Methods and Apparatuses for Detection of Myocardial Ischemia Upon Exertion

• US 20100030090A1
• Filed: 07/23/2009
• Published: 02/04/2010
• Est. Priority Date: 08/01/2008
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: ZHANG, YI, ZHANG, YUNLONG, LEWICKE, AARON, Beck, Kenneth C.
• Granted Patent: US 8,321,003 B2
• Time in Patent Office: Days
• US Class Current: 600/508
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02055 Simultaneously evaluating both cardiovascular condition and temperature
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/03 Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs A61B5/205 takes precedence
• CPC Class Codes: A61B 5/4519 Muscles A61B5/389, A61B5/224 take precedence

Abstract

Various method embodiments of the present invention concern sensing patient-internal pressure measurements indicative of physiological exertion, identifying one or more steady state periods of physiological exertion based on the patient-internal pressure measurements, sensing extra-cardiac response data and cardiac response data corresponding to the one or more physiological exertion steady state periods, respectively comparing the extra-cardiac response data and the cardiac response data to extra-cardiac response information and cardiac response information associated with equivalent levels of physiological exertion intensity of the one or more steady state periods, and determining the likelihood that myocardial ischemia occurred during the one or more steady state periods based on the comparison of the extra-cardiac response data to the extra-cardiac response information and the cardiac response data to the cardiac response information.

Claims

1. A method of detecting ischemia during exertion, comprising:

obtaining static exertion measurements indicative of static physiological exertion;

identifying steady state periods of physiological exertion based on the static exertion measurements;

assessing the intensity of physiological exertion for each of the identified steady state periods;

sensing extra-cardiac response data during identified physiological exertion steady state periods;

sensing cardiac response data during identified physiological exertion steady state periods;

comparing the extra-cardiac response data corresponding to identified steady state periods of physiological exertion with extra-cardiac response information associated with equivalent physiological exertion intensity;

determining the normalcy of the extra-cardiac response data for each steady state period based on the comparison of the extra-cardiac response data and the extra-cardiac response information;

comparing the cardiac response data corresponding to identified steady state periods of physiological exertion with cardiac response information associated with equivalent physiological exertion intensity;

determining the normalcy of the cardiac response data for each steady state period based on the comparison of the cardiac response data and the cardiac response information; and

determining the likelihood that myocardial ischemia occurred during one or more of the identified steady state periods of physiological exertion, wherein;

the likelihood of ischemia for the one or more steady state periods is determined to be relatively high if both the extra-cardiac response data and the cardiac response data sensed during the one or more steady state periods are determined to be abnormal;

the likelihood of ischemia for the one or more steady state periods is determined to be relatively moderate if only one of the extra-cardiac response data and the cardiac response data sensed during the one or more steady state periods is determined to be abnormal; and

the likelihood of ischemia for the one or more steady state periods is determined to be relatively low if neither of the extra-cardiac response data and the cardiac response data sensed during the one or more steady state periods are determined to be abnormal.

2. The method of claim 1, wherein:

obtaining static exertion measurements comprises obtaining patient internal pressure measurements;

identifying steady state periods of physiological exertion comprises identifying steady state periods of exertion based on the patient internal pressure measurements; and

assessing the intensity of physiological exertion for the identified steady state periods comprises classifying each period in one of a plurality of patient internal pressure ranges.

3. The method of claim 1, further comprising

sensing accelerometer data during identified physiological exertion steady state periods;

and

classifying one or more of the identified physiological exertion steady state periods as either a static exertion period or a dynamic exertion period, wherein the one or more periods are classified as static exertion if an increase in static exertion measurements is sensed without a corresponding increase in physical movement indicated by the accelerometer data and the one or more periods are classified as dynamic exertion if the increase in static exertion measurements corresponds with the increase in physical movement indicated by the accelerometer data.

4. The method of claim 3, wherein the steps of comparing and determining the normalcy of the extra-cardiac response data, and comparing and determining the normalcy of the cardiac response data, are only performed for steady state periods of exertion classified as dynamic exertion periods.

