SELECTIVELY CONNECTING THE TIP ELECTRODE DURING THERAPY FOR MRI SHIELDING

• US 20090149909A1
• Filed: 12/05/2008
• Published: 06/11/2009
• Est. Priority Date: 12/06/2007
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Ameri, Masoud
• Granted Patent: US 8,086,321 B2
• Time in Patent Office: Days
• US Class Current: 607/37
• CPC Class Codes: A61N 1/056 Transvascular endocardial electrode systems
• CPC Class Codes: A61N 1/086 Magnetic resonance imaging [MRI] compatible leads
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

A medical device includes a pulse generator and an electrode configured to contact tissue in a body vessel. The medical device includes a lead that includes a lead connector. The lead connector connects a pulse generator with an electrode via a conductive path. An electrode switch is electrically connected between the lead conductor and the electrode. The electrode switch includes an open state preventing the conductive path between the lead and the electrode. The electrode switch includes a closed state establishing the conductive path between the lead and the electrode when a voltage is applied across the electrode switch that exceeds a threshold voltage. The electrode switch in the open state electrically shields the electrode from electromagnetic radiation and induced voltages during magnetic resonance imaging.

Claims

1. A medical device, comprising:

a pulse generator configured to emit one or more therapy pulses;

a lead including an electrode configured to contact body tissue in a body vessel and a lead conductor connecting the pulse generator with the electrode via a conductive path;

an electrode switch electrically coupled between the lead conductor and the electrode, the electrode switch including an open state preventing the conductive path between the lead conductor and the electrode, the electrode switch including a closed state allowing formation of the conductive path between the lead conductor and the electrode upon reception of a voltage applied across the electrode switch which exceeds a threshold voltage; and

wherein the electrode switch in the open state is configured to electrically shield the electrode from at least electromagnetic radiation and induced voltages during magnetic resonance imaging.

2. The medical device according to claim 1, wherein the electrode switch further comprises:

a normally open switch configured to receive the one or more therapy pulses from the pulse generator, the normally open switch including the open state and the closed state, and

a switch controller configured to monitor a voltage applied across the normally open switch, the switch controller configured to switch the normally open switch from the open state to the closed state upon a voltage applied across the normally open switch exceeding the threshold voltage.

3. The medical device of claim 1, wherein the electrode switch is a diode for alternating current (DIAC) device.

4. The medical device of claim 1, wherein the voltage applied across the electrode switch is from at least one therapy pulse from the one or more therapy pulses emitted from the pulse generator.

5. The medical device of claim 4, wherein the voltage applied across the electrode from the at least one therapy pulse exceeds the threshold voltage.

6. The medical device of claim 1, wherein

the electrode switch comprises a threshold controller and a control line connecting the threshold controller to the pulse generator, and

the threshold controller is configured to receive at least one signal from the pulse generator to adjust the threshold voltage to another threshold voltage.

7. The medical device of claim 1, further comprising:

a high impedance resistor electrically connected in parallel with the electrode switch, the high impedance resistor configured to shield the electrode from electromagnetic radiation and induced voltages during magnetic resonance imaging, the high impedance resistor configured to provide another conductive path to recharge one or more capacitors located in the pulse generator.

8. The medical device of claim 1, wherein

the pulse generator is further configured to emit the one or more therapy pulses at a duration equal to or greater than a threshold duration, and

the electrode switch is further configured to operate in the closed state upon reception of the one or more therapy pulses having a voltage level exceeding the threshold voltage and a duration exceeding the threshold duration.

9. A method for monitoring a voltage applied across a switch, said method comprising:

monitoring a voltage across an electrode switch electrically coupled between a lead and an electrode, the electrode configured to contact tissue in a body vessel, the lead connecting a pulse generator with the electrode via a conductive path;

switching the electrode switch to an open state when the monitored voltage across the electrode switch is at or below a voltage threshold, the open state of the electrode switch preventing formation of the conductive path between the lead and the electrode;

switching the electrode switch to a closed state when the monitored voltage across the electrode switch exceeds the voltage threshold, the closed state of the electrode switch allowing formation of the conductive path between the lead and the electrode; and

wherein the electrode switch in the open state is configured to electrically shield the electrode from at least electromagnetic radiation and induced voltages during magnetic resonance imaging.

10. The method of claim 9, further comprising:

receiving one or more therapy pulses from the pulse generator, wherein

the voltage applied across the electrode switch is the one or more therapy pulses.

11. The method of claim 10, wherein the one or more therapy pulses exceeds the threshold voltage.

12. The method according to claim 9, further comprising:

receiving one or more signals via a control line connecting a switch controller to the pulse generator; and

adjusting the threshold voltage to another threshold voltage using the one or more signals.

13. The method according to claim 9, further comprising:

establishing another conductive path between the lead conductor and electrode via a high impedance resistor electrically connected in parallel with the electrode switch, the high impedance resistor configured to shield the electrode from electromagnetic radiation and induced voltages during magnetic resonance imaging; and

recharging one or more capacitors located in the pulse generator via the another conductive path.

14. The method of claim 9, wherein the electrode switch is a diode for alternating current (DIAC) device.

15. The method of claim 10, further comprising:

receiving the one or more therapy pulses from the pulse generator, the one or more therapy pulses having a duration greater than a threshold duration; and

switching the electrode switch to the closed state upon reception of the one or more therapy pulses having a voltage level exceeding the threshold voltage and a duration exceeding the threshold duration.

16. A medical device, comprising:

a pulse generator configured to deliver one or more therapy pulses;

an electrode configured to contact tissue in a body vessel;

a lead comprising proximal and distal ends, the lead connecting the pulse generator with the electrode via a conductive path;

at least one portion of the lead between the proximal and distal ends including an insulating material between an outer conductor and an inner conductor, the insulating material including a non-conductive state preventing the conductive path between the lead pulse generator and the electrode, the insulating material including a conductive state allowing formation of the conductive path between the lead and the electrode when receiving a voltage applied across the insulating material exceeding a voltage threshold of the insulating material; and

wherein the insulating material in the non-conductive state electrically shields the electrode from at least electromagnetic radiation and induced voltages during magnetic resonance imaging.

17. The medical device of claim 16, wherein

the pulse generator is in electrical communication with the outer conductor, and

the electrode is in electrical communication with the inner conductor.

18. The medical device of claim 16, wherein

the pulse generator is in electrical communication with the inner conductor, and

the electrode is in electrical communication with the outer conductor.

19. The medical device of claim 16, wherein the at least one portion of the lead extends along the length of the lead between the proximal and distal ends.

20. The medical device of claim 16, wherein the at least one portion of the lead is formed at the distal end.

21. The medical device of claim 16, wherein the voltage applied across the insulating material is from at least one therapy pulse from the one or more therapy pulses from the pulse generator.

22. The medical device of claim 21, wherein the voltage applied across the insulating material from the at least one therapy pulse exceeds the threshold voltage.