Importance Of Shock Phase Duration And Voltage Of Negative Shock Phase In Biphasic - Sequential Defibrillation In Pigs

Abstract

Previous studies have found that sequential pulse or biphasic pulse shocks are superior to monophasic shocks for defibrillation. Combining these two modalities may further enhance defibrillation efficacy. The importance of shock phase duration and voltage of the negative phase for combined biphasic-sequential pulse shocks were determined in random order in two experiments using anaesthetized pigs. The first experiment compared defibrillation efficacy using sequential pulse alone to biphasic shocks alone and biphasic-sequential shocks, with the leading edge voltages of the negative phase, being 35 % and 50% of the peak voltage of the positive phase for the biphasic shocks. The second experiment determined the effects of different phase durations of combined shocks: a) 3-7, 3-7 ms; b) 5-5, 5-5 ms; c) 7-3, 7-3 ms and d) 10, 10 ms; e) 4, 4 ms. Defibrillation thresholds were significantly lower for biphasic-sequential in both 35 % and 50 % groups compared to sequential and biphasic alone. Significantly lower energies were obtained with the 5-5, 5-5 ms and the 7-3, 7-3 ms phase durations compared to either of the other phase durations. In conclusion, the present mlts suggest that lower voltage negative phase may reduce the energy requirements necessary for defibrillation. In addition, when pulse duration is the same the phase duration is an important contributor to the decrease in the energy required for defibrillation. Incorporation of a biphasicsequential pulse with an equal or longer first phase followed by shorter phase duration as well as lower voltage negative phase may be important in the design of future generations of implantable devices.