System and method for efficiently distinguishing among cardiac ischemia, hypoglycemia and hyperglycemia using an implantable medical device and an external system
First Claim
1. A method for use with an implantable medical device for detecting cardiac ischemia within a patient in which the device is implanted, the method comprising:
- detecting ST segment elevation within electrical cardiac signal data;
detecting a preliminary indication of an episode of cardiac ischemia based on ST segment elevation and, in response, sensing additional electrical cardiac signal data;
detecting QTmax intervals and QTend intervals within the additional data;
analyzing the QTmax intervals and the QTend intervals to detect for changes in QTmax intervals and changes in QTend intervals, wherein said changes in QTmax intervals and QTend intervals include lengthening or decreases in said intervals; and
confirming the episode of cardiac ischemia based on the combination of a decrease in the QTmax intervals and a lack of significant change in the QTend intervals, or distinguishing among cardiac ischemia and other potential causes of ST segment deviation based on other changes in the QTmax intervals and the QTend intervals.
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Abstract
Techniques are described for efficiently detecting and distinguishing among cardiac ischemia, hypoglycemia or hyperglycemia based on intracardiac electrogram (IEGM) signals. In one example, a preliminary indication of an episode of cardiac ischemia is detected based on shifts in ST segment elevation within the IEGM. In response, the implanted device then records additional IEGM data for transmission to an external system. The external system analyzes the additional IEGM data to confirm the detection of cardiac ischemia using a more sophisticated analysis procedure exploiting additional detection parameters. In particular, the external system uses detection parameters capable of distinguishing hypoglycemia, hyperglycemia and hyperkalemia from cardiac ischemia, such as QTmax and QTend intervals. Alternatively, the more sophisticated analysis procedure may be performed by the device itself, if it is so equipped. Other examples described herein pertain instead to the detection of atrial fibrillation.
137 Citations
18 Claims
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1. A method for use with an implantable medical device for detecting cardiac ischemia within a patient in which the device is implanted, the method comprising:
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detecting ST segment elevation within electrical cardiac signal data; detecting a preliminary indication of an episode of cardiac ischemia based on ST segment elevation and, in response, sensing additional electrical cardiac signal data; detecting QTmax intervals and QTend intervals within the additional data; analyzing the QTmax intervals and the QTend intervals to detect for changes in QTmax intervals and changes in QTend intervals, wherein said changes in QTmax intervals and QTend intervals include lengthening or decreases in said intervals; and confirming the episode of cardiac ischemia based on the combination of a decrease in the QTmax intervals and a lack of significant change in the QTend intervals, or distinguishing among cardiac ischemia and other potential causes of ST segment deviation based on other changes in the QTmax intervals and the QTend intervals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A system for detecting cardiac ischemia within a patient, the system comprising:
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an implantable medical device comprising; a data acquisition system configured to acquire electrical cardiac signal data; memory configured to record electrical cardiac signal data; an ST segment elevation detector operative to detect ST segment elevation within electrical cardiac signal data; and a cardiac ischemia detector operative to detect a preliminary indication of an episode of cardiac ischemia based on ST segment elevation and, in response, further operative to control the recording of additional cardiac signal data; and a cardiac ischemia confirmation system operative to detect QTmax intervals and QTend intervals within the additional data;
analyze the QTmax intervals and the QTend intervals to detect for changes in QTmax intervals and changes in QTend intervals, wherein said changes in QTmax intervals and QTend intervals include lengthening or decreases in said intervals; andconfirm the episode of cardiac ischemia based on the combination of a decrease in the QTmax intervals and a lack of significant change in the QTend intervals, or distinguish among cardiac ischemia and other potential causes of ST segment deviation based on other changes in the QTmax intervals and the QTend intervals. - View Dependent Claims (16, 17)
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18. A system for use with an implantable medical device for detecting and distinguishing certain medical conditions within a patient in which the device is implanted, the system comprising:
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means for detecting ST segment elevation within electrical cardiac signal data; means for detecting a preliminary indication of an episode of cardiac ischemia based on ST segment elevation and, in response, for controlling the recording of additional electrical cardiac signal data; means for detecting QTmax intervals and QTend intervals within the additional data; means for analyzing the QTmax intervals and the QTend intervals to detect for changes in QTmax intervals and changes in QTend intervals, wherein said changes in QTmax intervals and QTend intervals include lengthening or decreases in said intervals; and means for confirming the episode of cardiac ischemia based on the combination of a decrease in the QTmax intervals and a lack of significant change in the QTend intervals, or distinguishing among cardiac ischemia and hypoglycemia, hyperglycemia and hyperkalemia based on other changes in the QTmax intervals and the QTend intervals.
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Specification