Method and apparatus for verifying a determined cardiac event in a medical device based on detected variation in hemodynamic status

• US 8,095,205 B2
• Filed: 04/28/2006
• Issued: 01/10/2012
• Est. Priority Date: 03/31/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Bhunia, Sourav
• Primary Examiner(s): Patel, Niketa
• Assistant Examiner(s): Holmes, Rex R
• Application Number:
  US11/380,855
• Publication Number:
  US 20070239053A1
• Time in Patent Office: 2,083 Days
• Field of Search: 607 17- 22, 600508-509
• 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 whether the sensed cardiac signals are associated with noise in response to the computed variation index, and confirms the determined cardiac event in response to the sensed cardiac signals not being associated with noise.

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 cardiac signals; and

a microprocessor detecting the presence of a cardiac event in response to the sensed cardiac signals, computing, during the detected presence of the cardiac event, a variation index trend associated with a predetermined number of variation index samples of the plurality of variation index samples, determining the deviation of variation index samples of a current predetermined number of variation index samples from the variation index trend, determining whether the sensed cardiac signals are associated with noise in response to the determined deviation, and confirming the detected presence of the cardiac event in response to the sensed cardiac signals not being associated with noise.

2. The device of claim 1, wherein the physiologic sensor comprises an optical sensor sensing an optical signal to determine tissue oxygenation and the variation index trend corresponds to a measure of change in tissue oxygenation determined in response to the sensed optical signal.

3. The device of claim 1, wherein the microprocessor determines, in response to the sensed cardiac signals not being associated with noise, whether the sensed cardiac signals are associated with an unstable rhythm.

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 physiologic sensor comprises an optical sensor generating an optical signal and the variation index trend corresponds to relationships between proportions of red light intensities of the optical signal and infrared light intensities of the optical signal to corresponding baseline intensities.

6. The device of claim 1, wherein the physiologic sensor comprises an optical sensor generating an optical signal and the variation index trend corresponds to

13. The device of claim 1, wherein the microprocessor computes the variation index trend over a moving group of the predetermined number of variation index samples of the plurality of variation index samples, including variation index samples of a previous group of the predetermined number of variation index samples.

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

sensing cardiac signals from a plurality of electrodes;

detecting the presence of the cardiac event in response to the sensed cardiac signals;

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

computing, during the detected presence of the cardiac event, a variation index trend associated with a predetermined number of variation index samples of the plurality of variation index samples;

determining deviations of variation index samples of a current predetermined number of variation index samples from the variation index trend;

determining whether the sensed cardiac signals are associated with noise in response to the determined deviations; and

confirming the detected presence of the cardiac event in response to the sensed cardiac signals not being associated with noise.

8. The method of claim 7, wherein the sensed physiologic signal comprises an optical signal and the variation index trend corresponds to a measure of change in tissue oxygenation determined in response to the sensed optical signal.

9. The method of claim 7, further comprising determining, in response to the sensed cardiac signals not being associated with noise, whether the sensed cardiac signals are associated with an unstable rhythm, wherein the determined cardiac event is confirmed in response to the sensed cardiac signals being associated with an unstable rhythm.

10. The method of claim 9, wherein determining whether the sensed cardiac signals are associated with an unstable rhythm comprises determining whether the computed variation index trend is less than a predetermined index trend threshold.

11. The method of claim 7, wherein sensing physiologic signals comprises sensing optical signals and the variation index trend corresponds to relationships between proportions of red light intensities of the optical signals and infrared light intensities of the optical signals to corresponding baseline intensities.

12. The method of claim 7, wherein sensing physiologic signals comprises sensing optical signals and the variation index trend corresponds to

14. The method of claim 7, wherein computing the variation index trend comprises computing the variation index trend over a moving group of the predetermined number of variation index samples of the plurality of variation index samples, including variation index samples of a previous group of the predetermined number of variation index samples.