Patent ID: 8843198

Claim:
A heart stimulator comprising a stimulation control unit; one or more stimulation units; a signal measurement unit; a signal evaluation unit; said one or more stimulation units configured to generate stimulation pulses and to deliver a stimulation pulse to a heart when triggered by said stimulation control unit; said stimulation control unit operatively connected to said one or more stimulation units to control pacing site and/or timing of said stimulation pulses by said one or more stimulation units; said signal measurement unit configured to determine a signal that represents mechanical heart action of said heart; said signal evaluation unit operatively connected to said signal measurement unit and to said stimulation control unit and configured to evaluate said signal that represents mechanical heart action to determine an isovolumic contraction time (IVCT), an isovolumic relaxation time (IVRT), an ejection time (ET) and a filling time (FT) from said signal that represents mechanical heart action; and, said stimulation control unit further configured to control the pacing site and/or the timing of stimulation pulses based on a performance index derived from at least a sum of said isovolumic contraction time (IVCT) and said isovolumic relaxation time (IVRT) divided by a further cardiac cycle time period length of a respective heart cycle; wherein said signal measurement unit is an impedance measurement unit and said signal evaluation unit is an impedance evaluation unit; wherein said impedance measurement unit is configured to determine an impedance signal that represents intracardiac impedance; and, wherein said impedance evaluation unit is configured to evaluate said impedance signal to determine said isovolumic contraction time (IVCT), said isovolumic relaxation time (IVRT), said ejection time (ET) and said filling time (FT) from said impedance signal.