Electrocardiographic baseline filtering and estimation system with bidirectional filter
First Claim
1. A method of estimating a baseline for electrocardiographic signals comprising the steps of:
- acquiring a digitized version of at least one electrocardiographic signal;
storing a predetermined length;
segmenting said digital signals into a series of windows, each of said windows being of said predetermined length;
filtering each of said windows in a forward and a reverse direction by means of bidirectional infinite impulse response (IIR) filter;
storing a present length filtered variable that measures current length filtered in each direction of said bidirectional IIR filter;
comparing said present length with said predetermined length to identify window boundaries where filtering should stop; and
reconstructing each of said filtered window into a synthesized version of said original signal.
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Abstract
A system for filtering stochastic signals as embodied in stress test systems for measuring electrocardiographic (ECG) activity in response to exercise employs a bidirectional Infinite Impulse Response (IIR) filtering process over a predetermined window on a digitized version of an ECG signal to eliminate noise up to the 0.67 Hz frequency range. To eliminate phase shifting distortion in the ECG signal, the IIR filter is applied in a first direction over a predetermined window of the ECG and then applied in a second direction opposite the first direction segment over the identical window. In this manner the phase shift distortion normally associated with IIR filters is completely eliminated and superior bandwidth (as compared to FIR filters) is obtained. The response is achieved fast enough to be used in real time purpose.
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Citations
20 Claims
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1. A method of estimating a baseline for electrocardiographic signals comprising the steps of:
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acquiring a digitized version of at least one electrocardiographic signal; storing a predetermined length; segmenting said digital signals into a series of windows, each of said windows being of said predetermined length; filtering each of said windows in a forward and a reverse direction by means of bidirectional infinite impulse response (IIR) filter; storing a present length filtered variable that measures current length filtered in each direction of said bidirectional IIR filter; comparing said present length with said predetermined length to identify window boundaries where filtering should stop; and reconstructing each of said filtered window into a synthesized version of said original signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of estimating a baseline for electrocardiographic signals comprising the following steps:
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acquiring a digitized version of at least one electrocardiographic signal; segmenting said digitized version into a series of windows, each of said windows being of a predetermined length; filtering each of said windows in a forward and a reverse direction by means of a bidirectional infinite Impulse Response (IIR) filter; storing a predetermined number indicative of a portion of said window to be analyzed; and comparing each of said windows with said predetermined number to identify a portion of said window which is to be analyzed. - View Dependent Claims (10, 11, 12)
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13. A filter for estimating a baseline for electrocardiographic signals comprising:
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acquisition means capable of acquiring a digital representations of an analog electrocardiographic signal; computational means for analyzing said digital representation and dividing said digital representation into a series of individual windows, each of said windows having a predetermined length;
filter means contained within said computational means for implementing a zero phase, bidirectional Infinite Impulse Response (IIR) filtering algorithm upon each of said series of windows in a first forward direction and in a second reverse direction opposite said first forward direction; andcomparison means for determining whether said filtering means has completed filtering in each of said first and said second directions in an amount equal to said predetermined length. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification