Method for defining signal templates in implantable cardiac devices
First Claim
1. A method of generating a template for use in morphology analysis of cardiac activity, as represented by electric signals, in an implantable medical device, the implantable medical device comprising a plurality of implantable electrodes coupled to operational circuitry including at least memory and a controller, the method comprising:
- capturing a cardiac signal using implanted electrodes;
forming a preliminary template;
selecting a fiducial point in the preliminary template;
optimizing the preliminary template; and
verifying the preliminary template if the preliminary template provides a valid representation of a cardiac event or, otherwise, discarding the preliminary template;
wherein the step of optimizing the preliminary template comprises masking a portion of the preliminary template by eliminating portions of the preliminary template that do not apparently contain QRS information of the cardiac signal; and
wherein the step of verifying the preliminary template comprises;
capturing a cardiac signal and identifying a secondary template;
selecting a fiducial point in the secondary template in a manner consistent with the step of selecting a fiducial point in the preliminary template, such that both fiducial points are selected in a similar manner;
optimizing the secondary template in a manner consistent with the step of optimizing the preliminary template; and
comparing the secondary template to the preliminary template to determine whether the two are sufficiently similar to imply that the preliminary template provides a valid representation of a cardiac event.
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Accused Products
Abstract
Template formation methods for use in implantable cardiac rhythm management devices. In an illustrative method, a signal is captured in an implanted cardiac rhythm management device, and parameters for analysis of the captured signal are then defined. Then, in the example, additional signals can be captured and used to either verify or discard the captured signal defined parameters. The template formation methods provide for creating a robust template to compare with sensed cardiac complexes. Devices and systems configured to perform template formation and verification methods are also shown.
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Citations
18 Claims
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1. A method of generating a template for use in morphology analysis of cardiac activity, as represented by electric signals, in an implantable medical device, the implantable medical device comprising a plurality of implantable electrodes coupled to operational circuitry including at least memory and a controller, the method comprising:
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capturing a cardiac signal using implanted electrodes; forming a preliminary template; selecting a fiducial point in the preliminary template; optimizing the preliminary template; and verifying the preliminary template if the preliminary template provides a valid representation of a cardiac event or, otherwise, discarding the preliminary template; wherein the step of optimizing the preliminary template comprises masking a portion of the preliminary template by eliminating portions of the preliminary template that do not apparently contain QRS information of the cardiac signal; and wherein the step of verifying the preliminary template comprises; capturing a cardiac signal and identifying a secondary template; selecting a fiducial point in the secondary template in a manner consistent with the step of selecting a fiducial point in the preliminary template, such that both fiducial points are selected in a similar manner; optimizing the secondary template in a manner consistent with the step of optimizing the preliminary template; and comparing the secondary template to the preliminary template to determine whether the two are sufficiently similar to imply that the preliminary template provides a valid representation of a cardiac event. - View Dependent Claims (2, 3, 4, 5)
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6. An implantable medical device comprising:
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means for capturing cardiac signals from implanted locations; means for performing data analysis; and means for data storage in the implantable medical device; wherein the means for performing data analysis is configured to perform a method comprising; sampling a signal captured using the means for capturing; identifying a peak in the sampled signal as a fiducial point; configuring a preliminary template using the fiducial point by identifying a number of template samples on either side of the fiducial point, identifying QRS start and end points using monotonic segments on either side of the fiducial point, and masking or discarding portions of the captured cardiac signal falling outside of the identified QRS start and end points; testing the preliminary template by comparing it to a similarly configured, later captured cardiac signal, with the comparing step leading to verification of the preliminary template or rejection of the preliminary template; and if the preliminary template is verified, storing the preliminary template using the means for data storage. - View Dependent Claims (7, 8, 9)
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10. A method of characterizing a normal sinus rhythm template in an implantable medical device, the implantable medical device comprising a plurality of implantable electrodes coupled to operational circuitry including at least memory and a controller, the method comprising:
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capturing a cardiac signal from implanted electrodes; identifying one or more peaks within the captured cardiac signal; selecting one of the one or more peaks within the captured cardiac signal as a fiducial point; identifying an early monotonic segment occurring prior to the fiducial point; identifying a late monotonic segment occurring following the fiducial point; defining a preliminary template as including data captured from approximately the beginning of the early monotonic segment to approximately the end of the late monotonic segment, while excluding at least some portion of the captured cardiac signal from the preliminary template; establishing a configuration for the preliminary template including a duration from the start of the early monotonic segment to the fiducial point and a duration from the fiducial point to the end of the late monotonic segment; comparing the preliminary template to a number of similarly configured captured cardiac signals to determine whether the preliminary template accurately characterizes normal cardiac function for the patient; and
;if so, storing the preliminary template as a Normal Sinus Rhythm template;
orif not, rejecting the preliminary template. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A method of establishing a Notched Cardiac Signal Template for a patient having a cardiac rhythm with a QRS complex segment characterized by a notch for use in an implantable cardiac stimulus device comprising a plurality of implantable electrodes coupled to operational circuitry including at least memory and a controller, the notch including first and second peaks separated by a region of lesser amplitude, the method comprising:
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determining whether the notch exists by observing whether a captured cardiac preliminary template comprising a plurality of sequential samples of cardiac signal includes first and second peaks that are; a) separated in amplitude by less than a notch amplitude threshold;
orb) separated in time by less than a notch time threshold; if so, identifying a notched signal and establishing the preliminary template as follows; selecting the first peak as a fiducial point for the preliminary template; identifying a QRS width using times associated with the starting time of the largest monotonic segment in the preliminary template preceding the fiducial point and the ending time of the largest monotonic segment in the preliminary template that occurs after the fiducial point; and masking the preliminary template to correspond to the identified QRS width; then verifying the preliminary template for the notched signal by; i) capturing at least a detected cardiac event comprising a plurality of sequential samples of cardiac signal; ii) identifying a fiducial point in the detected cardiac event in the same manner used to identify a fiducial point in the preliminary template; iii) masking the detected cardiac event around the fiducial point in the same manner used to mask the preliminary template; and iv) comparing the masked detected cardiac event to the masked preliminary template and; if the detected cardiac event correlates to the preliminary template, determining that the detected cardiac event suggests verification of the preliminary template;
orif the detected cardiac event does not correlate to the preliminary template, discarding the preliminary template. - View Dependent Claims (17, 18)
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Specification