Threshold templating for digital AGC
First Claim
1. 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.
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Abstract
A system and method automatically adjusts a sensing threshold in a cardioverter/defibrillator which receives electrical activity of the heart and delivers shock pulses in response thereto. An amplifier amplifies the electrical activity. A detection circuit detects depolarizations in the amplified electrical activity and provides a detect signal representing a cardiac event indicative of a depolarization when the amplified electrical activity exceeds a variable sensing threshold. Digital template generation circuitry responds quickly to track amplitudes of the electrical activity and to set the variable sensing threshold to a level proportional to a peak value of the amplitude of the amplified electrical activity and then decreases the variable sensing threshold from the level in discrete steps until the variable sensing threshold is at a low threshold value. The discrete steps are grouped into step groups. Each step group decreases the variable sensing threshold by a defined percentage.
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Citations
36 Claims
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1. 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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. 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:
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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. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. 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:
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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. - View Dependent Claims (30, 31, 32)
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33. 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:
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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. - View Dependent Claims (34, 35, 36)
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Specification