500 HEART BEATS FOR ASSESSING DIABETIC AUTONOMIC NEUROPATHY

The objective of the study was to investigate the usage of a new definition of autonomic dysfunction in assessing diabetic autonomic neuropathy (DAN), compared with the existing methods of evaluation, such as changes in heart rate variability (HRV) and autonomic scoring. In a prospective study, 21 diabetic patients and 9 non-diabetic volunteers were enrolled for assessment of DAN. Three methods were employed: scoring of the autonomic function involving 3 manoeuvres (more than 3000 heart beats), reduction in components of the power spectrum (PSD) of the HRV (Valsalva manoeuvre along less than 600 heart beats) and finally measurement of autonomic dysfunction as provided by the ANSiscope TM (supine position for 572 heart beats). All individual comparisons were taken between the three classifications given by the methods. Pathways leading from one classification to another were thoroughly represented. From 3 groups in the clinical classification (nondiabetic, diabetic without complications, diabetic with complications), autonomic scoring divided patients in 3 other groups with 15 healthy cases, 14 early cases and 1 case of advanced DAN. These 3 groups of scored patients were transformed in 2 ordered groups of equal size, by consideration of the amount of LF and/or HF component reduction (normal, abnormal). From this PSD distinction between absence and presence of DAN, the ANSiscope TM classified and ordered patients among 5 groups: 7 healthy cases, 7 early cases of DAN, 6 late cases, 7 advanced cases and 3 most advanced. Equivalence was found between the HRV and ANSiscope TM assessments as the latter classification was also brought to 2 groups, only distinguishing between absence and presence of DAN. The additional groups of the ANSiscope TM classification seem to provide evidence of early DAN for the first normal category and relativism in the severity of the neuropathy for the second abnormal category. Autonomic scoring did not convey the same diversity between groups as found with the groups formed by the other methods. These findings suggest that correct supine assessment of DAN with sole consideration of R-R time intervals is possible in a little more than 500 heart beats, i.e. with 5 to 8 minutes of ECG recording.