Respiratory-related heart rate variability in progressive experimental heart failure

Abstract

Entee. Respiratory-related heart rate variability in progressive experimental heart failure. Am J Physiol Heart Circ Physiol 289: H1729 -H1735, 2005. First published May 27, 2005; doi:10.1152/ajpheart.01129.2004.-Heart failure is associated with autonomic imbalance, and this can be evaluated by a spectral analysis of heart rate variability. However, the time course of low-frequency (LF) and high-frequency (HF) heart rate variability changes, and their functional correlates during progression of the disease are not exactly known. Progressive heart failure was induced in 16 beagle dogs over a 7-wk period by rapid ventricular pacing. Spectral analysis of heart rate variability and respiration, echocardiography, hemodynamic measurements, plasma atrial natriuretic factor, and norepinephrine was obtained at baseline and every week, 30 min after pacing interruption. Progressive heart failure increased heart rate (from 91 Ϯ 4 to 136 Ϯ 5 beats/min; P Ͻ 0.001) and decreased absolute and normalized (percentage of total power) HF variability from week 1 and 2, respectively (P Ͻ 0.01). Absolute LF variability did not change during the study until it disappeared in two dogs at week 7 (P Ͻ 0.05). Normalized LF variability increased in moderate heart failure (P Ͻ 0.01), leading to an increased LF-to-HF ratio (P Ͻ 0.05), but decreased in severe heart failure (P Ͻ 0.044; week 7 vs. week 5). Stepwise regression analysis revealed that among heart rate variables, absolute HF variability was closely associated with wedge pressure, right atrial and pulmonary arterial pressure, left ventricular ejection fraction and volume, ratio of maximal velocity of early (E) and atrial (A) mitral flow waves, left atrial diameter, plasma norepinephrine, and atrial natriuretic peptide (0.45 Ͻ r Ͻ 0.65, all P Ͻ 0.001). In tachycardia-induced heart failure, absolute HF heart rate variability is a more reliable indicator of cardiac dysfunction and neurohumoral activation than LF heart rate variability. autonomic nervous system; tachycardiomyopathy HEART FAILURE is associated with an autonomic imbalance consisting of an increase in sympathetic drive (25) and a reduction of parasympathetic activity (5). In these patients, efferent sympathetic nerve traffic has been shown to be increased in proportion to functional impairment (16), norepinephrine plasma levels are associated with an increased risk of death (7), and ␤-blocker therapy improves survival (8). Thus autonomic imbalance with prominent sympathetic activation plays an important role in heart failure pathophysiology.Cardiac autonomic imbalance can be evaluated by the spectral analysis of R-R interval (RRI) variability (35). In normal humans and in dogs, RRI variability occurs predominantly at low frequency (LF, between 0.04 and 0.15 Hz) and at high frequency (HF, between 0.15 and 1.0 Hz) (29). LF oscillations are present in both sympathetic and vagal outflows (24, 30). However, within physiological conditions, sympathetic activation is associated with an increase in LF when expressed in normalized u...

Evidence for impaired vagus nerve activity in heart failure

“…Using the phenylephrine bolus technique, Eckberg et al [27] showed over 40 years ago that arterial baroreflex control of HR was reduced in patients with LV dysfunction. Since that time, numerous groups of investigators have used a variety of techniques to support these findings, including time and frequency domain measures of RR variability, spectral analysis of HR, HR recovery following exercise, HR turbulence, and spontaneous or provoked arterial baroreflex testing [4,28,29]. Moreover, altered vagal control of HR is apparent early in the development of LV dysfunction.…”

Chronic fluoxetine reduces autonomic control of cardiac rhythms in rats with congestive heart failure

“…In heart failure, loss of HRV is indicative of decreased cardiac vagal drive and an inability of the parasympathetic system to properly buffer elevated cardiac sympathetic drive, which contributes to ventricular arrhythmogenesis in CHF (42). In dogs subjected to pacing-induced heart failure, increased sympathetic drive to the heart is reflected by increased HRV in the LF domain in the early stages of the disease (36). However, with disease progression, LF oscillations in HR diminish, likely due to reduced sensitivity of cardiac ␤-receptors (4).…”

Comparative study of heart rate variability between healthy human subjects and healthy dogs, rabbits and calves

“…HF waves are a marker of parasympathetic nervous activity, and LF waves are a marker of both sympathetic nervous activity and parasympathetic nervous activity. 6,8 The ratio of LF to HF (LF/HF) is defined as an indicator of sympathetic nervous activity.…”

“…Several studies have been performed to assess HRV in several species such as humans, 3,7 dogs, 6 pigs, 9 calves, 10,11 rabbits, 12 and rats. 13,14 However, haemodynamic parameters are totally different in each animal, 15 -17 and optimal animal models for studying HRV corresponding to human HRV are still unclear.…”