Wallin, Gunnar

The sensitivity of the baroreflex control of muscle sympathetic nerve activity (MSNA) represents the responsiveness of MSNA to changes in blood pressure, whereas the baroreflex threshold diagram evaluates the likelihood of a burst occurrence over a range of resting blood pressure values. We hypothesized that the slope of the threshold diagram would show a significant positive correlation with sympathetic baroreflex sensitivity (BRS). We compared BRS calculated by the Modified Oxford technique (ModOx) with the slope and midpoint (T50) values from threshold analysis (threshold) in 10 participants (9M, age 26 yrs ± 3[mean ± SEM]). MSNA (peroneal microneurography) and blood pressure (brachial catheter) were measured at rest and during vasoactive drug boluses (ModOx). A threshold diagram was created for each subject during rest by associating DBP to the % occurrence of a burst over a 4 min period prior to the ModOx drugs. The midpoint (T50) of this diagram was defined as the DBP at which 50% of the diastoles were associated with a burst. ModOx‐derived BRS positively correlated with the slope of the threshold diagram (r = 0.64, P<0.05), but not with the T50 (r =0.11, P > 0.2). Our results suggest that the slope of the threshold diagram may be a better index of ModOx‐derived BRS values compared to more commonly used "spontaneous" baroreflex techniques. NIH HL‐083947