Patent ID: 8131356

Claim:
An implantable medical device comprising: a housing for the implantable device sized for implantation in a chest region of a patient and comprising a housing electrode; a left ventricular lead port into which a proximal end of a lead is connectable, the lead having first and second conductors that are insulated from one another and that extend from the proximal end of the lead to corresponding first and second electrodes positioned near a distal end of the lead; an electrical impedance measurement circuit electrically connected to the left ventricular lead port and to the housing electrode, the circuit adapted to inject current between the first lead electrode and the housing electrode, and adapted to measure a voltage potential between the second lead electrode and the housing electrode, the voltage potential created by the current injection; and a control module adapted to calculate a series of multiple impedance value samples over a period of time, each impedance value sample being calculated based on a measurement of the voltage potential and the current injection that created the voltage potential, and to select and store in memory of the implantable device baseline impedance value samples from the series of multiple samples, wherein the baseline impedance value samples are selected based on the selected sample corresponding to a predetermined moment of both the cardiac cycle and the respiration cycle of the patient.