Etiology, pathology, genomics, physiology, and clinical course of post-SARS-CoV-2 autonomic disease
John Murphy, CEO, The COVID-19 Long haul Foundation
Abstract
Autonomic dysfunction has emerged as one of the most reproducible and clinically consequential phenotypes of post-acute sequelae of SARS-CoV-2 infection (PASC), or Long COVID. Patients may develop postural orthostatic tachycardia syndrome (POTS), orthostatic intolerance, inappropriate sinus tachycardia, orthostatic hypotension, impaired sudomotor function, gastrointestinal dysmotility, thermoregulatory abnormalities, and disturbances of cardiovascular autonomic control. These manifestations frequently coexist with fatigue, post-exertional malaise, cognitive dysfunction, headache, sleep disturbance, and small-fiber neuropathy, suggesting that autonomic disease is not an isolated cardiovascular disorder but a systemic neurovascular and neuroimmune phenotype.
The pathogenesis remains incompletely defined. Current evidence supports several potentially interacting mechanisms: impaired venous return and reduced circulating plasma volume; sympathetic overactivation; impaired peripheral vasoconstriction; small-fiber autonomic neuropathy; endothelial and microvascular dysfunction; altered baroreflex function; immune dysregulation; and, in a subset of patients, autoantibodies directed against G-protein-coupled receptors.¹–⁶ Persistent viral antigen and postinfectious immune activation remain plausible upstream triggers, although causality has not been established for any single mechanism. Importantly, recent quantitative autonomic testing has demonstrated objective abnormalities in patients with Long COVID, including abnormal heart-rate and blood-pressure responses to standing and tilt, impaired Valsalva responses, and reduced respiratory sinus arrhythmia.⁷
The physiological consequences can be substantial. On assuming the upright posture, excessive venous pooling or inadequate vasoconstriction reduces venous return and stroke volume. Compensatory sympathetic activation then produces tachycardia, while cerebral perfusion may remain inadequate. This model provides a physiological explanation for the characteristic concurrence of tachycardia, dizziness, fatigue, cognitive dysfunction, exercise intolerance, and presyncope. The syndrome is further complicated by abnormalities of blood volume, vascular resistance, autonomic small fibers, and neurovascular coupling.
The genomic architecture of post-COVID autonomic disease is presently unresolved. No autonomic-specific genome-wide association study has established a genetic locus for Long-COVID dysautonomia. However, genetic susceptibility to POTS and autonomic disorders predates the pandemic, and candidate variants affecting norepinephrine transport, endothelial nitric-oxide signaling, and G-protein signaling have been reported.⁸ A 2025 genome-wide association study of Long COVID identified a replicated association near FOXP4, but this locus was not demonstrated to be specific for autonomic disease.⁹ The emerging model is therefore one of host susceptibility interacting with an acquired postinfectious neuroimmune and vascular insult.
The clinical course is heterogeneous. Some patients improve over months, whereas others experience persistent or relapsing disease for years. Recent quantitative studies demonstrate that autonomic abnormalities may remain detectable more than three years after infection.⁷ The recognition of autonomic dysfunction as a major Long-COVID phenotype has important implications for diagnosis, trial design, and treatment. It argues for physiological phenotyping rather than reliance on symptom inventories and for mechanistically stratified clinical trials rather than treatment of Long COVID as a single homogeneous disorder.
Introduction
The autonomic nervous system is responsible for maintaining physiological stability in the face of continuous perturbation.
It regulates:
- heart rate;
- vascular tone;
- blood pressure;
- gastrointestinal motility;
- sweating;
- thermoregulation;
- pupil function;
- bladder function;
- sexual function;
- metabolic responses;
- and the redistribution of blood during exercise and orthostasis.
Its operation is therefore inseparable from virtually every major physiological system.
The emergence of autonomic dysfunction after SARS-CoV-2 infection is consequently of more than symptomatic interest.
It offers a potential mechanistic explanation for several of the most disabling manifestations of Long COVID:
tachycardia + fatigue + exercise intolerance + dizziness + cognitive dysfunction + post-exertional malaise.
The contemporary literature increasingly supports the proposition that autonomic dysfunction constitutes a major Long-COVID phenotype, although its prevalence varies substantially according to patient selection, diagnostic criteria, timing, and testing methodology. Reviews of cardiovascular autonomic dysfunction have emphasized that POTS, orthostatic hypotension, inappropriate sinus tachycardia, and related disorders can persist after COVID-19 and may impose substantial functional impairment.¹˒²
The important question is not simply whether SARS-CoV-2 causes dysautonomia.
It is:
How does an acute viral infection produce persistent failure of cardiovascular and systemic homeostasis months or years later?
