CN111281373A

CN111281373A - Method and device for quantitatively evaluating cardiac function based on electrocardiogram U wave and T wave

Info

Publication number: CN111281373A
Application number: CN202010150423.7A
Authority: CN
Inventors: 不公告发明人
Original assignee: 何乐
Priority date: 2020-03-06
Filing date: 2020-03-06
Publication date: 2020-06-16

Abstract

The invention discloses a method and a device for quantitatively evaluating cardiac function based on electrocardiogram U wave and T wave, which relate to the field of cardiac function evaluation. The method is simple and rapid, easy to operate, low in detection cost, free of any discomfort and side effects of the testee, and capable of being used for screening early-stage heart dysfunction. The heart function assessment device is small in size, convenient to carry and convenient to operate.

Description

Method and device for quantitatively evaluating cardiac function based on electrocardiogram U wave and T wave

Technical Field

The invention relates to the field of cardiac function assessment, in particular to a method and a device for quantitatively assessing cardiac function based on electrocardiogram U waves and T waves.

Background

The clinical diagnostic value of the electrocardiogram U wave is receiving increasing attention. U-wave abnormalities are not only predictive of a variety of heart diseases and hypertension, but may be associated with drug therapy and even affected by tumor size. The major cardiac tissues such as the American Heart Association (AHA) and the heart rhythm association (HRS) recommend that all U-wave abnormalities be reported when interpreting the ECG.

Although the U-wave was discovered over 100 years ago, its mechanism of action is still unclear. This situation is unfortunate in view of the rapid development of electrophysiology and body surface potential maps. There are a number of hypotheses about the mechanism of forming the U-wave: repolarization of Purkinje fibers (Purkinje fibers) was an early theory, but the small mass of the fibers and the abnormal morphology of the U-wave did not match the known repolarization patterns. Theory of delayed polarization of papillary muscles. The third theory is that the U-wave represents a long-term repolarization of M-cells. However, M cells are more likely to be involved in QT prolongation, forming the T2 wave after T. Another similar theory holds that the U-wave is a continuation of the entire ventricular repolarization and is in one continuum with the T-wave. While the most popular theory at present holds that: the U-wave is related to the physical forces in the ventricular wall. The theory holds that the difference in myocardial fiber relaxation between the endocardium and the epicardium during aortic valve diastole triggers the delayed potential, which generates the U-wave. However, it is considered that the repolarization delay caused by the deformation difference between different regions of the heart is not enough to explain the generation of U wave and related phenomena. These "mysterious" phenomena include: the amplitude of the U wave is inversely proportional to the heart rate; the amplitude of U wave of a patient with enlarged left ventricle or hypertrophic cardiomyopathy is higher; taking Digitalis purpurea and other medicines can increase U wave; severe anemia, hypothermic conditions, forced inspiration, and after exercise, even lifting the thigh while supine, can temporarily increase the U-wave; if the average U wave amplitude is used for comparison, the male is higher than the female, the young is higher than the old and the infant, the athlete is higher than the regular person, the thin person is higher than the fat person, and the low heart rate is higher than the high heart rate. Furthermore, normal U-waves have a fast rising and slower falling slope, just as opposed to the shape of normal T-waves, which is also confusing.

Studies have shown that changes in body position and chest may cause changes in the ECG waveform. Adams et al found that the lateral position often caused significant ECG changes. Shinar et al found that the R-wave durations were significantly different in the three lying positions. Batchvarov et al found that the RR intervals of electrocardiograms were significantly shorter when standing than when lying supine. Smit et al studied the changes in the QRS wave of the electrocardiogram after normal expiration, maximal inspiration and maximal expiration. The conclusion is that the three respiratory conditions have little effect on the QRS complex, but differ by greater than or equal to 1mm in the S-wave of the V4 lead and the R-wave of the V5 lead. Hongze Pan et al found that prone position had less effect on the ECG timing characteristics. QT and RR intervals are lower on the left than on the back. But the height of P wave and T wave, the area of QRS wave and T wave, and the QR potential difference are all obviously lower than those in the supine position, and the S/R is obviously higher than those in the supine position and the right-side position. The T wave height and the T wave area are significantly higher in supine position than in right decubitus position. None of the above studies relate to the U-wave nor give a reason for ECG waveform changes.

