Lyme disease is a bacterial infection with various symptoms depending on the stage. When people contract Lyme disease after being bitten by an infected tick, they enter Stage 1. In this stage, flu-like symptoms and a bulls-eye rash surrounding the tick bite develop.
After one to four weeks of an untreated Lyme infection, the body progresses into Stage 2, which is early disseminated disease. At this point, the bacteria that causes Lyme disease has begun to spread to other areas of the body.
The bacteria is a good traveler and can make its way to organs, joints, muscles, and tissues. One vital organ that Lyme bacteria can infect is the heart. When that happens, a condition known as Lyme carditis develops. But what is Lyme carditis, and what can happen to a person if they develop it? Read on to learn about the various complications of Lyme carditis.
What is Lyme carditis?
In healthy hearts, electrical signals travel through conduction pathways, causing the ventricles – chambers that pump blood from the heart into the body – to contract. If those signals are disrupted, the heart’s ability to pump blood becomes compromised.
In people with Lyme disease, bacteria can enter the heart muscle and remain there, disrupting its function. It does this by interfering with the movement of electrical signals that go through the upper and lower chambers of the heart. The heart does not beat properly, leading to what doctors commonly call a heart block.
Lyme carditis varies in severity and is unpredictable. While it can be mild for one moment, the changes in the electrical signals can rapidly become severe.
Another reason the heart becomes damaged when Lyme bacteria enters the tissue is an immune response. The immune system recognizes a threat in the heart and triggers an inflammatory response. This inflammation and change in the electrical signals can further damage the heart and its ability to function.

When does Lyme carditis occur?
As mentioned above, Lyme carditis develops in Stage 2 of the disease. At this point, the bacteria has had plenty of time to make its way through the body to the heart and other organs. From the initial onset of infection, it can take anywhere between one and four months to progress into Stage 2.
While Lyme carditis typically begins in Stage 2, it can also happen in Stage 3. The heart symptoms that develop because of Lyme carditis can often reappear if a person does not get treated for the infection and it progresses to this third and final stage.
How does Lyme carditis affect the heart?
When Lyme carditis develops, it can cause a range of different heart symptoms. Because of high levels of inflammation of the heart tissue and a change in the heart’s ability to pump blood, additional issues can occur. Unfortunately, diagnosing Lyme carditis isn’t easy, because the complications and signs are non-specific and may appear to be caused by other conditions.
The most common complication associated with Lyme carditis is a heart block. This leads to various symptoms, including:
- Tiredness or fatigue
- Feeling dizzy or fainting
- A slowed heart rate
- Skipping heartbeats
- Difficulty breathing
- Chest pain that can range in severity
- Feeling sick to the stomach
There are varying types of heart blocks. They include:
- First degree: Marked by a slowed heartbeat and a delay in electrical signals.
- Second degree: Marked by dropped heartbeats and the inability of some electrical signals to get through. Symptoms often include slow and irregular heartbeats.
- Third degree: Marked by a complete block of electrical signals. Other parts of the heart must pick up the slack, and the heart will beat exceptionally slowly.

Lyme disease can lead to any type of heart block, and research shows that 90% of people with Lyme carditis develop a heart block. Of that 90%, close to 70% will have either a second- or third-degree block. These blocks can also occur in rapid time, going from first to second to third degree in a matter of minutes, hours, or days.
Other complications of Lyme carditis that affect the rhythm of the heart include:
- Sinus bradycardia
- Sinus node disease
- Intra-atrial block
- Atrial fibrillation
- Supraventricular tachycardia
- Bundle branch block
- Ventricular tachycardia
- Ventricular fibrillation
- Asystole
Various types of inflammation disorders can also develop in people with Lyme carditis, such as:
- Myopericarditis
- Myocarditis
- Pericarditis
- Endocarditis
- Pancarditis
While these conditions are dangerous, they are treatable. That said, in extremely rare cases, the complications caused by Lyme carditis can be fatal.
Lyme carditis is a severe complication of Lyme disease. To avoid it, the best thing you can do to is practice Lyme-preventing techniques or seek treatment immediately if Lyme disease is contracted.
Featured image by jesse orrico on Unsplash