Patent Publication Number: US-2023144798-A1

Title: Interventional ventricular assist device

Description:
This application claims priority to Chinese Patent Application No. 202010758361.8, titled “interventional ventricular assist device”, filed Jul. 31, 2020, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present application relates to the technical field of medical devices, and more particularly to an interventional ventricular assist device. 
     BACKGROUND 
     The statements herein only provide background information related to the present application, and do not necessarily constitute prior art. A traditional interventional ventricular assist device adopts a mechanical bearing to achieve rotation of an impeller, which, however, has mechanical friction, and will bring potential risk of blood compatibility, and a bearing joint of the mechanical bearing is prone to thrombosis formation. 
     Technical Problems 
     It is an objective of the present application to provide an interventional ventricular assist device, which aims at solving the technical problem in the conventional interventional ventricular assist device that the risk of blood compatibility is resulted from the mechanical friction. 
     Technical Solutions 
     In order to solve the above-described technical problems, technical solutions adopted by embodiments of the present application are as follows: 
     In one aspect, it is provided an interventional ventricular assist device, which comprises: an interventional tube, a motor assembly, a perfusion cylinder, and an impeller assembly. 
     The interventional tube has a liquid inlet and a liquid outlet. 
     The impeller assembly comprises an impeller, the impeller is accommodated within the interventional tube, and the impeller is rotatable to enable a liquid to flow into the interventional tube via the liquid inlet and out therefrom via the liquid outlet. 
     The motor assembly is configured to generate a rotating magnetic field to drive the impeller to rotate and generate an attraction to the impeller. 
     The perfusion cylinder is configured to inject a perfusate into the interventional tube and enable the perfusate injected from the perfusion cylinder to provide a thrust to the impeller assembly, whereby the impeller is suspendedly rotatable in the interventional tube under a combined action of the thrust and the attraction. 
     Advantages 
     Advantages of the interventional ventricular assist device provide by embodiments of the present application are summarized as follows: In the interventional ventricular assist device provided by embodiments the present application, and the motor assembly is configured to generate a rotating magnetic field to drive the impeller to rotate and generate an attraction to the impeller. A perfusate injected from the perfusion cylinder provide a thrust to the impeller assembly, such that the impeller is suspendedly rotatable under a combined action of the thrust and the attraction. Compared with the mechanical bearing, the mechanical friction between the impeller and other parts is avoided, such that not only is the risk of blood contamination by abrasive particles generated from the mechanical friction avoided, but also the risk of thrombus formation at the mechanical bearing is avoided. Meanwhile, compared with the utilization of a flexible part to drive the impeller to rotate, the interventional ventricular assist device according to embodiments of the present application generates less vibration, which makes the patient feel more comfortable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings that need to be used in the description of the embodiments or the prior art will be briefly described hereinbelow. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. 
         FIG.  1    is a perspective view of an interventional ventricular assist device provided by an embodiment of the present application; 
         FIG.  2    is another perspective view of the interventional ventricular assist device of  FIG.  1   ; 
         FIG.  3    is an exploded view of the interventional ventricular assist device of  FIG.  2   ; 
         FIG.  4    is a lateral side view of the interventional ventricular assist device of  FIG.  1   ; 
         FIG.  5    is a cross section view taken from line AA of the interventional ventricular assist device of  FIG.  4   ; 
         FIG.  6    is an enlarged view of a middle region of the interventional ventricular assist device of  FIG.  4   ; 
         FIG.  7    is a perspective view of a motor casing of  FIG.  1   ; 
         FIG.  8    is a bottom view of the motor casing of  FIG.  7   ; 
         FIG.  9    is a cross section view taken from line BB of the motor casing of  FIG.  8   ; 
         FIG.  10    is a perspective view of the motor casing of  FIG.  8    from another angle; 
         FIG.  11    is a cross section view taken from line CC of the motor casing of  FIG.  10   ; 
         FIG.  12    is a perspective view of an impeller of  FIG.  6   ; 
         FIG.  13    is a perspective view of the impeller of  FIG.  12    from another angle; 
         FIG.  14    is a bottom view of the impeller of  FIG.  13   ; 
         FIG.  15    is a cross section view taken from line DD of the impeller of  FIG.  14   ; and 
         FIG.  16    is a structural view of a motor casing provided by another illustration of the present application. 
     
    
    
     In the drawings, the following reference numerals are adopted: 
       100 : Interventional ventricular assist device;  10 : Interventional tube;  11 : Liquid inlet;  12 : Liquid outlet;  13 : First channel;  14 : Straight tubular segment;  15 : Bend tubular segment;  20 : Impeller assembly;  21 : Impeller;  211 : Hub;  2111 : First installation groove;  2111   a : Straight hole portion;  2111   b : Inclined hole portion;  2112 : Second installation groove;  2113 : Flow guiding hole;  2114 : Blade;  2115 : Cylindrical segment;  2116 : Conical segment;  212 : Magnetic member;  213 : Seal cover;  22 : Transmission shaft;  30 : Motor assembly;  31 : Stator;  32 : Motor casing;  321 : Annular groove;  322 : Limiting groove;  3221 : Groove opening;  3222 : Bottom wall;  323 : Cylinder;  324 : Hole assembly;  3241 : First hole;  3242 : Second hole;  325 : Step;  33 : Cover plate;  331 : Through hole;  40 : Perfusion cylinder;  41 : Second channel; and  42 : Cable outlet. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In order to make the purposes, technical solutions, and advantages of the present application clearer and more understandable, the present application will be further described in detail hereinafter with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described herein are only intended to illustrate but not to limit the present application. 
     It should be noted that when an element is described as “fixed” or “arranged” on/at another element, it means that the element can be directly or indirectly fixed or arranged on/at another element. When an element is described as “connected” to/with another element, it means that the element can be directly or indirectly connected to/with another element. Terms “upper”, “lower”, “left”, “right”, and the like indicating orientation or positional relationship are based on the orientation or the positional relationship shown in the drawings, and are merely for facilitating and simplifying the description of the present application, rather than indicating or implying that a device or component must have a particular orientation, or be configured or operated in a particular orientation, and thus should not be construed as limiting the application. The terms “first” and “second” are adopted for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. The meaning of “a plurality of” or “multiple” is two or more unless otherwise specifically defined. 
     Technical solutions of the present application will be described in details in combination with the specific drawings and embodiments. 
     As shown in  FIGS.  1 - 6   , an embodiment of the present application provides an interventional ventricular assist device  100 , and more particularly to a centrifugal magnetic suspension ventricular assist device. The interventional ventricular assist device  100  can be applied in a right ventricle as well as a left ventricle. When being applied in the left ventricle, the interventional ventricular assist device can be inserted into the left ventricle via an aorta. The interventional ventricular assist device  100  comprises: an interventional tube  10 , an impeller assembly  20 , a motor assembly  30 , and a perfusion cylinder  40 . In an embodiment as illustrated, the motor assembly  30  is connected between the interventional tube  10  and the perfusion cylinder  40 . The motor assembly  30  is adapted to generate a rotating magnetic field, and the impeller assembly  20  is adapted to rotate under the rotating magnetic field generated by the motor assembly  30 , so as to provide a thrust for impelling the liquid (for example, the blood) to flow. 
     As shown in  FIGS.  1 - 2   , the interventional tube  10  comprises a liquid inlet  11  and a liquid outlet  12 . The liquid inlet  11  is configured to allow the blood to enter the interventional tube  10 , and the liquid outlet  12  is configured to allow the blood to flow out of the interventional tube  10 . In the illustrated embodiment, the liquid inlet  11  and the liquid outlet  12  are arranged at two ends of the interventional tube  10 , respectively. In an embodiment, the interventional tube  10  has an outer diameter fitted with an inner diameter of the aorta. The interventional tube  10  has a generally conical tip, which facilitates insertion into the blood vessel. The liquid inlet  11  is defined in the tip, and a plurality of the liquid inlets  11  are arranged at intervals around a center axis of the tip. In particular, the liquid outlet  12  is defined in a wall of the interventional tube  10  at an end thereof far away from the liquid inlet  11 , that is, the liquid outlet  12  is radially arranged (herein, the direction of the rotation axis of the impeller assembly  20  is defined as the axial direction, and the direction perpendicular to the rotation axis of the impeller assembly  20  is defined as the radial direction). A plurality of the liquid outlets  12  are provided, and the plurality of the liquid outlets  12  are arranged at intervals in a circle around the central axis of the interventional tube  10 . In particular, the interventional tube  10  comprises: a straight tubular segment  14 , and a bend tubular segment  15  bent and extended from one end of the straight tubular segment  14 , and an end of the straight tubular segment  14  far away from the bend tubular segment  15  is in fixed connection with a motor assembly  30 , the liquid inlet  11  is arranged at an end of the bend tubular segment  15  far away from the straight tubular segment  14 , the liquid outlet  12  is arranged at a wall of the straight tubular segment  14  at the end thereof far away from the bend tubular segment  15 , the impeller  21  is rotatably accommodated in the straight tubular segment  14 . The conical tip is arranged at the end of the bend tubular segment  15  far away from the straight tubular segment  14 . 
     It should be noted that the number of the liquid outlet  12  and the number of the liquid inlet  11  are not restricted to a plural, and can also be only one, respectively. The number of the liquid outlet  12  and the number of the liquid inlet  11  can be provided according to practical needs. 
     The impeller assembly  20  comprises an impeller  21 . The impeller  21  is accommodated in the interventional tube  10  and rotatable to enable the liquid to enter the interventional tube  10  via the liquid inlet  11  and to flow out via the liquid outlet  12 . That is, a rotation axis of the impeller assembly  20  is the rotation axis of the impeller  21 . In particular, the impeller  21  is arranged approximate one end of the liquid outlet  12  of the interventional tube  10 . When the interventional ventricular assist device  100  is applied in the left ventricle, the blood in the left ventricle enters the interventional tube  10  via the liquid inlet  11 , and then flows out of the interventional tube  10  via the liquid outlet  12  and into the aorta. 
     Specifically in the illustrated embodiment, as shown in  FIG.  6   , the impeller  21  comprises: a hub  211  and the magnetic members  212  arranged in the hub  211 . The magnetic member  212  is in a ring shape, and further, the magnetic member  212  is a Halbach array magnetic ring. 
     The motor assembly  30  is configured to generate a rotating magnetic field to drive the impeller  21  to rotate. In particular, the motor assembly  30  is arranged at the end of the interventional tube  10  provided with the liquid outlet  12 . The impeller  21  rotates under the cooperation of the magnetic member  212  and the motor assembly  30 . At certain rotational speeds, a radial suspension of the impeller  21  can also be achieved under the cooperation of the magnetic member  212  and the motor assembly  30 . In the present application, a state where the impeller  21  is not in contact with the sidewall of the interventional tube  10  nor the motor assembly  30  is referred to as the suspension of the impeller  21 . 
     An attraction between the motor assembly  30  and the impeller  21  is adapted to be generated, so that the impeller  21  has a tendency to move toward the direction of the motor assembly  30 . In order to achieve a balance in the axial direction, in the present application, the perfusion liquid is utilized to apply a hydraulic thrust to the impeller  21 . The hydraulic thrust includes at least a force urging the impeller  21  to move in a direction far away from the motor assembly  30 , whereby the suspension of the impeller  21  in the axial direction is realized. A perfusion cylinder  40  can be used to inject the perfusate into the interventional tube  10 , and the perfusate injected from the perfusion cylinder  40  is configured to provide a thrust to the impeller assembly  20  so that the impeller  21  is suspendedly rotatable in the interventional tube  10  under a combined action of the motor assembly  30  and the perfusion liquid. That is, the impeller  21  is suspendedly rotatable under a combination of the action between the motor assembly  30  and the impeller  21  and the action of the perfusate to the impeller assembly  20 . In other words, the thrust is adapted to offset at least the attraction between the motor assembly  30  and the magnetic member  212  of the impeller  21 , so that the impeller  21  is suspended in the axial direction. The suspension rotation of the impeller  21  results in that almost no mechanical friction exists between the impeller  21  and the interventional tube  10 . 
     In the interventional ventricular assist device  100  provided by the present application, a rotating magnetic field is generated by the motor assembly  30  to drive the impeller  21  to rotate, and a thrust is applied by the perfusate to the impeller  21 , so that the impeller  21  is suspended rotatable under a combination of the action between the motor assembly  30  and the impeller  21  and the action of the perfusate to the impeller assembly  20 . Compared with the mechanical bearing, the mechanical friction between the impeller  21  and other parts is avoided in the present application, such that not only is the risk of blood contamination by abrasive particles generated from the mechanical friction avoided, but also the risk of thrombus formation at the mechanical bearing is avoided. Meanwhile, compared with the utilization of a flexible part to drive the impeller  21  to rotate, the interventional ventricular assist device  100  according to embodiments of the present application generates less vibration, which makes the patient feel more comfortable. 
     In a specific embodiment, the perfusate is a glucose containing heparin or a physiological saline containing heparin. It can be understood that, in other embodiments of the present application, the perfusate may also be the common glucose or physiological saline. The perfusate can not only provide a thrust to the impeller  21 , but also wash the impeller  21  by the heparin contained therein, whereby the blood clotting is avoided and the thrombus formation is reduced. 
     In a specific embodiment, as shown in  FIG.  6   , the motor assembly  30  defines therein a limiting groove  322  and a hole assembly  324 . The limiting groove  322  is in communication with the interventional tube  10 , the hole assembly  324  is in communication with the limiting groove  322 , and the perfusion cylinder  40  is in communication with the hole assembly  324 , such that the perfusate injected via the perfusion cylinder  40  can sequentially pass through hole assembly  324  and the limiting groove  322  and then flow into the interventional tube  10 . With such a configuration, the perfusate also functions in cooling down the motor assembly  30 . 
     In a specific illustrated embodiment, the limiting groove  322  comprises: a groove opening  3221 , and a bottom wall  3222  opposite to the groove opening  3221 ; and the groove opening  3221  is in communication with the interventional tube  10 . Specifically, the limiting groove  322  further comprises a sidewall in connection with the bottom wall  3222 . The sidewall has a cylindrical surface and extends along an axial direction of the impeller  21 . In such condition, the bottom wall  3222  and the sidewall of the limiting groove  322  are both groove walls of the limiting groove  322 . 
     The impeller assembly  20  further comprises a transmission shaft  22 . One end of the transmission shaft  22  is in fixed connection with the impeller  21 , and the other end of the transmission shaft  22  protrudes into the limiting groove  322 . The transmission shaft  22  is rotatable along the impeller  21 , and the other end of the transmission shaft  22  far away from the impeller  21  is suspendable in the limiting groove  322 . A rotation axis of the transmission shaft  22  coincides with a rotation axis of the impeller  21 . The hole assembly  324  faces the other end of the transmission shaft  22  far away from the impeller  21 , and the perfusate injected into the limiting groove  322  via the hole assembly  324  is adapted to provide a thrust onto the transmission shaft  22 , such that the transmission shaft  22  and the impeller  21  are suspendedly rotatable under a combined action of the motor assembly  30  and the perfusate. In such condition. during operation, the perfusate injected into the limiting groove  322  provides a thrust to the transmission shaft  22 , and the transmission shaft  22  in turn transmits the thrust to the impeller  21 . Specifically, the transmission shaft  22  passes through the groove opening  3221  and protrudes toward the bottom wall  3222 . In the illustrated embodiment, the transmission shaft  22  is cylindrical. The end of the transmission shaft  22  far away from the impeller  21  has an end surface in a shape of a convex hemisphere. The transmission shaft  22  is arranged at the rotation axis of the impeller  21 , and an extension direction of the transmission shaft  22  is consistent with the rotation axis of the impeller  21 . 
     In a specific embodiment, as shown in  FIGS.  6 ,  8 , and  11   , the hole assembly  324  includes a first hole  3241 , and the first hole  3241  is in communication with the limiting groove  322  and the perfusion cylinder  40 . In one of the embodiments, one opening of the first hole  3241  is defined in the bottom wall  3222 , and the other opening thereof is in communication with the perfusion cylinder  40 . The first hole  3241  is aligned with a center of the end surface of the end of the transmission shaft  22  away from the impeller  21 . In this way, the perfusate injected from the first hole  3241  will directly act on the end surface of the end of the transmission shaft  22  far away from the impeller  21 , applying a thrust to the transmission shaft  22  in the axial direction, and the thrust counteracts with the attraction of the motor assembly  30  applied to the magnetic member  212 , whereby the transmission shaft  22  is balanced in the axial direction. Specifically, the central axis of the first hole  3241  coincides with the rotation axis of the transmission shaft  22 . The central axis of the first hole  3241  coincides with the central axis of the limiting groove  322 . It can be understood that, in other embodiments of the present application, an aperture of the first hole  3241  is the same as an aperture of the limiting groove  322 , that is, the limiting groove  322  passes through the motor assembly  30  along the axial direction of the impeller  21 , which is not exclusively limited herein. 
     Further, as shown in  FIGS.  8  to  11   , the hole assembly  324  further comprises a plurality of second holes  3242 . The plurality of second holes  3242  are all in communication with the perfusion cylinder  40  and the limiting groove  322 , the first hole  3241  is aligned with the center of the end surface of the end of the transmission shaft  22  far away from the impeller  21 . The plurality of second holes  3242  are arranged at equal intervals in a circle around the first hole  3241 , and the plurality of second holes  3242  face the end surface of the end of the transmission shaft  22  far away from the impeller  21 . Since the end surface of the end of the transmission shaft  22  far away from the impeller  21  is in a shape of the convex hemisphere, by adopting the plurality of second holes  3242  in the above arrangement, the thrust force applied by the perfusate injected via the plurality of second holes  3242  to the transmission shaft  22  have at least a radial component or alternatively, all the thrust force is a completely radial force. In addition, as the plurality of second holes  3242  are evenly distributed in the circumferential direction, the radial thrust force exerted by the perfusate injected via the plurality of second holes  3242  onto the transmission shaft  22  can be balanced with each other, so as to further ensure the suspension balance of the transmission shaft  22  in the radial direction, and prevent the transmission shaft  22  from mechanical collision and interference with the groove wall of the limiting groove  322 . In one of the embodiments, the axial directions of the plurality of second holes  3242  are parallel to the axial direction of the first hole  3241 , and the plurality of second holes  3242  are arranged at equal intervals around the central axis of the first hole  3241 . It should be understood that the axial directions of the plurality of second holes  3242  and the axial direction of the first hole  3241  may not be in parallel. 
     In a specific embodiment, as shown in  FIG.  6   , the bottom wall  3222  of the limiting groove  322  is in a shape of a concave hemisphere, and the first hole  3241  is arranged at a center of the bottom wall  3222 . In one of the embodiments, a curvature of the bottom wall  3222  of the limiting groove  322  is consistent with a curvature of the end surface of the end of the transmission shaft  22  far away from the impeller  21 . It can be understood that the curvature of the bottom wall  3222  of the limiting groove  322  may also be inconsistent with the curvature of the end surface of the end of the transmission shaft  22  far away from the impeller  21 . 
     As shown in  FIGS.  9 - 11   , in a specific illustrated embodiment, the number of the second holes  3242  is four, and the four second holes  3242  are arranged at equal intervals around the central axis of the first hole  3241 , and the four second holes  3242  are defined in the bottom wall of the limiting groove  322 . It can be understood that, in other embodiments of the present application, according to practical design requirements, the number of the second holes  3242  may also be three, five, or more than five, which is not exclusively limited herein. 
     It should be noted that the form of the hole assembly  324  is not limited to the above form. In other embodiments, the hole assembly  324  comprises a plurality of first holes  3241 , and the plurality of first holes  3241  all face the end surface of the end of the transmission shaft  22  far away from the impeller  21 , and the plurality of first holes  3241  are arranged at intervals around the rotation axis of the transmission shaft  22 . In such condition, if the hole assembly  324  further has a plurality of second holes  3242 , the plurality of second holes  3242  are arranged around the rotation axis of the transmission shaft  22  and along an outer periphery of the plurality of first holes  3241 . 
     In a specific embodiment, as shown in  FIGS.  1 - 3   , the motor assembly  30  comprises a motor casing  32  and a stator  31 . The motor casing  32  is in sealed connection with both the interventional tube  10  and the perfusion cylinder  40 . The motor casing  32  is arranged at an end of the interventional tube  10  approximate the liquid outlet  12 , and the perfusion cylinder  40  is arranged at an end of the motor casing  32  far away from the interventional tube  10 . As shown in  FIGS.  3  and  6   , the interventional tube  10  defines therein a first channel  13 , the first channel  13  is in communication with the liquid inlet  11  and the liquid outlet  12 , respectively, and the impeller  21  is accommodated in the first channel  13 . The stator  31  is installed and sealed within the motor casing  32 . The limiting groove  322 , the first hole  3241 , and the second holes  3242  are all defined in the motor casing  32 . The perfusion cylinder  40  defines therein a second channel  41  which is in communication with the first hole  3241  and the second holes  3242 , respectively. By defining the limiting groove  322 , the first hole  3241 , and the second holes  3242  in the motor casing  32 , the perfusate can also functions in cooling the motor assembly  30 , and therefore the service life of the motor assembly  30  is increased. It can be understood that, in other embodiments of the present application, if conditions permit, the interventional tube  10 , the motor casing  32 , and the perfusion cylinder  40  may also be integrally formed, which is not exclusively limited herein. 
     As shown in  FIG.  6   , the stator  31  and the impeller  21  are spaced apart from each other in the axial direction, so that the impeller  21  has a larger torque, so that the impeller  21  can rotate at a lower rotational speed, thereby reducing the shear stress of the impeller  21  imposed on the blood, lowering the damage of the blood caused by the impeller  21 , and reducing the hemolysis. In addition, compared to the conventional arrangement of the stator  31  surrounding the impeller  21 , the impeller  21  of the present application can have a larger size, which is more convenient to manufacture, and is conducive to reduction of the manufacturing cost. 
