Selectively connecting the tip electrode during therapy for MRI shielding

• US 8,897,875 B2
• Filed: 11/22/2011
• Issued: 11/25/2014
• 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
• Primary Examiner(s): Stice, Paula J
• Application Number:
  US13/302,715
• Publication Number:
  US 20120071941A1
• Time in Patent Office: 1,099 Days
• US Class Current: 607/36
• 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 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 selectively connecting the pulse generator with the electrode via a conductive path;

an inner conductor and an outer conductor, each of the inner conductor and the outer conductor extending within the lead and the outer conductor extending coaxially around the inner conductor, the inner conductor in electrical communication with the pulse generator, the outer conductor in electrical communication with the electrode;

at least one portion of the lead located proximal of the electrode and between the proximal and distal ends, the at least one portion including an insulating material between the outer conductor and the inner conductor, the insulating material configured to;

exhibit a non-conductive state in which the insulating material is configured to block current induced in the outer conductor by an MRI system from being transmitted to the inner conductor to minimize current on the inner conductor during an MRI scan, and

exhibit a conductive state in which the insulating material is configured to permit the one or more therapy pulses from the pulse generator to be transmitted between the inner conductor and the outer conductor through the insulating material, wherein the insulating material has a breakdown voltage threshold between a first voltage associated with the current induced by the MRI system and a second voltage associated with the stimulation energy;

an outer insulating layer extending over and encapsulating the outer conductor; and

wherein each of the insulating material, the outer conductor, and the outer insulating layer are concentrically disposed around the inner conductor at a cross section of the at least one portion of the lead that is orthogonal to a longitudinal axis of the lead.

2. The medical device of claim 1, wherein the at least one portion of the lead extends along the length of the lead between the proximal and distal ends, and wherein each of the insulating material, the outer conductor, and the outer insulating layer are concentrically disposed around the inner conductor along the length of the lead.

3. A medical device lead comprising:

a first conductor;

an electrode distal of the first conductor and electrically coupled to the first conductor;

a second conductor that is coaxial with the first conductor along at least a portion of the lead;

an insulating layer radially between the first conductor and the second conductor along at least the portion of the lead, the insulating layer proximal of the electrode, the insulating layer having a breakdown voltage threshold between a first voltage associated with a current induced in the second conductor by an MRI system and a second voltage associated with therapeutic stimulation energy such that the insulating layer permits conduction of the therapeutic stimulation energy from the first conductor to the second conductor across the insulating layer and to the electrode but the insulating layer blocks the current induced by the MRI system from being transmitted from the first conductor to the second conductor to minimize current on the second conductor during an MRI scan; and

an outer insulating layer extending around the first conductor and the second conductor and defining an exterior of the lead,

wherein each of the insulating layer, the first conductor, the second conductor, and the outer insulating layer overlap each other along at least the portion of the lead.

4. The medical device lead of claim 3, further comprising a pulse generator configured to electrically connect to the second conductor and output the stimulation energy to the second conductor.

5. The medical device lead of claim 3, wherein the insulating layer comprises a variable resistor.

6. The medical device lead of claim 3, wherein the second conductor surrounds the first conductor along at least the portion of the lead.

7. The medical device lead of claim 3, wherein the insulating layer extends only along the portion of the lead.

8. The medical device lead of claim 3, wherein the first conductor surrounds the second conductor along at least the portion of the lead.

9. A medical device comprising:

a pulse generator configured to deliver therapeutic stimulation energy; and

a lead comprising;

a first conductor configured to electrically couple to the pulse generator;

a second conductor coaxial with the first conductor along a portion of the lead;

an electrode that is distal of the portion of the lead, the electrode electrically coupled with the second conductor;

an insulating layer between the first conductor and the second conductor, the insulating layer proximal of the electrode and having a breakdown voltage threshold that is between a first voltage associated with a current induced by an MRI system on the first conductor and a second voltage associated with the therapeutic stimulation energy delivered by the pulse generator, the insulating layer configured to permit conduction of the therapeutic stimulation energy from the first conductor to the second conductor through the insulating layer but block conduction of the current induced by the MRI system from being transmitted from the first conductor to the second conductor through the insulating layer to minimize current on the second conductor during an MRI scan; and

an outer insulating layer extending around the first conductor and the second conductor and defining an exterior of the lead,

wherein each of the insulating layer, the first conductor, the second conductor, and the outer insulating layer overlap each other along at least the portion of the lead.

10. The medical device of claim 9, wherein the insulating layer comprises a variable resistor.

11. The medical device of claim 9, wherein the first conductor surrounds the second conductor along at least the portion of the lead.

12. The medical device of claim 9, wherein the insulating layer extends only along the portion of the lead.

13. The medical device of claim 9, wherein the second conductor surrounds the first conductor along at least the portion the lead.