THE USAGE OF THE CHAOS THEORY IN RESEARCH OF ELECTROPHYSIOLOGY IN VENTRICULAR FIBRILLATION
Introduction: Ventricular fibrillation (VF) is the most common reason for a circulatory arrest and sudden cardiac death; reentrant ventricular tachycardia (VT) is the most common sustained arrhythmia leading to VF. The theory of chaos is particularly attractive in the analysis of VF because it describes the phenomena in a comprehensive way. The analysed frequency of a spectrum of electrical phenomena during VF allows to isolate periodical regular components, undermining thereby the opinion about the randomness of constituents of the process under observation. The aim of the carried out tests was to verify the hypothesis assuming a “chaotic” characteristics of electrical phenomena in the heart muscle during VF and VT.
Methods: Fifteen rabbits were anesthetized with midazolam (0,75 mg/kg/h). Cardiac arrest during VF was induced with three methods - an alternating current with the use of transesophageal electrode (n-5, 12 V, 50 Hz), intravenous application of epinephrine (n-5, 0,001/kg), or calcium chloratum (n-5, 0,1/kg). Defibrillation shock was performed 5 minutes after cardiac arrest. When defibrillation was unsuccessful, cardiopulmonary resuscitation was performed. ECG data was analyzed using a numerical technique, based on discrete signal wavelet packet analysis.
Results: It was shown how a transition from a non-chaotic state to a chaotic state manifests itself in the magnitude and distribution of system response wavelet expansion coefficients. The analysis of the electrocardiographic signals during VT proved the existence of a continuous Fourier spectrum of the investigated signal. It was found that the signal packet wavelet expansion coefficients occur only for low frequency ranges of the signal. The results show that the investigated VT electrocardiographic signals have characteristics corresponding to chaotic states. It was further shown that the Fourier spectrum of the VT electrocardiographic signal has the dominant features of discrete distributions, and the signal wavelet packet expansion coefficients occur in all the frequency ranges of the signal.
Conclusions: Results show that standard ECG registration not allows to analyze developed chaotic process in myocardium during VF, however it is possible to find chaotic characteristic in VT.