The Dependence of the Fibrillation Cycle Fraction on which the Defibrillation Pulse is Effective on the Pulse Energy

Based on the data of modeling the response of a cardiomyocyte in a state of simulated fibrillation to rectangular defibrillation pulses, diagrams of the dependence on the energy of the defibrillation pulse of the fraction of the fibrillation cycle were constructed, on which the defibrillation pulse causes a long-term extension of the refractory period of cardiomyocytes (defibrillation completeness index). The constructed diagrams showed that the long-term extension of the refractory period of cardiomyocytes on a part of the fibrillation cycle is achieved at a pulse energy lower than the excitation energy. Presumably, such pulses provide safe low-energy defibrillation. The defibrillation completeness index of safe low-energy defibrillation pulses increases with increasing pulse duration. Guaranteed defibrillation is achieved when the defibrillation pulse causes the extension of the current refractory period of cardiomyocytes to a value of the pulse repetition period of fibrillation and more. The energetically optimal pulse duration of guaranteed defibrillation is approximately 2 times higher than the energetically optimal pulse duration of the excitation. The relative threshold energy of the pulses providing guaranteed defibrillation at pulse durations shorter than the optimum significantly exceeds the values corresponding to the Hoorweg–Weiss–Lapicque law.