A method for controlling an adaptive pacing therapy that includes utilizing one or more processors to perform measuring an atrial – ventricular (AV) interval corresponding to an interval between an atrial paced (Ap) event or an atrial sensed (As) event and a sensed ventricular (Vs) event, setting an AV delay based on the AV interval, and measuring an S1 heart sound characteristic of interest (COI) while utilizing the AV delay in connection with delivering a pacing therapy by the IMD. The one or more processors also perform adjusting the AV delay, repeating the measuring, and adjusting to obtain a collection of S1 heart sound COIs and corresponding AV delays, selecting one of the AV delays, that corresponds to a select one of the S1 heart sound COIs, as a resultant AV delay, and managing the pacing therapy, utilized by the IMD, based on the resultant AV delay.