The answer increasingly appears to involve an interaction among the immune system, vascular endothelium, peripheral nerves, circulating blood volume, autonomic reflexes, and possibly persistent antigenic stimulation.
1. The Autonomic Phenotype of Long COVID
Long-COVID autonomic disease encompasses several overlapping syndromes.
Postural orthostatic tachycardia syndrome
POTS is characterized by an excessive increase in heart rate after standing without the degree of sustained orthostatic hypotension required for the diagnosis.
Orthostatic intolerance
Patients experience symptoms on standing even when they do not meet formal POTS or orthostatic-hypotension criteria.
Orthostatic hypotension
Blood pressure falls excessively during upright posture.
Inappropriate sinus tachycardia
Heart rate remains inappropriately elevated at rest or with minimal exertion.
Neurogenic or neuropathic dysautonomia
Small autonomic fibers or their regulatory pathways are impaired.
Sudomotor dysfunction
Sweating becomes excessive, inadequate, asymmetric, or poorly regulated.
Gastrointestinal autonomic dysfunction
Patients may experience:
- nausea;
- early satiety;
- constipation;
- diarrhea;
- gastroparesis-like symptoms;
- abnormal intestinal motility.
These manifestations frequently coexist.
The patient who develops POTS may therefore also have:
small-fiber neuropathy + gastrointestinal dysmotility + temperature dysregulation + fatigue + cognitive dysfunction.
This clustering is one reason autonomic dysfunction should be viewed as a systemic physiological phenotype rather than merely a cardiac abnormality.
2. Evidence That the Autonomic Phenotype Is Objective
One of the principal historical problems in Long COVID was the assumption that autonomic symptoms were largely subjective.
This assumption is increasingly untenable.
A 2025 prospective study published in The American Journal of Medicine compared Long-COVID participants with POTS patients and healthy controls using quantitative autonomic testing, including beat-to-beat cardiovascular monitoring, respiratory sinus arrhythmia, Valsalva responses, orthostatic testing, and sudomotor assessment. The investigators reported a substantial burden of autonomic dysfunction and POTS in the Long-COVID population.¹⁰
More recently, a quantitative autonomic-testing study reported greater increases in heart rate and greater blood-pressure reductions during active standing and tilt-table testing among Long-COVID participants than among controls, together with lower Valsalva ratios and respiratory sinus-arrhythmia measures. Abnormalities remained detectable in patients referred as long as 40 months after infection.⁷
These findings are important because they provide physiological evidence independent of symptom reporting.
3. The Important Negative Finding
The evidence is nevertheless more nuanced than simply stating that “Long COVID causes POTS.”
A 2025 case-control study used 30-minute tilt-table testing at 70 degrees in patients with chronic Long-COVID autonomic symptoms. Long-COVID participants had substantially greater autonomic symptom burden and a higher heart rate throughout tilt, but only 3 of 16 participants met predefined clinically abnormal hemodynamic criteria.⁶
This distinction is crucial.
It indicates that:
autonomic symptoms do not necessarily equal classical POTS.
Long-COVID autonomic dysfunction may exist along a spectrum:
normal conventional testing
→
subclinical autonomic dysregulation
→
orthostatic intolerance
→
POTS
→
orthostatic hypotension or more generalized autonomic failure.
The clinical phenotype therefore cannot be reduced to a single diagnostic category.
4. Normal Orthostatic Physiology
To understand pathological physiology, the normal response to standing must first be considered.
When a person stands:
gravity → approximately 500–800 mL of blood shifts toward the lower extremities and abdomen.
This reduces:
- venous return;
- right-atrial filling;
- ventricular preload;
- stroke volume.
The baroreceptors in the:
- carotid sinus;
- aortic arch
detect the reduction in arterial stretch.
The medulla responds by:
reducing parasympathetic activity
and
increasing sympathetic activity.
The resulting response includes:
- increased heart rate;
- increased myocardial contractility;
- peripheral vasoconstriction;
- venoconstriction.
The objective is to maintain:
cardiac output + arterial pressure + cerebral perfusion.
A simplified relationship is: Cardiac Output=Heart Rate×Stroke Volume
and Mean Arterial Pressure≈Cardiac Output×Systemic Vascular Resistance.
A defect in any component can destabilize orthostasis.
5. The Pathophysiology of POTS
Consider a patient who loses substantial effective circulating volume.
Standing produces:
reduced venous return
↓
reduced stroke volume
↓
reduced cardiac output.
The body compensates by increasing heart rate:
tachycardia
but if peripheral vasoconstriction remains inadequate, the system remains inefficient.
