Myocardial infarction border zone tissue identification method

Abstract

A myocardial infarction border zone tissue identification method, comprising: performing a biaxial mechanical tensile test on heart tissue to be identified, a tissue between the stiffness of normal myocardial tissue and the stiffness of myocardial infarction tissue being a first potential border zone; performing double staining and identification on the cardiac tissue to be identified: first using an Evans blue staining solution to perform staining, and then using a 2,3,5-triphenyltetrazolium chloride staining solution to perform staining, and observing the staining results, a red region being a second potential border zone, and an overlapping portion of the first potential border zone and the second potential border zone being a myocardial infarction border zone. The present myocardial infarction border zone tissue identification method performs multi-dimensional identification of a myocardial infarction border zone from both physical and chemical perspectives, so as to ensure the accuracy of an identification result.

Description

A method for identifying the boundary zone of myocardial infarction Technical Field

[0001] This application relates to the field of medical experimental technology, and in particular to a method for identifying tissue in the boundary zone of myocardial infarction. Background Technology

[0002] Within an infarcted heart, three morphologically distinct regions can be identified: the infarct boundary zone, the uninjured distal myocardium, and the infarct zone, characterized by injury and cell death. Myocardial infarction is typically caused by the formation of atherosclerotic plaques leading to coronary artery occlusion. This blockage impedes the flow of blood and oxygen to the affected area of ​​the myocardium, resulting in hypoxia and the death of numerous myocardial cells. A steep oxygen gradient forms at the interface between the injured, hypoxic tissue and the surrounding, surviving, oxygen-rich tissue; this region is known as the infarct boundary zone.

[0003] The boundary region of myocardial infarction is particularly important for the remodeling process following myocardial infarction. Over the following days, weeks, and months, the electrocardiographic properties of the injured myocardium, especially the boundary region of the myocardial infarction, undergo extensive remodeling, potentially leading to heart failure. In vivo and in vitro models have shown that boundary region tissue is a known matrix for arrhythmias and generates less force than distal myocardium. These observations suggest that the boundary region is particularly susceptible to pathophysiological remodeling, possibly due to the heterogeneous cellular microenvironment. Various studies have indicated its involvement in infarct expansion, fibrosis, hypertrophy, and repair, as well as the electrically unstable processes that trigger arrhythmias and sudden cardiac events. The boundary between injured, hypoxic tissue and adjacent, viable, oxygen-rich tissue (the boundary region of myocardial infarction) is characterized by an oxygen gradient.

[0004] However, due to the limitations of existing experimental models, little is known about the impact of the myocardial infarction boundary region on cardiac tissue function. These changes in the myocardial infarction boundary region differ from those observed in tissues exposed to homogeneous normoxic or hypoxic conditions, suggesting different regulatory effects of oxygen gradients on cardiac tissue phenotype. From an anatomical perspective, no clearly defined tissue identification method for the myocardial infarction boundary region has been proposed, and its function remains unclear. Therefore, existing techniques require further improvement. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide a method for identifying tissues in the boundary zone of myocardial infarction, aiming to solve the problem of the lack of such methods in the prior art.

[0006] The technical solution of this application is as follows:

[0007] The first aspect of this application provides a method for identifying tissue at the boundary of a myocardial infarction, comprising the steps of:

[0008] A biaxial mechanical tensile test was performed on the cardiac tissue to be identified: the tissue between the stiffness of normal myocardial tissue and the stiffness of myocardial infarction tissue was designated as the first potential boundary zone; the cardiac tissue to be identified was subjected to double staining identification: first, Evans blue staining solution was used, followed by 2,3,5-triphenyltetrazolium chloride staining solution, and the staining results were observed. The red area was designated as the second potential boundary zone; the overlapping part of the first potential boundary zone and the second potential boundary zone was designated as the myocardial infarction boundary zone.

[0009] Optionally, the steps of the biaxial mechanical tensile test include:

[0010] A heart tissue sample is obtained, a tensile force is applied to the heart tissue sample along a first direction and a second direction, and the stiffness value of the heart tissue sample is measured; the angle between the first direction and the second direction is 90°.

[0011] Optionally, the strain ratio of the tensile force in the first direction to the tensile force in the second direction is at least one of 2:1, 4:3, or 1:1.

