Sympathetic neurohormonal correlates of linear and symbolic dynamics heart rate variability indexes in chronic heart failure

The aim of this study was to assess whether in chronic heart failure patients (CHF) linear and nonlinear indexes of heart rate variability (HRV) are associated with the plasma level of norepinephrine, a measure of tonic sympathetic nervous activity. In 99 CHF patients with a 24-hour Holter recording and plasma norepinephrine assay, the absolute (LFP) and normalized (LF-nu) power in the low frequency band (LF, 0.04-0.15Hz), the percentage of 3 beats patterns with no variations (0VP) and with two unlike variations (2UVP) were computed. A significant negative association (Spearman correlation coefficient) was found between LFP and PNE (r=-0.45, p<0.0001) and between LF-nu and PNE (r=-0.26, p<0.01), while the association between both 0VP and 2UVP and PNE was largely nonsignificant (r=-0.07, p=0.47 and r=0.13, p=0.19). The finding that symbolic dynamics indexes were not associated with sympathetic neurohormonal activation, suggests that the physiological link of these variables is limited to the modulation of sympathetic outflow to the sinus node.