Detecting ischemia using an implantable cardiac device based on morphology of cardiac pressure signal

• US 7,648,464 B1
• Filed: 07/19/2006
• Issued: 01/19/2010
• Est. Priority Date: 07/19/2006
• Status: Expired due to Fees

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Boileau, Peter, Gill, Jong, Florio, Joseph J., Min, Xiaoyi, Bornzin, Gene A.
• Primary Examiner(s): Layno; Carl H
• Assistant Examiner(s): Bertram; Eric D
• Application Number:
  US11/458,617
• Time in Patent Office: 1,280 Days
• Field of Search: 600/508
• US Class Current: 600/508
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/29 for permanent or long-term implantation
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/36564 controlled by blood pressure

Abstract

Methods and systems are presented for using an ICD to detect myocardial ischemia. In one embodiment, a method includes sensing a signal indicative of cardiac pressure, measuring a height of the sensed signal at a peak amplitude of the sensed signal, and measuring a duration of the sensed signal. The method further includes indicating an ischemia based on a comparison of a ratio of the height to the duration with a predetermined value. In another embodiment, a method includes sensing a signal indicative of cardiac pressure, determining a derivative signal that is a first derivative of the sensed signal, measuring a maximum positive value of the derivative signal, and measuring a maximum negative value of the derivative signal. The method further includes indicating an ischemia based on a comparison of a ratio of the maximum positive value to the maximum negative value with a predetermined value.

Claims

1. A method for detecting ischemia, comprising:

(a) sensing via an implantable cardiac-rhythm-management device (ICRMD) a signal indicative of cardiac pressure;

(b) measuring via a processor associated with the ICRMD a height of the sensed signal at a peak amplitude of the sensed signal;

(c) measuring via the processor a duration of the sensed signal;

(d) determining via the processor a ratio of the height to the duration; and

(e) indicating via the processor an ischemia based on a comparison of the determined ratio to a predetermined value of the ratio.

2. The method of claim 1, wherein step (b) comprises:

measuring a baseline value of the sensed signal; and

measuring the height of the sensed signal from the baseline value to the peak amplitude.

3. The method of claim 1, wherein step (c) comprises measuring the duration of the sensed signal at an amplitude that is a percentage of the peak amplitude.

4. The method of claim 3, wherein step (c) comprises measuring the duration of the sensed signal at an amplitude that is about fifty percent of the peak amplitude.

5. The method of claim 1, wherein step (e) comprises indicating an ischemia based on a comparison of the ratio to a previously stored value of the ratio.

6. The method of claim 5, wherein step (e) comprises indicating an ischemia when the ratio is less than the previously stored value of the ratio.

7. A system for detecting ischemia, comprising:

means for sensing a signal indicative of cardiac pressure;

means for measuring a height of the sensed signal at a peak amplitude of the sensed signal;

means for measuring a duration of the sensed signal;

means for determining a ratio of the height to the duration; and

means for indicating an ischemia based on a comparison of the determined ratio to a predetermined value of the ratio.

8. A system for detecting ischemia, comprising:

a sensor that generates a signal indicative of cardiac pressure; and

an ischemia detector that;

measures a height of the sensed signal at a peak amplitude of the sensed signal;

measures a duration of the sensed signal;

determines a ratio of the height to the duration; and

indicates an ischemia based on a comparison of the determined ratio to a predetermined value of the ratio.

9. The system of claim 8, wherein the ischemia detector measures a baseline value of the sensed signal and measures the height of the sensed signal from the baseline value to the peak amplitude.

10. The system of claim 8, wherein the ischemia detector measures the duration of the sensed signal at an amplitude that is a percentage of the peak amplitude.

11. The system of claim 10, wherein the ischemia detector measures the duration of the sensed signal at an amplitude that is about fifty percent of the peak amplitude.

12. The system of claim 8, wherein the ischemia detector indicates an ischemia based on a comparison of the ratio to a previously stored value of the ratio.

13. The system of claim 12, wherein the ischemia detector indicates an ischemia when the ratio is less than the previously stored value of the ratio.