Parametric analysis of heart rate variability in anaesthetised SHR and WKY rats

Spectral analysis was applied to study heart rate variability (HRV) in five spontaneously hypertensive rats (SHR) compared to five normotensive Wistar-Kyoto (WKY) rats. All them were anaesthetised with sodium pentobarbital. R-R interval series were extracted from records of ECG signals sampled at 1 kHz. Interpolation was performed to obtain an evenly spaced (100 ms) HR series. A parametric method, based on autoregressive models (AR), was applied to compute HRV power spectra. This method allowed an automatic determination of power components and related central frequencies, thus avoiding some inherent arbitrariness of FFT based methods. Compared to the SHR group, the power spectra of the WKY group showed remarkable differences in that the frequency component due to sympathetic activity disappeared whereas the frequency component related to vagal activity increased in magnitude.