Digital AGC using separate gain control and threshold templating
First Claim
1. A method of automatically adjusting a sensing threshold in a cardioverter/defibrillator which receives electrical activity of a heart and provides shock pulses in response thereto, the method comprising the steps of:
- amplifying the electrical activity according to a variable gain;
detecting cardiac events representing depolarizations in the electrical activity which exceed a variable sensing threshold;
acquiring amplitudes of the amplified electrical activity;
adjusting the variable sensing threshold to a level proportional to an acquired amplitude of the amplified electrical activity of a current detected cardiac event;
decreasing the variable sensing threshold from the level in discrete steps until the variable sensing threshold is at a low threshold value; and
adjusting the variable gain based on amplitudes of the amplified electrical activity of at least three detected cardiac events.
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Accused Products
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 according to a variable gain. 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. Slow gain control circuitry adjusts the variable gain in discrete steps based on stored peak history information representing peak values of the amplified electrical activity. Template generation circuitry responds quickly 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.
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Citations
58 Claims
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1. A method of automatically adjusting a sensing threshold in a cardioverter/defibrillator which receives electrical activity of a heart and provides shock pulses in response thereto, the method comprising the steps of:
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amplifying the electrical activity according to a variable gain; detecting cardiac events representing depolarizations in the electrical activity which exceed a variable sensing threshold; acquiring amplitudes of the amplified electrical activity; adjusting the variable sensing threshold to a level proportional to an acquired amplitude of the amplified electrical activity of a current detected cardiac event; decreasing the variable sensing threshold from the level in discrete steps until the variable sensing threshold is at a low threshold value; and adjusting the variable gain based on amplitudes of the amplified electrical activity of at least three detected cardiac events. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A system for automatically adjusting a sensing threshold in a cardioverter/defibrillator having a pulse circuit for generating shock pulses based on a detect signal representing cardiac events indicated in electrical activity of a heart, the system comprising:
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an amplifier for amplifying the electrical activity of the heart according to a variable gain; a cardiac depolarization detector for detecting depolarizations in the amplified electrical activity of the heart and providing the detect signal representing a cardiac event indicative of a depolarization when the amplified electrical activity exceeds a variable sensing threshold; gain controller for adjusting the variable gain of the amplifier based on amplitudes of the amplified electrical activity of at least three detected cardiac events; and threshold controller for acquiring amplitudes of the amplified electrical activity and for adjusting the variable sensing threshold to a level proportional to the acquired 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. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
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58. A cardiac rhythm management device for generating electrical pulses and coupleable to an electrode for sensing electrical activity of a heart and carrying the electrical pulses to the heart, the device comprising:
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an input/output terminal connectable to the electrode to receive the sensed electrical activity of the heart from the electrode and to provide the electrical pulses to the electrode; a sense amplifier coupled to the input/output terminal and amplifying the electrical activity of the heart according to a variable gain; a cardiac depolarization detector coupled to the sense amplifier and 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; gain controller coupled to the sense amplifier and the cardiac depolarization detector to adjust the variable gain of the sense amplifier based on amplitudes of the amplified electrical activity of at least three detected cardiac events; and threshold controller coupled to the sense amplifier and the cardiac depolarization detector to acquire amplitudes of the amplified electrical activity and to adjust the variable sensing threshold to a level proportional to the acquired amplitude of the amplified electrical activity of a current detected cardiac event and to decrease the variable sensing threshold from the level in discrete steps until the variable sensing threshold is at a low threshold value; and a pulse circuit coupled to the input/output terminal and the cardiac depolarization detector for generating the electrical pulses based on the detect signal.
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Specification