Nonlinear analysis of HRV during β-adrenoceptor modulation

The complex heart rate fluctuations in health tend to diminish in pathological states; this loss of complexity may contain prognostic information. Traditional heart rate variability methods are based on linear assumptions but unlike dynamic fluctuation measures take no account of the order of the occurrence of observations. It is proposed that non-linear methods may more accurately describe the structure of heart-rate time series. There is little information on the impact of drug therapy on such non-linear parameters; we have investigated the approximate entropy (ApEn) detrended fluctuation analysis (DFA) and fractal dimension (FD) of heart rate, in a normal volunteer study of agonists or antagonist of the cardiac β-adrenoceptor