1. A process for processing signals representative of cardiac myocardium depolarization potentials, said signals being signals collected by a plurality of endocardial electrodes of an active implantable medical device such as an implantable pacemaker, device for resynchronization, cardioversion and/or defibrillation, comprising: a) acquiring a plurality of endocardial electrogram signals (EGM) through a plurality of endocardial or intravascular derivations, defined based upon said endocardial electrodes; b) calculating, through a combination of the endocardial electrogram signals (EGM) acquired at step a), a corresponding endocardial vectogram (VGM); d) estimating, based upon the endocardial vectogram calculated at step b), a reconstructed surface vectocardiogram (VCG reconstructed ); and e) calculating surface electrocardiogram signals (ECG) corresponding to said reconstructed surface vectocardiogram (VCG reconstructed ).