SWITCHED SAFETY PROTECTION CIRCUIT FOR AN AIMD SYSTEM DURING EXPOSURE TO HIGH POWER ELECTROMAGNETIC FIELDS

• US 20130289666A1
• Filed: 05/20/2013
• Published: 10/31/2013
• Est. Priority Date: 12/17/2008
• Status: Active Grant

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Inventors: Johnson, Robert Shawn, Dabney, Warren S., Stevenson, Robert A., Williams, Christopher Michael, Moschiano, Holly Noelle, Brainard, Scott
• Granted Patent: US 9,037,258 B2
• Time in Patent Office: Days
• US Class Current: 607/63
• CPC Class Codes: A61B 2017/00911 for fields applied by a magnetic resonance imaging system
• CPC Class Codes: A61B 2018/00839 Bioelectrical parameters, e.g. ECG, EEG
• CPC Class Codes: A61B 2090/374 NMR or MRI
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• 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
• CPC Class Codes: A61N 1/37512 Pacemakers
• CPC Class Codes: G01R 33/285 Invasive instruments, e.g. catheters or biopsy needles, specially adapted for tracking, guiding or visualization by NMR
• CPC Class Codes: H03H 7/0107 Non-linear filters
• CPC Class Codes: H03H 7/1758 Series LC in shunt or branch path H03H7/1791 takes precedence
• CPC Class Codes: H03H 7/1766 Parallel LC in series path H03H7/1783 takes precedence

Abstract

An energy management system that facilitates the transfer of high frequency energy induced on an implanted lead or a leadwire includes an energy dissipating surface associated with the implanted lead or the leadwire, a diversion or diverter circuit associated with the energy dissipating surface, and at least one switch disposed between the diversion circuit and the AIMD electronics for diverting energy in the implanted lead or the leadwire through the diversion circuit to the energy dissipating surface. The switch may comprise a single or multi-pole double or single throw switch. The diversion circuit may be either a high pass filter or a low pass filter.

Claims

1. An implantable medical device, comprising:

a) a thermally or electrically conductive housing for the implantable medical device containing tissue-stimulating or biological-sensing circuits;

b) a feedthrough terminal disposed in the conductive housing;

c) a first conductive path electrically coupled between the feedthrough terminal and the tissue-stimulating or biological-sensing circuits;

d) a switch electrically coupled in series along the first conductive path, the switch comprising a first throw end, a second throw end and a pole end, wherein the pole end is permanently electrically coupled to the tissue-stimulating or biological-sensing circuit and the first throw end is permanently connected to the feedthrough terminal; and

e) a second conductive path permanently electrically coupled between the second throw end of the switch and the conductive housing;

f) wherein the switch is configured to be selectively actuatable in response to a programmable telemetry signal to either connect the pole to the first throw end or to connect the pole to the second throw end.

2. The implantable medical device of claim 1, wherein in a normal operating mode the pole is connected to the first throw end.

3. The implantable medical device of claim 2, wherein in an MRI mode the pole is connected to the second throw end.

4. The implantable medical device of claim 1, including a third conductive path coupled at a first end anywhere along the first conductive path between the feedthrough terminal and the first throw end of the switch, and coupled at a second end to the conductive housing, wherein a frequency variable diverter element is coupled in series along the third conductive path.

5. The implantable medical device of claim 4, wherein the frequency variable diverter element comprises a low pass filter, a capacitor, a feedthrough capacitor, an LC trap filter, a Pi filter, a T filter, an LL filter or an “

n”

element filter.

6. The implantable medical device of claim 1, wherein the switch comprises a multi-pole double throw switch.

7. The implantable medical device of claim 1, wherein the switch comprises a MEMS switch, a mechanical switch, a reed switch, an electronic switch, a programmable switch, an automatically actuated switch, a Hall Effect switch, a field effect transistor (FET) switch or a PIN diode.

8. The implantable medical device of claim 1, wherein the tissue-stimulating or biological-sensing circuits comprise non-linear circuit elements, over-voltage circuit elements, transient voltage suppression diodes, Transorbs, AIMD sensing circuits or active implantable medical device therapy delivery circuits.

9. The implantable medical device of claim 4, wherein the frequency variable diverter element comprises a high pass filter.

10. The implantable medical device of claim 9, wherein the high pass filter comprises a capacitor or a resistor in series with a capacitor.

11. The implantable medical device of claim 4, wherein the frequency variable diverter element comprises a plurality of LC trap filters, each LC trap filter being resonant at a different MRI RF pulsed frequency.

12. The implantable medical device of claim 1, wherein the implantable medical device comprises an implantable hearing device, a neurostimulator, a brain stimulator, a cardiac pacemaker, a left ventricular assist device, an artificial heart, a drug pump, a bone growth stimulator, a urinary incontinence device, a spinal, cord stimulator, an anti-tremor stimulator, an implantable cardioverter defibrillator, a congestive heart failure device, a probe, a catheter or a cardio resynchronization therapy device.

13. The implantable medical device of claim 4, wherein the third conductive path is disposed within the conductive housing.

14. The implantable medical device of claim 4, wherein third conductive path is disposed within a header block which is attached to the conductive housing.

15. The implantable medical device of claim 14, including an EMI shield conductively coupled to the conductive housing and coaxially extending about the third conductive path in non-conductive relation thereto.

16. An implantable medical device, comprising:

a) a thermally or electrically conductive housing for the implantable medical device containing tissue-stimulating or biological-sensing circuits;

b) a feedthrough terminal disposed in the conductive housing;

a first conductive path electrically coupled between the feedthrough terminal and the tissue-stimulating or biological-sensing circuits;

d) a switch electrically coupled in series along the first conductive path, the switch comprising a first throw end, a second throw end and a pole end, wherein the pole end is permanently electrically coupled to the tissue-stimulating or biological-sensing circuit and the first throw end is permanently connected to the feedthrough terminal; and

e) a second conductive path permanently electrically coupled between the second throw end of the switch and the conductive housing;

f) wherein the switch is configured to be selectively actuatable in response to a programmable telemetry signal to either connect the pole to the first throw end in a normal operating mode or to connect the pole to the second throw end in an MRI mode; and

g) a third conductive path coupled at a first end anywhere along the first conductive path between the feedthrough terminal and the first throw end of the switch, and coupled at a second end to the conductive housing, wherein a frequency variable diverter element is coupled in series along the third conductive path.

17. An implantable medical device, comprising:

a) a thermally or electrically conductive housing for the implantable medical device containing tissue stimulating or biological-sensing circuits;

b) a feedthrough terminal disposed in the conductive housing;

c) a first conductive path electrically coupled between the feedthrough terminal and the tissue-stimulating or biological-sensing circuits;

d) a switch electrically coupled in series along the first conductive path, the switch comprising a first throw end, a second throw end and a pole end, wherein the pole end is permanently electrically coupled to the tissue-stimulating or biological-sensing circuit and the first throw end is permanently connected to the feedthrough terminal; and

e) a second conductive path permanently electrically coupled between the second throw end of the switch and the conductive housing;

f) wherein the switch is configured to be actuatable in response to a magnetic resonance B₀ field sensor that, in the absence of a static magnetic field, electrically connects the pole to the first throw end, and in the presence of a static magnetic field, electrically connects the pole to the second throw end.