Clinically, physicians typically assess the size, function and symptoms of Left Ventricular Hypertrophy (LVH) by palpating the Apical Beat (AB). This approach is a highly subjective, non-quantitative approach and clinical significance is uncertain. Studies have shown that the distance from the heart to the inner wall of the chest cavity is inversely related to the estimated heart size or the amplitude of the apical pulsation. Patients with insignificant apical pulsation have smaller left ventricles or a larger distance from the inner wall of the chest. Another study showed that the distance from the heart to the chest surface affects the amplitude of the recorded precordial voltage. None of these studies have demonstrated the reason for such effects.

It is well known that the use of ECG does not allow reliable assessment of the pumping capacity of the heart, which is usually done by echocardiography or nuclear medicine, but the changes observed by these measures occur only when the disease has progressed to a certain stage or even later, and therefore the diagnosis of early cardiac function is not good. The six minute walk test method (6MWT) was developed by the american thoracic society and was formally introduced in 2002 for the classification of cardiac function in the elderly population. The method is simple and easy to implement, has better repeatability and safety, is easy to be accepted by patients, and is widely applied to the evaluation research of exercise tolerance, cardiac function, pulmonary function and the curative effect and prognosis of chronic heart failure. Ambulation distance <150m in 6 minutes is severe heart failure, 150-450m is moderate heart failure, and >450m is mild heart failure. However, 6MWT does not provide a high degree of discrimination between milder heart failure patients and patients with severe symptoms are not able to bear the risk of the test. Therefore, finding a simple, convenient, rapid and operation risk-free heart function assessment method is certainly of great clinical significance.

Disclosure of Invention

The invention aims to provide a method and a device for quantitatively evaluating heart functions based on electrocardiogram U waves and T waves, so as to solve the technical problems.

In order to solve the technical problem, the invention provides a method for quantitatively evaluating the cardiac function based on electrocardiogram U waves and T waves, which comprises the following steps:

the method comprises the following steps of firstly, recruiting enough volunteers of different ages and different sexes in advance, attaching electrocardiogram electrode plates to the chest and the four limbs of the volunteer, starting an electrocardiograph, an electrocardiosignal processor and a computer, and setting electrocardiograph parameters;

measuring and recording an electrocardiogram of each volunteer when the heart apex pulsation state is unchanged, and recording a U wave amplitude and a T wave amplitude on the electrocardiogram;

changing the heart apex pulsation state of the volunteer, and recording the amplitude of the U wave and the amplitude of the T wave on the electrocardiogram again;

step four, calculating the numerical value of the combined parameter of each volunteer after the U wave amplitude value and the T wave amplitude value are changed;

step five, each volunteer is subjected to echocardiography examination, CT examination or six-minute walk test;

step six, taking the numerical value of the combined parameter of the U wave amplitude and the T wave amplitude of the volunteers with normal echocardiogram or CT examination and/or walking distance of more than a certain distance in six minutes as the parameter value under the heart health state, and arranging the parameter values under the heart health state according to the magnitude sequence to obtain a normal parameter value range under the heart health state;

step seven, enabling any volunteer to receive the detection from the step one to the step four, obtaining a combined parameter value of the U wave amplitude and the T wave amplitude of the volunteer, comparing the value with the normal parameter value range in the heart health state in the step six, if the value is lower than the lower limit of the range, indicating that the heart contraction function of the volunteer is in problem, and the farther the value is away from the lower limit, the weaker the heart muscle contraction force is;

conversely, if the volunteer's combined parameter value is higher than the lower limit, there are two possibilities: firstly, the myocardium of the volunteer is normal in function, and the farther the numerical value is from the lower limit value, the stronger the heart contractility is; secondly, the heart size of the volunteer exceeds the normal range, and the heart is bigger the farther the numerical value is from the lower limit value; another conclusion can be reached as long as one can be excluded.

Preferably, the U-wave amplitude and T-wave amplitude combination parameter includes: (U)_l/T_l-U_s/T_s)、(U_l/T_l-U_s/T_s)/(U_s/T_s)、(U_l/T_l-U_s/T_s)/(U_l/T_l)、(U_l/T_l-U_s/T_s)/(U_s/T_s)-a(b-BMI)、(U_l/T_l-U_s/T_s)/(U_l/T_l)-a(b-BMI)、(U_p/T_p-U₀/T₀)、(U_p/T_p-U₀/T₀)/(U₀/T₀)、(U_p/T_p-U₀/T₀)/(U_p/T_p)、(U_p/T_p-U₀/T₀)/(U₀/T₀)-a(b-BMI)、(U_p/T_p-U₀/T₀)/(U_p/T_p)-a(b-BMI)；

