ASSESSMENT OF AUTONOMIC FUNCTION AT REST AND DURING TILT TESTING IN PATIENTS WITH VASOVAGAL SYNCOPE

This study evaluated autonomic nervous system Function in 30 patients with syncope and a positive tilt test result, 20 with a negative test result, and 20 healthy controls. Indexes of heart rate variability wer e measured during the intervals immediately before and after tilt, whi le all subjects were asymptomatic, and over a 24-hour period. There we re no significant differences among the groups in any of the indexes o f heart rate variability over the 24-hour period. In patients with a p ositive tilt result, tilting caused a decrease in low-frequency (LF) a nd high-frequency (HF) bands, although the LF/HF ratio did not signifi cantly change, In patients with a negative tilt result there was a dec rease in the HF band but no other significant changes. In the controls there was an increase in the IF band and LF/HF ratio and a decrease i n the HF band. Our findings showed that patients with vasovagal syncop e have no chronic differences from normal subjects in autonomic nervou s system activity, but that these patients respond differently to the orthostatic stimulus.