US5658317A — Threshold templating for digital AGC

Claim 1

Independent Claim 137 words

A method for automatically adjusting a sensing threshold in a cardioverter/defibrillator, which receives electrical activity of the heart and provides shock pulses in response thereto, the method comprising the steps of: amplifying the electrical activity of the heart; detecting cardiac events representing depolarizations in the electrical activity which exceed a variable sensing threshold; tracking amplitudes of the amplified electrical activity; adjusting the variable sensing threshold to a level proportional to the amplitude of the amplified electrical activity of a current detected cardiac event; and decreasing the variable sensing threshold from said level in discrete steps until the variable sensing threshold is at a low threshold value, wherein said discrete steps are grouped into step groups, wherein each step group decreases the variable sensing threshold by a defined percentage, and wherein each step group comprises multiple discrete steps.

Claim 2

Independent Claim 137 words

A method for automatically adjusting a sensing threshold in a cardioverter/defibrillator, which receives electrical activity of the heart and provides shock pulses in response thereto, the method comprising the steps of: amplifying the electrical activity of the heart; detecting cardiac events representing depolarizations in the electrical activity which exceed a variable sensing threshold; tracking amplitudes of the amplified electrical activity; adjusting the variable sensing threshold to a level proportional to the amplitude of the amplified electrical activity of a current detected cardiac event; and decreasing the variable sensing threshold from said level in discrete steps until the variable sensing threshold is at a low threshold value, wherein said discrete steps are grouped into step groups, wherein each step group decreases the variable sensing threshold by a defined percentage, and wherein each step group comprises multiple discrete steps.

Claim 3

Dependent Claim 20 words

The method of claim 1 wherein the adjusting and decreasing steps achieve a piecewise linear approximation of a geometric progression.

Claim 4

Dependent Claim 14 words

The method of claim 2 wherein the geometric progression is an exponential decay curve.

Claim 5

Dependent Claim 29 words

The method of claim 1 wherein said level is a percentage of a peak value of the amplitude of the amplified electrical activity of the current detected cardiac event.

Claim 6

Dependent Claim 15 words

The method of claim 4 wherein the percentage of the peak value is approximately 75%.

Claim 7

Dependent Claim 33 words

The method of claim 1 wherein the step of adjusting the variable sensing threshold to said level occurs prior to the end of a new sensed refractory period caused by a cardiac event.

Claim 8

Dependent Claim 48 words

The method of claim 1 wherein the method automatically adjusts the sensing threshold in a cardioverter/defibrillator having pacing capability, and wherein the step of adjusting the variable sensing threshold to said level occurs at the end of a paced/shock refractory period resulting from a pace or shock pulse.

Claim 9

Dependent Claim 12 words

The method of claim 1 wherein the defined percentage is approximately 50%.

Claim 10

Dependent Claim 15 words

The method of claim 1 wherein each step group includes at least 4 discrete steps.

Claim 11

Dependent Claim 22 words

The method of claim 1 wherein the decreasing step uses integer math to calculate an amount of drop for a discrete step.

Claim 12

Dependent Claim 35 words

The method of claim 1 further comprising the step of varying a time width of each discrete step based on operating conditions of the cardioverter/defibrillator to control the decay rate of the variable sensing threshold.

Claim 13

Dependent Claim 59 words

The method of claim 11 wherein the method automatically adjusts the sensing threshold in a cardioverter/defibrillator having pacing capability, and wherein the step of varying the time width of each discrete step includes the steps of varying time widths based on bradycardia pacing, tachyarrhythmia sensing, and normal sinus sensing to control the decay rate of the variable sensing threshold.

Claim 14

Dependent Claim 31 words

The method of claim 12 wherein the varying step varies the time width as a function of a bradycardia pacing rate when the cardioverter/defibrillator is operating under the bradycardia pacing conditions.

Claim 15

Dependent Claim 72 words

The method of claim 1 wherein the method automatically adjusts the sensing threshold in a cardioverter/defibrillator having pacing capability, and wherein the method further comprises the steps of: setting the variable sensing threshold after a pace or a shock pulse to a selected relatively high threshold value; and holding the variable sensing threshold at the selected relatively high threshold value through a paced/shock refractory period resulting from the pace or shock pulse.

Claim 16

Independent Claim 167 words

A system for automatically adjusting a sensing threshold in a cardioverter/defibrillator, which receives electrical activity of the heart and provides shock pulses in response thereto, the system comprising: an amplifier for amplifying the electrical activity of the heart; a cardiac depolarization detector for detecting depolarizations in the amplified electrical activity of the heart and providing a detect signal representing a cardiac event indicative of a depolarization when the amplified electrical activity exceeds a variable sensing threshold; and threshold controller for tracking amplitudes of the amplified electrical activity and for adjusting the variable sensing threshold to a level proportional to the amplitude of the amplified electrical activity of a current detected cardiac event and for decreasing the variable sensing threshold from said level in discrete steps until the variable sensing threshold is at a low threshold value, wherein said discrete steps are grouped into step groups, wherein each step group decreases the variable sensing threshold by a defined percentage, and wherein each step group comprises multiple discrete steps.

