CN117959585B

CN117959585B - Low shear stress asymmetric bleeding window and interventional catheter pump

Info

Publication number: CN117959585B
Application number: CN202410361648.5A
Authority: CN
Inventors: 马尔特·舍普斯; 法希德·法罗赫内扎德; 徐宁; 张存义
Original assignee: Life Shield Medical Technology Suzhou Co ltd
Current assignee: Life Shield Medical Technology Suzhou Co ltd
Priority date: 2024-03-27
Filing date: 2024-03-27
Publication date: 2024-05-31
Anticipated expiration: 2044-03-27
Also published as: CN117959585A

Abstract

The invention discloses an asymmetric bleeding window with low shear stress and an interventional catheter pump. The bleeding window is used for accommodating an impeller for pumping blood, and the impeller can be driven to rotate along the working direction so as to pump the blood out of the bleeding outlet. The bleeding port comprises a contour surface defining the contour shape of the bleeding port, the contour surface comprises a first turning surface and a second turning surface which are axially positioned at the first end, and the first turning surface and the second turning surface are in arc shape and are smoothly connected. The first turning flow surface is located upstream of the second turning flow surface along the working direction, and the curvature radius of the first turning flow surface is larger than that of the second turning flow surface, so that the first turning flow surface and the second turning flow surface form an axial asymmetric structure.

Description

Low shear stress asymmetric bleeding window and interventional catheter pump

Technical Field

The invention relates to the field of medical instruments, in particular to an asymmetric bleeding window with low shear stress and an interventional catheter pump.

Background

An interventional catheter pump may be percutaneously inserted into the left ventricle of a patient's heart and during operation blood may be pumped from the left ventricle of the patient's heart into the aorta, thereby reducing cardiac load and enabling assistance to the heart.

The support post is part of the force-guiding structure of the catheter pump which connects the cannula with the catheter pump body, which secures the motor, while the catheter pump body also carries a bleeding window for injecting blood flow. The blood flow is propelled by the impeller, which is driven in rotation by the motor, creating a high circumferential velocity in the bleeding opening of the bleeding window and in the area of the struts, whereas a high velocity means that the struts have a rather high impact or shear stress on the blood. Ideally, no bleeding window struts are present in the design, but this seems unavoidable because they have the structural function described above.

In order to reduce blood trauma caused by shock or shear stress, current catheter pumps employ different bleeding window structures. However, existing bleeding windows still have higher shear stresses at the post site, which increases blood trauma, especially hemolysis.

For example, in the first known embodiment (hereinafter referred to as comparative example 2) represented by publication number CN114929327A, CN116549806A, CN117045931A, CN219539244U or the like, the bleeding window adopts a symmetrical structure design, which is also the most commonly used bleeding window scheme at present and is relatively mature in technology. One of the main reasons for this solution being widely adopted is the simplicity and ease of implementation of the manufacturing process, which is very important for the small size of the component, such as the bleeding window, and is often the first factor considered by the developers in the design.

However, as described above, the blood is pushed by the rotation of the impeller, and a large circumferential velocity is generated, and in combination with the axial flow velocity, the blood actually presents a helical axial flow. In either axial section, blood appears to pass through the stoma in an oblique direction and impinge on the strut. Thus, the drawbacks of such a bleeding window are also evident, namely: the straight pillar of the bleeding window has a larger angle with the velocity vector of blood, so that the shearing force on the blood is larger, and the hemolysis caused by blood injury is more serious. Therefore, this solution requires the optimization of the structure of the bleeding window in various ways, for example: attempts or adoption of struts with different cross-sectional shapes, optimization of the fillet design of the strut edges and the like are made to achieve the aim of reducing blood damage. Then, the disadvantages of the structural principle itself lead to the reduction of shear and hemolysis being achieved only to a low extent.

A second known embodiment (hereinafter referred to simply as comparative example 1), represented by publication or publication numbers US11235138B2, CN117159914A, etc., is used for the bleeding window in a twisted or inclined configuration, in order to align the strut with the blood velocity vector as described above. However, such a bleeding window structure can present a significant challenge to the manufacturing process. Also, since the strut twist or tilt angle of a particular bleeding window is established, the velocity vector of the blood required to align with it is also determined, but this is often not controllable. The reason is that the blood speed varies with the impeller speed, as may be the case and inevitably, as follows: the need to provide a specific auxiliary flow to the patient requires that the impeller be operated at a certain rotational speed, the velocity vector of the blood is not aligned with the direction of strut torsion and causes more serious blood damage and hemolysis problems.

Disclosure of Invention

The invention aims to provide an asymmetric bleeding window with low shear stress and an interventional catheter pump, which are used for solving the problems in the prior art, reducing the impact and the shear stress of the bleeding window on blood flow and reducing the hemolysis reaction.

In order to achieve the above object, the present invention provides the following solutions:

an asymmetric bleeding window with low shear stress comprises a hollow cylindrical body and a bleeding opening formed on the body. The bleeding window is used for accommodating an impeller for pumping blood, and the impeller can be driven to rotate along the working direction so as to pump the blood out of the bleeding outlet. The bleeding opening comprises a contour surface limiting the contour shape of the bleeding opening, the contour surface comprises a first turning surface and a second turning surface which are axially positioned at the first end, and the first turning surface and the second turning surface are in arc shape and are smoothly connected. The first turning flow surface is located upstream of the second turning flow surface along the working direction, and the curvature radius of the first turning flow surface is larger than that of the second turning flow surface, so that the first turning flow surface and the second turning flow surface form an axial asymmetric structure.

An interventional catheter pump comprising a bleeding window as hereinbefore described.

