Identification of pacing site

An implantable medical device comprising:

• a first ventricular lead having multiple electrodes;
• a second ventricular lead having at least one electrode, said first ventricular lead is constructed to be implantable in or in connection with a first ventricle of a heart and said second ventricular lead is constructed to be implantable in or in connection with a second ventricle of said heart;
• a signal generator coupled to said first and second ventricular leads and configured to generate an electric signal applicable over two neighboring electrodes of said first ventricular lead or over an electrode of said first ventricular lead and a case electrode of said implantable medical device;
• a signal sensing unit configured to sense, for each candidate pair of neighboring electrodes of said first ventricular lead or for each candidate electrode of said first ventricular lead, a resulting electric signal over said candidate pair of neighboring electrodes or over said candidate electrode and said case electrode;
• an impedance processor configured to determine, for each candidate pair or for each candidate electrode, an impedance signal representative of local myocardial contraction at a site of said first ventricle associated with said candidate pair or said candidate electrode based on said electric signal and said resulting electric signal sensed by said signal sensing unit for said candidate pair or said candidate electrode;
• a time processor configured to determine, for each candidate pair or each candidate electrode, a time difference between start of contraction within said second ventricle and a timing of said local myocardial contraction at said site associated with said candidate pair or said candidate electrode based on said impedance signal;
• and
• an electrode selector configured to select a pacing electrode for said first ventricle corresponding to one of the electrodes of the candidate pair having largest time difference or corresponding to the candidate electrode having largest time difference.