A method and device for determining an optimal lower rate and adjusting the programmed lower pacing rate to the optimal rate that includes monitoring a parameter in response to therapy delivered at a first rate during a first time period to generate first parameter data, and determining whether the therapy was delivered for a predetermined portion of the first time period. The parameter is monitored in response to the therapy delivered at a next rate during a next time period to generate next parameter data, and a determination is made as to whether the therapy was delivered for a predetermined portion of the next time period. A metric corresponding to the first parameter data is determined to generate a first parameter metric, and corresponding to the next parameter data to generate a next parameter metric used for determining an optimal therapy delivery rate.