HRV and neurohumoral activation in cardiac failure

In patients with cardiac failure, when either short term or 24 hour recordings were analysed, reduced HRV was consistently observed and interpreted as a result of predominantly sympathetic and reduced vagal modulation of sinus node.1 It was also reported that the extent of reduction of time domain measures of HRV could be correlated with indices of severity of the disease, whereas the relation between the results of spectral analysis of HRV and the different degrees of severity of cardiac failure appeared more complex and of not unique interpretation. Compared with normal subjects,1 ,2 patients with mild cardiac failure presented a significant increase in low frequency (LF) and a reduction in high frequency (HF) power, whereas RR variance was only slightly decreased—that is, a spectral pattern consistent with that observed in most clinical conditions characterised by enhanced sympathetic and reduced vagal modulation of sinus node.3 On the contrary, the power spectrum of patients in the most advanced phases of the disease1-4 showed a progressive reduction of the energy in the LF and HF range, with most of the residual power distributed within the very low frequency (VLF) band. Thus, at variance with New York Heart Association (NYHA) …