A system for combined electrophysiological mapping and ablation of a patient's heart, comprising: an external electrophysiological mapping system, EMS, comprising: (a) a plurality of surface electrical sensing electrodes configured to acquire surface electrocardiogram, ECG, signals from at least portions of a patient's torso; (b) a data acquisition device operably connected to the surface electrical sensing electrodes and configured to condition the ECG signals provided thereby; (c) at least one non-transitory computer readable medium storing instructions executable by at least one processor to perform a method for receiving and processing the ECG signals to provide on a display or a monitor a real-time or near-real-time voxel-model-derived visual representation or image of at least a portion of the patient's heart during a combined electrophysiological mapping and cardiac ablation procedure carried out on the patient; a cardiac ablation system comprising a catheter configured for insertion inside the heart of the patient, the catheter comprising a distal end comprising a tissue ablation device configured to controllably form scar tissue on the patient's endocardium during the combined electrophysiological mapping and cardiac ablation procedure; wherein the EMS is further programmed and configured to: process the ECG signals during the combined electrophysiological mapping and cardiac ablation procedure to produce on the display or the monitor the real-time or near-real-time voxel-model-derived visual representation of one or more locations on the patient's heart where at least one scar has been created by the ablation device during the combined electrophysiological mapping and cardiac ablation procedure, the visual representation including maps of electrical activity of the patient's heart; and wherein the system is further configured to: monitor the patient's heart electrical activity while the cardiac ablation is carried out, monitoring electrophysiological changes in the heart by comparing the maps of electrical activity over time; wherein the system is further configured to: generate a reference map of activation isochrones; after receipt of a trigger signal from the cardiac ablation system indicative of the start of the ablation, monitoring ablation-related changes between a current updated map of activation isochrones and a reference map of activation isochrones in a repeat loop, said changes being related to scar formation; and send a respective trigger signal to the cardiac ablation system after a difference between a current updated map of activation isochrones and a reference map of activation isochrones has crossed a threshold value, the respective trigger signal being indicative that a change related to scar formation has been detected. an external electrophysiological mapping system, EMS, comprising: (a) a plurality of surface electrical sensing electrodes configured to acquire surface electrocardiogram, ECG, signals from at least portions of a patient's torso; (b) a data acquisition device operably connected to the surface electrical sensing electrodes and configured to condition the ECG signals provided thereby; (c) at least one non-transitory computer readable medium storing instructions executable by at least one processor to perform a method for receiving and processing the ECG signals to provide on a display or a monitor a real-time or near-real-time voxel-model-derived visual representation or image of at least a portion of the patient's heart during a combined electrophysiological mapping and cardiac ablation procedure carried out on the patient; a cardiac ablation system comprising a catheter configured for insertion inside the heart of the patient, the catheter comprising a distal end comprising a tissue ablation device configured to controllably form scar tissue on the patient's endocardium during the combined electrophysiological mapping and cardiac ablation procedure; generate a reference map of activation isochrones; after receipt of a trigger signal from the cardiac ablation system indicative of the start of the ablation, monitoring ablation-related changes between a current updated map of activation isochrones and a reference map of activation isochrones in a repeat loop, said changes being related to scar formation; and send a respective trigger signal to the cardiac ablation system after a difference between a current updated map of activation isochrones and a reference map of activation isochrones has crossed a threshold value, the respective trigger signal being indicative that a change related to scar formation has been detected.