Rate adaptive pacemaker

Claim 2

A rate-adaptive pacemaker comprising: an impedance measuring device for measuring a waveform over time of an intracardial impedance over at least a predetermined portion of one cardiac cycle; an impedance processing device for obtaining an impedance value from the waveform over time, the impedance processing device including: an integrator stage for determining a time integral of the impedance waveform over the predetermined portion of the cardiac cycle as a primary impedance value; an integral value memory coupled to the integrator stage for storing one reference integral value at a time, ascertained in at least one preceding cardiac cycle; and an arithmetic unit having inputs connected to outputs of the integrator stage and the integral value memory for calculating a secondary impedance value from the respective primary impedance value and from the reference integral value in accordance with a predetermined arithmetical equation; and a rate determining device, downstream of the impedance processing device and controlled by a sequence controller, for determining an adaptive stimulation rate on the basis of the secondary impedance value.

Claim 3

The rate-adaptive pacemaker of claim 1 , wherein the arithmetic unit includes a subtraction stage for forming a differential value between the primary impedance value and the reference integral value, the differential value constituting the secondary impedance value.

Claim 4

The rate-adaptive pacemaker of claim 1 , wherein the impedance processing device further includes a read only memory, connected at least indirectly to a control input of the integrator stage, for storing one of (a) limits of the predetermined portion of the cardiac cycle and (b) a location of impedance detection points on a time scale at which impedance values are sampled within the predetermined portion of the cardiac cycle.

Claim 5

The rate-adaptive pacemaker of claim 1 , wherein the impedance processing device further includes a mean value forming stage including an input connected to the integral value memory and and an output connected to the arithmetic unit for forming a sliding mean value from preceding impedance measurements as a reference integral value.

Claim 6

The rate-adaptive pacemaker of claim 1 , and further including a unipolar ventricle electrode connected to an input of the measuring device for being switched as both a sensing and stimulating electrode.

Claim 7

A rate-adaptive pacemaker comprising: an impedance measuring device for measuring a waveform over time of an intracardial impedance over at least a predetermined portion of one cardiac cycle; an impedance processing device for obtaining an impedance value from the waveform over time, the impedance processing device including an integrator stage for determining a time integral of the impedance waveform over the predetermined portion of the cardiac cycle as a primary impedance value and a read only memory, connected at least indirectly to a control input of the integrator stage, for storing one of (a) limits of the predetermined portion of the cardiac cycle and (b) a location of impedance detection points on a time scale at which impedance values are sampled within the predetermined portion of the cardiac cycle; and a rate determining device, downstream of the impedance processing device and controlled by a sequence controller for determining an adaptive stimulation rate using the primary impedance value.

Claim 8

A rate-adaptive pacemaker comprising: an impedance measuring device for measuring a waveform over time of an intracardial impedance over at least a predetermined portion of one cardiac cycle; an impedance processing device for obtaining an impedance value from the waveform over time, the impedance processing device including an integrator stage for determining a time integral of the impedance waveform over the predetermined portion of the cardiac cycle as a primary impedance value and a read only memory, connected at least indirectly to a control input of the integrator stage, for storing one of (a) limits of the predetermined portion of the cardiac cycle and (b) a location of impedance detection points on a time scale at which impedance values are sampled within the predetermined portion of the cardiac cycle; and a rate determining device, downstream of the impedance processing device and controlled by a sequence controller for determining an adaptive stimulation rate using the primary impedance value.

Claim 9

The rate-adaptive pacemaker of claim 6 , wherein the impedance processing device further includes a read only memory, connected at least indirectly to a control input of the integrator stage, for storing one of (a) limits of the predetermined portion of the cardiac cycle and (b) a location of impedance detection points on a time scale at which impedance values are sampled within the predetermined portion of the cardiac cycle.

Claim 10

The rate-adaptive pacemaker of claim 6 , wherein the rate determining device includes a differential member having a data input for the primary impedance value.

Claim 11

The rate-adaptive pacemaker of claim 6 , and further including a unipolar ventricle electrode connected to an input of the measuring device for being switched as both a sensing and stimulating electrode.

Claim 12

A rate-adaptive pacemaker comprising: an impedance measuring device for measuring a waveform over time of an intracardial impedance over at least a predetermined portion of one cardiac cycle; an impedance processing device for obtaining an impedance value from the waveform over time, the impedance processing device including an integrator stage for determining a time integral of the impedance waveform over the predetermined portion of the cardiac cycle as a primary impedance value; a differential member including a data input for receiving the impedance value at an output of the integrator stage and including a control input for setting a time constant of the differential member; a digital motion sensor for an activity variable having an output coupled to the control input of differential stage, the output of the sensor assuming a first state when a patient is resting and assuming a second state when the patient is in motion so that the time constant of the differential member is set to a differential time (T D ) value that is substantially lower when the patient is resting than when the patient is in motion; and a rate determining device, downstream of the impedance processing device and controlled by a sequence controller, for determining an adaptive stimulation rate using the primary impedance value.

Claim 13

A rate-adaptive pacemaker comprising: an impedance measuring device for measuring a waveform over time of an intracardial impedance over at least a predetermined portion of one cardiac cycle; an impedance processing device for obtaining an impedance value from the waveform over time, the impedance processing device including an integrator stage for determining a time integral of the impedance waveform over the predetermined portion of the cardiac cycle as a primary impedance value; a differential member including a data input for receiving the impedance value at an output of the integrator stage and including a control input for setting a time constant of the differential member; a digital motion sensor for an activity variable having an output coupled to the control input of differential stage, the output of the sensor assuming a first state when a patient is resting and assuming a second state when the patient is in motion so that the time constant of the differential member is set to a differential time (T D ) value that is substantially lower when the patient is resting than when the patient is in motion; and a rate determining device, downstream of the impedance processing device and controlled by a sequence controller, for determining an adaptive stimulation rate using the primary impedance value.

Claim 14

The rate-adaptive pacemaker of claim 9 , wherein the impedance processing device further includes a read only memory, connected at least indirectly to a control input of the integrator stage, for storing one of (a) limits of the predetermined portion of the cardiac cycle and (b) a location of impedance detection points on a time scale at which impedance values are sampled within the predetermined portion of the cardiac cycle.

Claim 15

The rate-adaptive pacemaker of claim 10 , and further including a unipolar ventricle electrode connected to an input of the measuring device for being switched as both a sensing and stimulating electrode.