IMPLANTABLE MEDICAL DEVICE INCLUDING CONTROLLABLY ISOLATED HOUSING

• US 20110160807A1
• Filed: 12/23/2010
• Published: 06/30/2011
• Est. Priority Date: 12/31/2009
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Linder, William J., Lyden, Michael J.
• Granted Patent: US 8,855,784 B2
• Time in Patent Office: Days
• US Class Current: 607/63
• CPC Class Codes: A61N 1/025 Digital circuitry features of electrotherapy devices, e.g. memory, clocks, processors
• CPC Class Codes: A61N 1/3605 Implantable neurostimulators for stimulating central or peripheral nerve system
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• CPC Class Codes: A61N 1/3758 Packaging of the components within the casing
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

An implantable medical device or some other ambulatory medical device, such as a pacer, defibrillator, or other cardiac rhythm management device can include an electrical energy delivery circuit, such as including an integrated circuit comprising a first electrostimulation output terminal, a can terminal, and a switch control output. The ambulatory or implantable device can include at least two switches in series, each including a respective substrate electrically separate from the integrated circuit, and from each other, the switches configured to controllably isolate a conductive housing of the implantable medical device from the can terminal of the integrated circuit, such as in response to the switch control output.

Claims

1. An apparatus comprising:

an implantable medical device comprising;

an implantable housing including a conductive portion;

an implantable electrostimulation output circuit located within the housing, the electrostimulation output circuit including;

a housing terminal; and

a switch control output; and

a switch, physically separate from the electrostimulation output circuit, located within the housing, and electrically coupled between the housing terminal and the conductive portion of the housing, the switch configured to controllably electrically isolate the conductive portion of the housing from the housing terminal of the electrostimulation output circuit in response to a control signal provided by the switch control output.

2. The apparatus of claim 1, comprising a rectifier electrically coupled in parallel with the switch, between the housing terminal of the electrostimulation output circuit and the conductive portion of the housing.

3. The apparatus of claim 1, wherein the electrostimulation output circuit comprises an integrated circuit including a first substrate;

wherein the switch includes a second substrate; and

wherein the first and second substrates are electrically isolated from each other.

4. The apparatus of claim 1, wherein the switch comprises two transistors electrically coupled in a series configuration and configured to be respectively controlled via the switch control output to controllably electrically isolate the conductive portion of the housing from the housing terminal of the electrostimulation output circuit.

5. The apparatus of claim 4, wherein the two transistors comprise field effect transistors;

wherein each field effect transistor includes a respective body diode in parallel with a respective source and a respective drain terminal of each field effect transistor; and

wherein the field effect transistors are electrically coupled in a series configuration wherein the body diodes oppose each other.

6. The apparatus of claim 4, wherein the electrostimulation output circuit includes a substrate;

wherein each transistor includes a respective substrate, and

wherein the respective substrates of the transistors are respectively electrically isolated from the electrostimulation output circuit substrate, and from each other.

7. The apparatus of claim 4, wherein the two transistors comprise:

a first transistor electrically coupled to the housing terminal of the electrostimulation output circuit;

a second transistor electrically coupled to the conductive portion of the housing;

wherein the first and second transistors are connected to each other in a series configuration;

wherein the second transistor includes a control input; and

wherein the implantable medical device includes a capacitor connected between the control input of the second transistor and the conductive portion of the housing.

8. The apparatus of claim 7, wherein the first transistor includes a control input;

and

wherein the implantable medical device includes a first resistor connected between the respective control inputs of the first and second transistors.

9. The apparatus of claim 8, further comprising an electrode at a location distal to the housing, the electrode coupled to the first electrostimulation output terminal;

wherein the implantable medical device comprises a second resistor connected between the first electrostimulation output terminal and a circuit ground of the electrostimulation output circuit; and

wherein the apparatus is configured to charge the capacitor using a current path including the first resistor, the second resistor, the distally-located electrode, and the conductive portion of the housing to maintain a specified voltage between the control input of the second transistor and a terminal of the second transistor connected to the conductive portion of the housing.

