Segmentation of nocturnal Holter-ECG recordings with respect to different recumbent body positions

This paper evaluates a previously developed approach for minute-by-minute segmentation of night-time ECG recordings with respect to periods of different recumbent body positions (BPs). It is based on recurrence analysis of 8D-feature vectors aggregating the area under the QRS complex in eight Holter-ECG leads. The number and consistency of ECG-derived BPs was compared to reference BPs (45° resolution) extracted from 139 polysomnograms (PSGs, 120 subjects). The results indicate a high BP resolution for the ECG. Up to 3 ECG BPs per PSG BP were identified in 70% of the cases. In 60% of the ECGs, the fraction of inconsistent epoch assignments was ≤10%, and ≤30% of BP changes in the PSG were undetected. When adjacent PSG BPs were considered exchangeable, the results improved significantly, indicating a potentially unfavorable effect of the PSG sensor discretization and encouraging further steps towards the absolute classification of BPs at least in coarse categories.