Electrode displacement detection

• US 8,909,338 B2
• Filed: 07/24/2013
• Issued: 12/09/2014
• Est. Priority Date: 07/25/2012
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Thakur, Pramodsingh Hirasingh, Averina, Viktoria A., An, Qi, Hatlestad, John D., Liu, Lili
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US13/949,334
• Publication Number:
  US 20140031888A1
• Time in Patent Office: 503 Days
• Field of Search: 607/28
• US Class Current: 607/28
• CPC Class Codes: A61N 1/37 Monitoring; Protecting

Abstract

Electrode displacement can be detected using a thoracic impedance or conductivity signal. The thoracic impedance or conductivity signal can be filtered to attenuate cardiac contraction (stroke) and respiration components. A fluid status component of the thoracic impedance or conductivity signal can be used to detect a posture-shift related electrode displacement, such as can result from left ventricular/coronary sinus (LV/CS) lead pullback upon a recumbent to upright posture shift.

Claims

1. An apparatus comprising:

a processor circuit, including;

an input, configured to receive an intrathoracic electrical response signal obtained from a subject in response to a delivered subcapture electrical test stimulus, the test stimulus delivered and the response signal obtained during both first and second time periods, in which the subject is in different first and second posture positions during the respective first and second time periods; and

an evaluation circuit, operatively coupled to the input, the evaluation circuit configured to process information about a change in the response signal between the first and second time periods to compute an indication of electrode displacement within the subject between the first and second time periods using a shift between the different first and second posture positions between the respective first and second time periods; and

an output, configured to provide the indication of electrode displacement to a user or an automated process.

2. The apparatus of claim 1, wherein:

the input of the processor circuit is configured to receive a posture-indicative signal obtained from a subject during the first and second time periods;

wherein

the processor is configured to declare an electrode displacement occurrence, between the first and second time periods, in response to a decrease in thoracic impedance exceeding a specified threshold value, within a specified period of time, when the patient shifts from a recumbent posture position to an upright posture position between the first and second time periods.

3. The apparatus of claim 2, wherein the apparatus includes an implantable medical device, configured to be subcutaneously implantable within the subject, and wherein the implantable medical device includes:

the processor circuit;

a posture detector circuit, operatively coupled to the processor circuit, the posture detector circuit configured to provide a posture-indicative signal correlative to a posture position of the subject;

a thoracic impedance detection circuit, configured to be operatively coupled to a left ventricular coronary sinus (LV/CS) lead electrode to obtain a thoracic impedance signal using the LV/CS lead electrode; and

a thoracic fluid detection filter circuit, operatively coupled to the thoracic impedance measurement circuit and the processor circuit, the thoracic fluid detection filter circuit configured to attenuate a cardiac contraction component and a respiration component of the thoracic impedance signal to obtain a DC or near-DC thoracic impedance based indication of thoracic fluid status of the subject; and

wherein the input of the processor circuit is configured to receive the posture-indicative signal, and wherein the processor circuit is configured to declare an electrode displacement occurrence, between the first and second time periods, in response to a decrease in the DC or near-DC thoracic impedance based indication of thoracic fluid status of the subject exceeding a specified threshold value, within a specified period of time, when the posture-indicative signal received from the posture detector circuit indicates that the patient shifts from a recumbent posture position to an upright posture position between the first and second time periods.

4. The apparatus of claim 1,

wherein the intrathoracic electrical response signal includes:

an intrathoracic electrical first response signal obtained using an electrode located on a first intravascular lead; and

an intrathoracic electrical second response signal obtained using an electrode located on a separate second intravascular lead;

wherein the evaluation circuit is configured to detect a change in the first response signal between the first and second time periods, and to detect a change in the second response signal between the first and second time periods, and to evaluate a comparison between the change in the first response signal and the change in the second response signal to compute the indication of electrode displacement within the subject between the first and second time periods.

5. The apparatus of claim 4,

wherein the intrathoracic electrical response signal includes an intrathoracic electrical third response signal obtained using an electrode located on a third intravascular lead, separate from the first and second intravascular leads;

wherein the evaluation circuit is configured to detect a change in the third response signal between the first and second time periods, and evaluating a pairwise comparison between the change in the first response signal, the change in the second response signal, and the change in the third response signal to compute the indication of electrode displacement within the subject between the first and second time periods, wherein the indication of electrode displacement is lead-specific.

6. The apparatus of claim 1, wherein:

the input of the processor circuit is configured to receive a posture-indicative signal obtained from a subject during the first and second time periods; and

the evaluation circuit is configured to declare an electrode displacement occurrence, between the first and second time periods, in response to the posture-indicative signal and the response signal between the first and second time periods.

7. The apparatus of claim 6, wherein:

the input of the processor circuit is configured to receive a posture-indicative signal obtained from a subject during the first and second time periods; and

the processor is configured declare an electrode displacement occurrence, between the first and second time periods, in response to a correlation between the posture-indicative signal and the response signal between the first and second time periods.

8. The apparatus of claim 1, wherein the evaluation circuit is configured to compute a functional relationship between posture and the electrical response signal between the first and second time periods, and to evaluate the functional relationship to compute an indication of electrode displacement within the subject between the first and second time periods.

