Systems according to the invention employ an acceleration sensor to characterize displacement and vibrational LV motion, and uses this motion data to characterize the different phases of the LV cycle for analyzing LV function. Systems may identify a target pacing region or regions in the LV or RV using the acceleration sensor by localizing regions of late onset of motion relative to the QRS, or isovolumic contraction, or mitral valve closure, or by pacing of target regions and measuring LV function in response to pacing. Systems further provide an implantable or non-implantable acceleration sensor device for measuring LV motion and characterizing LV function. An implantable myocardial acceleration sensing system (“IAD”) includes at least one acceleration sensor, a data acquisition and processing device, and an electromagnetic, e.g., RF, communication device. The IAD may be integrated into the pacing lead of a CRT device and can operate independently of the CRT IPG.