METHOD AND APPARATUS FOR DETECTING ARRHYTHMIAS IN A MEDICAL DEVICE

• US 20070270704A1
• Filed: 04/28/2006
• Published: 11/22/2007
• 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, Greenhut, Saul, Ghanem, Raja
• Granted Patent: US 7,907,993 B2
• Time in Patent Office: Days
• US Class Current: 600/521
• 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 sensing cardiac signals from a plurality of electrodes forming a first sensing vector and a second sensing vector, and determining first heart rate estimates associated with cardiac signals sensed from the first sensing vector and cardiac signals sensed from the second sensing vector in response to a metric of heart rate associated with the sensed cardiac signals. Second heart rate estimates associated with the first sensing vector and with the second sensing vector are generated in response to the determined first heart rate estimates, and a determination is made as to whether both of the second heart rate estimates are greater than a predetermined heart rate threshold.

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 first heart rate estimates associated with cardiac signals sensed from the first sensing vector and cardiac signals sensed from the second sensing vector in response to a metric of heart rate associated with the sensed cardiac signals;

generating second heart rate estimates associated with the first sensing vector and with the second sensing vector in response to the determined first heart rate estimates; and

determining whether both of the second heart rate estimates are greater than a predetermined heart rate threshold.

2. The method of claim 1, wherein generating second heart rate estimates comprises:

determining whether the first heart rate estimates are reliable; and

setting, in response to one of the first heart rate estimates not being reliable and the other of the first heart rate estimates being reliable, the one of the first heart rate estimates not being reliable equal to the other of the first heart rate estimates being reliable.

3. The method of claim 2, wherein generating second heart rate estimates further comprises setting the second heart rate estimates to the first heart rate estimates in response to the first heart rate estimates being reliable.

4. The method of claim 2, wherein the metric of heart rate corresponds to one of a mean of a plurality of RR intervals associated with the sensed cardiac signals, a trimmed mean of the plurality of RR intervals, a median of the plurality of RR intervals, and a predetermined RR interval of the plurality of RR intervals, and further comprising clearing buffers storing the plurality of RR intervals in response to both of the first heart rate estimates not being reliable.

5. The method of claim 2, wherein the metric of heart rate corresponds to one of a mean of a plurality of RR intervals associated with the sensed cardiac signals, a trimmed mean of the plurality of RR intervals, a median of the plurality of RR intervals, and a predetermined RR interval of the plurality of RR intervals, and wherein determining whether the first heart rate estimates are reliable comprises determining whether a buffer storing the plurality of RR intervals includes a cleared entry.

6. The method of claim 2, wherein the metric of heart rate corresponds to one of a mean of a plurality of RR intervals associated with the sensed cardiac signals, a trimmed mean of the plurality of RR intervals, a median of the plurality of RR intervals, and a predetermined RR interval of the plurality of RR intervals, and wherein determining whether the first heart rate estimates are reliable comprises:

determining whether the plurality of RR intervals are sensed at less than a minimum sensing threshold level; and

determining whether the first heart rate estimates are less than a predetermined heart rate threshold.

7. The method of claim 6, wherein determining whether the plurality of RR intervals are sensed at less than a first sensing threshold level comprises determining whether two RR intervals of the plurality of RR intervals are sensed at less than the sensing threshold, and wherein the plurality of RR intervals is equal to twelve RR intervals and the predetermined heart rate threshold is 180 beats per minute.

8. The method of claim 1, wherein the metric of heart rate corresponds to one of a mean of a plurality of RR intervals associated with the sensed cardiac signals, a trimmed mean of the plurality of RR intervals, a median of the plurality of RR intervals, and a predetermined RR interval of the plurality of RR intervals.

9. The method of claim 8, further comprising:

determining whether a predetermined heart rate condition is present during the plurality of RR intervals for the first sensing vector and during the plurality of RR intervals for the second sensing vector; and

clearing, in response to the predetermined heart rate condition being present for one of the first sensing vector and the second sensing vector, a buffer storing the corresponding plurality of RR intervals.

