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Postural orthostatic tachycardia syndrome (POTS, also known as postural tachycardia syndrome) is a condition in which a change from the supine position to an upright position causes an abnormally large increase in heart rate, called tachycardia. Other symptoms of an orthostatic nature — occurring in response to upright posture — may accompany the tachycardia.〔 The causes of POTS are poorly understood, and it is likely that several distinct underlying problems can lead to the symptoms of POTS.〔 A variety of treatments, including exercise and medications, can improve symptoms for the majority of people with POTS. Many experience "a reasonable recovery with recovery defined as the relative absence of orthostatic symptoms alone with the ability to perform the activities of daily living with minimal restriction", while in others the condition persists indefinitely.〔 It has been estimated that there are between 500,000 and 3,000,000 people with POTS in the United States alone.〔 ==Signs and symptoms== The hallmark symptom of POTS is an increase in heart rate by at least 30 beats per minute within 10 minutes of assuming an upright position.〔 For people aged between 12 and 19, the minimum increase for diagnosis is 40 beats per minute.〔 This symptom is known as orthostatic (upright) tachycardia (fast heart rate). It occurs without any coinciding drop in blood pressure, as that would indicate orthostatic hypotension.〔 It is accompanied by other features of orthostatic intolerance — symptoms which develop in an upright position and are relieved by reclining.〔 These orthostatic symptoms include palpitations, light-headedness, chest discomfort, shortness of breath,〔 weakness and blurred vision.〔 In up to one third of people with POTS,〔 fainting occurs in response to postural changes or exercise.〔 Migraine-like headaches are common, sometimes with symptoms worsening in an upright position (orthostatic headache).〔 Some people with POTS develop blotchy, sometimes purplish skin when standing, especially over the feet (indicative of blood pooling).〔 48% of people with POTS report chronic fatigue and 32% report sleep disturbances.〔 Others exhibit only the cardinal symptom of orthostatic tachycardia.〔 The hypermobility type of Ehlers–Danlos syndrome (EDS) sometimes co-occurs with POTS.〔 This type of EDS is characterized by loose, clicking joints prone to subluxations and dislocations, skin that exhibits moderate or greater laxity, meeting the Beighton criteria for joint hypermobility, and other miscellaneous signs of laxity including the ability to perform a reverse Namaskar sign and the ability to touch the tip of the nose with the tongue. POTS is also often accompanied by vasovagal syncope, with a 25% overlap being reported. There is significant overlap between POTS and chronic fatigue syndrome, with evidence of POTS in 25-50% of CFS cases.〔 Fatigue and reduced exercise tolerance are prominent symptoms of both conditions, and dysautonomia may underlie both conditions.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Postural orthostatic tachycardia syndrome」の詳細全文を読む スポンサード リンク
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