The result may be:
- palpitations;
- dizziness;
- visual disturbance;
- weakness;
- cognitive slowing;
- fatigue;
- presyncope.
This provides a coherent physiological explanation for why patients frequently report that:
“My brain works when I lie down but stops working when I stand.”
The symptom is potentially a manifestation of postural cerebral hypoperfusion rather than a primary cognitive disorder.
6. Hypovolemia
Reduced circulating volume is one of the most plausible mechanisms of post-COVID orthostatic intolerance.
The mechanisms may include:
- inadequate fluid intake;
- renal sodium handling abnormalities;
- altered renin–angiotensin–aldosterone physiology;
- impaired plasma-volume expansion;
- excessive venous capacitance.
The recent Communications Medicine synthesis notes that hypovolemic POTS and impaired vasoconstriction can converge on the same clinical phenotype, with reduced plasma volume producing compensatory sympathetic activation and tachycardia.³
This distinction matters therapeutically.
Two patients may both have a heart rate of 130 beats per minute on standing, but one may have:
hypovolemia
whereas another may have:
small-fiber denervation and impaired peripheral vasoconstriction.
The treatment implications are different.
7. Neuropathic POTS
A second mechanism is partial autonomic denervation.
Small sympathetic fibers innervate:
- arterioles;
- veins;
- sweat glands;
- visceral organs.
If these fibers are damaged, the lower extremities may fail to constrict appropriately during standing.
The consequence is:
excessive venous pooling
→
reduced venous return
→
tachycardia.
This form is often termed neuropathic POTS.
Recent mechanistic reviews report evidence of patchy small-fiber denervation in a subset of patients with Long COVID.³
8. Small-Fiber Neuropathy
The peripheral nervous system provides an important pathological bridge between Long COVID and dysautonomia.
Small fibers include:
- unmyelinated C fibers;
- thinly myelinated A-delta fibers.
They mediate:
- temperature;
- pain;
- sweating;
- vascular regulation;
- visceral sensation.
A 2024 case-control study found evidence of small-fiber neuropathy in a substantial subset of carefully selected patients with painful post-COVID conditions.¹¹
A separate Yale cohort identified biopsy-proven small-fiber neuropathy in patients with post-COVID disease and found neurovascular dysregulation and dysautonomia during invasive cardiopulmonary exercise testing.¹²
These observations support an integrated model:
small-fiber injury
→
impaired autonomic vascular control
→
abnormal venous pooling
→
reduced preload
→
tachycardia and exercise intolerance.
9. The Autonomic–Metabolic Connection
Dysautonomia may also explain why exercise becomes disproportionately difficult.
During exercise, the cardiovascular system must:
- increase cardiac output;
- redistribute blood to skeletal muscle;
- maintain cerebral perfusion;
- regulate temperature;
- increase ventilation.
If autonomic control is impaired, these adjustments become inefficient.
The patient may experience:
early tachycardia
inadequate stroke-volume augmentation
abnormal peripheral vascular regulation
impaired oxygen extraction
→
exercise intolerance.
This is especially important in patients with post-exertional malaise, in whom exercise may provoke delayed rather than immediate worsening.
10. Neurovascular Dysregulation
The autonomic nervous system and vascular system are inseparable.
A recent study of patients with post-COVID small-fiber neuropathy used invasive cardiopulmonary exercise testing and found evidence of neurovascular dysregulation consistent with dysautonomia and ME/CFS physiology.¹²
This suggests that some patients may have a defect not simply in heart rate control but in the integrated process by which blood flow is distributed among:
- heart;
- skeletal muscle;
- brain;
- skin;
- splanchnic circulation.
The resulting disease is therefore better described as neurovascular dysregulation.
11. Cerebral Perfusion
The brain is unusually dependent on continuous blood flow.
Autonomic dysfunction can impair cerebral perfusion through several mechanisms:
- reduced cardiac output;
- excessive venous pooling;
- impaired cerebral autoregulation;
- abnormal vascular tone;
- hypocapnia associated with altered breathing;
- endothelial dysfunction.
Thus, a patient may have normal brain structure but abnormal brain function when upright.
This may explain the characteristic combination of:
orthostatic dizziness + cognitive dysfunction + visual disturbance + headache.
12. Baroreflex Dysfunction
The baroreflex is the principal short-term regulator of blood pressure.
It operates through:
arterial pressure sensors → brainstem integration → sympathetic/parasympathetic output → heart and blood vessels.
Long COVID may disturb this system.
Quantitative autonomic testing has demonstrated abnormalities in:
- Valsalva responses;
- respiratory sinus arrhythmia;
- orthostatic heart-rate regulation;
- blood-pressure responses.
