Hyperadrenergic Postural Tachycardia Syndrome

Publisher Summary This chapter discusses hyperadrenergic postural tachycardia syndrome (POTS) or hyperadrenergic orthostatic intolerance, which designates orthostatic intolerance patients. Patients with orthostatic intolerance have symptoms on standing that resemble those elicited by inadequate cerebral blood flow. They have heart rate increases on standing of at least 30 beats/min with dizziness, palpitations, poor exercise tolerance, and presyncopal symptoms, although syncope itself is infrequent. There appear to be dozens, perhaps hundreds, of underlying pathophysiologies because orthostatic intolerance (POTS) is a symptom complex rather than a disease entity itself. There are two major problems in evaluating patients having this syndrome. First, physical deconditioning can be difficult to distinguish from true pathology; most commonly patients encountered have both an altered pathophysiology and an overlay of deconditioning. Second, many relatively common diseases have orthostatic intolerance as a rare presentation, and the clinician must exercise special caution that in diagnosing POTS, the continued importance of ongoing evaluation for the true cause of the illness is not neglected because there may be important therapeutic implications as well. Many of these patients have orthostatic intolerance because of a peripheral cause. However, others have a pathophysiology that likely originates in the brain.