DETERMINATION OF VAGAL BAROREFLEX SENSITIVITY IN NORMAL SUBJECTS

Introduction: The Valsalva maneuver (VM) is used widely to quantify the sensitivity of the vagal baroreflex loop (vagal baroreflex sensitivity, BRS_v), but most studies have focused on the heart rate (HR) response to blood pressure (BP) decrement (BRS_v down arrow), even though the subsequent response to an increment in BP after the VM (BRS_v up arrow) is important and different. Methods: We evaluated recordings of HR and BP in 187 normal subjects during the VM and determined both BRS_v up arrow, as determined by relating HR to the BP increase after phase III and BRS_v down arrow. Results: BRS_v up arrow was related inversely to age. In addition, BRS_v down arrow, age, and magnitude of phase IV were independent predictors of BRS_v up arrow in a multivariate model, accounting for 47% of the variance of BRS_v up arrow. Conclusions: The results indicate that both BRS_v up arrow and BRS_v down arrow become blunted with increasing age and that these indices relate to each other.