Rate responsive cardiac pacemaker with peak impedance detection for rate control
First Claim
1. An implantable cardiac stimulation apparatus comprisinga hermetically sealed container, said container having therein a battery, andcontrol circuitry powered by said battery, said control circuitry comprising means for producing an output to stimulate a patient'"'"'s heart;
- means for measuring impedance within the patient'"'"'s body and producing a first signal correlated to said impedance;
means for producing a first derivative of said first signal;
means for detecting a zero-crossing of said first derivative;
means for timing an interval from said output to said zero-crossing; and
means for controlling said means for producing said output as a function of said interval.
1 Assignment
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Accused Products
Abstract
An implantable, rate responsive pacemaker, sensitive to impedance changes in the heart, wherein the cardiac pacing rate and maximum cardiac pacing rate, or either of them, are adjusted as a function of an interval between either the administration of a pacing pulse or the detection of the R-wave and the occurrence of a maximum detected impedance, called the intercept interval. Because an intercept point in derivative of the impedance curve is detected, the apparatus and method are insensitive to electrode characteristics, electrode movement, body posture or other factors which could affect the magnitude of the detected impedance. The information contained in the intercept interval can also be combined with other sensed or calculated information to set the desired rates.
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Citations
16 Claims
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1. An implantable cardiac stimulation apparatus comprising
a hermetically sealed container, said container having therein a battery, and control circuitry powered by said battery, said control circuitry comprising means for producing an output to stimulate a patient'"'"'s heart; - means for measuring impedance within the patient'"'"'s body and producing a first signal correlated to said impedance;
means for producing a first derivative of said first signal;
means for detecting a zero-crossing of said first derivative;
means for timing an interval from said output to said zero-crossing; and
means for controlling said means for producing said output as a function of said interval. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- means for measuring impedance within the patient'"'"'s body and producing a first signal correlated to said impedance;
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9. A method for controlling an implantable cardiac stimulation apparatus comprising
producing a cardiac stimulating output; -
measuring impedance within the patient'"'"'s body; producing a first derivative of said measured impedance; detecting a zero-crossing of said first derivative; timing an interval from said output to said zero-crossing; and producing a subsequent cardiac stimulating output as a function of said interval. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification