DYNAMIC DETECTION OF RHYTHMIC OSCILLATIONS IN HEART-RATE TRACINGS - ASTATE-SPACE APPROACH BASED ON 4TH-ORDER CUMULANTS

This paper presents a new procedure specifically aimed at providing a dynamical detection of the oscillations occurring in long-term heart-r ate (HR) tracings. The procedure is based on a time-variant state-spac e modelling of the fourth-order cumulants of the HR signal. The state- space estimator was selected because of its demonstrated capability to distinguish between deterministic and stochastic components of the si gnal, while the fourth-order cumulants of the signal were used as inpu t of the model to further reduce adverse effects of coloured, white an d 1/f Gaussian noise possibly present in the input data. The procedure was tested by the analysis of simulated signals and its performance w as compared with the results obtained by state-space modelling applied directly on the test signals (instead of on the fourth-order cumulant s of the signals) and by the more traditional auto-regressive modellin g. The comparison has shown a clear superiority of the proposed proced ure over the other techniques in discriminating deterministic oscillat ions from coloured noise. Finally, the applicability of the procedure to biological data was verified by analysing five experimental HR trac ings recorded in normal subjects during laboratory and daily life cond itions.