Acceleration-sensitive cardiac pacemaker and method of operation

Claim 1

A rate adaptive pacemaker comprising: means for sensing a physiological parameter wherein the sensing means provides an output signal corresponding to the sensed physiological parameter; means for providing a sensor determined interval from the output signal coupled to the sensing means and comprising means for performing analog signal processing and means for performing digital signal processing; means for determining an actual pacing interval; means for determining a pacing rate coupled to the means for providing the sensor determined interval and the means for determining the actual pacing interval wherein the pacing rate is a function of both the sensor determined interval and the actual pacing interval; means for generating pacing pulses at said pacing rate; and wherein the means for performing analog signal processing compromises: (a) means connected to receive the output signal for chopping and modulating the output signal and providing a first modulated signal; (b) first means for amplifying coupled to the chopping and modulating means to receive the first modulated signal and provide a first amplified output; (c) first means for filtering having a first input coupled to receive the first amplified output and providing a first filtered output; (d) second means for amplifying coupled to the first filtered output and providing a second amplified output; (e) demodulator means for demodulating having an input coupled to the second amplified output and providing a demodulated output; (f) second means for filtering having an input coupled to the demodulated output and providing a second filtered output; (g) third means for amplifying having a first input also coupled to the second filtered output and providing a third amplified output; and (h) means for converting analog signals to digital signals having first and second inputs coupled to the third amplified output.

Claim 12

A method for operating a cardiac pacemaker implanted in a patient's body comprising the steps of: (a) sensing acceleration of the patient's body; (b) providing an acceleration output signal proportional to the sensed acceleration; (c) band limiting and filtering the acceleration output signal to provide a filtered accelerator output; (d) digitizing the filtered accelerator output; (e) sampling the filtered accelerator output and summing the samples over a cardiac cycle to provide an accumulated sum; (f) determining a sensor rectified average proportional to the accumulated sum divided by the number of samples in a cardiac cycle; (g) determining a sensor determined interval proportional to the sensor rectified average; (h) determining a pacing rate based in part on the sensor determined interval; and (i) generating pulses at the pacing rate.

Claim 13

A method for operating a cardiac pacemaker implanted in a patient's body comprising the steps of: (a) sensing acceleration of the patient's body; (b) providing an acceleration output signal proportional to the sensed acceleration; (c) band limiting and filtering the acceleration output signal to provide a filtered accelerator output; (d) digitizing the filtered accelerator output; (e) sampling the filtered accelerator output and summing the samples over a cardiac cycle to provide an accumulated sum; (f) determining a sensor rectified average proportional to the accumulated sum divided by the number of samples in a cardiac cycle; (g) determining a sensor determined interval proportional to the sensor rectified average; (h) determining a pacing rate based in part on the sensor determined interval; and (i) generating pulses at the pacing rate.