Symbolic analysis of 24h Holter heart period variability series: comparison between normal and heart failure patients.

This study proposes an application of symbolic analysis to beat-to-beat heart rate variability data derived from 24h Holter recordings both in healthy and heart failure populations. Heart rate series are transformed in a sequence of six symbols via a uniform quantization procedure. Symbols are grouped in patterns lasting three cardiac cycles and these patterns are grouped in few (four) families without any loss. The rate of occurrence of these families are found useful to distinguish two physiological conditions characterised by a different status of the autonomic nervous system (i.e. day-time and nigh-time) in healthy subjects and to discriminate between healthy and pathological populations. Indexes derived from symbolic analysis deserve to be added to traditional time and frequency domain parameters in standard analysis of heart rate variability obtained from 24h Holter recordings and tested over larger databases.