excessive increase in heart rate [>30 min-1] on standing associated with orthostatic symptoms [including palpitation, chest pain syndrome, dyspnea on standing, mental clouding and difficulties with concentration], in the absence of orthostatic hypotension. Orthostatic tachycardia can produce substantial disability among otherwise healthy people. Patients typically feel tired and run down. Many also report a myriad of symptoms that are hard to categorize, often involving fatigue. We and others have reported that patients had a diminished quality of life.