Tissue characterization using intracardiac impedances with an implantable lead system

摘要

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.

主权项

1. A method for use in an implantable device, comprising:
generating pulses to apply to a bodily tissue via an electrode, wherein each pulse has an asymmetric amplitude waveform possessing alternating positive and negative phases that are charge-balanced and voltage-balanced, the asymmetric amplitude waveform having a duration less than a charging time constant of an electrode-electrolyte interface between the electrode and the bodily tissue; applying the pulses having the waveform to the bodily tissue, wherein the pulses are applied at a frequency within a range of frequencies consisting of approximately 1 Hz to approximately 100 kHz; and measuring an effect of the applied pulses to determine a physiological parameter.