CN110558974A - Electrocardiogram signal analysis method based on extreme value energy decomposition method - Google Patents
Electrocardiogram signal analysis method based on extreme value energy decomposition method Download PDFInfo
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Abstract
the invention discloses an electrocardiogram signal analysis method based on an extreme value energy decomposition method, which comprises the steps of obtaining an ECG signal x (t) in an unknown state at a given time and a given sampling frequency; carrying out denoising preprocessing on the ECG signal x (t); taking the denoised ECG signal x (t) as an original signal, decomposing the original signal x (t) into n extreme value modal function components and a margin, decomposing the original signal x (t) into n extreme value modal function components representing components of different frequency bands of the original signal, and judging whether the ECG signal is an abnormal electrocardiogram signal or not according to the n extreme value modal function components. The invention adopts an extreme value energy decomposition method to analyze an ECG signal, decomposes an original signal into a plurality of components, namely an extreme value component function, and calculates the energy of each component to obtain the energy distribution of the component.
Description
Technical Field
The invention relates to electrocardiogram signal analysis, in particular to an electrocardiogram signal analysis method based on an extreme value energy decomposition method.
background
Physiological signals are generated by the interaction of multiple systems of a living body, and the time and the intensity of the action of different systems are different, so that the physiological signals have complexity in time and space. ECG (electrocardiograph) signals reflect the electrical activity process of heart beats, and have important guiding significance for basic heart functions and disease diagnosis. The ECG signal comprises several different wave groups of P wave, QRS wave, T wave and the like, each wave group comprises different frequency components, and the energy distribution proportion of the different frequency components in the ECG signal is different. Researches show that 99% of energy of an ECG signal is concentrated in a range of 0-40 Hz, and the frequency distribution range and the energy ratio have certain rules for different wave groups. The ECG signal energy distribution is changed due to heart diseases, and the study on the ECG energy distribution has important clinical guiding significance for revealing the function change caused by the heart diseases.
in the energy (spectrum) research of the ECG, the traditional classical methods such as spectrum analysis, time domain analysis and the like are many, however, the ECG signal is a non-stationary nonlinear signal, and the traditional frequency domain analysis method is more suitable for analyzing a stationary signal and only can give global frequency information. In addition, when the frequency domain is segmented, the traditional method is divided according to a plurality of fixed frequency points, and the fluctuation characteristics of different signals and the difference between the signals are not considered.
Therefore, it is desired to solve the above problems.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide an electrocardiogram signal analysis method based on an extreme value energy decomposition method, which can intuitively reflect the real rule of electrocardiogram energy distribution and signal fluctuation by adopting less data.
The technical scheme is as follows: in order to achieve the above purpose, the invention discloses an electrocardiogram signal analysis method based on an extreme value energy decomposition method, which comprises the following steps:
(1) Acquiring an ECG signal x (t) of an unknown state at a given time and a given sampling frequency;
(2) Carrying out denoising pretreatment on the ECG signal x (t); the specific method of pretreatment is as follows: filtering the ECG signal by a 40Hz zero-phase FIR low-pass filter to eliminate high-frequency noise, and then removing baseline drift by a median filter;
(3) Taking the denoised ECG signal x (t) as an original signal, solving all local extreme points of the original signal, and then connecting all the extreme points and all the minimum points of the original signal by adopting a spline curve to respectively form an upper envelope line emaxAnd a lower envelope eminObtaining the envelope mean value signal m (t) ═ e of the upper envelope line and the lower envelope linemax+emin)/2；
(4) Subtracting the envelope mean value signal m (t) from the original signal x (t) to obtain h (t) ═ x (t) -m (t); then judging whether h (t) meets the judgment condition of the extreme value modal function, if not, returning h (t) to the step (3) as an original signal until hk(t) if the condition for determining the extremum mode function is satisfied, c is recorded1(t)＝hk(t) as a first extreme modal function component;
(5) Subtracting the first extreme mode function component c from the original signal x (t)1(t) obtaining the residue r1(t)＝x(t)-c1(t) then judging hk(t) whether a stopping criterion is met, and if not, r1(t) as a new original sequence x (t), returning to steps (3) and (4) until hk(t) satisfying the stopping criterion, obtaining the 2 nd, 3 rd, … th, n extreme value modal function components and the margin rn(t) the original signal x (t) is then decomposed into n extreme modal function components and a residual, i.e.
(6) Opposite polar mode function component ci(t), i is 1, 2, …, n, and the center frequency of each extreme modal function component is obtained by performing spectrum analysis;
(7) N extreme value modal function components obtained by decomposing the original signal x (t) represent components of different frequency bands of the original signal, and then the energy of each component is calculated
Ei＝∫|ci(t)|2dt，i＝1，2，…，n
normalizing each energy value to obtain a normalized energy distribution vector
pi＝Ei/E，i＝1，2，….，n
Wherein the content of the first and second substances,first component p1representing the energy of the highest frequency band, representing the proportion of the energy distribution of the signal in the highest frequency band, the last component pnRepresenting the proportion of the energy distribution of the signal in the lowest frequency band range; drawing a normalized energy distribution graph according to the normalized energy distribution vector, wherein the abscissa represents component levels, the ordinate represents normalized energy distribution vector values, the curve represents an average value, and the error bar represents a standard deviation;
(8) Normalized energy distribution vector p of ECG signal of unknown stateiNormalized energy distribution vector p with standard ECG signalicarrying out significance detection to obtain a probability value P on each extreme value modal function componentiDetermining a probability value P of the first extreme mode function component1and a probability value P on the second extremum mode function component2If the signal is smaller than the probability standard value, returning to the step (1) to acquire the signal again;
(9) In the presence of a catalyst satisfying P1and P2if the energy distribution vector p of the first extreme mode function component is smaller than the standard value of the probability1Energy distribution vector p smaller than second extreme modal function component2Then the ECG signal is determined to be an abnormal ECG signal.
Wherein the minimum data amount N of the original signal x (t) is 2n+1and n is the number of the decomposed extreme mode function components.
Preferably, the condition for determining the extreme mode function in step (4) is: (a) in the whole data sequence, the number of the extreme points is equal to or different from the number of the zero-crossing points by one; (b) and the upper and lower envelopes are symmetric with respect to the time axis at any time.
Further, h in said step (5)k(t) the formula for satisfying the stopping criterion is:
Epsilon represents a screening threshold, and is taken to be 0.2-0.3.
Further, the standard value of the probability in the step (8) and the step (9) is 0.05.
and (3) the repetition frequency of the 6 th extreme value modal function component waveform obtained in the step (5) is the human heart rate, namely the cardiac cycle.
has the advantages that: compared with the prior art, the invention has the following remarkable advantages: the invention adopts an Extreme Energy Decomposition (EED) method to analyze an ECG signal, decomposes an original signal into a plurality of components, namely an extreme component function, calculates the Energy of each component to obtain the Energy distribution of the component, and can judge whether the signal is normal or not according to the comparison of Energy values of different levels of components; the invention can decompose the signal into different time-level signals from high frequency to low frequency according to the fluctuation rule of the biomedical signal; and for the ECG signal, the repetition frequency can be determined from a special level thereof, namely the heart rate value (comprising an instantaneous heart rate value and an average heart rate value) of the ECG signal, and the method for obtaining the heart rate value is more accurate than the traditional method; the data length obtained by the extremum decomposition on all levels is the same, so that the data length cannot be reduced, and the extremum decomposition method can be used for short-time data analysis, namely, an accurate result can be obtained by analysis with less data quantity; the EED is not susceptible to noise for different levels of component energy analysis.
