System and method for detecting cardiac ischemia based on T-waves using an implantable medical device
First Claim
1. A method for detecting ventricular electrical events comprising:
- sensing near-field signals using a bipolar lead contacting the atria and detecting atrial events therein;
starting a blanking period corresponding to the detected atrial events;
sensing far-field signals, except during blanking periods corresponding to the detected atrial events, using a lead contacting the heart, to provide far-field signals having substantially only ventricular events; and
examining the ventricular events within the far-field signals to identify repolarization events.
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Abstract
A technique is provided for detecting episodes of cardiac ischemia based on an examination of the total energy of T-waves. Since cardiac ischemia is often a precursor to acute myocardial infarction (AMI) or ventricular fibrillation (VF), the technique thereby provides a method for predicting the possible onset of AMI or VF. Briefly, the technique integrates internal electrical cardiac signals occurring during T-waves and then compares the result against a running average. If the result exceeds the average by some predetermined amount, ischemia is thereby detected and a warning signal is provided to the patient. The maximum slope of the T-wave is also exploited. Techniques are also set forth herein for reliably detecting T-waves, which help prevent P-waves from being misinterpreted as T-waves on unipolar sensing channels. The T-wave detection technique may be used in conjunction with ischemia detection or for other purposes.
67 Citations
22 Claims
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1. A method for detecting ventricular electrical events comprising:
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sensing near-field signals using a bipolar lead contacting the atria and detecting atrial events therein; starting a blanking period corresponding to the detected atrial events; sensing far-field signals, except during blanking periods corresponding to the detected atrial events, using a lead contacting the heart, to provide far-field signals having substantially only ventricular events; and examining the ventricular events within the far-field signals to identify repolarization events. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A system for detecting ventricular electrical events comprising:
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a bipolar lead adapted to contact the atria; a bipolar signal processing unit operative to sense near-field signals using the bipolar lead and to detect atrial events therein and to start a blanking period corresponding to the detected atrial events; a lead adapted to contact the heart; a unipolar signal processing unit operative to sense far-field signals, except during blanking periods corresponding to the detected atrial events, using the lead, to provide far-field signals having substantially only ventricular events therein; and a T-wave detection unit operative to examine the ventricular events within the far-field signals to identify ventricular repolarization events (T-waves) therein. - View Dependent Claims (21)
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22. A system for detecting ventricular electrical events comprising:
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means for sensing near-field signals from the atria and detecting atrial events therein; means for starting a blanking period corresponding to the detected atrial events; means for sensing far-field signals from the heart, except during blanking periods corresponding to the detected atrial events, to provide far-field signals having substantially only ventricular events; and means for examining the ventricular events within the far-field signals to identify ventricular repolarization events; means for calculating total energy values of the ventricular repolarization events; and means for detecting cardiac ischemia based on the total energy values.
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Specification