Distal sudomotor findings in postural tachycardia syndrome.
OBJECTIVE
Postural tachycardia syndrome (POTS) is a heterogeneous disorder characterized by excessive orthostatic tachycardia in the absence of orthostatic hypotension and by sympathetic nervous system activation. Postganglionic sudomotor deficits have been used to define a neurogenic postural tachycardia POTS subtype. Norepinephrine levels above 600 pg/ml have also been used to delineate patients with a hyperadrenergic state. This study aims to determine the relationship of sudomotor abnormalities to other aspects of dysautonomia in POTS.


METHODS
Autonomic function was quantified in thirty women through tests of cardiovagal, adrenergic, and sudomotor function including quantitative sudomotor axon reflex testing (QSART) and spectral indices. Differences between patients with and without sudomotor dysfunction as defined by QSART and between patients with and without hyperadrenergic POTS were assessed with Mann-Whitney U test and Mantel-Haenszel Chi-Square test using a p value of 0.01 for significance. Spearman correlation coefficients were used to test raw sweat volume correlations with other variables.


RESULTS
Of 30 women (ages 20-58), 17 patients (56%) had an abnormal QSART which was typically patchy and involved the lower extremity, while 13 patients had normal QSART results. Other autonomic tests, catecholamines or spectral indices did not correlate with QSART results. No differences in autonomic tests or spectral indices were observed between hyperadrenergic and non-hyperadrenergic POTS.


CONCLUSIONS
Our findings confirm that a large subset of POTS patients have sudomotor abnormalities which are typically patchy in distribution but do not correlate with other tests of autonomic function. Further studies are needed to determine the best method of endophenotyping patients with POTS.
Peltier
Amanda Catherine
AC
Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Nashville, USA. amanda.peltier@vanderbilt.edu
Garland
Emily
E
Raj
Satish R
SR
Sato
Kyoko
K
Black
Bonnie
B
Song
Yanna
Y
Wang
Lily
L
Biaggioni
Italo
I
Diedrich
Andre
A
Robertson
David
D
D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001369:Axons / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D054972:Postural Orthostatic Tachycardia Syndrome / Q000503:physiopathology*; D011187:Posture / Q000502:physiology