to help identify patients whose AV block may be caused by Lyme carditis.1
The SILC score considers factors such as:
- age
- sex
- outdoor activity
- endemic exposure
- known tick bite
- erythema migrans rash
- symptoms compatible with Lyme disease
Kerndt and colleagues noted that the cumulative SILC score categorizes patients by level of suspicion for Lyme disease as the cause of AV block.1
The 20-year-old patient had a SILC score of 9, placing him in the high-suspicion category for early disseminated Lyme carditis.1
Why Lyme Carditis Can Be Missed
Lyme carditis may be overlooked when patients present primarily with cardiac symptoms rather than joint pain, fever, or a recognized tick bite.
Patients may present with:
- lightheadedness
- fainting or near-fainting
- slow heart rate
- palpitations
- chest discomfort
- shortness of breath
- new AV block
Delayed recognition may increase the risk of complications, including the potential need for temporary pacing or even unnecessary permanent pacemaker placement.
For more on delayed recognition, visit our Lyme Disease Misdiagnosis article.
Frequently Asked Questions
Can Lyme disease cause heart block?
Yes. Lyme carditis can affect the heart’s electrical conduction system and cause AV block or heart block.1
What is the SILC score?
The SILC score, or Suspicious Index in Lyme Carditis, helps clinicians estimate whether AV block may be caused by Lyme carditis.1
Can Lyme disease cause AV block?
Yes. Lyme carditis may cause first-degree, second-degree, or high-degree AV block.1
Can Lyme carditis improve with antibiotics?
Many patients improve with appropriate antibiotic treatment when Lyme carditis is recognized early.1
Can Lyme carditis require a pacemaker?
Some severe cases may require temporary pacing, but early diagnosis and treatment may help avoid unnecessary permanent pacemaker placement.
What symptoms suggest Lyme carditis?
Symptoms may include lightheadedness, fainting, palpitations, chest discomfort, shortness of breath, bradycardia, or new heart block.
Clinical Takeaway
Lyme disease can cause Lyme carditis, including AV block, bradycardia, and serious conduction abnormalities.
The SILC score may help clinicians recognize suspected Lyme-induced heart block, especially in young patients from endemic areas with outdoor exposure or erythema migrans.
New-onset heart block in a patient with possible Lyme exposure should prompt consideration of Lyme carditis before permanent pacing decisions are made.
Related Articles
These related articles explore Lyme carditis, cardiac complications, AV block, and delayed recognition of Lyme disease.
Lyme Carditis Causes Complete Heart Block in a 26-Year-Old Man
Reversible Complete Heart Block Due to Lyme Disease
Severe Cardiac Problems in a 15-Year-Old Boy
Delayed Lyme Disease Diagnosis
Lyme Disease Heart Palpitations
References
- Kerndt C. Early Disseminated Lyme Carditis Inducing High-Degree Atrioventricular Block. Case Reports in Cardiology. 2020;Article ID 5309285. https://doi.org/10.1155/2020/5309285.
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
Hi Dr.Cameron- I wAs a patient of yours bk in 2008-12. I was diagnosed late stage.
You worked with me bk Forth from saratoga to mt kisco. You did start my journey bk to life’. Took a few years, with your help- 75% of The fatigue, heart issue, Neuropathy, joints, sensory overload, etc… did seem to disappear. I can have severe moments of brain fog, short term memory. I did see a neuropthamologist bk then. My eyes did play tricks. This did subside. But- did seem to come & go. Over the years I wrote it off as normal aging. Until this past year- my vision does change often. Blurry, far sighted, near sighted & can randomly not see at night. Seem to be progressing too fast. With covid- I put appt off until this month. I just read your article about lyme & eye issues. Is there a certain test or tests I should ask for in regards to confirming if this is lyme related? Any insight would be appreciated. I will always be grateful for the time, & expertise You & your staff gave me. You did assist in bringing me bk to life. Thank you for never giving up on lyme & having a voice.
I am glad you improved. It is still frustrating to have continued symptoms. I do not have any specific test for your eyes that I am aware of. Call my office at 914 666 4665 if you have any questions.
Hi! I read this as a person diagnosed a couple of years ago with a first degree heart block. Previously, I was treated with a PICC line and penicillin pump for a 28 day cycle for Neuro Lyme. That original Lyme had gone untreated for at least 10 years as my GP poo-poo’d Lyme results and ignored my complaints.
I have borderline deafness that no one can explain, and this first degree heart block. I’m suspicious that both may be from the Lyme infection.
As for the heart block, I was given a stress test, monitored for a month, told it’s normal for bp to get down to 30 on occasion (I am NOT an athlete) and sent home.
I’m feeling a bit nervous, and wondering if this could all be down to the Lyme, and what else could be lying in wait for me. I’m 53 and was diagnosed with the Neuro Lyme in 2016, 1st degree heart block found in 2020.
I always advise my patients to again include a doctor experienced in treating Lyme disease. Some of them have cardiac and Lyme disease issues as both are common.
Interesting article and important issue. It is particularly important that the authors remark that treatment was started because of the ‘suspicion’ of Lyme carditis. Waiting for confirmatory lab testing, especially if the testing is negative or equivocal, can be disastrous. Also glad that they investigated for cardiac dysfunction in addition to the heartblock. Although perhaps not the most common manifestation of heart involvement in Lyme it does occur. They talk about the specificity of serology, but omit discussion of the sensitivity. I would hope that they would have continued ceftriaxone based on clinical presentation and course while they evaluated for other etiologies, though their writing suggests that would not be the expected course of action; perhaps an important take away thought. The SILC scoring can indeed be useful as a way of codifying a useful and practical approach one might use regardless of familiarity with Lyme disease and its manifestations! Thanks for this interesting post. And for all you do all the time!