Automatic lead recognition for implantable medical device

• US 5,534,018 A
• Filed: 11/30/1994
• Issued: 07/09/1996
• Est. Priority Date: 11/30/1994
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Yerich, Charles G., Ecker, R. Michael, Greeninger, Daniel R., Wahlstrand, John D., Baxter, Daniel J.
• Primary Examiner(s): Sykes, Angela D.
• Assistant Examiner(s): HUANG, STEPHEN D
• Application Number:
  US08/346,661
• Time in Patent Office: 587 Days
• Field of Search: 607/9, 607/27, 607/28, 607/29, 128/734
• US Class Current: 607/27
• CPC Class Codes: A61N 1/3706 Pacemaker parameters stimulation threshold A61N1/371

Abstract

A method and apparatus for determining the availability of unipolar and/or bipolar pacing/sensing paths in a body-implantable cardiac pacing system. In one embodiment, a pacemaker system includes impedance monitoring circuitry for periodically measuring impedance between pairs of electrodes that are potentially available for pacing and/or sensing. This impedance monitoring circuitry includes circuitry for delivering excitation pulses between pairs of potentially available electrodes (including the pacemaker canister in the case of unipolar pacing or sensing), and for monitoring the current and voltage between those pairs of electrodes during delivery of an excitation pulse. Availability of a pair of electrodes for pacing and/or sensing is indicated if the impedance between a pair of electrodes is found to lie within a predetermined range. Detection of availability of a particular pair of electrodes is used initially as an indication that the pacing system has been implanted, and is also used to distinguish between unipolar and bipolar leads in the pacing system.

Claims

1. A body-implantable cardiac pacemaker system, comprising:

an electronic circuit, wherein said electronic circuit comprises;

an excitation circuit coupled to at least one conductor, for applying a sub-threshold symmetrical and bi-phasic voltage pulse along a current path;

an impedance measurement circuit, coupled to said at least one conductor and to a second electrode, adapted to measure impedance along said current path during application of said sub-threshold voltage pulse;

a comparison circuit, coupled to said impedance measurement circuit and adapted to determine whether said measured impedance lies within a predetermined impedance range, indicating availability of said current path for cardiac pacing;

a hermetic enclosure for housing said electronic circuit;

a flexible, elongate pacing/sensing lead having at least one conductor therein extending between proximal and distal ends of said lead, said at least one conductor being coupled at said proximal end to said electronic circuit in said hermetic enclosure and coupled near said distal end to a first conductive electrode adapted to be disposed in electrical contact with patient'"'"'s cardiac tissue;

a second electrode, electrically coupled to said electronic circuit in said hermetic enclosure, such that said current path is established extending from said electronic circuit, along said at least one lead to said electrode, through a portion of said patient'"'"'s body tissue to said second electrode and back to said electronic circuit;

Wherein said impedance measurement circuit further comprises;

a sampling circuit for obtaining a sample of voltage between said first and second electrodes during said application of said excitation pulse and for obtaining a sample of current between said first and second electrodes during said application of said excitation pulse;

an analog-to-digital converter for deriving a digital voltage value corresponding to a logarithm of said sampled voltage and a digital current value corresponding to the logarithm of said sampled current; and

an impedance computation circuit for deriving from said digital voltage and current values a digital impedance value corresponding to the logarithm of the impedance between said first and second electrodes during application of said excitation pulse, wherein said voltage pulse is bi-phasic and on the order of 0.26 volts, peak to peak.

2. A body implantable cardiac pacemaker system for implantation into a patient'"'"'s body:

a hermetic enclosure for housing electronic circuitry;

a flexible, elongate pacing/sensing lead having at least one conductor therein extending between proximal and distal ends of said lead, said at least one conductor being coupled at said proximal end to said electronic circuitry in said hermetic enclosure and coupled near to said distal end to a first conductive electrode adapted to be disposed in electrical contact with cardiac tissue in said patient'"'"'s body;

a second electrode, electrically coupled to said electronic circuitry in said hermetic enclosure, such that a current path is established extending from said electronic circuitry, along said at least one lead to said electrode, through a portion of said patient'"'"'s body tissue to said second electrode and back to said electronic circuitry;

said electronic circuitry comprising;

an excitation circuit coupled to said at least one conductor, for applying a sub-threshold symmetrical and bi-phasic voltage pulse along said current path;

an impedance measurement circuit, coupled to said at least one conductor and to said second electrode, adapted to measure impedance along said current path during application of said sub-threshold voltage pulse;

a comparison circuit, coupled to said impedance measurement circuit and adapted to determine whether said measured impedance lies within a predetermined impedance range, indicating availability of said current path for cardiac pacing;

wherein said voltage pulse is biphasic and on the order of 0.26 volts, peak to peak.