Claim 17

Independent Claim 167 words

A system for automatically adjusting a sensing threshold in a cardioverter/defibrillator, which receives electrical activity of the heart and provides shock pulses in response thereto, the system comprising: an amplifier for amplifying the electrical activity of the heart; a cardiac depolarization detector for detecting depolarizations in the amplified electrical activity of the heart and providing a detect signal representing a cardiac event indicative of a depolarization when the amplified electrical activity exceeds a variable sensing threshold; and threshold controller for tracking amplitudes of the amplified electrical activity and for adjusting the variable sensing threshold to a level proportional to the amplitude of the amplified electrical activity of a current detected cardiac event and for decreasing the variable sensing threshold from said level in discrete steps until the variable sensing threshold is at a low threshold value, wherein said discrete steps are grouped into step groups, wherein each step group decreases the variable sensing threshold by a defined percentage, and wherein each step group comprises multiple discrete steps.

Claim 18

Dependent Claim 24 words

The system of claim 15 wherein the threshold controller adjusts the variable sensing threshold to achieve a piecewise linear approximation of a geometric progression.

Claim 19

Dependent Claim 14 words

The system of claim 16 wherein the geometric progression is an exponential decay curve.

Claim 20

Dependent Claim 29 words

The system of claim 15 wherein said level is a percentage of a peak value of the amplitude of the amplified electrical activity of the current detected cardiac event.

Claim 21

Dependent Claim 15 words

The system of claim 18 wherein the percentage of the peak value is approximately 75%.

Claim 22

Dependent Claim 32 words

The system of claim 15 wherein the threshold controller adjusts the variable sensing threshold to said level prior to the end of a new sensed refractory period caused by a cardiac event.

Claim 23

Dependent Claim 75 words

The system of claim 15 wherein the cardioverter/defibrillator, in which the system of claim 15 automatically adjusts the sensing threshold, has pacing capability, and wherein the system further comprises means for detecting the end of a paced/shock refractory period resulting from a pace or shock pulse from the cardioverter/defibrillator and, and wherein the threshold controller includes means for adjusting the variable sensing threshold to said level at the detected end of a paced/shock refractory period.

Claim 24

Dependent Claim 12 words

The system of claim 15 wherein the defined percentage is approximately 50%.

Claim 25

Dependent Claim 15 words

The system of claim 15 wherein each step group includes at least 4 discrete steps.

Claim 26

Dependent Claim 21 words

The system of claim 15 wherein the threshold controller calculates an amount of drop for a discrete step using integer math.

Claim 27

Dependent Claim 37 words

The system of claim 15 further comprising a decay rate controller for varying a time width of each discrete step based on operating conditions of the cardioverter/defibrillator to control the decay rate of the variable sensing threshold.

Claim 28

Dependent Claim 46 words

The system of claim 25 wherein the cardioverter/defibrillator, in which the system of claim 25 automatically adjusts the sensing threshold, has pacing capability, and wherein the decay rate controller varies the time widths of each step based on bradycardia pacing, tachyarrhythmia sensing, and normal sinus sensing.

Claim 29

Dependent Claim 32 words

The system of claim 26 wherein the decay rate controller varies the time width as a function of a bradycardia pacing rate when the cardioverter/defibrillator is operating under the bradycardia pacing conditions.

Claim 30

Dependent Claim 72 words

The system of claim 15 wherein the system automatically adjusts the sensing threshold in a cardioverter/defibrillator having pacing capability, and wherein the system further comprises: means for setting the variable sensing threshold after a pace or a shock pulse to a selected relatively high threshold value and for holding the variable sensing threshold at the selected relatively high threshold value through a paced/shock refractory period resulting from the pace or shock pulse.

Claim 31

Independent Claim 150 words

A method for automatically controlling a decay rate of a sensing threshold in a cardioverter/defibrillator with pacing capability, which receives electrical activity of the heart and provides shock pulses and pacing pulses in response thereto, the method comprising the steps of: amplifying the electrical activity of the heart; detecting cardiac events representing depolarizations in the electrical activity which exceed a variable sensing threshold; tracking amplitudes of the amplified electrical activity; adjusting the variable sensing threshold to a level proportional to the amplitude of the amplified electrical activity of a current detected cardiac event; decreasing the variable sensing threshold from said level in discrete steps until the variable sensing threshold is at a low threshold value; and controlling the decay rate of the variable sensing threshold by varying a time width of each discrete step based on operating conditions of the cardioverter/defibrillator including bradycardia pacing, tachyarrhythmia sensing, and normal sinus sensing.

