This document discusses, among other things, systems and methods to determine a response curve between received cardiac electrical information from a subject, such as a time of a P wave, and received cardiac acceleration information of the subject, such as a time of a first heart sound (S1) or a second heart sound (S2), to a set of stimulation signals provided to the subject at different AVD intervals. In certain examples, one or more cardiac resynchronization therapy (CRT) parameters can be determined for the subject using the determined response curve.