The recent JACC study found lower Valsalva ratios and respiratory sinus arrhythmia measures in Long-COVID participants compared with controls.⁷
These findings suggest that autonomic dysfunction may involve both:
cardiovagal
and
adrenergic
components.
13. Sympathetic Overactivation
Tachycardia is not necessarily the primary defect.
It may be a compensatory response.
If venous return falls, sympathetic activation increases heart rate to preserve cardiac output.
Thus:
tachycardia may be the body’s solution to an upstream circulatory problem.
This distinction is critical.
Suppressing heart rate without correcting the underlying physiology may improve palpitations while worsening:
- fatigue;
- exercise tolerance;
- orthostatic symptoms.
This is one reason phenotype-specific treatment is necessary.
14. Autoimmunity
One of the leading mechanistic hypotheses is postinfectious autoimmunity.
The hypothesis is biologically plausible because:
- POTS frequently follows infection;
- autoimmune disorders can cause autonomic neuropathy;
- adrenergic and muscarinic receptor antibodies have been detected in some POTS cohorts.
Candidate antibodies include those targeting:
- α1-adrenergic receptors;
- β1-adrenergic receptors;
- β2-adrenergic receptors;
- muscarinic receptors.
However, the evidence must be interpreted carefully.
Multiple reviews emphasize that these antibodies are not specific to Long COVID, and their presence does not prove that they cause autonomic disease.¹˒²
The correct conclusion is therefore:
autoimmunity is a plausible mechanism in a subset of patients, not an established universal cause of Long-COVID dysautonomia.
15. The G-Protein-Coupled Receptor Hypothesis
Adrenergic and muscarinic receptors belong to the G-protein-coupled receptor family.
Antibodies that alter their function could theoretically produce:
- abnormal vasoconstriction;
- inappropriate tachycardia;
- impaired autonomic regulation.
Experimental evidence supports biological activity of some receptor-directed antibodies, but clinical causality remains unresolved.
A critical unanswered question is:
Are these antibodies pathogenic, compensatory, or epiphenomenal?
Only interventional studies can definitively answer this question.
16. Endothelial Dysfunction
The endothelium regulates:
- vascular tone;
- coagulation;
- leukocyte trafficking;
- inflammation.
SARS-CoV-2 can cause endothelial injury during acute disease.
Persistent endothelial dysfunction could therefore produce:
- impaired vasodilation;
- abnormal vascular resistance;
- microvascular perfusion abnormalities;
- platelet activation.
Long-COVID reviews have identified endothelial dysfunction and cerebral blood-flow abnormalities among recurrent biological findings.⁴
The autonomic and vascular systems may therefore form a pathological feedback loop:
autonomic dysfunction
→ abnormal vascular tone
→ impaired perfusion
→ compensatory sympathetic activation
→ further autonomic stress.
17. Persistent Viral Antigen
Persistent SARS-CoV-2 antigen has been reported in some Long-COVID cohorts.
Whether this antigen is biologically active remains uncertain.
If it is capable of maintaining immune activation, a possible sequence is:
persistent antigen
↓
immune activation
↓
endothelial dysfunction
↓
autonomic nerve injury
↓
dysautonomia.
This remains a hypothesis rather than an established causal pathway.
18. Mast-Cell Signaling
Mast cells interact closely with:
- blood vessels;
- autonomic nerves;
- gastrointestinal tissues;
- immune cells.
Histamine can alter:
- vascular permeability;
- vasodilation;
- heart rate;
- gastrointestinal function.
Mast-cell-related symptoms have been reported in Long COVID, and some patients report improvement with antihistamines.⁴
However, objective diagnostic criteria for mast-cell activation syndrome are often inconsistently applied in Long-COVID studies.
The mechanism therefore remains plausible but incompletely established.
19. The Autonomic–Immune Interface
The autonomic and immune systems are not independent.
Sympathetic fibers innervate lymphoid organs.
Immune cells express:
- adrenergic receptors;
- cholinergic receptors.
Conversely, cytokines influence autonomic activity.
The relationship is therefore bidirectional:
immune activation → autonomic dysfunction
and
autonomic dysfunction → altered immune regulation.
This creates the possibility of a self-sustaining postinfectious state.
The concept is particularly attractive for Long COVID because persistent symptoms may continue after the initiating infection has disappeared.
20. Genomics: What We Know
The genetic basis of Long-COVID autonomic dysfunction remains one of the least developed areas of the field.
There is currently no validated genome-wide association study specifically defining genetic susceptibility to Long-COVID POTS or dysautonomia.
This absence is important.
It would be premature to claim that a particular gene causes post-COVID autonomic disease.
Nevertheless, POTS itself appears to have a familial component.
