Abstract

The impairment of adaptive mechanisms during orthostatic challenge may evoke orthostatic intolerance (OI): a fall in blood pressure and/or excessive tachycardia in the standing position accompanied by a wide spectrum of subjective symptoms, e.g. dizziness, discomfort lightheadedness, palpitation. OI may occasionally lead to sudden loss of consciousness and fall injuries, it may also be a possible cause of unexplained syncope. The two main forms of OI are orthostatic hypotension (OH) and postural orthostatic tachycardia syndrome (POTS). The prevalence of OH increases with age and is higher in patients with chronic diseases. The presence of OH is associated with higher all-cause mortality and increased incidence of cardiovascular disease. POTS affects predominantly young women; excessive tachycardia is accompanied by several non-specific symptoms: headache, deconditioning, cognitive impairment and gastrointestinal symptoms. Management of OI includes nonpharmacological and pharmacological methods that have limited efficacy in severe cases. The cornerstone of the management is patient education directed to finding effective physical countermeasures against OI: gradual rising from the supine and sitting position, especially in the morning; light frequent meals, avoidance of prolonged standing, exercise training. Future studies of OI should focus on the pathogenesis of OH and POTS and on more effective therapeutic methods.