9. The apparatus of claim 1, comprising:

a posture detector circuit, operatively coupled to the processor circuit, the posture detector circuit configured to provide a posture-indicative signal correlative to a posture position of the subject;

a thoracic conductivity detection circuit, configured to be operatively coupled to an electrode and of providing a thoracic conductivity signal; and

a thoracic fluid detection filter circuit, operatively coupled to the thoracic conductivity detection circuit, the thoracic fluid detection filter circuit configured to attenuate a cardiac contraction component and a respiration component of the thoracic impedance signal to obtain a DC or near-DC thoracic conductivity signal indicative of a thoracic fluid status of the subject; and

wherein the processor circuit is configured to use the posture-indicative signal and the thoracic conductivity signal for evaluating the thoracic conductivity signal in response to a change in posture position of the subject to compute an indication of electrode displacement within the subject.

10. The apparatus of claim 9, further comprising:

a frequency-selective filter circuit, operatively coupled to the thoracic fluid detection circuit to receive the DC or near-DC thoracic conductivity based thoracic conductivity signal, the filter circuit including a filter edge frequency configured to discriminate between posture-induced electrode displacement and posture-induced thoracic fluid shift.

11. The apparatus of claim 10, further comprising:

a correlation circuit, including a first correlation circuit input operatively coupled to the thoracic fluid detection circuit to receive the DC or near-DC thoracic conductivity based thoracic conductivity signal, a second correlation circuit input operatively coupled to an output of the frequency-selective filter circuit, and configured to compute a correlation between signals at the first and second correlation circuit inputs to compute an indication of electrode displacement within the subject.

12. The apparatus of claim 1, wherein the response signal is obtained from bipolar electrodes.

13. The apparatus of claim 1, wherein the response signal includes multiple response signals obtained from different sets of electrodes that are longitudinally displaced from each other along a length of an intravascular lead.

14. A tangible non-transitory device readable medium including instructions that, when performed by the device, cause the device to perform the following acts:

receiving an intrathoracic electrical response signal obtained from a subject in response to a delivered subcapture electrical test stimulus, the test stimulus delivered and the response signal obtained during both first and second time periods, in which the subject is in different first and second posture positions during the respective first and second time periods; and

processing information about a change in the response signal between the first and second time periods to compute an indication of electrode displacement within the subject between the first and second time periods using a shift between the different first and second posture positions between the respective first and second time periods; and

providing the indication of electrode displacement to a user or automated process.

15. The tangible non-transitory device readable medium of claim 14, including instructions that, when performed by the device, cause the device to perform the following acts:

receiving a posture-indicative signal obtained from the subject during the first and second time periods; and

declaring an electrode displacement occurrence, between the first and second time periods, in response to a decrease in thoracic impedance exceeding a specified threshold value, within a specified period of time, when the patient shifts from a recumbent posture position to an upright posture position between the first and second time periods.

16. The tangible non-transitory device readable medium of claim 15, including instructions that, when performed by the device, cause the device to perform the following acts:

receiving thoracic impedance signal obtained using a left ventricular/coronary sinus (LV/CS) lead electrode; and

attenuating a cardiac contraction component and a respiration component of the thoracic impedance signal to obtain a DC or near-DC thoracic impedance based indication of thoracic fluid status of the subject; and

declaring an electrode displacement occurrence, between the first and second time periods, in response to a decrease in the DC or near-DC thoracic impedance based indication of thoracic fluid status of the subject exceeding a specified threshold value, within a specified period of time, when the posture-indicative signal received from the posture detector circuit indicates that the patient shifts from a recumbent posture position to an upright posture position between the first and second time periods.

17. The tangible non-transitory device readable medium of claim 16, including instructions that, when performed by the device, cause the device to perform the following acts:

receiving the intrathoracic electrical response signal, including receiving;

an intrathoracic electrical first response signal obtained using an electrode located on a first intravascular lead; and

an intrathoracic electrical second response signal obtained using an electrode located on a separate second intravascular lead;

detecting a change in the first response signal between the first and second time periods;

detecting a change in the second response signal between the first and second time periods; and

evaluating a comparison between the change in the first response signal and the change in the second response signal to compute the indication of electrode displacement within the subject between the first and second time periods.

18. The tangible non-transitory device readable medium of claim 17, including instructions that, when performed by the device, cause the device to perform the following acts:

receiving the intrathoracic electrical response signal, including receiving an intrathoracic electrical third response signal obtained using an electrode located on a third intravascular lead, separate from the first and second intravascular leads;

detecting a change in the third response signal between the first and second time periods; and

evaluating a pairwise comparison between the change in the first response signal, the change in the second response signal, and the change in the third response signal to compute the indication of electrode displacement within the subject between the first and second time periods, wherein the indication of electrode displacement is lead-specific.

19. The tangible non-transitory device readable medium of claim 14, including instructions that, when performed by the device, cause the device to perform the following acts:

receiving a posture-indicative signal obtained from the subject during the first and second time periods; and

declaring an electrode displacement occurrence, between the first and second time periods, in response to the posture-indicative signal and the response signal between the first and second time periods.

20. The tangible non-transitory device readable medium of claim 19, including instructions that, when performed by the device, cause the device to perform the following acts:

declaring an electrode displacement occurrence, between the first and second time periods, in response to a computed correlation between the posture-indicative signal and the response signal between the first and second time periods.