Information theory based evaluation of interactions between RR and QT intervals in the normal and people with high risk for cardiac arrhythmias

This project is purposed to evaluate autonomic nerve system (ANS) through the coupling of RR interval (RRI) and QT interval (QTI) using information theory as well as Spearman correlation coefficient (Spearman CC). And the possible changes of their coupling in ESRD (those with high risk for cardiac arrhythmias and sudden cardiac death). The Holter data with 189 Normal and 43 ESRD were provided by THEW. 5min episodes at rest were selected both in daytime and on night. Let predictive information (PI) measure the information that carried by QTI can be predicted by the knowledge of the past of itself and RRI. The information storage and internal information of QT variability (QTV) were determined respectively as the self-entropy of the QTI series and the self-entropy of the series conditioned to the knowledge of RRI. The information transfer and cross information from RRI to QTV were assessed as the coupling of them two. PI on night (PI„) was significantly smaller in ESRD compared with that in Normal (0.258±0.137 vs 0.322±0.142). However, no significant difference was found between PI in daytime (PI d ) in Normal and in ESRD. And the decreased PI n led the loss of PI diurnal variation in ESRD(0.275±0.170 vs 0.258±0.137). While in Normal, there were significant difference between PI d and PI n (0.223±0.102 vs 0.322±0.142). Since the decreased PI n in ESRD was mostly due to the changes in transfer entropy, meaning the reduction of RRI and QTI coupling. At the same time, the decreased conditioned self-entropy of QTI revealed less predictability of the past QTI to its present. All the above reflected the loss of sympathetic inhibition in ESRD, especially on night when the vagal activity is dominant and sympathetic activity should be withdrawn. The information theory based approach is not only feasible for assessing ANS activity through the coupling of RRI and QTI, but also provides a measure to characterize QTV related to HRV as well as those unrelated to HRVfrom nonlinear view.