Impeller for cardiac assist devices and cardiac assist devices

Abstract

This invention relates to an impeller for a cardiac assist device and the cardiac assist device itself. The impeller includes a hub and two blades with different structures, namely a first blade and a second blade. The axial deflection length of the first blade is greater than that of the second blade. By adjusting the induced distance and the shape of the frontal edge of the two blades, the frontal edge of the second blade can be placed entirely within a fully developed blood flow field, thereby reducing the blood shearing effect caused by collision. By adjusting the transition angle at each point on the frontal edge, the second blade can generate less flow field disturbance when it comes into contact with an incompletely developed blood flow field not driven by the blade, thereby reducing the shearing damage to the blood.

Description

Technical Field

[0001] This invention relates to the field of medical devices for cardiac surgery, and more particularly to an impeller for a cardiac assist device and a cardiac assist device. Background Technology

[0002] In recent years, mechanical circulatory support has become an important treatment for cardiovascular critical illnesses such as end-stage heart failure and cardiogenic shock, playing a significant role in improving hemodynamics. Through mechanical circulatory support, some of the heart's pumping function is replaced by the mechanical circulatory device, allowing the heart to rest effectively and facilitating the functional recovery of the failing heart. Mechanical circulatory support devices include intraaortic balloon counterpulsation, extracorporeal membrane oxygenation (ECMO), implantable left ventricular assist devices (LVAP), and interventional catheter pumps.

[0003] Compared to other mechanical circulatory support devices, interventional catheter pumps are characterized by minimal invasiveness and ease of implantation, and have good therapeutic effects for high-risk patients, such as those with severe cardiogenic shock. However, due to their small diameter (e.g., 6 mm), in order to provide the mechanical circulatory support flow rate required for clinical use (e.g., 1 L / min at 40–60 mmHg), the impeller of the catheter pump often needs to operate at a high speed (e.g., 10,000–60,000 rpm). Such a high speed causes a rapid change in the local flow field, which will exert extremely strong non-physiological shearing and collision effects on the blood, leading to complications such as hemolysis and even thrombosis, posing a great safety hazard to patients. Summary of the Invention

[0004] This invention discloses an impeller for a cardiac assist device and a cardiac assist device, aiming to solve the technical problems existing in the prior art.

[0005] The present invention adopts the following technical solution:

[0006] On one hand, the present invention provides an impeller for a cardiac assist device, including a hub and blades;

[0007] The blade has a pressure surface and a suction surface. The curve where the pressure surface and the suction surface intersect is the outer edge of the blade, which includes the frontal edge.

[0008] The blades are centrally symmetrically distributed on the hub. The blades include equal numbers of first blades and second blades that are spaced apart. All points on the front side of the first blade are at the same height, while the height of all points on the front side of the second blade decreases as the radius increases.

[0009] As a preferred technical solution, the impeller is used to install in the outflow chamber of the cardiac assist device. The outflow chamber includes several outflow windows, and in the installation position, the lowest point of the front side is higher than the highest point of the outflow window.

[0010] As a preferred technical solution, the axial deflection length of the first blade is greater than the axial deflection length of the second blade, and the frontal edge of the second blade is located below the frontal edge of the first blade.

[0011] As a preferred technical solution, the induced distance coincidence function is:

[0012] h ids =0.2~0.5×(h) bM -h W )

[0013] Among them, h bM The maximum distance between the first blade and the bottom surface of the hub is h, and the maximum distance between the second blade and the bottom surface of the hub is h. bS The difference between the two is h idc h idc h is the induced distance. W It is the distance from the bottom of the wheel hub to the highest point of the upper edge of the outlet window.

[0014] As a preferred technical solution, during the rotation of the impeller:

[0015] The angle between the normal vector at each point on the pressure surface and the velocity vector of the impeller at that point is ≤90°;

[0016] The angle between the normal vector at each point on the suction surface and the velocity vector of the impeller at that point is ≥90°.

[0017] As a preferred technical solution, the surface of the blade at the middle thickness is a blade-shaped surface, which is continuous at each point on the blade-shaped surface and is first-order differentiable in each direction.

[0018] As a preferred technical solution, the plane formed by a point on the front edge and the axis of the hub is the reference plane, and the angle between the front edge at a certain point and the reference plane is the transition angle. The transition angle decreases or remains unchanged as the radius increases, and the transition angle is greater than 0 and less than or equal to π / 2.

[0019] As a preferred technical solution, on the frontal side of the second blade, the point located at the smaller radius has a larger transition angle, and the point located at the larger radius has a smaller transition angle.

[0020] As a preferred technical solution, the overlap between the first blade and the second blade... Synchronous function:

[0021]

[0022] Where, θ bM θ represents the range of azimuth angles spanned by the outer edge of the first blade. bSθ represents the range of azimuth angles spanned by the outer edge of the second blade, with the zero point of the azimuth angle located at the highest point on the outer edge of any of the first blades; t The angle spanned from the beginning of the outer edge of the first blade to the end of the outer edge of the second blade.

[0023] On the other hand, this application provides a cardiac assist device, including an impeller as described in any of the preceding claims.

[0024] The technical solution adopted in this invention can achieve the following beneficial effects:

[0025] This invention mainly provides an impeller for a cardiac assist device and a cardiac assist device equipped with the impeller. The impeller has two blades with different structures, including a first blade and a second blade. The axial deflection length of the first blade is greater than that of the second blade. By adjusting the induction distance and the shape of the frontal edge of the two blades, the frontal edge of the second blade can be placed entirely within a fully developed blood flow field, thereby reducing the blood shearing effect caused by collision. By adjusting the transition angle at each point on the frontal edge, the second blade can generate less flow field disturbance when it comes into contact with an incompletely developed blood flow field not driven by the blade, thereby reducing the shearing damage to the blood.

[0026] Applying the impeller of this invention to a cardiac assist device can effectively reduce the shearing damage to blood in the impeller region flow field, avoid complications such as hemolysis or thrombosis, and eliminate potential safety hazards as much as possible. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, which constitute a part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention.

[0028] In the attached diagram:

[0029] Figure 1 This is a schematic diagram of the structure of a cardiac assist device in a preferred embodiment of Embodiments 1 and 2 of the present invention;

[0030] Figure 2 This is a schematic diagram of the outflow chamber in a preferred embodiment of the present invention, as disclosed in Embodiment 1.

[0031] Figure 3 This is a schematic diagram of the impeller structure in a preferred embodiment of the present invention as disclosed in Embodiment 1;

[0032] Figure 4 for Figure 3 Top view;

[0033] Figure 5 for Figure 3 A three-dimensional image;

[0034] Figure 6 This is a schematic diagram showing the features of an impeller in a preferred embodiment of the present invention as disclosed in Embodiment 1;

[0035] Figure 7 This is a schematic diagram showing the features of the impeller top view in a preferred embodiment of the present invention, as disclosed in Embodiment 1 of the present invention.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1. Pig tail tube, 2. Inlet chamber, 3. Insertion tube, 31. Developing ring, 4. Outlet chamber, 41. Outlet window, 5. Impeller, 51. Hub, 511. Hub bottom surface, 52. Blade, 521. First blade, 522. Second blade, 5221. Working part, 5222. Transition part, 5222. Pressure surface, 54. Suction surface, 55. Airfoil surface, 56. Outer edge of airfoil, 561. Frontal edge, 5611. Drive motor, 6. Cable, 7. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0039] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. Furthermore, in the description of this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0040] In the field of interventional medical device technology, the direction closer to the operator is generally defined as proximal, and the direction farther from the operator is defined as distal. The direction of the central axis of objects such as cylinders and tubes is defined as axial. Radial refers to the direction passing through the central axis in the radial plane, for example, a straight line along a diameter or radius, or a straight line perpendicular to the central axis.

[0041] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0042] Example 1

[0043] To address the problems existing in the prior art, this embodiment provides an impeller for a cardiac assist device. In a preferred embodiment, the cardiac assist device refers to a miniature axial flow pump that can be placed in the left or right ventricle; such as Figure 1 Taking the ventricular assist device placed in the left ventricle as an example, the miniature axial flow pump includes, from proximal to distal, components such as cable 7, drive motor 6, impeller 5, outflow chamber 4, cannula 3, inflow chamber 2, and pigtail tube 1. The inflow chamber 2 has an inflow window for blood to flow in, and the outflow chamber 4 has an outflow window 41 for blood to flow out. The cannula 3 is also equipped with a contrast ring 31 for determining the position under the imaging system.

[0044] In a preferred embodiment, taking left ventricular assist as an example, when applying the cardiac assist device, it is implanted between the left ventricle and the aorta through an arterial pathway. The inflow chamber 2 of the cardiac assist device is located in the left ventricle. When the drive motor 6 runs, the impeller 5 rotates and does work, which can draw blood from the left ventricle into the cardiac assist device. The blood in the left ventricle is drawn in through the inflow chamber 2, passes through the cannula 3 and the impeller 5 in the outflow chamber 4, and is finally discharged into the aorta through the outflow window 41 to maintain peripheral circulation.

[0045] like Figure 2 In a preferred embodiment, the outflow chamber 4 is cylindrical and has a plurality of outflow windows 41 distributed around its circumference. Each outflow window 41 is configured as a rectangular window of the same size. The impeller 5 is axially inserted into the outflow chamber 4, and the proximal end of the impeller 5 is connected to the output shaft of the drive motor 6. The drive motor 6 drives the impeller 5 to rotate in the outflow chamber 4 and pump blood.

[0046] like Figure 3-5 ,in, Figure 3 For the mounting position of the impeller 5, preferably, the impeller 5 includes a hub 51 and blades 52, wherein the hub 51 is configured as a rotating body structure, and its bottom surface is a plane. The output shaft of the drive motor 6 passes through and is fixed by the bottom surface 511 of the hub. The number of blades 52 is even, preferably 4, and they are centrally symmetrically distributed on the outer periphery of the hub 51. Each blade 52 consists of two surfaces, including a pressure surface 54 and a suction surface 55. The pressure surface 54 is the blade surface facing the blood flow direction, and the suction surface 55 is the blade surface facing away from the blood flow direction.

[0047] Specifically, when blood enters the impeller 5, it flows over the suction surface 55 of the blade 52. Due to the shape of the suction surface 55, the blood forms a low-pressure area on the blade 52, thereby generating a suction effect that draws the blood into the center of the blade 52. As the impeller 5 rotates, the blood is forced to flow over the pressure surface 54 of the blade 52. Due to the shape of the pressure surface 54, the blood forms a high-pressure area on the blade 52, thereby generating a thrust effect that pushes the blood toward the outlet of the impeller 5.

[0048] Preferably, the angle between the normal vector of each point on the pressure surface 54 and the velocity vector of the impeller 5 at that point is ≤90°, and the angle between the normal vector of each point on the suction surface 55 and the velocity vector of the impeller 5 at that point is ≥90°, so as to minimize the turbulence loss on the impeller 5 surface and reduce the hydrodynamic noise of the impeller 5, thereby improving the efficiency and performance of the impeller 5.

[0049] like Figure 7 Preferably, the curve where the pressure surface 54 and the suction surface 55 intersect is defined as the outer edge line 561 of the blade. The outer edge line 561 of the blade includes the front edge 5611, the side edge, and the outlet edge. Preferably, the front edge 5611 is defined as the edge where the blade 52 first cuts into and acts on the fluid, the outlet edge is the edge where the fluid leaves the area of ​​the blade 52 after the blade 52 has done work, and the side edge is the edge where the blade 52 is adjacent to the hub 51.

[0050] In a preferred embodiment, the outer edge line 561 of the blade is approximately arc-shaped in the top view direction, and the radius of curvature of the arc-shaped portion formed by the projection of the outer edge line 561 of the blade in the top view direction is defined as R. b The radius of curvature R of the first blade 521 and the second blade 522 b Similarly, the frontal edge 5611 is located within the arc-shaped projection area. The portion of the second blade 522 within the range from the highest point to the lowest point of the frontal edge 5611 is called the transition section 5222, and the rest is the working section 5221.

[0051] In a preferred embodiment, the blade 52 includes a first blade 521 and a second blade 522, which are the same in number and spaced apart. The second blade 522 is located on one side of the pressure surface 54 of the first blade 521. The axial deflection length of the first blade 521 is greater than the axial deflection length of the second blade 522. The deflection lengths of the two blades are the lengths by which the blade 52 extends upward from the bottom surface 511 of the hub along the side surface of the hub 51, corresponding to the side lengths of the first blade 521 and the second blade 522. That is, the second blade 522 has a smaller size than the first blade 521.

[0052] In a preferred embodiment, when in the installation position, the lowest point of the front edge 5611 is higher than the highest point of the outlet window 41, so that the blades 52 of the outlet window 41 can do sufficient work to improve the performance and efficiency of the impeller 5.

[0053] In a preferred embodiment, all points on the front edge 5611 of the first blade 521 are at the same height, and the height of each point on the front edge 5611 of the second blade 522 decreases as the radius increases. That is, the front edge 5611 of the first blade 521 is perpendicular to the axis of the hub 51. When the axis of the hub 51 is defined as vertical, the front edge 5611 of the first blade 521 is a curve on a horizontal plane, while the front edge 5611 of the second blade 522 is a curve inclined downward. At this time, the blade 52 area near the front edge 5611 of the second blade 522 is in the blood flow field driven by the first blade 521, thereby reducing the impact of blood on the second blade 522 and reducing the shear damage caused by the impact to the blood.

[0054] Preferably, near the upstream edge 5611 of the first blade 521, the process of the blood flow field gradually developing fully under the influence of the first blade 521 requires a certain amount of space. The fully developed blood flow field should be located below the upstream edge 5611 of the first blade 521. Therefore, the upstream edge 5611 of the second blade 522 is located below the upstream edge 5611 of the first blade 521. By adjusting the induction distance, the upstream edge 5611 of the second blade 522 is placed entirely within the fully developed blood flow field to regulate the velocity distribution of blood as it passes through the impeller 5, thereby reducing the blood shearing effect caused by collision. Specifically, the induction distance is the distance between the outer edge lines 561 of the first blade 521 and the second blade 522 in the height direction at the beginning.

[0055] Preferably, at each point on the outer edge line 561 of the blade, the maximum distance between the first blade 521 and the bottom surface 511 of the hub is defined as h. bM The maximum distance between the second blade 522 and the bottom surface 511 of the hub is defined as h. bS The induced distance is defined as h. idc The distance from the bottom surface 511 of the wheel hub to the highest point of the upper edge of the outlet window 41 is defined as h. W Therefore, the induced distance h idc =h bM -h bS Preferably, the induction distance h idc Synchronous function:

[0056] h idc =0.2~0.5×(h) bM -h W )

[0057] For blood with a circumferential velocity of zero to reach the same angular velocity as the first blade 521, it needs a certain development time. Setting an induction distance allows the frontal edge 5611 of the second blade 522 to be in a flow field environment that is fully driven by the first blade 521, thereby reducing the collision caused by the inconsistency between the blood flow and the rotation speed of the blade 52, and thus reducing the shear force near the frontal edge 5611 of the second blade 522.

[0058] In a preferred embodiment, a height h direction is established with the central symmetry axis of the hub 51 as the height h direction and the center of the bottom surface 511 of the hub as the origin of the height direction, as shown below. Figure 6 In the cylindrical coordinate system shown, the direction from the bottom surface 511 of the hub to the blade 52 is the positive height direction. Among all points on the outer edge line 561 of the blade, the maximum distance from the bottom surface 511 of the hub is h. b The minimum value is h0, and the blade height is 52. t =h b -h0, defining the heights of the first blade 521 and the second blade 522 as h respectively. tM h tS .