Compared with the prior art, the invention has the following technical effects:

The first corner flow surface and the second corner flow surface form an asymmetric structure, so that the blade has a larger passing area on the pressure surface than the suction surface. The pressure surface is bigger through the area, can promote the speed and the efficiency that blood passed through the bleeding mouth for the in-process of impeller from the rotatory first turning flow surface of upper reaches, the blood of pressure surface propelling movement can flow out through bigger first turning flow surface rapidly.

The blood is discharged through the bleeding port with high efficiency, and the contact time between the blood and the impeller and the support column can be shortened. Thus, the time during which the blood is subjected to shear stress is shorter. In addition, the blood is discharged through the bleeding port with high efficiency, the aggregation quantity at the bleeding port can be at least partially reduced, and the vortex phenomenon is reduced, so that the repeated shearing stress of the blood acted by the impeller and the support column can be reduced, the shearing degree of the blood is lower, the damage is smaller, and the hemolysis performance is better.

In addition, the smaller passage area of the suction surface can provide larger blood backflow resistance in the process of rotating the blade from the second turning surface to the downstream, so that the blood backflow phenomenon is reduced, and the blood flow of the pump is improved.

Drawings

FIG. 1 is a schematic illustration of a catheter pump of an embodiment of the present invention as left heart assist;

FIG. 2 is a schematic perspective view of a catheter pump according to an embodiment of the present invention;

FIGS. 3A-3C are enlarged partial views within the dashed box of FIG. 2;

FIG. 4 is a schematic cross-sectional view of a driving motor and an impeller;

FIG. 5 is a front view of a bleeding window according to an embodiment of the present invention;

FIG. 6 is a schematic view of any one of the cuffs of FIG. 5;

FIG. 7 is a graph of flow field and shear stress using comparative example 1;

FIG. 8 is a graph of flow field and shear stress using comparative example 2;

FIG. 9 is a flow field and shear stress diagram of a bleeding window employing an embodiment of the present invention;

FIG. 10 is a graph showing comparison of hemolysis index of blood using the bleeding window of the embodiment of the present invention and the bleeding windows of comparative examples 1 and 2;

FIG. 11 is a graph of the ratio of shear stress to less than 450Pa experienced by blood using the bleeding window of comparative example 1;

FIG. 12 is a graph of the ratio of shear stress to less than 450Pa for blood using the bleeding window of comparative example 2;

FIG. 13 is a graph of the ratio of shear stress to less than 450Pa experienced by blood during a bleeding window according to an embodiment of the present invention;

FIG. 14 is a graph showing the comparison of the ratio of shear stress applied to blood at 450Pa, 1000Pa, 1500Pa, respectively, for the bleeding windows according to the examples of the present invention and the bleeding windows according to comparative examples 1 and 2;

FIG. 15 is a schematic view of the blood return area when the bleeding window of comparative example 1 is used;

FIG. 16 is a schematic view of the blood flashback region when a bleeding window of comparative example 2 is used;

FIG. 17 is a schematic view of a blood flashback region when a bleeding window according to an embodiment of the present invention is used;

FIG. 18 is a graph comparing the volume of the regurgitant blood area and the regurgitant flow ratio of the bleeding window according to the embodiment of the present invention with the bleeding windows according to comparative examples 1 and 2;

FIG. 19 is a schematic view of the relationship between the axial offset distance and lift of the connection point of the first turning flow surface and the first side flow surface and the proximal end point of the vane;

FIG. 20 is a graph of blood flow rate with the connection point of the first crank flow surface to the first side flow surface axially aligned with the proximal end point of the blade;

FIG. 21 is a graph of blood flow velocity at the point of connection of the first crank surface to the first side surface as compared to when the proximal end point of the blade is offset axially rearward;

FIG. 22 is a graph of the flow rate of blood when the point of connection of the first crank surface to the first side surface is offset axially forward as compared to the proximal end point of the blade.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by a person skilled in the art based on the embodiments of the invention without any inventive effort, are intended to fall within the scope of the invention.

It should be noted that the terms "first," "second," and the like in the description and in the claims are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.

The terms "proximal", "distal", "anterior", "posterior" are used herein with respect to a physician manipulating a catheter pump. The terms "proximal", "posterior" and "distal" refer to portions relatively closer to the physician, and the terms "distal" and "anterior" refer to portions relatively farther from the physician. For example, the extracorporeal portion of the catheter is located at the proximal or rear end, while the pump assembly is located at the distal or front end. It should be understood that these orientations of "proximal", "distal", "anterior" and "posterior" are defined for purposes of convenience in description, and that the catheter pump may be used in a variety of orientations and positions, and therefore these terms of relative positional relationships are not limiting and absolute.

Unless otherwise indicated, terms of orientation such as "upper, lower, top, bottom" are used generally with respect to the orientation shown in the drawings, or with respect to the component itself in a vertical, vertical or gravitational orientation. Also, for ease of understanding and description, "inner and outer" refers to inner and outer relative to the profile of each component itself, but the above-mentioned orientation terms are not intended to limit the present invention.

In one exemplary application scenario, the catheter pump 1000 of the present embodiment may be used as a left ventricular assist device. As shown in fig. 1 and 2, catheter pump 1000 includes a catheter 100 and a pump assembly 900 connected to a distal end of catheter 100, pump assembly 900 including: the fluid cannula 400, a blood inlet window 420 and a blood outlet window 410 respectively connected to the distal end and the proximal end of the fluid cannula 400, a blood inlet 421 is formed on the blood inlet window 420, and a blood outlet 411 is formed on the blood outlet window 410. The pump assembly 900 may be inserted into a subject using percutaneous aspiration, advanced by the catheter 100 in the subject's aorta until the distal end of the pump assembly 900 passes through the aortic valve AV into the left ventricle LV with the fluid cannula 400 in a position across the aortic valve AV, the blood inlet 421 in the left ventricle LV and the blood outlet 411 in the ascending aorta AAO. Thus, in operation, the pump assembly 900 may pump blood from the left ventricle LV into the ascending aorta AAO to assist the pumping function of the heart and reduce the heart burden.

It is noted that the above example is used as left ventricular assist is but one possible applicable scenario for catheter pump 1000. In other possible and not explicitly excluded scenarios, catheter pump 1000 may also be used as a right ventricle assist, where pump assembly 900 may be interposed, and where pump assembly 900 operates to pump venous blood into the right ventricle. Of course, catheter pump 1000 may also be adapted for assisting the kidney as a renal pump. The scenario described below is primarily described with respect to the use of the present catheter pump 1000 as left ventricular assist. It will be appreciated from the foregoing that the scope of embodiments of the invention is not limited thereby.

As shown in fig. 1 to 4, the catheter pump 1000 further includes an impeller 300 provided in the bleeding window 410, a driving motor 200 for driving the impeller 300 to rotate, and a protective structure 800 provided at the distal end of the fluid cannula 400. The driving motor 200 includes a motor housing 210 connected to the distal end of the guide tube 100, a stator 230 provided in the motor housing 210, and a rotor driven by the stator 230. The rotor includes a rotation shaft 220, a magnet 240 provided on the rotation shaft 220, the magnet 240 being coupled with the stator 230 to drive the rotation shaft 220 to rotate in a working direction O (clockwise or counterclockwise), a distal end of the rotation shaft 220 protruding from a distal end of the motor housing 210. The fluid cannula 400 is connected to the distal end of the motor housing 210, the impeller 300 is connected to the distal end of the shaft 220, and is fixedly connected (e.g., at least one of interference fit, adhesive) to the shaft 220, thereby being driven by the shaft 220 to rotate in the working direction O, drawing blood in the left ventricle LV into the fluid cannula 400 through the blood intake window 420, and pumping from the bleeding window 410 to the ascending aorta AAO.

The protective structure 800 serves as a guide during intervention of the pump assembly 900 to guide the pump assembly 900 into the left ventricle LV smoothly, while providing support after the pump assembly 900 enters the left ventricle LV to avoid oscillation of the pump assembly 900 within the left ventricle LV. The protective structure 800 may be a rounded head structure as shown in fig. 1 and 2, or a pigtail (Pigtail) structure with a rounded outer surface to prevent damage to blood vessels and left ventricular LV inner wall tissue.

As shown in fig. 5, the bleeding window 410 is for receiving the impeller 300 for pumping blood, and the impeller 300 can be driven to rotate in the working direction O to pump blood from the bleeding opening 411. The bleeding window 410 includes a body 423 having a substantially hollow cylindrical shape, and a bleeding opening 411 is formed in the body 423, and the bleeding opening 411 penetrates through inner and outer side walls of the body 423 for blood to pass through. The number of the bleeding openings 411 is plural, and the bleeding openings 411 are circumferentially spaced apart from each other to form pillars 422 between adjacent bleeding openings 411. Further, a strut 422 is formed between the first side flow surface 418 of one stoma 411 and the second side flow surface 419 of an adjacent stoma 411. It will be appreciated that adjacent ports 411 are separated by struts 422.

The shape of the bleed port 411 affects the kinetics of blood flow and thus the haemolytic performance of the catheter pump 1000 when in operation. In order to reduce the impact and shear stress of the bleeding window 410 on the blood flow and reduce the hemolytic reaction, the shape of the bleeding opening 411 is designed as follows. In this specification, "substantially" is understood to mean close to, approximate to, or within a predetermined range from the target value.

The bleeding opening 411 includes a contour surface defining a contour shape thereof, the contour surface having a first end and a second end in an axial direction of the bleeding window 410. Wherein the first end is the distal end of the stoma 411 and the second end is the proximal end of the stoma. Or the first end is the most upstream in the axial direction along the blood pumping direction, and the second end is the most downstream in the axial direction along the blood pumping direction. In the present specification, a direction toward the impeller 300 and away from the catheter 100 is defined as a distal direction, and a direction toward the catheter 100 and away from the impeller 300 is defined as a proximal direction. The terms "axial", "circumferential" and "radial" are used herein to refer to the axial, circumferential, and radial directions of the blood window 410.

As shown in fig. 3A to 3C, 5 and 6, the first end of the profile surface of the bleeding opening 411 includes a first turning surface 413, a first diversion surface 412 and a second turning surface 414, which are sequentially connected, in the working direction O. The first diversion surface 412 is a straight surface along the circumferential direction, the first turning surface 413 and the second turning surface 414 are respectively connected to two ends of the first diversion surface 412 along the circumferential direction, and the first turning surface 413 and the second turning surface 414 are in smooth transition connection with the first diversion surface 412. The smooth transition connection is used for avoiding sharp corners at the connection or the corners and reducing the shearing stress and the hemolysis phenomenon of blood at the corners.

The first and second turning surfaces 413, 414 are arcuate, and the first turning surface 413 is located upstream of the second turning surface 414 in the working direction O. Thus, the first corner flow surface 413 is on the pressure side where the blood pressure is greater than the second corner flow surface 414.

In this embodiment, the radius of curvature R1 of the first corner surface 413 is different from the radius of curvature R2 of the second corner surface 414, specifically, R1 > R2, so that the first corner surface 413 and the second corner surface 414 form an asymmetric structure along the axial direction. After the first end of the bleeding opening 411 adopts an asymmetric structure, the passage area of the blood supply liquid at the first turning flow surface 413 is larger than the passage area at the second turning flow surface 414.

As shown in fig. 3A to 3C, the blade 302 has a pressure surface 3021 and a suction surface 3022, and the pressure surface 3021 is a surface on the blade 302 that is subjected to pressure when blood flows, and is used to apply work to the blood and to cause the blood to flow. Suction face 3022 is the side of blade 302 that is subjected to pressure during blood flow and is also the side facing away from pressure face 3021. At some point during the rotation of impeller 300, blood tends to break away from suction surface 3022, resulting in a pressure drop at suction surface 3022, which is manifested by suction surface 3022 having a suction effect on the blood.

During the rotation of impeller 300, blood passes over the proximal ends of blades 302 and from pressure surface 3021 of blades 302 to suction surface 3022 at the back side, a phenomenon known as flashback. The blood reflux may cause deterioration of the hydraulic effect, and the above-mentioned "deterioration of the hydraulic effect" is understood as: although the impeller 300 rotates at a high speed, the blood flow rate that is eventually pumped into the aorta AAO is low. That is, the catheter pump 1000 supports or assists a lower blood flow, which is undesirable.

In addition, blood reflux can exacerbate hemolysis, as: the backflow is always present along with the rotation of the impeller 300, which also means that the backflow blood is continuously stirred by the impeller 300 and cannot be timely discharged from the bleeding port 411, so that the backflow blood forms a vortex near the bleeding port 411, and the backflow blood is repeatedly rubbed against the impeller 300 and the support posts 422 repeatedly. The time of the blood subjected to shearing stress is longer, the intensity is higher, the damage is more serious, and the hemolysis phenomenon is further aggravated.

It should be noted that, the backflow of blood is a hydraulic phenomenon, and the decrease of the blood flow caused by the backflow of blood cannot be compensated by the conventionally understood increase of the rotation speed of the impeller 300, which may cause more serious problems such as hemolysis and increase of energy consumption.

The bleeding hole 411 adopts the asymmetric structure design of the present embodiment, which can solve this problem well, as follows.

During rotation of impeller 300 in working direction O, pressure surface 3021 of vane 302 has a larger passage area than suction surface 3022 because first turning surface 413 is upstream of second turning surface 414. The larger passage area of the pressure surface 3021 can increase the speed and efficiency of blood passing through the bleeding opening 411, and in the process of rotating the impeller 300 from the upstream to the first turning surface 413, the blood pushed by the pressure surface 3021 of the blade 302 can flow out through the larger first turning surface 413 rapidly. In the above process, blood has not yet come back, i.e., flows out of the bleeding opening 411. Alternatively, blood that is about to or is being returned is discharged through the first angled surface 413 by inertial or centrifugal forces. Thus, the pumping-out flow rate of blood can be effectively improved.

The blood is efficiently discharged through the bleeding port 411, and the contact time between the blood and the impeller 300 and the strut 422 can be shortened. Thus, the time during which the blood is subjected to shear stress is shorter. In addition, the blood is discharged through the bleeding opening 411 with high efficiency, so that the aggregation amount at the bleeding opening 411 can be at least partially reduced, and the vortex phenomenon can be reduced, thereby reducing the repeated shearing stress of the blood acted by the impeller 300 and the support column 422, and the blood has lower shearing degree, less damage and better hemolysis performance.

In addition, the smaller passage area of suction surface 3022 may provide greater resistance to blood flashback during rotation of blade 302 downstream from second turning surface 414, thereby reducing blood flashback. The reason is that: blood that does not flow back, i.e., remains on the pressure surface 3021 side of the blade 302, but does not flow through the current bleed port 411, is pushed by the blade 302 to the next bleed port 411 and is initially discharged from the first angled flow surface 413 of the next bleed port 411. Thus, blood does not substantially accumulate at the bleeding opening 411 to exhibit vortex flow, thereby improving hydrodynamic effects and reducing hemolysis.

The asymmetric stoma structure of the present solution is compared with the stoma structure of the prior art. As described above, there are two types of structures for the bleeding port in the prior art: one type is that the bleeding port adopts a symmetrical structural design, namely, comparative example 2. The other is that the bleeding port is of an inclined or torsional structural design, namely comparative example 1. And analyzing the flow field simulation condition, the shear stress ratio condition and the blood reflux ratio condition of the bleeding port to obtain the shear stress and the hemolysis reaction condition under different bleeding port structures.

Fig. 7-9 are graphs of flow field and shear stress around strut 422 when the blood flow rate is 3L/min and the impeller 300 speed is 45000 RPM. Wherein fig. 7 to 9 are flow field and shear stress diagrams of the bleeding window employing comparative example 1, comparative example 2 and the examples of the present invention, respectively. All of the following comparative data for these three schemes are based on the same boundary conditions, such as impeller rotation speed, bleeding window structure (inner diameter, outer diameter, length, etc.), and the only variable is the shape of the three bleeding openings.

As can be seen from fig. 7 to 9, the bleeding windows of comparative example 1 and comparative example 2 have a region (red region) where shear stress is large on the strut, but such a region does not appear on the strut 422 of the present embodiment. That is, the struts 422 of the bleeding window of the present embodiment are subjected to a smaller peak of shear stress than comparative examples 1 and 2. Since the shear stress of the strut is applied by the blood, the shear stress to which the blood is subjected is equal to the interaction force. That is, compared with the prior art, the asymmetric bleeding port structure in this solution can effectively reduce the shearing stress to which the blood is subjected, thereby reducing hemolysis.

Further, based on the flow field and the shear stress diagram, the shear stress of the above three schemes is quantitatively analyzed to obtain an index comparison diagram of mechanical intravascular hemolysis (MIH, MECHANICAL INTRAVASCULAR HEMOLYSIS) as shown in fig. 10. As can be seen from fig. 10, the scheme of the embodiment of the present invention is adopted for the bleeding port, the MIH value is the smallest, which indicates that the scheme can effectively reduce the hemolytic reaction and has better hemolytic performance.

Furthermore, it is generally recognized in the art that blood is not destroyed when it is subjected to a shear stress of less than 450 Pa. That is, only when the shear stress is higher than 450Pa, the blood is destroyed and hemolysis occurs. Therefore, the larger the ratio of shearing stress to which the blood is subjected to less than 450Pa, the lower the probability of occurrence of hemolysis. Therefore, in order to further verify the difference in hemolysis effect between the protocol of the present example and the two comparative examples, studies were conducted on the ratio of the size distribution of the shear stress to which blood is subjected. As shown in fig. 11 to 16, which are graphs showing the ratio of the shear stress to which blood is subjected to less than 450Pa when the bleeding windows of comparative example 1, comparative example 2 and examples of the present invention are used, respectively, the abscissa represents the shear stress and the ordinate represents the percentage. To clearly understand the differences between the three schemes, the three shear stress duty ratio diagrams are quantized, and the duty ratios of the shear stress less than or equal to 450Pa, > 1000Pa and > 1500Pa are calculated respectively to obtain a schematic diagram shown in FIG. 14.

As can be seen from FIG. 14, with the embodiment of the present invention, the ratio of shearing stress to blood of 450Pa or less was the highest, and the ratio of shearing stress > 450Pa was small for comparative example 1 and comparative example 2. Therefore, the asymmetric bleeding port structure in the scheme can effectively reduce the shearing stress and the hemolytic reaction of blood.

It is noted that the MIH value of the bleeding port using this embodiment is slightly lower than that of comparative example 1, and the ratio of shear stress to which blood is subjected to 450Pa or less is slightly higher than that of comparative example 1. As a result, it was revealed that the effect of hemolysis on the bleeding port was slightly superior to that of comparative example 1, and this result was unexpected. Since the inclined outlet of comparative example 1 can be adapted at least partially to the vector direction of the blood outlet velocity as understood in the conventional thinking, the shear stress should be smaller (although there has been a substantial drop compared to the conventional symmetrical outlet solution of comparative example 2), but the hemolysis effect is slightly inferior to the present solution, probably due to the inclined outlet, resulting in a larger surface length of the column against which the flow is directed and thus in an increased shear plane and shear length.

As for the blood reflux, as shown in fig. 15 to 17, there are schematic views of the blood reflux regions when the bleeding windows of comparative examples 1, 2 and 2 are used, respectively, and fig. 18 is a comparison of the volume and reflux ratio of the blood reflux regions when the bleeding windows of the examples of the present invention are used and the bleeding windows of comparative examples 1 and 2 are used. It follows that with the bleeding port of the present embodiment, the volume and the ratio of the blood return area is minimized, which is related to the second, smaller radius, corner surface 414 improving the greater resistance to return flow. From the above, it is clear that a lower blood reflux is advantageous for increasing the blood pump flow and reducing the hemolysis phenomena. Therefore, the smaller the blood recirculation zone, the better the hydrodynamic effect, i.e., the greater the blood flow under the same rotational speed and lift conditions, the greater the blood flow supported or assisted by catheter pump 1000.

In summary, the bleeding hole 411 adopts the asymmetric structure according to the embodiment of the present invention, so that the blade 302 obtains a larger passing area on the pressure surface 3021 side and a smaller passing area on the suction surface 3022 side. This distribution of blood passing areas on the pressure and suction sides 3021, 3022 of the blade 302 achieves lower shear stress and reflux to the blood, thereby providing a positive gain to hemolysis and hydraulics of the catheter pump 1000.

As described above, by providing the flat first flow guiding surface 412 at the most upstream of the bleeding port 411 in the blood flow direction, the two arc-shaped first and second turning flow surfaces 413 and 414 are smoothly connected by the flat first flow guiding surface 412 in a transitional manner. This design makes it easier to form a smooth transition or rounded corner at the corners of the stoma 411 and the smoothness of the joint is better.

Of course, in some embodiments, the first and second angled surfaces 413, 414 may also be directly smoothly transitioned, eliminating the intermediate transition section of the first flow guide surface 412. However, this may be difficult in terms of process relative to achieving a smooth transition connection with the first flow guiding surface 412, and thus a smooth transition connection of a cambered surface with a straight surface is easier than a smooth transition connection of two cambered surfaces with different radii of curvature. In addition, the increased difficulty of implementing the process can also lead to poor smoothness of the joint for small-sized parts such as the bleeding window, thereby affecting the hemolysis effect.

Furthermore, in one embodiment, the first turning surface 413 and/or the second turning surface 414 may be a single arc surface, that is, the first turning surface 413 may be formed by an arc surface with a radius R1, and the second turning surface 414 may be formed by an arc surface with a radius R2, where the curvature radius of the turning surfaces is the radius of the corresponding arc surfaces.

Of course, in another possible embodiment, the first corner surface 413 and/or the second corner surface 414 may be smooth curved surfaces formed by sequentially connecting multiple segments of arc surfaces, arc-like surfaces and spline curves, and the radii of curvature R1 and R2 of the corner surfaces 413 and 414 are average values of the comprehensive radii of curvature of the multiple segments of arc surfaces, the arc-like surfaces and the spline curves. The integrated radius of curvature is the radius of curvature of the calculation unit section at a certain point or divided on the curved surface, r1=average (R11, R12 … R1 n), r2=average (R21, R22 … R2 m). R11, R12 … R1n are the comprehensive radii of curvature of the multi-segment arc surface, the similar arc surface and the spline curve contained in the first turning surface 413, R21, R22 … R2m are the comprehensive radii of curvature of the multi-segment arc surface, the similar arc surface and the spline curve contained in the second turning surface 414, and n and m are the number of corresponding turning surface calculation unit sections.

The first corner surface 413 and the second corner surface 414 may be both single arc surfaces, or may be curved surfaces formed by sequentially connecting a plurality of arc surfaces, a similar arc surface and spline curves, or one of the two may be a single arc surface, and the other may be a curved surface formed by sequentially connecting a plurality of arc surfaces, a similar arc surface and spline curves, which is not limited in this embodiment.

As shown in fig. 6, the distance between the projections of both ends of the first flow guiding surface 412 on a plane perpendicular to the axial direction is defined as W1, i.e., the width of the first flow guiding surface 412 in the circumferential direction, hereinafter abbreviated as the width of the first flow guiding surface 412. Wherein, W1 of the first flow guiding surface 412 is smaller than the radius of curvature R2 of the second turning surface 414, i.e. W1< R2.

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 guiding surface 412, i.e. r1+_r2+w1. And, the ratio of the radius of curvature R2 of the second angled flow surface 414 to the radius of curvature R1 of the first angled flow surface 413 is greater than or equal to 0.8, i.e., 0.8.ltoreq.R2/R1 < 1. The ratio of the width W1 of the first flow directing surface 412 to the radius of curvature R2 of the second angled flow surface 414 is less than or equal to 0.15, i.e., 0< W1/R2 < 0.15.

The larger ratio of R2/R1 (greater than or equal to 00.8, further greater than 0.85, 0.9) and the smaller ratio of W1/R2 (less than or equal to 00.15, further less than 0.12, 0.1) serves to compress the width W1 of the first flow-directing surface 412 as much as possible such that the width W1 of the first flow-directing surface 412 is much smaller than the radius of curvature R1 of the first corner surface 413 and the radius of curvature R2 of the second corner surface 414 (W1 ≪ R1, R2, i.e., the width W1 of the first flow-directing surface 412 is short), while the radius of curvature R2 of the second corner surface 414 is closer to the radius of curvature R1 of the first corner surface 413. Since the most upstream of the bleeding opening 411 is considered as the inlet end through which blood flows out through the bleeding opening 411, the most upstream of the bleeding opening 411 is occupied by as many smooth curved surfaces as possible, namely, the first and second corner surfaces 413 and 414, so that the shearing stress of the blood at the place is reduced, and the blood damage is reduced.

As shown in FIG. 6, R1 is equal to or greater than R2+W1, which is used to ensure that the end of the first turning flow surface 413 near the most upstream end (the upper end in the drawing) is located on or enters the side of the central axis P of the bleeding port 411 near the second turning flow surface 414, so as to ensure that the curvature radius R1 of the first turning flow surface 413 is always larger than the curvature radius R2 of the second turning flow surface 414.

Of course, R2+W1 should not be too much less than R1, which would otherwise cause too small a corner of the bleeding opening 411 at the second corner surface 414, which would be beneficial in preventing blood from flowing back, but would be detrimental to hemolysis. Therefore, in practice, R1 should be slightly larger than r2+w1. The research of the applicant shows that R1/(R2+W1) is not more than 1.2, namely R1/(R2+W1) is between 1 and 1.2, and further between 1 and 1.12, and the blood backflow prevention performance and the hemolysis prevention performance can be achieved.

In the present embodiment, the central axis P of the bleeding opening 411 is an axis passing through the midpoint of the second guide surface 415. As described below, the bleeding opening 411 has a symmetrical structure at the second axial end, so that the axis passing through the midpoint of the second guiding surface 415 is the central symmetry axis of the third and fourth turning surfaces 416 and 417, the first and second side surfaces 418 and 419, and can be regarded as the central axis P of the bleeding opening 411.

As shown in fig. 5 and 6, the contoured surface of the bleed orifice 411 further includes a second flow guide surface 415, a third corner surface 416, and a fourth corner surface 417 at the second end. The second guide surface 415 is a straight surface along the circumferential direction and is parallel to the first guide surface 412. The third and fourth turning surfaces 416 and 417 are arc-shaped and smoothly transition to both ends of the second guide surface 415 in the circumferential direction, respectively, and the third turning surface 416 is located upstream of the fourth turning surface 417 in the working direction O.

The first flow-guiding surface 412 is located upstream of the second flow-guiding surface 415 in the pumping direction of the blood, which is in the distal-to-proximal direction. The distance between projections of both ends of the second flow guiding surface 415 on a plane perpendicular to the axial direction is defined as W2, i.e., the width of the second flow guiding surface 415 in the circumferential direction, hereinafter simply referred to as the width of the second flow guiding surface 415.

The radius of curvature R3 of the third angled flow surface 416 is the same as the radius of curvature R4 of the fourth angled flow surface 417 such that the third angled flow surface 416 and the fourth angled flow surface 417 form an axially symmetric structure. The following relationship exists among W1, W2, R1, R2, R3 and R4: r1+w1+r2=r3+w2+r4. Wherein W1< W2, r3=r4 < R2 < R1 < W2. Further, W2 is 15-20 times of W1, 1.1-1.3 times of R1, 2-5 times of R3 or R4. That is, the width W2 of the second flow guiding surface 415 is the largest of the above values (except L1 and L2), in order to enlarge the opening area of the blood outlet 411 at the most downstream end as much as possible, deflect more blood toward the proximal end of the blood outlet 411 for drainage, and further increase the blood flow rate directed toward the ascending aorta AAO.

The contoured surface of bleed port 411 further includes a first side flow surface 418 and a second side flow surface 419 connecting the first and second ends, first side flow surface 418 connecting first corner flow surface 413 with third corner flow surface 416, and second side flow surface 419 connecting second corner flow surface 414 with fourth corner flow surface 417. Both the first side flow surface 418 and the second side flow surface 419 extend straight in the axial direction such that the straight side edge shape of the bleeding opening 411 of the present embodiment is different from the inclined or twisted side edge shape of the comparative example 1, and as described above, the straight side edge of the bleeding opening 411 is advantageous in reducing the difficulty of the manufacturing process. Likewise, this reduction in difficulty of the manufacturing process may be advantageous for the consistency of the final shape of the bleeding opening 411, such as for example, deburring or deburring, and thus for the haemolytic effect.

The length L1 of the first side flow surface 418 in the axial direction is smaller than the length L2 of the second side flow surface in the axial direction. The following relationship exists among R1, R2, R3, R4, L1 and L2: r1+l1+r3=r2+l2+r4. Since r3=r4, the difference between L1 and L2 is the difference between R1 and R2. The ratio relationship between R1 and R2, W1 has been described above, then where 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 described with reference to the ratio of R1 to R2 to W1, and will not be described herein.

As described below, second side flow face 419 and second flow guide face 415 serve as two main areas of blood outflow port 411. Thus, it is necessary to secure a large outflow area of the two main blood outflow areas. As with the above magnitude relation between the circumferential width W2 of the second flow guiding surface 415 and the radius of curvature R1 of the first turning surface 413, in the present embodiment, the length L2 of the second side flow surface 419 in the axial direction is also larger than the radius of curvature R1 of the first turning surface 413. As described above, the large radius of curvature R1 of the first corner flow surface 413 provides a large flow area, the ultimate purpose of which is to reduce shear stress in terms of lifting flow. That is, the increase in blood flow is still primarily accomplished or accomplished by second side flow surface 419 and second flow guide surface 415. Thus, the present embodiment is advantageous for ultimately increasing the blood flow rate by setting the dimensions L2 and W2 of the second side flow surface 419 and the second flow guide surface 415 for the blood outflow region to be larger than the radius of curvature R1 of the first turning flow surface 413.

As shown in fig. 3A to 3C, a connection point M (hereinafter, simply referred to as point M) of the first turning flow surface 413 and the first side flow surface 418 is substantially flush with a proximal end point N (hereinafter, simply referred to as point N) of the blade 302. The "substantially flush" is that the pointing point M has an offset distance D in the axial direction from the point N that is within a certain range. Wherein the offset is a bi-directional offset in the axial direction. It is possible that the point M is offset distally compared to the point N, as in the case shown in fig. 3C, where the point M is axially distally of the point N, the offset in this case being defined as a positive offset. It is also possible that the point M is shifted proximally compared to the point N, as in the case shown in fig. 3B, where the point M is axially proximal to the point N, the shift in this case being defined as a negative shift. When the range of the offset distance D is 0, as shown in fig. 3A, the point M is flush with the point N.

The purpose of designing the point M and the point N to be approximately flush in the axial direction is to fully exert the effect of the large flow area of the first turning surface 413 on improving the hydraulic effect. As the blood is completely removed from the pushing action of the blade 302 at point N and swirled out through the bleed orifice 411. Therefore, the blood is aligned with the point M at the point N, so that the blood pushed by the separation blade 302 and swirled can flow out completely through the first turning flow surface 413 with a large flow area, and the high-efficiency and high-flow outflow of the blood is ensured.

As shown in fig. 3B and 3C, whether point N is offset too far or too far proximally as compared to point M, the effect of the large flow area of the first angled flow surface 413 on increasing blood flow is impaired, thereby causing a decrease in blood flow. Further, a part of the blood pushed from the N-point separation blade 302 flows out through the second corner flow surface 414 or the flat second side flow surface 419 having a smaller radius of curvature, and this further causes a problem of increasing blood damage.

The applicant has found that there is a curved relationship between the pump head and the offset distance D as shown in fig. 19. In the graph, the horizontal axis represents the offset distance D in mm; the vertical axis is lift in mmHg. It should be noted that, similar to other flow field schematic conditions, the relationship is based on the same flow rate (3L/min). Thus, the higher the lift, the better the hydraulic properties.

As can be seen from fig. 19, the lift and the offset distance D are approximately in a normal distribution relationship. However, the normal distribution is not a standard normal distribution. That is, when the offset distance D is 0, that is, the point M is axially aligned with the point N, the head is not maximum, and the offset distance D corresponding to the maximum head is about 0.42mm. This result shows that: a degree of positive displacement is instead advantageous for increasing the pump head, which is not expected by the applicant.

The reasons for this are currently unknown, and the applicant hypothesizes that possible reasons are: the positive offset represents the proximal end point N of the vane 302 passing proximally beyond point M, and the side of the bleed orifice 411 opposite the point M is a flat second side flow surface 419, indicating that the proximal end point N of the vane 302 now falls within the scope of the second side flow surface 419. As described above, the blood accelerated by the blade 302 is in a mixed flow in the axial+radial direction, and the second side flow surface 419 is one of the regions where the blood flows out (the other main region is the second flow guide surface 415). Thus, the proximal end point N of the vane 302 falls within the region of the second side flow surface 419, which is the main outflow region of blood, which may be advantageous for increasing the lift.

Since the offset distance D corresponding to the maximum value of the lift is a fixed point value, and this fixed point value is not a special point value, this presents a great challenge for assembling the impeller 300 and the bleeding window 410. In general, the maximum value of 0.8 times is basically satisfied in the relationship conforming to the normal distribution. Therefore, under the guidance of the relation, when the value of the offset distance D is in the range of-0.13 mm to 0.96mm (namely-0.13 mm is less than or equal to D is less than or equal to 0.96 mm), the lift is more than 0.8 times of the maximum value. Further, when the value of the offset distance D is within the range of-0.05 mm to 0.89mm (namely-0.05 mm is less than or equal to D is less than or equal to 0.89 mm), the lift reaches more than 0.85 times of the maximum value.

Through the setting of the offset distance D, axial redundancy can be provided for the assembly of the impeller 300 and the bleeding window 410 on the premise that the flow rate or the lift of the pump is acceptable, so that the assembly difficulty of the pump is reduced, and the assembly efficiency is improved.

It is noted that the only effect of the offset distance D on the pump head or flow is described above. In fact, the positional relationship between impeller 300 and bleeding window 410 is systematic, and affects not only the pump head or flow rate, but also the flow rate and shear stress of the blood.

