Spectral Analysis as an Assessment of the Neural Control of the Heart: A Methodological Comparison

Abstract

It is commonly accepted that heart rate variability provides information on the neural control of the heart. Normally, three components are found in the spectrum of the cardiotachogram: A low frequency component (LF) with a frequency around 0.1 Hz, a high frequency component (HF) with a frequency around 0.25 Hz and a third component with a frequency around 0.03 Hz. Different experiments designed to relate the dominant frequency components to the amount of sympathetic and parasympathetic influence on the heart have resulted in contradictory findings. In order to examine the influence of the different methods of spectral analysis on these contradictory findings, we compared three calculatory procedures: FFT, AR1 and AR2. FFT is believed to represent the different methods based on the deterministic Fourier transform whereas AR1 and AR2 are two different versions of autoregressive spectral analysis. The results of our study indicate that the discrepancies of the findings, with respect to the different methods applied, are not caused by differences in the underlying theories (interpretation of the time series as a deterministic or random process), but by the different definitions of LF and HF.