The neuropathic postural tachycardia syndrome

Area of Science:

• Autonomic Nervous System Research
• Cardiovascular Physiology
• Neurology

Background:

• Postural tachycardia syndrome (POTS) is characterized by orthostatic symptoms and increased heart rate upon standing, without hypotension.
• Evidence suggests POTS may stem from sympathetic denervation in the legs.

Purpose of the Study:

• To investigate sympathetic nervous system function in patients with postural tachycardia syndrome.
• To determine if sympathetic denervation is localized to the legs.

Main Methods:

• Measured norepinephrine spillover in arms and legs of 10 POTS patients and 8 controls.
• Stimuli included cold pressor test, sodium nitroprusside, and tyramine infusions.

Main Results:

• Lower baseline femoral vein norepinephrine concentration in POTS patients (135 pg/mL vs. 215 pg/mL).
• Norepinephrine spillover in arms increased similarly in both groups.
• Significantly smaller increases in leg norepinephrine spillover in POTS patients during all stimuli (P<0.05).

Conclusions:

• Neuropathic postural tachycardia syndrome is linked to partial sympathetic denervation.
• The legs appear to be a primary site of this sympathetic deficit in POTS.