Drawings
FIG. 1 is a diagram of an original signal in the present invention;
FIG. 2 is a diagram illustrating the envelope of the original signal according to the present invention;
FIG. 3 is a schematic diagram of a subtracted envelope mean signal of an original signal in accordance with the present invention;
FIG. 4 is a schematic diagram of obtaining a first extreme modal function component according to the present invention;
FIG. 5 is a schematic flow chart of the extreme energy decomposition method of the present invention;
FIG. 6 is an EED decomposition diagram of ECG signal in embodiment 1 of the present invention;
FIG. 7 is a spectrum chart of an ECG signal in embodiment 1 of the present invention;
FIG. 8 is an EED decomposition diagram of ECG signal in embodiment 2 of the present invention;
FIG. 9 is a time-frequency diagram of ECG of a healthy person in the practice 2 of the present invention;
FIG. 10 is a time-frequency plot of the ECG of a CHF patient in accordance with practice 2 of the present invention.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
As shown in fig. 1, fig. 2, fig. 3, fig. 4 and fig. 5, the electrocardiogram signal analyzing method based on the extreme value energy decomposition method of the present invention comprises the following steps:
(1) Acquiring an ECG signal x (t) of an unknown state at a given time and a given sampling frequency; the minimum data amount N of the original signal x (t) is 2n+1wherein n is the number of resolved extremum modal function components;
(2) Carrying out denoising pretreatment on the ECG signal x (t); the specific method of pretreatment is as follows: filtering the ECG signal by a 40Hz zero-phase FIR low-pass filter to eliminate high-frequency noise, and then removing baseline drift by a median filter;
(3) Taking the denoised ECG signal x (t) as an original signal, solving all local extreme points of the original signal, and then connecting all the extreme points and all the minimum points of the original signal by adopting a spline curve to respectively form an upper envelope line emaxAnd a lower envelope eminObtaining the envelope mean value signal m (t) ═ e of the upper envelope line and the lower envelope linemax+emin)/2；
(4) Subtracting the envelope mean value signal m (t) from the original signal x (t) to obtain h (t) ═ x (t) -m (t); then judgeAnd (4) judging whether h (t) meets the judgment condition of the extreme value modal function, if not, returning h (t) serving as an original signal to the step (3) until hk(t) if the condition for determining the extremum mode function is satisfied, c is recorded1(t)＝hk(t) as a first extreme modal function component; the determination condition of the extreme value modal function is as follows: (a) in the whole data sequence, the number of the extreme points is equal to or different from the number of the zero-crossing points by one; (b) at any time, the upper envelope line and the lower envelope line are symmetrical relative to a time axis;
(5) Subtracting the first extreme mode function component c from the original signal x (t)1(t) obtaining the residue r1(t)＝x(t)-c1(t) then judging hk(t) whether a stopping criterion is met, and if not, r1(t) as a new original sequence x (t), returning to steps (3) and (4) until hk(t) satisfying the stopping criterion, obtaining the 2 nd, 3 rd, … th, n extreme value modal function components and the margin rn(t) the original signal x (t) is then decomposed into n extreme modal function components and a residual, i.e.
wherein h isk(t) the formula for satisfying the stopping criterion is:
epsilon represents a screening threshold, and is taken to be 0.2-0.3; the extremum modal decomposition that satisfies the stopping criterion then satisfies the following two conditions: (a) finally obtained extreme value modal function component cn(t) or the remainder rn(t) is less than a predetermined threshold; (b) residual signal rn(t) becomes a monotonous signal from which an extreme mode function signal cannot be extracted again;
(6) Opposite polar mode function component ci(t), i is 1, 2, …, n, and the center frequency of each extreme modal function component is obtained by performing spectrum analysis;
(7) N extreme value modal function components obtained by decomposing the original signal x (t) represent components of different frequency bands of the original signal, and then the energy of each component is calculated
Ei＝∫|ci(t)|2dt，i＝1，2，…，n
Normalizing each energy value to obtain a normalized energy distribution vector
pi＝Ei/E，i＝1，2，…，n
Wherein the content of the first and second substances,First component p1representing the energy of the highest frequency band, representing the proportion of the energy distribution of the signal in the highest frequency band, the last component pnRepresenting the proportion of the energy distribution of the signal in the lowest frequency band range; drawing a normalized energy distribution graph according to the normalized energy distribution vector, wherein the abscissa represents component levels, the ordinate represents normalized energy distribution vector values, the curve represents an average value, and the error bar represents a standard deviation;
(8) Normalized energy distribution vector p of ECG signal of unknown stateiNormalized energy distribution vector p with standard ECG signaliCarrying out significance detection to obtain a probability value P on each extreme value modal function componentiDetermining a probability value P of the first extreme mode function component1and a probability value P on the second extremum mode function component2If the signal is smaller than the probability standard value, returning to the step (1) to acquire the signal again; wherein the probability standard value is selected to be 0.05;
(9) In the presence of a catalyst satisfying P1And P2if the energy distribution vector p of the first extreme mode function component is smaller than the standard value of the probability1energy distribution vector p smaller than second extreme modal function component2Then the ECG signal is determined to be an abnormal ECG signal.
