Characteristic Energy Method for Evaluation of Monopolar Defibrillation Pulse Efficiency

Abstract

IntroductionAccording to the leading theory, efficacious defibril lation requires electric pulse polarization of cell mem branes in the entire myocardium or most of it. The polar ization should be at a certain voltage [1]. Because the effect of electric pulse current on the patient's body tis sues can cause damage (particularly with high patient thoracic cavity resistance), it is desirable that defibrilla tion is performed at minimal pulse energy. The optimum criterion of threshold defibrillation pulse is minimal ener gy required for polarization of myocardium cell mem branes.There is a method of evaluation of defibrillation pulse efficiency based on the Weiss-Lapique model. This model was elaborated in the early XX century [1]. This model makes no difference between pulses with the same mean current value. It follows from this model that trian gular ascending pulses and triangular descending pulses of the same pulse time should have the same threshold amplitude of defibrillation current and the same thresh old defibrillation energy. However, it was shown experi mentally that a triangular ascending pulse required lower defibrillation energy (lower current amplitude) compared to a triangular descending pulse [2,3].The characteristic energy method suggested in this work provides theoretical assessment of monopolar defib rillation pulse efficiency. This method allows pulses of dif ferent shape to be tested and optimal defibrillation pulse time to be determined for elucidation of this difference.For bipolar and multiphase defibrillation pulses, this method provides separate evaluation of individual pulse phases. The efficiency of the first pulse phase is of cardi nal importance. For example, in a bipolar quasi sinu soidal defibrillation pulse (Gurvich-Venin pulse) the optimal ratio of the first to second phase is 1 : 0.55 [4 8].The first pulse phase contains 77% of the energy. A trape zoidal bipolar defibrillation pulses provide close ratio of pulse phases.Defibrillation pulses of arbitrary shape are presently available [9 16]. The results obtained in this work could be used for determination of optimal defibrillation pulse shape in experiments with laboratory animals. Characteristic Energy MethodThe characteristic energy method is based on a model of defibrillation pulse effect on myocardium cell membrane ( Fig. 1) [17,18]. According to this model, a defibrillation pulse is applied to resistor R s (resistance of the patient's thoracic cavity) and to a model myocardium cell membrane response to external stimulation. This model consists of a series of resistor R m and capacitor C m . Time constant τ m determines cell membrane reaction to the defibrillation pulse: Fig. 1. Model of defibrillation pulse effect on myocardium cell membrane. Defibrillator Myocardium cell membrane

Construction of Energy-Optimal Smooth Monophasic Defibrillation Pulse Waveforms Using Cardiomyocyte Membrane Model

“…The present and previous our papers have focused on monophasic and first phase biphasic pulses of different waveforms (morphology) and duration which releases at least 70% -80% of the pulse energy on the heart region during defibrillation [12] [14]. The results of this study suggest that it is impossible to achieve significant increase in the energy efficiency of monophasic defibrillation pulses by using the Luo-Rudy cardiomyocyte membrane model.…”

Study of the Impact of Rectangular Current Pulses on the Ten Tusscher-Panfilov Model of Human Ventricular Myocyte

“…A number of previous theoretical studies have studied the effect on the cardiomyocyte membrane model of a single excitation pulse [1][2][3][4][5][6][7][8]. However, a study of the impact of an electrical defibrillation pulse on cardiomyocytes should consider the fact that during fibrillation a cardiomyocyte is not in a resting state and is subject to the impact of an abnormally frequent parasitic excitation wave while myocardial cardiomyocytes are in different phases of the excitation cycle.…”