System and method for detecting cardiac ischemia based on T-waves using an implantable medical device
First Claim
1. In an implantable medical device for implant within a patient, a method comprising:
- detecting a plurality of individual T-waves within cardiac signals;
determining an energy value for each of the plurality of individual T-waves;
calculating a plurality of slopes for each of the plurality of individual T-waves;
for each of the plurality of individual T-waves, determining the maximum slope from the plurality of slopes and comparing the maximum slope to a threshold maximum slope and the energy value to a threshold energy value; and
for each of the plurality of individual T-waves, detecting cardiac ischemia when the energy value and the maximum slope of the T-wave exceeds its respective threshold.
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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.
82 Citations
17 Claims
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1. In an implantable medical device for implant within a patient, a method comprising:
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detecting a plurality of individual T-waves within cardiac signals; determining an energy value for each of the plurality of individual T-waves; calculating a plurality of slopes for each of the plurality of individual T-waves; for each of the plurality of individual T-waves, determining the maximum slope from the plurality of slopes and comparing the maximum slope to a threshold maximum slope and the energy value to a threshold energy value; and for each of the plurality of individual T-waves, detecting cardiac ischemia when the energy value and the maximum slope of the T-wave exceeds its respective threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. In an implantable medical device for implant within a patient, a system comprising:
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means for detecting a plurality of T-waves within cardiac signals; means for determining energy values associated with the plurality of T-waves; means for calculating a plurality of slopes for each of the plurality of T-waves and determining a maximum slope for each of the plurality of T-waves from the plurality of slopes associated with the T-wave; means for comparing the maximum slope of each of the plurality of T-waves to a threshold maximum slope and the energy value of each of the plurality of T-waves to a threshold energy value; and means for detecting, for each T-wave, cardiac ischemia when the energy value and the maximum slope of the T-wave exceeds its respective threshold.
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Specification