[0012] Optionally, the Evans blue staining solution contains 0.5-3% Evans blue dye by mass; and the 2,3,5-triphenyltetrazolium chloride staining solution contains 1-3% 2,3,5-triphenyltetrazolium chloride by mass.

[0013] A second aspect of this application provides a biaxial mechanical tensile testing device, including a base and an X-axis mechanical tensile component, a Y-axis mechanical tensile component, and a sample testing platform disposed on the base. The angle between the extension direction of the X-axis mechanical tensile component and the extension direction of the Y-axis mechanical tensile component is 90°. The X-axis mechanical tensile component includes a first tensile component and a second tensile component arranged symmetrically about the sample testing platform. The Y-axis mechanical tensile component includes a third tensile component and a fourth tensile component arranged symmetrically about the sample testing platform. The first tensile component and the second tensile component... Both the third and fourth stretching components have clamping portions on the side near the sample detection platform. At least one of the clamping portions of the first and second stretching components is movable along the extension direction of the X-axis mechanical stretching component, and at least one of the clamping portions of the third and fourth stretching components is movable along the extension direction of the Y-axis mechanical stretching component. At least one of the first and second stretching components and at least one of the third and fourth stretching components are equipped with a force sensor, and the force sensor is configured to record force values.

[0014] Optionally, the first tensioning assembly, the second tensioning assembly, the third tensioning assembly, and the fourth tensioning assembly each include a displacement driver and a connecting rod, and the displacement driver, the connecting rod, and the clamping part are fixedly connected in sequence.

[0015] Optionally, the base is provided with a water bath, and the X-axis mechanical tensile component, the Y-axis mechanical tensile component, and the sample testing platform are disposed in the water bath.

[0016] A third aspect of this application provides the application of the biaxial mechanical tensile testing device of the second aspect of this application in the identification of tissues in the boundary zone of myocardial infarction.

[0017] A fourth aspect of this application provides a method for identifying the boundary region of myocardial infarction using the biaxial mechanical tensile testing device of the second aspect of this application, comprising: acquiring a cardiac tissue sample; measuring the true thickness of the cardiac tissue sample at nine different locations using a dial gauge; laying the cardiac tissue sample flat on the sample testing platform, removing excess tissue along the edge of the sample testing platform, and fixing the cardiac tissue sample using the clamping part; applying a preload force of 10 mN along the X-axis and Y-axis, then applying biaxial tensile forces along the X-axis and Y-axis respectively with reference to 30% of the strain on the X-axis and a tensile speed of 10 μm / s; performing stress relaxation for 300 s after all loading is completed; recording the force value change using a sensor and recording the relationship curve between the force value change and time.

[0018] Optionally, the biaxial tensile strain ratio is at least one of 2:1, 4:3, or 1:1.

[0019] The beneficial effects of this application are as follows: The method for identifying the boundary zone of myocardial infarction in this application includes biaxial mechanical tensile testing, dual staining identification, and transcriptomics analysis of the cardiac tissue to be identified. By combining mechanical properties, chemical staining, and transcriptomics analysis, the boundary zone of myocardial infarction is identified from both macroscopic and microscopic perspectives to ensure the accuracy of the identification results. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0021] Figure 1 is a schematic diagram of the biaxial mechanical tensile testing device provided in an embodiment of this application;

[0022] Figure 2 is a physical diagram of the biaxial mechanical tensile testing device provided in the embodiment of this application;

[0023] Figure 3 is an ultrasound image of myocardial infarction in mice provided in an embodiment of this application;

[0024] Figure 4 shows a biaxial tensile test diagram provided in an embodiment of this application:

[0025] A is the tensile stress-strain curve along the direction of myocardial fibers; B is the creep stress-relaxation curve along the direction of myocardial fibers; C is the tensile stress-strain curve perpendicular to the direction of myocardial fibers; D is the creep stress-relaxation curve perpendicular to the direction of myocardial fibers.

[0026] Figure 5 is a double staining identification diagram provided in an embodiment of this application.

[0027] Attached image description:

[0028] 1. Base; 2. X-axis mechanical tension assembly; 21. First tension assembly; 211. Clamping part; 212. Connecting rod; 213. Displacement actuator; 214. Force sensor; 22. Second tension assembly; 3. Y-axis mechanical tension assembly; 31. Third tension assembly; 32. Fourth tension assembly; 4. Sample testing platform; 5. Water bath. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this application. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0030] It should be noted that if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on enabling those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0031] This application provides a method for identifying tissue at the boundary of myocardial infarction, including the following steps:

[0032] Biaxial mechanical tensile testing was performed on the cardiac tissue to be identified: the tissue between the stiffness of normal myocardial tissue and the stiffness of myocardial infarction tissue was the first potential boundary region;

[0033] Double staining identification of the cardiac tissue to be identified: First, stain with Evans blue staining solution, then stain with 2,3,5-triphenyltetrazolium chloride staining solution, observe the staining results, the red area is the second potential boundary area;

[0034] The overlapping portion of the first potential boundary region and the second potential boundary region is the myocardial infarction boundary region.

[0035] The method for identifying the boundary zone of myocardial infarction in this application combines the mechanical properties and chemical staining results of the cardiac tissue to be identified, and identifies the boundary zone of myocardial infarction from a physical and chemical perspective to ensure the accuracy of the identification results.

[0036] In some implementations, the steps of the biaxial tensile test include:

[0037] A heart tissue sample is obtained, a tensile force is applied to the heart tissue sample along a first direction and a second direction, and the stiffness value of the heart tissue sample is measured, wherein the angle between the first direction and the second direction is 90°.

[0038] Specifically, the steps for obtaining heart tissue samples include:

[0039] (1) After inducing anesthesia with 5% isoflurane, open the chest and incise the inferior vena cava to drain blood. Perfuse the heart from the apex of the left ventricle with phosphate-buffered saline containing 150 mM potassium chloride to induce cardiac arrest in the saline solution. Remove the heart to obtain it.

[0040] (2) Embed the heart tissue block in 2% low melting point agarose, mount it on the platform of a vibratory slicer, and cut out a sample with a thickness of 500 μm.

[0041] In some embodiments, the strain ratio of the tensile force in the first direction to the tensile force in the second direction is at least one of 2:1, 4:3, or 1:1.

[0042] In some embodiments, the mass ratio of Evans blue dye in the Evans blue staining solution is 0.5-3%. For example, the mass ratio of Evans blue dye in the Evans blue staining solution is 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%, etc. The mass ratio of 2,3,5-triphenyltetrazolium chloride in the 2,3,5-chlorotriphenyltetrazolium staining solution is 1-3%, for example, the mass ratio of 2,3,5-triphenyltetrazolium chloride in the 2,3,5-chlorotriphenyltetrazolium staining solution is 1%, 1.5%, 2%, 2.5%, or 3%, etc.

[0043] Evans blue dye has a strong affinity for myocardial tissue. After ligation, Evans blue staining solution is injected into the inferior vena cava, preventing myocardial tissue with blocked blood flow in the left anterior descending coronary artery from being stained, while myocardial tissue with normal blood supply is stained dark blue, thus distinguishing normal myocardial tissue from myocardial tissue without blood supply (including the infarcted area and the infarct boundary area). 2,3,5-Triphenyltetrazolium chloride (TTC) is a lipid-soluble photosensitizing complex. As a proton acceptor of the pyridine-nucleoside structural enzyme system in the respiratory chain, it reacts with dehydrogenases in normal and ischemic myocardial tissue, resulting in a red color (normal myocardium + myocardial infarction boundary area). However, the dehydrogenase activity in infarcted myocardial tissue decreases sharply and cannot react, so it remains pale (myocardial infarction area). Since Evans blue dye appears dark blue in normal myocardial tissue, it masks the staining of TTC. Therefore, after double staining in a myocardial infarction model, normal myocardial tissue appears blue, myocardial infarction boundary area appears red, and infarcted tissue appears pale.

[0044] Please refer to Figures 1 and 2. This application embodiment also provides a biaxial mechanical tensile testing device 100, which generally includes: a base 1 and an X-axis mechanical tensile component 2, a Y-axis mechanical tensile component 3 and a sample testing platform 4 disposed on the base 1. The angle formed by the extension direction of the X-axis mechanical tensile component 2 and the extension direction of the Y-axis mechanical tensile component 3 is 90°.

