1. A method for estimating patient-specific cardiac electrical properties from medical image data and non-invasive electrocardiography measurements of a patient, comprising: generating a patient-specific anatomical heart model and a patient-specific anatomical torso model from medical image data of a patient and an electrical coupling model between the patient-specific anatomical heart model and the patient-specific anatomical torso model; generating a mechanical activation time map of the heart from a dynamic cardiac image sequence of the patient; identifying a line of block from the mechanical activation time map; and estimating spatially varying patient-specific cardiac electrical parameters for the patient by: simulating cardiac electrophysiology over time at a plurality of nodes in the patient-specific anatomical heart model using a computational cardiac electrophysiology model, and adjusting at least one cardiac electrical parameter of the computational cardiac electrophysiology model based on the mechanical activation time map, the non-invasive electrocardiography measurements of the patient, the simulated cardiac electrophysiology, and the line of block identified from the mechanical activation time map.