10. 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 first heart rate estimates associated with cardiac signals sensed from the first sensing vector and cardiac signals sensed from the second sensing vector in response to a metric of heart rate associated with the sensed cardiac signals, the metric of heart rate corresponding to one of a mean of a plurality of RR intervals associated with the sensed cardiac signals, a trimmed mean of the plurality of RR intervals, a median of the plurality of RR intervals, and a predetermined RR interval of the plurality of RR intervals;

determining whether asystole is detected for one of cardiac signals sensed from the first sensing vector and cardiac signals sensed from the second sensing vector;

clearing, in response to asystole being detected for one of cardiac signals sensed from the first sensing vector and cardiac signals sensed from the second sensing vector, a buffer storing the corresponding plurality of RR intervals;

determining whether the first heart rate estimates are reliable;

generating second heart rate estimates in response to the determining whether the first heart rate estimates are reliable; and

determining whether both of the second heart rate estimates are greater than a predetermined heart rate threshold.

11. The method of claim 10, wherein generating second heart rate estimates further comprises setting, in response to one of the first heart rate estimates not being reliable and the other of the first heart rate estimates being reliable, the one of the first heart rate estimates not being reliable equal to the other of the first heart rate estimates being reliable.

12. The method of claim 11, wherein generating second heart rate estimates further comprises setting the second heart rate estimates to the first heart rate estimates in response to the first heart rate estimates being reliable.

13. The method of claim 10, further comprising clearing buffers storing the plurality of RR intervals in response to both of the first heart rate estimates not being reliable.

14. The method of claim 10, wherein determining whether the first heart rate estimates are reliable comprises determining whether a buffer storing the plurality of RR intervals includes a cleared entry.

15. The method of claim 10, wherein determining whether the first heart rate estimates are reliable comprises:

determining whether the plurality of RR intervals are sensed at less than a minimum sensing threshold level; and

determining whether the first heart rate estimates are less than a predetermined heart rate threshold.

16. The method of claim 16, wherein determining whether the plurality of RR intervals are sensed at less than a first sensing threshold level comprises determining whether two RR intervals of the plurality of RR intervals are sensed at less than the sensing threshold, and wherein the plurality of RR intervals is equal to twelve RR intervals and the predetermined heart rate threshold is 180 beats per minute.

17. 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 first heart rate estimates associated with cardiac signals sensed from the first sensing vector and cardiac signals sensed from the second sensing vector in response to a metric of heart rate associated with the sensed cardiac signals;

generating second heart rate estimates associated with the first sensing vector and with the second sensing vector in response to the determined first heart rate estimates; and

determining whether both of the second heart rate estimates are greater than a predetermined heart rate threshold.

18. The computer readable medium of claim 17, the method further comprising:

determining whether the first heart rate estimates are reliable;

setting, in response to one of the first heart rate estimates not being reliable and the other of the first heart rate estimates being reliable, the one of the first heart rate estimates not being reliable equal to the other of the first heart rate estimates being reliable; and

setting the second heart rate estimates to the first heart rate estimates in response to the first heart rate estimates being reliable.

19. The computer readable medium of claim 18, wherein the metric of heart rate corresponds to one of a mean of a plurality of RR intervals associated with the sensed cardiac signals, a trimmed mean of the plurality of RR intervals, a median of the plurality of RR intervals, and a predetermined RR interval of the plurality of RR intervals, and wherein determining whether the first heart rate estimates are reliable comprises:

determining whether the plurality of RR intervals are sensed at less than a minimum sensing threshold level; and

determining whether the first heart rate estimates are less than a predetermined heart rate threshold.

20. The computer readable medium of claim 17, wherein the metric of heart rate corresponds to one of a mean of a plurality of RR intervals associated with the sensed cardiac signals, a trimmed mean of the plurality of RR intervals, a median of the plurality of RR intervals, and a predetermined RR interval of the plurality of RR intervals, the method further comprising:

determining whether a predetermined heart rate condition is present during the plurality of RR intervals for the first sensing vector and during the plurality of RR intervals for the second sensing vector; and

clearing, in response to the predetermined heart rate condition being present for one of the first sensing vector and the second sensing vector, a buffer storing the corresponding plurality of RR intervals.