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

• US 20070255148A1
• Filed: 04/28/2006
• Published: 11/01/2007
• 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 7,647,095 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• 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 plurality of sensors sensing cardiac signals, and a physiologic sensor sensing physiologic signals to generate a plurality of variation index samples corresponding to the sensed signals. A microprocessor detects a cardiac event in response to the sensed cardiac signals, computes a variation index trend associated with a predetermined number of variation index samples of the plurality of variation index samples, determines a rate of change of the computed variation index trend, and confirms the determined cardiac event in response to the computed variation index trend and in response to the determined rate of change.

Claims

1. A medical device, comprising:

a plurality of sensors sensing cardiac signals;

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

a microprocessor detecting a cardiac event in response to the sensed cardiac signals, computing a variation index trend associated with a predetermined number of variation index samples of the plurality of variation index samples, determining a rate of change of the variation index trend, and confirming the determined cardiac event in response to the computed variation index trend and the determined rate of change.

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 microprocessor determines a deviation of the predetermined number of variation index samples from the variation index trend.

4. The device of claim 3, wherein the microprocessor determines whether the computed variation index trend is less than a predetermined index trend threshold.

5. The device of claim 1, wherein the microprocessor determines whether the rate of change is one of greater than an upper limit and less than a lower limit.

6. The device of claim 1, wherein the microprocessor whether the rate of change is within one of a first range corresponding to a ventricular tachycardia event and a second range corresponding to a ventricular fibrillation event.

7. 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.

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

9. A method of determining 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 and acquiring a plurality of variation index samples corresponding to the sensed physiologic signals;

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

determining a rate of change of the computed variation index trend; and

confirming the determined cardiac event in response to the computed variation index trend and the determined rate of change.

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 a deviation of the predetermined number of variation index samples from the variation index trend.

12. The method of claim 11, further comprising determining, in response to the determined deviation, whether the sensed cardiac signals are associated with an unstable rhythm, wherein the determined cardiac event is confirmed in response to the determined deviation and the sensed cardiac signals being associated with an unstable rhythm.

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, further comprising determining whether the rate of change is one of greater than an upper limit and less than a lower limit.

16. The method of claim 9, further comprising determining whether the rate of change is within one of a first range corresponding to a ventricular tachycardia event and a second range corresponding to a ventricular fibrillation event.

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

sensing physiologic signals and acquiring a plurality of variation index samples corresponding to the sensed physiological signals;

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

determining a rate of change of the variation index trend; and

verifying the cardiac event in response to the determined variation index trend and the determined rate of change.

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

19. The method of claim 17, further comprising determining whether the computed variation index trend is less than a predetermined index trend threshold.

20. The method of claim 19, further comprising determining whether a deviation of the predetermined number of variation index samples from the computed variation index trend is greater than a deviation threshold, wherein the cardiac event is verified in response to both the computed variation index trend being less than the predetermined index trend threshold and the deviation not being greater than the deviation threshold.

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

22. The method of claim 17, wherein the variation index trend corresponds to

23. The method of claim 17, further comprising determining whether the rate of change is one of greater than an upper limit and less than a lower limit.

24. The method of claim 17, further comprising determining whether the rate of change is within one of a first range corresponding to a ventricular tachycardia event and a second range corresponding to a ventricular fibrillation event.