Cardiac disorders result mainly from defects in cardiac structure or failure to generate and regulate electrical impulses. Knowledge of the structure, motion patterns, local deformation, and associated electrical activation patterns of the heart is necessary for precise diagnosis and treatment. Electrical and mechanical performance of the heart is strongly influenced by the anisotropic nature of myocardial tissue. Diffusion-encoded MR imaging provides in vivo myocardial fiber track information that can be used for precise simulation of cardiac conduction and contraction. We propose a method that incorporates such fiber track information with a physics-based deformable model to realistically simulate cardiac contraction and subsequent relaxation. The simulation aims to reproduce the myocardial deformation during the heartbeat. The system allows interactive visualization of dynamic 3-D heart structures during the cardiac cycle. In procedures such as catheter ablation, the interactive 4-D model provides updated anatomy and physiology of the patient's heart simultaneously, and can be used to guide the procedure for efficient targeting of the treatment regions.