1. An implantable medical device for use in delivering cardiac resynchronization therapy to a patient's heart, wherein the cardiac resynchronization therapy is delivered based on a plurality of device parameters, the device comprising: a sensing module configured to monitor at least an intracardiac impedance between at least two electrodes to provide an intracardiac impedance signal; a therapy delivery module configured to deliver cardiac therapy to the patient's heart; and a control module coupled to the sensing module and the therapy delivery module and configured to: deliver cardiac resynchronization therapy to a patient at a plurality of options for at least one of the device parameters; acquire selection data relating to each of the plurality of options for the at least one device parameter for at least one cardiac cycle, wherein acquiring the selection data at each of the plurality of options of the device parameter comprises: acquiring temporal fiducial points associated with at least a part of a systolic portion of at least one cardiac cycle and temporal fiducial points associated with at least a part of a diastolic portion of the at least one cardiac cycle for each of a plurality of electrode vector configurations, acquiring, at each of the plurality of electrode vector configurations and about simultaneously with the acquired fiducial points, an intracardiac impedance signal, extracting measurements from the intracardiac impedance signal for each of the plurality of electrode vector configurations based on the temporal fiducial points and associated with the systolic portion of at least one cardiac cycle and associated with the diastolic portion of the at least one cardiac cycle, and determining selection data for each of the plurality of electrode vector configurations based on the extracted measurements; and use the acquired selection data relating to each of the plurality of options of the device parameter to set one option of the plurality of options for delivery of cardiac resynchronization therapy to the patient's heart.