Comparison between permutation and coarse-grained entropy approaches for the assessment of short-term complexity of heart period variability

The study compares permutation and coarse-grained entropy approaches for the assessment of short-term complexity of the cardiovascular control from heart period (HP) variability recordings. Approaches were applied to simulations and to HP variability series recorded during complete vagal blockade obtained via administration of a high dose of atropine (AT). Differences between the estimated complexity indexes derived from both simulations and real data indicated that permutation entropy has a larger sensitivity to noise than coarse-grained entropy. We recommend caution in applying permutation entropy in presence of short HP variability series characterized by a low signal-to-noise ratio such as after complete vagal blockade induced by AT.