Generally, the disclosure is directed one or more methods or systems of cardiac pacing employing a plurality of left ventricular electrodes. Pacing using a first one of the left ventricular electrodes and measuring activation times at other ones of the left and right ventricular electrodes. Pacing using a second one of the ventricular electrodes and measuring activation times at other ones of the left ventricular electrodes. Employing weighted sums of the measured activation times to measure a fusion index and select one of the left ventricular electrodes for delivery of subsequent pacing pulses based on comparing fusion indices during pacing from different LV electrodes. One or more embodiments use the same fusion index to select an optimal A-V delay by comparing fusion indices during pacing with different A-V delays at resting atrial rates as well as rates above the resting rate.