The repetition frequency of the 6 th extreme value modal function component waveform obtained by the invention is the heart rate of the human body, namely the cardiac cycle.
The Extreme Energy Decomposition (EED) method adopted by the invention is a method based on the concept of an extreme mode function, wherein the extreme mode function is a signal with single frequency which simultaneously meets the following two conditions:
(a) The number of extreme points (including maxima and minima) and the number of zero-crossing points must be equal or differ by at most one throughout the data sequence;
(b) At any moment, the average value of an upper envelope line formed by the local maximum value points and a lower envelope line formed by the local minimum value points is zero, namely the local upper envelope line and the local lower envelope line are locally symmetrical relative to a time axis;
The above two conditions, condition (a) is similar to the requirement of the gaussian normal stationary process for the traditional narrow band, and condition (b) ensures that the instantaneous frequency calculated by the extreme value modal function has physical significance.
the standard selection of the extreme value modal function decomposition termination is moderate, and the conditions are too strict, so that the last extreme value modal function components lose significance; conditions are too loose, which can result in loss of useful components; in practical application, the number of layers of the extremum modal function components to be decomposed can be set according to requirements, and when the number of layers of decomposition is met, the calculation is terminated.
Example 1
the invention discloses an electrocardiogram signal analysis method based on an extreme value energy decomposition method, which comprises the following steps:
(1) Acquiring an ECG signal x (t) at a given time and a given sampling frequency from a healthy person normal sinus database nsrdb of physionet; the data length is 8s, and the minimum data amount needed by the original signal x (t) is N-2n+1＝29Wherein n is the number of the decomposed extreme mode function components, and n is 8;
(2) Carrying out denoising pretreatment on the ECG signal x (t); the specific method of pretreatment is as follows: because the ECG energy is mainly concentrated in 0-40 Hz, the ECG signal is filtered by a 40Hz zero-phase FIR low-pass filter to eliminate high-frequency noise, and then baseline drift is removed by a median filter;
(3) and determining all local parts of the original signal by using the denoised ECG signal x (t) as the original signalExtreme points, and connecting all the extreme points and all the minimum points of the original signal by spline curves to form an upper envelope line e respectivelymaxAnd a lower envelope eminobtaining the envelope mean value signal m (t) ═ e of the upper envelope line and the lower envelope linemax+emin)/2；
(4) Subtracting the envelope mean value signal m (t) from the original signal x (t) to obtain h (t) ═ x (t) -m (t); then judging whether h (t) meets the judgment condition of the extreme value modal function, if not, returning h (t) to the step (3) as an original signal until hk(t) if the condition for determining the extremum mode function is satisfied, c is recorded1(t)＝hk(t) as a first extreme modal function component; the determination condition of the extreme value modal function is as follows: (a) in the whole data sequence, the number of the extreme points is equal to or different from the number of the zero-crossing points by one; (b) at any time, the upper envelope line and the lower envelope line are symmetrical relative to a time axis;
(5) subtracting the first extreme mode function component c from the original signal x (t)1(t) obtaining the residue r1(t)＝x(t)-c1(t) adding r1(t) as a new original sequence x (t), returning to the steps (3) and (4) to obtain 2 nd, 3 rd, … th and 8 th extreme value modal function components and a margin r8(t) the original signal x (t) is then decomposed into 8 extreme modal function components and a residual, i.e.
