Medtronic, Inc.

Shannon D Nelson

Robert W Stadler

Todd Jon Sheldon

Lee Stylos

Mark L Haerle

Kathleen U Crandall

Eric B Ericson

Lori L Echols

Paul R Swanberg

Dan A Hooper

Jewelry

Techniques for detection and treatment of myocardial ischemia are described that monitor both the electrical and dynamic mechanical activity of the heart to detect and verify the occurrence of myocardial ischemia in a more reliable manner. The occurrence of myocardial ischemia can be detected by monitoring changes in an electrical signal such as an ECG or EGM, and changes in dynamic mechanical activity of the heart that are sensed by an accelerometer sensor. The heart acceleration signal can be obtained from an single- or multiple-axis accelerometer and/or a pressure sensor deployed within or near the heart. The techniques correlate contractility changes detected by an accelerometer or pressure sensor with changes in the ST electrogram segment detected by the electrodes to increase the reliability of ischemia detection.

Ischemia detection

Techniques for detection and treatment of myocardial ischemia are described that monitor both the electrical and dynamic mechanical activity of the heart to detect and verify the occurrence of myocardial ischemia in a more reliable manner. The occurrence of myocardial ischemia can be detected by monitoring changes in an electrical signal such as an ECG or EGM, and changes in dynamic mechanical activity of the heart. Dynamic mechanical activity can be represented, for example, by a heart acceleration signal or pressure signal. The electrical signal can be obtained from a set of implanted or external electrodes. The heart acceleration signal can be obtained from an accelerometer or pressure sensor deployed within or near the heart. The techniques correlate contractility changes detected by an accelerometer or pressure sensor with changes in the ST electrogram segment detected by the electrodes to increase the reliability of ischemia detection.

We show how to determine whether there has been an axis shift in an electrocardiogram waveform and how to use this for filtering out bad electrocardiogram information and to modify an adaptive filter that can be used to adapt the filtering of such electrocardiogram information to make it available for determining physiologic conditions even after an axis shift.

Axis shift analysis of electrocardiogram signal parameters especially applicable for multivector analysis by implantable medical devices, and use of same

In using electrogram signals to determine physiologic conditions like ischemia, the bad cardiac cycle information due to noise, axis shifts in the cardiac electrical axis, and the like must be removed if the electrogram signal can be made to be a good indicator. If this is accomplished through the adaptive filtering techniques shown here, the signal can be used to drive a closed loop therapy system responsive to those physiologic conditions discernible from good cardiac cycle electrocardiogram signals.

Ischemia detection during non-standard cardiac excitation patterns

In determining whether a patient has ischemia or other conditions discernible in the variation occurring in the ST portion of the electrocardiogram signal, we filter out bad ST change parameters that are not changing at a rate representative of human ischemia ST change parameter rates of change. This can be used for driving therapy systems to alleviate cardiac ischemia. This filtering can be enhanced by using multiple cardiac electrical vectors for the electrogram signal vectors, and using a determination of Axis shift to modify filter parameters and the expected ranges of precursors to the ST change parameter (an ST change variable) to eliminate bad cardiac cycles, that is cardiac cycle information that may be misleading.

Method for ischemia detection and apparatus for using same

As particularly useful for implantable medical devices we teach a method and apparatus for orienting electrocardiogram input from electrodes of unknown vector orientation. This can be used for locating a fiducial point in the electrocardiogram signal by which other parameterization of measurements taken of the electrocardiogram signal can be made. It is of particular relevance in any cardio electrogram reading where the orientation of the electrogram signal is unknown, and knowledge of the orientation and a fiducial point can form the basis for useful analysis of electrogram signals for detection of physiologic conditions.

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Stacy, MN, United States of America

Shannon D Nelson