A medical electrical lead is disclosed that is adapted for placement in the coronary sinus, or a branch vein thereof. The lead includes a first and second pace/sense electrode. A selection mechanism is provided to select either the first or the second electrode for use as a cathode, with the other electrode being selected as the anode. According to another aspect of the invention, a high-voltage coil electrode may be provided between the first and second electrodes. The coil electrode may be electrically coupled to the anode to increase the shadow area of the coil electrode.