Patent ID: 8295927

Claim:
A machine-assisted method comprising: measuring a first impedance, during at least a portion of a cardiac cycle, between a first electrode associated with a first ventricle of a heart and a reference electrode; measuring a second impedance, during at least the portion of the cardiac cycle, between a second electrode associated with a second ventricle of the heart, in which the second ventricle is different from the first ventricle, and the same or a different reference electrode; measuring a phase difference between the first and second impedances; and automatically adjusting in a closed loop manner, using the measured phase difference as an error signal, a cardiac resynchronization therapy parameter that synchronizes left and right ventricular heart contractions, the automatically adjusting tending to reduce the phase difference during a subsequent cardiac cycle, wherein the automatically adjusting comprises: when the measured phase difference shows the second impedance leading the first impedance in phase by more than a first threshold value, then lengthening an atrioventricular (AV) delay; and when the measured phase difference shows the first impedance leading the second impedance in phase by more than a second threshold value, then shortening the AV delay.