Multi-site impedance sensor using coronary sinus/vein electrodes

A method for carrying out impedance plethysmography on a living heart, comprising the steps of:

• (a) installing a first lead including at least two electrodes in a right ventricular chamber of said heart;
• (b) installing a second lead including a plurality of electrodes in a coronary vein on the left ventricle of the heart;
• (c) coupling a subthreshold AC drive signal source between one of
• (i) the at least two electrodes on the first lead,
• (ii) one of the at least two electrodes on the first lead and a first of the plurality of electrodes on the second lead,
• (iii) the first and a second of the plurality of electrodes on the second lead;
• (d) coupling a signal sensing circuit between
• (i) a third and a fourth electrode on the second lead when the AC drive signal is coupled to the at least two electrodes on the first lead,
• (ii) the other of the at least two electrodes on the first lead and the first of the plurality of the electrodes on the second lead when the AC drive signal is coupled to one of the at least two electrodes on the first lead and the third of the plurality of electrodes on the second lead,
• (iii) the third and fourth of the plurality of electrodes on the second lead when the AC drive signal is coupled to the first and second of the plurality of electrodes on the second lead;
• and
• (e) extracting a signal representative of electrical impedance from the signal sensing circuit.

A method for carrying out impedance plethysmography comprising the steps of:

• (a) installing a first lead including at least two electrodes in a right ventricular chamber of said heart;
• (b) installing a second lead including a plurality of electrodes in a coronary vein on the left ventricle of the heart;
• (c) installing a third lead having an electrode in a right atrial chamber of the heart;
• (d) coupling an AC drive signal source between one of:
• (i) the at least two electrodes on the first lead,
• (ii) one of the at least two electrodes on the first lead and a first of the plurality of electrodes on the second lead,
• (iii) the first and a second of the plurality of electrodes on the second lead,
• (iv) the electrode on the third lead and one of the electrodes on the first lead;
• (e) coupling a signal sensing circuit between:
• (i) a third and a fourth of the plurality of electrodes on the second lead when the AC drive signal is coupled to the at least two electrodes on the first lead,
• (ii) the other of the at least two electrodes on the first lead and the third of the plurality of electrodes on the second lead when the AC drive signal is coupled to one of the at least two electrodes on the first lead and a third of the plurality of electrodes on the second lead,
• (iii) the third and a fourth of the plurality of electrodes on the second lead when the AC drive signal is coupled to the first and second of the plurality of electrodes on the second lead,
• (iv) the first and the third of the plurality of electrodes on the second lead or the other electrode on the first lead and the third of the plurality of electrodes on the second lead when the AC drive signal is coupled to the electrode on the third lead and one of the electrodes on the first lead;
• and
• (f) extracting a signal representative of the electrical impedance from the signal sensing circuit.

A method for carrying out impedance plethysmography on a living heart, comprising the steps of:

• (a) installing a first lead in a right ventricle of the heart, the first lead including at least two electrodes RV1 and RV2 thereon disposed in the right ventricle;
• (b) installing a second lead in a coronary vein on the left ventricle of the heart, the second lead including a plurality of electrodes including at least two of CS1, CS2, CS3 and CS4 thereon;
• (c) coupling a source of subthreshold AC drive signals and a signal sensing circuit to predetermined pairs of said electrodes in accordance with an entry in the following table:
• AC DRIVE SOURCE SENSING CIRCUIT RV1, RV2 CS2, CS3 CS1, CS4 CS2, CS3 RV2, CS1 RV1, CS2
• and;
• (d) extracting a signal representative of electrical impedance from the signal sensing circuit.

An apparatus for conducting impedance plethysmography on a living heart, comprising:

• (a) a first electrical lead having a plurality of electrodes adapted for placement in a coronary vein on the left ventricular chamber of said heart;
• (b) a second lead having a plurality of electrodes and adapted for placement in a right ventricular chamber of the heart;
• (c) means for applying a subthreshold AC carrier signal across selected ones of said plurality of electrodes on one or both of the first and second electrical leads;
• (d) means for sensing electrical signals connected across a pair of said plurality of electrodes where at least one of said pair of electrodes is on the first electrical lead;
• and
• (e) means connected to the sensing means for demodulating the sensed electrical signals.

Apparatus for carrying out impedance plethysmography on a living heart, comprising:

• (a) a first lead having a plurality of electrodes adapted for placement in a right ventricular chamber of said heart;
• (b) a second lead having a plurality of electrodes adapted for placement in a coronary vein on the left ventricle of the heart;
• (c) a source of AC drive signals;
• (d) a switching circuit for connecting said source of AC drive signals to selected ones of the electrodes on the first and second leads;
• (e) a signal sensing circuit coupled by the switching circuit to at least one electrode on the second lead and another electrode on the second lead and another electrode on one of the first and second leads;
• and
• (f) a demodulator coupled to the signal sensing circuit, the demodulator extracting a signal proportional to the electrical impedance between said at least one electrode on the second lead and said another electrode on one of the first and second leads.

An apparatus for carrying out impedance plethysmography on a living heart, comprising:

• (a) a first electrical lead having at least two electrodes thereon adapted for placement in the right ventricular chamber of said heart;
• (b) a second electrical lead having a plurality of electrodes thereon adapted for placement in a coronary vein on the left ventricle of said heart;
• (c) a source of AC drive signals;
• (d) a signal sensing circuit;
• (e) a switching circuit for connecting said source and said sensing circuit to the electrodes on the first and second leads in accordance with an entry in the following table:
• AC DRIVE SOURCE SENSING CIRCUIT FIGURE RV1, RV4 CS2, CS3 2b CS1, CS4 CS2, CS3 2c RV2, CS1 RV1, CS2 2d
• and;
• (f) a demodulator coupled to the signal sensing circuit, the demodulator extracting a signal proportional to the electrical impedance between the electrodes to which the switching circuit has connected the sensing circuit.