Cardiac autonomic neuropathy associated alteration of sympatho-vagal balance through the tone entropy analysis of heart periods

This study presents the usefulness of tone-entropy (T-E) analysis of heart rate variability (HRV) using short term ECG recordings (∼20 minutes) for screening the degree of severity (mild, definite and severe) of cardiac autonomic neuropathy (CAN). Tone reflects sympathovagal balance whose validity has been already examined on typical physiological cases. Entropy which is the autonomic regularity activity was evaluated though Shannon entropy of HRV. Both indexes were defined on a distribution of successive variations of heart periods. The results showed that the tone was high and the entropy was low in the definite group compared with the early and normal group. When the result was plotted in twodimensional T-E space, it revealed a curve-linear relation between the tone and entropy. The findings could form the basis of a cheap and non-invasive test for screening CAN in patients with or without diabetes.