Abstract
The relation between the electrical properties of the heart and the beating rate is essential for the heart functioning. This relation is central when calculating the “corrected QT interval” — an important measure of the risk of potentially lethal arrhythmias. We use the transfer entropy method from information theory to quantitatively study the mutual dynamics of the ventricular action potential duration (the QT interval) and the length of the beat-to-beat (RR) interval. We show that for healthy individuals there is a strong asymmetry in the information transfer: the information flow from RR to QT dominates over the opposite flow (from QT to RR), i.e. QT depends on RR to a larger extent than RR on QT. Moreover, the history of the intervals has a strong effect on the information transfer: at sufficiently long QT history length the information flow asymmetry inverts and the RR influence on QT dynamics weakens. Finally, we demonstrate that the widely used QT correction methods cannot properly capture the changes in the information flows between QT and RR. We conclude that our results obtained through a model-free informational perspective can be utilised to improve and test the QT correction schemes in clinics.
Highlights
It is known that the QT interval of the electrocardiogram (ECG) recordings relates to the ventricular action potential duration and varies with the heart rate (HR)[1,2,3,4]
The resulting average Transfer entropy (TE) distributions for the two information transfers are shown in Fig. 2A
In this work we have considered the transfer of information between coupled RR and QT interval dynamics of healthy individuals
Summary
It is known that the QT interval of the electrocardiogram (ECG) recordings relates to the ventricular action potential duration and varies with the heart rate (HR)[1,2,3,4]. The QT values normalised according to the HR variability are used in assessment of adverse cardiac side effects of drugs in the context of diseases not directly related to the heart, as cancer and others[1,8,9]. Recent evidence demonstrates improvements in the QT correction procedures when a range of the past values of HR is taken into account[4,21,22]. We show that the history length of the past values significantly affects the information flows, and the effect is opposite when QT and RR history lengths are varied independently. We demonstrate that the widely used QT correction formulas are not able to reduce the observed information transfers as stipulated by the correction procedures. We formulate an informational basis of the QT-correction for testing and developing of the QT-correction schemes
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