Session S73.4

Cardiac Autonomic Neuropathy Associated Alteration of Sympatho-Vagal Balance through the Tone-Entropy Analysis of Heart Periods

AH Khandoker*, HF Jelinek, M Palaniswami

The University of Melbourne
Melbourne, Australia

Early sub clinical assessment of severity of cardiac autonomic neuropathy (CAN) and intervention are of prime importance for risk stratification and early treatment in preventing sudden death due to silent myocardial infarction. This study presents the usefulness of tone-entropy (T-E) analysis of heart rate variability (HRV) using short term ECG recordings (~20 minutes using Lead II) for screening the degree of severity (mild, definite and severe) of CAN. Tone which represents sympatho-vagal balance was estimated by the ratio of short term and long term HRV. 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. Eight normal subjects without (CAN-) and 16 with CAN (CAN+) participated in this study. Among 16 CAN+ subjects, 7 are early CAN+ (eCAN+), 6 are definite CAN+ (dCAN+) and 3 are severe CAN+ (sCAN+) subjects. Five cardiac autonomic nervous system function tests as described by Ewing were recorded. These measured change in heart rate during lying to standing, deep breathing and Valsalva manoeuvre. Change in blood pressure was measured for lying to standing and hand-grip test. The criterion for no autonomic neuropathy was that all five cardiac autonomic nervous system function tests had to be within the normal range. For early signs of autonomic neuropathy one heart rate test had to be abnormal or two borderline. Definite autonomic neuropathy was defined as two or more heart rate tests were abnormal and for severe disease, two or more heart rate tests had to be abnormal plus one or more of the blood pressure tests. The results showed that the tone was high and the entropy was low in the definite-severe group (T=1.2~2.2 and E=1.0~2.5) compared with the early (T=1.0~1.5 and E=2.5~4.0) and normal (T=0.4~1.0 and E=4.0~5.0) group. When the result was plotted in two-dimensional T-E space, it revealed a curve-linear relation between the tone and entropy. In conclusion, the results suggested that sympatho-vagal balance altered or the vagal predominance was significantly impaired with the severity of CAN in this population.

(Abstract Control Number: 141)