Foldable impeller and blood pump thereof

Abstract

The present application aims to provide a foldable impeller with good resilience and folding effect and a blood pump thereof, comprising a hub and blades arranged in the circumferential direction of the hub, wherein the blades comprise foldable supports and a film covering the periphery of the foldable supports, and the foldable supports fold in the radial direction and fold the film when the blades are subjected to a constraint force. When the collapsible shell of the blood pump is constrained to shrink by a sheath, the foldable supports are folded under pressure, and the optimal folding effect is that adjacent support pieces completely fit together. When the blood pump enters a preset working position, the blood pump will be separated from the sheath, the collapsible shell of the blood pump automatically restores to the original size, and the foldable supports also return to the original shape and size due to resilience. The unfolded size of the impeller can reach 6 mm, and the size after shrinking is 2.2 mm, so that the blood pump can provide sufficient flow and maintain good hemolysis performance.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, specifically to a foldable impeller and its blood pump. Background Technology

[0002] Various heart diseases, such as heart failure, myocardial infarction, and myocardial injury, can impair the pumping function of the ventricles. Currently, the primary treatment for these patients involves ventricular assist devices (VADs), which not only help the heart pump blood, reducing the burden on the myocardium and aiding in its recovery, but also prevent damage to vital organs such as the brain and kidneys due to ischemia when the heart's pumping function declines or even disappears.

[0003] For interventional cardiac blood pumps, there are three ideal performance requirements: longer clinical support time, smaller size, and better hemodynamics. However, it is often difficult to balance these three points simultaneously. Smaller size makes it difficult to achieve greater flow support, and longer support time brings a greater risk of hemolytic events. Therefore, in the latest research direction of blood pumps, foldable blood pumps have become the most popular direction. As a key component, the shape and folding method of the foldable impeller are crucial to hemolytic performance and pumping volume. Summary of the Invention

[0004] One of the objectives of this invention is to provide a foldable impeller with good resilience and folding effect.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a foldable impeller, including a hub and blades arranged in the circumferential direction thereon, wherein the blades include a foldable support and a film covering the outer periphery of the foldable support, and when the blades are subject to a constraint force, the foldable support folds radially and the film is folded together.

[0006] The foldable bracket has a folding fan structure. The whole structure is formed by cutting an alloy plate to form a structure with several support plates connected together. Each support plate in the folding structure has the same curvature as the outer diameter of the hub. The angle between adjacent support plates can be adjusted according to the width of the support plate and the design size of the blade.

[0007] The innermost edge of the foldable bracket has the same curvature as the wheel hub, and the two are welded together.

[0008] The foldable bracket is made of shape memory alloy, which is selected from one of nickel-titanium alloy, titanium-nickel-copper alloy, titanium-nickel-iron alloy, and titanium-nickel-chromium alloy. The coating is made of TPU material with a hardness of 40D to 70D.

[0009] The angle between adjacent support plates is 30° to 80°.

[0010] A relatively thick section is reserved at the corner of the foldable bracket to connect the film. The film is covered on the outer periphery of the foldable bracket by hot melt welding, or the film is covered on the outer periphery of the foldable bracket and the wheel hub by hot melt welding.

[0011] The film has a crease in the middle of the adjacent support piece. When the blade is under constraint, the film will fold along the crease.

[0012] The blade includes a working surface, and the contour line of the working surface includes an outer edge profile away from the hub. The endpoint of the outer edge profile near the inlet end is the profile start point, and the endpoint of the outer edge profile near the outlet end is the profile end point. The angle between the axial plane where the profile start point is located and the axial plane where the profile end point is located is the blade deflection angle θ, and the blade deflection angle θ is 90° to 180°.

[0013] The angle between the tangent of the impeller arc at the point where the blade extends from the hub and the tangent of the hub is the blade inflow angle α, which is 90° to 180°.

[0014] Another objective of this invention is to provide a foldable impeller with good resilience and folding effect.

[0015] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a blood pump, comprising a catheter and a foldable impeller disposed within the catheter.

