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# Postural orthostatic tachycardia syndrome (POTS) and inappropriate sinus tachycardia

The heart races when the person stands (POTS) or even at rest (inappropriate sinus tachycardia), without a heart disease to explain it.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Sinoatrial (SA) node](https://durgical.com/en/anatomy/sinuatrial-node/)
- [Sympathetic trunk](https://durgical.com/en/anatomy/sympathetic-trunk/)
- [Right atrium](https://durgical.com/en/anatomy/right-atrium/)
- [Superior vena cava](https://durgical.com/en/anatomy/superior-vena-cava/)
- [Vagus nerve](https://durgical.com/en/anatomy/vagus-nerve/)
- [Atrioventricular (AV) node](https://durgical.com/en/anatomy/atrioventricular-node/)

## Why it happens

- [The response to standing up](https://durgical.com/en/physiology/the-response-to-standing-up/)
- [The baroreceptor reflex](https://durgical.com/en/physiology/the-baroreceptor-reflex/)
- [The autonomic nervous system: organization](https://durgical.com/en/physiology/the-autonomic-nervous-system-organization/)

## What it is

POTS is chronic orthostatic intolerance in which the sinus rate rises excessively on standing, with light-headedness and palpitations but no fall in blood pressure; inappropriate sinus tachycardia (IST) is a related autonomic disorder with a fast sinus rate at rest and on minimal effort. In both the ECG shows normal sinus rhythm: the problem is rate regulation, not structural heart disease.

## Who gets it

Both conditions mainly affect women of reproductive age (roughly 15 to 50 years; IST classically in the third and fourth decades). POTS is estimated to affect hundreds of thousands of people in the USA alone, and cases rose after the COVID-19 pandemic as part of post-COVID conditions. Data for Colombia and Latin America are scarce, and the diagnosis is probably under-recognised because symptoms are often attributed to anxiety.

## Causes

- Often no single cause is found (idiopathic); onset frequently follows a viral illness, pregnancy, surgery or trauma
- Post-infectious, including after COVID-19 (long COVID)
- Associated conditions: hypermobile Ehlers–Danlos syndrome, autoimmune disease (Sjögren syndrome, lupus, coeliac disease), myalgic encephalomyelitis/chronic fatigue syndrome
- Deconditioning after prolonged bed rest or inactivity (both a cause and a perpetuating factor)
- Rare genetic variants affecting noradrenaline reuptake (norepinephrine transporter) in a few families
- IST: enhanced intrinsic sinus node automaticity, excess sympathetic or reduced vagal tone; occasionally after catheter ablation for other arrhythmias

## Risk factors

- Female sex and age 15–50
- Recent viral infection, including COVID-19
- Joint hypermobility
- Autoimmune disease
- Family history
- Prolonged inactivity or bed rest

## Pathophysiology

On standing, about half a litre of blood shifts to the legs and splanchnic veins. Normally the baroreflex raises sympathetic tone modestly, constricts vessels and increases heart rate by only a few beats. In POTS, venous return stays low because of impaired vasoconstriction in the lower limbs (neuropathic type, from a patchy small-fibre autonomic neuropathy), low circulating blood volume (hypovolaemic type) or an exaggerated sympathetic discharge with high upright noradrenaline (hyperadrenergic type). The [sympathetic trunk](https://durgical.com/en/anatomy/sympathetic-trunk/) drives the sinoatrial node to compensate, so the heart rate rises sharply, but cerebral perfusion is still marginal, giving light-headedness and brain fog. In IST the sinus node itself is overactive, through increased intrinsic automaticity, heightened beta-adrenergic sensitivity or a sympathovagal imbalance. Deconditioning shrinks the heart and blood volume and worsens both conditions.

