Can Lyme Disease Cause Atrial Fibrillation?

Atrial fibrillation is an uncommon presentation of Lyme carditis
Published cases describe AFib occurring before or alongside heart block
Recognizing the combination may help identify an otherwise missed cardiac infection

Can Lyme disease cause atrial fibrillation? Atrial fibrillation (AFib) is not the typical electrical abnormality associated with Lyme carditis, but published case reports show that it can occasionally occur.

Most patients with Lyme carditis develop some degree of atrioventricular (AV) block. AFib is much less common. However, two particularly instructive cases show that atrial fibrillation may either appear before heart block develops or occur at the same time as complete heart block.^1-3

This matters because a patient presenting with new-onset atrial fibrillation may initially appear to have a common cardiac arrhythmia rather than an infectious illness. The possibility of Lyme disease becomes more important when there is compatible tick exposure, fever or other systemic symptoms, unexplained bradycardia, or evolving conduction abnormalities.

A young man first presented with atrial fibrillation

A 2019 BMJ Case Reports article described a 23-year-old man who presented with sudden palpitations. His electrocardiogram (ECG) demonstrated atrial fibrillation, while echocardiography showed a mildly dilated left atrium.²

The patient did not recall a tick bite or erythema migrans rash. Because atrial fibrillation rather than AV block was the initial rhythm abnormality, Lyme carditis was considered but was not initially viewed as the leading diagnosis.

He was treated with metoprolol, and his rhythm spontaneously returned to normal sinus rhythm before discharge.

Four days later he returned with heart block

Four days after discharge, the patient returned to the hospital. Repeat ECG demonstrated Mobitz type II AV block alternating with intermittent complete heart block, findings much more characteristic of Lyme carditis.²

Clinicians obtained Lyme serologic testing and began intravenous ceftriaxone while awaiting laboratory confirmation. His symptoms began improving within 48 hours, and Lyme testing subsequently returned positive.²

After antibiotic treatment, his cardiac rhythm had returned to normal at one-month follow-up.²

A 2024 case showed AFib and complete heart block together

A second report published in 2024 provides an important variation on this presentation. Barkhordarian and colleagues described a 70-year-old man who developed two weeks of fever followed by lightheadedness and marked bradycardia.³

Unlike the younger patient, his atrial fibrillation and heart block did not occur sequentially. His ECG showed atrial fibrillation with complete heart block and a junctional escape rhythm at approximately 40 beats per minute.³

The patient recalled an insect bite approximately two months earlier but reported no rash. He had no previous history of heart disease or arrhythmia. Lyme antibody screening and both IgM and IgG immunoblots were positive.³

An echocardiogram showed a preserved ejection fraction of 60% and no structural heart disease that readily explained the new arrhythmia.³

What happened after Lyme disease treatment?

The patient was treated with intravenous ceftriaxone for three weeks and was also anticoagulated for atrial fibrillation.³

During cardiology follow-up, the complete heart block resolved. The atrial fibrillation, however, initially persisted. Three months after presentation, the patient underwent electrical cardioversion and returned to sinus rhythm, which was maintained at subsequent follow-up.³

This distinction is important. Antibiotic treatment was followed by resolution of the Lyme-associated conduction abnormality, but the case does not establish that antibiotics alone reversed the atrial fibrillation. Cardioversion was ultimately required to restore sinus rhythm.

Why these two cases matter

Together, the 2019 and 2024 reports demonstrate two different ways atrial fibrillation may appear in Lyme carditis.

• In the 2019 case, AFib appeared first and was followed several days later by high-degree AV block.
• In the 2024 case, AFib and complete heart block were present simultaneously.

These cases reinforce that atrial fibrillation should not be viewed as a typical manifestation of Lyme disease. AV block remains the hallmark electrical abnormality of Lyme carditis, and only a small number of AFib cases have been described in the literature.^1-5

At the same time, an uncommon presentation should not be mistaken for an impossible one. When new-onset AFib is accompanied by unexplained bradycardia, AV block, fever, possible tick exposure, or other findings compatible with Lyme disease, the broader clinical picture deserves consideration.

A rash or known tick bite may be absent

Neither case depended on the presence of a classic erythema migrans rash. The 23-year-old did not recall either a tick bite or rash, while the 70-year-old remembered an earlier insect bite but denied any skin manifestation.^2,3

This is clinically relevant because waiting for a recalled tick bite or characteristic rash can lower suspicion for Lyme disease when a patient instead presents with cardiac symptoms.

The absence of these findings does not establish Lyme disease, but neither should it automatically exclude Lyme carditis when the rest of the presentation is compatible.

What heart rhythm problem is most typical of Lyme carditis?

AV conduction abnormalities remain much more characteristic of Lyme carditis than atrial fibrillation. These may range from first-degree AV block to second-degree or complete heart block and can fluctuate rapidly.^1,4,5

Reviews also describe less common cardiac manifestations including bundle branch block, atrial and ventricular arrhythmias, myocarditis, pericarditis, and other electrical abnormalities.^1,4-6

Because severe conduction disease can progress quickly, patients with suspected Lyme carditis and significant ECG abnormalities may require hospital monitoring and, in selected cases, temporary pacing.

