Tissue characterization using intracardiac impedances with an implantable lead system

A method, comprising:

• generating electric pulses in an implantable device to apply to a bodily tissue via an electrode, wherein each pulse has a duration less than a charging time constant of an electrode-electrolyte interface between the electrode and the bodily tissue, each pulse comprises a multi-phasic waveform having alternating positive and negative phases, each phase comprises a duration and an amplitude, wherein duration is defined as the width of the phase and amplitude is defined as the height of the phase, the absolute amplitude of at least one positive phase is different from the absolute amplitude of at least one negative phase, the multi-phasic waveform is charge-balanced and voltage-balanced, and the multi-phasic waveform comprises 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;
• applying the pulses to the bodily tissue;
• sensing an electric response resulting from the applied pulses in the bodily tissue;
• determining a phase delay between the applied pulses and the sensed electric response;
• and
• determining a tissue characteristic based on the phase delay.

A method, comprising:

• generating electric pulses in an implantable device to apply to a bodily tissue via an electrode, wherein each electric pulse has a multi-phasic waveform having alternating positive and negative phases that are charge-balanced and voltage-balanced, each phase comprises a duration and an amplitude, wherein duration is defined as the width of the phase and amplitude is defined as the height of the phase, at least one negative phase has an absolute amplitude less than an absolute amplitude of one of the positive phases, the waveform of 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;
• sensing an electric response resulting from the applied pulses in the bodily tissue;
• determining a phase delay between the applied pulses and the sensed electric response;
• and
• determining a tissue characteristic based on the phase delay.