5. The method of claim 3, further comprising classifying one or more episodes of angina as stable angina, unstable angina, or vasospasm using the extra-cardiac response data, the cardiac response data, and the static or dynamic exertion period classification, wherein:

the one or more episodes of angina are classified as stable angina if one or more steady state periods of exertion corresponding to the one or more episodes of angina are classified as dynamic exertion and either of the extra-cardiac response data and the cardiac response data show a non-proportional physiological response with respect to exertion intensity beyond an angina threshold, wherein below the angina threshold the extra-cardiac response data or the cardiac response data show a proportional physiological response with respect to exertion intensity;

the one or more episodes of angina are classified as unstable angina if either of the extra-cardiac response data and the cardiac response data show the non-proportional physiological response with respect to exertion intensity with no angina threshold below which the extra-cardiac response data or the cardiac response data show the proportional physiological response with respect to exertion intensity; and

the one or more episodes of angina are classified as vasospasm if one or more episodes of exertion corresponding to the one or more episodes of angina are classified as static exertion and either of the extra-cardiac response data and the cardiac response data show a non-proportional physiological response with respect to exertion intensity beyond an angina threshold, wherein below the angina threshold the extra-cardiac response data or the cardiac response data show a proportional physiological response with respect to exertion intensity.

6. The method of claim 1, wherein the extra-cardiac response information and the cardiac response information each comprise previously collected patient data that has been trended, and wherein determining the normalcy of the extra-cardiac response data and the cardiac response data comprises respectively comparing the extra-cardiac response data and the cardiac response data with the trended previously collected patient data to determine whether the extra-cardiac response data and the cardiac response data corresponds to trends of the previously collected patient data.

7. The method of claim 1, wherein the extra-cardiac response information and the cardiac response information each comprise previously determined baselines, and wherein determining the normalcy of the extra-cardiac response data and the cardiac response data comprises assessing deviation of the extra-cardiac response data and the cardiac response data from the baselines.

8. The method of claim 1, further comprising modifying a therapy based on a relatively high likelihood of ischemia being determined for one or more of the identified periods of steady state physiological exertion.

9. The method of claim 1, wherein sensing extra-cardiac response data comprises sensing one or more of minute ventilation, tidal volume, pulmonary vascular pressure, core body temperature, venous oxygen saturation, and respiration rate.

10. The method of claim 1, wherein comparing the cardiac response data and determining the normalcy of the cardiac response data comprises comparing electro-cardiac data to electro-cardiac information, and wherein the electro-cardiac data comprises one or more of heart rate, ST segment deviation, ST segment slope, FCC, PVC, AF %, QRS width, T-wave amplitude, T-wave polarity, and R-wave amplitude.

11. The method of claim 1, further comprising classifying myocardial ischemia of one or more of the identified steady state periods of physiological exertion as exertion-related myocardial ischemia or non-exertion-related myocardial ischemia, wherein:

the myocardial ischemia is classified as exertion-related myocardial ischemia if the extra-cardiac response data or the cardiac response data sensed during the one or more steady state periods show a non-proportional physiological response with respect to exertion intensity beyond a threshold, wherein below the threshold the extra-cardiac response data or the cardiac response data show a proportional physiological response with respect to exertion intensity; and

the myocardial ischemia is classified as non-exertion-related myocardial ischemia if the extra-cardiac response data or the cardiac response data sensed during the one or more steady state periods show the non-proportional physiological response with respect to exertion intensity with no threshold below which the extra-cardiac response data or the cardiac response data show the proportional physiological response with respect to exertion intensity.

12. A system for characterizing myocardial ischemia, comprising:

an implantable static exertion sensor configured to output an exertion signal responsive to patient static exertion, the exertion signal containing static exertion data;

at least one implantable physiological parameter sensor configured to output a physiological signal responsive to a physiological parameter, the physiological signal containing physiological exertion-response data;

memory; and

a processor configured to execute program instructions stored in memory to cause the system to;

identify steady state periods of physiological exertion based on the static exertion data and assign one of a plurality of exertion intensity levels to each of the steady state periods;

organize the physiological exertion-response data according to the assigned exertion intensity levels of the identified steady state periods of physiological exertion during which the physiological exertion-response data was respectively output;

compare the physiological exertion-response data with stored physiological response information associated with equivalent levels of physiological exertion intensity of the steady state periods to which the physiological exertion-response data is organized; and

determine the likelihood that myocardial ischemia occurred during one or more of the periods based on the comparison of the physiological response information to the physiological exertion-response data.

