Implantable medical device system and method with signal quality monitoring and response

• US 7,496,409 B2
• Filed: 03/29/2006
• Issued: 02/24/2009
• Est. Priority Date: 03/29/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Vitense, Holly S., Greenhut, Saul E., Stadler, Robert W.
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US11/392,065
• Publication Number:
  US 20070239220A1
• Time in Patent Office: 1,063 Days
• Field of Search: 607/116, 600/509, 600/521
• US Class Current: 607/116
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61N 1/05 for implantation or insertion into the body, e.g. heart electrode A61N1/06 takes precedence
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control

Abstract

An implantable medical device system and method are provided for monitoring the quality of signals sensed by a subcutaneously implanted device using subcutaneous electrodes. In one embodiment, the method includes selecting one or more sensing vectors; sensing signals from selected sensing vectors, determining a signal quality metric in response to a sensed signal, comparing the signal quality metric to a predetermined threshold, and generating a loss of signal quality response in response to the signal quality crossing the threshold.

Claims

1. An implantable medical device system, comprising:

a plurality of subcutaneous electrodes forming a plurality of subcutaneous sensing vectors;

a sensing circuit for receiving signals from the plurality of subcutaneous sensing vectors;

a processor for determining a first signal quality metric in response to a first subcutaneous sensing vector signal, comparing the first signal quality metric to a predetermined threshold, and generating a first loss of signal quality response in response to the first signal quality metric crossing the threshold

wherein determining the first signal quality metric comprises calculation of a characteristic of the vector signal, the characteristic corresponding to the quality of the vector signal for providing accurate separation of a sinus rhythm of a patient and a tachyarrhythmia of the patient.

2. The system of claim 1 wherein the processor further determines a second signal quality metric for a second subcutaneous sensing vector signal, compares the second signal quality metric to the predetermined threshold, and generates a second loss of signal quality response in response to both the first and the second signal quality metric crossing the threshold.

3. The system of claim 2 wherein the predetermined threshold includes a first threshold applied to the first signal quality metric and a second threshold applied to the second signal quality metric.

4. The system of claim 1 wherein the first loss of signal quality response includes any of:

generating an alert signal, selecting a different sensing vector, suspending a device function, adjusting a device function, and increasing the frequency of determining the first signal quality metric.

5. The system of claim 4 further including an implantable medical device telemetry circuit and an external device adapted for bidirectional communication with the telemetry circuit and wherein generating the alert signal includes transmitting a signal between the implantable medical device telemetry circuit and the external device.

6. The system of claim 4 further including an alert module and wherein generating the alert signal includes generating a sensory stimulus perceivable by the patient.

7. The system of claim 1 further including a communications module adapted for communicating with a communications network and wherein the first loss of signal quality response includes transferring a signal to the communications network.

8. The system of claim 1 wherein the plurality of subcutaneous electrodes includes electrodes carried by a subcutaneous lead.

9. The system of claim 1 wherein the received signals include cardiac electrogram signals.

10. The system of claim 1 wherein the determining the signal quality includes determining any of a signal amplitude, a signal-to-noise ratio, a total signal energy, a signal slope, a signal frequency, a frequency of sensing at a minimum sensing threshold, a frequency of short intervals, a cross-correlation metric, a channel consistency metric, and an inter-electrode impedance.

11. The system of claim 1 wherein the processor further compares the first signal quality metric to a low-level response threshold and generates a low-level loss of signal quality response in response to the signal quality metric crossing the low-level response threshold.

12. The system of claim 1 wherein the processor further determines a vector selection metric for each of the plurality of sensing vectors, and selects one or more sensing vectors based on a comparison of the vector selection metric to a vector selection threshold.

13. A method for use in a subcutaneously implanted medical device system, comprising:

selecting a plurality of subcutaneous sensing vectors from a plurality of subcutaneous electrodes;

sensing signals from the selected plurality of subcutaneous sensing vectors;

determining a first signal quality metric in response to a first selected subcutaneous sensing vector signal, comparing the first signal quality metric to a predetermined threshold, and generating a first loss of signal quality response in response to the first signal quality metric crossing the threshold

wherein determining the first signal quality metric comprises calculation of a characteristic of the vector signal, the characteristic corresponding to the quality of the vector signal for providing accurate separation of a sinus rhythm of a patient and an arrhythmia of the patient.

14. The method of claim 13 further comprising determining a second signal quality metric for a second selected subcutaneous sensing vector signal, comparing the second signal quality metric to the predetermined threshold, and generating a second loss of signal quality response in response to both the first and the second signal quality metric crossing the threshold.

15. The method of claim 14 wherein the predetermined threshold includes a first threshold applied to the first signal quality metric and a second threshold applied to the second signal quality metric.

16. The method of claim 13 wherein the first loss of signal quality response includes any of:

generating an alert signal, selecting a different sensing vector, suspending a device function, adjusting a device function, and increasing the frequency of determining the first signal quality metric.

17. The method of claim 16 further wherein generating the alert signal includes transmitting a signal between an implantable medical device telemetry circuit and an external device.

18. The method of claim 16 wherein the alert signal includes generating a generating a sensory stimulus perceivable by the patient.

19. The method of claim 13 wherein the first loss of signal quality response includes transferring an alert signal to a communications network.

20. The method of claim 13 wherein the plurality of subcutaneous electrodes includes electrodes carried by a subcutaneous lead.

21. The method of claim 13 wherein the sensed signals include cardiac electrogram signals.

22. The method of claim 13 wherein determining the signal quality metric includes determining any of a signal amplitude, signal-to-noise ratio, a total signal energy, a signal slope, and a low slope content.

23. The method of claim 13 further including comparing the first signal quality metric to a low-level response threshold and generating a low-level loss of signal quality response in response to the signal quality metric crossing the low-level response threshold.

24. The method of claim 13 further comprising determining a vector selection metric for each of the plurality of sensing vectors, selecting one or more sensing vectors based on a comparison of the vector selection metric to a vector selection threshold.

25. A computer readable medium for storing a set of instructions which cause a subcutaneously implanted medical device system to:

sense signals from a plurality of subcutaneous sensing vectors formed between a plurality of subcutaneous electrodes;

determine a signal quality metric for each of the subcutaneous sensing vector signals;

compare the signal quality metric for each subcutaneous sensing vector to a threshold; and

provide a loss of signal quality response in response to the signal quality metric crossing the threshold

wherein determining the signal quality metric comprises calculation of a characteristic of the vector signal, the characteristic corresponding to the quality of the vector signal for providing accurate separation of a sinus rhythm of a patient and an arrhythmia of the patient.