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A.V. Moskalenko*), A.V. Rusakov*), Yu. E. Elkin**)
Ventricular arrhythmias are life-dangerous disorders of the heart activity. Despite considerable progress in recent years, the pharmacological treating of patients with ventricular fibrillation and polymorphic ventricular tachycardia remain little effective. In accordance with multicentered investigations (ESVEM, CASCADE etc.), the treating with antiarrhythmic drugs of all classes leads to the positive results in 58,5% of cases. Such low treating efficiency can be caused by poor differentiation of ventricular arrhythmias. It is expected that the more detailed diagnosis is made the more correct treating is prescribed.
The most widely used clinical tools for assessing arrhythmias is the body surface ECG. For detailed quantitative description of polymorphic ventricular arrhythmias to be introduced, we proposed a new technique for ECG analysis referred to as ANI-method [Biophysics 46(2):313-323].
The ANI-method was tested with the ECGs obtained both in physiological experiments [Biophysics 42(2):491-496] and in numeric simulations [Biophysics 48(2):303-312].
The ANI-method maps ECG fragment to two real indices. The indices give evaluation of polymorphism, which is one of the qualitative ECG characteristics of cardiac arrhythmia degree. One of the indices characterizes the average evaluation of ECG segments unlikeness inside the fragment and the other is its variation. An indices sequence for successive ECG fragments draws a trajectory in the index space. The compared ECG segments correspond to similar intervals of adjacent cardiac cycles. See Fig.1
In the index space, the regions corresponded to ECG with different polymorphism were picked out. On the base of peer review, the partial order was introduced for ECG polymorphism. It is induced the partial order in the index space. As result new detailed quantitative description of polymorphic ECGs was introduced. See Fig.2
It was found out that the trajectories of ECGs obtained in the physiological experiments usually groups in certain regions of the index space and are absent in the other regions. See Fig.4
The trajectories of ECGs obtained in the numeric simulations have significantly different location. But ECGs of both types have no evident visual differences. It is interesting that numeric ECGs are less "determinate" with respect to the indices than the physiological ECGs. Physiological and biophysical mechanisms of the phenomena described here have no explanation yet. See Fig.5
In this study we have shown that a novel technique for ECG analysis referred to as ANI-method could provide cardiologists with sensitive clinical tools for ventricular life-dangerous arrhythmias assessment. The estimates of ECG variation in this study reveal some unexpected details of ventricular arrhythmias dynamics, which probably will be useful for diagnostics of heart disorders.
This study has demonstrated the possibilities of ANI-method for quantitative distinction of ECGs during life-dangerous ventricular arrhythmias. The many of the natural phenomena found are not understood because of complexity of heart activity during ventricular arrhythmias.
As regimes of circulation of excitation waves on myocardium is strongly determined by the state of membrane ionic channels [Chaos, Solitons and Fractals 1995;5:513-526], further development of ANI-method is suggested to turn the technique into new effective noninvasive procedure for evaluation of myocardial state.
Further work will also aim at the study how reentrant and focal arrhythmias could be distinguished from their ECGs.
This work has been supported by the Civil Research Development Foundation through the award of CRDF-RB0-676 (1999-2000) and CRDF-RB1-102 (1996-1998) grants.