APPLICATION OF LINEAR AND NONLINEAR TIME-SERIES MODELING TO HEART-RATE DYNAMICS ANALYSIS

The linear autoregressive (AR) model is often used to investigate the pathophysiologic mechanisms controlling heart rate (HR) dynamics. This stud implemented parametric models new to this field to determine if a more appropriate HR dynamics modeling structure exists., The linear AR and autoregressive-moving average (ARMA) models, and the nonlinear polynomial autoregressive (PAR) and bilinear (BL) models were fit to i nstantaneous HR time series obtained from nine subjects in the supine position, Model orders sere determined by the Akaike Information Crite ria (AIC). Model residual variance was used as the primary intermodel comparison criterion, with significance evaluated by a chi(2) distribu ted statistic, The BL model best represented the HR dynamics, as its r esidual variance was significantly (p < 0.05) smaller than that of the corresponding AR model for nine out of nine data sets, In all cases, the BL model had a smaller residual variance than either the ARMA or P AR models, The bilinear model was ineffective at data forecasting, how ever, ne show that this cannot reflect BL model validity because poor prediction is inherent to the BL model structure, The apparent superio rity of the nonlinear bilinear model suggests that Future heart rate d ynamics studies should put greater emphasis on nonlinear analyses.