METHOD AND APPARATUS FOR VERIFYING A DETERMINED CARDIAC EVENT IN A MEDICAL DEVICE BASED ON DETECTED VARIATION IN HEMODYNAMIC STATUS

• US 20070239052A1
• Filed: 04/28/2006
• Published: 10/11/2007
• Est. Priority Date: 03/31/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Bhunia, Sourav
• Granted Patent: US 7,962,202 B2
• Time in Patent Office: Days
• US Class Current: 600/513
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

A method and apparatus for verifying a determined cardiac event in a medical device based on detected variation in hemodynamic status that includes a physiologic sensor sensing physiologic signals to generate a plurality of variation index samples corresponding to the sensed signals, and a microprocessor computing a variation index trend associated with a predetermined number of variation index samples of the plurality of variation index samples, determining whether deviations of the predetermined number of variation index samples over predetermined sampling windows are less than a deviation threshold, and determining, in response to the deviations being less than the deviation threshold, a corrected variation index trend in response to the changes in the variation index trend during the predetermined sampling windows.

Claims

1. A medical device, comprising:

a physiologic sensor sensing physiologic signals to generate a plurality of variation index samples corresponding to the sensed signals; and

a microprocessor computing a variation index trend associated with a predetermined number of variation index samples of the plurality of variation index samples, determining whether deviations of the predetermined number of variation index samples over predetermined sampling windows are less than a deviation threshold, and determining, in response to the deviations being less than the deviation threshold, a corrected variation index trend in response to the changes in the variation index trend during the predetermined sampling windows.

2. The device of claim 1, wherein the variation index trend corresponds to a measure of change in tissue oxygenation.

3. The device of claim 1, wherein the determined corrected index trend includes an offset determined in response to the deviations not being less than the deviation threshold.

4. The device of claim 1, wherein the microprocessor determines, in response to the deviations being less than the deviation threshold, whether the sensed signals are associated with an unstable rhythm.

5. The device of claim 4, wherein the microprocessor determines whether the computed variation index trend is less than a predetermined index trend threshold.

6. The device of claim 1, wherein the variation index trend corresponds to relationships between proportions of red light intensities and infrared light intensities to corresponding baseline intensities.

7. The device of claim 1, wherein the variation index trend corresponds to

8. The device of claim 1, further comprising a plurality of sensors sensing cardiac signals, wherein the microprocessor detects a cardiac event in response to the sensed cardiac signals and confirms the detected cardiac event in response to the corrected variation index trend.

9. A method of determining a cardiac event in a medical device, comprising:

sensing physiologic signals to generate a plurality of variation index samples corresponding to the sensed signals;

computing a variation index trend associated with a predetermined number of variation index samples of the plurality of variation index samples;

determining whether deviations of the predetermined number of variation index samples over predetermined sampling windows are less than a deviation threshold; and

determining, in response to the deviations being less than the deviation threshold, a corrected variation index trend in response to the changes in the variation index trend during the predetermined sampling windows.

10. The method of claim 9, wherein the variation index trend corresponds to a measure of change in tissue oxygenation.

11. The method of claim 9, further comprising determining, in response to the deviations being less than the deviation threshold, whether the sensed signals are associated with an unstable rhythm.

12. The method of claim 11, wherein determining whether the sensed signals are associated with an unstable rhythm comprises determining whether the computed variation index trend is less than a predetermined index trend threshold.

13. The method of claim 9, wherein the variation index trend corresponds to relationships between proportions of red light intensities and infrared light intensities to corresponding baseline intensities.

14. The method of claim 9, wherein the variation index trend corresponds to

15. The method of claim 9, wherein the determined corrected index trend includes an offset determined in response to the deviations not being less than the deviation threshold.

16. A method of verifying a cardiac event in a medical device, comprising:

sensing cardiac signals from a plurality of electrodes;

determining the cardiac event in response to the sensed first cardiac signals;

sensing physiologic signals to generate a plurality of variation index samples corresponding to the sensed signals;

computing a variation index trend associated with a predetermined number of variation index samples of the plurality of variation index samples;

determining whether deviations of the predetermined number of variation index samples over predetermined sampling windows are less than a deviation threshold;

determining, in response to the deviations being less than the deviation threshold, a corrected variation index trend in response to the changes in the variation index trend during the predetermined sampling windows; and

confirming the determined cardiac event in response to the corrected variation index trend.

17. The method of claim 16, wherein the variation index trend corresponds to a measure of change in tissue oxygenation.

18. The method of claim 16, further comprising determining, in response to the deviations being less than the deviation threshold, whether the sensed signals are associated with an unstable rhythm.

19. The method of claim 18, wherein determining whether the sensed signals are associated with an unstable rhythm comprises determining whether the computed variation index trend is less than a predetermined index trend threshold.

20. The method of claim 16, wherein the variation index trend corresponds to relationships between proportions of red light intensities and infrared light intensities to corresponding baseline intensities.

21. The method of claim 16, wherein the variation index trend corresponds to

22. The method of claim 21, further comprising determining an offset in response to the deviations not being less than the deviation threshold.