Method and apparatus for filtering electrocardiogram (ECG) signals to remove bad cycle information and for use of physiologic signals determined from said filtered ECG signals
First Claim
1. A method for filtering out information from invalid or undesirable cardiac cycle signals in a series of cardiac cycle signals present in a cardiac electrogram signal to eliminate consideration of information from said invalid cycle in evaluating said cardiac electrogram signal, said method employing adaptive amplitude thresholds and comprising a cycle repeated for each cardiac cycle, comprising the steps:
- a) for a given cardiac cycle, collecting a selected set of characteristic portions of the electrocardiogram signal and sampling specific point locations within said portions, and thereby measuring the electrocardiogram amplitude at said specific sampled point locations and producing measured values for each point location,b) parameterizing each said sampled selected set of portions by calculating a plurality of characteristic parameter values based on said measured values of said point locations in said set of portions collected in step a for said given cardiac cycle,c) employing a plurality of previously calculated expected value ranges, one said range for each characteristic parameter value from step b, to determine whether each said parameter value of said plurality of characteristic parameter values is within said previously calculated expected range for said each parameter,d) determining cardiac cycle validity for said given cardiac cycle from which said set of portions was collected in step a, based on a determination that a predetermined sufficient number of said plurality of parameters for a cardiac cycle are within said ranges, ande) if said given cardiac cycle is determined to have been valid, then, updating by recalculating said previously calculated expected ranges based on the characteristic parameter values determined in step b so as to provide flexibility to said adaptive amplitude thresholds and to provide data to adjust said ranges.
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Accused Products
Abstract
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.
507 Citations
32 Claims
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1. A method for filtering out information from invalid or undesirable cardiac cycle signals in a series of cardiac cycle signals present in a cardiac electrogram signal to eliminate consideration of information from said invalid cycle in evaluating said cardiac electrogram signal, said method employing adaptive amplitude thresholds and comprising a cycle repeated for each cardiac cycle, comprising the steps:
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a) for a given cardiac cycle, collecting a selected set of characteristic portions of the electrocardiogram signal and sampling specific point locations within said portions, and thereby measuring the electrocardiogram amplitude at said specific sampled point locations and producing measured values for each point location, b) parameterizing each said sampled selected set of portions by calculating a plurality of characteristic parameter values based on said measured values of said point locations in said set of portions collected in step a for said given cardiac cycle, c) employing a plurality of previously calculated expected value ranges, one said range for each characteristic parameter value from step b, to determine whether each said parameter value of said plurality of characteristic parameter values is within said previously calculated expected range for said each parameter, d) determining cardiac cycle validity for said given cardiac cycle from which said set of portions was collected in step a, based on a determination that a predetermined sufficient number of said plurality of parameters for a cardiac cycle are within said ranges, and e) if said given cardiac cycle is determined to have been valid, then, updating by recalculating said previously calculated expected ranges based on the characteristic parameter values determined in step b so as to provide flexibility to said adaptive amplitude thresholds and to provide data to adjust said ranges. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. Apparatus for filtering out information from invalid cardiac cycle signals in a series of cardiac cycle signals present in a cardiac electrogram signal to eliminate consideration of information from said invalid cycle in evaluating said cardiac electrogram signal, said cardiac electrogram signal being received by said apparatus through a plurality of electrical leads connected to receive said cardiac electrogram signal in a plurality of electrical vectors, said apparatus comprising:
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an electrogram reading device connected to said plurality of electrodes for sensing the amplitude variation in the electrical signal of a heart, a sampling and digitizing circuit for digitizing samples of said cardiac electrical amplitude signal and to provide an output stream of digitized sample point values representative of said samples, a V-event detection circuit for generating a V-event signal at its output indicating that a ventricular event has occurred, a buffer circuit for holding a set of point values that are temporally related to a time when said V-event signal is output from said V-event detection circuit, a fiducial point determining circuit for determining which of said point values in said set of point values is a fiducial, a subset determining and selecting circuit for determining based at least in part on a temporal relative location of said determined R-peak point to said set of point values which subset of said set of point values to select and selecting them, a parameterizing processor circuit for producing a set of parameter values related to said set of point values selected and determined by said subset determining circuit, an expected range value recalculating circuit for employing said set of parameter values and said pre-calculated expected ranges to produce new pre-calculated expected ranges to produce new pre-calculated expected range values for a next set of parameter values to be compared with a comparison circuit for comparing said pre-calculated expected ranges with each parameter value from said set of parameter values to determine if it is within its expected range and producing a validity value as an output, a cycle validity determining circuit for determining if said validity value is sufficient to employ said set of parameter values for determining a physiologic condition and for recalculating said set of expected ranges by said recalculating circuit and for providing a flag value signal representing whether the determination of cycle validity is sufficient. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32)
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Specification