[Baroreflex behavior in patients with vasovagal syncope during active standing]

INTRODUCTION. Neurally-mediated syncope, also known as vasovagal syncope, is defined as sudden and transient loss of consciousness due to a sudden and deep fall in arterial pressure. AIM. To determine the differences on the hemodynamic parameters mediating the baroreflex during active standing in patients with clinical diagnosis of vasovagal syncope as well as in healthy subjects. SUBJECTS AND METHODS. Cross-sectional, observational and comparative study. We included 20 patients diagnosed with neurally-mediated syncope and 30 controls, who underwent active orthostatic test, recording by finometry the systolic blood pressure (SBP) and heart rate (interbeat interval) in a continuous (beat to beat) and noninvasive fashion. RESULTS. Patients with syncope had a mean supine baseline SBP significantly higher than that of the healthy controls. The measured values of SBP from baseline showed a significant difference between groups, being also lower in the control group. No differences were found between groups in the fall of SBP from the first peak of heart rate to the trough. The recovery time of the SBP to the baseline was no different in controls and in patients. CONCLUSIONS. The baseline SBP and SBP drop measured from baseline in supine position was higher in patients than in healthy subjects. The magnitude of the elevation of heart rate has a tendency to be higher in the patient group compared with the control group. This suggests a sympathetic hyperactivity in patients with syncope.