Method and apparatus for detection of lead conductor anomalies using dynamic electrical parameters

• US 8,825,158 B2
• Filed: 08/25/2010
• Issued: 09/02/2014
• Est. Priority Date: 08/25/2009
• Status: Active Grant

• Current Assignee: Lamda NU, LLC
• Original Assignee: Lamda NU, LLC
• Inventors: Swerdlow, Charles
• Primary Examiner(s): STOKLOSA, JOSEPH A
• Application Number:
  US12/868,056
• Publication Number:
  US 20110054554A1
• Time in Patent Office: 1,469 Days
• Field of Search: 607 27- 29
• US Class Current: 607/27
• CPC Class Codes: A61N 1/0504 Subcutaneous electrodes
• CPC Class Codes: A61N 1/056 Transvascular endocardial electrode systems
• CPC Class Codes: A61N 1/36142 for improving safety
• CPC Class Codes: A61N 1/3706 Pacemaker parameters stimulation threshold A61N1/371
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting

Abstract

A method and apparatus to detect anomalies in the conductors of leads attached to implantable medical devices based on the dynamical electrical changes these anomalies cause. In one embodiment, impedance is measured for weak input signals of different applied frequencies, and a conductor anomaly is detected based on differences in impedance measured at different frequencies. In another embodiment, a transient input signal is applied to the conductor, and an anomaly is identified based on parameters related to the time course of the voltage or current response, which is altered by anomaly-related changes in capacitance and inductance, even if resistance is unchanged. The method may be implemented in the implantable medical device or in a programmer used for testing leads.

Claims

1. A method for determination of anomalies in a lead implanted within a patient, the method comprising the steps of:

a. delivering one or more signals at a subset of frequencies to one or more conductors in the implanted lead,

b. measuring two or more frequency dependent parameters determined by inductance or capacitance of the implanted lead,

c. determining at least one relationship between two or more measured parameters,

d. comparing the at least one relationship to a predetermined expected range of relationships, and

e. detecting an anomaly in the implanted lead based on a change between the determined and expected relationships, wherein the anomaly can be any of a partial conductor fracture, a complete conductor fracture, a partial insulation failure, and a complete insulation failure.

2. The method of claim 1 in which the lead is attached to a pulse generator in an implantable cardioverter defibrillator (ICD) or a pacemaker, and wherein the lead is implanted intracardiac, intravascularly, or subcutaneously.

3. The method of claim 2, further comprising the step of responding to the detection of the anomaly.

4. The method of claim 1 in which the measured parameter is measured from a reflected signal.

5. The method of claim 1 in which the at least one relationship is a mathematical relationship.

6. The method of claim 5 in which the mathematical relationship is a ratio or difference.

7. The method of claim 1 in which:

a. one or more derived numerical results are calculated for each comparison, and

b. the presence of an anomaly is detected by comparison of the values of the derived numerical results to a range of expected values.

8. The method of claim 1, that:

a. delivers a base signal and one or more test signals at different frequencies to one or more conductors in a lead attached to a pulse generator,

b. measures values of frequency-dependent parameters of the conductors during a base signal and one or more test signals with different test-signal frequencies,

c. determines a relationship or relationships between or among two or more of the measured values,

d. compares the relationships to an expected range of relationships,

e. detects an anomaly based on a change between the determined and expected relationships, and

f. responds to the detection of the anomaly.

9. The method of claim 8 in which:

a. the parameter is determined using a base signal and a test signal at a different frequency, and

b. the relationship is the ratio of the value at these two frequencies.

10. The method of claim 8 in which the frequency-dependent parameters are a subset of the following parameters:

complex impedance including real and imaginary components, admittance, susceptance, resonance frequency, and phase angle.

11. The method of claim 8 in which the frequency-dependent parameter is the resonance frequency.

12. The method of claim 8 in which the base signal is a single pulse.

13. The method of claim 12 in which the base signal is a pacing pulse itself.

14. The method of claim 8 in which the test signal is alternating current at frequency between 1 Hz and 1 GHZ.

15. The method of claim 1 in which a single test signal is delivered to a circuit including one or more conductors in a lead attached to a pulse generator.

16. The method of claim 3 in which the response is to change one or more of the pulse generator'"'"'s programmed settings.

17. The method of claim 1 in which test signals are delivered at intervals on an automated, periodic basis.

18. The method of claim 17 in which the intervals are determined by the values of the measured parameters or the variability of these values.

19. The method of claim 1 in which

a. the variability of the measured values are determined, and

b. the presence of a conductor anomaly is detected if the variability exceeds a predetermined value.