Patent ID: 8750981

Claim:
A method for use with an implantable medical device for implant within a patient having a lead system including a right ventricular (RV) lead and a right atrial (RA) lead, the method comprising: injecting current between an injection current reference electrode and an RV electrode of the RV lead; measuring values representative of impedance along a vector between a voltage sensing reference electrode and an RA electrode of the RA lead; and controlling at least one device function based on the values representative of impedance; wherein measuring values representative of impedance using the RA electrode includes: measuring impedance (Z RA ) values over cardiac cycles corresponding to at least one respiration cycle while the current is being infected; determining maximum and minimum impedance values (max Z RA and min Z RA ) with each cardiac cycle; and determining difference values (ΔZ RA ) based on the maximum and minimum impedance values (max Z RA min Z RA ); and further including: determining AV and VV pacing delays that achieve a maximum value for AZ RA from among a set of AV and VV delay values.