The aim of this study was to assess the effectiveness of chronic medical treatment with oral propranolol and its influence on heart rate variability in patients with vasovagal syndrome. A spectral frequency domain analysis was used for the estimation of heart rate variability characteristics. Thirty-six patients, mean age 49 +/- 17 years, with a history of recurrent syncope and positive tilt testing were involved in the study. All patients received oral propranolol (five patients also had a dual chamber inhibited DDI pacemaker implanted) for a mean time 12 +/- 6 months. One patient complained of syncope during this follow-up. The tilt test repeated in 29 patients during follow-up was negative in 28. In 20 patients treatment was discontinued for 4 days and a new tilt test was then performed. Eleven of these 20 patients (55%) had a positive test (P < 0.001 compared with the group in which treatment was continued). In the group of 11 patients in whom the tilt test became positive again after medical treatment had been withdrawn (mean age 43 +/- 20 years) and in 11 asymptomatic controls (mean age 52 +/- 19 years), with no history of syncope and negative tilt testing, the heart rate variability was assessed. The increase in the low frequency component from rest to the maximum value of heart rate variability during tilt testing was higher in the vasovagal group than in the controls (2.6 +/- 1.2 vs 1.5 +/- 0.7 P = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

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.