Abstract: Systems and methods are provided for estimating a patient's ventricular defibrillation threshold (VDFT). Stimulation pulses, which are of at least three different energy levels up to 2 Joules, are delivered to the patient's right ventricle during a window defined between an R-wave and a vulnerable period that follows the R-wave. Voltage potentials, induced in response to the delivered RV stimulation pulses, are measured at a location of the patient's left ventricle (LV) where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest. Potential gradients are computed using the measured voltage potentials. The patient's VDFT can then be estimated by estimating, based on the computed potential gradients, the RV stimulation energy level that would be required to achieve a minimum acceptable potential gradient at the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest.