TISSUE CHARACTERIZATION USING INTRACARDIAC IMPEDANCES WITH AN IMPLANTABLE LEAD SYSTEM
First Claim
1. A method, comprising:
- generating a first pulse to apply to a bodily tissue via an electrode, wherein the first pulse has a first applied waveform that is charge-balanced and voltage-balanced and wherein the first applied waveform has a duration less than a charging time constant of an electrode-electrolyte interface between the electrode and the bodily tissue;
applying the first pulse having the first applied waveform to the bodily tissue;
sensing a first waveform response to the first pulse;
measuring a morphology of the first waveform response;
generating a second pulse to apply to the bodily tissue via an electrode, wherein the second pulse has a second applied waveform that is charge-balanced and voltage-balanced and wherein the second applied waveform has a duration that is different from the duration of the first applied waveform and less than the charging time constant of the electrode-electrolyte interface between the electrode and the bodily tissue;
applying the second pulse having the second applied waveform to the bodily tissue;
sensing a second waveform response to the second pulse;
measuring a morphology of the second waveform response;
determining a difference between the morphology of the first waveform response and the morphology of the second waveform response; and
determining a tissue characteristic based on at least the difference between the morphology of the first waveform response and the morphology of the second waveform response.
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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.
15 Citations
21 Claims
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1. A method, comprising:
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generating a first pulse to apply to a bodily tissue via an electrode, wherein the first pulse has a first applied waveform that is charge-balanced and voltage-balanced and wherein the first applied waveform has a duration less than a charging time constant of an electrode-electrolyte interface between the electrode and the bodily tissue; applying the first pulse having the first applied waveform to the bodily tissue; sensing a first waveform response to the first pulse; measuring a morphology of the first waveform response; generating a second pulse to apply to the bodily tissue via an electrode, wherein the second pulse has a second applied waveform that is charge-balanced and voltage-balanced and wherein the second applied waveform has a duration that is different from the duration of the first applied waveform and less than the charging time constant of the electrode-electrolyte interface between the electrode and the bodily tissue; applying the second pulse having the second applied waveform to the bodily tissue; sensing a second waveform response to the second pulse; measuring a morphology of the second waveform response; determining a difference between the morphology of the first waveform response and the morphology of the second waveform response; and determining a tissue characteristic based on at least the difference between the morphology of the first waveform response and the morphology of the second waveform response. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method, comprising:
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generating pulses having applied waveforms that alternate between a first duration and a second duration, wherein the applied waveforms are charge-balanced and voltage-balanced and wherein the first and second durations are less than a charging time constant of an electrode-electrolyte interface between the electrode and the bodily tissue, and wherein the first duration is different from the second duration; applying the pulses to one or more vectors of a bodily tissue via one or more electrodes; sensing waveform responses to the generated pulses along the one or more vectors of the bodily tissue; measuring a morphology of the waveform responses; determining a difference between the morphology of the sensed waveform responses along the one or more vectors of the bodily tissue; and determining a tissue characteristic based on at least the difference between the morphology responses along the one or more vectors. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. A method, comprising:
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generating a plurality of pulses to apply to one or more vectors of a bodily tissue via one or more electrodes, wherein the pulses have applied waveforms that are charge-balanced and voltage-balanced and wherein the applied waveforms have durations that are each less than a charging time constant of an electrode-electrolyte interface between the electrode and the bodily tissue and wherein the duration of the applied waveforms is modulated continuously over a spectrum of durations; applying the pulses to the one or more vectors of the bodily tissue using the one or more electrodes; sensing a waveform response to each of the pulses along each of the one or more vectors; measuring a morphology of each of the waveform responses; determining a difference between the morphology of each of the waveform responses along each of the one or more vectors; and determining a physiological parameter based on at least the difference between the morphologies of the waveform responses along each of the one or more vectors.
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Specification