Predictors of tilting test negativization during beta-blocker treatment in patients with neurocardiogenic syncope

The cardioinhibitory and/or vasodepressor reflex, always preceded by adrenergic activation, has recently been accepted as the main mechanism of neuromediated syncope. The aim of this study was to verify if efficacy of beta-blockers, in the treatment of neuromediated syncope, may be predicted on the basis of clinical variables and data derived from tilting test.

We retrospectively analyzed 23 patients with recurrent or traumatic unexplained syncopal episodes, with a positive tilting test, who repeated the test during beta-blocker therapy. According to the second tilting test results, patients were divided into Group 1 (19 patients) with a positive second test, and Group 2 (4 patients) with a negative second test.

No difference was found between the two groups in age, gender, number of syncopal episodes before observation, and period (days) between the two tests. Moreover, there was no difference between the two groups in the kind of positive response to tilting test, in heart rate at tilting (minimum, maximum, delta and slope of increase), and in the minimum, maximum and slope of heart rate increase before syncope. Delta heart rate before syncope was 15 b/min in Group 1, and 28 b/min in Group 2 (p = 0.011). Taking a discriminant value of 20 b/min, 100% sensitivity and 68% specificity were found.

Heart rate increase before syncope identifies patients with negativization of tilting test on beta-blocker therapy. However, the clinical value of the second test for driving therapy is controversial.