[0045] Furthermore, the X-axis mechanical tensile assembly 2 includes a first tensile assembly 21 and a second tensile assembly 22 arranged symmetrically with the sample detection platform 4 as the center of symmetry. The Y-axis mechanical tensile assembly 3 includes a third tensile assembly 31 and a fourth tensile assembly 32 arranged symmetrically with the sample detection platform 4 as the center of symmetry. Each of the first tensile assembly 21, the second tensile assembly 22, the third tensile assembly 31, and the fourth tensile assembly 32 has a clamping part 211 on the side closest to the sample detection platform 4. At least one of the clamping parts 211 of the first tensile assembly 21 and the second tensile assembly 22 can move along the extending direction of the X-axis mechanical tensile assembly 2, and at least one of the clamping parts 211 of the third tensile assembly 31 and the fourth tensile assembly 32 can move along the extending direction of the Y-axis mechanical tensile assembly 3. At least one of the first tensioning assembly 21 and the second tensioning assembly 22 is provided with a force sensor 214, and at least one of the third tensioning assembly 31 and the fourth tensioning assembly 32 is provided with a force sensor 214. When the clamping part 211 of the first tensioning assembly 21, the second tensioning assembly 22, the third tensioning assembly 31 and the fourth tensioning assembly 32 moves, the force sensor 214 can record the force value in the direction in which it is located.

[0046] In some embodiments, the clamping part may include a plurality of spaced stainless steel needles. The side of the stainless steel needles away from the stretching components (first stretching component 21, second stretching component 22, third stretching component 31, and fourth stretching component 32) has a certain curvature, bending towards the sample detection platform 4 to facilitate insertion into the heart tissue to be identified for fixation. The number of stainless steel needles may be 3 or 5.

[0047] The biaxial mechanical tensile testing device 100 can be used to perform biaxial mechanical tensile tests on cardiac tissue to be identified. Specifically, the cardiac tissue to be identified is fixed on the sample testing platform 4 by four clamping parts 211. Forces in the X-axis and Y-axis directions can be applied to the cardiac tissue by the X-axis mechanical tensile assembly 2 and the Y-axis mechanical tensile assembly 3, and the force values ​​in the X-axis and Y-axis directions are recorded by the force sensor 214. By combining the applied forces in the X-axis and Y-axis directions and the data recorded by the force sensor, the mechanical properties of the cardiac tissue to be identified can be obtained, including the Green-Lagrange strain tensor and the second type of Piola-Kirchhoff stress, or the tensile stress-strain curves in the direction of myocardial fibers and the tensile stress-strain curves perpendicular to the direction of myocardial fibers. Subsequent calculations can then be used to determine whether the cardiac tissue to be identified is in the boundary zone of myocardial infarction.

[0048] In some embodiments, the sample detection platform 4 is a glass slide, and the biaxial mechanical tensile testing device 100 further includes a microscopic observation component, preferably a laser confocal microscope. The laser confocal microscope can excite the autofluorescence of elastin and collagen in myocardial tissue for three-dimensional in-situ scanning, observing the changes in the spatial position of small blood vessels and myocardial cells during stretching, thereby obtaining the coupling relationship between myocardial fibers and small blood vessels during deformation, and thus enabling the identification of the boundary zone of myocardial infarction.

[0049] In some embodiments, the first tensioning assembly 21, the second tensioning assembly 22, the third tensioning assembly 31, and the fourth tensioning assembly 32 each include a displacement actuator 213 and a connecting rod 212, which are sequentially and fixedly connected. The displacement actuator 213 can drive the connecting rod 212 to translate, thereby moving the clamping part 211 and generating a tension force on the cardiac tissue to be identified, which is fixed by the clamping part 211.

[0050] In some embodiments, a water bath 5 is provided on the base 1, and the X-axis mechanical tensile assembly 2, the Y-axis mechanical tensile assembly 3, and the sample detection platform 4 are arranged in the water bath. The water bath 5 can be used to hold liquids such as buffer solutions, so that the heart tissue to be identified is kept in a solution of a certain concentration during the biaxial mechanical tensile test, thus better restoring the physiological environment of the heart tissue to be identified.

[0051] This application also provides an application of the biaxial mechanical tensile testing device described above in the identification of tissues in the boundary zone of myocardial infarction.

[0052] This application also provides a method for identifying the boundary zone of myocardial infarction using the biaxial mechanical tensile testing device described above, including the following steps:

[0053] Obtain heart tissue samples;

[0054] The true thickness was measured using a dial gauge at nine different locations on the heart tissue sample.