13. The system of claim 12, wherein the at least one implantable physiological parameter sensor comprises:

an implantable extra-cardiac parameter sensor configured to output an extra-cardiac signal responsive to an extra-cardiac parameter, the extra-cardiac signal containing extra-cardiac response data; and

an implantable cardiac parameter sensor configured to output a cardiac signal responsive to a cardiac parameter, the cardiac signal containing cardiac response data, wherein;

processor organization of the physiological response data comprises organizing the respective extra-cardiac response and cardiac response data according to the assigned exertion intensity levels of the identified steady state periods of physiological exertion during which the extra-cardiac response and cardiac response data was respectively output;

processor comparison of the physiological exertion-response data with stored physiological response information comprises respectively comparing the extra-cardiac and cardiac response data with extra-cardiac and cardiac response information associated with equivalent levels of physiological exertion intensity of the steady state periods to which the extra-cardiac and cardiac response data is organized; and

determining the likelihood that myocardial ischemia occurred during one or more of the periods based on the comparison of the extra-cardiac and cardiac response data to the extra-cardiac and cardiac response information.

14. The system of claim 13, wherein:

the likelihood that myocardial ischemia occurred during a period of the identified steady state periods is determined to be relatively high if both the extra-cardiac response data and the cardiac response data for the period deviate from trends of the extra-cardiac response information and the cardiac response information;

the likelihood that myocardial ischemia occurred during the period is determined to be relatively moderate if only one of the extra-cardiac response data and the cardiac response data for the period deviate from trends of the extra-cardiac response information and the cardiac response information; and

the likelihood that myocardial ischemia occurred during the period is determined to be relatively low if neither of the extra-cardiac response data and the cardiac response data for the period deviate from trends of the extra-cardiac response information and the cardiac response information.

15. The system of claim 12, wherein the implantable static exertion sensor is configured to sense patient internal pressure and output a pressure signal responsive to patient static exertion, the pressure signal containing static exertion data, and wherein the processor is configured to execute stored program instructions to identify the steady state periods of physiological exertion based on the pressure signal.

16. The system of claim 12, further comprising an accelerometer configured to output a dynamic exertion signal responsive to patient movement, the dynamic exertion signal containing dynamic exertion data, wherein steady state periods of dynamic physiological exertion are further identified based on the dynamic exertion data.

17. The system of claim 16, wherein the processor is configured to execute stored program instructions to cause the system to classify one or more of the steady state periods of physiological exertion as either a static exertion period or a dynamic exertion period, wherein the one or more steady state periods are classified as static exertion if an increase in patient internal pressure is sensed without a corresponding increase in physical movement indicated by the dynamic exertion data and the one or more steady state periods are classified as dynamic exertion if the increase in patient internal pressure corresponds with the increase in physical movement indicated by the dynamic exertion data.

18. The system of claim 17, wherein the processor is configured to execute stored program instructions to cause the system to classify an episode of angina as stable angina, unstable angina, or vasospasm using the extra-cardiac response data, the cardiac response data, and the static or dynamic exertion period classification, wherein:

the episode of angina is classified as stable angina if a corresponding period of exertion is classified as dynamic exertion and the physiological exertion-response data shows a non-proportional physiological response with respect to exertion intensity beyond an angina threshold, wherein below the angina threshold the physiological exertion-response data show a proportional physiological response with respect to exertion intensity;

the episode of angina is classified as unstable angina if the physiological exertion-response data shows the non-proportional physiological response with respect to exertion intensity with no angina threshold below which the physiological exertion-response data shows the proportional physiological response with respect to exertion intensity; and

the episode of angina is classified as vasospasm if the corresponding period of exertion is classified as static exertion and the physiological exertion-response data shows the non-proportional physiological response with respect to exertion intensity beyond an angina threshold, wherein below the angina threshold the physiological exertion-response data shows the proportional physiological response with respect to exertion intensity.

19. The system of claim 12, wherein the processor is configured to execute stored program instructions to cause the system to modify a therapy based on a relatively high likelihood of ischemia being determined for a period of identified steady state physiological exertion.

