Survey of Poincaré indices for measuring heart rate variability.

Multiple indices have been developed to characterise the nonperiodic behaviour of heart rate variability displayed in Poincaré plots, particularly with R-R interval data collected over 24hr periods. Some of these indices have been compared to statistical time-domain indices and some to spectral indices, while others have been used to separate data sets such as cardiac abnormalities. A survey of published indices for Poincaré plot analysis was made covering literature through the 1990's to the present day. Statistical time-domain indices and the surveyed Poincaré indices were used to analyse the same data set of R-R intervals that included: supine, standing, deep breathing, light exercise and recovery. This study examined these Poincaré indices and determined their correlations with time-domain indices, and investigated how the correlations are affected by analysing shorter time periods. Further investigation of the Poincaré indices that do not correlate strongly with SD or rMSSD may prove interesting in determining dynamic characteristics of cardiac nervous system activity.