Short-term forecasting of life-threatening arrhythmias with finite time Lyapunov exponents

Ventricular tachycardia or fibrillation (VT/VF) are fatal cardiac arrhythmias which are the main triggering factors for a sudden cardiac death. The objective of this study was to find early signs of VT/VF in patients with an implantable cardioverter-defibrillator (ICD) to enable a prediction for an improved antiarrhythmic therapy. Therefore, we studied the interbeat intervals of 17 chronic heart failure ICD patients with and without (control) VT/VF event. To detect typical signs of an immediately following malignant arrhythmia we calculated HRV parameters from time and frequency domain as well as the averaged finite time Lyapunov exponent and the Shannon entropy of the finite time Lyapunov exponents distribution. The results of this study show that neither the time nor the frequency domain parameters show significant differences between the VT/VF and the control time series. However, the averaged finite time Lyapunov exponents and the Shannon entropy discriminate significantly both groups (p<0.01 resp. p<0.04). These findings could be of importance in algorithms for next generation ICDs to improve the diagnostics and therapy of VT/VF.