[0055] Place the heart tissue sample flat on the sample testing platform, remove excess tissue along the edge of the sample testing platform, and use the clamping part to fix the heart tissue sample.

[0056] A preload force of 10 mN was applied along the X and Y axes. Then, with a strain of 30% on the X axis and a tensile speed of 10 μm / s as a reference, biaxial tensile forces were applied on the X and Y axes respectively. After all loading was completed, stress relaxation was performed for 300 s. The force value changes were recorded by the sensor and the force value change curve was plotted.

[0057] In some embodiments, the biaxial tensile strain ratio is at least one of 2:1, 4:3 or 1:1.

[0058] The following detailed implementation method will provide further explanation.

[0059] Example 1: Establishment of a mouse model of myocardial infarction

[0060] Mice (C57BL / 6J) were intubated and ventilated with 2% isoflurane. After anesthesia and fixation, a thoracotomy was performed on the left fourth intercostal space to expose the heart. The left anterior descending coronary artery was permanently ligated using 8-0 nylon sutures to establish a mouse model of myocardial infarction. Ultrasound examination of the mouse heart was performed, and the results are shown in Figure 3. As can be seen from Figure 3, the mouse heart ultrasound showed clear anterior wall contractile abnormalities, and the ejection fraction was reduced to below 50%, indicating a successful animal model.

[0061] Example 2: Biaxial Mechanical Tensile Test

[0062] (1) Obtaining normal myocardial tissue, myocardial infarction tissue, and myocardial infarction boundary tissue: After inducing anesthesia with 5% isoflurane, the chest was opened, and the inferior vena cava was incised to drain blood. The heart was perfused from the apex of the left ventricle with phosphate-buffered saline containing 150 mM potassium chloride to stop the heart from beating in physiological saline. The heart was excised and obtained; the heart tissue block was embedded in 2% low-melting-point agarose, mounted on the platform of a vibratory microtome, and the sample thickness was cut to 500 μm;

[0063] (2) After obtaining the sample, the actual thickness was measured at 9 different locations using a dial gauge;

[0064] (3) Place the sample flat on the sample testing platform, carefully remove excess tissue along the edge of the platform, and pass the five stainless steel needles of each hook clamp through the sample into the guide hole.

[0065] (4) Adjust the position of the four displacement actuators of the planar biaxial stretching instrument and set the distance between the two relative needles to 9.5 mm;

[0066] (5) Apply a preload of 10mN along the X-axis and Y-axis. The initial length of the sample in the fiber and perpendicular fiber directions is defined as the distance between the relative hook clamps under the preload.

[0067] (6) With 30% strain on the X-axis and a tensile speed of 10 μm / s as a reference, quasi-static biaxial tension with strain ratios of 2:1, 4:3 and 1:1 were applied on the X-axis and Y-axis respectively. After all loading was completed, stress relaxation was performed for 300s.

[0068] Force changes were recorded using sensors, and force change curves were plotted, as shown in Figure 4. Based on Figure 4 and calculations, the stiffness of normal myocardial tissue was found to be 180.0 ± 5.4 kPa; the stiffness of infarcted tissue was 321.5 ± 46.9 kPa; and the stiffness of the boundary zone was between the two, at 236.8 ± 38.1 kPa. Therefore, the tissue between the stiffness of normal myocardial tissue and the stiffness of infarcted tissue is considered the boundary zone of myocardial infarction.

[0069] Example 3: Double staining identification

[0070] (1) Using the mouse myocardial infarction model constructed in Example 1, the outflowing vena cava was freed, the distal end was clamped, and 3 mL of 1% Evans Blue staining solution (EB staining solution, prepared by mixing 1 g Evans Blue with 100 mL of double-distilled water) was injected through the upper end of the vascular clamp. The heart was then quickly removed, rinsed with pre-cooled PBS, and after stopping the heartbeat in 30 mM KCl solution, it was frozen at -20°C for 30 min.

[0071] (2) The heart tissue from (1) was cut into 1.5 mm thick slices using a mold and placed in a 6-well plate containing 3 mL of 2% 2,3,5-triphenyltetrazolium chloride. The slices were incubated in a 37°C water bath in the dark for 20 min. After incubation, the slices were fixed in 4% FPA fixative and observed and photographed the next day.