As shown in FIG. 6, the ECG signal can be divided into three wave groups of P, QRS and T waves according to the characteristics of the waveform; c can be obtained by decomposing 8 extreme value modal function components1(t) and c2(t) the component of the decomposition of the QRS complex with the highest frequency representing the highest frequency in the ECG signal, c3(t) decomposition components representing superposition of high frequency QRS complex and P wave in ECG signal, c4(T) decomposition components of the superposition of high-frequency QRS complex, P-wave and T-wave in ECG signal, c5(T) decomposition components representing superposition of QRS complex, P wave and low frequency part of T wave in ECG signal, c6(t) representing heart beat rhythmCardiac cycle, c7(t) and c8(t) represents the heart's circadian rhythm on a larger time scale representative of the long-term rhythm of the heart; observing the amplitude of the signal, wherein the component with the highest frequency has higher amplitude and the highest energy; the component with the lowest frequency has lower amplitude and lower energy;
(6) Opposite polar mode function component ci(t), i is 1, 2, …, 8, and performing spectrum analysis to obtain the center frequency of each extreme modal function component, as shown in table 1; wherein pair c1Performing spectrum analysis to obtain a spectrogram shown in FIG. 7, and obtaining c1The center frequency of (A) is about 20Hz, and the main frequency is concentrated in the range of 15-25 Hz; as shown in the existing research, the frequency spectrum range of the P wave is 0-18 Hz (+ -3 Hz), and the energy is mainly concentrated in 5-12 Hz; the QRS wave has a frequency spectrum range of 0-37 Hz (+ -5 Hz), and energy is mainly concentrated in 6-18 Hz; the frequency spectrum range of the T wave is 0-8 Hz (+ -2 Hz), and the energy is mainly concentrated in 0-8 Hz. As can be seen from comparison of Table 1, the frequency band of QRS complex mainly includes c1、c2Two components, P-waves containing predominantly c3，c4two components, T-waves containing predominantly c4～c8The component part of (a). It should be noted that the inclusion is not intended to mean that each component is determined by a specific ECG complex (P, QRS, T wave) or that each ECG complex is included in a specific component, and that the above complex-energy relationship is a primary correspondence, not all. E.g. c representing the low frequency part5～c8The components are determined by the superposition of the low frequency portions of the individual ECG complexes, rather than by a particular ECG complex. The extreme value modal function component and the extreme value modal function components of all layers of the invention both show that the extreme value modal function component of the ECG can represent a certain ECG wave group fluctuation condition and reflect the fluctuation rule of the ECG on different layers; compared with the traditional frequency domain analysis method, the EED method can directly observe the fluctuation condition of the ECG on each level, and is very intuitive. The repetition frequency of the obtained 6 th extreme value modal function component waveform is the human heart rate, namely the cardiac cycle.
TABLE 1 center frequencies of respective extreme modal function components
example 2
The EED analysis method is used to analyze the energy distribution of the ECG at different levels in healthy persons and CHF patients.