As shown in fig. 20 to 22, the flow field diagrams at the point M are respectively no offset, negative offset, and positive offset compared to the point N. As can be seen from fig. 21, when M is negatively offset from point N, the blood will generate a higher flow rate in the region (shown by the dashed box) near the surface of hub 301, and this region extends from the front section of hub 301 to the location of the bleeding opening 411. Therefore, the shear stress to which blood is subjected is much higher than that in the case shown in fig. 20. As can be seen from fig. 22, when M is shifted forward compared to the point N, the blood will generate a larger back flow area (shown by the left dotted box) in the middle of the blade 302, and a more distinct flow velocity drop area (shown by the right dotted box) near the bleeding outlet 411.

In contrast, as shown in fig. 20, when M is not shifted from the point N, the whole blood flow rate is uniform, no significant high flow rate and low flow rate occur in the region near the surface of the hub 301 and the bleeding port 411, and the volume of the backflow region is significantly reduced as compared with fig. 22.

Therefore, M is the best embodiment for comprehensively considering all performance indexes (lift or flow, uniformity of blood flow field, and shear stress) compared with the point N without offset, i.e. M is axially aligned with the point N, or offset distance D is 0. Furthermore, although M is also a fixed point value compared to the point N, which is offset-free, the corresponding offset distance D, this fixed point value is a special point value, i.e. M is axially aligned with the point N. Thus, this does not substantially adversely affect the assembly of the impeller 300 with the bleeding window 410.

It will be understood by those skilled in the art that the present invention is not limited to the details of the foregoing exemplary embodiments, but includes other specific forms of the same or similar structures that may be embodied without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. An asymmetric bleeding window of low shear stress, comprising: a hollow cylindrical body and a bleeding opening formed in the body; the bleeding window is used for accommodating an impeller for pumping blood, and the impeller can be driven to rotate along the working direction so as to pump the blood out of the bleeding outlet;

the method is characterized in that:

the stoma includes a contoured surface defining a contoured shape thereof, the contoured surface comprising:

the first turning flow surface and the second turning flow surface are axially positioned at the first end, and the first turning flow surface and the second turning flow surface are arc-shaped and are smoothly connected;

The first turning flow surface is located at the upstream of the second turning flow surface along the working direction, and the curvature radius of the first turning flow surface is larger than that of the second turning flow surface, so that the first turning flow surface and the second turning flow surface form an axial asymmetric structure.

2. The bleeding window of claim 1, wherein the contoured surface further comprises:

The first diversion surface is positioned at the first end and is connected with the first turning surface and the second turning surface;

the first diversion surface is a straight surface along the circumferential direction, the first diversion surface and the second diversion surface are respectively connected to two ends of the first diversion surface along the circumferential direction, and the first diversion surface and the second diversion surface are in smooth transition connection with the first diversion surface.

3. The bleeding window of claim 2, wherein the radius of curvature of the first inflection surface is equal to or slightly greater than the sum of the radius of curvature of the second inflection surface and the width of the first diversion surface in the circumferential direction; the upper limit of the ratio of R1/(R2+W1) is not more than 1.2, R1 is the curvature radius of the first turning surface, R2 is the curvature radius of the second turning surface, and W1 is the width of the first diversion surface along the circumferential direction.

4. The bleeding window of claim 2, wherein a ratio of a radius of curvature of the second crutch flow surface to a radius of curvature of the first crutch flow surface is greater than or equal to 0.8, and a ratio of a width of the first deflector flow surface in a circumferential direction to a radius of curvature of the second crutch flow surface is less than or equal to 0.15.

5. The bleeding window of claim 2, wherein the contoured surface further comprises:

The second guide surface is positioned at a second end opposite to the first end along the axial direction, and the second guide surface is a straight surface along the circumferential direction;

The third turning flow surface and the fourth turning flow surface are respectively connected to two ends of the second flow guiding surface along the circumferential direction and are arc-shaped, and the third turning flow surface is positioned at the upstream of the fourth turning flow surface along the working direction;

The third turning flow surface and the fourth turning flow surface are in smooth transition connection with the second flow guide surface, and the curvature radius of the third turning flow surface is the same as that of the fourth turning flow surface, so that the third turning flow surface and the fourth turning flow surface form an axially symmetrical structure.

6. The bleeding window of claim 5, wherein the fourth corner surface has a radius of curvature that is less than a radius of curvature of the second corner surface, the radius of curvature of the second corner surface being less than a circumferential width of the second deflector surface.

7. The bleeding window of claim 5, wherein the first flow-guiding surface is upstream of the second flow-guiding surface in the pumping direction of the blood, the first flow-guiding surface having a width in the circumferential direction that is smaller than the width of the second flow-guiding surface in the circumferential direction.

8. The bleeding window of claim 5, wherein the contoured surface of the bleeding opening further comprises: a first side flow surface connecting the first and third corner flow surfaces, a second side flow surface connecting the second and fourth corner flow surfaces; the first and second side flow surfaces each extend straight in an axial direction.

9. The bleeding window of claim 8, wherein the radius of curvature of the first inflection surface is less than the length of the second lateral flow surface in the axial direction and is also less than the circumferential width of the second flow guide surface.

10. The bleeding window of claim 8, wherein,

The impeller includes a hub and blades formed on the hub;

Wherein the first corner flow surface and the first side flow surface are axially offset from the proximal end point of the blade by a distance between-0.13 mm and 0.96 mm;

Wherein the connection point is offset distally positive and offset proximally negative compared to the proximal end point.

11. The bleeding window of claim 10, wherein the connection point is offset from the proximal end point in an axial direction by a distance between-0.05 mm and 0.89 mm.

12. The bleeding window of claim 10, wherein the connection point is axially aligned with the proximal end point, i.e., the offset distance is 0.

13. An interventional catheter pump comprising: a bleeding window according to any of claims 1 to 12.