Wherein, U_lRepresenting the amplitude, T, of the U wave on the left lateral decubitus electrocardiogram_lRepresenting the amplitude, U, of the T wave on the left lateral decubitus electrocardiogram_sRepresenting the amplitude, T, of the U-wave on the electrocardiogram in the supine position_sRepresenting the T wave amplitude value on the electrocardiogram in the supine position; a (b-BMI) represents a parameter term including a body mass index, wherein a and b are proportionality coefficients, and BMI is weight/height²；U_pShowing the amplitude of U wave on electrocardiogram T when the inflation pressure of the chest-bound air bag is P_pShowing the T wave amplitude, U, on the electrocardiogram with the inflation pressure of the chest-bound air bag being P₀Showing the amplitude of U-wave on electrocardiogram, T, when the inflation pressure of the chest-binding air bag is 0₀Showing the T wave amplitude on the electrocardiogram when the inflation pressure of the chest-binding air bag is 0.

Preferably, the change mode of the state of the three-step apical pulsation is to change the posture of the volunteer during electrocardiogram measurement.

Preferably, the change of the state of the three-step apical pulsation is realized by changing the distance between the apex of the heart and the chest wall of the volunteer.

Preferably, the distance between the apex of the heart and the chest wall of the volunteer is changed by wearing an air bag wrapping the chest wall of the volunteer and changing the inflation amount or inflation pressure of the air bag by inflating the air bag so as to change the distance between the apex of the heart and the chest wall.

Preferably, the changing of the distance between the apex of the heart and the chest wall of the volunteer is realized by pressing the left chest of the volunteer with hands or objects.

Preferably, the changing of the distance between the apex of the heart and the chest wall of the volunteer is to keep the volunteer in a supine position and to lift the left leg to press the left chest.

In addition, the invention also provides a device for quantitatively evaluating the heart function based on the electrocardiogram U wave and T wave, which comprises:

the air bag is inflated into the air bag, so that the inflation quantity or inflation pressure of the air bag is changed, the distance between the apex of the heart and the chest wall of the volunteer is changed, and the apex beating state of the heart of the volunteer is changed;

the electrocardiograph is used for acquiring electrocardio analog signals of a volunteer in different cardiac apex beating states and sending the electrocardio analog signals to the electrocardio signal processor;

the electrocardiosignal processor receives electrocardio analog signals from the electrocardiograph, converts the electrocardio analog signals into digital signals, screens out chest lead signals from the digital signals, screens out U-wave signals and T-wave signals from the chest lead signals, measures and records the amplitude of the U-wave signals and the T-wave signals, and sends the obtained data to the computer;

the computer analyzes the data from the electrocardiosignal processor and displays the detection result;

and the control unit controls the inflation quantity and the inflation pressure of the air bag.

Preferably, a drift filter and an alternating current filter are further arranged between the electrocardiograph and the electrocardiosignal processor.

Preferably, the electrocardiograph is not lower than 12-lead electrocardiograph.

Compared with the prior art, the invention has the characteristics and beneficial effects that:

(1) the heart function is evaluated by changing the heart apex pulsation state, measuring the U wave amplitude and the T wave amplitude of the electrocardiogram under different heart apex pulsation states and comparing the difference value of the combined parameters of the U wave amplitude and the T wave amplitude with the normal value under the health state. The method is simple and rapid, easy to operate, low in detection cost, free of any discomfort and side effects of the testee, and capable of being used for screening early-stage heart dysfunction.

(2) The invention provides a cardiac function assessment device which is small in size, convenient to carry and convenient to operate.

Drawings

FIG. 1 is a schematic diagram of the amplitude of the U wave, the amplitude of the T wave, and the time interval J between the two peaks in the supine position.

U in Table 2 of FIG. 2_s/T_sAnd U_l/T_lA scatter plot of the relationships between.

FIG. 3 is U in Table 2₅₀/T₅₀And U₀/T₀A scatter plot of the relationships between.

FIG. 4 is a drawing showing (U) in Table 3_l/T_l-U_s/T_s)/(U_l/T_l) -scatterplot of the relationship between 0.001(24-BMI) and 1000 meters running time.

FIG. 5 is a drawing showing (U) in Table 3₅₀/T₅₀-U₀/T₀)/(U₅₀/T₅₀) And a relation scatter diagram between 1000 meters running time.

Detailed Description

In order to make the technical means, innovative features, objectives and functions realized by the present invention easy to understand, the present invention is further described below.

The examples described herein are specific embodiments of the present invention, are intended to be illustrative and exemplary in nature, and are not to be construed as limiting the scope of the invention. In addition to the embodiments described herein, those skilled in the art will be able to employ other technical solutions which are obvious based on the disclosure of the claims and the specification of the present application, and these technical solutions include technical solutions which make any obvious replacement or modification for the embodiments described herein.

1. New U wave theory

The present invention considers that apical pulsation eventually leads to generation of an electrocardiogram U-wave based on the following facts:

(1) temporally, the U-wave occurs at the end or pre-diastole phase of the heart, just in the time frame of the apex striking the chest wall, which occurs with the second (S2) heart sound.

(2) Spatially, the U-wave is most pronounced in the V3 lead, where the U-vector points to the left and front, just where the apex strikes the chest wall.

(3) The distance from the heart to the chest surface affects the amplitude of the electrocardiographic voltage, while the distance from the heart to the inner wall of the chest cavity is inversely related to the amplitude of the apical pulsation.

(4) In the left lateral decubitus position, the apex of the heart beats more acutely than in the supine position, and the heart is closer to the chest wall in the left lateral decubitus position.

(5) Computer modeling of the left ventricular repolarization showed that if there is a delayed potential on the cardiac action potential, the U-wave polarity and other U-wave features can be interpreted.

(6) Changes in posture and chest cavity can cause changes in the ECG waveform. The amplitude of the T wave is higher in the supine position than in the left or right decubitus position.

The theoretical key points of electrocardiogram U wave and T wave change caused by apical pulsation are as follows:

(1) because of the beating of the apex, some of the left ventricular cardiomyocytes (including the adventitial and intimal cells) are subjected to a counter-impact force from the chest wall, which is related to the myocardial contractility, the heart mass, the distance between the apex and the intrathoracic wall, and the heart structure and condition, regardless of the thickness and shape of the extrathoracic fat layer.

(2) When the pressure strain and the pressure strain rate of the myocardial cells exceed certain threshold values, the repolarization process is affected and delayed. The greater the compressive strain and rate of compressive strain experienced, the longer the repolarization time.

(3) Because of the heart apex pulsation, part of the left ventricular cardiomyocytes will be subjected to a compressive strain and a compressive strain rate exceeding a threshold value, and the repolarization of the part of the cells is delayed, so that the overall repolarization of the left ventricle is divided into two stages: repolarization of cells that are less or not affected by apical pulsation and repolarization of cells that are more affected by apical pulsation. The former forms the T wave of electrocardiogram, and the latter forms the U wave.

(4) The number of cells in the two repolarization stages and the mean of these cell strains and strain rates are positively correlated with the T-wave area and the U-wave area. Under the condition that the waveform is basically unchanged, the T wave amplitude and the U wave amplitude are approximately in positive correlation. The time difference between the two repolarization phases can be roughly represented by the time difference between two peak points on the electrocardiogram.

(5) In healthy conditions, the more intense the apical pulsation, the greater the proportion of cardiomyocytes affected and the strain and strain rates of these cells, and the lesser and unaffected proportion of cardiac cells and the strain and strain rates of these cells. Therefore, the higher the amplitude of the U wave, the lower the amplitude of the T wave, and the larger the time difference between the two peaks. And because the current flow is the same, both waves have the same positive polarity.

(6) Under abnormal conditions such as myocardial cell ischemia, if cells at an ischemic part are affected by apical pulsation, the degree of ischemia is more serious, the repolarization delay is also more serious, and the abnormal conditions that the repolarization cannot be realized, and even part of repolarized cells depolarize again, so that U waves disappear or are inverted are caused.

(7) If pathological factors (myocarditis, pericarditis, myocardial infarction, pleural effusion, pneumothorax, pleural adhesion and the like) and non-pathological factors (movement, cardiac apex displacement caused by the fact that the diaphragm is lifted up or down and the like) are eliminated, the change of the amplitude of the U wave is related to three main factors, namely heart mass (or size) M, the distance S between the heart and the inner wall of the chest and heart contractility P, and the specific expression is as follows:

a. if S and P are not changed, the larger M is, the larger the momentum change (impulse) when the cardiac apex impacts the chest wall is, the larger the compressive strain and the compressive strain rate generated by the cardiac apex are, the larger the number of the affected myocardial cells is, and the higher the U wave amplitude is.

b. If M and S are constant, the greater P, the greater the acceleration of the heart contraction and the velocity at which the apex contacts the chest wall, the greater the change in momentum upon impact with the chest wall, the more intense the apex beating, and the greater the strain and strain rate experienced by the apex. The higher the U-wave amplitude.

c. If M and P are unchanged, the smaller S is, the longer the apical impulse occurs, the longer the apical impulse contacts with the chest wall, the more cardiomyocytes are squeezed and deformed by the chest wall, the larger the strain and strain rate is, and the higher the U-wave amplitude is.

