Heart rate variability in patients with vasovagal syndrome.

The aim of this study was to assess the heart rate variability in patients with vasovagal syndrome (VVS). Heart rate variability was expressed as: (1) the standard deviation (SD) of the mean RR interval; and (2) the SD as a percentage of the mean RR interval (%SD). Heart rate variability was measured in VVS patients and compared with control individuals. Eighteen patients (mean age 50 +/- 14 years) with a history of recurrent syncope and positive tilt testing were included in the study. Fifteen asymptomatic individuals (mean age 53 +/- 13 years) with no history of syncope and negative tilt testing were used as a control group. The SD and %SD (39 +/- 38 and 5 +/- 4 msec) in the VVS group were statistically higher at the tenth minute of tilt testing than in the control group (20 +/- 14 and 2.5 +/- 1.8 msec, P = 0.03 and P < 0.05, respectively). The mean RR interval (mean heart rate) was shorter after the 15th minute of tilt testing in the VVS group than in the control group (RR-VVS 687 +/- 136 msec, RR-control 801 +/- 131 msec, P < 0.05). It is concluded that heart rate variability, as expressed by the SD of the mean RR interval, and the SD as a percentage of the mean RR interval (%SD) are significantly higher in VVS patients than in control asymptomatic individuals.