Patent ID: 8594788

Claim:
A cardiac stimulator comprising at least one stimulation unit ( 210 ) which is connected or connectable to one or more stimulation electrodes, and which is configured to deliver at least sub-threshold stimulation pulses for cardiac contraction modulation therapy; a cardiac rhythm detection unit ( 220 ); an impedance detection unit ( 230 ) which is connected or connectable to one or more electrodes, and which is configured to detect a voltage or current intensity that occurs as the result of a particular sub-threshold stimulation pulse, and, based thereon, to determine a particular impedance value; an impedance evaluation unit ( 260 ) which is configured to determine at least one value based on ventricular volume, and/or at least one value based on minute ventilation, and/or at least one value based on contraction time; wherein the impedance evaluation unit is further configured to determine an increase in stimulation rate; a control unit ( 240 ) which is connected to the at least one stimulation unit, the cardiac rhythm detection unit, the impedance detection unit, and the impedance evaluation unit wherein the control unit is configured to control a delivery of the sub-threshold stimulation pulses for the cardiac contraction modulation therapy that depend on the at least one value based on ventricular volume, and/or the at least one value based on minute ventilation, and/or the at least one value based on contraction time; wherein the control unit is configured to initiate the cardiac contraction modulation therapy whenever the impedance evaluation unit determines an increase in heart rate; and wherein the control unit is configured to initiate the cardiac contraction modulation therapy whenever the an increase in heart rate is determined, when sinus rhythm has been detected, and when an increase in stimulation rate determined by the impedance evaluation unit lags behind the increase in heart rate.