Neurocirculatory abnormalities in chronic orthostatic intolerance.

Area of Science:

• Cardiology
• Autonomic Nervous System Research
• Clinical Physiology

Background:

• Chronic orthostatic intolerance (COI) affects patients with postural tachycardia syndrome (POTS) and some with neurocardiogenic syncope (NCS).
• Investigating neurocirculatory abnormalities during supine rest in COI patients is crucial for understanding these conditions.

Purpose of the Study:

• To determine if patients with COI, POTS, or NCS have distinct neurocirculatory abnormalities during supine rest.
• To compare supine hemodynamic and neurohormonal profiles between POTS, NCS, and healthy individuals.

Main Methods:

• Adult patients with COI (POTS or NCS) and healthy volunteers underwent measurements of plasma catecholamines and forearm hemodynamics.
• Comparison of heart rate, mean arterial norepinephrine and epinephrine levels, and forearm vascular resistance between groups.

Main Results:

• The POTS group exhibited a significantly faster resting heart rate compared to NCS and control groups.
• POTS patients showed higher plasma norepinephrine and epinephrine levels than both NCS and control groups.
• NCS patients demonstrated higher forearm vascular resistance during supine rest than the POTS group.

Conclusions:

• Postural tachycardia syndrome (POTS) is characterized by increased resting heart rate and sympathetic nervous system and adrenomedullary outflows.
• Elevated sympathetic outflow may contribute to the characteristic tachycardia observed in POTS.
• Neurocardiogenic syncope (NCS) involves forearm vasoconstriction at rest, without evidence of sympathoneural or adrenomedullary activation.