Atypical Cardiac Autonomic Neuropathy Identified with Entropy Measures

Aims: To identify Cardiac Autonomic Neuropathy (CAN) from a range of measures extracted from Heart Rate Variability (HRV), including higher moments of RR intervals and a spectrum of entropy measures of RR intervals.

Study Design: Analysis of HRV measured from participants at a diabetes screening clinic. Groups were compared using t-tests to identify variables that provide separation between groups.

Place and Duration of Study: Charles Sturt Diabetes Complications Clinic, Albury, NSW Australia.

Methodology: Eleven participants with definite CAN, 67 participants with early CAN, and 71 without CAN had their beat-to-beat fluctuations analyzed using two spectra of HRV: the spectrum of moments of RR intervals and the spectrum of Renyi entropy measures. RR intervals were extracted from ECG recordings and were detrended before analysis.

Results: Higher moments of RR intervals identified a previously unnoticed sub-group of patients who are atypical within the definite CAN group. Classification of CAN progression was better with Renyi entropy measures than with moments of RR intervals. Significant differences between early and definite CAN were found with the sixth and eighth moments, (P=.022 and P=.042 respectively), but for entropy measures P values were orders of magnitude smaller.

Conclusion: Identification of early CAN provides the opportunity for early intervention and better treatment outcomes, as well as identifying atypical cases. Our findings illustrate the value of exploring a range of different measures when attempting to detect differences in groups of patients with CAN.