METHOD AND APPARATUS FOR DETECTION OF LEAD CONDUCTOR ANOMALIES USING DYNAMIC ELECTRICAL PARAMETERS

• US 20110054554A1
• Filed: 08/25/2010
• Published: 03/03/2011
• Est. Priority Date: 08/25/2009
• Status: Active Grant

• Current Assignee: Lamda NU, LLC
• Original Assignee: Lamda NU, LLC
• Inventors: Swerdlow, Charles
• Granted Patent: US 8,825,158 B2
• Time in Patent Office: Days
• US Class Current: 607/5
• 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 comprising the steps of:

a. delivering one or more signals to one or more conductors in a lead,

b. measuring one or more parameters determined by the inductance or capacitance of the one or more conductors,

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 based on a change between the determined and expected relationships.

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 measured parameter is measured from a transmitted signal.

6. The method of claim 1 in which the measured parameter is related to current induced in one conductor by a test signal in a different conductor.

7. The method of claim 1 in which the step of measuring is made in the time-domain.

8. The method of claim 1 in which the step of measuring is made in a transformed domain.

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

10. The method of claim 9 in which the mathematical relationship is a ratio or difference.

11. 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.

12. 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.

13. The method of claim 12 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.

14. The method of claim 12 in which the frequency-dependent parameters are a subset of the following parameters:

impedance, admittance, susceptance, resonance frequency, and phase angle.

15. The method of claim 12 in which the frequency-dependent parameter is the resonance frequency.

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

17. The method of claim 16 in which the base signal is a pacing pulse itself.

18. The method of claim 12 in which the test signal is alternating current at frequency between 1 Hz and 1 GHZ

19. 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.

20. The method of claim 19 that

a. delivers an impulse or transient signal to one or more conductors in a lead attached to a pulse generator,

b. measures values of one or more signal parameters determined by the circuit'"'"'s inductance and/or capacitance,

c. determines if the measured values or values derived from these measured values are within an expected range,

d. detects an anomaly if one or a plurality of a sufficient number of measured values is outside the expected range, and

e. responds to the detection of the anomaly.

21. The method of claim 20 in which one of the measured parameters includes the time for the voltage or current response to the impulse to decline to a predetermined fraction of the initial value.

22. The method of claim 20 in which one of the measured parameters includes the interval between baseline crossings of the voltage or current response to the impulse or the number of baseline crossings in a predetermined period of time.

23. The method of claim 20 in which one of the measured parameters includes the time for the voltage or current response to the impulse to decline to a predetermined fraction of the initial value.

24. The method of claim 20 in which one of the measured parameters includes the interval between baseline crossings of the voltage or current response to the impulse or the number of baseline crossings in a predetermined period of time.

25. The method of claim 1 that

a. delivers a test signal with a known duration to one or more conductors in a lead attached to a pulse generator,

b. measures values of one or more signal parameters determined by the circuit'"'"'s inductance and/or capacitance,

c. determines if the measured values or values derived from these measured values are within an expected range,

e. detects an anomaly if one or a plurality of a sufficient number of measured values is outside the expected range, and

f. responds to the detection of the anomaly.

26. The method of claim 25 in which one of the measured parameters includes the time course of the voltage or current response to the test signal during the pulse.

27. The method of claim 26 in which the measured parameter is the ratio of the voltage or current response at a predetermined fraction of the pulse duration to its value at the end of the pulse.

28. The method of claim 25 in which the test signal is a pacing pulse itself.

29. The methods of claim 3 in which the response is notification of a patient via an alert mechanism.

30. The method of claim 29 in which the alert is an auditory signal, a vibratory signal, or an electronic signal transmitted wirelessly to a receiver.

31. The method of claim 3 in which the response is notification of a physician via an alert mechanism.

32. The method of claim 31 in which the alert is delivered via a remote monitoring system or via a device programmer.

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

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

36. 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.

35. The method of claim 35 in which the intervals are determined by the values of the measured parameters or the variability of these values.

37. An apparatus, comprising

a. a lead including one or more conductors, and

b. a pulse generator connected to the lead, the pulse generator including a lead anomaly detector comprising a lead anomaly measurement subsystem and a lead anomaly analysis subsystem.

38. The apparatus of claim 37, wherein the lead and pulse generator are implanted in a human patient.

39. The apparatus of claim 37 in which the lead anomaly measurement subsystem includes:

a. a signal generator for generating a base signal and multiple test signals at different frequencies and delivering the signals to the one or more of the conductors in the lead, and

b. a subsystem that can measure properties of the conductor during a sequence of test signals at different frequencies.

40. The apparatus of claim 39 in which the properties measured are a subset of the following:

impedance, admittance, susceptance, and phase angle.

41. The apparatus of claim 37 in which the lead anomaly measurement subsystem includes:

a. signal generator for generating one or more transient, impulse test signal and delivering the signals to the one or more of the conductors in the lead, and

b. a subsystem that can measure the time course of the voltage or current response to the impulse signal.

42. The apparatus of claim 37 in which the lead anomaly analysis subsystem includes:

a. a processor that;

i. analyzes measured values,

ii. computes derived values from these measured values,

iii. compares the derived or measured values with a range of expected values, and

iv. analyzes the comparisons to determine if a conductor anomaly is present in the lead; and

b. a subsystem that generates one or more responses if an anomaly is detected.

43. The apparatus of claim 37 in which all components are contained within the pulse generator.

44. The apparatus of claim 37 in which one or more components are contained within a programmer, pacing-system analyzer, or controlling device that is external to the pulse generator.

45. The apparatus of claim 37 in which the lead contains at least one conductor used for delivering one or more stimuli from the pulse generator and a second conductor that is used only for measuring conductor anomalies using the lead anomaly detector and not for stimulation.

46. The apparatus of claim 45 in which the one or more stimuli are pacing stimuli.

47. The apparatus of claim 45 in which the stimulus is a defibrillation pulse.