Systems and methods for detecting and compensating for changes in posture during ischemia detection a using an implantable medical device

• US 8,108,035 B1
• Filed: 10/18/2006
• Issued: 01/31/2012
• Est. Priority Date: 10/18/2006
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Bharmi, Rupinder
• Primary Examiner(s): Patel, Niketa
• Assistant Examiner(s): EL-KAISSI, HIBA CARINE
• Application Number:
  US11/550,744
• Time in Patent Office: 1,931 Days
• Field of Search: 607/9, 607 17- 19, 600/517, 600/509
• US Class Current: 600/509
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/283 Invasive
• 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: A61N 1/36535 controlled by body position or posture
• CPC Class Codes: A61N 1/36542 controlled by body motion, e.g. acceleration

Abstract

Techniques are described for detecting changes in posture; detecting cardiac ischemia while accounting for changes in posture; and delivering therapy or warning signals in response thereto using the implantable medical device. In one example, the device detects variations in the electrical cardiac signals indicative of a possible episode of cardiac ischemia. Changes in patient posture are detected as well using an accelerometer or similar device. Then, an episode of cardiac ischemia is detected based on the variations in the cardiac signals while distinguishing variations due to changes in posture. In another example, the device instead detects changes in posture based on transient changes in morphological features of electrical cardiac signals.

Claims

1. A method for use with an implantable medical device for implant within a patient, comprising:

detecting electrical cardiac signals within the patient;

detecting variations in the cardiac signals indicative of a possible episode of cardiac ischemia;

obtaining atrial paced depolarization integral (PDI) measurements, including an initial baseline atrial PDI based on atrial PDI measurements before a posture change by the patient, a subsequent baseline atrial PDI based on atrial PDI measurements following the posture change by the patient, and transient PDI measurements corresponding to the PDI measurements during the posture change;

detecting a significant change in patient posture when a difference between the initial atrial PDI baseline and the subsequent atrial PDI baseline exceeds a predetermined threshold indicative of a significant posture change;

identifying a transient decay period subsequent to a change in posture during which the transient PDI measurements gradually decay to the subsequent baseline atrial PDI;

detecting, using a microprocessor, for an episode of cardiac ischemia based, at least in part, on weighted parameters of the cardiac signals, wherein the weights of the parameters of those cardiac signals detected during a significant posture change period and the transient decay period are adjusted according to a particular technique being used to detect ischemia, wherein the significant posture change period corresponds to the period of time during which atrial PDI measurements transition from an initial atrial PDI baseline to a subsequent atrial PDI baseline, wherein the initial atrial PDI baseline and the subsequent atrial PDI baseline correspond to a previously detected significant change in patient posture.

2. The method of claim 1 wherein detecting electrical cardiac signals include detecting an intracardiac electrogram (IEGM).

3. The method of claim 1 wherein detecting variations in the cardiac signals indicative of a possible episode of a cardiac ischemia includes detecting selected variations in one or more of the elevation, width, maximum slope, and peak amplitude of P-waves, QRS-complexes, T-waves, intervals therebetween and integrals thereof.

4. The method of claim 3 wherein detecting selected variations in the cardiac signals includes detecting variations in an ST-segment elevation.

5. The method of claim 1 further including the step of controlling therapy in response to the detection of an episode of cardiac ischemia.

6. The method of claim 1 further including the step of generating a warning signal in response to detection of an episode of cardiac ischemia.

9. The method of claim 1 wherein the difference between the initial atrial PDI baseline and the subsequent atrial PDI baseline corresponds to a change in mean atrial PDI.

10. The method of claim 1 wherein the difference between the initial atrial PDI baseline and the subsequent atrial PDI baseline corresponds to a change in standard deviation of atrial PDI.

7. A system for use with an implantable medical device for implant within a patient, comprising:

a cardiac signal detection unit configured to detect electrical cardiac signals within the patient;

a medical condition detection unit configured to detect variations in the cardiac signals indicative of a possible episode of cardiac ischemia;

and a posture change detection unit configured to obtain atrial paced depolarization integral (PDI) measurements, including an initial baseline atrial PDI based on atrial PDI measurements before a posture change by the patient, a subsequent baseline atrial PDI measurements following the posture change by the patient, and transient PDI measurements corresponding to the PDI measurements during the posture change;

to identify a transient decay period subsequent to a change in posture during which the transient PDI measurements gradually decay to the subsequent baseline atrial PDI;

and to detect a significant change in patient posture by comparing the difference between initial atrial PDI baseline and the subsequent atrial PDI baseline to a predetermined threshold indicative of a significant posture change;

wherein the medical condition detection unit is configured to detect for an episode of cardiac ischemia based, at least in part, on weighted parameters of the cardiac signals, wherein the weights of the parameters of those cardiac signals detected during a significant posture change period and the transient decay period are adjusted according to a particular technique being used to detect ischemia, wherein the significant posture change period corresponds to the period of time during which atrial PDI measurements transition from an initial atrial PDI baseline to a subsequent atrial PDI baseline, wherein the initial atrial PDI baseline and the subsequent atrial PDI baseline correspond to a previously detected significant change in patient posture.

8. A system for use with an implantable medical device for implant within a patient, comprising:

means for detecting electrical cardiac signals within the patient;

means for detecting variations in the cardiac signals indicative of a possible episode of cardiac ischemia;

means for obtaining atrial paced depolarization integral (PDI) measurements, including an initial baseline atrial PDI based on atrial PDI measurements before a posture change by the patient, a subsequent baseline atrial PDI based on atrial PDI measurements following the posture change by the patient, and transient PDI measurements corresponding to the PDI measurements during the posture change;

means for detecting a significant change in patient posture when a difference between the initial atrial PDI baseline and the subsequent atrial PDI baseline exceeds a predetermined threshold indicative of a significant posture change;

means for identifying a transient decay period subsequent to a change in posture during which the transient PDI measurements gradually decay to the subsequent baseline atrial PDI; and

means for detecting an episode of cardiac ischemia based, at least in part, on weighted parameters of the cardiac signals, wherein the weights of the parameters of those cardiac signals detected during a significant posture change period and the transient decay period are adjusted according to a particular technique being used to detect ischemia, wherein the significant posture change period corresponds to the period of time during which atrial PDI measurements transition from an initial atrial PDI baseline to a subsequent atrial PDI baseline, wherein the initial atrial PDI baseline and the subsequent atrial PDI baseline correspond to a previously detected significant change in patient posture.