by Wendy Adams, Research Grant Director and Advisory Board Member, Bay Area Lyme Foundation


Recently, we’ve started to hear more about Lyme carditis as one potentially lethal manifestation of Lyme disease.  What exactly is it, why does it happen, and how does it cause disease?

What is Lyme Carditis?

First of all, a little Latin.  When you see the suffix “-itis”, it denotes inflammation – often caused by an infection.  So, carditis literally means inflammation of the heart.

When a Borrelia infection enters the body, we know from animal studies that it disseminates quickly.  It tries to find the tissues where it is most comfortable, and often that includes the heart.  Borrelia can infect all parts of the heart – the myocardium, the pericardium, and the endocardium, the cardiac muscle, the valves, and even the aorta itself.  The immune system senses the presence of the spirochete bacteria and induces inflammation, the first prong of the immune system’s response.

The inflammation instigated by the infection can cause an impairment of the electrical signal conduction between the atria and the ventricles.  This rhythm disruption is called atrial-ventrical (AV) block. AV block is very serious and probably the most common type of Lyme carditis.

AV Block

Image courtesy of the Children’s Heart Specialists

When the electrical signal conduction is impaired, the rhythm and mechanical beating of the heart (think the “lub-dub” rhythm) gets out of sync.  Without correct syncing of these contractions, the blood might not be in the correct chamber to get pumped out to the rest of the body at the right time, starving the body of blood and oxygen.

There are three degrees of AV block, with third-degree being the most serious.  In a third-degree block, the heart stops pumping blood reliably to the body and sudden cardiac death may occur.  A permanent pacemaker is inserted inside the body to get the heart to pump blood reliably.  Permanent pacemakers require servicing several times over the course of a patient’s lifetime, each time involving an invasive surgery.

When AV block is caused by Lyme disease, however, it can usually be reversed by administering antibiotics – without inserting a permanent pacemaker.  A temporary pacemaker can be used to support electrical conduction function until the antibiotics begin to fight the infection and inflammation subsides.   Being able to treat the AV block with antibiotics, as opposed to a permanent pacemaker, greatly decreases costs and improves the quality of the rest of the patient’s life.


The symptoms of AV block include dizziness, shortness of breath, syncope (fainting), palpitations and chest pain, similar to a heart attack.  Hopefully, the patient gets to the ER quickly, where the ER doctor would perform a cardiac workup and see an aberrant heart rhythm.

Sadly, in case studies of Lyme carditis, sometimes these patients are sent home with diagnoses of flu, meningitis, and mononucleosis, even with a history of a tick/insect bite and rashes.

Who’s At Risk?

Only 4-10% of patients with Lyme disease develop Lyme carditis, and only 1% develop AV block.  However, as with other Lyme statistics, the reporting of Lyme carditis is usually based on a positive two-tiered test – since this test is very insensitive early on, these incidence statistics may be grossly underestimated.  Lyme carditis patients also seem to be less likely to have a rash (40% of total), although that statistic is based on a small number of cases.

Importantly,  Lyme carditis seems to strike mostly young male patients up to 40 years old and as young as 14 – a population who wouldn’t usually be suffering from heart disease.

Eight fatal cases of Lyme carditis have been documented in medical journals, some of which could have been prevented by correct initial diagnosis of Lyme disease and prompt administration of antibiotics.

It’s time for the CDC and the IDSA to communicate that Lyme is not a benign disease where delayed diagnosis has no consequences.  Delayed diagnosis of Lyme is not only problematic, it can be fatal.  




Fuster, LS et al., “Electrocardiographic progression of acute Lyme disease.”  2017 Jul;35(7):1040.e5-1040.e6. doi: 10.1016/j.ajem.2017.02.052. Epub 2017 Mar 1.

Michalski, B, et. al, “Lyme Carditis Buried Beneath ST-Segment Elevations,”  2017;2017:9157625. doi: 10.1155/2017/9157625. Epub 2017 Jun 21..

Muehlenbachs, A., et al., “Cardiac Tropism of Borrelia burgdorferi: An Autopsy Study of Sudden Cardiac Death Associated with Lyme Carditis.”  2016 May;186(5):1195-205. doi: 10.1016/j.ajpath.2015.12.027. Epub 2016 Ma.,

Wendy A.

Wendy Adams. As a member of the science committee and Advisory Board, Wendy Adams provides strategic research advice and identifies, vets, and manages our research opportunities, including the Lyme Disease Biobank. Her unique perspective and knowledge as a former Lyme patient—as well as her background in finance, strategy and business development for companies like Cowen, Genentech and Aviron—make her skill set uniquely valuable to BAL. Wendy has spent over 20 years in the biotechnology field and most recently served as Chief Business Officer at Full Spectrum Genetics, Inc., an antibody engineering company pursuing programs in immuno-oncology and autoimmune disease.

7 Comments on “Getting to the Heart of the Issue – Lyme Carditis: Why Early Diagnosis is Critical

  1. Would a simple EKG pick this up? I have severe chest pains for several years but my EKG is always fine. I have also had a cardiac ultrasound come back normal.

  2. I have had Lyme disease for over ten years. I am 40 year old woman who is disabled so how can I get more help with fighting this? Would love to be able to find out more on this disease. Thank You

    1. Michele, One place to start might be connecting with a local Lyme disease support group. offers a national directory of support groups in all 50 states. And the International Lyme and Associated Diseases Society (ILADS) offers a similar referral service for physicians and care providers familiar with the disease (both in the US and in many other countries). Unfortunately with this illness, there is an awful lot of self-advocacy required to get the care and attention needed. There is still shockingly little awareness and understanding. Best wishes.

  3. I had 3rd degree heart block last Dec. and had to have a pacemaker put in. The cause according to the cardiologist?? I did not fit the criteria. I tested for Lyme in hospital, it came back negative. I’ve been symptomatic for Lyme for years but test always came back negative. After my heart issue, I decided to get my own testing and went to Lyme Literate DR. It came back positive for Lyme antibodies along with other co-infections. My cardiologists still refuse to acknowledge my Lyme and tell me my heart is fine with Pacemaker, but I’m not so sure.. Is there any way to test for certain that my heart is damaged by Lyme carditis ?

    1. Unfortunately there really is no non-invasive test for Lyme carditis, however the standard treatment when diagnosed quickly is antibiotics and a temporary pacemaker. We would encourage you to continue to discuss your history and symptoms with your doctors and wish you the best of health.

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