The far-field ECG detection unit records a far-field ECG through the terminals for electrode lines (12,14) placed in right atrium (28) or right ventricle (34) of heart (18). The ECG evaluation unit detects signal features of the ECG associated with an excitation and a contraction of left atrium or ventricle in the recorded ECG. The delay between natural right-atrial event and respective end of right-atrial excitation in far-field ECG is determined in predetermined time period. An independent claim is included for method for determining optimum atrioventricular (AV) conduction time.
