The effectiveness of -blockade and its influence on heart rate variability in vasovagal patients

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 In the group of 11 patients in whom the tilt test became positive again after medical treatment had been withdrawn (mean age 43 ± 20 years) and in 11 asymptomatic controls (mean age 52 ± 19 years), with no history of syncope and negative tilt testing, tile heart rate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 ± 07 P = 0.02). The ratio between the increases in the sympathetic and parasympathetic components was also higher in the vasovagal group (1.7 ± 0.7 vs 1.0 ± 0.3 respectively P = 0.01). These differences during tilt testing were eliminated after propranolol treatment. It is concluded that sympathetic activity is a predominant factor in the pathogenesis of vasovagal syndrome and that medical therapy with propranolol could be effective in vasovagal patients.