Complexity changes in instantaneous heart rate prior to ventricular fibrillation in patients with implantable defibrillator

The objective of this study was to determine complexity changes of instantaneous heart rate prior to malignant tachy-arrhythmic events. Are these possible changes detectable by means of an implantable defibrillator? R-R intervals of the internal defibrillator memory were analyzed by means of linear and non-linear techniques. The non-linear analysis revealed a significant decline of the slope of the correlation integral prior to the malignant tachycardia. In contrast, the linear parameter standard deviation of the R-R series, a measure of heart rate variability, did not show any significant change. Thus methods of early detection of vulnerable periods and possible new strategies in prevention of malignant events with implantable anti-tachy-arrhythmic devices may benefit from non-linear analysis of R-R intervals