Implantable electronic stimulator having isolation transformer input to telemetry circuits

• US 6,505,072 B1
• Filed: 11/16/2000
• Issued: 01/07/2003
• Est. Priority Date: 11/16/2000
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Linder, William J., Amundson, Mark D.
• Primary Examiner(s): WOLFE JR, WILLIS RAY
• Application Number:
  US09/714,337
• Time in Patent Office: 782 Days
• Field of Search: 607/4, 607/5, 607/9, 607/12, 607/14, 607/30, 607/32, 607/60, 128/903
• US Class Current: 607/32
• CPC Class Codes: A61N 1/37211 Means for communicating with stimulators
• CPC Class Codes: A61N 1/3752 Details of casing-lead connections
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

An implantable medical device for applying electrical stimulating pulses to body tissue in which the device includes a hermetically sealed metal housing that contains the stimulating pulse delivery circuitry as well as a telemetry transmitter and telemetry receiver and where the metal housing serves as a return electrode. An isolation transformer is operatively coupled between an antenna/coil used to receive and transmit information from and to an external programmer device and the telemetry receiver and telemetry transmitter within the implanted device. The isolation transformer effectively precludes high voltage stimulating pulses from causing damage to the telemetry circuit components.

Claims

1. An implantable medical device comprising:

(a) a moisture impervious, body compatible, metal housing containing a therapy delivery circuit, a telemetry transmitter and a telemetry receiver;

(b) an electrically non-conductive header affixed to the metal housing and supporting a magnetic or electromagnetic field energized coil/antenna;

(c) at least one hermetically sealed feed-through pin extending from the header into the metal housing and connected to the coil/antenna; and

(d) an isolation transformer contained within the housing and having a primary winding and a first secondary winding, with at least one terminal of the primary winding being coupled to the at least one feed-through pin and the first secondary winding coupled in circuit with at least one of the telemetry transmitter and telemetry receiver to permit signal flow between the at least one telemetry transmitter or the telemetry receiver and the coil/antenna, the isolation transformer electrically isolating the at least one telemetry transmitter and telemetry receiver from voltages impressed on the housing by the therapy delivery circuit.

2. The implantable medical device of claim 1 and further including:

a further terminal of the primary winding electrically connected to a chassis ground point on the metal housing and one terminal of the secondary winding being connected to a local ground point isolated from the metal housing.

3. The implantable medical device of claim 1 wherein the isolation transformer is a balun transformer with the secondary winding coupled to the input terminals of the telemetry receiver and to the output terminals of the telemetry transmitter.

4. The implantable medical device of claim 1 wherein the secondary winding is coupled in circuit with both the telemetry transmitter and the telemetry receiver.

5. The implantable medical device of claim 1 and further including a further hermetically sealed feed-through pin extending from the header into the metal housing and connected to the therapy delivery circuit.

6. The implantable medical device of claim 1 and further including a second secondary winding with the telemetry transmitter having output terminals coupled to the first secondary winding and the telemetry receiver having input terminals coupled to the second secondary winding.

7. The implantable medical device of claim 6 wherein the coil/antenna comprises first and second coil segments, each having a first terminal connected in common to the at least one feed-through pin and a second terminal connected in common to the metal housing.

8. The implantable medical device of claim 1 and further including a second hermetically sealed feed-through pin extending from the header into the metal housing and being coupled to the coil/antenna.

9. The implantable medical device of claim 8 wherein the primary winding has a further terminal coupled to the second hermetically sealed feed-through pin.

10. The implantable medical device of claim 9 wherein the at least one terminal and a further terminal of the primary winding are capacitively coupled individually to the at least one and the second hermetically sealed feed-through pins.

11. In an implantable medical device of the type having a hermetically sealed, body compatible electrically conductive housing for enclosing a therapy circuit, a telemetry transmitting circuit and a telemetry receiving circuit where the therapy circuit delivers relatively high voltage output signals between the conductive housing and a lead mounted electrode, a method of protecting the telemetry transmitting circuit and the telemetry receiving circuit from the relatively high output voltage, comprising the steps of

(a) affixing a non-conductive header to the conductive housing, the header supporting a transmitting and receiving coil/antenna;

(b) providing a hermetically sealed conductive feed-through including a conductive pin extending from the interior of the housing into the header;

(c) connecting the conductive pin to the transmitting and receiving coil/antenna;

(d) placing an isolation transformer within the housing, the isolation transformer having a primary winding with first and second terminals and a secondary winding with first and second terminals;

(e) connecting the first terminal of the primary winding to the conductive pin within the housing and the second terminal of the primary winding to the housing; and

(f) coupling at least one of the first and second terminals of the secondary winding to the telemetry transmitting circuit and the telemetry receiving circuit.

