Independent role of reduced arterial baroreflex sensitivity during head-up tilt testing in predicting vasovagal syncope recurrence

The involvement of arterial baroreflex function in the pathophysiology of vasovagal syncope (VVS) is controversial, and there are no published data supporting its clinical usefulness. The aim of this study was to evaluate the role of arterial baroreflex sensitivity (BRS) at baseline and during head-up tilt testing (HUT) in predicting the recurrence of VVS. The study involved otherwise healthy patients with a history of unexplained syncope who underwent diagnostic HUT by being tilted to 70 degrees after 10 min supine rest; the test was potentiated by the administration of 300 mu g of nitroglycerine (NTG) after 20 min. Beat-to-beat heart rate and systolic blood pressure were continuously recorded, and the sequence method was used to measure arterial baroreflex control of heart rate. The 190 enrolled patients were followed up for 18 +/- 6 months, during which 34 experienced a total of 90 episodes of syncope recurrence. In a stepwise multivariate analysis, female gender [hazard ratio (HR): 2.74; P = 0.008], the presence of >= 3 syncope events before HUT (HR: 3.36; P = 0.004), and BRS below median value after the start of HUT or after the administration of NTG (HR: 3.79; P = 0.006) were significantly and independently associated with the recurrence of syncope. Moreover, when a BRS value of less than the median was added to the other independent factors in a stepwise model, a significant increase in discrimination (C-index: 0.77) and model fitting (P = 0.001) was observed. Reduced BRS during HUT has independent and incremental value in predicting the recurrence of syncope, thus supporting its potential usefulness in the clinical management of patients.