20. The system of claim 12, wherein the patient-internal extra-cardiac parameter sensor is configured to sense data from which the processor can determine one or more of minute ventilation, tidal volume, pulmonary vascular pressure, core body temperature, venous oxygen saturation, and respiration rate.

21. The system of claim 12, wherein the patient-internal cardiac sensor is configured to sense data from which the processor can determine an electro-cardiac parameter and the processor is configured to execute stored program instructions to compare the electro-cardiac parameter to the cardiac response information to determine the myocardial ischemia likelihood, wherein the electro-cardiac parameter comprises one or more of heart rate, ST segment deviation, ST segment slope, FCC, PVC, AF %, QRS width, T-wave amplitude, T-wave polarity, and R-wave amplitude.

22. The system of claim 12, wherein the processor is configured to execute stored program instructions to cause the system to:

classify myocardial ischemia of one or more of the identified steady state periods of physiological exertion as exertion-related myocardial ischemia or non-exertion-related myocardial ischemia, wherein;

the myocardial ischemia is classified as exertion-related myocardial ischemia if the physiological exertion-response data sensed during the one or more steady state periods shows a non-proportional physiological response with respect to exertion intensity beyond a threshold, wherein below the threshold the physiological exertion-response data shows a proportional physiological response with respect to exertion intensity; and

the myocardial ischemia is classified as non-exertion-related myocardial ischemia if the physiological exertion-response data sensed during the one or more steady state periods show the non-proportional physiological response with respect to exertion intensity with no threshold below which the physiological exertion-response data shows the proportional physiological response with respect to exertion intensity.

23. A method of detecting myocardial ischemia, comprising:

obtaining exertion measurements indicative of physiological exertion;

identifying one or more steady state periods of physiological exertion based on the exertion measurements;

sensing extra-cardiac response data and cardiac response data corresponding to the one or more steady state periods of physiological exertion;

respectively comparing the extra-cardiac response data and the cardiac response data to extra-cardiac response information and cardiac response information associated with equivalent levels of physiological exertion intensity of the one or more steady state periods; and

determining the likelihood that myocardial ischemia occurred during the one or more steady state periods based on the comparison of the extra-cardiac response data to the extra-cardiac response information and the cardiac response data to the cardiac response information.

24. The method of claim 23, wherein:

obtaining exertion measurements comprises obtaining non-circulatory patient internal pressure measurements indicative of static exertion;

identifying the one or more steady state periods of physiological exertion comprises identifying the one or more steady state periods based on the non-circulatory patient internal pressure measurements; and

sensing cardiac response data comprises sensing electro-cardiac response data.

25. A system for detecting ischemia during exertion, comprising:

means for obtaining patient-internal pressure measurements indicative of physiological exertion;

means for identifying steady state periods of physiological exertion based on the patient-internal pressure measurements;

means for assessing the intensity of physiological exertion for each of the identified steady state periods;

means for sensing extra-cardiac response data during identified physiological exertion steady state periods;

means for sensing cardiac response data during identified physiological exertion steady state periods;

means for comparing the extra-cardiac response data corresponding to identified steady state periods of physiological exertion with extra-cardiac response information associated with equivalent physiological exertion intensity;

means for determining the normalcy of the extra-cardiac response data for each steady state period based on the comparison of the extra-cardiac response data and the extra-cardiac response information;

means for comparing the cardiac response data corresponding to identified steady state periods of physiological exertion with cardiac response information associated with equivalent physiological exertion intensity;

means for determining the normalcy of the cardiac response data for each steady state period based on the comparison of the cardiac response data and the cardiac response information; and

means for determining the likelihood of ischemia for one or more of the identified steady state periods of physiological exertion, wherein;

the likelihood of ischemia for each steady state period of the one or more steady state periods is determined to be relatively high if both the extra-cardiac response data and the cardiac response data for the one or more steady state periods are determined to be abnormal;

the likelihood of ischemia for each steady state period of the one or more steady state periods is determined to be relatively moderate if only one of the extra-cardiac response data and the cardiac response data for the one or more steady state periods is determined to be abnormal; and

the likelihood of ischemia for each steady state period of the one or more steady state periods is determined to be relatively low if neither of the extra-cardiac response data and the cardiac response data for the one or more steady state periods are determined to be abnormal.