Postural Orthostatic Tachycardia Syndrome

Postural orthostatic tachycardia syndrome is a chronic disorder of autonomic regulation in which standing causes an excessive heart rate rise without a sustained fall in blood pressure, accompanied by symptoms of orthostatic intolerance lasting at least 3 months. It predominantly affects women aged 15 to 50 and frequently follows infection, trauma, surgery, pregnancy or viral illness (including COVID-19).

• Definition: sustained rise in heart rate of at least 30 beats per minute within 10 minutes of standing (at least 40 beats per minute for ages 12 to 19), without orthostatic hypotension (fall in systolic of 20 mmHg or more).
• Heterogeneous mechanisms: hypovolaemia, neuropathic (small fibre) type, hyperadrenergic type, autoimmune type, joint hypermobility, mast cell activation.
• Associated conditions: Ehlers-Danlos syndrome (hypermobile type), chronic fatigue syndrome, migraine, irritable bowel syndrome, fibromyalgia, anxiety, iron deficiency.
• Course: many improve over years with treatment; some recover fully.

• Palpitations, light headedness, presyncope, fatigue, exercise intolerance, blurred or tunnel vision on standing.
• Brain fog, headache, tremulousness, sweating, nausea, bloating, chest discomfort, sleep disturbance.
• Symptoms worse with heat, prolonged standing, meals, menstruation, dehydration, and exercise; relieved by lying.
• Acrocyanosis or dependent blue purple discolouration of legs on standing.
• Syncope is less frequent than in vasovagal disease.
• Examination: resting tachycardia, hypermobility (Beighton score), signs of dehydration, normal cardiac examination.
• Red flags prompting alternative diagnoses: weight loss, fever, chest pain, syncope with exertion, abnormal ECG, focal neurology, marked hypotension.

• 10-minute active stand test: supine rest for 5 to 10 minutes, then record heart rate and blood pressure every minute for 10 minutes standing. Positive if heart rate rises by 30 beats per minute or more (40 or more in 12 to 19 year olds) without drop in systolic blood pressure of 20 mmHg or more. Stand off medication (beta blockers, fludrocortisone, midodrine, ivabradine) where possible, with adequate hydration, after fasting 3 hours and avoiding caffeine.
• ECG to exclude pre-excitation, long QT, and conduction disease.
• Bloods: full blood count, ferritin, urea and electrolytes, thyroid function, glucose, B12, folate, morning cortisol, calcium, coeliac serology; consider plasma metanephrines and standing plasma catecholamines.
• Echocardiography if murmurs or abnormal ECG; 24 to 48 hour ambulatory monitoring to exclude arrhythmia.
• Tilt table test or autonomic testing via specialist when unclear.
• Differentials: dehydration, anaemia, thyrotoxicosis, inappropriate sinus tachycardia, orthostatic hypotension, deconditioning, adrenal insufficiency, phaeochromocytoma, anxiety or panic disorder, medication effect.

Non-pharmacological (first line)

• Fluid 2 to 3 litres daily; salt 6 to 10 g daily (1 to 2 teaspoons of salt or salt tablets 1 g two to three times daily) if no hypertension or renal disease.
• Compression garments to waist (20 to 30 mmHg).
• Avoid triggers: prolonged standing, hot environments, heavy meals, alcohol, caffeine excess.
• Smaller, more frequent meals with slow rise after eating.
• Raise head of bed by 10 degrees if morning symptoms.
• Graded exercise: begin with recumbent exercise (rowing machine, recumbent bike, swimming) for 20 to 30 minutes 3 to 5 times weekly, progressing over 3 months to upright exercise. Strongly evidence supported and essential.
• Counter manoeuvres: leg crossing, squatting, muscle tensing.
• Treat iron deficiency: ferrous sulphate 200 mg orally once daily or on alternate days, aim for ferritin above 50 micrograms/L; consider intravenous iron for intolerance.
• Cognitive and psychological support for anxiety or low mood.

Pharmacological (symptom persistence; specialist guided)

• Propranolol 10 to 20 mg orally up to four times daily (low dose preferred; high doses may worsen symptoms), or bisoprolol 1.25 to 2.5 mg once daily, or metoprolol 25 mg twice daily. Avoid in asthma and bradycardia.
• Ivabradine 2.5 to 7.5 mg orally twice daily (start 2.5 mg twice daily); avoid in pregnancy.
• Fludrocortisone 0.1 to 0.2 mg orally once daily for hypovolaemic type; monitor blood pressure, potassium and oedema.
• Midodrine 2.5 to 10 mg orally three times daily (daytime only; last dose at least 4 hours before bed) for neuropathic type; watch for urinary retention, scalp tingling and supine hypertension.
• Pyridostigmine 30 to 60 mg orally up to three times daily; gastrointestinal side effects.
• Desmopressin 0.1 to 0.2 mg orally at night in selected specialist cases; monitor sodium.
• Hyperadrenergic type: low dose clonidine 0.05 to 0.1 mg orally twice daily or methyldopa 125 to 250 mg orally twice daily, under specialist care.

Special groups

• Adolescents: school adjustments (water bottle, salt, seating), graded exercise, and family education are central.
• Pregnancy: symptoms may improve or worsen; avoid ivabradine and be cautious with other drugs; increase fluids and salt.
• Hypermobile patients: physiotherapy for joint stability.

Follow up and referral

• Review every 4 to 8 weeks initially.
• Refer to cardiology or autonomic clinic if diagnosis uncertain, severe functional impairment, syncope or no response to first line measures.