Time sharing multipolar rheography apparatus and method

• US 5,501,702 A
• Filed: 07/19/1994
• Issued: 03/26/1996
• Est. Priority Date: 06/06/1994
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Ceccarelli, Massimo, Plicchi, Gianni
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): Getzow, Scott M.
• Application Number:
  US08/277,051
• Time in Patent Office: 616 Days
• Field of Search: 607/17, 607/20, 607/24, 607/5
• US Class Current: 607/20
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence

Abstract

A cardiac pacemaker having switching circuitry for dynamically re-assigning the electrical function of a plurality of electrodes coupled thereto. The pacemaker is provided with switching circuitry for allowing the sensing signals from a plurality of implanted electrodes may be selectively applied to sensing and detection circuitry in the pacemaker. Controller circuitry in the pacemaker controls the operation of the switching circuits and of a rheography current pulse generator such that a plurality of time slots are defined during a sensing interval. During successive time slots, a different electrical function may be assigned to the same electrode. Also disclosed is a method of operating such a pacing system.

Claims

1. A pulse generator system comprising:

a plurality of electrodes, each adapted to be disposed at a separate site in a patient'"'"'s body;

a plurality of conductive leads, each coupled at a distal end to one of said plurality of electrodes;

first and second switching circuits coupled to a proximal end of each of said plurality of leads;

a rheography pulse generating circuit coupled to said first switching circuit, said rheogmphy pulse generating circuit adapted to generate a constant current rheography pulse in response to a rheography pulse control signal;

an impedance detection circuit having first and second terminals coupled to said second switching circuit, said impedance detection circuit adapted to produce an output voltage corresponding to an impedance present between said first and second impedance detection circuit terminals;

control circuitry coupled to said first and second switching circuits and to said rheography pulse generating circuit. said control circuitry adapted to generate a source control signal identifying two of said plurality of leads, and to generate a recording control signal identifying two of said plurality of leads, and to generate said rheography pulse control signal;

wherein said first switching circuit is responsive to said source control signal to couple said two leads identified by said source control signal to said rheography pulse generating circuit, and wherein said second switching circuit is responsive to said recording control signal to couple said two leads identified by said recording control signal to said first and second impedance detection circuit terminals, respectively;

such that said rheography current pulse is conducted on said leads identified by said source control signal and such that said impedance detection circuit output voltage corresponds to impedance between said leads identified by said recording control signal.

2. A pulse generator system in accordance with claim 1 further comprising a conductive pacemaker canister coupled to said first and second switching circuits.

3. A method of detecting respiration and cardiac systole in a patient, comprising the steps of:

(a) implanting at least one multipolar pace/sense lead such that a plurality of pace/sense electrodes are disposed at spaced-apart in vivo sites;

(b) defining a plurality of time slots during which rheographic measurements are to be made;

(c) delivering a constant current pulse between different pairs of said electrodes during successive time slots; and

(d) measuring the voltage differential between different pairs of said electrodes during successive time slots.

4. A cardiac pacemaker system, comprising:

a rheography pulse generating circuit adapted to generate constant current rheography pulses;

an impedance detection circuit having first and second terminals, said detection circuit adapted to generate an output voltage proportional to the voltage between said first and second terminals;

a plurality of electrodes adapted to be disposed at spaced apart in vivo sites;

a first switching circuit, coupled to said plurality of electrodes via a plurality of conductive leads and further coupled to said pulse generating circuit, said first switching circuit being responsive to source control signals identifying source conductor pairs from among said plurality of conductors to couple said source conductor pairs to said pulse generating circuit;

a second switching circuit, coupled to said plurality of electrodes via said plurality of conductive leads and further coupled to said impedance detection circuit, said second switching circuit being responsive to recording control signals identifying recording conductor pairs from among said plurality of conductors to couple said recording conductor pairs to said impedance detection circuit; and

control circuitry coupled to said first and second switching circuit and to said pulse generating circuit, said control circuitry adapted to generate said source control signals and said record control signals.

5. A cardiac pacemaker system, comprising:

a rheography circuit including a rheography pulse generator, an impedance detector, and a switching circuit, said pulse generator adapted to generate a sequence of rheogmphy current pulses;

a plurality of electrodes adapted to be disposed at in vivo sites, coupled to said rheogmphy circuit by a plurality of pairs of conductive leads;

control circuitry, coupled to said switching circuit and to said pulse generator, said control circuitry adapted to control said switching circuit to couple a different pair of said conductive leads to said pulse generator for each one of said sequence of current pulses, and to couple a different pair of said conductive leads to said impedance detector for each of said sequence of current pulses.

6. A method of making rheographic measurements, comprising the steps of:

(a) disposing a plurality of electrodes at different in vivo sites;

(b) generating a series of rheography current pulses;

(c) for each rheography pulse generated in step (b), directing said pulses to a different pair of said electrodes; and

(d) for each rheography pulse generated in step (b), coupling a different pair of said electrodes to an impedance detection circuit.

7. A cardiac pacemaker system, comprising:

a rheography circuit including a rheography pulse generator, an impedance detector, and a switching circuit, said pulse generator adapted to generate a rheography current pulse;

a first electrode adapted to be disposed in vivo, coupled to said rheography circuit by a first conductor;

a second electrode adapted to be disposed in vivo, coupled to said rheography circuit by a second conductor;

a third electrode adapted to be disposed in vivo, coupled to said rheography circuit by a third conductor;

control circuitry, coupled to said switching circuit and to said pulse generator, said control circuitry adapted to control said switching circuit to couple a different pair of said conductors to said pulse generator for each one of said rheography current pulses, and to couple a different pair of said conductors to said impedance detector for each of said rheography current pulses.