Heart rate variability characterization: time-frequency representation and nonlinear analysis

Time-frequency representation (TFR) and complexity measures based on the correlation dimension are applied to the characterization of the Heart Rate Variability, (HRV). For this study 117 subjects are analyzed from the IDEAL database, 53 patients with idiopathic dilated cardiomyopathy (IDC); 64 normal subjects (NRM). IDC patients are classified by means of their ejection fraction. The RR series are analyzed during the night period. The Choi-Williams distribution is used for the TFR analysis and three spectral bands are selected: low frequency band (0-0.07 Hz) mid frequency band (0.07-0.15), and high frequency band (0.15-0.45 Hz). The Correlation Dimension CD index is calculated determining its optimal parameters, time delay and embedding dimension. A new Dck index is introduced. A statistical analysis of the results using one-way analysis of variance (ANOVA) is applied.