10. The apparatus of claim 1, comprising a magnetic field sensor;

and

wherein the electrostimulation output circuit is configured to controllably isolate the conductive portion of the housing from the housing terminal of the electrostimulation output circuit using the switch in response to information from the magnetic field sensor indicative of at least one of a magnetic resonance imaging field or another external magnetic field in excess of a specified threshold.

11. The apparatus of claim 1, wherein the electrostimulation output circuit is configured to controllably isolate the conductive portion of the housing from the housing terminal of the electrostimulation output circuit in response to a command received from an external assembly in communication with the implantable medical device.

12. An implantable medical device including a processor-readable medium comprising instructions that, when performed by the processor, cause the implantable medical device to controllably isolate a conductive portion of a housing of the implantable medical device from a housing terminal of an implantable electrostimulation output circuit included as a portion of the implantable medical device, using a switch located within the housing, the switch physically separate from the electrostimulation output circuit.

13. The implantable medical device of claim 12, comprising a magnetic field sensor;

and

wherein the processor-readable medium comprises instructions that cause the implantable medical device to controllably isolate the conductive portion of the housing from the housing terminal of the electrostimulation output circuit using the switch, in response to information from the magnetic field sensor indicative of at least one of a magnetic resonance imaging field or another external magnetic field in excess of a specified threshold.

14. The implantable medical device of claim 13, wherein the processor-readable medium comprises instructions that cause the implantable medical device to allow the conductive portion of the housing to be connected to the housing terminal of the electrostimulation output circuit via the switch, in response to information from the magnetic field sensor indicative that the external magnetic field is below the specified threshold, during a specified duration of time.

15. The implantable medical device of claim 12, wherein the processor-readable medium comprises instructions that cause the implantable medical device to connect the conductive portion of the housing to the housing terminal of the electrostimulation output circuit via the switch, by default, when the information received from the magnetic field sensor indicates that the external magnetic field is below the specified threshold.

16. The implantable medical device of claim 12, wherein the processor-readable medium comprises instructions that cause the implantable medical device to controllably isolate the conductive portion of the housing from the housing terminal of the electrostimulation output circuit using the switch, in response to a command received from an external assembly in communication with the implantable medical device.

17. The implantable medical device of claim 12, wherein the electrostimulation output circuit comprises an integrated circuit including a first substrate;

wherein the switch includes a second substrate; and

wherein the first and second substrates are electrically isolated from each other.

18. The implantable medical device of claim 12, wherein the switch comprises two transistors electrically coupled in a series configuration;

and

wherein the processor-readable medium comprises instructions that cause the implantable medical device to controllably electrically isolate the conductive portion of the housing from the housing terminal of the electrostimulation output circuit using the two transistors.

19. The implantable medical device of claim 18, wherein the two transistors comprise field effect transistors;

wherein each field effect transistor includes a respective body diode in parallel with a respective source and a respective drain terminal of each field effect transistor; and

wherein the field effect transistors are electrically coupled in a series configuration wherein the body diodes oppose each other.

20. An implantable medical device comprising:

an implantable housing including a conductive portion;

an implantable electrostimulation output circuit located within the housing, the electrostimulation output circuit including;

a housing terminal; and

a switch control output;

a switch comprising two transistors electrically coupled in a series configuration, the switch physically separate from the electrostimulation output circuit and located within the housing, and electrically coupled between the housing terminal and the conductive portion of the housing, the switch configured to controllably electrically isolate the conductive portion of the housing from the housing terminal of the electrostimulation output circuit in response to a control signal provided by the switch control output;

wherein the electrostimulation output circuit includes a substrate;

wherein each transistor includes a respective substrate, and

wherein the respective substrates of the transistors are respectively electrically isolated from the electrostimulation output circuit substrate, and from each other.