M. Prinzzaiss et al., PRESYNCOPAL SYMPATHETIC WITHDRAWAL IS THE SAME IN PATIENTS WITH VASODEPRESSOR SYNCOPE AND CONTROLS WHO FAINT ON HEAD-UP TILTING, The American heart journal, 133(2), 1997, pp. 230-239
Head-up tilt provokes vasodepressor syncope in patients with this diso
rder but may also cause fainting in unaffected subjects. The aims of t
his study were to examine autonomic function and sequential changes in
heart rate variability and plasma catecholamines during graded head-u
p tilt in patients with vasodepressor syncope compared with healthy su
bjects. Studies were performed in 10 patients and 15 control subjects.
Eight negative controls completed the study; presyncope or syncope de
veloped in seven positive controls and all 10 patients. The negative c
ontrol group showed a progressive increase in mid-frequency from the s
upine position to end tilt. Patients and positive controls showed sign
ificant and similar falls in mid-frequency in the presyncope period. T
he rise in plasma norepinephrine was blunted in patients and positive
controls, whereas plasma epinephrine increased more in these groups co
mpared with the negative control group. In conclusion, the patterns of
heart rate variability and catecholamine changes could not be disting
uished in patients and positive control subjects.