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 positive phases and negative phases;
wherein each phase comprises a duration and an amplitude, wherein duration is defined as the width of the phase and the amplitude is defined as the length of the phase, further wherein the alternating positive and negative phases have different absolute amplitudes; and
wherein each pulse has a duration less than a charging time constant of an electrode-electrolyte interface between the electrode and the bodily tissue.
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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
32 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 positive phases and negative phases; wherein each phase comprises a duration and an amplitude, wherein duration is defined as the width of the phase and the amplitude is defined as the length of the phase, further wherein the alternating positive and negative phases have different absolute amplitudes; and wherein each pulse has a duration less than a charging time constant of an electrode-electrolyte interface between the electrode and the bodily tissue. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A system, comprising:
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means for delivering a multi-phasic pulse waveform to bodily tissue via one or more electrodes, wherein the pulse waveform has a duration less than the a charging time constant of an electrode-electrolyte interface between one of the electrodes and the bodily tissue, and wherein the multi-phasic waveform consists of positive phases and negative phases, wherein each phase comprises a duration and an amplitude, wherein duration is defined as the width of the phase and the amplitude is defined as the length of the phase, further wherein the alternating positive and negative phases have different absolute amplitudes; means for sensing a response waveform resulting from application of the pulse waveform in the bodily tissue; and means for determining a characteristic of the bodily tissue based on the sensed response waveform. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method, comprising:
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delivering a multi-phasic pulse waveform to bodily tissue via one or more electrodes, wherein the pulse waveform has a duration less than a charging time constant of an electrode-electrolyte interface between one of the electrodes and the bodily tissue, and wherein the multi-phasic waveform consists of positive phases and negative phases, wherein each phase comprises a duration and an amplitude, wherein duration is defined as the width of the phase and the amplitude is defined as the length of the phase, further wherein the alternating positive and negative phases have different absolute amplitudes; sensing a response waveform resulting from application of the pulse waveform in the bodily tissue; and determining a characteristic of the bodily tissue based on the sensed response waveform. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32)
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Specification