Left ventricular vortex plays a critical role in blood ejection from left ventricle (LV) to aorta. In spite of several parameters for evaluating LV vortex, there still remain fundamental questions to categorize LV vortex. Here, we propose the Reynolds number (Re), based on mitral valvular velocity and diameter, as an evaluation index for LV vortex strength and verify this by using a computational method. For this purpose, we implement an integrative model of heart and blood flow simulating sequential events of heart from cellular electric excitation-contraction to 3D tissue contraction, and eventually blood hemodynamics in LV. Simulation of fluid structure interation (FSI) in this study couples cardiac electromechanical model presented in our previous study [1] with the code of computational fluid dyanamics [2]. Remeshing algorithm is used to account for the mesh vairtion according to vave and ventricular wall motions. First, we verify the present method by comparing computed results with clinical observations. Then, we investigate the effect of Re variation on the strength LV vortex. Simulated results show that the strength LV vortex can be classified by Re, indicating Re is a useful index for diagonizing hemodynamic dysfunction of LV.