In this work we present a coupled electromechanical model of the heart for patient-specific simulations, and in particular cardiac resynchronisation therapy. To this end, we propose a fast fully autonomous and flexible pipeline to generate and optimise the data required to run the mechanical simulation. After the meshing of the biventricular segmentation image and the construction of the associated fibres arrangement, we compute the electrical potential propagation in the myocardial tissue from selected onset points on the endocardium. We generate a 12-lead electrocardiogram corresponding to the latter activation map by extrapolating the electrical potential on a virtual torso. This electrical activation is coupled to a mechanical model, featuring a small set of interpretable parameters. We also propose an efficient algorithm to optimise the model parameters, based on patient data. The whole pipeline including a cardiac cycle is computed in 30 minutes, enabling to use this digital twin for diagnosis and therapy planning.