2. Changing the way of U-wave and T-wave

The present invention alters the subject's U-wave and T-wave in the following ways, but is not limited to:

(1) changing body position

Conventional electrocardiographic measurements typically allow the subject to adopt a supine position (and sometimes a sitting position). When the testee lies on the back, the distance between the apex of the heart and the chest wall is larger due to the action of gravity, the contact area between the apex of the heart and the chest wall is reduced after the apex of the heart is twisted, and the impact strength is weakened due to the reverse drawing action of gravity. According to the above theory, the amount of cardiomyocytes that are deformed by the chest wall reaction is small, the strain rate is low, and the amplitude of the measured U-wave on the electrocardiogram is low. If left lateral recumbent measurements are used, the distance between the heart on the left side and the left chest wall will be shortened due to gravity. The contact area between the apex of the heart and the chest wall is larger when the apex of the heart is twisted, the impact force is enhanced due to the action of gravity, the number of the myocardial cells which are deformed due to the reaction of the chest wall is larger, the strain rate is also larger, the amplitude of U wave on the electrocardiogram is higher than that of the U wave when the user lies on the back, the T wave is lower than that of the U wave when the user lies on the back, and the time difference between the peak values of the two waves. The phenomenon is well documented: experienced physicians know that apex beating can be particularly intense when left recumbent, even without touching the chest wall surface. But cannot be seen if turned into the supine position, and is difficult to feel even by hand.

(2) Squeezing thoracic cavity

The chest cavity, supported by ribs, can change shape under external forces. The present invention employs an inflatable band to tightly wrap around the thorax. Once the air bag begins to inflate, the ribs are forced inwardly by even pressure, forcing the rib cage to contract. The distance between the thoracic cavity and the heart is reduced due to the contraction of the thoracic cavity, the torsion motion of the apex is prevented by the closer chest wall to generate larger deformation, the number of left ventricle myocardial cells with repolarization affected by the deformation is more, and U waves and T waves can be changed according to the U-wave apex beating theory. In addition, the left chest of the subject can be pressed by hands or objects, or the subject can keep the supine position and lift the left leg to press the left chest, and the effect of shortening the distance between the apex of the heart and the chest wall can also be achieved.

3. Measuring parameters

(1) U-wave amplitude (in 0.1mv) for each lead: by U_l，U_s，U₀And U_pRespectively representing the amplitude of the air bag when the pressure is 0 and the pressure is P in the left lateral lying position, the back lying position and the sitting and standing position. When the U-wave amplitude is measured, the lowest point between the U-wave and the T-wave is used as a base point (as shown in fig. 1).

(2) T-wave amplitude (in 0.1mv) for each lead: by T_l，T_s，T₀And T_pRespectively representing the amplitude of the air bag when the pressure is 0 and the pressure is P in the left lateral lying position, the back lying position and the sitting and standing position. When measuring the amplitude of the T wave, the lowest point between the U wave and the T wave is used as a base point (as shown in fig. 1).

4. Measuring device

(1) Electrocardiogram instrument

The present invention measures the electrocardiogram of a subject by a conventional method using a multi-lead (e.g., 12-lead) high-quality electrocardiograph.

(2) Electrocardiosignal processor

The invention sends the electrocardiogram analog signals obtained by the electrocardiogram instrument into a processor for amplifying and filtering noise and then converting the signals into digital signals, screens out chest lead (V1-V6) signals from all lead signals, screens out U wave signals from the signals and measures and records the amplitude of the U wave signals. The measured U-wave amplitudes under the different conditions were compared and the difference between them was recorded. In addition, the electrocardiosignal processor can also record the heart rate of the volunteer and automatically calculate the heart rate mean value in each electrocardiogram measuring period. The obtained data is input into a computer through a lead for heart work analysis and result display.

(3) Computer and APP

The invention adopts APP software which can automatically analyze the heart function according to the output parameters of the electrocardiosignal processor, and the detection result is analyzed and displayed in a computer.

(4) Air bag

The present invention uses controllable inflatable air bags of different sizes. The air bag can be wrapped around the chest of the volunteer and the length of the air bag can be fixed in the non-inflated state by adopting various conventional methods, such as pinching the two ends of the air bag together by using nylon buckles and the like. After the air bag is inflated, the volume of the air bag is gradually increased, and the inflated air bag enables the thoracic cavity to be gradually contracted under circumferential pressure due to the fixed length of the air bag, so that the aim of reducing the distance between the apex of the heart and the chest wall of the testee is fulfilled.