[0059] like Figure 7 As shown, in a preferred embodiment, the azimuth zero point is located at the highest point of the blade outer edge line 561 of any blade in the first blade 521, with the opposite direction of the impeller 5 rotation direction as the positive direction of the angle. It should also be noted that the azimuth zero point is the beginning of the blade outer edge line 561, and the lowest point of the height is the end of the blade outer edge line 561.

[0060] In a preferred embodiment, the azimuth angle range spanned by the outer edge line 561 of the blade is defined as θ. b The azimuth angle range spanned by the outer edge line 561 of the first blade 521 and the second blade 522 is θ respectively. bM and θ bS The angle spanned from the outer edge line 561 of the first blade 521 to the outer edge line 561 of the second blade 522 is defined as θ. t .

[0061] Preferably, the surface of the blade 52 at the middle thickness is the blade-shaped surface 56, which is continuous at each point on the blade-shaped surface 56 and is first-order differentiable in each direction. At this time, the blade 52 is smooth and has no protrusions or depressions.

[0062] In a preferred embodiment, the points on the upstream edge 5611 are continuous and first-order smooth, and the transition angle θ of each point is [missing information]. tranDefined as the angle between the frontal edge 5611 at a certain point and the reference plane, where the reference plane is the plane formed by the point and the axis of the hub 51.

[0063] Preferably, 0≤θ tran ≤π / 2, and the transition angle θ tran It decreases or remains constant as the radius increases. By setting an appropriate transition angle θ tran This allows the second blade 522 to generate less flow field disturbance when it comes into contact with the incompletely developed blood flow field that is not driven by the blade 52, thereby reducing the shear damage to the blood. Furthermore, a smaller transition angle θ... tran The smaller the disturbance to the flow field, the better; however, a smaller transition angle θ is used overall. tran This will cause the transition section 5222 of the second blade 522 to be too long, reducing the work capacity of this part of the blade 52.

[0064] In a preferred embodiment, on the flow-facing edge 5611 of the second blade 522, preferably, the blade 52 located at a smaller radius position has a smaller linear velocity, so a larger transition angle (approaching π / 2) can be selected, allowing the blade 52 to transition to the working part 5221 more quickly within a shorter height range; the part near the outer edge has a larger linear velocity and is more likely to have a stronger collision with the blood, so a smaller transition angle (approaching 0) should be selected for this part to minimize the shearing and damaging effect on the blood.

[0065] Preferably, the overlap between the first blade 521 and the second blade 522 is... Synchronous function:

[0066]

[0067] Overlap This mainly determines where the frontal edge 5611 of the second blade 522 begins relative to the first blade 521, and the degree of overlap. The higher the flow rate, the closer the frontal edge 5611 of the second blade 522 will be to the first blade 521, resulting in a more fully developed flow field. This reduces the shear force generated by the collision between the frontal edge 5611 portion of the blade 52 and the blood, but may simultaneously impede blood flow in the first blade 521 portion. Preferably,

[0068] In this embodiment, by redesigning the shape of the impeller 5, the shearing damage to the blood in the flow field of the impeller 5 region is effectively reduced.

[0069] Example 2

[0070] refer to Figure 1This embodiment provides a cardiac assist device, including the impeller 5 as described in Embodiment 1, and the features already included in the above embodiments are naturally inherited in this embodiment.

