Session S22.4

Sympathetic Neurohormonal Correlates of Linear and Symbolic Dynamics Heart Rate Variability Indexes in Chronic Heart Failure

R Maestri*, GD Pinna, A Porta, MT La Rovere

S. Maugeri Foundation
Montescano, Italy

Background: Sympatho-excitation plays a major role in the pathogenesis and progression of chronic heart failure (CHF) and the extent of neurohormonal activation is related to survival. Some indexes derived from heart rate variability (HRV) have been shown to be related to sympathetic cardiac modulation. The aim of this study was to assess whether these indexes are associated with the plasma level of norepinephrine, a well established biochemical measure of tonic systemic sympathetic nervous activity.
Methods: 99 stable CHF patients in sinus rhythm (age: 51±9 years, NYHA class 2.1±0.6, LVEF 24±6%) were studied. Each patient had a 24-hour Holter recording and, besides standard clinical and laboratory examinations, underwent within one week plasma norepinephrine assay. Two linear and two symbolic dynamics indexes with an established association with sympathetic cardiac modulation, were computed from consecutive 5-min sequences obtained from RR interval: the power in the low frequency band (LF, 0.04-0.15Hz), both in absolute units (LFP) and in normalised units (LF_nu), the percentage of patterns lasting 3 beats with no significant variations (0VP) and the percentage of patterns lasting 3 beats with two significant unlike variations (2UVP). The association between each index and plasma norepinephrine (PNE) was assessed by Spearman correlation coefficient.
Results: PNE, LFP, LF_nu, 0VP and 2UVP were respectively (median [interquartile range]): 347 [200-454] pg/l, 104 [40-237] ms2, 0.70 [0.62-0.75], 33 [26-39] % and 21 [17-24] %. A significant negative association 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).
Conclusions: In CHF patients, reduced LFP and LF_nu were associated with increased tonic sympathetic activity. This result confirms previous findings of an inverse relationship between LF power and sympathoexcitation in CHF, which is the opposite of what is often assumed in healthy subjects. On the contrary, symbolic dynamics indexes were not associated with sympathetic neurohormonal activation, thus suggesting that the physiological link of these variables is limited to the modulation of sympathetic outflow to the sinus node.

(Abstract Control Number: 166)