Postural orthostatic tachycardia syndrome

Orthostatic intolerance can be defined as inability to tolerate upright posture relieved by recumbence. Postural orthostatic tachycardia syndrome (POTS) is a form of orthostatic intolerance defined as sustained increase in heart rate of >= 30 bpm or increase of heart rate to >= 120 bpm within 10 min of standing or head-up tilt associated with symptoms of orthostatic intolerance and absence of orthostatic hypotension. POTS patients are mostly female with 4-5:1 ratio and age range from 15 to 50. Several pathophysiological mechanisms are thought to underlie POTS. Some of the possible mechanisms are distal peripheral neuropathy, abnormalities of central control of sympathetic nervous system, impaired synaptic norepinephrine reuptake, renin-angiotensin-aldosterone axis disturbance and altered norepinephrine synthetic pathway. The most common symptoms related to POTS are light-headedness, presyncope, weakness and palpitations. Exacerbation of symptoms with standing and symptoms relieved with recumbence is a characteristic feature of POTS. Active stand test and passive head-up tilt table test are used in diagnosing POTS, along with detailed history and examination. Nonpharmacological therapy of POTS includes increase in daily salt and water intake, and exercise training. Pharmacological therapy is directed at expanding fluid volume, increasing peripheral vascular resistance and reducing central sympathetic activity The majority of patients experience substantial improvement after correct diagnosis and appropriate therapy.