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

The aim of this study was to assess the effectiveness of chronicmedical treatment with oral propranolol and its influence onheart rate variability in patients with vasovagal syndrome.A spectral frequency domain analysis was used for the estimationof heart rate variability characteristics. Thirty-six patients,mean age 49 ± 17 years, with a history of recurrent syncopeand positive tilt testing were involved in the study. All patientsreceived oral propranolol (five patients also had a dual chamberinhibited 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 negativein 28. In 20 patients treatment was discontinued for 4 daysand a new tilt test was then performed. Eleven of these 20 patients(55%) had a positive test (P<0.001 compared with the groupin which treatment was continued). In the group of 11 patients in whom the tilt test became positiveagain after medical treatment had been withdrawn (mean age 43± 20 years) and in 11 asymptomatic controls (mean age52 ± 19 years), with no history of syncope and negativetilt testing, tile heart rate variability was assessed. Theincrease in the low frequency component from rest to the maximumvalue of heart rate variability during tilt testing was higherin the vasovagal group than in the controls (2.6 ± 1.2vs 1.5 ± 07 P = 0.02). The ratio between the increasesin the sympathetic and parasympathetic components was also higherin the vasovagal group (1.7 ± 0.7 vs 1.0 ± 0.3respectively P = 0.01). These differences during tilt testingwere eliminated after propranolol treatment. It is concluded that sympathetic activity is a predominant factorin the pathogenesis of vasovagal syndrome and that medical therapywith propranolol could be effective in vasovagal patients.