The present invention relates to monitoring septal wall motion of the atrial and/or ventricular chambers of a heart for optimizing cardiac pacing intervals based on signals derived from the monitored wall motion. At least one lead of medical device is equipped with a motion sensor adapted to couple to septal tissue. The device receives and may post-process (e.g., suitably filter, rectify and/or integrate) motion signals to determine acceleration, velocity and/or displacement. During pacing interval optimization the wall motion is measured for those pacing intervals and the pacing interval setting(s) that produce minimal wall motion for chronic therapy delivery. In addition, methods for periodically determining whether to cease or resume delivery of a bi-ventricular pacing therapy to a patient that may have experienced beneficial reverse remodeling of the heart.