Hyperadrenergic activity and the Postural Tachycardia Syndrome (PoTS)

Abstract

The aim of this study was to compare cardiovascular autonomic function of Hyperadrenergic PoTS, defined as a plasma norepinephrine >; 600 ng/mol during orthostasis, to PoTS due to other causes. Clinical cardiovascular autonomic function test results were reviewed. 50 PoTS patients were identified; 18 with Hyperadrenergic PoTS. Plasma norepinephrine was higher while upright (383 ± 99 vs 726 ± 112 ng/mol, p<0.05) and supine (233 ± 58 vs 422 ± 128 ng/mol, p<0.05) in Hyperadrenergic PoTS. There were no differences in heart rate or blood pressure during cold pressor challenge, mental stress, isometric exercise, deep breathing and short‐term (9 min) head‐up tilting, between groups (all p>;0.05). Valsalva manoeuvre derived Valsalva ratio, blood pressure recovery time and vagal baroreflex sensitivity were not different (all p>;0.05), whereas adrenergic baroreflex sensitivity was lower in Hyperadrenergic PoTS (p<0.05). Hyperadrenergic PoTS had lower prolonged (60 min or less) head‐up tilt tolerance (p<0.05); termination was predominantly due to patient request not differences in heart rate or blood pressure. These findings suggest that, 1) Hyperadrenergic PoTS have elevated supine and upright, plasma norepinephrine levels and 2) Hyperadrenergic PoTS do not have distinctive cardiovascular autonomic function except for decreased adrenergic baroreflex sensitivity and reduced prolonged orthostatic tolerance.