Patent ID: 8639328

Claim:
An implantable medical device for use in delivering therapy to a patient's heart comprising: a sensing module configured to monitor an impedance between at least two electrodes proximate the patient's heart to provide an 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: determine an E-wave portion representative of an early diastolic filling phase during a cardiac cycle based on the impedance signal, determine an A-wave portion representative of a late diastolic filling phase during the cardiac cycle based on the impedance signal, deliver cardiac therapy to the patient based upon one or more characteristics associated with at least one of the E-wave portion and the A-wave portion, the one or more characteristics comprising an area of the E-wave portion, determine a maximum peak impedance for the cardiac cycle, and determine an earliest trough of the impedance signal following the maximum peak impedance as a start of the E-wave portion.