12. In an implantable medical device having a metal housing defining a sealed chamber and an insulating header affixed to the exterior housing, the chamber containing a therapy delivery circuit, a telemetry receiver and telemetry transmitter, a lead carrying an electrode and operatively coupled through a hermetically sealed feed-through pin extending between the header and the therapy delivery circuit within the housing for applying a stimulating voltage pulse between the electrode and the metal housing, and a telemetry coil supported by the header, the improvement comprising:

an isolation transformer disposed within the housing, the isolation transformer having a primary winding coupled between a further feed-through pin and the metal housing and a secondary winding coupled between at least one of an input of the telemetry receiver and an output of the telemetry transmitter and a point of reference potential for the at least one telemetry receiver and telemetry transmitter such that the point of reference potential is conductively isolated from the stimulating voltage pulses.

13. An implantable medical device comprising:

(a) a conductive metal housing defining a sealed chamber;

(b) an insulating header affixed to an exterior portion of the housing and having a lead terminal receiving bore formed therein;

(c) a therapy delivery circuit, a telemetry receiver, a telemetry transmitter, a telemetry transmitter contained within the housing;

(d) an elongated, flexible lead body having a proximal end and a distal end with at least one electrode proximate the distal end of the lead body and connected by a conductor within the lead body to a lead terminal at the proximal end;

(e) a first feed-through pin extending from the header into the sealed chamber, the first feed-through pin being connected to the therapy delivery circuit and to the lead terminal, when the lead terminal is inserted into the lead terminal receiving bore of the header;

(f) a telemetry antenna/coil supported by the header and having a first terminal thereof connected to a second feed-through pin; and

(g) an isolation transformer disposed within the sealed chamber and having a primary winding and a secondary winding, the primary winding being connected between the second feed-through pin and the metal housing and the secondary winding being coupled to at least one of the telemetry transmitter and telemetry receiver and a point of fixed potential.

14. The implantable medical device of claim 13 wherein the secondary winding is coupled to an input of the telemetry receiver, an output of the telemetry transmitter and to the point of fixed potential.

15. The implantable medical device of claim 13 wherein the isolation transformer includes first and second secondary windings with inputs of the telemetry receiver connected to the first secondary winding and the output of the telemetry transmitter connected to the second secondary winding.

16. The implantable medical device of claim 15 wherein the antenna/coil is a humbucking coil.

17. An implantable medical device comprising:

(a) a conductive metal housing defining a sealed enclosure;

(b) a therapy delivery circuit, a telemetry transmitter and a telemetry receiver contained within the enclosure;

(c) an insulating header affixed to an exterior portion of the metal housing, the header having a lead terminal receiving bore formed therein;

(d) a tissue stimulating lead having a proximal end and a distal end with at least one electrode proximate the distal end and a lead terminal at the proximal end, the lead terminal having contacts thereon electrically connected to the at least one electrode by a conductor, the conductor adapted to serve as a telemetry antenna;

(e) first and second hermetically sealed feed-through pins extending between the lead terminal receiving bore, and the interior of the sealed enclosure and adapted to make electrical contact with contacts on the lead terminal when the lead terminal is inserted into the bore; and

(f) an isolation transformer having a primary winding and a secondary winding, the primary winding being coupled to the first and second feed-through pins and the secondary winding having a first terminal connected to an input of the telemetry receiver circuit and an output of the telemetry transmitter and a second terminal to a point of fixed potential.

18. The implantable medical device of claim 17 and further including a high-pass filter connected in circuit with the primary winding of the isolation transformer for attenuating signals produced by the therapy delivery circuit.

19. The implantable medical device of claim 18 and further including a low-pass filter circuit coupled between the therapy delivery circuit and the first and second feed-through pins for attenuating high frequency telemetry signals picked up by the telemetry antenna.