## Classification

- POTS subtypes (overlapping): neuropathic, hypovolaemic, hyperadrenergic
- Inappropriate sinus tachycardia: resting sinus rate above 100 beats/min with a mean 24-hour rate above 90 beats/min, not explained by a physiological cause
- Both are distinguished from orthostatic hypotension (blood pressure falls on standing) and from reflex (vasovagal) syncope

## Symptoms and signs

- Palpitations and a racing heart on standing (POTS) or at rest and with little effort (IST)
- Light-headedness, dizziness or near-fainting that eases on lying down
- Fatigue, exercise intolerance and poor sleep
- Brain fog, difficulty concentrating, headaches
- [Chest](https://durgical.com/en/anatomy/region/chest/) discomfort, breathlessness, tremor and sweating
- Nausea, bloating and other digestive symptoms; purplish discoloration of the feet on standing (acrocyanosis)

## Red flags

- Syncope during exertion or while lying down (suggests a cardiac arrhythmia or structural heart disease)
- Abrupt onset and offset of a regular tachycardia, or a rate above about 150 beats/min at rest (suggests supraventricular tachycardia rather than sinus tachycardia)
- Fall in blood pressure on standing (orthostatic hypotension, not POTS)
- Family history of sudden death, abnormal ECG or heart murmur
- Weight loss, fever, bleeding or heat intolerance (hyperthyroidism, anaemia, blood loss, infection)
- Paroxysmal headache, sweating and hypertension (pheochromocytoma)

## Diagnosis

**Clinical**
POTS: during an active stand test or tilt, a sustained heart-rate rise of at least 30 beats/min (at least 40 in people aged 12–19) within 10 minutes of standing, or a rate above 120 beats/min, without orthostatic hypotension, with symptoms for at least 3 months. IST: persistent resting sinus tachycardia above 100 beats/min, mean above 90 beats/min over 24 hours, with symptoms, once secondary causes are excluded. Both are diagnoses of exclusion.

**Tests**
12-lead ECG (sinus P waves, normal [axis](https://durgical.com/en/anatomy/axis/); excludes pre-excitation and other arrhythmias); 24-hour Holter monitoring (mean rate, circadian pattern, gradual onset typical of sinus tachycardia); full blood count, thyroid function, electrolytes, renal function; urine or plasma metanephrines if hyperadrenergic features; pregnancy test; review of drugs and stimulants. Specialist autonomic testing: head-up tilt table, sweat function testing (QSART), heart-rate response to deep breathing and Valsalva, upright plasma noradrenaline, sometimes [skin](https://durgical.com/en/anatomy/skin/) biopsy for small-fibre neuropathy.

**Imaging**
Transthoracic echocardiography to exclude structural heart disease when indicated. Imaging is otherwise directed by suspected secondary causes.

## Differential diagnosis

- Physiological sinus tachycardia from fever, dehydration, blood loss, anaemia, pain, pregnancy or stimulants
- Hyperthyroidism (Graves disease)
- Supraventricular tachycardia and focal atrial tachycardia near the sinus node (abrupt onset and offset)
- Orthostatic hypotension and reflex (vasovagal) syncope
- Panic disorder and generalised anxiety
- Pheochromocytoma
- Adrenal insufficiency and drug effects (beta-agonists, stimulants, withdrawal of beta-blockers)

## Goal of treatment

Reduce symptoms and restore daily function by expanding blood volume, improving venous return and progressively reconditioning, using drugs only as a complement; treat any secondary cause.

## Treatment

**Lifestyle**
Education and avoidance of triggers (heat, prolonged standing, large carbohydrate-rich meals, alcohol, dehydration); increased fluid and salt intake unless contraindicated; rising slowly; physical counter-manoeuvres such as leg crossing and muscle tensing; raising the head of the bed.

**Rehabilitation**
Graded exercise training, starting in recumbent or seated positions (rowing, recumbent cycling, swimming) and progressing to upright exercise; this is a cornerstone of POTS management.

**Conservative**
Waist-high compression garments or abdominal binders to reduce venous pooling.

**Medical**
POTS: drugs used off-label and often combined, chosen by subtype: volume expanders (fludrocortisone), alpha-1 agonists (midodrine), low-intensity beta-blockers (propranolol), acetylcholinesterase inhibitors (pyridostigmine), and ivabradine; central sympatholytics in hyperadrenergic forms.

**Medical**
IST: beta-blockers and ivabradine (a selective sinus-node If-channel blocker), alone or together, with exercise training. Sinus node modification by catheter ablation is reserved for refractory cases because of limited long-term benefit and risks.

