From the Guidelines
Postural Orthostatic Tachycardia Syndrome (POTS) is primarily an overreaction of the sympathetic nervous system, not the parasympathetic nervous system. According to the 2018 ESC guidelines for the diagnosis and management of syncope 1, POTS is characterized by a marked orthostatic heart rate increase (>30 b.p.m., or >120 b.p.m. within 10 min of standing or head-up tilt) in the absence of orthostatic hypotension. This suggests that the pathophysiology of POTS is likely related to a hyperadrenergic state, which is a state of excessive sympathetic nervous system activity.
The symptoms of POTS, such as dizziness, light-headedness, weakness, fatigue, and palpitations, typically develop upon standing and are relieved by sitting or lying down 1. These symptoms are consistent with a sympathetic nervous system that is overactive, leading to excessive venous pooling and a compensatory increase in heart rate. The fact that POTS is frequently associated with deconditioning, recent infections, chronic fatigue syndrome, joint hypermobility syndrome, and a spectrum of non-specific symptoms such as headache and chest pain 1 also suggests that the sympathetic nervous system plays a key role in the pathophysiology of the condition.
Key characteristics of POTS include:
- A marked orthostatic heart rate increase (>30 b.p.m., or >120 b.p.m. within 10 min of standing or head-up tilt) in the absence of orthostatic hypotension
- Symptoms that develop upon standing and are relieved by sitting or lying down
- Association with deconditioning, recent infections, chronic fatigue syndrome, joint hypermobility syndrome, and non-specific symptoms such as headache and chest pain
- A hyperadrenergic state, which is a state of excessive sympathetic nervous system activity
Overall, the evidence suggests that POTS is primarily related to dysfunction of the sympathetic nervous system, rather than the parasympathetic nervous system. Treatment approaches should focus on improving autonomic regulation, rather than just suppressing sympathetic activity.
From the Research
Pathophysiology of POTS
- POTS is characterized by orthostatic intolerance and a symptomatic increase in heart rate upon standing, which can significantly impair patients' quality of life 2.
- The pathophysiology of POTS is complex and multifactorial, involving various mechanisms such as peripheral denervation, hypovolemia, venous pooling, beta-receptor supersensitivity, and presumed impairment of brain stem regulation 3.
- POTS can be associated with a high degree of functional disability, and therapies aimed at correcting the hypovolemia and the autonomic imbalance may help relieve the severity of the symptoms 4.
Role of the Sympathetic Nervous System
- POTS is often characterized by excessive sympathetic drive, leading to symptoms of cerebral hypoperfusion and excessive sympathoexcitation 5.
- The hyperadrenergic state in POTS is caused by excessive norepinephrine production or impaired reuptake, leading to sympathetic overactivity 2.
- Beta-blockers are an effective option for managing hyperadrenergic POTS, as they can help reduce the excessive sympathetic drive 2, 3.
Role of the Parasympathetic Nervous System
- There is limited evidence to suggest that POTS is an overreaction of the parasympathetic nervous system 2, 3, 4, 6, 5.
- The pathophysiology of POTS is more closely related to sympathetic overactivity and impaired autonomic regulation, rather than parasympathetic overactivity 2, 3, 4, 6, 5.
Management of POTS
- Management of POTS involves nonpharmacologic and pharmacologic approaches, including lifestyle modifications, volume expansion, physical countermaneuvers, exercise training, and pharmacotherapy 2, 3, 6, 5.
- The objectives of POTS management are to increase the time that patients can stand, perform daily activities, and exercise, and to avoid syncope 6.