Cardiac Resynchronisation Therapy (CRT) causes changes in cardiac anatomy, electrophysiology and mechanics of the heart after 3–6 months of treatment. Multi-pole pacing (MPP) and multi-vein pacing (MVP) are new technologies that offer the ability to change the location of the pacing site post implant, however, the long term benefits of shifting the left ventricle (LV) pacing site are still uncertain. A personalised biophysical electromechanical model of a patient's heart was developed from MRI, echocardiogram, ECG and pressure catheter recordings, before and after sustained CRT treatment. Simulations of biventricular pacing of the heart were performed for 49 pacing sites across the LV free wall, in the model of the patient prior to- and after sustained pacing. The optimal region for LV pacing was determined by the acute haemodynamic response (AHR). After sustained CRT treatment the heart remodels and the models predict that the optimal region for pacing the LV would expand by 46% after this remodeling. The expansion in the optimal LV pacing region after remodeling predicts that if LV lead location was placed within the optimal region prior to CRT treatment, it will remain within the optimal region after sustained pacing.