Efficacy of Intravenous Atenolol for Prevention of Neurally Mediated Syncope Induced by Head‐Up Tilt Testing

Background In our hospital we performed a prospective, randomized, double‐blind, and controlled study on the efficacy of oral atenolol in patients with neurocardiogenic syncope. Fifty patients with clinically diagnosed vasovagal syncope were included.A complete study to discard other possible causes of syncope was performed in all patients. In the first part of this study, before the patients were randomized in two groups to receive either atenolol or placebo, a baseline tilt test with a protocol of 80° during 45 minutes was performed. Methods All patients with a positive response (18) underwent an infusion of intravenous atenolol and the test was repeated. Four patients with a positive baseline test did not accept the infusion of that drug and, therefore, were not included in this protocol. Atenolol prevented a second positive tilt in 5 of 18 patients (27.8%). Results There were no significant differences between both groups with respect to age, gender, blood pressure, heart rate, and number of episodes of syncope. Thirteen patients had a recurrent positive response in spite of atenolol. Eleven of these subjects had a syncope during the first tilt test. In seven of these patients (63.6%) atenolol prevented severe symptoms 'syncope) in the second test. In patients with a significant cardioinhibitory response in the first test, atenolol did not prevent a second positive response in any of the patients. Conclusions In our study, intravenous atenolol was not an efficient drug to prevent a second positive tilt test in patients with clinically diagnosed vasovagal syncope and a first positive tilt‐table test. Only 5 of 18 patients (27.8%) had a negative response in the second test after the infusion of that drug. This drug was more effective in patients with a vasodepressor or mixed response in the first tilt test. A.N.E. 1999; 4(2):130–136