A method and system are provided to determine a defibrillation threshold (DFT). The method and system determine local conduction (LC) information for at least one LV region of the heart, and designate a ULV pacing electrode, where the ULV pacing electrode is located proximate to a region of the heart for which the LC information satisfies a predetermined LC characteristic. The method and system pace the heart from the ULV pacing electrode such that the region of the heart, for which the LC information satisfies the predetermined LC characteristic, becomes re-polarized early in a repolarization phase following pacing of the heart. The method and system deliver a ULV shock, obtain upper limit of vulnerability (ULV) information based on a heart response to the ULV shock and obtain a DFT based on the ULV information.
