Background and aims: The existence of non-excitable cells in the myocardium leads\nto the increasing conduction non-uniformity and decreasing myocardial electrical\nconductivity. Slowed myocardial conduction velocity (MCV) believed to enhance the\nprobability of cardiac arryhthmia and alter the cardiac mechanical pumping efficacy,\neven in sinus rhythm. Though several studies on the correlation between MCV and\ncardiac electrical instabilities exist, there has been no study concerning correlation or\ncausality between MCV and cardiac mechanical pumping efficacy, due to the limitation\nin clinical methods to document and evaluate cardiac mechanical responses directly.\nThe goal of this study was to examine quantitatively the cardiac pumping efficacy\nunder various MCV conditions using three-dimensional (3D) electromechanical model\nof canine�s failing ventricle.\nMethods: The electromechanical model used in this study composed of the electrical\nmodel coupled with the mechanical contraction model along with a lumped model of\nthe circulatory system. The electrical model consisted of 241,725 nodes and 1,298,751\nelements of tetrahedral mesh, whereas the mechanical model consisted of 356 nodes\nand 172 elements of hexahedral mesh with Hermite basis. First, we performed the\nelectrical simulation for five different MCV conditions, from 30 to 70 cm/s with 10 cm/s\ninterval during sinus pacing. Then, we compared the cardiac electrical and mechanical\nresponses of each MCV condition, such as the electrical activation time (EAT), pressure,\nvolume, and energy consumption of the myocardium. The energy consumption of\nthe myocardium was calculated by integrating ATP consumption rate of each node in\nmyofilament model.\nResults: The result showed that under higher MCV conditions, the EAT, energy consumption,\nend diastolic and systolic volume are gradually decreased. Meanwhile, the\nsystolic pressure, stroke volume, stroke work, and stroke work to ATP are increased as\nthe MCV values increased. The cardiac functions and performances are more efficient\nunder higher MCV conditions by consuming smaller energy (ATP) while carrying more\nworks.\nConclusion: In conclusion, this study reveals that MCV has strong correlation with the\ncardiac pumping efficacy. The obtained results provide useful information to estimate\nthe effect of MCV on the electro-physiology and hemodynamic responses of the ventricle\nand can be used for further study about arrhythmogeneis and heart failure.
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