Autonomic dysfunction / POTS
The autonomic nervous system mis-regulates heart rate and blood flow — racing heart and dizziness on standing.
Dysautonomia, including postural orthostatic tachycardia syndrome (POTS), is one of the more confidently identifiable mechanisms because it has a cheap, near-confirmatory test: a sustained heart-rate rise of ≥30 bpm (≥40 in teens) on standing without a big blood-pressure drop, measured by a 10-minute NASA lean test or tilt-table. Treatments are symptomatic rather than curative — salt and fluids, compression, and selectively beta-blockers, ivabradine, or midodrine. Notably, the RECOVER-AUTONOMIC trial found ivabradine lowered heart rate but did not improve symptoms, so drugs target the number more than the suffering.
How it's tested
10-minute standing (NASA lean) test
Measure heart rate lying down and across 10 minutes of standing. A sustained rise of ≥30 bpm (≥40 in teens) without a large blood-pressure drop suggests POTS. Doable at home with a heart-rate monitor.
Tilt-table test
The clinical reference test for orthostatic intolerance and POTS, performed in a specialist autonomic lab.
Treatment options & their evidence
Graded honestly — including treatments that failed in good trials, which is worth knowing.
Compression garments (abdominal + leg)
Mixed evidenceRandomized crossover data show full abdominal+leg compression meaningfully lowers standing heart rate; abdominal compression beats calf-only.
IVIG (intravenous immunoglobulin)
Mixed evidenceSerious harm riskOpen-label/case-series benefit in confirmed autoimmune small-fiber neuropathy, but a randomized trial for idiopathic small-fiber pain was negative — reserve for objectively confirmed autoimmune cases.
Caution: Thromboembolism, aseptic meningitis, renal injury, anaphylaxis; very expensive and supply-limited.
Salt and fluid loading
Weak evidenceMechanistically sound first-line for POTS (patients are often hypovolemic); supported by guidelines and physiology rather than high-quality trials.
Caution: Avoid with hypertension, or kidney/heart disease.
Beta-blockers (low-dose)
Weak evidenceCautionLow-dose propranolol reduces standing heart rate and symptoms in POTS reviews (~64% response), but no dedicated Long COVID RCT.
Caution: Can worsen fatigue and exercise intolerance, and is poorly tolerated if hypotensive or fatigued — use low doses.
Midodrine
Weak evidenceCautionHighest symptomatic response of the POTS orals in reviews (~78%), but evidence is short-term and physiologic, with no Long COVID-specific RCT.
Caution: Supine hypertension — don't dose before lying down; urinary retention, scalp tingling.
Ivabradine
Failed in trialsCautionpromise 0 · 2 RCTsRECOVER-AUTONOMIC (n=181) found ivabradine significantly lowered heart rate but did NOT improve POTS symptoms or quality of life — it fixes the number, not the suffering.
Caution: Visual phosphenes; avoid in significant bradyarrhythmia; not in pregnancy.