Cardiac implantable devices offer improved recording capabilities. Future developments have for objective to facilitate the home check-up of the patient to reduce the health care expenditure. For this purpose, a challenge deals with the patient ECG check-up from the intracardiac ElectroGraMs (EGM) delivered by the implanted prostheses. In this paper we propose a method to reconstruct the surface ECG from a set of EGM signals, based on a 3D representation of the cardiac electrical activity and Principal Component Analysis (PCA). The results, in the case of sinus rhythm, show a correlation coefficient between the real ECG and the reconstructed ECG of about 0.85.