A modification of the mathematical model of the shape and fibre direction field of the cardiac left ventricle is presented. The model was developed based on the idea of nested spiral surfaces. The ventricle is composed of surfaces which model myocardial layers. Each layer is filled with curves corresponding to myocardial fibers. The tangents to these curves form the myofibre direction field. With the model left ventricle, a modified spherical-like coordinate system is linked where ventricular boundaries are coordinate surfaces. The model is personified based on echocardiographic, computed tomography or magnetic resonance imaging data. For that, four-chamber and two-chamber echocardiography views or sections along the long axis of the left ventricle from the said tomographic data in several positions are approximated with model profile. To construct a 3-D model, we then interpolate model parameters by periodic cubic splines and the vector field of the tangents to the model fibres is calculated. For the model verification, we used diffusion-tensor magnetic resonance imaging data of the human heart.