METHOD AND APPARATUS FOR DETECTING ARRHYTHMIAS IN A MEDICAL DEVICE

• US 20070239047A1
• 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 7,761,150 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• 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 in a medical device that includes determining a first characteristic in response to cardiac signals sensed along a first sensing vector over a predetermined sensing window and in response to cardiac signals sensed along a second sensing vector over the predetermined sensing window, determining a second characteristic in response to cardiac signals sensed along the first sensing vector over the predetermined sensing window and in response to cardiac signals sensed along the second sensing vector over the predetermined sensing window, and determining a third characteristic in response to cardiac signals sensed along the first sensing vector over the predetermined sensing window and in response to cardiac signals sensed along the second sensing vector over the predetermined sensing window.

Claims

1. A method of detecting a cardiac event in a medical device, 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 characteristic in response to the cardiac signals sensed along the first sensing vector over a predetermined sensing window and in response to the cardiac signals sensed along the second sensing vector over the predetermined sensing window;

determining a second characteristic in response to the cardiac signals sensed along the first sensing vector over the predetermined sensing window and in response to the cardiac signals sensed along the second sensing vector over the predetermined sensing window;

determining a third characteristic in response to the cardiac signals sensed along the first sensing vector over the predetermined sensing window and in response to the cardiac signals sensed along 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 characteristic, the second characteristic, and the third characteristic.

2. The method of claim 1, wherein determining the first characteristic comprises:

determining first rates of change in the cardiac signals sensed by the first sensing vector;

determining second rates of change in the cardiac signals sensed by the second sensing vector; and

determining the first characteristic in response to the first rates of change and the second rates of change.

3. The method of claim 2, 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.

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

7. The method of claim 1, wherein determining the third characteristic comprises:

determining a first amplitude associated with the cardiac signals sensed by the first sensing vector and a second amplitude associated with the cardiac signals sensed by the second sensing vector; and

determining the third characteristic in response to the first amplitude and the second amplitude.

8. The method of claim 1, wherein detecting the sensed cardiac signals comprises:

determining a minimum of the first characteristic determined for the first sensing vector and the first characteristic determined for the second sensing vector;

determining a minimum of the second characteristic determined for the first sensing vector and the second characteristic determined for the second sensing vector; and

determining the maximum of the third characteristic determined for the first sensing vector and the third characteristic determined for the second sensing vector.

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

determining a first boundary corresponding to the minimum of the first characteristic and the minimum of the second characteristic;

determining a second boundary corresponding to the minimum of the first characteristic and the maximum of the third characteristic;

determining whether the first characteristic is less than the first boundary and the third characteristic is less than the second boundary.

10. The method of claim 9, wherein the first boundary corresponds to the minimum of the first characteristic being equal to the sum of 0.93 and the product the second characteristic associated one of the first sensing vector and the second sensing vector and −

0.004, and the second boundary corresponds to the maximum of the third characteristic being equal to the sum of 8.16 and the product of 68 and the minimum of the first characteristic.

4. The method of claim 4, wherein determining the rate of change threshold comprises:

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

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

determining the rate of change threshold in response to the determined largest absolute rates of change.

5. The method of claim 4, wherein determining the rate of change threshold further comprises:

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

setting the largest absolute rates of change equal to the largest rate of change in response to the largest absolute rates of change being less than the portion of the largest rate of change.

11. A method of detecting a cardiac event in a medical device, 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 and a second low slope content of the sensed cardiac signals sensed by the second sensing vector over a predetermined sensing window;

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

determining a first amplitude associated with the cardiac signals sensed by the first sensing vector and a second amplitude associated with the cardiac signals sensed by the second sensing vector; 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, the second spectral width, the first amplitude and the second amplitude.

12. The method of claim 11, further comprising:

determining a minimum of the first low slope content and the second low slope content;

determining a minimum of the first spectral width and the second spectral width; and

determining a maximum of the first amplitude and the second amplitude.

13. The method of claim 12, further comprising:

determining a first boundary corresponding to the minimum of the first low slope content and the second low slope content and the minimum of the first spectral width and the second spectral width;

determining a second boundary corresponding to the minimum of the low slope content and the second low slope content and the maximum of the first amplitude and the second amplitude.

14. The method of claim 13, wherein the first boundary corresponds to the minimum of the first low slope content and the second low slope content being equal to the sum of 0.93 and the product of −

0.004 and the spectral width of one of the first sensing vector and the second sensing vector, and the second boundary corresponds to the maximum of the first amplitude and the second amplitude being equal to the sum of 8.16 and the product of 68 and the minimum of the first low slope content and the second low slope content.

15. The method of claim 11, 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.

16. The method of claim 15, 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.

17. The method of claim 16, 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.

18. The method of claim 17, further comprising determining a portion of an average of the largest absolute slopes as the low slope threshold.

19. The method of claim 11, further comprising:

determining a minimum of the first low slope content and the second low slope content;

determining a minimum of the first spectral width and the second spectral width;

determining a maximum of the first amplitude and the second amplitude;

determining a first boundary corresponding to the minimum of the first low slope content and the second low slope content and the minimum of the first spectral width and the second spectral width; and

determining a second boundary corresponding to the minimum of the low slope content and the second low slope content and the maximum of the first amplitude and the second amplitude; and

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.

20. A computer readable medium having computer executable instructions for performing a method 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 characteristic in response to the cardiac signals sensed along the first sensing vector over a predetermined sensing window and in response to the cardiac signals sensed along the second sensing vector over the predetermined sensing window;

determining a second characteristic in response to the cardiac signals sensed along the first sensing vector over the predetermined sensing window and in response to the cardiac signals sensed along the second sensing vector over the predetermined sensing window;

determining a third characteristic in response to the cardiac signals sensed along the first sensing vector over the predetermined sensing window and in response to the cardiac signals sensed along 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 characteristic, the second characteristic, and the third characteristic.