Reconstruction of a surface electrocardiogram from far field signals extracted from an endocardial electrogram in an active medical device is disclosed. The device collects a ventricular EGM signal (EGMV) and an atrial EGM signal (EGMA), and extracts a ventricular far field signal component (FFV) and an atrial far field signal component (FFA). The ventricular and atrial far field signal components are combined to deliver as an output a reconstructed surface electrogram ECG signal (ECGj*). The ventricular and atrial far field signals are respectively extracted from the collected ventricular and atrial EGM signals (FFV, FFA). The reconstruction of the ECG is operated by ventricular (18) and atrial (16) far field signal estimator filters. According to one embodiment, the far field signal estimator filters are linear or nonlinear filters, receiving as input the far field signal components. An adder (20) adds the filtered signals and delivers as output the reconstructed ECG signal (ECGj*).
