Lyme heart symptoms

What Lyme carditis involves

Published research

Lyme carditis occurs when Borrelia burgdorferi invades heart tissue, triggering inflammation that can disrupt normal cardiac function. The most clinically significant manifestation is disruption of the heart's electrical conduction system:

Atrioventricular (AV) block. This is the hallmark of Lyme carditis. The inflammation interferes with electrical signals passing from the atria (upper chambers) to the ventricles (lower chambers) of the heart. AV block ranges in severity:

• First-degree AV block — a slowing of conduction that is usually asymptomatic and detected only on an electrocardiogram (ECG)
• Second-degree AV block — some electrical signals fail to reach the ventricles, producing a noticeable irregularity in heartbeat
• Third-degree (complete) AV block — no electrical signals pass from atria to ventricles. This is a medical emergency that may require temporary cardiac pacing. It has been associated with rare cases of sudden cardiac death in Lyme disease.

A distinctive feature of Lyme carditis is that AV block severity can fluctuate rapidly — progressing from first-degree to third-degree within hours or days. This unpredictability is one reason why cardiac monitoring is important when Lyme carditis is suspected.

Cardiac symptoms in Lyme disease

Patients with Lyme cardiac involvement may experience any combination of the following:

• Palpitations — a sensation of the heart racing, pounding, fluttering, or skipping beats. This is the most commonly reported cardiac symptom in Lyme patients.
• Chest pain or discomfort — which may feel like pressure, tightness, or a dull ache. This can reflect myocarditis (inflammation of the heart muscle) or pericarditis (inflammation of the heart lining).
• Lightheadedness or syncope — fainting or near-fainting, particularly upon standing or exertion, which may indicate significant conduction disturbance or reduced cardiac output
• Shortness of breath — especially with exertion that was previously well-tolerated, suggesting reduced cardiac efficiency
• Exercise intolerance — a disproportionate increase in heart rate or symptoms with modest physical activity
• Fatigue — while fatigue is common in Lyme disease for many reasons, cardiac involvement can add a cardiovascular component to the exhaustion

How Lyme disease affects the heart

The mechanism of Lyme carditis involves direct invasion and immune-mediated damage:

Direct tissue invasion. Borrelia spirochetes have been identified in cardiac tissue on biopsy and autopsy specimens. The bacteria appear to have an affinity for the interventricular septum — the wall between the heart's lower chambers — which is where the critical conduction pathways are located. This explains the characteristic AV block pattern.

Inflammatory infiltration. The immune response to bacteria in cardiac tissue produces lymphocytic infiltration — immune cells migrating into the heart tissue and causing localized inflammation. This inflammation disrupts the normal electrical conduction of the heart.

Myocarditis. In some cases, the inflammatory process extends beyond the conduction system to affect the heart muscle itself, reducing the heart's pumping efficiency. Myocarditis can produce chest pain, shortness of breath, and fatigue.

Pericarditis. Inflammation of the pericardium — the protective sac surrounding the heart — can occur, producing sharp chest pain that changes with body position and may worsen when lying down.

Cardiac symptoms in chronic Lyme disease

Clinical experience

While acute Lyme carditis with high-grade AV block is a well-defined clinical entity, many chronic Lyme patients report subtler cardiac symptoms that may not appear on standard cardiac testing:

• Intermittent palpitations that come and go without a clear trigger
• Postural tachycardia — an abnormal increase in heart rate when moving from lying to standing, which may reflect autonomic nervous system dysfunction
• Chest tightness or discomfort that does not fit typical cardiac patterns and is not explained by standard cardiology evaluation
• Exercise intolerance that is disproportionate to the patient's level of deconditioning

These symptoms may reflect low-grade ongoing inflammation, autonomic neuropathy, or persistent immune activation affecting cardiac function. They deserve evaluation in the context of the patient's full clinical picture.

Treatment approaches for Lyme cardiac involvement

Treatment for Lyme carditis requires addressing both the immediate cardiac risk and the underlying infection:

Acute Lyme carditis. Patients with significant conduction abnormalities typically require hospitalization for cardiac monitoring. Intravenous antibiotics are the standard of care for acute Lyme carditis, as they achieve rapid therapeutic levels. Temporary cardiac pacing may be needed for high-grade AV block until the conduction system recovers. The good news is that Lyme carditis is generally reversible — most patients see complete resolution of conduction abnormalities within 1-6 weeks of antibiotic treatment.

Whole-body hyperthermia. For chronic Lyme patients with ongoing cardiac symptoms (palpitations, exercise intolerance, autonomic dysfunction) that have not resolved with antibiotic treatment, hyperthermia-based protocols may help by addressing persistent infection and reducing the inflammatory burden. Cardiac function is monitored carefully throughout the treatment process.

Supportive cardiac care. This may include anti-inflammatory support, electrolyte optimization, and careful exercise guidance as cardiac symptoms improve.

Autonomic rehabilitation. For patients with post-infectious autonomic dysfunction affecting heart rate regulation, graduated reconditioning and specific autonomic training may help restore normal cardiovascular reflexes.

Related symptoms

Cardiac symptoms in Lyme disease often co-occur with other system involvement: