Low shear stress asymmetric bleeding window and interventional catheter pump

Abstract

The present invention discloses a low shear stress asymmetric bleeding window and an interventional catheter pump. The bleeding window comprises a hollow cylindrical body and a blood outlet formed on the body. The bleeding window is configured for accommodating an impeller for pumping the blood. The impeller can be driven to rotate in an operational direction to pump the blood out through the blood outlet. The blood outlet comprises a contour surface for defining the contour shape of the blood outlet. The contour surface comprises a first flow-inflecting surface and a second flow-inflecting surface located at a first end in an axial direction, and the first flow-inflecting surface and the second flow-inflecting surface are arc-shaped and are smoothly connected. The first flow-inflecting surface is located upstream of the second flow-inflecting surface in the operational direction, and the curvature radius of the first flow-inflecting surface is greater than the curvature radius of the second flow-inflecting surface, allowing the first flow-inflecting surface and the second flow-inflecting surface to form an axially asymmetric configuration.

Description

Low shear stress asymmetric bleeding window and interventional catheter pump Technical Field

[0001] The present invention relates to the field of medical devices, and in particular to a low-shear-stress asymmetric bleeding window and an invasive catheter pump. Background Art

[0002] The interventional catheter pump can be percutaneously inserted into the patient's left ventricle. During operation, it can pump blood from the patient's left ventricle to the aorta, thereby reducing the workload of the heart and providing assistance to the heart.

[0003] The struts are part of the catheter pump's force-conducting structure, connecting the cannula to the main body of the catheter pump, which holds the motor and also houses the bleed window through which blood is ejected. Blood flow is propelled by the impeller, which rotates in response to the motor. This creates high circumferential velocities in the bleed window and strut regions. These high velocities result in considerable impact, or shear, stress on the blood from the struts. Ideally, bleed window struts would be absent from the design, but their presence appears unavoidable given their aforementioned structural function.

[0004] To reduce blood trauma caused by impact or shear stress, current catheter pumps use different bleeding window structures. However, existing bleeding windows still have high shear stress at the support position, which increases blood trauma, especially hemolysis.

[0005] For example, the first known embodiment (hereinafter referred to as Comparative Example 2), represented by publication numbers or announcements such as CN114929327A, CN116549806A, CN117045931A, and CN219539244U, employs a symmetrical bleeding window design. This is currently the most commonly used and technologically mature bleeding window solution. One of the main reasons for this widespread adoption is its simplicity and ease of fabrication, which is crucial for smaller components like bleeding windows and is often a primary consideration for developers during design.

[0006] However, as mentioned above, when blood is pushed due to the rotation of the impeller, a large circumferential velocity is generated. Combined with its axial flow velocity, the blood actually presents a spiral axial flow. On any axial cross-section, the blood appears to pass through the bleeding port in an inclined direction and impact the pillars. Therefore, the defects of this bleeding window are also very obvious, namely: the straight pillars of the bleeding window are at a large angle to the velocity vector of the blood, resulting in a large shear force on the blood, and more serious hemolysis caused by blood damage. Therefore, this scheme hopes to achieve the purpose of reducing blood damage by optimizing the structure of the bleeding window in various ways, such as trying or adopting pillars with different cross-sectional shapes, optimizing the rounded corner design of the pillar edges, etc. However, the defects of the structural principle itself result in the purpose of reducing shear and hemolysis being achieved to a low degree.

[0007] In a second known embodiment (hereinafter referred to as Comparative Example 1), represented by publication numbers or announcements such as US11235138B2 and CN117159914A, the bleeding window utilizes a twisted or tilted structure, aiming to align the struts with the blood velocity vector as described above. However, this bleeding window structure presents significant manufacturing challenges. Furthermore, since the twist or tilt angle of the struts for a specific bleeding window is fixed, the blood velocity vector required to align with it is also determined, but this is often uncontrollable. This is because blood velocity varies with impeller speed. This often and unavoidably occurs when, at a certain impeller speed required to provide a specific assist flow rate to the patient, the blood velocity vector is misaligned with the strut twist direction, leading to more severe blood damage and hemolysis.

[0008] Furthermore, there is concern that most mechanical circulatory support systems have higher blood recirculation rates at lower pump speeds, leading to increased blood damage. Technical issues

[0009] The purpose of the present invention is to provide an asymmetric bleeding window with low shear stress and an invasive catheter pump to solve the problems existing in the above-mentioned prior art, reduce the impact and shear stress of the bleeding window on the blood flow, and reduce the hemolytic reaction.

[0010] Furthermore, in a further embodiment of the present invention, the contour shape of the asymmetric bleeding window is further optimized to reduce the increased backflow in the pump recirculation area under low flow operating conditions, thereby reducing potential blood damage. Technical Solutions

[0011] To achieve the above object, the present invention provides the following solutions:

[0012] A low shear stress asymmetric bleeding window includes a hollow cylindrical body and a bleeding port formed on the body. The bleeding window is used to accommodate an impeller for pumping blood, and the impeller can be driven to rotate along the working direction to pump blood out of the bleeding port. The bleeding port includes a contour surface that defines its contour shape, and the contour surface includes a first inflection surface and a second inflection surface located at the first end along the axial direction, and the first inflection surface and the second inflection surface are arc-shaped and smoothly connected. The first inflection surface is located upstream of the second inflection surface along the working direction, and the curvature radius of the first inflection surface is greater than the curvature radius of the second inflection surface, so that the first inflection surface and the second inflection surface form an asymmetric structure along the axial direction.

[0013] An invasive catheter pump comprises the bleeding window as described above. Beneficial effects

[0014] Compared with the prior art, the present invention has achieved the following technical effects:

[0015] The asymmetric structure formed by the first and second turning surfaces gives the blade a larger flow area on the pressure side than on the suction side. This larger flow area on the pressure side increases the speed and efficiency of blood flowing through the bleeding outlet. As the impeller rotates from upstream to the first turning surface, blood pushed by the pressure side can quickly flow out through the larger first turning surface.

[0016] Efficient blood discharge through the bleeding port shortens the contact time between the blood and the impeller and struts. Consequently, the blood is subjected to shear stress for a shorter period of time. Furthermore, efficient blood discharge through the bleeding port can at least partially reduce the amount of blood that accumulates at the bleeding port, minimizing eddy currents and alleviating the multiple shear stresses exerted on the blood by the impeller and struts. This results in lower shear levels, less damage, and improved hemolytic properties.

[0017] In addition, the smaller passing area of ​​the suction surface can provide greater blood reflux resistance when the blade rotates from the second turning surface to the downstream, thereby reducing blood reflux and increasing the blood flow rate of the pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a schematic diagram of a catheter pump according to an embodiment of the present invention when used as a left ventricular assist device;

[0019] FIG2 is a schematic diagram of the three-dimensional structure of a catheter pump according to an embodiment of the present invention;

[0020] 3A to 3C are enlarged views of the parts within the dotted box in FIG. 2 ;

[0021] FIG4 is a schematic diagram of the cross-sectional structure of the drive motor and the impeller;

[0022] FIG5 is a front view of a bleeding window according to an embodiment of the present invention;

[0023] FIG6 is a schematic diagram of any bleeding site in FIG5 ;

[0024] FIG7 is a flow field and shear stress diagram of Comparative Example 1;

[0025] FIG8 is a flow field and shear stress diagram of Comparative Example 2;

[0026] FIG9 is a diagram showing the flow field and shear stress of a bleeding window using an embodiment of the present invention;

[0027] FIG10 is a comparison chart of the hemolysis index of blood when the bleeding window of the embodiment of the present invention is used and the bleeding windows of Comparative Examples 1 and 2 are used;

[0028] FIG11 is a graph showing the percentage of blood shear stress below 450 Pa when the bleeding window of Comparative Example 1 is used;

[0029] FIG12 is a graph showing the percentage of blood shear stress below 450 Pa when the bleeding window of Comparative Example 2 is used;

[0030] FIG13 is a graph showing the percentage of blood shear stress below 450 Pa during the bleeding window according to an embodiment of the present invention;

[0031] FIG14 is a comparison chart showing the proportions of shear stress on blood when the bleeding window is ≤450Pa, >450Pa, >1000Pa, and >1500Pa, respectively, when using the bleeding window of the embodiment of the present invention and the bleeding windows of Comparative Examples 1 and 2;

[0032] FIG15 is a schematic diagram of the blood reflux area when the bleeding window of Comparative Example 1 is used;

[0033] FIG16 is a schematic diagram of the blood reflux area when the bleeding window of Comparative Example 2 is used;

[0034] FIG17 is a schematic diagram of a blood reflux area when a bleeding window is used according to an embodiment of the present invention;

[0035] FIG18 is a comparison diagram of the blood reflux area volume and reflux ratio when the bleeding window of the embodiment of the present invention is used and the bleeding windows of Comparative Examples 1 and 2 are used;

[0036] FIG19 is a schematic diagram showing the relationship between the axial offset distance between the connection point of the first inflection surface and the first lateral flow surface and the proximal end point of the blade and the lift;

[0037] FIG20 is a diagram showing the blood flow velocity when the connection point between the first inflection surface and the first lateral flow surface is aligned with the proximal end point of the blade along the axial direction;

[0038] FIG21 is a diagram showing the blood flow velocity when the connection point between the first inflection surface and the first lateral flow surface is offset axially backward relative to the proximal end point of the blade;

[0039] FIG22 is a diagram showing the blood flow velocity when the connection point between the first inflection surface and the first lateral flow surface is offset axially forward relative to the proximal end point of the blade;

[0040] FIG23 is a graph showing the expanded profiles of different embodiments;

[0041] Figure 24 shows the radial velocity vector field of the bleeding window with a symmetrical design under the operating conditions of a flow rate of 1 L / min and a motor speed of 44,000 RPM;

[0042] Figure 25 shows the radial velocity vector field of the bleeding window with a symmetrical design under the operating conditions of a flow rate of 2 L / min and a motor speed of 44,000 RPM;

[0043] Figure 26 shows the radial velocity vector field of the bleeding window with a symmetrical design under the operating conditions of a flow rate of 3 L / min and a motor speed of 44,000 RPM;

[0044] Figure 27 shows the radial velocity vector field of the bleeding window with an asymmetric design under the operating conditions of a flow rate of 1 L / min and a motor speed of 44,000 RPM;

[0045] Figure 28 shows the radial velocity vector field of the bleeding window with an asymmetric design under the operating conditions of a flow rate of 2 L / min and a motor speed of 44,000 RPM;

[0046] FIG29 shows the radial velocity vector field of the bleeding window with an asymmetric design under the operating conditions of a flow rate of 3 L / min and a motor speed of 44,000 RPM. Modes for Carrying Out the Invention

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the figures in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0049] As used herein, the terms "proximal," "distal," "anterior," and "posterior" are used relative to the physician operating the catheter pump. The terms "proximal" and "posterior" refer to the portion relatively close to the physician, while the terms "distal" and "anterior" refer to the portion relatively far from the physician. For example, the extracorporeal portion of the catheter is located at the proximal or posterior end, while the pump assembly is located at the distal or anterior end. It should be understood that the terms "proximal," "distal," "anterior," and "posterior" are defined for ease of description, and that catheter pumps can be used in many orientations and positions. Therefore, these terms expressing relative positional relationships are not intended to be limiting or absolute.

[0050] Unless otherwise indicated, directional terms such as "upper, lower, top, and bottom" generally refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular, or gravitational direction. Similarly, for ease of understanding and description, "inside" and "outside" refer to the inside and outside relative to the outline of each component itself, but these directional terms are not intended to limit the present invention.

[0051] In an exemplary application scenario, the catheter pump 1000 of this embodiment can be used as a left ventricular assist device. As shown in Figures 1 and 2, the catheter pump 1000 includes a catheter 100 and a pump assembly 900 connected to the distal end of the catheter 100. The pump assembly 900 includes a fluid cannula 400, a blood inlet window 420 and a bleeding window 410 connected to the distal and proximal ends of the fluid cannula 400, respectively. The blood inlet window 420 is formed with a blood inlet port 421, and the bleeding window 410 is formed with a bleeding port 411. The pump assembly 900 can be inserted into a subject's body using percutaneous puncture and pushed forward in the subject's aorta by the catheter 100 until the distal end of the pump assembly 900 passes through the aortic valve AV and enters the left ventricle LV. The fluid cannula 400 is positioned across the aortic valve AV, with the blood inlet port 421 located in the left ventricle LV and the bleeding port 411 located in the ascending aorta AAO. In this way, when the pump assembly 900 is in operation, it can pump blood in the left ventricle LV to the ascending aorta AAO to assist the heart's pumping function and reduce the heart's burden.

[0052] It is worth noting that the above-mentioned example of being used as a left ventricular assist is only one feasible application scenario of the catheter pump 1000. In other feasible scenarios that cannot be explicitly excluded, the catheter pump 1000 can also be used as a right ventricular assist, and the pump assembly 900 can be inserted into the right ventricle, and the pump assembly 900 pumps the blood in the vein into the right ventricle when it is in operation. Of course, the catheter pump 1000 can also be used to assist the kidneys as a renal pump. The following mainly describes the scenario in which the catheter pump 1000 is used as a left ventricular assist. However, based on the above description, it can be seen that the scope of protection of the embodiments of the present invention is not limited thereto.

[0053] As shown in Figures 1 to 4, the catheter pump 1000 further includes an impeller 300 disposed within the bleeding window 410, a drive motor 200 for driving the impeller 300 in rotation, and a protective structure 800 disposed at the distal end of the fluid cannula 400. The drive motor 200 includes a motor housing 210 connected to the distal end of the catheter 100, a stator 230 disposed within the motor housing 210, and a rotor driven by the stator 230. The rotor includes a rotating shaft 220 and a magnet 240 disposed on the rotating shaft 220. The magnet 240 couples with the stator 230 to drive the rotating shaft 220 to rotate in an operating direction O (clockwise or counterclockwise). The distal end of the rotating shaft 220 extends from the distal end of the motor housing 210. The fluid cannula 400 is connected to the distal end of the motor housing 210, and the impeller 300 is connected to the distal end of the rotating shaft 220 and is fixedly connected to the rotating shaft 220 (for example, by at least one of interference fit and gluing), thereby being driven by the rotating shaft 220 to rotate along the working direction O, so as to draw blood in the left ventricle LV into the fluid cannula 400 through the blood inlet window 420 and pump it from the bleeding window 410 to the ascending aorta AAO.

[0054] Protective structure 800 guides pump assembly 900 during intervention, guiding it smoothly into the left ventricle (LV). It also provides support once inside the LV, preventing pump assembly 900 from swinging within the LV. Protective structure 800 can have a rounded head, as shown in Figures 1 and 2 , or a pigtail structure with a rounded outer surface to prevent damage to blood vessels and the inner wall of the LV.

[0055] As shown in Figure 5, the bleeding window 410 is used to accommodate the impeller 300 for pumping blood. The impeller 300 can be driven to rotate along the working direction O to pump blood out of the bleeding port 411. The bleeding window 410 includes a body 423 that is roughly hollow and cylindrical. The body 423 is formed with a bleeding port 411. The bleeding port 411 passes through the inner and outer walls of the body 423 for blood to pass through. There are multiple bleeding ports 411, which are distributed at intervals along the circumference, and pillars 422 are formed between adjacent bleeding ports 411. Furthermore, the pillars 422 are formed between the first lateral flow surface 418 of one bleeding port 411 and the second lateral flow surface 419 of the adjacent bleeding port 411. It can be understood that adjacent bleeding ports 411 are separated by pillars 422.

[0056] The shape of bleeding window 411 affects blood flow dynamics, and thus the hemolytic performance of catheter pump 1000 during operation. To reduce the impact and shear stress of bleeding window 410 on blood flow and mitigate hemolytic reactions, the shape of bleeding window 411 is designed as follows. It should be noted that, in this specification, "substantially" can be understood as close to, approximately, or within a predetermined range of a target value.

[0057] The bleeding outlet 411 includes a contour surface that defines its outline shape. The contour surface has a first end and a second end along the axial direction of the bleeding window 410. The first end is the distal end of the bleeding outlet 411, and the second end is the proximal end of the bleeding outlet. Alternatively, the first end is located axially far upstream in the direction of blood pumping, and the second end is located axially far downstream in the direction of blood pumping. In this specification, the direction pointing toward the impeller 300 facing away from the catheter 100 is defined as the distal direction, and the direction pointing toward the catheter 100 facing away from the impeller 300 is defined as the proximal direction. The terms "axial," "circumferential," and "radial" herein refer to the axial, circumferential, and radial directions of the bleeding window 410.

[0058] As shown in Figures 3A to 3C, 5, and 6, along the working direction O, the first end of the contour surface of the bleeding outlet 411 includes a first inflection surface 413, a first guide surface 412, and a second inflection surface 414, which are connected in sequence. The first guide surface 412 is a straight surface along the circumference, and the first inflection surface 413 and the second inflection surface 414 are respectively connected to the first guide surface 412 at both ends along the circumference. The first inflection surface 413 and the second inflection surface 414 are connected to the first guide surface 412 in a smooth transition. The smooth transition is used to avoid sharp edges at the connection or corner, reducing shear stress and hemolysis of the blood at the corner.

[0059] The first and second turning surfaces 413 and 414 are arcuate, with the first turning surface 413 located upstream of the second turning surface 414 along the working direction O. That is, when the impeller rotates, the first turning surface 413 is located on the suction side of the blade, while the second turning surface 414 is located on the pressure side of the blade. Therefore, compared to the second turning surface 414, the first turning surface 413 is located on the suction side, where blood pressure is lower.

[0060] In this embodiment, the radius of curvature R1 of the first turning surface 413 differs from the radius of curvature R2 of the second turning surface 414. Specifically, R1>R2. Specifically, the curvature R1 along the first turning surface 413 varies compared to the curvature R2, which remains constant along the second turning surface 414. This results in the first turning surface 413 and the second turning surface 414 forming an axially asymmetric structure. The asymmetric structure of the first end of the bleeding outlet 411 allows the blood to drain through the first turning surface 413 with a larger area than that through the second turning surface 414.

[0061] As shown in Figures 3A to 3C , the blade 302 has a pressure surface 3021 and a suction surface 3022. The pressure surface 3021 is the side of the blade 302 that is subjected to pressure when blood flows, and is used to perform work on the blood, causing it to flow. The suction surface 3022 is the side of the blade 302 that is subjected to pressure when blood flows, and is the side facing away from the pressure surface 3021. At some point during the rotation of the impeller 300 while pumping blood, blood tends to escape from the suction surface 3022, resulting in a decrease in pressure at the suction surface 3022, manifesting as a suction force exerted by the suction surface 3022 on the blood.

[0062] As impeller 300 rotates and pumps blood, blood can flow over the proximal ends of blades 302, from pressure surface 3021 to suction surface 3022 on the back of blades 302. This phenomenon is known as backflow. Blood backflow can lead to poor hydraulic efficiency. "Poor hydraulic efficiency" means that despite the high-speed rotation of impeller 300, the blood flow ultimately pumped into the aorta AAO is very low. In other words, the blood flow supported or assisted by catheter pump 1000 is low, which is undesirable.

[0063] Furthermore, blood reflux can exacerbate hemolysis because the reflux persists as the impeller 300 rotates. This means the refluxed blood is constantly stirred by the impeller 300 and cannot be promptly discharged from the bleeding port 411. This causes the refluxed blood to form a vortex near the bleeding port 411, causing this blood to repeatedly rub against the impeller 300 and the support 422. This results in the blood being subjected to shear stress for a longer period of time, with greater intensity, resulting in more severe damage, and further exacerbating the hemolysis.

[0064] It should be noted that blood reflux is an inevitable hydraulic phenomenon. The resulting decrease in blood flow cannot be compensated by increasing the impeller speed by 300 as commonly understood. Instead, it will lead to more serious hemolysis and increased energy consumption.

[0065] The bleeding port 411 adopts the above-mentioned asymmetric structure design of this embodiment, which can better solve this problem, as follows.

[0066] As the impeller 300 rotates along the working direction O, because the first turning surface 413 is located upstream of the second turning surface 414, the pressure surface 3021 of the blade 302 has a larger passage area than the suction surface 3022. The larger passage area of ​​the pressure surface 3021 can increase the speed and efficiency of blood passing through the bleeding port 411. As the impeller 300 rotates from the upstream to the first turning surface 413, the blood pushed by the pressure surface 3021 of the blade 302 can quickly flow out through the larger first turning surface 413. During this process, the blood does not have time to flow back, that is, to flow out of the bleeding port 411. Alternatively, blood that is about to or is already flowing back is discharged through the first turning surface 413 due to inertia or centrifugal force. In this way, the blood pumping rate can be effectively increased.

[0067] Efficient blood discharge through the bleeding port 411 shortens the contact time between the blood and the impeller 300 and the support 422. Consequently, the blood is subjected to shear stress for a shorter period of time. Furthermore, efficient blood discharge through the bleeding port 411 can at least partially reduce the amount of blood that accumulates at the bleeding port 411 and reduce eddy currents. This reduces the multiple shear stresses applied to the blood by the impeller 300 and the support 422, resulting in lower shear levels, less damage, and improved hemolytic properties.

[0068] Furthermore, the smaller passage area of ​​the suction surface 3022 provides greater resistance to blood backflow during the blade 302's rotation from the second inflection surface 414 to the downstream, thereby reducing blood backflow. This is because blood that has not backflowed, meaning it remains on the pressure surface 3021 of the blade 302, but has not yet exited the current bleeding outlet 411, is pushed by the blade 302 to the next bleeding outlet 411 and is first discharged from the first inflection surface 413 of the next bleeding outlet 411. This prevents blood from gathering at the bleeding outlet 411 and forming a vortex, thereby improving the hydraulic effect and reducing hemolysis.

[0069] The following comparative analysis compares the asymmetric bleeding port structure of this solution with prior art bleeding port structures. As described above, prior art bleeding port structures fall into two categories: one employs a symmetrical design, referred to as Comparative Example 2. The other employs an inclined or twisted design, referred to as Comparative Example 1. By analyzing the flow field simulation, shear stress ratio, and blood reflux ratio of the bleeding port, the shear stress and hemolytic response under different bleeding port structures were determined.

[0070] Figures 7 through 9 illustrate the flow field and shear stress around pillar 422 when the blood flow rate is 3 L / min and the impeller 300 rotates at 45,000 RPM. Figures 7 through 9 illustrate the flow field and shear stress for the bleeding windows of Comparative Example 1, Comparative Example 2, and the embodiment of the present invention, respectively. It should be noted that all comparative data for these three solutions is based on identical boundary conditions, such as impeller speed and bleeding window structure (inner diameter, outer diameter, length, etc.). The only variable is the shape of the three bleeding openings.

[0071] As shown in Figures 7 to 9, the bleeding windows of Comparative Examples 1 and 2 exhibit areas of high shear stress (red areas) on the pillars, while such areas are absent on the pillars 422 of the present embodiment. This means that, compared to Comparative Examples 1 and 2, the peak shear stress experienced by the pillars 422 of the bleeding window of the present embodiment is smaller. Because the shear stress on the pillars is exerted by the blood, the shear stress experienced by the blood is an equal and interactive force. In other words, compared to the prior art, the asymmetric bleeding window structure of the present embodiment effectively reduces the shear stress experienced by the blood, thereby reducing hemolysis.

[0072] Furthermore, based on the flow field and shear stress diagrams, a quantitative analysis of the shear stress of the three solutions described above was performed, resulting in a comparison of the Mechanical Intravascular Hemolysis (MIH) index, as shown in Figure 10. As shown in Figure 10, the MIH value for the bleeding site using the solution of the embodiment of the present invention is the smallest, demonstrating that this solution can effectively reduce hemolysis and achieve better hemolytic performance.

[0073] In addition, it is generally believed in the art that when the shear stress to which blood is subjected is lower than 450Pa, the blood will not be destroyed. That is, only when the shear stress is higher than 450Pa will the blood be destroyed and hemolysis will occur. Therefore, the greater the proportion of blood subjected to shear stress lower than 450Pa, the lower the probability of hemolysis. Therefore, in order to further verify the difference in hemolytic effect between the solution of the embodiment of the present invention and the two comparative examples, a study was conducted on the distribution ratio of the shear stress magnitude to which the blood is subjected. As shown in Figures 11 to 16, respectively, are graphs showing the proportion of blood subjected to shear stress lower than 450Pa when the bleeding window is adopted using Comparative Example 1, Comparative Example 2, and the embodiment of the present invention. The horizontal axis in the figure is shear stress and the vertical axis is percentage. In order to clearly understand the difference between the three solutions, the above three shear stress ratio graphs were quantified, and the proportions of shear stress ≤450Pa, >450Pa, >1000Pa, and >1500Pa were calculated, respectively, to obtain the schematic diagram shown in Figure 14.

[0074] As can be seen from Figure 14, using the solution of the embodiment of the present invention, the proportion of blood subjected to shear stress ≤450Pa is the highest, while the proportion of blood subjected to shear stress >450Pa is smaller than that in both Comparative Examples 1 and 2. This shows that the asymmetric bleeding port structure in this solution can effectively reduce blood shear stress and hemolysis.

[0075] It is worth noting that the MIH value of the bleeding outlet using this solution is slightly lower than that of Comparative Example 1, and the proportion of shear stress ≤450Pa to which the blood is subjected is also slightly higher than that of Comparative Example 1. This shows that the hemolytic effect of the bleeding outlet using this solution is slightly better than that of Comparative Example 1, which is surprising. Because according to conventional thinking, the inclined outlet of Comparative Example 1 can at least partially adapt to the vector direction of the blood outlet velocity, and the shear stress should be smaller (although it has been greatly reduced compared to the traditional symmetrical outlet solution of Comparative Example 2), but its hemolytic effect is still slightly worse than that of this solution. The reason may be that the outlet is inclined, resulting in a larger surface length of its support facing the flow, which in turn leads to an increase in the shear surface and shear length.

[0076] Regarding blood reflux, Figures 15 to 17 are schematic diagrams of the blood reflux area when using the bleeding windows of Comparative Example 1, Comparative Example 2, and the embodiment of the present invention, respectively. Figure 18 is a comparative diagram of the blood reflux area volume and reflux ratio when using the bleeding window of the embodiment of the present invention and the bleeding windows of Comparative Examples 1 and 2. It can be seen that the volume and ratio of the blood reflux area are the smallest when using the bleeding window of this embodiment, which is related to the greater reflux resistance provided by the second inflection surface 414 with a smaller radius. As can be seen from the above, lower blood reflux is beneficial for increasing blood pump flow rate and reducing hemolysis. Therefore, the smaller the blood reflux area, the better the hydraulic effect. That is, under the same operating conditions such as speed and head, the greater the blood flow rate, the greater the blood flow supported or assisted by the catheter pump 1000.

[0077] In summary, the asymmetric structure of the bleeding port 411 according to the embodiment of the present invention allows the blade 302 to have a larger blood flow area on the pressure side 3021 and a smaller blood flow area on the suction side 3022. This distribution of blood flow area between the pressure side 3021 and the suction side 3022 of the blade 302 achieves lower shear stress and reflux on the blood, thereby positively enhancing the hemolysis and hydraulics of the catheter pump 1000.

[0078] As described above, by providing a straight first flow guide surface 412 at the most upstream side of the bleeding outlet 411 in the direction of blood flow, and smoothly transitioning the two curved first inflection surfaces 413 and second inflection surfaces 414 through the straight first flow guide surface 412, this design makes it easier to form smooth transitions or rounded corners at the edges of the bleeding outlet 411, and improves the smoothness of the connection.

[0079] Of course, in some embodiments, the first turning surface 413 and the second turning surface 414 can also be directly connected by a smooth transition, eliminating the intermediate transition section of the first guide surface 412. However, this may be more difficult to achieve in terms of process than using the first guide surface 412 to achieve a smooth transition. Therefore, compared to the smooth transition between two curved surfaces with different curvature radii, the smooth transition between a curved surface and a straight surface is easier. Moreover, this increased process difficulty can also lead to a poorer smoothness of the connection for small components such as bleeding windows, thereby affecting the hemolysis effect.

[0080] In addition, it should be noted that, in one embodiment, the first turning surface 413 and / or the second turning surface 414 can be a single arc surface, that is, the first turning surface 413 can be composed of an arc surface with a radius of R1, and the second turning surface 414 can also be composed of an arc surface with a radius of R2, and the curvature radii of the turning surfaces are the radii of the corresponding arc surfaces.

[0081] Of course, in another feasible embodiment, the first turning surface 413 and / or the second turning surface 414 may also be smooth surfaces formed by sequentially connecting multiple circular arc surfaces, quasi-circular arc surfaces, and spline curves. In this case, the curvature radii R1 and R2 of the turning surfaces 413 and 414 are the average of the combined curvature radii of the multiple circular arc surfaces, quasi-circular arc surfaces, and spline curves. The combined curvature radius is the curvature radius of a point on the surface or of a segmented calculation unit segment, where R1 = Average (R11, R12 ... R1n) and R2 = Average (R21, R22 ... R2m). R11, R12…R1n are the combined curvature radii of the multiple arc surfaces, quasi-arc surfaces, and spline curves included in the first turning surface 413; R21, R22…R2m are the combined curvature radii of the multiple arc surfaces, quasi-arc surfaces, and spline curves included in the second turning surface 414; and n and m are the numbers of corresponding turning surface calculation unit sections.

[0082] The first turning surface 413 and the second turning surface 414 can both be single arc surfaces, or can both be curved surfaces formed by sequentially connecting multiple arc surfaces, quasi-arc surfaces, and spline curves, or one of them can be a single arc surface and the other can be a curved surface formed by sequentially connecting multiple arc surfaces, quasi-arc surfaces, and spline curves. This embodiment does not limit this.

[0083] As shown in FIG6 , the distance between the projections of the two ends of the first guide surface 412 on a plane perpendicular to the axial direction is defined as W1, i.e., the circumferential width of the first guide surface 412, hereinafter referred to as the width of the first guide surface 412. Among them, W1 of the first guide surface 412 is smaller than the curvature radius R2 of the second turning surface 414, i.e., W1 <R2。

[0084] In practice, the radius of curvature R1 of the first turning surface 413 is greater than or equal to the sum of the radius of curvature R2 of the second turning surface 414 and the width W1 of the first guide surface 412, i.e., R1 ≥ R2 + W1. Furthermore, the ratio of the radius of curvature R2 of the second turning surface 414 to the radius of curvature R1 of the first turning surface 413 is greater than or equal to 0.8, i.e., 0.8 ≤ R2 / R1 < 1. The ratio of the width W1 of the first guide surface 412 to the radius of curvature R2 of the second turning surface 414 is less than or equal to 0.15, i.e., 0 < W1 / R2 ≤ 0.15.

[0085] A larger ratio of R2 / R1 (greater than or equal to 00.8, further greater than 0.85, 0.9) and a smaller ratio of W1 / R2 (less than or equal to 00.15, further less than 0.12, 0.1) are used to compress the width W1 of the first guide surface 412 as much as possible, so that the width W1 of the first guide surface 412 is much smaller than the curvature radius R1 of the first turning surface 413 and the curvature radius R2 of the second turning surface 414 (W1≪R1, R2, that is, the width W1 of the first guide surface 412 is very short), and the curvature radius R2 of the second turning surface 414 is relatively close to the curvature radius R1 of the first turning surface 413. Since the upstream of the bleeding outlet 411 can be regarded as the entrance end of the blood flowing out through the bleeding outlet 411, such a design can ensure that the upstream of the bleeding outlet 411 is occupied by as many smooth curved surfaces as possible, namely the first turning surface 413 and the second turning surface 414, thereby reducing the shear stress of the blood at this location and further reducing blood damage.

[0086] As shown in Figure 6, R1≥R2+W1, which is used to ensure that the endpoint of the first turning surface 413 close to the upstream end (the upper endpoint shown in the figure) is located on or enters the side of the central axis P of the bleeding outlet 411 close to the second turning surface 414, thereby ensuring that the curvature radius R1 of the first turning surface 413 can always be greater than the curvature radius R2 of the second turning surface 414.

[0087] Of course, R2 + W1 should not be significantly smaller than R1, otherwise the corner of the bleeding opening 411 at the second inflection surface 414 will be too small. While this may be beneficial for preventing blood backflow, an excessively small corner can be detrimental to hemolysis. Therefore, in practice, R1 should be slightly larger than R2 + W1. The applicant's research has found that R1 / (R2 + W1) should be no greater than 1.2, meaning R1 / (R2 + W1) is between 1 and 1.2, and further between 1 and 1.12, to achieve both blood backflow prevention and hemolysis performance.

[0088] In this embodiment, the central axis P of the bleeding port 411 is the axis passing through the midpoint of the second diversion surface 415. As described below, the bleeding port 411 is a symmetric structure at the second axial end. Therefore, the axis passing through the midpoint of the second diversion surface 415 is the central symmetry axis of the third flow turning surface 416 and the fourth flow turning surface 417, and the first side flow surface 418 and the second side flow surface 419, which can be regarded as the central axis P of the bleeding port 411.

[0089] As shown in FIGS. 5 and 6, the contour surface of the bleeding port 411 further includes a second diversion surface 415, a third flow turning surface 416 and a fourth flow turning surface 417 at the second end. The second diversion surface 415 is a straight surface along the circumferential direction and is parallel to the first diversion surface 412. The third flow turning surface 416 and the fourth flow turning surface 417 are arc-shaped and are respectively smoothly connected to the two circumferential ends of the second diversion surface 415. The third flow turning surface 416 is located upstream of the fourth flow turning surface 417 along the working direction O.

[0090] The first diversion surface 412 is located upstream of the second diversion surface 415 along the blood pumping direction, and the blood pumping direction is from the distal end to the proximal end. The distance between the projections of the two ends of the second diversion surface 415 on the plane perpendicular to the axial direction is defined as W2, that is, the circumferential width of the second diversion surface 415, which is hereinafter simply referred to as the width of the second diversion surface 415.

[0091] The radius of curvature R3 of the third flow turning surface 416 is the same as the radius of curvature R4 of the fourth flow turning surface 417, so that the third flow turning surface 416 and the fourth flow turning surface 417 form a symmetric structure along the axial direction. The following relationship exists among W1, W2, R1, R2, R3 and R4: R1 + W1 + R2 = R3 + W2 + R4. Among them, W1 < W2, R3 = R4 < R2 < R1 < W2. Further, W2 is 15-20 times of W1, 1.1-1.3 times of R1, and 2-5 times of R3 or R4. That is, the width W2 of the second diversion surface 415 is the largest among the above values (except L1 and L2), aiming to expand the opening area of the bleeding port 411 at the most downstream end as much as possible, so that more blood deflects and drains towards the proximal end of the bleeding port 411, thereby increasing the blood flow towards the ascending aorta AAO direction.

[0092] The contour surface of the bleeding port 411 also includes a first lateral flow surface 418 and a second lateral flow surface 419 connecting the first end and the second end. The first lateral flow surface 418 connects the first inflection flow surface 413 and the third inflection flow surface 416, and the second lateral flow surface 419 connects the second inflection flow surface 414 and the fourth inflection flow surface 417. The first lateral flow surface 418 and the second lateral flow surface 419 both extend straight along the axial direction, making the straight side shape of the bleeding port 411 of this embodiment different from the inclined or twisted side shape of Comparative Example 1. As described above, the straight side shape of the bleeding port 411 helps reduce the difficulty of the manufacturing process. Similarly, this reduced manufacturing difficulty is beneficial to the consistency of the final shape of the bleeding port 411, for example, eliminating burrs or rough edges, which is also beneficial to the hemolysis effect.

[0093] The axial length L1 of the first lateral flow surface 418 is less than the axial length L2 of the second lateral flow surface. The following relationship exists between R1, R2, R3, R4, L1, and L2: R1+L1+R3=R2+L2+R4. Since R3=R4, the difference between L1 and L2 is also the difference between R1 and R2. The ratio relationship between R1, R2, and W1 has been explained above. If the values ​​of R1 and R2 are determined, the values ​​of L1 and L2 are also determined. Therefore, the effect of L1 < L2 can be referred to the above description of the ratio of R1 to R2 and W1, and will not be repeated here.

[0094] As described below, the second lateral flow surface 419 and the second guide surface 415 serve as the two main areas for blood to flow out of the bleeding outlet 411. Therefore, it is necessary to ensure a large outflow area for these two main blood outflow areas. Similar to the relationship between the circumferential width W2 of the second guide surface 415 and the radius of curvature R1 of the first turning surface 413 described above, in this embodiment, the axial length L2 of the second lateral flow surface 419 is also greater than the radius of curvature R1 of the first turning surface 413. As described above, the large radius of curvature R1 of the first turning surface 413 provides a large flow area, and its ultimate purpose in increasing flow rate is to reduce shear stress. In other words, increasing blood flow is still primarily accomplished or achieved by the second lateral flow surface 419 and the second guide surface 415. Therefore, in this embodiment, by setting the dimensions L2 and W2 of the blood outflow area of ​​the second lateral flow surface 419 and the second guide surface 415 to be larger than the radius of curvature R1 of the first turning surface 413, it is beneficial to ultimately increase blood flow.

[0095] As shown in Figures 3A to 3C, the connection point M between the first inflection surface 413 and the first lateral flow surface 418 (hereinafter referred to as point M) is substantially flush with the proximal end point N of the blade 302 (hereinafter referred to as point N). The term "substantially flush" means that point M and point N have an axial offset distance D within a certain range. The offset is a bidirectional offset along the axial direction. It can mean that point M is offset distally relative to point N, as shown in Figure 3C. In this case, point M is axially distal to point N, and the offset in this case is defined as a positive offset. It can also mean that point M is offset proximally relative to point N, as shown in Figure 3B. In this case, point M is axially proximal to point N, and the offset in this case is defined as a negative offset. When the offset distance D has a value range of 0, as shown in Figure 3A, point M is flush with point N.

[0096] The purpose of designing points M and N to be roughly aligned axially is to fully utilize the large flow area of ​​the first turning surface 413 to enhance the hydraulic effect. Because the blood at point N is completely free from the propulsion of the blades 302 and swirls out through the bleeding port 411, aligning the blood at point N with point M ensures that all of the blood, which has swirled out of the blades 302, can flow out through the large flow area of ​​the first turning surface 413, thereby ensuring efficient and high-volume blood outflow.

[0097] As shown in Figures 3B and 3C , whether point N is offset too far or too far proximally relative to point M, the effect of the large flow area of ​​first turning surface 413 on increasing blood flow may be weakened, thereby causing a decrease in blood flow. Furthermore, some of the blood that escapes from blade 302 at point N may flow out through the second turning surface 414 with a smaller radius of curvature or the straight second lateral surface 419, further exacerbating blood damage.

[0098] The applicant's research has revealed a relationship between the pump head and the aforementioned offset distance D, as shown in Figure 19. In this relationship graph, the horizontal axis represents the offset distance D in mm, and the vertical axis represents the head in mmHg. It should be noted that, similar to the other flow field diagrams, this relationship assumes the same flow rate (3 L / min). Therefore, a greater head indicates better hydraulic performance.

[0099] Figure 19 shows that the pump head and offset distance D exhibit a roughly normal distribution. However, this distribution is not a standard normal distribution. Specifically, when offset distance D is 0, that is, when points M and N are axially aligned, the pump head is not at its maximum. The offset distance D corresponding to maximum pump head is approximately 0.42 mm. This result suggests that a certain degree of positive offset can actually be beneficial in increasing the pump head, something the applicants had not anticipated.

[0100] The reason for this phenomenon is currently unclear. The applicant speculates that the possible cause is that the positive offset indicates that the proximal endpoint N of the blade 302 has proximally passed point M. The side of the bleeding outlet 411 opposite point M is the straight second lateral flow surface 419, indicating that the proximal endpoint N of the blade 302 now falls within the confines of the second lateral flow surface 419. As described above, blood accelerated by the blade 302 forms a mixed axial and radial flow, and the second lateral flow surface 419 is one of the areas where blood flows out (the other major area is the second guide surface 415). Therefore, if the proximal endpoint N of the blade 302 falls within the confines of the second lateral flow surface 419, the primary blood outflow area, it can be beneficial for increasing the head.

[0101] Because the offset distance D corresponding to the maximum head value is a fixed point value, and this fixed point value is not a special point value, this poses a significant challenge to the assembly of the impeller 300 and the bleeding window 410. Generally speaking, in a relationship that conforms to a normal distribution, 0.8 times the maximum value generally meets the requirements. Therefore, guided by the above relationship, when the offset distance D ranges from -0.13mm to 0.96mm (i.e., -0.13mm ≤ D ≤ 0.96mm), the head is greater than 0.8 times the maximum value. Furthermore, when the offset distance D ranges from -0.05mm to 0.89mm (i.e., -0.05mm ≤ D ≤ 0.89mm), the head reaches greater than 0.85 times the maximum value.

[0102] By setting the above-mentioned offset distance D range, under the premise that the flow rate or head of the pump is acceptable, axial redundancy can be provided for the assembly of the impeller 300 and the bleeding window 410, thereby reducing the difficulty of assembling the pump and improving the assembly efficiency.

[0103] It is worth noting that the above only describes the effect of the offset distance D on the pump head or flow rate. In fact, the positional relationship between the impeller 300 and the bleeding window 410 is a systemic issue that affects not only the pump head or flow rate, but also the blood flow rate and shear stress.

[0104] Figures 20 to 22 show the flow field diagrams when point M is not offset, negatively offset, and positively offset relative to point N, respectively. As shown in Figure 21, when M is negatively offset relative to point N, blood will generate a higher flow velocity in an area near the surface of the hub 301 (shown in the dotted box in the figure), and this area extends from the front-center section of the hub 301 to the bleeding outlet 411. Therefore, the shear stress on the blood is much higher than that shown in Figure 20. As shown in Figure 22, when M is positively offset relative to point N, blood will generate a larger backflow area in the middle section of the blade 302 (shown in the dotted box on the left side of the figure), and form a more obvious area of ​​reduced flow velocity near the bleeding outlet 411 (shown in the dotted box on the right side of the figure).

[0105] In contrast, as shown in FIG20 , when M is not offset from point N, the overall blood flow rate is uniform, and there is no obvious high flow rate or low flow rate phenomenon in the area close to the surface of the hub 301 and the bleeding outlet 411 area, and the volume of the reflux area is also significantly reduced compared to FIG22 .

[0106] Therefore, M is not offset from point N, that is, M is axially aligned with point N, or the offset distance D is 0. This is the optimal embodiment that takes all performance indicators (head or flow rate, blood flow field uniformity, and shear stress) into consideration. Furthermore, although M is not offset from point N, the corresponding offset distance D is also a fixed point value, this fixed point value is a special point value, namely, M is axially aligned with point N. Therefore, this will not significantly adversely affect the assembly of impeller 300 and bleeding window 410.

[0107] The symmetrical design of the bleed port can have a negative impact in the blade pass area because the blood flows through the pressure and suction sides of the blade with different radial velocities. Under low flow conditions, the symmetrical design may cause the blood to stay in the recirculation area longer.

[0108] As shown in Figure 23, this embodiment employs an asymmetric design. A turning surface 413, with a larger radius of curvature (i.e., a larger second-order derivative value) on the left proximal edge and a relatively smaller curvature (i.e., a smaller second-order derivative value) on the right distal edge, defines an obstacle region at the upper left edge of the bleeding window. The shape of the obstacle meets the requirement of being kink-free, meaning it is continuous and differentiable.

[0109] The Unwrapped Profile of the obstacle is located between the Upper Limit of Obstruction Profile and the Lower Limit of Obstruction Profile.

[0110] Blocking profile upper limit: ;

[0111] Blocking contour lower limit: .

[0112] In one embodiment, x = 0 is defined as the boundary between the suction and pressure sides of a rotating impeller blade passing through. The obstacle is located at x ≤ 0 and consists of an upper portion of the profile between (-0.8 ≤ x ≤ 0) and a lower portion of the profile between (-0.875 ≤ x < -0.8), and is defined by the following formula. The unfolded profile satisfies the requirements of having no broken lines at x = -0.8, displaying a horizontal tangent line at x = 0, and displaying a vertical tangent line at x = -0.875.

[0113] Upper contour: ;

[0114] Lower part of the outline: .

[0115] Furthermore, the obstacle is formed by a compact contour in the entire range (-0.875≤x<0) and is defined by the following formula.

[0116] .

[0117] When the impeller in the device rotates counterclockwise (as viewed from the distal end), blood flowing through the impeller acquires a counterclockwise circumferential velocity upon exiting the rotating domain. Since the circumferential velocity is counterclockwise, the radial velocity is primarily determined by the pressure difference between the rotating domain and the outflow domain. Therefore, in the present invention, due to the asymmetric design of the bleed window, the resistance to blood flow back into the upstream region of the rotating domain on the suction side of the blades is significantly increased. This effectively guides blood out of the rotating domain, effectively reducing the recirculation zone and, consequently, blood trauma. This is particularly important under low-flow operating conditions, where the pump's reflux rate is high.

[0118] One of the main challenges in designing catheter pumps is the high recirculation rate caused by unintended operation at low flow rates. As shown in Figure 24, when recirculation occurs, blood flows back through the bleeding window. Under operating conditions with a flow rate of 1 L / min, the recirculation rate through the symmetrical bleeding window is approximately 0.268 L / min, which essentially means that 26.8% of the pump's total flow rate is recirculating within the rotating domain.

[0119] The high recirculation rates of catheter pumps at lower flow rates are well known and have always been a challenge for designers (Reference 1). The inventors of the asymmetric bleeding window profile for microaxial flow pumps discovered that, across the entire range of pump operating conditions, a specific region lacks significant radial flow. As shown in Figures 25 and 26, examining the radial vector field in the bleeding window region under different operating conditions clearly reveals that increasing pump flow rate shifts the region of fluid exiting the window toward the proximal side of the pump, further highlighting the impact of the distal bleeding window profile on the hemodynamics of microaxial flow pumps operating at low flows. Furthermore, radial flow to the distal left of the bleeding window is relatively low under all operating conditions. Another key observation is that the outward radial velocity field is biased to the right of the bleeding window, which is understandable given that the pump rotates counterclockwise when viewed from the distal end.

[0120] Therefore, the inventors identified a region on the distal left side of the bleeding window where a significant outward radial velocity field is not expected to occur under pump operating conditions. By modifying the bleeding window profile, the cross-sectional area of ​​the bleeding window in this region can be reduced, thereby reducing the recirculation rate during low-flow operation. This will improve the hydraulic efficiency and hemocompatibility of the device.

[0121] As shown in Figure 27, due to the asymmetric design, the backflow rate decreased from 268.4 mL / min to 234.5 mL / min at a flow rate of 1 L / min. This represents a significant reduction in backflow rate of approximately 12.5%, while the pump head increased from 94.85 mmHg to 100.04 mmHg and the hydraulic efficiency increased from 11.5% to 12.1%, fully demonstrating the potential of the asymmetric bleeding window design. Although the symmetric bleeding window has been optimized for the operating conditions of the microaxial flow pump, it should be noted that the asymmetric shape has better hemodynamic performance under low flow conditions.