The NIH POTS consensus literature notes familial clustering and candidate associations involving pathways related to:
- norepinephrine transport;
- G-protein signaling;
- endothelial nitric oxide;
- immune regulation.⁸
No monogenic explanation has been established for ordinary POTS.
21. The Norepinephrine Transporter
A rare familial form of autonomic dysfunction has been linked to altered norepinephrine transporter function.
The norepinephrine transporter normally clears norepinephrine from the synaptic cleft.
Reduced transporter activity can produce:
excessive sympathetic signaling
→
tachycardia
→
orthostatic intolerance.
This illustrates how genetically determined alterations in autonomic neurotransmission can produce a phenotype resembling postviral dysautonomia.
It does not, however, demonstrate that the same mutation explains Long-COVID POTS.
22. Long-COVID Genetics
The largest Long-COVID GWAS, published in Nature Genetics in 2025, analyzed up to 6,450 Long-COVID cases and more than 1 million controls and identified a replicated association near FOXP4.⁹
The association was particularly related to lung biology, and the investigators found that a proxy variant was associated with FOXP4 expression in both lung and hypothalamic tissue.
The relevance to autonomic dysfunction is therefore potentially intriguing but remains speculative.
The hypothalamus participates in:
- autonomic regulation;
- endocrine signaling;
- thermoregulation;
- stress responses.
Nevertheless:
FOXP4 should not presently be regarded as an autonomic Long-COVID gene.
The current evidence supports it as a general Long-COVID susceptibility locus.
23. A Polygenic Model
A more plausible model is:
genetic predisposition
viral exposure
immune response
vascular susceptibility
autonomic reserve
=
post-COVID dysautonomia.
In such a model, genetic variants would alter susceptibility rather than determine outcome.
This is consistent with the broader understanding of POTS, which lacks a single Mendelian cause.⁸
24. Epigenetic Mechanisms
Genetic sequence is only one layer of biological regulation.
SARS-CoV-2 infection can potentially modify:
- DNA methylation;
- chromatin accessibility;
- transcriptional programs.
If autonomic neurons or immune cells undergo persistent epigenetic reprogramming, abnormal autonomic regulation could theoretically continue after viral clearance.
This hypothesis remains insufficiently established in humans and requires longitudinal single-cell and tissue-level investigation.
25. Peripheral Autonomic Neuropathy
The autonomic nervous system contains extensive peripheral fibers that regulate:
- blood vessels;
- heart;
- gastrointestinal tract;
- sweat glands.
Damage to these fibers could explain why patients simultaneously develop:
POTS + sweating abnormalities + bowel dysfunction + temperature dysregulation.
Skin biopsy and quantitative sudomotor axon-reflex testing may therefore provide objective evidence of peripheral autonomic dysfunction.
A 2024 post-COVID POTS cohort reported abnormal quantitative sudomotor testing in approximately 63% of those tested and neuropathic findings on skin biopsy in 40%, although the sample was small and highly selected.⁵
These findings require replication but support a peripheral-neuropathy component in at least some patients.
26. The Role of Sex
POTS in the general population has a marked female predominance.
Long-COVID autonomic cohorts similarly often contain a large proportion of women.⁷˒¹⁰
Potential explanations include:
- sex differences in immune regulation;
- hormonal effects on vascular tone;
- autoimmune susceptibility;
- autonomic physiology.
However, sex-specific biological mechanisms in Long-COVID dysautonomia have not been adequately defined.
The issue warrants dedicated genomic and endocrine studies.
27. Age and Autonomic Reserve
Autonomic resilience changes with age.
Older individuals generally have:
- reduced baroreflex sensitivity;
- altered vascular compliance;
- reduced cardiac responsiveness.
This could theoretically increase vulnerability to postinfectious autonomic dysfunction.
Conversely, younger patients may have stronger sympathetic compensation and therefore develop pronounced tachycardia without substantial hypotension.
The clinical phenotype may consequently vary with age even when the initiating pathology is similar.
28. Clinical Course
The course of Long-COVID autonomic disease is highly variable.
Early onset
Symptoms may begin during or immediately after acute infection.
Delayed onset
Some patients initially recover and develop dysautonomia weeks later.
Progressive disease
Autonomic symptoms intensify over several months.
Relapsing disease
Symptoms fluctuate according to:
- exertion;
- infection;
- sleep;
- hormonal changes;
- heat;
- dehydration.
Partial recovery
Orthostatic tachycardia may improve while fatigue or neuropathy persists.
Persistent disease
Some patients remain symptomatic for several years.
Objective autonomic abnormalities have been demonstrated in patients referred up to approximately 40 months after infection.⁷
29. Recovery Does Not Necessarily Mean Normalization
A particularly important clinical observation is that recovery may be multidimensional.
