Effect of Prehypertension and Blood Pressure Reactivity on Orthostatic Response in Young Men: Relationship with HF and LF HRV Power

The orthostatic test is commonly used to evaluate sympathetically mediated blood pressure (BP) reactivity in health and disease. Whether orthostatic hyperreactivity is inherent in prehypertensives, if the cardiovascular response is the same between normotensives and prehypertensives of the same reactivity, and what are the explanatory variables for cardiovascular orthostatic responses till now remains unclear. The study was carried out in 81 normotensive and 69 prehypertensive men enrolled from V.N. Karazin Kharkiv National University student population. Informed consent was given by each participant. After 5 min of supine rest subjects moved into the standing position for 5 minutes. ECG was continuously recorded, heart rate (HR), low frequency and high frequency HRV power (LF and HF) were interpreted (CardioLab 2010). Systolic and diastolic BP (SBP and DBP) were measured at the end of each stage (Nissei WS‐1011). All subjects were divided into normoreactors with DBP response (ΔDBP) less than 11 mm Hg and hyperreactors with ΔDBP more than 11 mm Hg. GLM MANOVA was used to test for possible effects of orthostatic reactivity, prehypertension and their interaction on HR, SBP, DBP, LnLF, LnHF and their responses. The stepwise multiple linear regression analysis was carried out to assess the relative importance of orthostatic reactivity, prehypertension, LnLF and LnHF power in cardiovascular responses. An exaggerated ΔDBP was observed in 47.4% of normotensives and 44.6% of prehypertensives. In normotensive and prehypertensive hyperreactors the resting DBP (DBPrest) was less compared with normoreactors (Table 1) possibly due to the higher sensitivity of baroreceptors in hyperreactors. The ΔSBP was less in prehypertensive then in normotensive normoreactors (Figure 1) supposedly due to some degree of autonomic failure and desensitization of arterial baroreceptors by a persistent increase in BP. Apparently, they are at high risk of orthostatic hypotension development. The multiple linear regression analysis revealed that the ΔHR was not associated with orthostatic reactivity (Table 2) but was negatively associated with ΔLnHF in all subjects and with ΔLnLF in prehypertensives, indicating that the increment of HR depends on decrease in the cardiovagal outflow in all subjects and, also, on decrease in inhibitory influence on presympathetic medullary neurons, according to our hypothesis, in prehypertensives. The ΔSBP was positively associated with orthostatic reactivity and negatively with resting LnLF by height interaction (Table 2), indicating that the taller is the subject the more the inhibition of resting sympathetic outflow reduced increment in SBP. The ΔSBP and ΔDBP were positively associated with ΔLnLF by resting LnHF interaction (ΔLnLF*LnHFrest) indicating that the increment of BP led to the increase in inhibition of the sympathetic nervous system activity in the case of high cardiovagal outflow. In conclusion, in hyperreactors the resting DBP was less compared with normoreactors; prehypertensive normoreactors may represent a population developing orthostatic hypotension; the increment in HR was determined by decrease in cardiovagal outflow in all subjects and by decrease in sympathetic inhibition in prehypertensives; the inhibition of resting sympathetic outflow reduced increment in SBP depending on height; the increments of BP caused inhibition of the sympathetic nervous system activity only in the case of high cardiovagal activity. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .