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Automatic sensitivity adjust for cardiac pacemakers

  • US 5,374,282 A
  • Filed: 10/31/1991
  • Issued: 12/20/1994
  • Est. Priority Date: 10/31/1991
  • Status: Expired due to Term
First Claim
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1. A pacemaker, comprising:

  • a pulse generator, for producing cardiac pacing pulses;

    a sense amplifier for receiving and amplifying electrical cardiac signals, said sense amplifier having a sensitivity threshold adjustable by means of sensitivity control input signals, and said sense amplifier producing a sensed event output pulse whenever said electrical cardiac signals exceed said adjustable sensitivity threshold;

    a pacing lead, coupled to a patient'"'"'s heart, for conveying said cardiac pacing pulses from said pulse generator to the heart, and for conveying said electrical cardiac signals from the heart to said sense amplifier;

    a pressure sensor for producing a pressure sensor output signal;

    peak sense and threshold measurement means, for detecting a voltage peak of said pressure sensor output signal and for determining whether said voltage peak exceeds a predetermined pressure threshold, said peak sense and threshold measurement means producing a pressure event indicator signal when said voltage peak exceeds said predetermined pressure threshold;

    sensitivity adjustment circuitry, receiving said sensed event output pulses and said pressure event indicator signals, for generating said sensitivity control input signals;

    wherein said sensitivity adjustment circuitry comprises timing means defining an auto-sensitivity timing period;

    and wherein said sensitivity adjustment circuitry further comprises counting means for determining a count of sensed event output pulses and a count of pressure event indicator signals occurring during said auto-sensitivity timing period, said sensitivity adjustment circuitry issuing sensitivity control input signals upon expiration of said auto-sensitivity timing period;

    said sensitivity control input signals causing said sensitivity threshold to be increased unless said count of pressure event indicator signals exceeds said count of sensed event output pulses by more than a predetermined margin, and otherwise causing said sensitivity threshold to be decreased.

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