Adaptive refractory period within implantable cardioverter-defibrillator
First Claim
1. An implantable cardioverter-defibrillator (ICD) comprising:
- sensing means for sensing intrinsic cardiac depolarization signals of a patient'"'"'s heart as a function of a first sensitivity setting;
stimulation means for generating electrical stimulation pulses and delivering said pulses to the patient'"'"'s heart in accordance with a prescribed stimulation regime;
refractory means for generating a first refractory period immediately following the generation of an electrical stimulation pulse by said stimulation means or the sensing of intrinsic cardiac depolarization by said sensing means, whichever occurs first, said stimulation means and said sensing means being inhibited during said refractory period; and
means for adaptively adjusting the first refractory period of said refractory means and the first sensitivity setting of said sensing means to optimally detect whether a given sequence of depolarization signals sensed by said sensing means is indicative of one of a plurality of cardiac conditions.
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Abstract
An implantable cardioverter-defibrillator (ICD) adaptively adjusts the refractory period and sensitivity setting of its sensing channel in order to optimally detect depolarization signals indicative of intrinsic cardiac rhythm or tachycardias, or depolarization signals indicative of fibrillation. In one embodiment, the ICD utilizes first and second depolarization signal processing channels, each having first and second refractory periods and first and second sensitivity settings, respectively. The sensitivity settings of the first processing channel are adaptively adjusted to sense normal depolarization signals and tachycardias. The sensitivity settings of the second processing channel are adaptively adjusted to sense fibrillation. Both the first and second refractory periods begin following either a paced depolarization or a sensed depolarization.
83 Citations
22 Claims
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1. An implantable cardioverter-defibrillator (ICD) comprising:
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sensing means for sensing intrinsic cardiac depolarization signals of a patient'"'"'s heart as a function of a first sensitivity setting; stimulation means for generating electrical stimulation pulses and delivering said pulses to the patient'"'"'s heart in accordance with a prescribed stimulation regime; refractory means for generating a first refractory period immediately following the generation of an electrical stimulation pulse by said stimulation means or the sensing of intrinsic cardiac depolarization by said sensing means, whichever occurs first, said stimulation means and said sensing means being inhibited during said refractory period; and means for adaptively adjusting the first refractory period of said refractory means and the first sensitivity setting of said sensing means to optimally detect whether a given sequence of depolarization signals sensed by said sensing means is indicative of one of a plurality of cardiac conditions. - View Dependent Claims (2, 3, 4, 5)
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6. An implantable cardioverter-defibrillator (ICD) comprising:
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stimulation means for generating electrical stimulation pulses and delivering said pulses to a patient'"'"'s heart in accordance with a prescribed stimulation regime; sensing means for sensing intrinsic cardiac depolarization signals of the patient'"'"'s heart, said sensing means including first and second sensing channels having first and second refractory periods, respectively, said first and second refractory periods each beginning following a depolarization of the patient'"'"'s heart, said first and second sensing channels being prevented from sensing any depolarization signals during their respective refractory periods, said first sensing channel being adapted to sense normal depolarizations and tachycardias following said first refractory period as a function of a first sensitivity setting, and said second sensing channel being adapted to sense fibrillation following said second refractory period as a function of a second sensitivity setting; and control means for defining said first and second refractory periods, said first and second sensitivity settings and said prescribed stimulation regime. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. An implantable cardioverter-defibrillator (ICD) comprising:
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sensing means for sensing intrinsic cardiac depolarization signals of a patient'"'"'s heart; stimulation means responsive to said sensing means for generating electrical stimulation pulses and delivering said pulses to the patient'"'"'s heart in accordance with a prescribed stimulation regime; said sensing means including a refractory period that follows a depolarization of the patient'"'"'s heart, said refractory period being divided into segments, with a different sensing option being activated at the conclusion of each segment to optimally sense a prescribed type of cardiac activity. - View Dependent Claims (14, 15)
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16. A method of distinguishing normal cardiac activity, including a tachycardia, from cardiac fibrillation comprising the steps of:
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(a) electrically sensing depolarization signals; (b) simultaneously processing the depolarization signals sensed in step (a) in first and second signal processing channels; (c) making the first signal processing channel refractory during a first refractory period that begins at the beginning of a cardiac cycle, said cardiac cycle beginning following a sensed or paced depolarization, the duration of said first refractory period being selected to prevent sensing of the afterpotential and repolarization; (d) applying a first sensitivity setting to the first signal processing channel that is adapted to sense depolarization signals representative of normal depolarization and tachycardia; (e) recognizing the presence of a normal depolarization if a depolarization signal is sensed by said first signal processing channel subsequent to the termination of said first refractory period and prior to the beginning of the next cardiac cycle when the sensed depolarization signal conforms to normal depolarization criteria, and recognizing the presence of a tachycardia if a depolarization signal is sensed by said first signal processing channel subsequent to the termination of said first refractory period and prior to the beginning of the next cardiac cycle when the sensed depolarization signal conforms to tachycardia criteria; (f) making the second signal processing channel refractory during a second refractory period that begins at the beginning of said cardiac cycle, the duration of said second refractory period being selected to prevent falsely identifying the paced event afterpotential as a second intrinsic depolarization; (g) applying a second sensitivity setting to the second signal processing channel that is adapted to sense depolarization signals representative of fibrillation; and (h) recognizing the presence of fibrillation if a depolarization signal is sensed by said second signal processing channel subsequent to the termination of said second refractory period and before the beginning of the next cardiac cycle when the sensed depolarization signal conforms to prescribed fibrillation criteria. - View Dependent Claims (17, 18, 19, 20)
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21. A method of treating tachycardia and fibrillation with an implantable cardioverter-defibrillator (ICD) device comprising:
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(a) sensing cardiac depolarization signals in a first signal processing channel within said ICD device, said first signal processing channel having a first refractory period and a sensitivity setting adapted to sense cardiac depolarization signals representative of normal cardiac depolarization, including depolarization associated with tachycardia; (b) determining the rate of the cardiac depolarization signals sensed in the first signal processing channel and determining whether such depolarization signals are representative of a normal cardiac rhythm or a tachycardia rhythm; (c) applying a prescribed antitachycardia therapy through said ICD device in response to determining that a tachycardia rhythm is present; (d) sensing cardiac depolarization signals in a second signal processing channel within said ICD, said second signal processing channel having a second refractory period and a sensitivity setting adapted to sense cardiac depolarization signals representative of fibrillation; (e) determining whether the cardiac depolarization signals sensed in the second signal processing channel, in combination with other prescribed criteria, are representative of fibrillation; and (f) applying a prescribed fibrillation therapy through said ICD device in response to determining that a fibrillation is present. - View Dependent Claims (22)
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Specification