Resumen de Towards the estimation of the fractal dimension of heart rate variability data
J. L. Hernández Cáceres, H Foyaca Sibat, R Hong, María Dolores García Arcal, M Sautié, V Namugowa
With the aim of determining the Fractal Dimension (FD) of Heart Rate Variability (HRV) signals, three indices (Ix) were evaluated using HRV data. The relationship between each (Ix) and FD was established via a Numerical Experiments (NE) approach. Signals with known FD, were evaluated using different Ix. Once the functional relationship between FD and Ix was found, an estimate of the FD, based on a particular Ix can be proposed (FDIx).
The following Ix’s were analysed: A) Fractal Dimension estimated by Higuchi’s method (FDH); B) Long Range Slope (LRS), obtained from time detrended data, as well as C) the Autoregressive Dimension Index (ARDI) a measure recently proposed by Enzmann et al for evaluating HRV data. Our results showed that, for fractal signals, a statistically sound functional dependence between FD and each of the other two Ix’s was found for 1.5-1.95 FD values region. Adding non-fractal components to a pure fractal signal increased FDIx. The three indices behaved similarly, i.e. 5-7 % FDIx increase in the presence of about 30% of non-fractal contribution.
A comparison between FDIx of old vs. young subjects revealed a reduction in the FD of the elderly. This is in agreement with literature data, and points to the adequacy of the three methods here proposed.
