Definition of Postural Orthostatic Tachycardia Syndrome (POTS)
POTS is a clinical syndrome characterized by a sustained heart rate increase of ≥30 bpm (or ≥40 bpm in patients aged 12-19 years) within 10 minutes of standing or head-up tilt, occurring in the absence of orthostatic hypotension, accompanied by frequent symptoms of orthostatic intolerance that improve upon returning to a supine position. 1
Diagnostic Criteria
The diagnosis requires all five of the following components to be present for at least 3 months 1:
Heart rate criteria: Sustained increase of ≥30 bpm within 10 minutes of standing (≥40 bpm for ages 12-19 years), with standing heart rate often exceeding 120 bpm 1
Blood pressure criteria: Absence of orthostatic hypotension, defined as no sustained systolic blood pressure drop of ≥20 mm Hg or diastolic drop of ≥10 mm Hg 1
Symptom profile: Frequent symptoms of orthostatic intolerance during standing that rapidly improve upon returning to supine position, including lightheadedness, palpitations, tremulousness, generalized weakness, blurred vision, exercise intolerance, and fatigue 1
Duration requirement: Symptoms must persist for at least 3 months 1
Exclusion of alternative causes: Absence of other conditions that could explain sinus tachycardia, such as anorexia nervosa, primary anxiety disorders, hyperventilation, anemia, fever, pain, infection, dehydration, hyperthyroidism, pheochromocytoma, cardioactive drugs (sympathomimetics, anticholinergics), or severe deconditioning from prolonged bed rest 1
Clinical Presentation
Syncope is rare in POTS and typically occurs only when vasovagal reflex activation is triggered, not from POTS itself. 1, 2 The disorder predominantly affects young women and may be associated with recent infection or trauma, joint hypermobility syndrome, chronic fatigue syndrome, or severe deconditioning 1, 3, 4
Pathophysiologic Mechanisms
The core pathophysiology involves three primary mechanisms 5, 6:
Neuropathic POTS: Partial autonomic neuropathy causing impaired vasoconstriction during orthostatic stress, leading to excessive venous pooling 5, 6
Hyperadrenergic POTS: Excessive norepinephrine production or impaired reuptake causing sympathetic overactivity 5, 6
Hypovolemic POTS: Central hypovolemia often triggered by dehydration and physical deconditioning 5, 6
Important Clinical Distinctions
Do not confuse POTS with postprandial hypotension: POTS is defined by tachycardia without hypotension, whereas postprandial hypotension involves blood pressure drops after eating in autonomic failure 2. Large carbohydrate-rich meals should be avoided in POTS patients as they can worsen symptoms through splanchnic vasodilation, despite the fundamental disorder being inappropriate heart rate increase rather than hypotension 2.