Postural tachycardia syndrome (POTS) is one of the most common manifestations of orthostatic intolerance.1, 2 According to current criteria for adults,3 POTS is defined by a heart rate increment of 30 beats/min or more within 10 minutes of standing or head-up tilt (HUT) in the absence of orthostatic hypotension; the standing heart rate is often 120 beats/min or higher. These criteria may not be applicable for individuals with low resting heart rate. For individuals aged 12 to 19 years, the required increment is at least 40 beats/min.3
The orthostatic tachycardia may be accompanied by symptoms of cerebral hypoperfusion and sympathetic hyperactivity that are relieved by recumbency. Symptoms of cerebral hypoperfusion include light-headedness, blurred vision, cognitive difficulties, and generalized weakness; symptoms of excessive sympathoexcitation include palpitations, chest pain, and tremulousness.
The term orthostatic intolerance is used to describe a condition in which patients develop symptoms on standing or HUT but do not fulfill the heart rate criteria for the diagnosis of POTS.4
The diagnostic criteria for orthostatic intolerance and POTS in adults are unsuitable for children and adolescents, and new criteria for these disorders in this age group have been recently proposed.5
POTS is more frequent in women (female:male ratio, 4.5:1), and most cases occur between the ages of 15 and 25 years. Up to 50% of cases have antecedent viral illness, and 25% have a family history of similar complaints