Time-variant AR spectral estimation in the study of vasovagal syncope

The AutoRegressive (AR) spectral estimation is implemented in a recursive way with a forgetting factor w both in the classical RLS form, with a constant w value, and in the Fortescue variant with w changing with time, according to the changing characteristics of the signals. The time-variant AR algorithm is here employed, in the study of heart rate and blood pressure variability signals obtained during syncope episodes. The spectral parameters (LF, HF powers, LF/HF ratio), which are able to quantify the sympatho-vagal balance in the assessing of the heart rate and blood pressure values, are evaluated on a beat-to-beat basis, in order to obtain more information about the role played by the autonomie nervous system during these episodes.