Your heart pounds for no reason. You stand up too quickly and the room spins. You're exhausted after a short walk — not just tired, but crashed, needing hours to recover. You've had an ECG, maybe a Holter monitor, maybe an echocardiogram. Everything is structurally normal. The cardiologist says it might be anxiety.
You know it isn't anxiety. And you're right to keep looking.
This page is for people experiencing cardiac or autonomic symptoms — palpitations, racing pulse, dizziness, extreme fatigue — that haven't been explained by standard testing. We'll look at why these symptoms happen, why standard tests often miss the cause, and why tick-borne infections are a possibility worth knowing about.
A familiar and frustrating sequence
The problem isn't the cardiologist. Cardiac tests are designed to detect structural disease — and they're excellent at it. But when an infection is dysregulating the autonomic nervous system, there's nothing structural to find. The scan is clean. The symptoms are not.
Structural vs. regulatory — two completely different problems
Standard cardiac testing is designed to find structural problems: damaged muscle, blocked arteries, valve disease, abnormal electrical rhythm. These tests are excellent at what they do. But there's a whole category of symptoms they're not designed to detect.
The autonomic nervous system (ANS) runs continuously in the background, managing everything you don't consciously control: heart rate, blood pressure, digestion, temperature, sweat, breathing rate. When it's working well, you don't notice it. When it's dysregulated — as it can be in tick-borne illness — your body struggles to maintain stability, especially during upright activity, exertion, or stress.
Autonomic dysregulation looks a lot like anxiety from the outside. Racing heart, difficulty breathing, trembling, exhaustion. But the mechanism is completely different. Anxiety is driven by psychological stress response. Autonomic dysregulation from infection is driven by direct disruption of the nervous system. Treating one does nothing for the other — and being told "it's anxiety" when it isn't is one of the most demoralising experiences in this illness.
Does your heart race or your symptoms worsen when you stand up, change position, or exert yourself even mildly — in a way that feels automatic, not emotional? Do you crash after minimal activity, needing hours or days to recover? Does your body struggle to regulate itself in ways that don't respond to rest alone? These patterns point toward the autonomic system, not the heart's structure.
What this cluster looks and feels like
- Heart palpitations — fluttering, pounding, or skipped beats at rest or with minimal activity
- Sudden racing pulse with no physical trigger — sitting still, lying down, just existing
- Lightheadedness or near-fainting when standing, especially quickly (orthostatic intolerance)
- Profound, crushing fatigue that doesn't improve with sleep or rest
- Crashing after light activity — walking to the kitchen, a short conversation, a shower
- Temperature dysregulation — persistently cold extremities, or unexpected sweating
- Shortness of breath or air hunger without lung or structural heart disease
- Blood pressure that fluctuates — episodes of feeling very low or very unstable
- Brain fog alongside all of the above — cognitive and cardiac symptoms travelling together
- Waking in the night with a pounding heart or sudden feeling of dread
Research into post-treatment Lyme disease documented significant autonomic nervous system dysfunction in patients — including heart rate variability abnormalities and post-exertional symptom worsening. These patterns persisted independently of standard cardiac structural findings, supporting dysautonomia as a distinct and measurable feature of tick-borne illness.
How tick-borne pathogens affect the heart and autonomic system
This is rarely the first question a cardiologist asks. But tick-borne infections have a well-documented ability to disrupt the autonomic nervous system and, in some cases, directly affect the heart's conduction system.
- Can invade cardiac conduction tissue (Lyme carditis)
- Produces dysautonomia and POTS-like symptoms
- Causes post-exertional crashes driven by nervous system disruption
- Well-documented in peer-reviewed cardiac literature
- Invades the lining of blood vessels throughout the body
- Causes palpitations and vascular inflammation
- Produces neurological symptoms that mimic cardiac anxiety
- Almost never tested for in standard cardiology workups
- Parasitic infection of red blood cells — like a mild malaria
- Causes air hunger, night sweats, and profound fatigue
- Often mistaken for cardiac or respiratory conditions
- Does not respond to antibiotics used for Borrelia
- Bacterial infections affecting white blood cells
- Can cause acute flu-like collapse with fatigue
- Respond to doxycycline, but rarely tested for
- May contribute to chronic dysregulation if missed acutely
In some cases, Borrelia invades the heart's conduction system, causing varying degrees of heart block — a slowing of electrical signals between the upper and lower chambers. This can produce palpitations, fainting, and in severe cases, complete heart block requiring temporary pacing. It is a recognised, documented complication of Lyme disease. It responds to antibiotic treatment when identified.