A patient may report:
less tachycardia
but continue to experience:
- fatigue;
- cognitive dysfunction;
- neuropathic symptoms;
- PEM.
Conversely:
POTS may persist
while cognitive function improves.
This suggests that Long COVID contains multiple interacting biological processes rather than a single linear disease mechanism.
30. Post-Exertional Malaise
PEM is particularly important in autonomic Long COVID.
Physical exertion imposes a large autonomic demand.
The body must:
- increase cardiac output;
- redistribute blood flow;
- regulate temperature;
- maintain cerebral perfusion;
- increase ventilation.
In a patient with dysautonomia, this coordinated response may be impaired.
The result may be:
exercise → physiological stress → delayed symptom exacerbation.
This differs fundamentally from ordinary physical deconditioning.
Consequently, rehabilitation must be individualized, especially in patients who demonstrate PEM.
31. The Autonomic–Cognitive Connection
“Brain fog” may be partly downstream of autonomic physiology.
Standing can produce:
reduced venous return
↓
reduced stroke volume
↓
reduced cerebral perfusion
↓
impaired attention and executive function.
This mechanism could explain why cognitive symptoms frequently worsen:
- after standing;
- during prolonged activity;
- in heat;
- after meals;
- during dehydration.
The brain is exquisitely sensitive to changes in perfusion.
Thus, autonomic dysfunction can produce a neurological phenotype without primary structural CNS disease.
32. The Autonomic–Gastrointestinal Connection
The gastrointestinal tract contains an extensive intrinsic nervous system and is heavily regulated by the autonomic system.
Dysautonomia may therefore cause:
- delayed gastric emptying;
- altered intestinal transit;
- nausea;
- constipation;
- diarrhea;
- abdominal discomfort.
The gut may consequently become both:
a target of autonomic dysfunction
and
a source of further autonomic signaling.
This provides another possible mechanism for multisystem Long COVID.
33. The Autonomic–Thermoregulatory Connection
Patients commonly report:
- heat intolerance;
- chills;
- excessive sweating;
- inability to regulate body temperature.
Thermoregulation requires coordination among:
- hypothalamus;
- sympathetic nervous system;
- skin blood vessels;
- sweat glands;
- endocrine systems.
Thus, thermoregulatory symptoms may provide a clinically useful indicator of broader autonomic dysfunction.
34. Clinical Assessment
The evaluation should begin with a careful history.
Important questions include:
- Does standing provoke symptoms?
- Does the heart race after standing?
- Does lying down improve symptoms?
- Does heat worsen symptoms?
- Are there episodes of near-syncope?
- Is sweating abnormal?
- Are bowel movements altered?
- Are symptoms worse after meals?
- Is there PEM?
- Are there neuropathic symptoms?
Orthostatic vital signs should be obtained when appropriate.
Formal autonomic testing may include:
- active stand;
- tilt-table testing;
- Valsalva maneuver;
- deep-breathing/respiratory sinus arrhythmia;
- quantitative sudomotor testing;
- autonomic reflex screening.
35. Differential Diagnosis
Long-COVID dysautonomia must not become a diagnosis of exclusion that obscures treatable disease.
Potential alternative or contributory diagnoses include:
- dehydration;
- anaemia;
- thyroid disease;
- adrenal disease;
- arrhythmia;
- structural heart disease;
- medication effects;
- diabetes-related autonomic neuropathy;
- peripheral neuropathy from other causes;
- Parkinsonian autonomic failure;
- autoimmune autonomic ganglionopathy;
- deconditioning.
This is particularly important because several of these disorders are treatable.
36. Treatment: A Mechanism-Based Approach
Treatment should follow phenotype.
For hypovolemic physiology:
- adequate fluid intake;
- increased sodium intake when medically appropriate;
- compression garments;
- carefully selected pharmacological volume expansion.
For excessive tachycardia:
- selected rate-control strategies may be considered.
For peripheral vasodilation or venous pooling:
- compression;
- physical counter-maneuvers;
- selected vasoconstrictor therapy.
For small-fiber neuropathy:
- neuropathic-pain treatment;
- evaluation for immune-mediated mechanisms.
For PEM:
- pacing and individualized activity management rather than indiscriminate graded exercise.
The 2025 scoping review of Long-COVID autonomic treatments found substantial heterogeneity in the evidence base and emphasized the need for better controlled trials.¹³
37. Immunotherapy
Immunotherapy is among the most intriguing experimental approaches.
The rationale is strongest in patients with:
- biopsy-confirmed small-fiber neuropathy;
- objective autonomic dysfunction;
- evidence suggesting immune-mediated disease.
