Respiratory-related heart rate variability in progressive experimental heart failure

1 Laboratory of Physiology, Faculty of Medicine, Free University of Brussels, Brussels, Belgium; 2 Department of Intensive Care, Erasmus Hospital, Brussels, Belgium; 3 Unit of Diabetes and Nutrition, Catholic University of Louvain, Brussels, Belgium; 4 Department of Clinical Sciences, Ospedale, L Sacco, University of Milan, Milan, Italy; and 5 Department of Cardiology, Erasmus Hospital, Brussels, Belgium Submitted 8 November 2004 ; accepted in final form 16 May 2005 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 ± 4 to 136 ± 5 beats/min; P < 0.001) and decreased absolute and normalized (percentage of total power) HF variability from week 1 and 2 , respectively ( P < 0.01). Absolute LF variability did not change during the study until it disappeared in two dogs at week 7 ( P < 0.05). Normalized LF variability increased in moderate heart failure ( P < 0.01), leading to an increased LF-to-HF ratio ( P < 0.05), but decreased in severe heart failure ( P < 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 < r < 0.65, all P < 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 Address for reprint requests and other correspondence: K. Mc Entee, Free Univ. of Brussels, Laboratory of Physiology, CPI 604, Lennik Road 808, B-1070 Brussels, Belgium (e-mail: kmcentee{at}ulb