Cardiac activation sequence monitoring for ischemia detection

• US 20060116593A1
• Filed: 03/14/2005
• Published: 06/01/2006
• Est. Priority Date: 11/30/2004
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Meyer, Scott A., Stahmann, Jeffrey E., Zhang, Yi, McCabe, Aaron R., Yu, Yinghong, Ricci, Carlos Alberto, Brockway, Marina, Hopper, Donald I.
• Granted Patent: US 7,797,036 B2
• Time in Patent Office: Days
• US Class Current: 600/512
• 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: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371

Abstract

Cardiac monitoring and/or stimulation methods and systems that provide one or more of monitoring, diagnosing, defibrillation, and pacing. Cardiac signal separation is employed to detect, monitor, track and/or trend ischemia using cardiac activation sequence information. Ischemia detection may involve sensing composite cardiac signals using implantable electrodes, and performing a signal separation that produces one or more cardiac activation signal vectors associated with one or more cardiac activation sequences. A change in the signal vector may be detected using subsequent separations. The change may be an elevation or depression of the ST segment of a cardiac cycle or other change indicative of myocardial ischemia, myocardial infarction, or other pathological change. The change may be used to predict, quantify, and/or qualify an event such as an arrhythmia, a myocardial infarction, or other pathologic change. Information associated with the vectors may be stored and used to track the vectors.

Claims

1. A cardiac method, comprising:

sensing a plurality of composite cardiac signals using a plurality of implantable electrodes;

performing a source separation using the sensed plurality of composite signals;

selecting one or more cardiac signal vectors associated with a portion of one or more cardiac activation sequences based on the source separation; and

detecting a change of the selected one or more cardiac signal vectors using one or both of the selected one or more cardiac signal vectors and the signals associated with the selected one or more cardiac signal vectors.

2. The method of claim 1, wherein the change is indicative of cardiac ischemia.

3. The method of claim 1, wherein the portion of one or more cardiac activation sequences comprises an ST segment and the detected change comprises an elevation or depression of the ST segment.

4. The method of claim 1, comprising predicting an arrhythmia or predicting an increased risk of arrhythmia using the detected change.

5. The method of claim 1, comprising predicting a myocardial infarction using the detected change.

6. The method of claim 1, comprising:

separating at least one cardiac waveform from the plurality of composite signals using the one or more cardiac signal vectors; and

using the at least one cardiac waveform to define a window associated with the ST segment of a cardiac cycle.

7. The method of claim 1, comprising:

providing a window defined by one or more features of the separated cardiac waveform; and

examining the ST-segment of one or more cardiac activation sequences within the window.

8. The method of claim 1, comprising establishing a baseline from the performed source separation, wherein the change is detected using a subsequent source separation.

9. The method of claim 1, wherein selecting the one or more cardiac signal vectors comprises selecting one or more vectors preferentially useful in detecting ischemia.

10. The method of claim 1, wherein detecting the change comprises:

performing a subsequent source separation using a plurality of subsequently detected composite signals from the plurality of cardiac electrodes; and

tracking the selected one or more vectors using the subsequent source separation.

11. The method of claim 1, wherein detecting the change comprises detecting a trend associated with the selected one or more vectors.

12. The method of claim 1, comprising transmitting information associated with the detected change to a patient-external device.

13. The method of claim 1, wherein the change detected comprises one or more of a phase angle change of the one or more cardiac signal vectors, a magnitude change of the one or more cardiac signal vectors, a variance change of the one or more cardiac signal vectors, a power spectral density change of the phase of the one or more cardiac signal vectors, a power spectral density change of the magnitude of the one or more cardiac signal vectors, a trajectory change of the one or more cardiac signal vectors, a temporal profile change of the one or more cardiac signal vectors, a rate of change of phase angle of the one or more cardiac signal vectors, a rate of change of magnitude of the one or more cardiac signal vectors, a rate of change of variance of the one or more cardiac signal vectors, a rate of change of temporal profile of the one or more cardiac signal vectors, a trend of the phase angle of the one or more cardiac signal vectors, a trend of the magnitude of the one or more cardiac signal vectors, a trend of the variance of the one or more cardiac signal vectors, and a trend of the temporal profile of the one or more cardiac signal vectors.

14. A cardiac system, comprising:

a plurality of implantable electrodes configured for sensing a composite signal, thereby providing a plurality of composite signals;

a housing configured for implantation in a patient;

a memory provided in the housing; and

a controller provided in the housing and coupled to the memory and the plurality of implantable electrodes, the controller configured to perform a source separation using the sensed plurality of composite signals, the source separation producing one or more cardiac signal vectors associated with an ST segment of one or more cardiac activation sequences, and to detect ischemia using the one or more cardiac signal vectors.

15. The system of claim 14, wherein the controller predicts one or both of myocardial infarction and cardiac arrhythmia.

16. The system of claim 14, comprising:

a filter window defined by one or more features of a cardiac waveform separated from the plurality of composite signals using the one or more cardiac signal vectors.

17. The method of claim 14, wherein the window is centered on the ST segment of the cardiac cycle.

18. The system of claim 14, comprising a signal processor provided in a patient-external device or system, the signal processor and the controller coupled to respective communication devices to facilitate wireless communication between the signal processor and controller.

19. The system of claim 14, comprising a signal processor provided in a network server system, the signal processor and the controller coupled to respective communication devices to facilitate wireless communication between the signal processor and controller.

20. The system of claim 14, further comprising a lead configured for subcutaneous non-intrathoracic placement in a patient and coupled to the controller, wherein at least one of the plurality of implantable electrodes is supported by the lead.

21. An implantable cardiac device, comprising:

means for sensing a plurality of composite signals using a plurality of implantable cardiac electrodes;

means for performing a source separation using the sensed plurality of composite signals, the source separation producing one or more cardiac signal vectors associated with an ST segment of one or more cardiac activation sequences; and

means for detecting ischemia using the one or more cardiac signal vectors.

22. The device of claim 21, further comprising means for detecting a change in a characteristic of the one or more cardiac signal vectors relative to a baseline.

23. The device of claim 21, further comprising means for predicting one or both of myocardial infarction and cardiac arrhythmia using the change in the characteristic.

24. The device of claim 21, further comprising means for communicating information associated with one or both of the one or more cardiac signal vectors and the one or more cardiac activation sequences to a patient-external device.