Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Differentiate PoTS from inappropriate sinus tachycardia and physiological sinus tachycardia, perform reproducible orthostatic testing, and use staged non-drug and specialist off-label treatment safely.
PoTS is an orthostatic intolerance syndrome, not simply a number. Upright palpitations, dizziness, weakness, breathlessness, tremulousness, cognitive fog and fatigue improve on lying down and accompany excessive tachycardia without the BP fall that defines classical orthostatic hypotension.
IST is a diagnosis of exclusion in which normal P-wave sinus activation occurs at an excessive resting and 24-hour rate, with exaggerated acceleration on minor activity. Physiological sinus tachycardia from infection, hypovolaemia, anaemia, thyrotoxicosis, pregnancy, pulmonary disease, pain, stimulants or withdrawal must be found and treated first.
Treatment aims at function and symptom burden, not forcing a normal pulse. Non-drug measures are foundational; medication choice depends on low BP/venous pooling, hypovolaemia or dominant tachycardia and should be initiated by a clinician experienced in autonomic or rhythm disorders.
Some PoTS phenotypes have reduced effective blood volume or excessive lower-body and splanchnic pooling. Upright venous return then falls, provoking compensatory tachycardia.
Impaired peripheral vasoconstriction or excessive sympathetic activation may contribute to abnormal adaptation to standing. Sinus acceleration may help preserve cardiac output and blood pressure, but tachycardia is not necessarily the sole cause of orthostatic symptoms.
Symptoms may emerge after infection, pregnancy, surgery or prolonged inactivity. Reduced activity and conditioning may amplify orthostatic intolerance in some people, but do not establish the cause and should not be assumed to explain every presentation.
IST is mechanistically heterogeneous; proposed contributors include exaggerated sinus-node automaticity and autonomic imbalance. The diagnosis requires symptomatic sinus tachycardia at rest or with minor activity after physiological causes have been excluded.
Gravity shifts blood towards the legs and abdominal circulation. Normal compensation requires rapid venous constriction and maintenance of cardiac preload.
In some PoTS phenotypes, low effective volume, pooling or impaired vasoconstriction causes upright preload and stroke volume to fall more than usual, without the early blood-pressure fall that defines classical orthostatic hypotension.
Compensatory baroreflex activation and, in some phenotypes, excessive sympathetic drive accelerate the sinus node. The sustained posture-linked response accompanies and may contribute to palpitations, dizziness, tremor, cognitive fog and exercise intolerance.
In IST, sinus rate is inappropriately high at rest or rises disproportionately with minor physical or emotional stress. Ambulatory monitoring may show a higher mean rate than in posture-linked PoTS, supporting but not independently establishing the diagnosis.
Symptom-related inactivity may reduce stroke volume and skeletal-muscle pump efficiency in some people. Deconditioning is neither required nor sufficient to explain PoTS, and rehabilitation should be individualised when exertion worsens symptoms.
Symptoms begin or worsen upright and improve supine, with a sustained adult HR increase at least 30 beats/min within 10 minutes and no BP fall of at least 20/10 mmHg within the first 3 minutes.
Fatigue, exercise intolerance, tremor, sweating, nausea, bowel disturbance, headache, blurred/tunnel vision, acrocyanosis and cognitive fog are common but non-specific.
Sinus tachycardia is present at rest, often above 100 beats/min, and accelerates markedly with minimal physical or emotional stress; ambulatory monitoring shows a persistently raised mean rather than only upright episodes.
Exertional syncope, family history of young sudden death, abnormal cardiac examination/ECG, sustained broad-complex rhythm or major desaturation requires urgent cardiac evaluation, not reassurance as dysautonomia.
A substantial sustained early blood-pressure fall with standing redirects the diagnosis towards orthostatic hypotension, although orthostatic syndromes can coexist. Paired heart-rate and blood-pressure measurements are therefore essential.