an electrocardiogram signal analysis method based on an extreme value energy decomposition method for healthy people comprises the following steps:
(1) Acquiring an ECG signal x (t) with the data length of 10s and the sampling frequency of 128Hz from a normal sinus database nsrdb of physionet; where the nsrdb database contains 18 healthy persons (age 34.3 ± 8.4) and the minimum amount of data N required for the raw signal x (t) is 2n+1＝29Wherein n is the number of the decomposed extreme mode function components, and n is 8;
(2) Carrying out denoising pretreatment on the ECG signal x (t); the specific method of pretreatment is as follows: because the ECG energy is mainly concentrated in 0-40 Hz, the ECG signal is filtered by a 40Hz zero-phase FIR low-pass filter to eliminate high-frequency noise, and then baseline drift is removed by a median filter;
(3) Taking the denoised ECG signal x (t) as an original signal, solving all local extreme points of the original signal, and then connecting all the extreme points and all the minimum points of the original signal by adopting a spline curve to respectively form an upper envelope line emaxAnd a lower envelope eminObtaining the envelope mean value signal m (t) ═ e of the upper envelope line and the lower envelope linemax+emin)/2；
(4) subtracting the envelope mean value signal m (t) from the original signal x (t) to obtain h (t) ═ x (t) -m (t); then judging whether h (t) meets the judgment condition of the extreme value modal function, if not, returning h (t) to the step (3) as an original signal until hk(t) if the condition for determining the extremum mode function is satisfied, c is recorded1(t)＝hk(t) as a first extreme modal function component; the determination condition of the extreme value modal function is as follows: (a) in the whole data sequence, the number of the extreme points is equal to or different from the number of the zero-crossing points by one; (b) get on and off the bag at any timeThe crosswinding is symmetrical with respect to the time axis;
(5) Subtracting the first extreme mode function component c from the original signal x (t)1(t) obtaining the residue r1(t)＝x(t)-c1(t) adding r1(t) as a new original sequence x (t), returning to the steps (3) and (4) to obtain 2 nd, 3 rd, … th and 8 th extreme value modal function components and a margin r8(t) the original signal x (t) is then decomposed into 8 extreme modal function components and a residual, i.e.
(6) Opposite polar mode function component ci(t), i is 1, 2, …, 8, and performing spectrum analysis to obtain the center frequency of each extreme value modal function component, and obtaining a frequency domain analysis result graph;
(7) 8 extreme value modal function components obtained by decomposing the original signal x (t) represent components of different frequency bands of the original signal, and then the energy of each component is calculated
Ei＝∫|ci(t)|2dt，i＝1，2，…，8
Normalizing each energy value to obtain a normalized energy distribution vector
pi＝Ei/E，i＝1，2，…，8
wherein the content of the first and second substances,First component p1representing the energy of the highest frequency band, representing the proportion of the energy distribution of the signal in the highest frequency band, the last component pnrepresenting the proportion of the energy distribution of the signal in the lowest frequency range.
An electrocardiogram signal analysis method based on an extreme value energy decomposition method for CHF patients comprises the following steps:
(1) Acquiring an ECG signal x (t) with a data length of 10s and a sampling frequency of 128Hz from a CHF database chfdb, wherein the chfdb database comprises 15 CHF patients (age 58.8 +/-9.1) and the minimum number of raw signals x (t) is requiredData amount N is 2n+1＝29wherein n is the number of the decomposed extreme mode function components, and n is 8;
The method comprises the following steps of (2) carrying out denoising pretreatment on an ECG signal x (t), wherein the specific method of the pretreatment is that the ECG signal is filtered by a 40Hz zero-phase FIR low-pass filter to eliminate high-frequency noise because the ECG energy is mainly concentrated in 0-40 Hz, and then the baseline drift is removed by a median filter;
(3) Taking the denoised ECG signal x (t) as an original signal, solving all local extreme points of the original signal, and then connecting all the extreme points and all the minimum points of the original signal by adopting a spline curve to respectively form an upper envelope line emaxAnd a lower envelope eminObtaining the envelope mean value signal m (t) ═ e of the upper envelope line and the lower envelope linemax+emin)/2；
(4) Subtracting the envelope mean value signal m (t) from the original signal x (t) to obtain h (t) ═ x (t) -m (t); then judging whether h (t) meets the judgment condition of the extreme value modal function, if not, returning h (t) to the step (3) as an original signal until hk(t) if the condition for determining the extremum mode function is satisfied, c is recorded1(t)＝hk(t) as a first extreme modal function component; the determination condition of the extreme value modal function is as follows: (a) in the whole data sequence, the number of the extreme points is equal to or different from the number of the zero-crossing points by one; (b) at any time, the upper envelope line and the lower envelope line are symmetrical relative to a time axis;
(5) Subtracting the first extreme mode function component c from the original signal x (t)1(t) obtaining the residue r1(t)＝x(t)-c1(t) adding r1(t) as a new original sequence x (t), returning to the steps (3) and (4) to obtain 2 nd, 3 rd, … th and 8 th extreme value modal function components and a margin r8(t) the original signal x (t) is then decomposed into 8 extreme modal function components and a residual, i.e.
