Lead condition assessment for an implantable medical device

• US 8,190,258 B2
• Filed: 07/07/2009
• Issued: 05/29/2012
• Est. Priority Date: 10/28/2005
• Status: Expired due to Fees

• Current Assignee: LivaNova USA, Inc. (LivaNova Plc)
• Original Assignee: Cyberonics, Inc
• Inventors: Armstrong, Randolph K.
• Primary Examiner(s): Layno, Carl H
• Assistant Examiner(s): SARCIONE, JESSICA LYNN
• Application Number:
  US12/499,001
• Publication Number:
  US 20090270959A1
• Time in Patent Office: 1,057 Days
• Field of Search: 607 27- 29
• US Class Current: 607/27
• CPC Class Codes: A61N 1/3614 based on impedance measurement
• CPC Class Codes: A61N 1/36142 for improving safety
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/3706 Pacemaker parameters stimulation threshold A61N1/371
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

A method, system, and apparatus for performing a lead condition assessment and/or a lead orientation determination associated with an implantable medical device (IMD). A first impedance is determined. The first impedance relates to the impedance relative to a first electrode and a portion of the IMD. A second impedance is determined. The second impedance relates to the impedance relative to a second electrode and the portion of the IMD. The first impedance is compared with the second impedance to determine an impedance difference. A determination is made whether the impedance difference is outside a predetermined tolerance range. Furthermore, artifact measured during impedance measurements or test pulses may be compared to assess lead orientation. An indication of a lead condition error is provided in response to determining that the impedance difference is outside the predetermined tolerance range.

Claims

1. A method for assessing a condition of a lead assembly coupled to an implantable medical device (IMD), the method comprising:

determining by an impedance unit of the IMD or an external unit in communication with the IMD a first impedance relative to a first electrode and a reference electrode;

determining by the impedance unit of the IMD or the external unit in communication with the IMD a second impedance relative to a second electrode and the reference electrode;

comparing by the impedance unit of the IMD or the external unit in communication with the IMD the first impedance to the second impedance to determine an impedance difference;

determining by the impedance unit of the IMD or the external unit in communication with the IMD a position of the first electrode relative to the second electrode based on at least the impedance difference;

determining a third impedance, the third impedance comprising the impedance relative to the first electrode and the second electrode;

determining whether the impedance difference is outside a predetermined tolerance range;

comparing the impedance difference to the third impedance; and

identifying a source of a lead condition error based upon the comparing of the impedance difference to the third impedance, the source comprising at least one of the first electrode, the second electrode, and a physiological impedance.

2. The method of claim 1, wherein the reference electrode comprises a portion of the IMD.

3. The method of claim 1, wherein the first electrode is an EEG sensing electrode.

4. The method of claim 1, further comprising receiving at the IMD a signal prompt from an external source to initiate assessment of a condition of the lead assembly.

5. The method of claim 1, further comprising:

providing an indication of the lead condition error in response to determining that the impedance difference is outside a predetermined tolerance range to a memory of the IMD or a communication unit of the IMD.

6. The method of claim 1, wherein determining the first impedance comprises:

providing a test current signal from the IMD to the first electrode;

measuring a voltage signal across the first electrode and the reference electrode, the voltage signal resulting from the test current signal; and

determining the first impedance based upon the test current signal and the voltage signal.

7. The method of claim 1, wherein determining the second impedance comprises:

providing a test current signal from the IMD to the second electrode;

measuring a voltage signal across the second electrode and the reference electrode, the voltage signal resulting from the test current signal; and

determining the second impedance based upon the test current signal and the voltage signal.

8. The method of claim 1, further comprising:

measuring a first signal artifact relating to the second electrode, the first signal artifact resulting from a test current signal being applied to the first electrode;

measuring a second signal artifact relating to the first electrode, the second signal artifact resulting from a test current signal being applied to the second electrode; and

comparing the first signal artifact to the second signal artifact to determine a signal artifact differential;

wherein determining the position of the first electrode relative to the second electrode is further based on the signal artifact differential.

9. The method of claim 8, further comprising determining which of the first electrode and the second electrodes is positioned distal to the reference electrode based upon the signal artifact differential.

10. The method of claim 1, further comprising determining which of the first electrode and the second electrode is positioned distal to the reference electrode based upon the comparing of the first impedance to the second impedance.

11. The method of claim 10, wherein determining which of the first electrode and the second electrode is positioned distal to the reference electrode comprises determining whether the first impedance is greater than the second impedance.

12. The method of claim 10, wherein determining which of the first electrode and the second electrode is positioned distal to the reference electrode comprises determining whether the positioning of the first and second electrodes is the reverse of an expected positioning.

13. The method of claim 1, wherein the second electrode is an EEG sensing electrode.

14. The method of claim 1, wherein the position of the first electrode is distal or proximal to the reference electrode.

15. The method of claim 1, wherein steps of the method are performed by a processor executing instructions stored on a computer-readable storage device.

16. A method for determining a condition of a lead assembly associated with an implantable medical device (IMD) using an impedance unit of the IMD or an external unit in communication with the IMD, the method comprising:

providing a first test signal from the IMD to a first electrode coupled to the IMD through a first lead;

measuring a first signal artifact relating to a second electrode coupled to the IMD through a second lead, the first signal artifact resulting from the first test signal being applied to the first electrode;

providing a second test signal from the IMD to the second electrode;

measuring a second signal artifact relating to the first electrode, the second signal artifact resulting from the second test signal being applied to the second electrode;

comparing the first signal artifact to the second signal artifact to determine a signal artifact differential;

determining whether the signal artifact differential is outside a predetermined tolerance range; and

providing an indication of a lead condition error in response to determining that the signal artifact differential is outside the predetermined tolerance range to a memory of the IMD or a communication unit of the IMD.

17. The method of claim 16, further comprising determining whether the signal artifact differential relates to at least one of a resistive characteristic, an inductive characteristic and a capacitive characteristic to determine whether the source of the lead condition error relates to at least one of the first electrode, the second electrode, and a physiological impedance.

18. An implantable medical device (IMD) comprising:

a stimulation unit configured to deliver an electrical signal to a patient, wherein the stimulation unit is configured to be coupled to a first electrode, wherein the stimulation unit is configured to be coupled to a second electrode;

an impedance unit configured to determine a first impedance between the first electrode and a reference electrode, wherein the impedance unit is configured to determine a second impedance between the second electrode and the reference electrode, wherein the impedance unit is configured to compare the first impedance to the second impedance to determine an impedance difference;

a processor coupled to the impedance unit and configured to determine a position of the first electrode relative to the second electrode based on at least the impedance difference; and

the impedance unit is further configured to determine a third impedance between the first electrode and the second electrode and to compare the impedance difference to the third impedance, wherein the processor is further configured to identify a source of lead condition error based on the comparison of the impedance difference to the third impedance, the source comprising at least one of the first electrode, the second electrode, and a physiological impedance.

19. The IMD of claim 18, wherein the first electrode is an EEG sensing electrode.

20. The IMD of claim 18, wherein the second electrode is an EEG sensing electrode.