Multiscale analysis of acceleration and deceleration of the instantaneous heart rate using symbolic dynamics

The multiscale analysis of physiologic time series such as the RR interval time series has revealed that the entropy differs according to the scale. Furthermore, healthy subjects show different characteristics on the different time scales compared to patients. Instead of calculating entropies of the time series, the sequence of acceleration and deceleration of the instantaneous heart rate may also be investigated by means of binary symbolic dynamics. This kind of analysis revealed that the healthy heartbeat series also contains numerous regular binary sequences indicating runs of acceleration or deceleration. Here, we investigate whether this approach yields new information when applied to multiple time scales. We investigate the occurrence of binary patterns of length 8 on different time scales of heart rate series from healthy subjects and patients with congestive heart failure (CHF). Healthy subjects and CHF patients show different occurrences of binary patterns. These occurrences change especially on scales 1 to 5. Healthy subjects show more pronounced changes than CHF patients. At larger scales only gradual changes were observed. In conclusion, the application of binary symbolic dynamics on different scales yields new information, in particular on small scales.