METHOD AND APPARATUS FOR DETECTING ARRHYTHMIAS IN A MEDICAL DEVICE

• US 20070239050A1
• Filed: 04/28/2006
• Published: 10/11/2007
• Est. Priority Date: 03/29/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Zhang, Xusheng, Stadler, Robert, Ghanem, Raja
• Granted Patent: US 7,742,812 B2
• Time in Patent Office: Days
• US Class Current: 600/512
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/341 Vectorcardiography [VCG]
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• 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 5/7239 using differentiation including higher order derivatives
• 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 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal
• CPC Class Codes: Y10S 128/902 Biological signal amplifier

Abstract

A method of detecting a cardiac event that includes sensing cardiac signals from a plurality of electrodes, determining rates of change of the sensed cardiac signals, and determining a range of the sensed cardiac signals. The sensed cardiac signals are detected as being associated with the cardiac event in response to the determined rates of change and the determined range.

Claims

1. A method of detecting a cardiac event, comprising:

sensing cardiac signals from a plurality of electrodes;

determining rates of change in the sensed cardiac signals;

determining a range of the sensed cardiac signals;

detecting the sensed cardiac signals as being associated with the event in response to the determined rates of change and the determined range.

2. The method of claim 1, wherein determining rates of change of the sensed cardiac signals comprises:

determining a rate of change threshold in response to the sensed cardiac signals; and

determining a number of the rates of change being less than the rate of change threshold.

3. The method of claim 1, wherein determining a range of the sensed cardiac signals comprises determining a difference between a mean frequency and a fundamental frequency of the sensed cardiac signals.

4. The method of claim 2, wherein detecting the sensed cardiac signals comprises:

determining whether the number of the rates of change that are less than the rate of change threshold is less than a first boundary; and

determining whether the range is less than a second boundary different from the first boundary.

5. A method of detecting a cardiac event, comprising:

sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector;

determining first rates of change in the cardiac signals sensed by the first sensing vector over a predetermined sensing window;

determining second rates of change in the cardiac signals sensed by the second sensing vector over the predetermined sensing window;

determining a first range of the cardiac signals sensed by the first sensing vector over the predetermined sensing window;

determining a second range of the cardiac signals sensed by the second sensing vector over the predetermined sensing window; and

detecting the sensed cardiac signals as being associated with the event in response to the first rates of change, the second rates of change, the first range and the second range.

6. The method of claim 5, wherein determining the first rates of change and the second rates of change comprises:

determining a rate of change threshold in response to the sensed cardiac signals; and

determining a number of the first rates of change and the second rates of change being less than the rate of change threshold.

7. The method of claim 5, wherein determining the first range and the second range comprises determining a difference between a mean frequency and a fundamental frequency of the sensed cardiac signals.

8. The method of claim 6, wherein detecting the sensed cardiac signals comprises:

determining whether the number of the first rates of change and the number of the second rates of change that are less than the rate of change threshold is less than a first boundary; and

determining whether the range is less than a second boundary different from the first boundary.

9. A method of detecting a cardiac event, comprising:

sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector;

determining a first low slope content of the sensed cardiac signals sensed by the first sensing vector over a predetermined sensing window;

determining a second low slope content of the sensed cardiac signals sensed by the second sensing vector over the predetermined sensing window;

determining a first spectral width of the sensed cardiac signals sensed by the first sensing vector over the predetermined sensing window;

determining a second spectral width of the sensed cardiac signals sensed by the second sensing vector over the predetermined sensing window; and

detecting the sensed cardiac signals as being associated with the event in response to the first low slope content, the second low slope content, the first spectral width and the second spectral width.

10. The method of claim 9, wherein determining a first low slope content and a second low slope content comprises:

determining slopes corresponding to the cardiac signals sensed over the predetermined sensing window;

determining a low slope threshold; and

determining whether the slopes are less than the low slope threshold.

11. The method of claim 10, wherein determining the low slope threshold comprises:

dividing the cardiac signals sensed over the predetermined sensing window into a plurality of sub-segments;

determining largest absolute slopes for each of the plurality of sub-segments; and

determining the low slope threshold in response to the determined largest absolute slopes.

12. The method of claim 11, wherein determining the low slope threshold further comprises:

determining whether the largest absolute slopes are less than a portion of a largest slope determined for the cardiac signals sensed over the predetermined sensing window; and

setting the largest absolute slopes equal to the largest slope in response to the largest absolute slopes being less than the portion of the largest slope.

13. The method of claim 12, further comprising determining a portion of an average of the largest absolute slopes as the low slope threshold.

14. The method of claim 9, wherein determining a first spectral width and a second spectral width comprises determining a difference between an RR-cycle length and a mean spectral period corresponding to the cardiac signals sensed over the predetermined sensing window.

15. The method of claim 9, wherein detecting the sensed cardiac signals comprises:

determining whether the first low slope content and the second low slope content is less than a first boundary; and

determining whether the range is less than a second boundary different from the first boundary.

16. The method of claim 15, wherein the first boundary corresponds to one of the first low slope content being equal to −

0.0013×

the first spectral width+0.415 and the second low slope content being equal to −

0.0013×

the second spectral width+0.415, and the second boundary corresponds to one of the first spectral width and the second spectral width being equal to 200 Hz.

17. The method of claim 12, wherein detecting the sensed cardiac signals comprises:

determining whether a number of the slopes less than the low slope threshold is less than a first boundary; and

determining whether the range is less than a second boundary different from the first boundary.

18. The method of claim 17, wherein the first boundary corresponds to one of the first low slope content being equal to −

0.0013×

the first spectral width+0.415 and the second low slope content being equal to −

0.0013×

the second spectral width+0.415, and the second boundary corresponds to one of the first spectral width and the second spectral width being equal to 200 Hz.

19. A computer readable medium having computer executable instructions for performing a method comprising:

sensing cardiac signals from a plurality of electrodes;

determining rates of change in the sensed cardiac signals;

determining a range of the sensed cardiac signals;

detecting the sensed cardiac signals as being associated with the event in response to the determined rates of change and the determined range.