[0016] In the above design, when the retractable outer shell of the blood pump is constricted and contracted by the sheath, the foldable support folds under pressure, with the optimal folding effect being complete fit between adjacent support plates. When the blood pump enters the preset working position, it disengages from the sheath, the retractable outer shell automatically returns to its initial size, and the foldable support also returns to its original shape and size due to its resilience. The impeller's expanded size reaches 6mm, and its contracted size is 2.2mm, maintaining good hemolytic performance while providing sufficient blood flow. Attached Figure Description

[0017] Figure 1 This is a three-dimensional view of the impeller;

[0018] Figure 2 This is the front view of the impeller in its unfolded state;

[0019] Figure 3 This is a front view of the impeller in its folded state;

[0020] Figure 4 This is a top view of the impeller in its unfolded state;

[0021] Figure 5 This is a top view of the impeller in its folded state;

[0022] Figure 6 for Figure 2 Cross-sectional view;

[0023] Figure 7 for Figure 3 Cross-sectional view;

[0024] Figure 8 The simulation diagram shows the wall shear stress when the blade inflow angle α is 140° and the blade deflection angle θ is 180°.

[0025] Figure 9 The simulation diagram shows the wall pressure when the blade inflow angle α is 140° and the blade deflection angle θ is 180°.

[0026] Figure 10 The simulation diagram of the velocity streamline is shown when the blade inflow angle α is 140° and the blade deflection angle θ is 180°.

[0027] Figure 11 The simulation results are shown at various time points corresponding to the start of timing when blood flows through the inlet with a blade inflow angle α of 140° and a blade deflection angle θ of 180°. Detailed Implementation

[0028] The hydraulic performance and hemolytic performance of a blood pump are closely related to the structure of the impeller.

[0029] Hydraulic performance refers to the flow rate and head that a blood pump can achieve under target volume and operating conditions.

[0030] To enable blood pumps to meet the blood circulation needs of different patients, they can be classified into various types based on their blood output per minute, such as 2.5L / min, 3.5L / min, and 5.0L / min blood pumps.

[0031] Hemolysis refers to the rupture of red blood cells, causing the hemoglobin within them to leak out and dissolve in the blood. Hemolysis leads to changes in the morphology and biochemical properties of red blood cells, shortens their lifespan, and can even result in complete rupture, thereby reducing their ability to transport oxygen to tissues and organs. Furthermore, hemolysis increases the concentration of free hemoglobin in the plasma; the excess free hemoglobin needs to be excreted through the kidneys, potentially leading to kidney damage and multiple organ failure.

[0032] Therefore, preventing hemolysis of the pumped blood is crucial when performing blood pumping on medical patients. Hemolysis during pumping can endanger the patient's life.

[0033] To ensure the safe use of blood pumps, hemolytic performance needs to be considered. Hemolytic performance refers to the probability that hemolysis will occur due to blood cell breakage and damage after the blood flows through the blood pump.

[0034] To meet the requirements of hydraulic performance and hemolytic performance, some related technologies employ micro axial flow structures for their impellers.

[0035] The applicant's research found that due to the special nature of blood pump usage scenarios, there are still two key technical challenges in the design and manufacture of the impeller: First, in order to reduce the impact of implantation on normal human physiology, the outer diameter of the impeller is limited to within 7mm, which is suitable for passing through blood vessels. This severely limits the volume of the impeller and the blades on the impeller, making it difficult for the impeller to achieve the required hydraulic performance. Second, in order to meet the pressure requirements of human blood circulation, it is necessary to increase the impeller speed to improve the pumping performance. However, the high-speed rotation of the impeller will increase the shear stress of the blood flow field, leading to blood cell breakage and mechanical hemolysis.

[0036] Therefore, the structure of a blood pump impeller needs to balance hydraulic performance and hemolytic performance. The main considerations for hydraulic performance are the output flow rate and the pressure difference between the pump inlet and outlet, while the main considerations for hemolytic performance are the shear stress on the blood during pumping and the smoothness of blood flow. By optimizing and improving the impeller structure, hydraulic performance can be enhanced while reducing blood damage caused by hemolysis.

[0037] For the reasons mentioned above, this application provides a foldable impeller, including a hub 10 and blades 20 arranged circumferentially thereon. Each blade 20 includes a foldable support 21 and a membrane 22 covering the outer periphery of the foldable support 21. When the blades 20 are under constraint, the foldable support 21 folds radially and the membrane 22 is retracted. When the retractable housing of the blood pump is constricted by the sheath, the foldable support 21 folds under pressure, with the optimal folding effect being complete contact between adjacent support plates 211. When the blood pump enters a preset working position, the blood pump disengages from the sheath, the retractable housing automatically returns to its initial size, and the foldable support 21 also returns to its original shape and size due to its resilience. The impeller's unfolded size can reach 6mm, and its retracted size is 2.2mm, maintaining good hemolytic performance while providing sufficient blood flow for pumping.

[0038] The foldable bracket 21 has a folding structure, and the whole is formed by cutting an alloy plate to form a structure with several support pieces 211 connected together. Each support piece 211 in the folding structure has the same curvature as the outer diameter of the hub 10. The angle between adjacent support pieces 211 is adjustable according to the width of the support piece 211 and the design size of the blade 20.

[0039] The innermost edge contour of the foldable bracket 21 has the same curvature as the hub 10 and the two are welded together. The same curvature of the two can provide the maximum welding area, so that the connection strength between the two meets the usage requirements.

[0040] Shape memory alloys are materials composed of two or more metallic elements that exhibit shape memory effects through thermoelasticity and martensitic phase transformation and its inverse. The foldable bracket 21 is made of a shape memory alloy, selected from nickel-titanium alloy, titanium-nickel-copper alloy, titanium-nickel-iron alloy, and titanium-nickel-chromium alloy. Because the coating 22 needs to resist the resistance to blood flow caused by the high-speed rotation of the impeller, a flexible membrane cannot be used; therefore, the coating 22 is made of TPU material with a hardness of 40D to 70D. The hub 10 can be made of nickel-titanium alloy, stainless steel, or other metallic materials, or hard plastic materials such as PEEK and hard TPU. Different hub wall thicknesses can be designed according to different materials and product requirements. The outer diameter of the hub 10 can be 1.0mm to 1.4mm, and the inner diameter can be 0.6mm to 1.0mm.

[0041] As a preferred embodiment of the present invention, the angle between adjacent support pieces 211 is 30° to 80°.

[0042] A relatively thick section is reserved at the corner of the foldable bracket 21 to connect to the film 22. The film 22 is covered on the outer periphery of the foldable bracket 21 by hot-melt welding, or the film 22 is covered on the outer periphery of the foldable bracket 21 and the hub 10 by hot-melt welding. The film 22 has a crease 221 reserved in the middle of the adjacent support piece 211. When the blade 20 is under constraint, the film 22 is folded along the crease 221, which facilitates the folding and compression of the film 22 and the foldable bracket 21 to achieve the best folding effect.

[0043] The blade 20 includes an action surface 23. The contour line of the action surface 23 includes an outer edge profile away from the hub 10. The endpoint of the outer edge profile near the inlet end is the profile start point, and the endpoint of the outer edge profile near the outlet end is the profile end point. The angle between the axial plane where the profile start point is located and the axial plane where the profile end point is located is the blade deflection angle θ. The blade deflection angle θ is 90° to 180°. The blade deflection angle θ can be more intuitively understood as the angle formed by the line connecting the profile start point and the axis of the hub 10, and the line connecting the profile end point and the axis of the hub 10, in the top view projection of the impeller. The size of the blade deflection angle θ reflects the length of each blade 20 extending circumferentially on the hub 10. If the blade deflection angle θ is too small, the flow rate may not meet the requirements under high pressure; if the blade deflection angle θ is too large, the flow rate may be too small under low pressure.

[0044] The angle between the tangent of the impeller arc at the position where the blade 20 extends from the hub 10 and the tangent of the hub 10 is the blade inflow angle α, which is 90° to 180°.

[0045] In the impeller design, we selected an inflow angle of 140°, a blade deflection angle of 180°, and a blade outer diameter of 6mm for the impeller. Using ANSYS CFX fluid analysis simulation software, we set a flow rate of 4L / min to simulate the flow of blood through the blood pump, and performed numerical analysis of the flow field. When the residual curve was within 10... -6 Under controlled convergence, contour maps of the pressure, velocity, and shear stress fields within the flow field can be obtained, and the hemolysis rate can be calculated based on the hemolysis formula obtained experimentally by GIERSIEPEN et al. This model indicates that the degree of hemolysis is related to the flow field shear stress and the exposure time of red blood cells under shear stress in a power function:

[0046] ;

[0047] In the formula: Total mass of hemoglobin; This refers to the amount of free hemoglobin; denoted as the shear stress scalar in the flow field; t is the exposure time of the red blood cells. To allow for margin in the hemolysis calculation, the maximum shear stress is used in this application for calculation.

