Tissue characterization using intracardiac impedances with an implantable lead system
First Claim
1. A method, comprising:
- generating pulses in an implantable device, wherein a multi-phasic waveform of each pulse possesses alternating positive and 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 alternating positive and negative phases have an additive net-zero charge, wherein at least one negative phase has an absolute amplitude less than an absolute amplitude of one of the positive phases, 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;
applying the pulses to a bodily tissue;
measuring a frequency response of the bodily tissue to the applied pulses; and
determining a tissue characteristic based on the frequency response.
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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.
119 Citations
22 Claims
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1. A method, comprising:
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generating pulses in an implantable device, wherein a multi-phasic waveform of each pulse possesses alternating positive and 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 alternating positive and negative phases have an additive net-zero charge, wherein at least one negative phase has an absolute amplitude less than an absolute amplitude of one of the positive phases, 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; applying the pulses to a bodily tissue; measuring a frequency response of the bodily tissue to the applied pulses; and determining a tissue characteristic based on the frequency response. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method, comprising:
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generating pulses in an implantable device to apply to a bodily tissue via an electrode, wherein each pulse has a multi-phasic waveform having alternating positive and 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 alternating positive and negative phases have different absolute amplitudes, and wherein the multi-phasic waveform has a duration less than a charging time constant of an electrode-electrolyte interface between the electrode and the bodily tissue; applying the pulses to the bodily tissue; measuring a frequency response of the bodily tissue to the applied pulses; and determining a tissue characteristic based on the frequency response. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A method, comprising:
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generating pulses in an implantable device to apply to a bodily tissue via an electrode, wherein a multi-phasic waveform of each pulse possesses alternating positive and negative phases that have an additive net-zero charge and wherein the multi-phasic waveform is 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, wherein each phase of the multi-phasic waveform 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 at least one negative phase has an absolute amplitude less than an absolute amplitude of one of the positive phases, and each pulse has a duration less than a charging time constant of an electrode-electrolyte interface between the electrode and the bodily tissue; applying the pulses to the bodily tissue; measuring a frequency response of the bodily tissue to the applied pulses; and determining a tissue characteristic based on the frequency response. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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Specification