Defibrillation: toward the optimal waveform shape

Heart defibrillation requires exposure of most of the myocardium to a pulsed electric field or potential gradient. The global trend in external defibrillation is undoubtedly the biphasic waveform. If we analyze the defibrillator's international market, we can find around 25 manufacturers and around 15 different biphasic waveforms as it has not yet been established what the optimal waveform for external defibrillation is. Preliminarily, we call it Optimal Transthoracic Defibrillation Waveform, that restores the myocardium normal pumping function with minimal energy applied to the patient. The current state-of-the-art in cardiac electrophysiology allows us, in our point of view, to hope that we may determine what the best way to deliver defibrillation shocks is. There is now scientific consensus that the simple exponential model of cellular membrane potential is a reasonable tool to establish optimal defibrillation parameters, but not with respect to the main parameter of the model, the membrane time constant. In this paper we propose a sketch of a line of research to achieve this goal that is divided into seven main stages: 1. Improving the electrical model of cellular membrane incorporating nonlinearity due to electroporation. 2. Using the improved model to select one (or more) typical waveforms to be evaluated experimentally. 3. Implementing a purely experimental stage to verify empirically the in-vivo waveforms in isolated animal hearts. 4. Extrapolating results to the chest of the animal used. 5. Experimentally adjusting the parameters of optimal external waveform in these animals. 6. Using a mathematical model of the human chest and test animal chest to define preliminarily the optimum external waveform for humans. 7. Clinical validation of the results obtained.