An implantable medical device and associated method to determine an optimal control parameter setting for controlling a cardiac therapy that includes a therapy delivery module to deliver cardiac pacing signals at a plurality of pacing rates, and an admittance measurement module to determine admittance signals associated with each of the plurality of pacing rates. A control unit determines metrics of hemodynamic performance corresponding to each of the plurality of pacing rates in response to the determined admittance signals, identifies pacing rates of the plurality of pacing rates as rejected rates in response to the determined metrics of hemodynamic performance, and determines a pacing rate of the plurality of pacing rates as an optimal rate for delivering the cardiac therapy in response to the identified pacing rates.