Tissue characterization using intracardiac impedances with an implantable lead system
First Claim
1. An implantable device, comprising:
- one or more electrodes for implanting in contact with a bodily tissue;
a pulse generator configured to produce pulses that are applied to the bodily tissue, wherein the pulses are used to measure a physiological parameter and the pulses are applied via the one or more electrodes;
wherein each pulse has a multi-phasic waveform consisting of a number of positive phases and a different number of negative phases, wherein each phase comprises a duration and an amplitude, wherein duration is defined as the width of the phase and amplitude is defined as the length of the phase, and wherein the absolute amplitude of the positive phases is different from the absolute amplitude of the negative phases;
wherein the positive phases and the negative phases transfer a net zero charge through the bodily tissue; and
wherein the pulses are configured to generate a voltage on one or more capacitors of the bodily tissue and/or the implantable device in series with the impedance load of the bodily tissue path that has a zero-volt mean value.
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Accused Products
Abstract
An implantable system acquires intracardiac impedance with an implantable lead system. In one implementation, the system generates frequency-rich, low energy, multi-phasic waveforms that provide a net-zero charge and a net-zero voltage. When applied to bodily tissues, current pulses or voltage pulses having the multi-phasic waveform provide increased specificity and sensitivity in probing tissue. The effects of the applied pulses are sensed as a corresponding waveform. The waveforms of the applied and sensed pulses can be integrated to obtain corresponding area values that represent the current and voltage across a spectrum of frequencies. These areas can be compared to obtain a reliable impedance value for the tissue. Frequency response, phase delay, and response to modulated pulse width can also be measured to determine a relative capacitance of the tissue, indicative of infarcted tissue, blood to tissue ratio, degree of edema, and other physiological parameters.
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Citations
29 Claims
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1. An implantable device, comprising:
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one or more electrodes for implanting in contact with a bodily tissue; a pulse generator configured to produce pulses that are applied to the bodily tissue, wherein the pulses are used to measure a physiological parameter and the pulses are applied via the one or more electrodes; wherein each pulse has a multi-phasic waveform consisting of a number of positive phases and a different number of negative phases, wherein each phase comprises a duration and an amplitude, wherein duration is defined as the width of the phase and amplitude is defined as the length of the phase, and wherein the absolute amplitude of the positive phases is different from the absolute amplitude of the negative phases; wherein the positive phases and the negative phases transfer a net zero charge through the bodily tissue; and wherein the pulses are configured to generate a voltage on one or more capacitors of the bodily tissue and/or the implantable device in series with the impedance load of the bodily tissue path that has a zero-volt mean value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An implantable device, comprising:
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one or more electrodes for implanting in contact with a bodily tissue; a pulse generator to produce pulses to apply to the bodily tissue to measure a physiological parameter, wherein the pulses are applied via the one or more electrodes; wherein each pulse has a multi-phasic waveform consisting of a number of positive phases and a different number of negative phases, wherein each phase comprises a duration and an amplitude, wherein duration is defined as the width of the phase and amplitude is defined as the length of the phase; wherein the number of negative phases is greater than the number of positive phases and the absolute amplitude of the positive phases is greater than the absolute amplitude of the negative phases; wherein the multi-phasic waveform has a duration less than a charging time constant of an electrode-electrolyte interface; wherein the positive phases and the negative phases transfer a net zero charge through the bodily tissue; and wherein the pulses are configured to generate a voltage on one or more capacitors of the tissue and/or the implantable device in series with the impedance load of the bodily tissue that has a zero-volt mean value. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. An implantable device, comprising:
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one or more electrodes for implanting in contact with a bodily tissue; a pulse generator to produce pulses to apply to the bodily tissue to measure a physiological parameter, wherein the pulses are applied via the one or more electrodes; wherein each pulse has a multi-phasic waveform consisting of a number of positive phases and a different number of negative phases; wherein each phase comprises a duration and an amplitude, wherein duration is defined as the width of the phase and amplitude is defined as the length of the phase; wherein the negative phases have an absolute amplitude that is different from the absolute amplitude of the positive phases; wherein the number of negative phases is greater than the number of positive phases and the absolute amplitude of the positive phases is greater than the absolute amplitude of the negative phases; wherein the multi-phasic waveform has a duration less than a charging time constant of an electrode-electrolyte interface; wherein the multi-phasic waveform has null segments between the positive and negative phases, the null segments having a duration sufficient to allow processing circuit of the implantable device to complete processing of information from one phase before the next phase begins; and wherein the positive phases and the negative phases transfer a net zero charge through the bodily tissue; and wherein the positive phases and the negative phases transfer a voltage on capacitors of the bodily tissue and/or the implantable device in series with the impedance load of the bodily tissue path that has a zero-volt mean value. - View Dependent Claims (28, 29)
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Specification