Time-courses of the Central Frequencies of Low-Frequency Components of RR Intervals, Systolic and Diastolic Pressure Variabilities in Response to Active Orthostatic Test

Salvador Carrasco-Sosa1, Alejandra Guillén-Mandujano1, Aldo Mejía-Rodríguez2
1Universidad Autónoma Metropolitana-I, 2Universidad Autónoma de San Luis Potosí


Previously, while studying the effects of static and dynamic exercises on HRV, we provided evidence supporting the adequate performance of the central frequencies of low-frequency components (CFLF) of: RR intervals (CFLFRR), systolic (CFLFSP) and diastolic (CFLFDP) pressure variabilities as cardiac and vasomotor sympathetic activity measures. Currently, in 23 healthy subjects we assessed the effects provoked by 1-min stages of supine position, active orthostatic test (AOT) and recovery to supine on the instantaneous time-courses of CFLFRR, CFLFSP and CFLFDP and of low-frequency powers (PLF) of the same variables (PLFRR, PLFSP, PLFDP), estimated by a time-frequency distribution. The response patterns of PLFRR, PLFSP and PLFDP dynamics to AOT were similar and depicted an initial prominent change (IPC) upwards, followed by their return to baseline (RB) and a final moderate change (FMC) upwards. Mean maximal points in IPC and FMC were greater (p<0.003) than their mean baseline (BL). The response patterns of CFLFRR, CFLFSP and CFLFDP were similar but in opposite direction to those of PLF: a prominent decrement in IPC, return to BL in RB and a final moderate reduction in FMC. Mean minimal points in IPC and FMC were less (p<0.001) than their mean BL. Mean correlations of PLFRR-CFLFRR, PLFSP-CFLFSP and PLFDP-CFLFDP relations ranged from -0.88±0.35 to -0.96±0.07 in IPC, -0.82±0.22 to -0.88±0.10 in RB and -0.21±0.65 to -0.41±0.57 in FMC. The table shows means of CFLFRR and CFLFDP. Our findings, initial prominent and final moderate leftward shift of CFLFRR, CFLFSP and CFLFDP dynamics that were strongly and inversely correlated with PLFRR, PLFSP and PLFDP and that CFLFRR is greater than CFLFDP, support that AOT provokes similar cardiac and vasomotor sympathetic activations, large at the onset and moderate at the ending. Thus, CFLF are trustable measures of sympathetic activity, possibly branch-specific: CFLFRR for the cardiac and CFLFDP for the vasomotor one.