A computer-implemented method of non-invasively planning a patient-specific ablation cardiac procedure, comprising: receiving three-dimensional in-vivo imaging data of a patient's heart; segmenting said three-dimensional imaging data into a first plurality of regions of normal tissue and a second plurality of regions of remodeled tissue based on said three-dimensional imaging data; assigning different electrophysiological properties to said first and second pluralities of tissue_regions; simulating at least one of electrophysiological or electromechanical activity of at least a portion of said patient's heart using said segmented and assigned three-dimensional imaging data; and planning said patient-specific cardiac procedure based on said simulating, wherein said simulating at least one of electrophysiological or electromechanical activity of at least said portion of said patient's heart comprises constructing a geometric model of said at least said portion of said patient's heart, said geometric model including said first plurality of regions of normal tissue and second plurality of regions of remodeled tissue determined for said patient using said segmented three-dimensional imaging data, wherein said simulating at least one of electrophysiological or electromechanical activity of at least said portion of said patient's heart further comprises estimating tissue fiber orientations in said geometric model of said at least said portion of said patient's heart, and wherein said cardiac procedure is for providing a preselected alteration of at least one of electrophysiological or electromechanical behavior of said patient's heart, preferably (i) wherein said three-dimensional imaging data is at least one of magnetic resonance imaging, computed tomography, positron emission tomography, ultrasound, or nuclear tracer three-dimensional imaging data, or (ii) further comprising: receiving additional patient-specific data that includes at least one of biopsy data, electrocardiogram data, recorded data from an implantable device, or invasive electrical mapping data, wherein said simulating uses said additional patient-specific data. receiving three-dimensional in-vivo imaging data of a patient's heart; segmenting said three-dimensional imaging data into a first plurality of regions of normal tissue and a second plurality of regions of remodeled tissue based on said three-dimensional imaging data; assigning different electrophysiological properties to said first and second pluralities of tissue_regions; simulating at least one of electrophysiological or electromechanical activity of at least a portion of said patient's heart using said segmented and assigned three-dimensional imaging data; and planning said patient-specific cardiac procedure based on said simulating, wherein said simulating at least one of electrophysiological or electromechanical activity of at least said portion of said patient's heart comprises constructing a geometric model of said at least said portion of said patient's heart, said geometric model including said first plurality of regions of normal tissue and second plurality of regions of remodeled tissue determined for said patient using said segmented three-dimensional imaging data, wherein said simulating at least one of electrophysiological or electromechanical activity of at least said portion of said patient's heart further comprises estimating tissue fiber orientations in said geometric model of said at least said portion of said patient's heart, and wherein said cardiac procedure is for providing a preselected alteration of at least one of electrophysiological or electromechanical behavior of said patient's heart, preferably (i) wherein said three-dimensional imaging data is at least one of magnetic resonance imaging, computed tomography, positron emission tomography, ultrasound, or nuclear tracer three-dimensional imaging data, or (ii) further comprising: receiving additional patient-specific data that includes at least one of biopsy data, electrocardiogram data, recorded data from an implantable device, or invasive electrical mapping data, wherein said simulating uses said additional patient-specific data. (i) wherein said three-dimensional imaging data is at least one of magnetic resonance imaging, computed tomography, positron emission tomography, ultrasound, or nuclear tracer three-dimensional imaging data, or (ii) further comprising: receiving additional patient-specific data that includes at least one of biopsy data, electrocardiogram data, recorded data from an implantable device, or invasive electrical mapping data, wherein said simulating uses said additional patient-specific data. receiving additional patient-specific data that includes at least one of biopsy data, electrocardiogram data, recorded data from an implantable device, or invasive electrical mapping data, wherein said simulating uses said additional patient-specific data.