Patent ID: 8755883

Claim:
A system comprising: a transducer configured to measure a heart sound characteristic of a heart; a control circuit configured to: receive the heart sound characteristic; determine a contractility characteristic of the heart using the measured heart sound characteristic; determine a corresponding heart rate indicating how frequently the heart is contracting; alter a pacing rate to determine and store in a memory device a group of (contractility characteristic, heart rate) pairs over a range of heart rates, the group of pairs over the range of heart rates defining a force-frequency relationship for the heart; and determine a slope for at least some of the group of (contractility characteristic, heart rate) pairs based, at least in part, on at least one of a linear regression and a curve fit performed on the at least some of the group of (contractility characteristic, heart rate) pairs; a stimulating circuit coupled to the control circuit, the stimulating circuit configured to deliver, in response to a control signal from the control circuit upon the control circuit determining the slope, stimulating signals based, at least in part, on the previously determined slope for the at least some of the group of (contractility characteristic, heart rate) pairs.