The standard two-tier blood test detects antibodies to Borrelia — but in chronic or long-standing infection, antibody levels can fall below the detection threshold. A negative result means antibodies weren't found at the required level on that test — not that infection is absent. Co-infections like Bartonella and Babesia aren't included in standard Lyme panels at all and require their own separate testing.
The palpitations were among the scariest things I experienced. Your heart is involved — everything feels urgent. I went through cardiac testing, wore a Holter monitor, and heard "everything is fine" more times than I can count. It wasn't fine. It took finding a doctor who understood dysautonomia as a feature of tick-borne illness — not a separate condition — before anything actually changed. That framing was everything.
The labels people often receive first
Because autonomic and cardiac symptoms overlap with anxiety and other functional conditions, people with tick-borne illness often spend years in the wrong diagnostic category.
- Anxiety or panic disorder — the most common misattribution; the symptoms look similar, the mechanism is entirely different
- POTS — postural orthostatic tachycardia syndrome; sometimes correct as a description, but the underlying infectious cause is rarely investigated
- ME/CFS — significant overlap; tick-borne infection is a recognised trigger and should be ruled out
- "Functional" symptoms — often a destination rather than an answer, when no structural cause is found
- Dysautonomia of unknown cause — the autonomic involvement is recognised, but the infectious driver is not investigated
Receiving one of these diagnoses doesn't mean the search is over. It means the cause hasn't been identified yet.
What you can do with this
Write down when symptoms occur, what triggers them (position change, exertion, eating, time of day), how long they last, and what accompanies them. Note especially whether symptoms worsen 12–48 hours after activity — this post-exertional crash pattern is clinically important and worth documenting with precision.
Bring it up directly: "Could a tick-borne infection like Lyme or a co-infection be behind these symptoms? I'd like to be tested — including for Bartonella and Babesia, not just standard Lyme." Standard Lyme testing alone is not sufficient. Co-infections require their own panels. How this request is received tells you something important about whether you're in the right hands.
A doctor familiar with tick-borne illness understands that normal cardiac tests don't rule out infectious autonomic dysfunction. They evaluate symptoms clinically, not just by test result. ILADS (ilads.org) publishes practitioner guidance and a directory. That's a reasonable starting point for finding someone who asks the questions that haven't been asked yet.
A grounded perspective
- Cardiac and autonomic symptoms with normal structural tests are real — and have real, identifiable causes.
- Tick-borne infections are among those causes, and they are rarely considered in standard cardiology workups.
- A negative standard Lyme test does not close the door. Co-infections aren't even included in that test.
- You are not anxious. You are not imagining it. You are dealing with something that requires a more complete investigation.
Normal tests don't mean nothing is wrong. They mean nothing structural is wrong. Understanding that difference is the first genuinely useful piece of information many people in this situation receive.
Where to go from here
Autonomic symptoms rarely travel alone. Fatigue, brain fog, joint pain, and sleep disruption often come alongside them. The full symptom overview helps you — and any clinician — see the whole pattern at once.
Bartonella and Babesia have distinct autonomic and cardiac effects — and require different testing than standard Lyme panels. Understanding what each pathogen does is part of building the right picture.
The fatigue that comes with autonomic dysfunction is unlike ordinary tiredness. Understanding why it happens — and why pushing through it often makes things worse — changes how you approach recovery.
Healing mentality checkpoint
Heart symptoms generate a particular kind of fear — because the heart feels urgent in a way other symptoms don't. Being told everything is fine when you know it isn't is one of the most frustrating experiences in this illness. Understanding the difference between "structurally normal" and "functionally normal" is the first step toward asking better questions — and finding better answers.
Read about healing mentality →Sources & further reading
- Wormser G.P. et al. — Lyme carditis (Heart Rhythm, 2015)
- Younger D.S. — Lyme neuroborreliosis and the peripheral nervous system (J Peripher Nerv Syst, 2019)
- Aucott J.N. et al. — Post-treatment Lyme disease syndrome and dysautonomia (2013)
- ILADS clinical guidelines — ilads.org
- Columbia University Lyme and Tick-borne Disease Research Center
Last updated: March 2026