Postural tachycardia syndrome: multiple symptoms, but easily missed

The evolution of upright posture is usually considered an advantage in humans. For people with postural tachycardia syndrome (PoTS) it can present a daily challenge. Although orthostatic intolerance is often associated with older people, PoTS tends to affect young women who present with multiple, non-specific symptoms and significant functional impairment.1 PoTS was characterised in 1993,2 but previously existed under various names including irritable heart, soldier's heart, and idiopathic orthostatic intolerance. It is a heterogeneous group of disorders sharing similar characteristics as a consequence of abnormal autonomic nervous system response to assuming upright posture. When humans stand up, approximately 500 ml of blood descends from the thorax into the abdominal cavity and limbs. A normal autonomic nervous system responds with immediate peripheral vasoconstriction, increase in heart rate of 10–20 beats per minute (bpm), and minimal change in blood pressure.1 In patients with PoTS this mechanism does not respond appropriately; the exact pathophysiology remains unclear.3 A likely mechanism is inadequate vasoconstriction on standing, resulting in pooling of blood in splanchnic and peripheral vasculature. Heart rate and catecholamine levels increase further to compensate. Symptoms of cerebral hypoperfusion including dizziness and syncope occur, often in the presence of normal blood pressure. Ironically, some patients with PoTS have a hypertensive response to standing.1 Diagnosis is usually made following a tilt table test or 10-minute stand test. The definition is arbitrary, but agreed by consensus (Box 1).4 Heart rate increases but, by definition, blood pressure does not necessarily drop. However, there is overlap with neurally mediated hypotension and some …