Lyme Carditis and Heart Block: When Lyme Disease Slows the Heart
You feel lightheaded—like you might pass out.
Your heart rate is dangerously slow.
This may be Lyme disease affecting the heart.
Lyme carditis is a serious complication of Lyme disease that can disrupt the heart’s electrical system—sometimes leading to complete heart block.
This is where symptoms can be mistaken for something else—until the rhythm becomes dangerous.
This is where symptoms can become dangerous quickly. What begins as fatigue or lightheadedness may progress to life-threatening rhythm disturbances.
Start here: Lyme disease symptoms guide
What Happened in This Lyme Carditis Case?
How severe can Lyme carditis become?
A patient presented to the emergency department with presyncope, including lightheadedness, muscle weakness, and worsening fatigue.
Telemetry monitoring revealed a 2:1 atrioventricular (AV) block alternating with complete heart block, along with a junctional escape rhythm at approximately 30 beats per minute (Chaudhry et al., 2017).
This is where conduction abnormalities can rapidly worsen.
Despite initiation of intravenous ceftriaxone for suspected Lyme disease, the patient’s condition deteriorated within 24 hours.
He developed complete heart block with loss of junctional escape rhythm and episodes of asystole, resulting in near syncope.
Why Can Lyme Disease Cause Heart Block?
This is where things become more complicated.
Lyme carditis is caused by direct invasion of cardiac tissue by Borrelia burgdorferi, the bacterium responsible for Lyme disease.
This leads to inflammation of the heart’s conduction system, disrupting normal electrical signaling.
Lyme carditis is a well-recognized cause of reversible heart block in clinical practice.
Pathologic findings may include:
- Transmural inflammation with macrophages and neutrophils
- Lymphocytic infiltration
- Interstitial fibrosis
- Vasculitis affecting small and large vessels
- Myocarditis and pericarditis
In some cases, more severe complications such as acute coronary syndromes or coronary artery aneurysms may occur.
What Treatment Was Required?
What happens when the heart rhythm becomes unstable?
Due to worsening conduction abnormalities, the patient required emergent pacing.
A temporary pacemaker was placed using right subclavian access, with an active fixation lead to stabilize cardiac rhythm.
Serologic testing confirmed Lyme disease with positive ELISA and Western blot IgM.
This is where rapid intervention can be life-saving.
The patient was discharged after 12 days and continued intravenous antibiotic therapy.
The pacemaker was successfully removed on day 19 as cardiac conduction recovered.
See also: Lyme carditis and pacemaker avoidance
What Are the Warning Signs of Lyme Carditis?
Symptoms often begin subtly—but can escalate quickly:
- Lightheadedness or presyncope
- Fainting (syncope)
- Chest discomfort
- Shortness of breath
- Unexplained fatigue
- Slow or irregular heartbeat
These symptoms may appear suddenly—and can worsen quickly.
See related symptoms in Lyme heart problems.
Clinical Takeaway
Lyme carditis can cause serious—and potentially life-threatening—heart rhythm abnormalities.
Early recognition is critical, especially in patients with unexplained heart block or fainting.
If heart symptoms don’t fit the usual pattern, it’s worth asking why—again.
Related Reading
12-year-old boy suffers cardiac arrest due to Lyme disease
Reversible complete heart block due to Lyme disease
Another Lyme carditis case
Lyme myocarditis in adolescents
References
- Chaudhry, M. A., Satti, S. D., & Friedlander, I. R. (2017). Lyme carditis with complete heart block: Management with an external pacemaker. Clinical Case Reports, 5(6), 915–918.
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
I have the same thing…..pacemaker in for a moth now…..they called it AV node dysfunction
I had complained of palpitations for years, EKG, Echo, Holter all normal. Then thought I was having a heart attack but it was Supraventricular tachycardia, had an ablation and spent 6 days in the ICU. Because I didn’t have a fever they ignored the fact I said I had Lyme but wasn’t CDC positive anymore. Now I need another ablation my heart is fluttering and keeping me up at night……I need a real doctor!
There is not enough known about cardiac manifestations of Lyme disease. I would be reasonable to see a doctor with experience treating Lyme disease as part of your evaluation particularly given you apparently had Lyme disease in the past.
Hi dana, did you ever take antibiotics for Lyme prior to the palpitations?
After surviving 4 cardiac arrests due(back to back to back to back) to Lyme Carditis, I received an implant. Looking back at the day of the Cardiac arrests, I recall the symptoms being identical to heart attack patients. i.e. muscle weakness, headaches, neck pain, arm weakness, fatigue, etc. Warning to all: Do not ignore these symptoms even though it’s not recognizable. It will kill you if it goes unchecked.
Hello
My son had lyme carditis my concern is was he treated adequately? What would confirm that?
I typically have ask my patient to follow up. They may have other symptoms that he did not recogniz that have not resolved
I have patients with heart block, a type of Lyme carditis that resolved within days. I have more complex cases requiring ongoing work with a cardiologist. I do not have a blood test that helps determine if Lyme disease has resolved. I have to assess each of my patients