Heart rate variability and QT dispersion in a cohort of diabetes patients.

Heart rate is dependent on a cycle of depolarization and repolarization of the atria and ventricles that is regulated by intrinsic and extrinsic factors. Inhomogeneity in ventricular repolarization, measured as QT interval dispersion (QTd) is likely to lead to arrhythmia. The role of the autonomic nervous system in the development of this inhomogeneity is still uncertain. Autonomic regulation can be measured using the tone-entropy algorithm, which indicates inter-beat interval variation.When a sliding cut-off for QTd was used only the control group had a significant association between QTd and both tone and entropy. This finding suggests that for certain levels of ventricular inhomogeneity, autonomic control becomes more dissociated from intra-beta variation measured by QTd. This may be an early sign of potentially fatal arrhythmia.