(6) Opposite polar mode function component ci(t)，iperforming spectrum analysis to obtain the central frequency of each extreme value modal function component and obtaining a frequency domain analysis result graph, wherein the energy of the healthy person is distributed in the range of 0-40 Hz as shown in FIG. 9, the energy proportion of a high-frequency part above 20Hz is high, CHF energy is mainly concentrated below 20Hz as shown in FIG. 10, and the energy of the high-frequency part is obviously reduced;
(7) 8 extreme value modal function components obtained by decomposing the original signal x (t) represent components of different frequency bands of the original signal, and then the energy of each component is calculated
Ei＝∫|ci(t)|2dt，i＝1，2，…，8
normalizing each energy value to obtain a normalized energy distribution vector
pi＝Ei/E，i＝1，2，…，8
Wherein the content of the first and second substances,First component p1Representing the energy of the highest frequency band, representing the proportion of the energy distribution of the signal in the highest frequency band, the last component pnRepresenting the proportion of the energy distribution of the signal in the lowest frequency band range; drawing a normalized energy distribution map according to the normalized energy distribution vectors of healthy people and CHF patients, wherein the abscissa represents the component level, the ordinate represents the normalized energy distribution vector value, the curve represents the average value, and the error bar represents the standard deviation;
As shown in fig. 8, at level 1, the healthy person is higher in energy than the CHF patient, and as the levels increase, the healthy person is gradually reduced in energy; CHF patients gradually increase in levels 1-3 and reach the highest value in level 3; when the level is greater than 3, the energy is gradually reduced along with the increase of the level; the energy of the healthy people is mainly concentrated on levels 1-4, namely in a high frequency range, which shows that the heart of the healthy people has stronger short-time regulating capability; the relatively low-level energy of a CHF patient indicates a reduced short-term accommodation capacity, while the main power is concentrated at the intermediate level, at level 6, which reflects the heart rhythm, and the higher level, which indicates that the CHF patient has a higher energy proportion for the accommodation of the heart rhythm.
(8) Normalized energy distribution vector p for ECG signals of a CHF patientiNormalized energy distribution vector p of ECG signal of healthy personiCarrying out significance detection to obtain a probability value P on each extreme value modal function componentiwhen probability value PiLess than 0.05 indicates a significant difference between the two, as shown in table 2, at levels 1, 2, 3, 5, 6, and a decrease in energy at the decomposition low level in CHF patients may indicate a decrease in the ability of the heart to modulate on the hourly scale due to the disease; the energy of healthy people is higher at the decomposition low level, which shows that the heart of healthy people has better short-time regulation capability and better adaptability to the change of external environment and body environment;
TABLE 2 energy vector T test for healthy and CHF patients
(9) In the presence of a catalyst satisfying P1And P2Less than 0.05, the energy distribution vector p of the first extreme modal function component of the CHF patient1energy distribution vector p smaller than second extreme modal function component2。
Claims (6)
1. An electrocardiogram signal analysis method based on an extreme value energy decomposition method is characterized by comprising the following steps:
(1) Acquiring an ECG signal x (t) of an unknown state at a given time and a given sampling frequency;
(2) Carrying out denoising pretreatment on the ECG signal x (t); the specific method of pretreatment is as follows: filtering the ECG signal by a 40Hz zero-phase FIR low-pass filter to eliminate high-frequency noise, and then removing baseline drift by a median filter;
(3) Taking the denoised ECG signal x (t) as an original signal, solving all local extreme points of the original signal, and then connecting all the extreme points and all the minimum points of the original signal by adopting a spline curve to form a shape respectivelyBecomes an upper envelope emaxAnd a lower envelope eminObtaining the envelope mean value signal m (t) ═ e of the upper envelope line and the lower envelope linemax+emin)/2；
(4) Subtracting the envelope mean value signal m (t) from the original signal x (t) to obtain h (t) ═ x (t) -m (t); then judging whether h (t) meets the judgment condition of the extreme value modal function, if not, returning h (t) to the step (3) as an original signal until hk(t) if the condition for determining the extremum mode function is satisfied, c is recorded1(t)＝hk(t) as a first extreme modal function component;
(5) Subtracting the first extreme mode function component c from the original signal x (t)1(t) obtaining the residue r1(t)＝x(t)-c1(t) then judging hk(t) whether a stopping criterion is met, and if not, r1(t) as a new original sequence x (t), returning to steps (3) and (4) until hk(t) satisfying the stopping criterion, obtaining the 2 nd, 3 rd, … th, n extreme value modal function components and the margin rn(t) the original signal x (t) is then decomposed into n extreme modal function components and a residual, i.e.