(5) Control unit

Controlling the inflation volume and inflation pressure of the air bag.

5. Example of the implementation

The volunteers were allowed to rest sufficiently, and then electrocardiograms of the volunteers in the supine and left lateral positions were measured using a standard 12-lead electrocardiograph. Finally, the volunteer takes a sitting posture, and after the electrocardiogram electrode plate is attached, an air bag which can be inflated and pressurized is wrapped around the whole chest outside the electrode plate. The air bag does not affect the shape of the thorax when not inflated. After inflation, the chest cavity will be compressed and become smaller. Electrocardiograms were measured both without and with inflation and pressurization to 50 kPa. The main disturbances of the electrocardiogram waveform result from the baseline wander caused by the coupling of the electro-muscular activity at a frequency of 2Hz-2kHz and the breathing of the volunteers. To eliminate interference, we let volunteers rest fully before measurement, try to relax during measurement and hold their breath for a short time while the instrument collects data. In addition, other interference in the ECG signal is eliminated using a drift filter and an AC filter. Because the amplitude of the U wave is small, the added value is smaller, and the obtained electrocardiogram can be amplified by a plurality of times and then measured by a caliper. The parameters of the electrocardiograph were set as follows: scanning speed 25mm/s, sensitivity 20mm/mv, ECG sampling frequency 200 Hz.

The measurement steps are as follows:

In the present invention, 41 experimental volunteers were recruited(35 men, 6 women), all healthy in high school students, aged from 15 to 18 years. The height (cm) and weight (kg) of the volunteer were first measured, and then the elapsed time(s) of the distance (1000 m in male, 800m in female) run in the volunteer was measured with a stopwatch. There were 2 volunteers who did not participate in the chest compression test for personal reasons. Table 1 shows the range of mean values with 99% confidence for the parameter combinations of the V3 lead portion, J_lRepresenting the difference in time between the peaks of the U and T waves in the lateral decubitus of the volunteer, J_sRepresenting the difference between the peaks of the U and T waves in the supine position of the volunteer, Ave (J)_l-J_s) Then represents two postures J of 41 volunteers_lAnd J_sThe average of the differences. J. the design is a square₅₀The difference between the peaks of the U-wave and the T-wave at an airbag pressure of 50kPa, J₀The time difference between the peaks of the U-wave and the T-wave at an air bag pressure of 0, Ave (J)₅₀-J₀) Then represents 41 volunteers under two air bag pressures J₅₀And J₀The mean value of the difference, the meaning of the other parameters and so on.

TABLE 1 test results under different apical pulsation conditions

Difference of parameters	Amplitude (0.1mv)	Time difference (40ms)
			Ave(U_l–U_s)	0.244±0.095	-
Ave(T_l–T_s)	-1.303±0.740	-
			Ave(J_l–J_s)	-	0.377±0.120
Ave(U₅₀–U₀)	0.113±0.069	-
			Ave(T₅₀–T₀)	-0.72±0.600	-
Ave(J₅₀–J₀)	-	0.268±0.260

The U wave amplitude, T wave amplitude and time difference between two peaks of the V3 lead are clearly related to the posture. Changing body positions can cause them to change. The inflation pressure of the airbag in the sitting position also causes a change in the parameters. In order to find out the relationship between the parameter combinations in different body positions and air bag pressures, the measurement parameters of each volunteer are adopted to calculate the correlation coefficient r, and the calculation result is shown in table 2.

TABLE 2 correlation coefficient between parameter combinations in different apical pulsation states

Parameter one	Parameter two	Coefficient of correlation r
			U_l-U_s	T_l-T_s	0.124
U_l/T_l	U_s/T_s	0.871
			U_l/T_l-U_s/T_s	J_l-J_s	0.358
U_l/U_s	T_l/T_s	-0.173
			U_s/T_s	U₀/T₀	0.591
U₅₀/T₅₀	U₀/T₀	0.959

Fig. 2 and 3 are graphs showing scattergrams of the relationship between two sets of parameters with higher correlation in table 2. It can be seen from fig. 2 and fig. 3 that these points are concentrated on a straight line, which indicates that the correlation between the parameters is strong.

In order to find the relationship between different parameter combinations and cardiac function, the present invention uses the elapsed time of 1000m (or 800m) run to characterize the degree of cardiac health. In the case of best effort, the shorter the time, the stronger the systolic function. The time spent in 1000m of 41 volunteers was very different (from 2 min 50 s to 5 min 05 s). Table 3 shows the correlation coefficient between different parameter combinations and running time of 1000 meters.

