POTS is a Specific Type of Dysautonomia, Not a Separate Condition
POTS (Postural Orthostatic Tachycardia Syndrome) is not a different condition from dysautonomia—it is one specific subtype within the broader category of dysautonomic disorders. 1
Understanding the Relationship
Dysautonomia is the umbrella term that describes any condition involving severe imbalance or dysfunction of the autonomic nervous system. 1 POTS falls under this umbrella as one of several distinct dysautonomic syndromes, similar to how familial dysautonomia (Riley-Day syndrome) and neurogenic orthostatic hypotension (multiple system atrophy) are also types of dysautonomia. 1
POTS represents the most common but least severe form of dysautonomia, characterized by chronic orthostatic intolerance. 2 The key distinction is that POTS patients have variable autonomic nervous system dysfunction that is more severe than typical neurocardiogenic syncope but less severe than other dysautonomic disorders like pure autonomic failure or multiple system atrophy. 2, 3
Key Distinguishing Features of POTS
POTS is defined by excessive orthostatic tachycardia without orthostatic hypotension, which separates it from other dysautonomic conditions:
- Heart rate increase of ≥30 bpm in adults (≥40 bpm in adolescents aged 12-19) within 10 minutes of standing or head-up tilt 1, 4
- Heart rate often exceeds 120 bpm during orthostatic challenge 1, 4
- Critically, orthostatic hypotension must be absent (no sustained BP drop of ≥20 mmHg systolic or ≥10 mmHg diastolic within 3 minutes of standing) 1, 4
- Symptoms of orthostatic intolerance present (light-headedness, palpitations, tremor, weakness, blurred vision, fatigue) 1, 4
How POTS Differs from Other Dysautonomias
The absence of orthostatic hypotension is the critical differentiator. Other dysautonomic conditions like neurogenic orthostatic hypotension (Shy-Drager syndrome) present with significant blood pressure drops and impaired heart rate responses due to autonomic failure. 1 In contrast, POTS involves inappropriate heart rate increase without concomitant blood pressure fall, likely due to excessive venous pooling, hyperadrenergic state, or severe deconditioning. 1
POTS is distinct from autonomic failure syndromes that typically cause orthostatic hypotension, such as pure autonomic failure and multiple system atrophy. 3 While these conditions involve progressive autonomic degeneration, POTS primarily affects younger individuals (ages 15-40, predominantly female) and has different underlying mechanisms. 3
Pathophysiological Subtypes
Different POTS phenotypes exist, representing varied pathophysiological mechanisms:
- Hypovolemic POTS (reduced blood volume) 5
- Neuropathic POTS (small fiber neuropathy affecting peripheral vasoconstriction) 5, 6
- Primary hyperadrenergic POTS (excessive norepinephrine levels, potentially related to norepinephrine transporter deficiency) 5
All these subtypes share the common feature of orthostatic intolerance with tachycardia but no hypotension, which defines them as POTS rather than other forms of dysautonomia. 7
Common Clinical Pitfall
Do not confuse POTS with postprandial hypotension, which can occur in autonomic failure and causes symptoms after eating due to blood pressure drops. 8 POTS is fundamentally defined by tachycardia without hypotension—syncope in POTS is rare and usually occurs only when vasovagal reflex activation is triggered, not from the POTS itself. 1, 8