Patent ID: 7062326

Claim:
A cardiac pacemaker system comprising: (a) an implantable lead adaptable for sensing intracardiac electrical signals and delivering high and low energy pacing therapy, wherein the lead includes two or more electrodes at various distances from each other; (b) a sensing module for detecting the intracardiac electrical signals; (c) an impedance circuit for recording intracardia impedance signals; (d) a microprocessor for computing an intracardiac impedance-derived parameter based on the impedance signals wherein the intracardiac impedance-derived parameter includes a ratio of a first value related to an area encompassed by a portion of an impedance waveform and a second value related to an area encompassed by a whole impedance waveform corresponding to a single cardiac cycle; (e) a pacing controller for adjusting a pacing therapy delivered by the system according to the impedance-derived parameter; (f) a pacing module for delivering pacing signals to the implantable lead according to the pacing therapy; (g) a sensor for generating electrical signals associated with activity related to cardiac demand; and (h) a second sensing module for receiving the activity related electrical signals from the sensor, wherein the pacing controller uses the intracardiac impedance-derived parameter to modify pacing therapies suggested by the sensor activity-related signals.