It is a widely practiced method to utilize high-intensity electric fields (E) for the purpose of reversing ventricular fibrillation (VF) through a procedure known as defibrillation. This method, however, carries the risk of potentially damaging cardiac tissue, thereby highlighting the necessity for refining defibrillation protocols to enhance their efficacy. With this consideration in mind, we employed the COMSOL Multiphysics software to develop a computer model designed to simulate the stimulation of a murine heart using various pulse widths. Our primary objective was to observe the stimulated area of the heart when altering the duration of the stimulation pulse, all while keeping the intensity of the applied E constant. We observed that in order to stimulate a minimum of 75% of the heart with at least 4.5 V/cm, pulses with a duration of up to 1 ms need an E intensity that can be up to 71% higher when compared to pulses lasting at least 3 ms. This shows the significant role played by the duration of the applied stimulus in facilitating the stimulation of a broader area of the heart, all without the need to increase the intensity of the stimulus. In essence, this work underscores the critical importance of optimizing the duration of stimulation pulses in defibrillation protocols, as it directly influences the efficiency of the procedure while mitigating the potential risks associated with high-intensity E application.