Synopsis
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.
- Adult PoTS requires chronic orthostatic symptoms plus a sustained heart-rate rise of at least 30 beats/min within 10 minutes of standing, without classical orthostatic hypotension and without another cause.
- Record supine rest, HR and BP together, then serial standing measurements to 10 minutes; one smartwatch peak or a dehydrated bedside pulse is not diagnostic.
- IST is sinus rhythm that is persistently and inappropriately fast, typically resting over 100 beats/min with a 24-hour mean over 90 beats/min, after fever, anaemia, thyroid disease, drugs and other causes are excluded.
Key red flags
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.
Investigation priorities
Reproduce orthostatic symptoms while measuring HR and BP after adequate supine rest and serially upright.
Management branches
Palpitations, dizziness or fatigue occur with a documented fast sinus rate.
- Check ABCDE/red flags, 12-lead ECG, medication/substance exposure, volume status, infection, bleeding, pregnancy where relevant and cardiopulmonary examination.
- Obtain FBC/ferritin, renal/electrolyte, glucose and thyroid tests plus targeted tests suggested by the history; treat a reversible driver first.
Key medicines
MidodrineSpecialist off-label PoTS use: 2.5 mg orally three times daily initially, titrated at intervals of more than 3 days or weekly to response; usual maximum 10 mg three times daily (30 mg/day). Take the final dose at least 4 hours before bed.
FludrocortisoneSpecialist off-label use commonly starts at 0.05–0.1 mg orally once daily; the SmPC adult replacement range is 0.05–0.3 mg once daily, but PoTS is not a licensed indication.