(6) Opposite polar mode function component ci(t), i is 1, 2, …, n, and the center frequency of each extreme modal function component is obtained by performing spectrum analysis;
(7) N extreme value modal function components obtained by decomposing the original signal x (t) represent components of different frequency bands of the original signal, and then the energy of each component is calculated
Ei＝∫|ci(t)|2dt，i＝1，2，…，n
Normalizing each energy value to obtain a normalized energy distribution vector
pi＝Ei/E，i＝1，2，...，n
Wherein the content of the first and second substances,First component p1Representing the energy of the highest frequency band, representing the proportion of the energy distribution of the signal in the highest frequency band, the last component pnrepresenting the proportion of the energy distribution of the signal in the lowest frequency band range; drawing a normalized energy distribution graph according to the normalized energy distribution vector, wherein the abscissa represents component levels, the ordinate represents normalized energy distribution vector values, the curve represents an average value, and the error bar represents a standard deviation;
(8) Normalized energy distribution vector p of ECG signal of unknown stateiNormalized energy distribution vector p with standard ECG signaliCarrying out significance detection to obtain a probability value P on each extreme value modal function componentidetermining a probability value P of the first extreme mode function component1And a probability value P on the second extremum mode function component2If the signal is smaller than the probability standard value, returning to the step (1) to acquire the signal again;
(9) In the presence of a catalyst satisfying P1And P2If the energy distribution vector p of the first extreme mode function component is smaller than the standard value of the probability1energy distribution vector p smaller than second extreme modal function component2Then the ECG signal is determined to be an abnormal ECG signal.
2. an electrocardiogram signal analysis method based on the extreme energy decomposition method according to claim 1, characterized in that: the minimum data amount N of the original signal x (t) is 2n+1And n is the number of the decomposed extreme mode function components.
3. An electrocardiogram signal analysis method based on the extreme energy decomposition method according to claim 1, characterized in that: the determination conditions of the extreme mode function in the step (4) are as follows: (a) in the whole data sequence, the number of the extreme points is equal to or different from the number of the zero-crossing points by one; (b) and the upper and lower envelopes are symmetric with respect to the time axis at any time.
4. An electrocardiogram signal analysis method based on the extreme energy decomposition method according to claim 1, characterized in that: h in the step (5)k(t) the formula for satisfying the stopping criterion is:
epsilon represents a screening threshold, and is taken to be 0.2-0.3.
5. an electrocardiogram signal analysis method based on the extreme energy decomposition method according to claim 1, characterized in that: and (3) the probability standard value in the step (8) and the step (9) is 0.05.
6. An electrocardiogram signal analysis method based on the extreme energy decomposition method according to claim 1, characterized in that: and (3) the repetition frequency of the 6 th extreme value modal function component waveform obtained in the step (5) is the heart rate of the human body, namely the cardiac cycle.
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