Identification of high-risk patients for sudden cardiac death (SCD) remains difficult. Non-invasive markers evaluating changes in heart rate and ventricular repolarisation (VR) have been developed to stratify this risk. Most studies using VR analysis rely on static analysis of the QT interval which is poorly reproducible and heart rate dependent. Dynamic VR analysis assesses QT interval modification according to RR duration of the precedent heart cycle. This relation is characterized by the linear regression QT/RR (y = ax+b) thus defined by its slope (a) and the value of the QT for a virtual null RR cycle (b). Analysis can be made for QTa (apex) and QTe (end). In healthy subjects, the difference of QT/RR slopes observed between day and night highly suggest that the QT/RR slope is influenced by the autonomic tone. The QT/RR slope is also influenced by clinical, physiological, pharmacological and various diseases associated with an increased risk of SCD. The prognostic value of the QT/RR slope for SCD has been demonstrated after myocardial infarction and in chronic heart failure. These results suggest that QT dynamicity is a promising tool able to identify patients at risk of SCD.
Keywords: QT/RR, QT dynamicity, ventricular repolarization, sudden cardiac death, Autonomic system, Ventricular arrhythmias
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