[0122] A second point to investigate is whether the asymmetric design leads to any adverse changes in the pump's hemodynamic performance under other operating conditions. To investigate this, the inventors studied operating conditions with flows greater than 1 L / min. As shown in Figures 28 and 29, the recirculation rate differs slightly from that observed with the symmetrical window. The difference between the recirculation rate values ​​at both 2 L / min and 3 L / min operating conditions is less than 6 mL / min. This slight change in recirculation values ​​is negligible, and it can be concluded that the asymmetric profile does not significantly affect recirculation under other operating conditions. Furthermore, by examining the pump's generated head and efficiency, the pump's head increases from 96.8 mmHg to 98.6 mmHg at a flow rate of 2 L / min. At a flow rate of 3 L / min, the pressure head decreases from 39.3 mmHg to 37.6 mmHg. These minor changes are negligible. Therefore, it can be concluded that the asymmetric profile has minimal impact on the pump's hemodynamics under high flow rate conditions.

[0123] Reference 1: Schöps, Malte; Groß-Hardt, Sascha H.; Schmitz-Rode, Thomas; Steinseifer, Ulrich; Brodie, Daniel; Clauser, Johanna C.; Karagiannidis, Christian (2021): Hemolysis at low blood flow rates: in-vitro and in-silico evaluation of a centrifugal blood pump. In: Journal of translational medicine 19 (1), S. 2. DOI: 10.1186 / s12967-020-02599-z.

[0124] Of course, it will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, but also encompasses the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all variations that fall within the meaning and range of equivalents of the claims be included in the present invention, and any figure signs in the claims should not be construed as limiting the claims to which they relate.

Claims

1. A low shear stress asymmetric bleeding window comprising: A body in the shape of a hollow cylinder, and a bleeding hole formed on the body; The bleeding window is used to accommodate an impeller for pumping blood, and the impeller can be driven to rotate along a working direction to pump blood out of the bleeding port; Its characteristics are: The bleeding port includes a contour surface defining its contour shape, and the contour surface includes: A first flow turning surface and a second flow turning surface are axially located at the first end, wherein the first flow turning surface and the second flow turning surface are arc-shaped and smoothly connected; The first turning surface is located upstream of the second turning surface along the working direction, and the curvature radius of the first turning surface is greater than the curvature radius of the second turning surface, so that the first turning surface and the second turning surface form an asymmetric structure along the axial direction.

2. The bleeding window according to claim 1, wherein: The contour surface further comprises: a first guide surface located at the first end and connecting the first inflection surface and the second inflection surface; The first guide surface is a straight surface along the circumferential direction, the first turning surface and the second turning surface are respectively connected to the two ends of the first guide surface along the circumferential direction, and the first turning surface and the second turning surface are both smoothly connected to the first guide surface.

3. The bleeding window according to claim 2, wherein: The radius of curvature of the first turning surface is equal to or slightly greater than the sum of the radius of curvature of the second turning surface and the width of the first guide surface along the circumferential direction; the term "slightly greater than" means that the upper limit of the ratio R1 / (R2+W1) is not greater than 1.2, where R1 is the radius of curvature of the first turning surface, R2 is the radius of curvature of the second turning surface, and W1 is the width of the first guide surface along the circumferential direction.

4. The bleeding window according to claim 2, wherein: The ratio of the curvature radius of the second turning surface to the curvature radius of the first turning surface is greater than or equal to 0.8, and the ratio of the circumferential width of the first guide surface to the curvature radius of the second turning surface is less than or equal to 0.

15.

5. The bleeding window according to claim 2, wherein: The contour surface further comprises: a second flow-guiding surface axially located at the second end opposite to the first end, the second flow-guiding surface being a straight surface along the circumferential direction; a third and a fourth arc-shaped flow turning surface respectively connected to two ends of the second flow guide surface in the circumferential direction, wherein the third flow turning surface is located upstream of the fourth flow turning surface in the working direction; Among them, the third turning surface and the fourth turning surface are both smoothly connected to the second guide surface, and the curvature radius of the third turning surface is the same as the curvature radius of the fourth turning surface, so that the third turning surface and the fourth turning surface form an axially symmetrical structure.

6. The bleeding window according to claim 5, characterized in that: The curvature radius of the fourth turning surface is smaller than the curvature radius of the second turning surface, and the curvature radius of the second turning surface is smaller than the circumferential width of the second guide surface.

7. The bleeding window according to claim 5, wherein: The first guide surface is located upstream of the second guide surface along the pumping direction of blood, and the width of the first guide surface along the circumferential direction is smaller than the width of the second guide surface along the circumferential direction.

8. The bleeding window according to claim 5, wherein: The contour surface of the bleeding outlet also includes: a first lateral flow surface connecting the first turning flow surface and the third turning flow surface, and a second lateral flow surface connecting the second turning flow surface and the fourth turning flow surface; the first lateral flow surface and the second lateral flow surface both extend straightly along the axial direction.

9. The bleeding window according to claim 8, wherein: The curvature radius of the first turning surface is smaller than the axial length of the second lateral flow surface and is also smaller than the circumferential width of the second guide surface.

10. The bleeding window according to claim 8, wherein: The impeller includes a hub and blades formed on the hub; The connection point between the first inflection surface and the first lateral surface is offset in the axial direction from the proximal end point of the blade by a distance between -0.13 mm and 0.96 mm. The connection point is positively offset toward the distal end compared to the proximal end point, and negatively offset toward the proximal end.

11. The bleeding window according to claim 10, wherein: The axial offset distance of the connection point relative to the proximal end point is between -0.05 mm and 0.89 mm.

12. The bleeding window according to claim 10, wherein: The connection point is aligned with the proximal end point along the axial direction, that is, the offset distance is 0.

13. The bleeding window according to claim 1, wherein: When the impeller rotates through the bleeding port, the first inflection surface is located on the suction side of the blade, and the second inflection surface is located on the pressure side of the blade; The first inflection surface is configured to form an obstacle having a developed profile located between an upper blocking profile limit and a lower blocking profile limit, wherein the upper blocking profile limit and the lower blocking profile limit are defined by the following formula: Blocking profile upper limit: ； Blocking contour lower limit: 。 14. The bleeding window according to claim 13, wherein: x=0 is defined as the boundary between the suction side and the pressure side of the blade when the blade of the rotating impeller passes through the bleeding port; the expanded profile is located at x≤0 and consists of an upper profile portion between -0.8≤x≤0 and a lower profile portion between -0.875≤x<-0.

8. The upper and lower profile portions are defined by the following formulas: Upper contour: ； Lower part of the outline: 。 15. The bleeding window according to claim 13, wherein: The unfolded profile is formed by a compact profile in the entire range -0.875≤x<0, and the compact profile is defined by the following formula: 。 16. An interventional catheter pump, characterized in that: include: The bleeding window according to any one of claims 1 to 15.

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