Can Lyme-related heart abnormalities be reversible?

One of the important features of Lyme carditis is that many conduction abnormalities improve after appropriate antibiotic treatment.^1,4-6

The two AFib cases illustrate this potential reversibility while also showing that recovery is not necessarily identical for every electrical abnormality. The younger patient’s AFib and subsequent heart block resolved after treatment, whereas the older patient’s heart block resolved but his atrial fibrillation persisted until cardioversion.^2,3

These reports cannot determine how frequently AFib is directly attributable to Lyme disease or predict whether atrial fibrillation will resolve with antimicrobial therapy in another patient. Case reports identify possible clinical presentations; they do not establish incidence or treatment outcomes for all patients.

Frequently Asked Questions

Can Lyme disease cause atrial fibrillation?

Atrial fibrillation has been reported in patients with Lyme carditis, but it is uncommon. Published case reports describe AFib occurring before or alongside more typical conduction abnormalities such as AV block. AV block remains the most characteristic electrical abnormality associated with Lyme carditis.

Can Lyme carditis cause atrial fibrillation and complete heart block at the same time?

Yes, although this appears to be rare. A 2024 case report described a patient with atrial fibrillation, complete heart block, and a junctional escape rhythm occurring simultaneously in the setting of Lyme carditis.

Can Lyme carditis occur without a rash?

Yes. Patients with Lyme carditis may not recall an erythema migrans rash or even a tick bite. The absence of these findings does not by itself rule out Lyme disease when the clinical presentation and exposure history otherwise raise suspicion.

Does Lyme carditis show up on an ECG?

Lyme carditis may produce ECG abnormalities including a prolonged PR interval, varying degrees of AV block, atrial fibrillation, bundle branch block, and other rhythm disturbances. Because conduction abnormalities can change rapidly, repeated ECGs or continuous cardiac monitoring may be appropriate in patients with significant suspected cardiac involvement.

Can antibiotics reverse heart rhythm abnormalities associated with Lyme carditis?

Many AV conduction abnormalities associated with Lyme carditis improve after appropriate antibiotic treatment. Atrial fibrillation may behave differently. In one 2024 case, the heart block resolved after ceftriaxone but the AFib persisted until the patient later underwent cardioversion.

Clinical Takeaway

Atrial fibrillation is not the typical presentation of Lyme carditis, but published case reports show that it may occasionally occur before or alongside the more characteristic finding of AV block.

The 2019 case demonstrated AFib followed several days later by Mobitz type II and intermittent complete heart block. The 2024 case demonstrated AFib and complete heart block simultaneously in a patient who had fever and a previous insect bite but no rash.

These reports do not mean that unexplained AFib should routinely be attributed to Lyme disease. They do show why Lyme carditis may deserve consideration when a new arrhythmia occurs in the appropriate epidemiologic and clinical setting, particularly when bradycardia or additional conduction abnormalities are present.

This article is for educational purposes and does not replace individualized medical evaluation. New chest pain, fainting, significant shortness of breath, or a markedly abnormal heart rate warrants prompt medical assessment.

Atrial fibrillation is rare in Lyme carditis, but AFib occurring with evolving or complete heart block can be an important clue to an atypical cardiac presentation of Lyme disease.

Related Articles

Learn more about cardiac manifestations, conduction abnormalities, and the evaluation of Lyme carditis:

5 Things to Know About Lyme Carditis
When Lyme Disease Mimics a Heart Attack
Exercise-Induced Heart Block in Lyme Carditis: A Rare Case

References

1. Kostić T, Momčilović S, Perišić ZD, et al. Manifestations of Lyme carditis. Int J Cardiol. 2017;232:24-32.
2. Shabbir MA, Saad Shaukat MH, Arshad MH, Sacco J. Lyme carditis presenting as atrial fibrillation in a healthy young male. BMJ Case Rep. 2019;12(6):e229261.
3. Barkhordarian M, Grijalva M, Kolla A, Stein A, Nemirovsky D. Harbinger of Lyme Carditis: From Atrioventricular Block to Atrial Fibrillation. J Community Hosp Intern Med Perspect. 2024;14(4):71-74.
4. Robinson ML, Kobayashi T, Higgins Y, Calkins H, Melia MT. Lyme carditis. Infect Dis Clin North Am. 2015;29(2):255-268.
5. Wu M, Mirkin S, McPhail MN, et al. A comprehensive review of Lyme disease: A focus on cardiovascular manifestations. Cureus. 2024;16(5):e60821.
6. Badheeb M, Ahmed A, Stolear A, et al. Long-term cardiac sequelae in Lyme carditis: A review. Curr Cardiol Rev. 2026;22(4):e1573403X395575.

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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