Hemodynamic parameters and baroreflex sensitivity during head-up tilt test in patients with neurally mediated syncope.

BackgroundWe aimed to investigate differences in hemodynamic parameters and the role of baroreflex sensitivity (BRS) in patients with a history of neurally mediated syncope (NMS) compared with a control group. MethodsHemodynamic parameters and BRS were continuously measured noninvasively using a Finometer at rest and during passive head-up tilt test (HUT) in patients with a history of NMS (n=55) and a control group (n=77). The tilting period was divided into pretest (resting supine position), initial (first 3 minutes of tilting), last (last 3 minutes of tilting), and recovery (3 minutes after tilting was complete) periods. ResultsDecrease in systolic blood pressure (-14.7 15.7mm Hg vs-7.6 +/- 14.3mm Hg, P<0.01) was more prominent and increase in total systemic peripheral resistance was significantly smaller (67.6 +/- 418.7dyn.s/cm(5) vs 189.4 +/- 261.0dyn.s/cm(5), P=0.04) from the initial to the last period of HUT in the patient group compared with the control group. BRS was significantly higher during the pretest period (20.1 +/- 10.9ms/mm Hg vs 13.0 +/- 8.1ms/mm Hg, P<0.01) in the patient group, while the decrease in BRS from the pretest to the initial period was greater (-8.5 +/- 6.0ms/mm Hg vs-3.2 +/- 4.1ms/mm Hg, P=0.01). ConclusionsDysfunctional BRS in response to orthostatic stress might be involved in pathological autonomic cardiac modulation of NMS.