(1) Postural tachycardia syndrome (POTS) is a disorder characterized by a pulse rate that is too fast when the patient stands. Symptoms include rapid heartbeat, lightheadedness with prolonged standing, headache, chronic fatigue, chest pain, and other nonspecific complaints. Causes of POTS usually are not identified in individual patients. Reversible causes such as low blood volume should be ruled out.
(2) Upright posture is a fundamental human activity requiring rapid and effective circulatory and neurologic compensations in order to maintain blood pressure and consciousness. The orthostatic tachycardia syndrome is a disabling disease state described at least since 1940 and is the most common reason for referral for chronic orthostatic intolerance. Patients are often unable to hold jobs or attend schools. Yet, our understanding of its pathophysiology remains incomplete. An operational definition of the syndrome (often denoted by the acronym POTS for postural orthostatic tachycardia syndrome) includes symptoms of orthostatic intolerance associated with an increase in heart rate from the supine to upright position of more than 30 beats per minute or to a heart rate greater than 120 beats per minute within 10 minutes of head-up tilt (HUT). An exaggerated increase in heart rate, often accompanied by hypotension in association with dizziness, nausea, palpitations, heat and fatigue in the upright position has been described under other names including the hyperadrenergic syndrome of Streeten, idiopathic hypovolemia of Fouad et al, and most recently the postural orthostatic syndrome of Low et al. POTS is common, affecting an undisclosed number of patients mostly in the age range of 12 to 50 years, mostly female (approximately 80%), often with onset following a viral infection or other inflammatory condition. There is an as yet undetermined but increasing apparent prevalence in children and adolescents. Resting tachycardia is common. Symptoms of anxiety may proliferate and appear to be autonomically mediated in many cases; there is also overlap with anxiety/panic disorder.
Patterns of heart rate and blood pressure variation are shown in the figure and are from our paper which was the first to directly discuss POTS in the pediatric population.