Claim 32

Independent Claim 150 words

A method for automatically controlling a decay rate of a sensing threshold in a cardioverter/defibrillator with pacing capability, which receives electrical activity of the heart and provides shock pulses and pacing pulses in response thereto, the method comprising the steps of: amplifying the electrical activity of the heart; detecting cardiac events representing depolarizations in the electrical activity which exceed a variable sensing threshold; tracking amplitudes of the amplified electrical activity; adjusting the variable sensing threshold to a level proportional to the amplitude of the amplified electrical activity of a current detected cardiac event; decreasing the variable sensing threshold from said level in discrete steps until the variable sensing threshold is at a low threshold value; and controlling the decay rate of the variable sensing threshold by varying a time width of each discrete step based on operating conditions of the cardioverter/defibrillator including bradycardia pacing, tachyarrhythmia sensing, and normal sinus sensing.

Claim 33

Dependent Claim 30 words

The method of claim 29 wherein the controlling step varies the time width as a function of a bradycardia pacing rate when the cardioverter/defibrillator is operating under bradycardia pacing conditions.

Claim 34

Dependent Claim 46 words

The method of claim 30 wherein the controlling step varies the time width under bradycardia pacing conditions based on the time between each pacing pulse, a programmed paced refractory period, and the number of discrete steps to go from said level to the low threshold level.

Claim 35

Dependent Claim 29 words

The method of claim 29 wherein the controlling step varies the time width to produce a relatively fast decay rate when the cardioverter/defibrillator is operating under tachyarrhythmia sensing conditions.

Claim 36

Independent Claim 184 words

A system for automatically controlling a decay rate of a sensing threshold in a cardioverter/defibrillator with pacing capability, which receives electrical activity of the heart and provides shock pulses and pacing pulses in response thereto, the system comprising: an amplifier for amplifying the electrical activity of the heart; a cardiac depolarization detector for detecting depolarizations in the amplified electrical activity of the heart and providing a detect signal representing a cardiac event indicative of a depolarization when the amplified electrical activity exceeds a variable sensing threshold; threshold controller for tracking amplitudes of the amplified electrical activity and for adjusting the variable sensing threshold to a level proportional to the amplitude of the amplified electrical activity of a current detected cardiac event and for decreasing the variable sensing threshold from said level in discrete steps until the variable sensing threshold is at a low threshold value; and decay rate controller for controlling the decay rate of the variable sensing threshold by varying a time width of each discrete step based on operating conditions of the cardioverter/defibrillator including bradycardia pacing, tachyarrhythmia sensing, and normal sinus sensing.

Claim 37

Independent Claim 184 words

A system for automatically controlling a decay rate of a sensing threshold in a cardioverter/defibrillator with pacing capability, which receives electrical activity of the heart and provides shock pulses and pacing pulses in response thereto, the system comprising: an amplifier for amplifying the electrical activity of the heart; a cardiac depolarization detector for detecting depolarizations in the amplified electrical activity of the heart and providing a detect signal representing a cardiac event indicative of a depolarization when the amplified electrical activity exceeds a variable sensing threshold; threshold controller for tracking amplitudes of the amplified electrical activity and for adjusting the variable sensing threshold to a level proportional to the amplitude of the amplified electrical activity of a current detected cardiac event and for decreasing the variable sensing threshold from said level in discrete steps until the variable sensing threshold is at a low threshold value; and decay rate controller for controlling the decay rate of the variable sensing threshold by varying a time width of each discrete step based on operating conditions of the cardioverter/defibrillator including bradycardia pacing, tachyarrhythmia sensing, and normal sinus sensing.

Claim 38

Dependent Claim 31 words

The system of claim 33 wherein the decay rate controller varies the time width as a function of a bradycardia pacing rate when the cardioverter/defibrillator is operating under bradycardia pacing conditions.

Claim 39

Dependent Claim 47 words

The system of claim 34 wherein the decay rate controller varies the time width under bradycardia pacing conditions based on the time between each pacing pulse, a programmed paced refractory period, and the number of discrete steps to go from said level to the low threshold value.

Claim 40

Dependent Claim 30 words

The system of claim 33 wherein the decay rate controller varies the time width to produce a relatively fast decay rate when the cardioverter/defibrillator is operating under tachyarrhythmia sensing conditions.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2000-08-18	2001-02-17	2001-08-19	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2004-08-18	2005-02-17	2005-08-19	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2008-08-18	2009-02-17	2009-08-19	$7700.00	Window Closed / Lapsed

Threshold templating for digital AGC

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