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Automatic cardiac capture threshold determination system and method

  • US 4,708,142 A
  • Filed: 05/28/1985
  • Issued: 11/24/1987
  • Est. Priority Date: 05/28/1985
  • Status: Expired due to Term
First Claim
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1. A capture threshold determination system for automatically determining the capture threshold energy level of applied pacing pulses required to reliably stimulate cardiac events in a patient heart, comprising:

  • pulse generating means responsive to an applied energy level control signal for developing pacing pulses over a predetermined range of energy levels for application to the heart during successive reoccurring intervals;

    capture detection means for connection to the heart for detecting cardiac events stimulated during each successive itnerval in response to the pacing pulses generated during that interval, and providing a capture detection signal indicative thereof;

    first register means for storing a lower limit pulse energy level and providing an output indicative thereof;

    second register means for storing an upper limit pulse energy level and providing an output indicative thereof;

    computing means coupled to and responsive to the outputs of said first and second register means for computing the average of said pulse energy levels stored in said first and second register means and providing an output indicative thereof;

    pulse amplitude control means coupled to and responsive during an initial one of said intervals to the output of one of said register means, and during subsequent intervals coupled to and responsive to the output of said computing means for producing an energy level control signal for application to said pulse generating means to cause said generating means to produce pacing pulses at the energy level of said one register during said initial interval, and at the average energy levels computed by said computing means during subsequent intervals;

    transfer means responsive to said capture detection signal upon completion of each interval for transferring the then existing average pulse energy level indicated by the output of said computing means to said first register means in the event of non-capture during that interval, and to said second register means in the event of capture during that interval, whereby the energy level of said pacing pulses as determined by said energy level control signal approaches the capture threshold level with successive intervals; and

    output circuit means coupled to and responsive to the outputs of said register means for providing an output control signal upon the difference between said outputs falling below a predetermined threshold level to indicate generation of pacing pulses at the capture threshold level.

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