[0072] The final staining results of the sections are shown in Figure 5. As can be seen from Figure 5, the red area is the boundary area of ​​myocardial infarction, the blue area is the normal area, and the white area is the myocardial infarction area.

[0073] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for identifying tissue at the boundary of a myocardial infarction, characterized in that, Including the following steps: Biaxial mechanical tensile testing was performed on the cardiac tissue to be identified: the tissue between the stiffness of normal myocardial tissue and the stiffness of myocardial infarction tissue was the first potential boundary zone; Double staining identification of the cardiac tissue to be identified: First, stain with Evans blue staining solution, then stain with 2,3,5-triphenyltetrazolium chloride staining solution, observe the staining results, the red area is the second potential boundary area; The overlapping portion of the first potential boundary region and the second potential boundary region is the myocardial infarction boundary region.

2. The method for identifying the boundary zone of myocardial infarction according to claim 1, characterized in that, The steps of the biaxial tensile test include: A heart tissue sample is obtained, a tensile force is applied to the heart tissue sample along a first direction and a second direction, and the stiffness value of the heart tissue sample is measured. The angle between the first direction and the second direction is 90°.

3. The method for identifying the boundary zone of myocardial infarction according to claim 2, characterized in that, The strain ratio of the tensile force in the first direction to the tensile force in the second direction is at least one of 2:1, 4:3, or 1:

1.

4. The method for identifying the boundary zone of myocardial infarction according to claim 1, characterized in that, The Evans blue staining solution contains 0.5-3% Evans blue dye by mass. The mass ratio of 2,3,5-triphenyltetrazolium chloride in the 2,3,5-chlorotriphenyltetrazolium staining solution is 1-3%.

5. A biaxial tensile testing device, characterized in that, include: The base and the X-axis mechanical tensile component, the Y-axis mechanical tensile component and the sample testing platform disposed on the base, wherein the angle formed by the extension direction of the X-axis mechanical tensile component and the extension direction of the Y-axis mechanical tensile component is 90°. The X-axis mechanical tensile component includes a first tensile component and a second tensile component arranged symmetrically with the sample detection platform as the center of symmetry, and the Y-axis mechanical tensile component includes a third tensile component and a fourth tensile component arranged symmetrically with the sample detection platform as the center of symmetry. Each of the first stretching component, the second stretching component, the third stretching component, and the fourth stretching component has a clamping part on the side near the sample detection platform. At least one of the clamping parts of the first stretching component and the second stretching component can move along the extension direction of the X-axis mechanical stretching component, and at least one of the clamping parts of the third stretching component and the fourth stretching component can move along the extension direction of the Y-axis mechanical stretching component. At least one of the first tensioning assembly and the second tensioning assembly is provided with a force sensor, and at least one of the third tensioning assembly and the fourth tensioning assembly is provided with a force sensor, the force sensor being configured to record force values.

6. The biaxial tensile testing device according to claim 5, characterized in that, The first tensioning assembly, the second tensioning assembly, the third tensioning assembly, and the fourth tensioning assembly all include a displacement driver and a connecting rod, and the displacement driver, the connecting rod, and the clamping part are fixedly connected in sequence.

7. The biaxial tensile testing device according to claim 5, characterized in that, The base is equipped with a water bath, and the X-axis mechanical tensile component, the Y-axis mechanical tensile component, and the sample detection platform are arranged in the water bath.

8. The application of the biaxial mechanical tensile testing device according to any one of claims 5 to 7 in the identification of tissues in the boundary zone of myocardial infarction.

9. A method for identifying the boundary zone of myocardial infarction using the biaxial mechanical tensile testing device according to any one of claims 5 to 7, characterized in that, include: Obtain heart tissue samples; The true thickness was measured using a dial gauge at nine different locations on the heart tissue sample. The heart tissue sample is laid flat on the sample detection platform, excess tissue is removed along the edge of the sample detection platform, and the heart tissue sample is fixed using the clamping part. A preload force of 10 mN was applied along the X and Y axes. Then, with a strain of 30% on the X axis and a tensile speed of 10 μm / s as a reference, biaxial tensile forces were applied on the X and Y axes respectively. After all loading was completed, stress relaxation was performed for 300 s. The force value change was recorded by the sensor and the relationship curve between the force value change and time was recorded.

10. The method according to claim 9, characterized in that, The strain ratio of the biaxial tensile force is at least one of 2:1, 4:3 or 1:1.

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