[0048] The wall shear stress cloud diagram shows that the highest shear stress (551.4 Pa) is found at the outer edge of the blades on the impeller inlet side. The shear stress on the blade surface decreases uniformly from the edge to the hub, and is below 366 Pa, indicating that most areas of the blades experience low shear stress. The pressure cloud diagram shows that the overall pressure distribution of the impeller follows the same pattern as the wall shear stress, with a uniform pressure gradient that will not cause destructive damage to red blood cells. The plasma velocity streamline diagram inside the blood pump shows the instantaneous velocity of plasma at various points within the pump. The overall velocity difference is small, while the velocity is higher in the gap between the impeller and the pump cover. This is because the blood cell volume concentration is higher at the impeller edge, and the interaction between blood cells and plasma increases the plasma velocity. The plasma travel time streamline diagram inside the blood pump shows that the longest time for plasma to travel from the inlet to the outlet is 2.71 × 10⁻⁶. -3 s, and the overall movement is uniform.

[0049] Based on the maximum wall shear stress and the longest time, we calculated the maximum hemolysis index to be 0.0148, indicating good hemolysis performance.

[0050] A blood pump includes a conduit and a foldable impeller disposed within the conduit. The blood pump of the above embodiment relies on the corresponding impeller in any of the foregoing embodiments to pump blood and has the beneficial effects of the corresponding impeller embodiments, which will not be described in detail here.

[0051] It should be noted that the above description describes some embodiments of this application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in a different order than that shown in the above embodiments and still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A foldable impeller, comprising a hub (10) and blades (20) arranged circumferentially thereon, characterized in that: The blade (20) includes a foldable bracket (21) and a film (22) covering the outer periphery of the foldable bracket (21). When the blade (20) is under constraint, the foldable bracket (21) folds radially and the film (22) is folded together. The foldable bracket (21) has a fan-shaped folding structure. The whole structure is formed by cutting an alloy plate and connecting several support pieces (211). Each support piece (211) in the folding structure has the same arc as the outer diameter of the hub (10). The angle between adjacent support pieces (211) is adjustable according to the width of the support piece (211) and the design size of the blade (20).

2. The foldable impeller according to claim 1, characterized in that: The innermost edge contour of the foldable bracket (21) has the same curvature as the hub (10) and the two are welded together.

3. The foldable impeller according to claim 1, characterized in that: The foldable bracket (21) is made of shape memory alloy, which is selected from one of nickel-titanium alloy, titanium-nickel-copper alloy, titanium-nickel-iron alloy, and titanium-nickel-chromium alloy. The coating (22) is made of TPU material with a hardness of 40D to 70D.

4. The foldable impeller according to claim 1, characterized in that: The angle between adjacent support plates (211) is 30° to 80°.

5. The foldable impeller according to claim 1, characterized in that: A relatively thick part is reserved at the corner of the foldable bracket (21) to connect the film (22). The film (22) is covered on the outer periphery of the foldable bracket (21) by hot melt welding, or the film (22) is covered on the outer periphery of the foldable bracket (21) and the hub (10) by hot melt welding.

6. The foldable impeller according to claim 1, characterized in that: The film (22) leaves a crease (221) in the middle of the adjacent support piece (211). When the blade (20) is under constraint, the film (22) is gathered along the crease (221).

7. The foldable impeller according to claim 1, characterized in that: The blade (20) includes a working surface (23), the outline of which includes an outer edge profile away from the hub (10). The end point of the outer edge profile near the inlet is the profile start point, and the end point of the outer edge profile near the outlet is the profile end point. The angle between the axial plane where the profile start point is located and the axial plane where the profile end point is located is the blade deflection angle θ. The blade deflection angle θ is 90° to 180°.

8. The foldable impeller according to claim 1, characterized in that: The angle between the tangent of the impeller arc at the position where the blade (20) extends from the hub (10) and the tangent of the hub (10) is the blade inflow angle α, which is 90° to 180°.

9. A blood pump, characterized in that: Includes a conduit and a foldable impeller as described in any one of claims 1 to 8 disposed within the conduit.

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