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Method and apparatus for automatic pacing threshold determination

  • US 5,713,933 A
  • Filed: 11/30/1994
  • Issued: 02/03/1998
  • Est. Priority Date: 11/30/1994
  • Status: Expired due to Term
First Claim
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1. A method of determining a patient'"'"'s cardiac stimulation threshold, comprising the steps of:

  • (a) defining a capture detect window of predetermined duration and initiating said window at a predefined time following delivery of any stimulating pulse to a patient'"'"'s heart, during which a cardiac impedance signal is sensed and measured;

    (b) delivering to a patient'"'"'s heart at least one control stimulating pulse having sufficient energy predetermined to ensure cardiac capture;

    (c) deriving at least one control value which characterizes the morphology of said cardiac impedance signal sensed and measured during said predefined capture detect window following delivery of said at least one stimulating pulse in step (b);

    (d) delivering to said patient'"'"'s heart at least one series of stimulating pulses having successively lower energy levels;

    (e) for each one pulse of said series of stimulating pulses delivered in step (d) above, deriving at least one test value corresponding to said each one pulse, wherein said at least one corresponding test value characterizes the morphology of said cardiac impedance signal signal sensed and measured during said capture detect window following said each one of said series of stimulating pulses;

    (f) for each test value derived in step (e), determining whether a difference between said each test value and said control value lies within a predetermined range;

    (g) for each one pulse of said series of stimulating pulses delivered in step (d), determining whether a cardiac electrical event was sensed during said capture detect window following said each one of said series of stimulating pulses;

    (h) discontinuing said at least one series of stimulating pulses of successively lower energy levels when any one of said determinations in step (f) indicates that said difference between said test value for a given one pulse of said series of stimulating pulses and said control value does not lie within said predetermined range and therefore that capture was not achieved by said given one pulse of said series of stimulating pulses;

    (i) discontinuing said at least one series of stimulating pulses of successively lower energy levels when any one of said determinations in step (g) indicates a cardiac electrical event reflecting a loss of capture was sensed during said capture detect window following a given one pulse of said series of stimulating pulses; and

    (j) identifying said patient'"'"'s pacing threshold as being at least a predetermined incremental amount greater than the energy level of the last in said series of test stimulation pulses delivered prior to discontinuance in step (h) or step (l).

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