An implantable medical device that includes a first elongated lead body having an outer surface and an opening along the outer surface, a sensor positioned along the lead body and configured to receive acoustic signals through the opening of the first lead body and generate an electrical signal representative of sounds produced at a targeted location along a patient's cardiovascular system. A therapy delivery module is capable of delivering a cardiac therapy via predetermined electrodes of a plurality of electrodes, and a processor is configured to detect a cardiac event in response to the sensed cardiac electrical signals, determine a plurality of time intervals between the electrical signals and acoustic signals, determine a correlation between the electrical signals and the acoustic signals, and control the therapy delivery module to deliver therapy in response to the determined correlation.