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Method and apparatus for rate-responsive cardiac pacing

  • US 5,562,711 A
  • Filed: 11/30/1994
  • Issued: 10/08/1996
  • Est. Priority Date: 11/30/1994
  • Status: Expired due to Term
First Claim
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1. A cardiac pacemaker, comprising:

  • a stimulating pulse generator for producing a cardiac stimulating pulse in response to a trigger signal;

    a first sensing circuit in said pacemaker for detecting cardiac electrical signals;

    a cardiac pacing lead having at least one conductor and having at least one electrode in electrical contact at one end thereof to a patient'"'"'s heart, for conducting said cardiac stimulating pulse from said pulse generator to said patient'"'"'s heart and for conducting cardiac electrical signals to said first sensing circuit;

    an impedance sensing circuit, coupled to said lead, for generating an electrical impedance signal whose level reflects said patient'"'"'s minute ventilation level;

    an activity sensing circuit adapted to generate an electrical activity signal whose level reflects said patient'"'"'s activity level;

    a rate determination circuit, coupled to receive impedance level signals from said impedance sensing circuit and to receive said activity level signals from said activity sensing circuit, said rate determination circuit periodically deriving a new rate value as a function of a current rate value and of said activity signal level and said impedance signal level, said new rate value being within a rate range defined by predetermined lower and upper limits, said activity signal level having greater influence than said impedance signal on said rate value derivation when said current rate value is in a lower segment of said rate range, and said impedance signal having greater influence than said activity signal on said rate value derivation when said current rate value is in an upper segment of said rate range;

    a control circuit, coupled to said pulse generator, said first sensing circuit, and said rate determination circuit, for generating a sequence of said trigger signals at a rate which varies in accordance with said periodically derived new rate value.

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