TABLE 3 different parameter combinations and running time t of 1000m_1kCoefficient of correlation between

Parameter combination	Coefficient of correlation r
		U_s	0.161
U_l–U_s	-0.271
		T_l-T_s	0.20
U_l/T_l-U_s/T_s	-0.515
		(U_l/T_l-U_s/T_s)/(U_l/T_l)	-0.786
[(U_l/T_l-U_s/T_s)/(U_l/T_l)]-0.001*(24-BMI)	-0.787
		U₅₀-U₀	-0.384
U₅₀/T₅₀-U₀/T₀	-0.395
		(U₅₀/T₅₀–U₀/T₀)/(U₅₀/T₅₀)	-0.688

Fig. 4 and 5 are graphs showing the relationship between two sets of parameters with high correlation and running time of 1000 meters in table 3. It can be seen from fig. 4 and 5 that these points are concentrated on a straight line, which indicates that the correlation between the parameters is strong.

According to the preceding measurement procedure, the following combinations of parameters are measured and calculated for the assessment of myocardial function:

(1) the difference between the ratio of the U wave to the T wave on the left lateral and supine electrocardiograms, i.e. (U)_l/T_l-Us/Ts)；

(2) Dividing the difference between the ratio of the U wave and the T wave of the left lateral and supine electrocardiograms by the ratio of the U wave to the T wave of the supine electrocardiograms to obtain (U wave and T wave ratio)_l/T_l-Us/Ts)/(Us/Ts)；

(3) Dividing the difference between the ratio of the U wave and the T wave of the left lateral position electrocardiogram by the ratio of the U wave to the T wave of the left lateral position electrocardiogram, i.e. (U wave ratio)_l/T_l-Us/Ts)/(U_l/T_l)；

(4) Dividing the difference of the ratio of the U wave and the T wave on the electrocardiogram of the left lateral decubitus and the electrocardiogram of the supine decubitus by the ratio of the U wave and the T wave of the electrocardiogram of the supine decubitus, and then subtracting the BMI parameter item: a (b-BMI), i.e. (U)_l/T_l-Us/Ts)/(Us/Ts)-a(b-BMI)；

(5) Dividing the difference of the ratio of the U wave and the T wave on the electrocardiogram of the left lateral recumbent position and the electrocardiogram of the supine position by the ratio of the U wave and the T wave of the electrocardiogram of the left lateral recumbent position, and then subtracting a BMI parameter item: a (b-BMI), i.e. (U)_l/T_l-Us/Ts)/(U_l/T_l)-a(b-BMI)；

(6) The difference between the ratio of the U wave to the T wave on the electrocardiogram with the inflation pressure of the chest-binding air bag being P and the inflation pressure being 0, i.e. (U wave)_p/T_p-U₀/T₀)；

(7) The difference between the ratio of the U wave and the T wave on the electrocardiogram with the inflation pressure of P and the inflation pressure of 0 is divided by the ratio of the U wave and the T wave on the electrocardiogram with the inflation pressure of 0, namely (U wave and T wave)_p/T_p-U₀/T₀)/(U₀/T₀)；

(8) The difference between the ratio of the U wave and the T wave on the electrocardiogram with the inflation pressure of P and the inflation pressure of 0 of the chest restraint air bag is divided by the ratio of the U wave and the T wave of the electrocardiogram with the inflation pressure of P, namely (U wave and T wave)_p/T_p-U₀/T₀)/(U_p/T_p)；

(9) The difference between the ratio of the U wave and the T wave on the electrocardiogram with the inflation pressure of P and the inflation pressure of 0 is divided by the ratio of the U wave and the T wave of the electrocardiogram with the inflation pressure of 0, and then the BMI parameter item is subtracted: a (b-BMI), i.e. (U)_p/T_p-U₀/T₀)/(U₀/T₀)-a(b-BMI)；

(10) The difference between the ratio of the U wave and the T wave on the electrocardiogram with the inflation pressure of K and the inflation pressure of 0 is divided by the ratio of the U wave and the T wave of the electrocardiogram with the inflation pressure of P, and then the BMI parameter item is subtracted: a (b-BMI), i.e. (U)_p/T_p-U₀/T₀)/(U_p/T_p)-a(b-BMI)。

Comparing the magnitude of the above-mentioned combined U-wave and T-wave amplitude parameter of the subject with the value of the healthy heart parameter, thereby evaluating the systolic function or the heart size. The range of normal values of the healthy heart described here can be determined by a large number of medical clinical trials, according to the experiments of the authors, for healthy adolescents (14-18 years) and for the combination of parameters (U)_l/T_l-Us/Ts)/(U_l/T_l) A value of-0.001 (24-BMI), healthy heart should not be lower than 0.03, and robust heart can reach 0.8 or even higher. For parameter combination (U)₅₀/T₅₀-U₀/T₀)/(U₅₀/T₅₀) Healthy hearts should not be less than-0.2, stronger hearts may reach 0.4 or even higher. The normal ranges for the remaining parameter combinations also need to be determined on the basis of a large number of clinical trials.