**Follow-up**
Nursing: measure heart rate and blood pressure lying and after standing; prevent falls (sit or lie down with legs raised at the first warning symptoms); fluid balance; check for supine hypertension with fludrocortisone or midodrine; watch for bradycardia or hypotension with beta-blockers and ivabradine; screen for low mood and anxiety; support school or work adjustments.

## Complications

- Falls and injuries from presyncope or syncope
- Marked disability, school or work absence and progressive deconditioning
- Anxiety, depression and reduced quality of life
- Drug adverse effects: supine hypertension, hypokalaemia (fludrocortisone), bradycardia and visual disturbances (ivabradine)
- Damage to the [phrenic nerve](https://durgical.com/en/anatomy/phrenic-nerve/) or need for a pacemaker after sinus node ablation (IST)

## Prognosis

Neither condition shortens life expectancy, but both can be disabling. Many people with POTS improve over months to a few years, especially young patients and post-viral cases, although some symptoms often persist. IST tends to be chronic and fluctuating; it rarely causes tachycardia-induced cardiomyopathy.

## Prevention

- No proven primary prevention
- Avoiding prolonged bed rest and keeping physically active after illness or surgery
- Early recognition of triggers and adequate hydration to prevent flares

## Test yourself

Think of the answer, then tap the question to see it.

## What heart-rate change on standing defines POTS in an adult?

A sustained rise of at least 30 beats/min (or a rate above 120 beats/min) within 10 minutes of standing, without orthostatic hypotension, with symptoms lasting at least 3 months.

## What distinguishes POTS from orthostatic hypotension?

In POTS the heart rate rises excessively but blood pressure is maintained; in orthostatic hypotension systolic pressure falls by at least 20 mmHg (or diastolic by 10 mmHg) on standing.

## Which non-drug measure is a cornerstone of POTS treatment?

Graded exercise training starting in recumbent positions, together with fluids, salt and compression garments.

## Which drug selectively slows the sinus node and is used in inappropriate sinus tachycardia?

Ivabradine, an inhibitor of the funny (If) current of the sinoatrial node, alone or with a beta-blocker.

## Which secondary causes must be excluded before diagnosing inappropriate sinus tachycardia?

Hyperthyroidism, anaemia, fever or infection, dehydration or blood loss, pregnancy, pheochromocytoma, drugs and stimulants, and structural heart disease or another tachyarrhythmia.

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## Related conditions

- [Syncope (vasovagal, orthostatic hypotension, cardiac)](https://durgical.com/en/conditions/syncope/)
- [Supraventricular tachycardia (AVNRT, AVRT)](https://durgical.com/en/conditions/supraventricular-tachycardia/)
- [Graves disease (hyperthyroidism)](https://durgical.com/en/conditions/graves-disease/)
- [Phaeochromocytoma](https://durgical.com/en/conditions/phaeochromocytoma/)
- [Iron deficiency anaemia](https://durgical.com/en/conditions/iron-deficiency-anaemia/)
- [Ehlers–Danlos syndrome](https://durgical.com/en/conditions/ehlers-danlos-syndrome/)
- [Panic disorder](https://durgical.com/en/conditions/panic-disorder/)
- [COVID-19](https://durgical.com/en/conditions/covid-19/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Postural tachycardia syndrome (PoTS)](https://www.nhs.uk/conditions/postural-tachycardia-syndrome/) (NHS, 2026); [Postural Orthostatic Tachycardia Syndrome (POTS)](https://my.clevelandclinic.org/health/diseases/16560-postural-orthostatic-tachycardia-syndrome-pots) (Cleveland Clinic, 2026); Harrison's Principles of Internal Medicine, 21st ed. Chapter 247: Physiologic and Nonphysiologic Sinus Tachycardia (McGraw Hill, 2022).

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Source: https://durgical.com/en/conditions/postural-orthostatic-tachycardia-syndrome-and-inappropriate-sinus-tachycardia/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/postural-orthostatic-tachycardia-syndrome-and-inappropriate-sinus-tachycardia/