A retrospective Yale study of post-COVID small-fiber neuropathy reported clinical improvement in all nine patients treated with IVIG versus three of seven untreated patients.¹²
However, this was a small, nonrandomized study.
It therefore provides:
a signal of efficacy
not
proof of efficacy.
Randomized controlled trials are required before IVIG can be considered established disease-modifying therapy for Long-COVID autonomic neuropathy.
38. Why Autoantibody Testing Is Not Yet Routine Proof of Mechanism
The presence of adrenergic or muscarinic receptor antibodies should not automatically establish autoimmune POTS.
Three problems remain:
- antibodies can occur in other autonomic disorders;
- assay methods vary;
- functional pathogenicity has not been consistently demonstrated.
The appropriate scientific position is therefore:
autoantibodies may identify a biologically meaningful subgroup, but they are not yet validated as diagnostic or treatment-selection biomarkers for Long-COVID dysautonomia.
39. A Unified Pathophysiological Model
The emerging model can be represented as:
SARS-CoV-2 infection
↓
acute immune activation
↓
endothelial injury + immune dysregulation ± persistent antigen
↓
autonomic nerve and vascular dysfunction
↓
one or more of:
- hypovolemia;
- venous pooling;
- impaired vasoconstriction;
- abnormal sympathetic activation;
- impaired baroreflex;
- small-fiber neuropathy;
- abnormal cerebral perfusion.
↓
POTS / orthostatic intolerance / inappropriate tachycardia / orthostatic hypotension
↓
cerebral hypoperfusion + exercise intolerance + fatigue + cognitive dysfunction
↓
possible PEM and chronic multisystem disease.
This model accommodates the heterogeneity observed clinically.
40. A More Sophisticated Model: Multiple Endotypes
The available evidence suggests that Long-COVID dysautonomia may contain several endotypes.
Hypovolemic endotype
Primary abnormality:
reduced effective circulating volume.
Neuropathic endotype
Primary abnormality:
small-fiber autonomic denervation.
Hyperadrenergic endotype
Primary abnormality:
excessive sympathetic activation.
Immune-mediated endotype
Primary abnormality:
postinfectious immune dysfunction or autoimmunity.
Neurovascular endotype
Primary abnormality:
abnormal systemic and cerebral vascular regulation.
Mixed endotype
Most clinically severe patients may possess elements of several categories.
This framework may ultimately prove more useful than the simple diagnostic label “POTS.”
41. Research Priorities
The next generation of studies should integrate:
genomics
immune profiling
autoantibody functional assays
skin biopsy
autonomic testing
blood-volume measurements
cerebral perfusion
endothelial function
cardiopulmonary exercise testing
metabolomics
longitudinal clinical phenotyping.
The crucial objective should be to determine whether specific biological signatures predict:
- onset;
- severity;
- persistence;
- recovery;
- therapeutic response.
42. The Most Important Unanswered Question
The fundamental question is:
Is autonomic dysfunction the primary driver of Long-COVID symptoms in some patients, or is it primarily a downstream consequence of systemic disease?
The answer may be:
both.
In one patient, autonomic injury may be the dominant pathology.
In another, dysautonomia may be secondary to:
- metabolic dysfunction;
- endothelial disease;
- immune activation;
- small-fiber neuropathy.
This distinction will ultimately determine treatment.
43. Conclusions
Autonomic dysfunction has emerged as a major and objectively measurable phenotype of Long COVID.
Its clinical manifestations include:
- POTS;
- orthostatic intolerance;
- orthostatic hypotension;
- inappropriate sinus tachycardia;
- sudomotor dysfunction;
- gastrointestinal dysmotility;
- thermoregulatory abnormalities.
The strongest current evidence supports a multifactorial pathophysiology involving:
hypovolemia
venous pooling
impaired peripheral vasoconstriction
small-fiber autonomic neuropathy
baroreflex dysfunction
sympathetic overactivation
endothelial dysfunction
neurovascular dysregulation
and, potentially in selected patients,
autoimmunity or persistent antigenic stimulation.
Objective autonomic testing has demonstrated abnormalities in cardiovascular reflexes and orthostatic responses, including findings persisting years after infection.⁷
The small-fiber hypothesis is supported by skin-biopsy studies and by physiological evidence of neurovascular dysregulation in selected patients.¹¹˒¹²
The autoimmune hypothesis remains compelling but unproven. Adrenergic and muscarinic receptor autoantibodies may define biologically interesting subgroups, but their specificity and pathogenicity remain unresolved.¹˒²
The genomic architecture is even less mature. There is no established autonomic-specific Long-COVID gene. The 2025 FOXP4 association provides evidence that host genetics influences Long-COVID susceptibility, but its relevance to dysautonomia remains uncertain.⁹
The most defensible synthesis is therefore:
Long-COVID autonomic dysfunction is a heterogeneous postinfectious disorder of cardiovascular and systemic homeostasis in which immune, vascular, peripheral-neural, and volume-regulatory abnormalities converge upon impaired autonomic control.
