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

• US 8,162,842 B2
• Filed: 12/07/2009
• Issued: 04/24/2012
• Est. Priority Date: 07/19/2006
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Gill, Jong, Boileau, Peter, Bornzin, Gene A., Florio, Joseph J., Min, Xiaoyi
• Primary Examiner(s): Bertram, Eric D.
• Application Number:
  US12/632,689
• Publication Number:
  US 20100081952A1
• Time in Patent Office: 869 Days
• Field of Search: 600/508, 600/515
• 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. One such method includes sensing via an implantable cardiac-rhythm-management device (ICRMD) a signal indicative of cardiac pressure; determining via a processor associated with the ICRMD, a derivative signal that is a first derivative of the sensed signal; measuring via the processor, a maximum positive value of the derivative signal; measuring via the processor, a maximum negative value of the derivative signal; and indicating via the processor, 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) determining via a processor associated with the ICRMD, a derivative signal that is a first derivative of the sensed signal;

(c) measuring via the processor, a maximum positive value of the derivative signal;

(d) measuring via the processor, a maximum negative value of the derivative signal; and

(e) indicating via the processor, an ischemia when a ratio of the maximum positive value to the maximum negative value is less than a previously stored value of the ratio during a non-ischemic event.

2. A method for detecting ischemia, comprising:

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

(b) determining via a processor associated with the ICRMD, a derivative signal that is a first derivative of the sensed signal;

(c) measuring via the processor, a maximum positive value of the derivative signal;

(d) measuring via the processor, a maximum negative value of the derivative signal; and

(e) indicating via the processor, an ischemia based on a comparison of a ratio of the maximum positive value to the maximum negative value with a predetermined value;

wherein the derivative signal is an ensemble average of a plurality of separately determined derivative signals.

3. The method of claim 2 wherein:

steps a) through d) are repeated a plurality of times to obtain a corresponding plurality of ratios of maximum positive value to maximum negative value; and

step (e) comprises comparing each ratio with the predetermined value and indicating an ischemia when a predetermined number of consecutively obtained ratios deviates from the predetermined value.

4. The method of claim 2 wherein:

steps a) through d) are repeated a plurality of times to obtain a corresponding plurality of ratios of maximum positive value to maximum negative value; and

step (e) comprises comparing each ratio with the predetermined value and indicating an ischemia when a predetermined percentage of consecutively obtained ratios deviates from the predetermined value.

5. A system for detecting ischemia, comprising:

means for sensing a signal indicative of cardiac pressure;

means for determining a derivative signal that is a first derivative of the sensed signal;

means for measuring a maximum positive value of the derivative signal;

means for measuring a maximum negative value of the derivative signal; and

means for indicating an ischemia when a ratio of the maximum positive value to the maximum negative value is less than a previously stored value of the ratio during a non-ischemic event.

6. A system for detecting ischemia, comprising:

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

an ischemia detector that determines a derivative signal that is a first derivative of the sensed signal;

measures a maximum positive value of the derivative signal;

measures a maximum negative value of the derivative signal; and

indicates an ischemia when a ratio of the maximum positive value to the maximum negative value is less than a previously stored value of the ratio during a non-ischemic event.