Method and apparatus for discriminating cardiac signals in a medical device based on wavelet decomposition analysis

• US 7,894,886 B2
• Filed: 05/04/2007
• Issued: 02/22/2011
• Est. Priority Date: 05/05/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Ghanem, Raja N., Jackson, Troy E.
• Primary Examiner(s): Layno; Carl H
• Assistant Examiner(s): Stice; Paula J
• Application Number:
  US11/744,475
• Publication Number:
  US 20070260152A1
• Time in Patent Office: 1,390 Days
• Field of Search: 600/453, 600509-510, 702/189, 455/313, 435/6
• US Class Current: 600/509
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61N 1/3706 Pacemaker parameters stimulation threshold A61N1/371
• CPC Class Codes: G06F 2218/12 Classification; Matching

Abstract

A method and device for detecting cardiac signals in a medical device that includes decomposing sensed cardiac signals using a wavelet function to form a corresponding wavelet transform, generating a first wavelet representation corresponding to the wavelet transform that is responsive to RR intervals of the sensed cardiac signals, generating a second wavelet representation that is not responsive to RR intervals associated with the sensed cardiac signals, and determining a device failure in response to the first wavelet representation and the second wavelet representation. The method and device may also include decomposing sensed cardiac signals using a wavelet function to form a corresponding wavelet transform, generating a wavelet representation that is not responsive to RR intervals of the sensed cardiac signals, determining RR intervals associated with the sensed cardiac signals, and determining a device failure in response to the first wavelet representation and the determined RR intervals.

Claims

1. A medical device, comprising:

means for sensing cardiac signals;

a cardiac lead, the means for sensing cardiac signals being positioned, at least in part, with respect to the cardiac lead;

means for applying a wavelet function to the sensed cardiac signals to generate a wavelet transform from the sensed cardiac signals using dyadic wavelet decomposition;

means for generating a first wavelet representation from the wavelet transform, the first wavelet representation being responsive to highpass frequency content of the sensed cardiac signals;

means for generating a second wavelet representation from the wavelet transform, the second wavelet representation being responsive to lowpass frequency content of the sensed cardiac signals; and

means for determining a lead failure of the cardiac lead in response to the first wavelet representation and the second wavelet representation.

2. The device of claim 1, wherein the wavelet transform is a Haar wavelet transform and the second wavelet representation corresponds to an approximation sequence.

3. The device of claim 1, wherein the wavelet transform is a Haar wavelet transform and the first wavelet representation corresponds to a detail sequence.

4. The device of claim 1, wherein the sensed cardiac signals are decomposed at a plurality of scales and further comprising:

means for determining approximation coefficients in response to the plurality of scales; and

means for reconstructing the second wavelet representation using predetermined approximation coefficients of the determined approximation coefficients.

5. The device of claim 4, further comprising:

means for determining detail coefficients in response to the plurality of scales; and

means for reconstructing the first wavelet representation using predetermined detail coefficients of the determined detail coefficients.

6. The device of claim 5, wherein the predetermined approximation coefficients correspond to a coarsest scale of the plurality of scales and the detail coefficients correspond to a finest scale of the plurality of scales.

7. The device of claim 6, wherein the approximation coefficients are determined at a fourth scale of the plurality of scales and the detail coefficients are determined at a first scale of the plurality of scales.

8. The device of claim 5, wherein the detail coefficients are determined at a first scale of the plurality of scales to form a first detail sequence and a second scale of the plurality of scales to form a second detail sequence, and wherein the first wavelet representation is reconstructed in response to a sum of the first detail sequence and the second detail sequence.

9. A medical device, comprising:

means for sensing cardiac signals;

a cardiac lead, the means for sensing being positioned, at least in part, with respect to the cardiac lead;

means for applying a wavelet function to the sensed cardiac signals to generate a wavelet transform from the sensed cardiac signals using dyadic wavelet decomposition;

means for generating a wavelet representation from the wavelet transform, the wavelet representation being responsive to lowpass frequency content of the sensed cardiac signals;

means for determining RR intervals associated with the sensed cardiac signals; and

means for determining a lead failure of the cardiac lead in response to the first wavelet representation and the determined RR intervals.

10. The device of claim 9, wherein the wavelet transform is a Haar wavelet transform and the wavelet representation corresponds to an approximation sequence.

11. The device of claim 10, wherein the sensed cardiac signals are decomposed at a plurality of scales and further comprising:

means for determining approximation coefficients in response to the plurality of scales; and

means for reconstructing the wavelet representation using predetermined approximation coefficients of the determined approximation coefficients.

12. The device of claim 10, wherein the predetermined approximation coefficients correspond to a coarsest scale of the plurality of scales.

13. A medical device for sensing a cardiac signal of a patient, comprising:

a cardiac lead;

an electrode positioned with respect to the cardiac lead and configured to sense the cardiac signal;

a processor operatively coupled to the electrode and configured to;

apply a dyadic wavelet function to the cardiac signal to obtain a wavelet transform comprised of a plurality of wavelet values;

generate a low frequency wavelet representation from a plurality of lowpass wavelet values of the plurality of wavelet values of the wavelet transform;

generate a high frequency wavelet representation from a plurality of highpass wavelet values of the plurality of wavelet values of the wavelet transform; and

identify a lead fault in the cardiac lead based, at least in part, on the low frequency wavelet representation and the high frequency wavelet representation.

14. The medical device of claim 13, further comprising a user interface operatively coupled to the processor and configured to display an indication of the fault in the cardiac lead to a user.

15. The medical device of claim 13, further comprising a therapy module operatively coupled to the processor and the electrode and configured to generate a predetermined therapeutic output;

and

wherein the electrode is configured to deliver the therapeutic output to the patient;

wherein the predetermined therapeutic output is adjusted based, at least in part, on the fault in the cardiac lead.

16. The medical device of claim 13 wherein the processor is configured to apply the wavelet function to the cardiac signal to obtain the wavelet transform by being configured to:

apply a wavelet function to the signal function to obtain a subset of the plurality of highpass wavelet values and a subset of the plurality of lowpass wavelet values;

then

apply the wavelet function to an immediately preceding subset of the plurality of lowpass wavelet values to obtain a subsequent subset of the plurality of highpass wavelet values and a subsequent subset of the plurality of lowpass wavelet values;

then

repeat at least once the applying the wavelet function to an immediately preceding subset of the plurality of lowpass wavelet values.

17. The medical device of claim 16 wherein the plurality of highpass wavelet values is at least one subset of the plurality of highpass wavelet values and the plurality of lowpass wavelet values is at least one subset of the plurality of lowpass wavelet values.

18. The medical device of claim 17 wherein the at least one subset of the plurality of highpass wavelet values is a subset of the plurality of highpass wavelet values obtained first in sequence and the at least one subset of the plurality of lowpass wavelet values is a subset of the plurality of lowpass wavelet values obtained last in sequence.

19. The medical device of claim 18 wherein the at least one subset of the plurality of lowpass wavelet values is a fourth subset of lowpass wavelet values obtained in sequence.

20. The medical device of claim 17 wherein the plurality of highpass wavelet values is an aggregate of at least some subsets of the plurality of highpass wavelet values.

21. The medical device of claim 20 wherein the plurality of highpass wavelet values is an aggregate of a subset of the plurality of highpass wavelet values obtained first in sequence and a subset of the plurality of highpass wavelet values obtained second in sequence.