This model explains why a single clinical phenotype can arise through multiple biological pathways.
It also explains why patients with apparently identical symptoms may respond very differently to treatment.
The next major advance will therefore not come from identifying yet another generic marker of Long COVID.
It will come from identifying the autonomic endotype operating in each patient and matching that endotype to a mechanism-specific intervention.
Numbered References
- Fedorowski A, Fanciulli A, Raj SR, Sheldon R, Shibao C, Sutton R, et al. Cardiovascular autonomic dysfunction in post-COVID-19 syndrome: a major health-care burden. Nature Reviews Cardiology. 2024;21:379-395.
- Goldstein DS. Post-COVID dysautonomias: what we know and (mainly) what we don’t know. Nature Reviews Neurology. 2024;20:99-113.
- Current status and future perspectives on the mechanistic and pathophysiological understanding of long COVID. Communications Medicine. 2026. The review synthesizes evidence for hypovolemic, neuropathic and other POTS mechanisms in Long COVID.
- Davis HE, McCorkell L, Vogel JM, Topol EJ. Long COVID: major findings, mechanisms and recommendations. Nature Reviews Microbiology. 2023;21:133-146.
- Post-COVID postural orthostatic tachycardia syndrome (POTS): a new phenomenon. Frontiers in Neurology. 2024. In a selected post-COVID POTS cohort, autonomic testing demonstrated abnormalities in sudomotor function and skin-biopsy measures in subsets of participants.
- Durstenfeld MS, Mataraarachchi N, Peluso MJ, et al. Case-control study of autonomic symptoms in the setting of Long COVID with tilt table testing. PLOS One. 2025;20:e0335218. In this small cohort, autonomic symptoms and heart rate during tilt were increased, although most participants did not meet formal criteria for abnormal hemodynamic responses.
- Association of Autonomic Dysfunction With Long COVID: Evaluation Using Quantitative Autonomic Testing. Journal of the American College of Cardiology. 2025. Quantitative testing demonstrated abnormal orthostatic heart-rate and blood-pressure responses, reduced Valsalva ratios and respiratory sinus arrhythmia, with abnormalities observed up to 40 months after infection.
- Raj SR, Guzman JC, Harvey P, et al. Postural orthostatic tachycardia syndrome: state of the science and clinical care from a 2019 NIH Expert Consensus Meeting. The consensus review discusses familial aggregation, candidate genetic variants, and the absence of a demonstrated monogenic or GWAS-defined cause of POTS.
- Lammi V, Nakanishi T, Jones SE, et al. Genome-wide association study of long COVID. Nature Genetics. 2025. The study included up to 6,450 Long-COVID cases and 1,093,995 controls and identified a replicated association near FOXP4.
- High incidence of autonomic dysfunction and postural orthostatic tachycardia syndrome in patients with Long COVID: implications for management and health care planning. American Journal of Medicine. 2025;138:354-361.e1. The prospective study used quantitative autonomic testing including beat-to-beat hemodynamic monitoring, Valsalva testing, respiratory sinus arrhythmia, orthostatic assessment and sudomotor testing.
- Falco P, Litewczuk D, Di Stefano G, et al. Small Fibre Neuropathy and Post-COVID-19 Pain: An In-depth Study. Neurology. 2024;102(7 Suppl 1):2972. In selected patients with painful post-COVID conditions, 12 of 26 had clinical and biopsy/QST findings consistent with small-fiber neuropathy.
- Case-Control Study of Individuals With Small Fiber Neuropathy After COVID-19. Neurology: Neuroimmunology & Neuroinflammation. 2024. In a retrospective cohort, biopsy-confirmed small-fiber neuropathy was associated with neurovascular dysregulation and dysautonomia on invasive cardiopulmonary exercise testing; preliminary treatment-response observations require confirmation in randomized trials.
- Treadwell JR, Wagner J, Reston JT, et al. Treatments for Long COVID autonomic dysfunction: a scoping review. Clinical Autonomic Research. 2025;35:5-29. The review identified substantial heterogeneity and limited high-quality evidence for treatment strategies.
- Autoimmunity in Long Covid and POTS. Oxford Immunology Reviews. 2023. The review summarizes evidence for receptor-directed autoantibodies while emphasizing that their lack of specificity prevents assigning a universal causal role.