The method for quantitatively evaluating the cardiac function provided by the invention has no side effect, no discomfort of a subject, simple operation and short detection time. The method has low detection cost and easy acceptance, and can be used for screening early cardiac dysfunction.

The above examples are only for describing the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for quantitatively evaluating cardiac function based on electrocardiogram U waves and T waves is characterized by comprising the following steps:

2. The method according to claim 1, wherein the parameters of the combination of the U-wave amplitude and the T-wave amplitude comprise: (U)_l/T_l-U_s/T_s)、(U_l/T_l-U_s/T_s)/ (U_s/T_s)、(U_l/T_l-U_s/T_s)/ (U_l/T_l)、(U_l/T_l-U_s/T_s)/ (U_s/T_s)- a(b-BMI)、(U_l/T_l-U_s/T_s)/ (U_l/T_l) - a(b-BMI)、(U_p/T_p-U₀/T₀)、(U_p/T_p-U₀/T₀)/ (U₀/T₀)、(U_p/T_p-U₀/T₀)/ (U_p/T_p)、(U_p/T_p-U₀/T₀)/(U₀/T₀)-a(b-BMI)、(U_p/T_p-U₀/T₀)/ (U_p/T_p)-a(b-BMI)；

Wherein, U_lRepresenting the amplitude, T, of the U wave on the left lateral decubitus electrocardiogram_lRepresenting the amplitude, U, of the T wave on the left lateral decubitus electrocardiogram_sRepresenting the amplitude, T, of the U-wave on the electrocardiogram in the supine position_sRepresenting the T wave amplitude value on the electrocardiogram in the supine position; a (b-BMI) represents a parameter term including body mass index, wherein a and b are proportionality coefficients, BMI = weight/height²；U_pShowing the amplitude of U wave on electrocardiogram T when the inflation pressure of the chest-bound air bag is P_pShowing the T wave amplitude, U, on the electrocardiogram with the inflation pressure of the chest-bound air bag being P₀Showing the amplitude of U-wave on electrocardiogram, T, when the inflation pressure of the chest-binding air bag is 0₀Showing the T wave amplitude on the electrocardiogram when the inflation pressure of the chest-binding air bag is 0.

3. The method for quantitative assessment of cardiac function based on electrocardiographic U-wave and T-wave according to claim 1, wherein: the change mode of the central apex beating state of the three steps is to change the posture of a volunteer during electrocardiogram measurement.

4. The method for quantitative assessment of cardiac function based on electrocardiographic U-wave and T-wave according to claim 1, wherein: the change mode of the heart point pulsation state in the three steps is to change the distance between the heart point and the chest wall of the volunteer.

5. The method for quantitative assessment of cardiac function based on electrocardiographic U-wave and T-wave according to claim 4, wherein: the change volunteer's distance between apex of the heart and chest wall specifically is let the volunteer dress the air pocket of parcel thorax, through aerifing the air pocket, changes air pocket inflation volume or inflation pressure to change the distance of apex of the heart and chest wall.

6. The method for quantitative assessment of cardiac function based on electrocardiographic U-wave and T-wave according to claim 4, wherein: the step of changing the distance between the apex of the heart and the chest wall of the volunteer is realized by pressing the left chest of the volunteer with hands or objects.

7. The method for quantitative assessment of cardiac function based on electrocardiographic U-wave and T-wave according to claim 4, wherein: the changing of the distance between the apex of the heart and the chest wall of the volunteer is to keep the volunteer in a supine position and lift the left leg to press the left chest.

8. An apparatus for quantitatively evaluating cardiac function based on U-wave and T-wave of electrocardiogram, comprising:

9. The apparatus for quantitative assessment of cardiac function based on electrocardiographic U-wave and T-wave according to claim 8, wherein: a drift filter and an alternating current filter are also arranged between the electrocardiograph and the electrocardiosignal processor.

10. The apparatus for quantitative assessment of cardiac function based on electrocardiographic U-wave and T-wave according to claim 8, wherein: the electrocardiograph is not lower than 12-lead electrocardiograph.