Dehydration, bleeding, anaemia, fever, thyrotoxicosis, hypoxia, pregnancy, pain or stimulant exposure can explain the rate. Correcting the trigger should precede a PoTS or IST label.
Abrupt onset and offset, a fixed very rapid rate or non-sinus P waves suggest a focal arrhythmia rather than gradual autonomic sinus acceleration.
Panic can cause sinus tachycardia, tremor and breathlessness, but episodes are not consistently reproduced by sustained standing. Normal testing during typical symptoms supports another or coexisting explanation; anxiety should not be inferred from tachycardia alone.
Fever, dehydration, bleeding, anaemia, thyrotoxicosis, hypoxia, pregnancy, pain, stimulant/sympathomimetic use or drug withdrawal explains the rate and prevents an IST/PoTS diagnosis until corrected.
Abrupt onset/offset, non-sinus P waves, a fixed very rapid rate or pre-excitation suggests SVT or atrial tachycardia rather than autonomic sinus acceleration.
Orthostatic symptoms commonly cause presyncope; frank syncope occurs in some people and should also prompt assessment for vasovagal or other causes. Falls may produce injury and make patients avoid standing or leaving home.
Orthostatic symptoms, fatigue and cognitive fog can restrict work, education, self-care and exercise. Day-to-day variability may make disability difficult to predict or accommodate.
In some people, reduced activity because of symptoms may lower cardiovascular conditioning and amplify later orthostatic intolerance. This is a potentially modifiable consequence, not evidence that deconditioning caused the syndrome.
The HR criterion must be sustained, symptom-linked and chronic after excluding hypovolaemia and other causes. Consumer-device peaks are useful clues, not a diagnosis.
A large early BP fall redirects assessment toward orthostatic hypotension; compensatory tachycardia from volume loss is not PoTS.
Orthostatic tachycardia varies with circadian state, meals, heat, menstrual cycle, medication and hydration; record context when results and history disagree.
Normal P-wave morphology does not make the rate appropriate. Conversely, abrupt onset or a different P-wave should trigger a search for atrial tachycardia.
High sodium can help selected hypovolaemic PoTS but can harm people with hypertension, renal disease or heart failure; document the target and contraindication check.
Progressive recumbent conditioning is evidence-supported, but a fixed push-through programme can be counterproductive when a patient has post-exertional symptom exacerbation.
Diagnosing PoTS from a single standing pulse without paired BP, symptom reproduction or exclusion of dehydration.
Calling persistent resting sinus tachycardia PoTS when the posture-independent pattern fits IST or a secondary cause.
Prescribing large fluid/salt loads without checking hypertension, renal disease, heart failure or pregnancy.
Starting several off-label medicines together so benefit and harm cannot be attributed.
Pursuing sinus-node ablation routinely for IST despite variable durability and pacemaker risk.
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An adult with chronic posture-linked dizziness rests supine for 10 minutes. Their HR then rises from 72 to 106 beats/min and remains elevated through 10 minutes standing, with typical dizziness and no fall in BP. Secondary causes have been excluded. Which diagnosis is best supported?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. ·
Unlicensed for PoTS. Check supine/sitting/standing BP, renal and liver function; avoid in hypertension, severe organic heart disease, urinary retention, acute/severe renal disease and pregnancy. Stop if supine hypertension persists.
Monitor supine/standing BP, weight, oedema, sodium and potassium and review salt intake; avoid uncontrolled hypertension/heart failure and use the lowest effective dose. Do not stop prolonged therapy abruptly without advice.
PoTS use is off-label. Avoid asthma/bronchospasm, bradycardia, high-grade AV block, hypotension and acute decompensated heart failure; fatigue and worse presyncope can outweigh HR reduction.
Not licensed for PoTS or IST. Confirm sinus rhythm; monitor for bradycardia, AF and luminous visual phenomena. Avoid pregnancy and strong CYP3A4 inhibitors; verapamil/diltiazem coadministration is contraindicated in the SmPC.