[0071] In a preferred embodiment, the cardiac assist device is a miniature axial flow pump. Preferably, the cardiac assist system includes a cable 7, a drive motor 6, an impeller 5, an outflow chamber 4, a cannula 3, a contrast ring 31, an inflow chamber 2, and a pigtail tube 1. The cable 7 is connected to the proximal end of the drive motor 6, and the impeller 5 is connected to the distal end of the drive motor 6 and is disposed in the outflow chamber 4. The impeller 5 is driven by the drive motor 6 to rotate and perform work, replacing the heart's pumping function. Taking left ventricular assist as an example, the portion from the contrast ring 31 to the pigtail tube 1 is located in the patient's left ventricle, and the portion from the contrast ring 31 to the cable 7 is located in the patient's aorta. The contrast ring 31 is located near the aortic valve. When the impeller 5 rotates, blood from the left ventricle is drawn from the inflow chamber 2, passes through the cannula 3 and the impeller 5 in the outflow chamber 4, and is finally discharged into the aorta through the outflow window 41.

[0072] Those skilled in the art should understand that, given that different manufacturers have different designs for the structure of the micro axial flow pump, the drive motor 6, the cannula 3, the impeller 5, the inflow chamber 2, the outflow chamber 4, and other components can be any design from the prior art. The inventive point of this embodiment is to apply the impeller 5 in the above embodiment 1 to the cardiac assist device to reduce the damaging effect on the blood when the impeller 5 rotates and reduce complications. Therefore, other specific structures of the micro axial flow pump will not be described in detail.

[0073] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. An impeller for a cardiac assist device, characterized in that, Including the hub and blades; The blade has a pressure surface and a suction surface, and the curve where the pressure surface and the suction surface intersect is the outer edge line of the blade, which includes the frontal edge. The blades are centrally symmetrically distributed on the hub. The blades include an equal number of first blades and second blades spaced apart. Each point on the frontal side of the first blade is at the same axial height. The axial height of each point on the frontal side of the second blade decreases as the radius increases. This makes the area near the frontal side of the second blade in the blood flow field driven by the first blade, thereby reducing the impact of blood on the second blade and reducing the shear damage caused by the impact on the blood.

2. The impeller according to claim 1, characterized in that, The impeller is used to install in the outflow chamber of the cardiac assist device, the outflow chamber including a plurality of outflow windows, wherein, in the installation position, the lowest point of the frontal side is higher than the highest point of the outflow window in axial height.

3. The impeller according to claim 2, characterized in that, Induced distance coincidence function: in, The maximum distance between the first blade and the bottom surface of the hub is [value missing], and the maximum distance between the second blade and the bottom surface of the hub is [value missing]. The difference between the two is , The induced distance, The distance is the distance from the bottom surface of the hub to the highest point of the upper edge of the outlet window.

4. The impeller according to claim 1, characterized in that, The axial deflection length of the first blade is greater than that of the second blade; The frontal edge of the second blade is located below the frontal edge of the first blade.

5. The impeller according to claim 1, characterized in that, During the rotation of the impeller: The angle between the normal vector at each point on the pressure surface and the velocity vector of the impeller at that point. 90°; The angle between the normal vector at each point on the suction surface and the velocity vector of the impeller at that point. 90°.

6. The impeller according to claim 1, characterized in that, The surface of the blade at its intermediate thickness is a blade-shaped surface, and all points on the blade-shaped surface are continuous and first-order differentiable in all directions.

7. The impeller according to claim 1, characterized in that, The plane formed by a point on the front edge and the axis of the wheel hub is a reference plane. The angle between the front edge at a certain point and the reference plane is a transition angle. The transition angle decreases or remains constant as the radius increases. The transition angle is greater than 0 and less than or equal to... .

8. The impeller according to claim 7, characterized in that, On the frontal edge of the second blade, the point located at the smaller radius has a larger transition angle, and the point located at the larger radius has a smaller transition angle.

9. The impeller according to claim 1, characterized in that, The overlap between the first blade and the second blade Synchronous function: ， in, The size of the azimuth angle range spanned by the outer edge line of the first blade. The range of azimuth angles spanned by the outer edge line of the second blade, with the zero point of the azimuth angle at the highest point of the outer edge line of any of the first blades. The angle spanned from the beginning of the outer edge line of the first blade to the end of the outer edge line of the second blade.

10. A cardiac assist device, characterized in that, Includes the impeller as described in any one of claims 1-9.

Images