SYSTEMS AND METHODS FOR EMPLOYING MULTIPLE FILTERS TO DETECT T-WAVE OVERSENSING AND TO IMPROVE TACHYARRHYTHMIA DETECTION WITHIN AN IMPLANTABLE MEDICAL DEVICE

• US 20090018595A1
• Filed: 07/11/2007
• Published: 01/15/2009
• Est. Priority Date: 07/11/2007
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Boileau, Peter, Florio, Joseph J., Bharmi, Rupinder, Bornzin, Gene A., Snell, Jeffery D.
• Granted Patent: US 8,504,144 B2
• Time in Patent Office: Days
• US Class Current: 607/14
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/346 Analysis of electrocardiograms
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

Techniques are described for detecting tachyarrhythmia and also for preventing T-wave oversensing using a narrowband bradycardia filter in combination with a narrowband tachycardia filter. In some embodiments, a separate wideband filter is also exploited. In one illustrative example, ventricular tachycardia (VT) is detected by: detecting a preliminary indication of VT using signals filtered by the bradycardia filter and, in response, confirming the detection of VT using signals filtered by the tachycardia filter. That is, the bradycardia filter, traditionally used only to detect bradycardia, is additionally used to provide a preliminary indication of VT. The tachycardia filter is then activated to confirm the detection of VT before therapy is delivered. In this manner, the tachycardia filter need not run continuously, but is instead activated only when there is some indication of possible VT, and hence power is saved. Numerous other exemplary techniques are set forth herein for arrhythmia detection and for T-wave oversensing detection.

Claims

1. In an implantable medical device for processing electrical cardiac signals sensed via leads implanted within the heart of a patient, wherein the device has a first filter operative to substantially eliminate signals having frequencies associated with ventricular repolarization events while retaining signals having frequencies associated with at least some ventricular depolarization events and a second filter operative to pass signals having frequencies associated with ventricular depolarization events and ventricular repolarization events, a method comprising:

sensing electrical cardiac signals within the patient;

selectively filtering the signals using the first filter;

selectively filtering the signals using the second filter; and

detecting tachyarrhythmia within the patient using signals filtered by the first filter in combination with signals filtered by the second filter.

2. The method of claim 1 wherein detecting tachyarrhythmia using signals filtered by the first filter in combination with signals filtered by the second filter includes:

detecting a preliminary indication of tachyarrhythmia using signals filtered by the first filter; and

in response, confirming the detection of tachyarrhythmia using signals filtered by the second filter.

3. The method of claim 2 wherein detecting the preliminary indication of tachyarrhythmia using signals filtered by the first filter includes:

activating the first filter to filter ventricular channel signals sensed via the leads;

analyzing the ventricular channel signals filtered by the first filter to detect the preliminary indication of ventricular tachyarrhythmia.

4. The method of claim 1 wherein detecting tachyarrhythmia within the patient includes:

filtering ventricular channel signals sensed via the leads using the second filter while also filtering ventricular channel signals sensed via the leads using the first filter; and

comparing the ventricular channel signals filtered by the second filter and the first filter to detect ventricular tachyarrhythmia.

5. The method of claim 1 wherein detecting tachyarrhythmia within the patient includes:

filtering ventricular channel signals sensed via the leads using the second filter; and

detecting a preliminary indication of tachyarrhythmia using signals filtered by the second filter; and

in response, confirming the detection of tachyarrhythmia by comparing additional signals filtered by the second filter with additional signals filtered by the first filter.

6. The method of claim 1 wherein detecting tachyarrhythmia using signals filtered by the first filter in combination with signals filtered by the second filter includes:

comparing ventricular channel signals filtered by the first filter with ventricular channel signals filtered by the second filter to distinguish between true ventricular depolarization events and false ventricular depolarization events; and

detecting tachyarrhythmia based on the true ventricular depolarization events.

7. The method of claim 1 wherein the device additionally includes a wideband filter having a substantially wider bandwidth than bandwidths of the first and second filters and wherein the step of detecting tachyarrhythmia uses signals filtered by the wideband filter in combination with signals filters by the first and second filters.

8. The method of claim 1 further including delivering therapy in response to the tachyarrhythmia.

9. The method of claim 1 wherein the first filter is a bradycardia filter and wherein the second filter is a tachycardia filter and wherein detecting tachyarrhythmia within the patient is performed using signals filtered by the bradycardia filter in combination with signals filtered by the tachycardia filter.

10. The method of claim 1 wherein the first filter has a passband beginning at about 20 Hz and wherein the second filter has a passband beginning at about 10 Hz and wherein detecting tachyarrhythmia within the patient is performed using signals filtered by the first filter having the passband beginning at about 20 Hz in combination with signals filtered by the second filter having the passband beginning at about 10 Hz.

11. A tachyarrhythmia detection system for use in an implantable medical device having filters for filtering electrical cardiac signals sensed via leads implanted within the heart of a patient, the system comprising:

a first filter operative to substantially eliminate signals having frequencies associated with ventricular repolarization events while retaining signals having frequencies associated with at least some ventricular depolarization events;

a second filter operative to pass signals having frequencies associated with ventricular depolarization events and ventricular repolarization events; and

a combined first filter/second filter-based arrhythmia detection system operative to detect tachyarrhythmia within the patient using signals filtered by the first filter in combination with the signals filtered by the second filter.

12. The system of claim 11 wherein the combined first filter/second filter-based detection system includes:

a first filter-based preliminary detection unit operative to detect a preliminary indication of tachyarrhythmia using signals filtered by the first filter; and

a second filter-based confirmation unit to then confirm the detection of tachyarrhythmia using signals filtered by the second filter.

13. The system of claim 11 wherein the combined first filter/second filter-based detection system includes a comparison unit operative to compare the ventricular channel signals filtered by the second filter and the first filter to detect ventricular tachyarrhythmia.

14. The system of claim 11 wherein the combined first filter/second filter-based detection system includes:

a second filter-based preliminary detection unit operative to detect a preliminary indication of tachyarrhythmia using signals filtered by the second filter; and

a duel filter-based confirmation unit to then confirm the detection of tachyarrhythmia using signals filtered by the first filter and the second filter.

15. The system of claim 11 wherein the combined first filter/second filter-based detection system includes:

a second filter-based preliminary detection unit operative to detect a preliminary indication of tachyarrhythmia using signals filtered by the first filter; and

a second filter-based confirmation unit operative to detect oversensing of ventricular repolarization events by the second filter and to confirm the detection of tachyarrhythmia only in the absence of oversensing of ventricular repolarization events.

16. The system of claim 11

wherein the implantable device additionally includes a wideband filter having a substantially wider bandwidth than bandwidths of the first and second filters;

and

wherein the combined first filter/second filter-based detection system includes a comparison unit operative to detect tachyarrhythmia using signals filtered by the wideband filter in combination with signals filters by the first and second filters.

17. A tachyarrhythmia detection system for use in an implantable medical device having filters for filtering electrical cardiac signals sensed via leads implanted within the heart of a patient, the system comprising:

means for sensing electrical cardiac signals within the patient;

first means for filtering the signals to substantially eliminate signals having frequencies associated with ventricular repolarization events while retaining signals having frequencies associated with at least some ventricular depolarization events;

second means for filtering the signals to pass signals having frequencies associated with ventricular depolarization events and ventricular repolarization events; and

means for detecting tachyarrhythmia within the patient by comparing the first means for filtering and the second means for filtering.