     In a specific embodiment, as shown in  FIGS.  3 ,  9  and  11   , the motor casing  32  defines therein an annular groove  321 , the annular groove  321  is arranged around the limiting groove  322 , and the annular groove  321  is spaced apart from the limiting groove  322 . In particular, the central axis of the limiting groove  322  coincides with the central axis of the motor casing  32 , and the annular groove  321  and the limiting groove  322  are coaxially arranged. An opening of the annular groove  321  faces the perfusion cylinder  40 , and the opening of the limiting groove  322  faces the interventional tube  10 , that is, the opening of the annular groove  321  and the opening of the limiting groove  322  face different ends of the motor casing  32  in the axial direction, respectively, and the annular groove  321  and the limiting groove  322  are not in communication with each other. The stator  31  is also in an annular shape, and the stator  31  is accommodated in the annular groove  321 . The opening of the annular groove  321  is covered by a cover plate  33 , the cover plate  33  has an annular shape, and the cover plate  33  is provided at the annular groove  321 , so that the stator  31  is mounted in the motor casing  32  in a sealed manner. 
     As shown in  FIGS.  6 - 7   , the motor casing  32  has a cylindrical shape as a whole. An outer wall of the motor casing  32  is flush with an outer wall of the interventional tube  10  at a junction of the motor casing  32  and the interventional tube  10 , and the outer wall of the motor casing  32  is flush with an outer wall of the perfusion cylinder  40  at a junction of the motor casing  32  and the perfusion cylinder  40 . Two ends of the motor casing  32  form a plug fit with the interventional tube  10  and the perfusion cylinder  40 , respectively. In particular, a step  325  is formed at a periphery of one end of the motor casing  32 , and the end of the interventional tube  10  far away from the liquid inlet  11  is sleeved at the step  325  of the motor casing  32  and formed a sealed connection by pasting, welding, and hot pressing, etc. 
     In a specific embodiment, as shown in  FIG.  6   , a cylinder  323  extends along a central axis of the annular groove  321 , the cylinder  323  and the annular groove  321  are arranged concentrically. An end of the cylinder  323  protrudes outside of the annular groove  321 , and the end of the cylinder  323  protruding from the annular groove  321  is received in the perfusion cylinder  40 . The limiting groove  322 , the first hole  3241 , and the second holes  3242  are all formed in the cylinder  323 . Specifically, the limiting groove  322  axially extends inward from one end of the cylinder  323  facing the interventional tube  10 , and the first hole  3241  and the second holes  3242  axially extend inward from the other end of the cylinder  323  to the bottom wall of the limiting groove  322 . The second channel  41  extends axially along the perfusion cylinder  40 , the central axis of the second channel  41  coincides with the central axis of the first hole  3241 , and an aperture of the second channel  41  is greater than a diameter of an outer contour circle D formed by all the second holes  3242 . It should be noted herein that the outer contour circle D formed by all the second holes  3242  refers to the circle where the points of the various second holes  3242  farthest from the central axis of the first hole  3241  are arranged. Specifically, the outer contour circle D of all the second holes  3242  is indicated by a dotted circle in  FIG.  8   . When the aperture of the second channel  41  is greater than the diameter of the outer contour circle D of all the second holes  3242 , the perfusate injected from the second channel  41  can be injected into the first hole  3241  and all the second holes  3242 , such that the impeller is maintained balanced in the axial and radial direction. 
     As shown in  FIG.  6   , the perfusion cylinder  40  further defines therein a cable outlet  42 , and the cable owlet  42  is spacedly arranged apart from the second channel  41 . The cover plate  33  defines therein a through hole  331  with a position thereof corresponding to the cable outlet  42 . A control line of the stator  31  sequentially passes through the through hole  331  and the cable outlet  42  and forms a communication connection with an external controller. 
     As shown in  FIG.  12   , the impeller  21  comprises a cylindrical segment  2115  and a conical segment  2116 . The cylindrical segment  2115  and the conical segment  2116  are integrally connected along the axial direction of the impeller  21 . The cylindrical segment  2115  is arranged approximate the motor casing  32 . The conical segment  2116  is arranged far away from the motor casing  32 , and the magnetic member  212  is installed within the cylindrical segment  2115 . One end of the transmission shaft  22  is installed at a center of the cylindrical segment  2115 . Four blades  2114  are distributed on an outer circumference of the conical segment  2116 , and each of the blades  2114  is spirally distributed on an outer wall of the conical segment  2116 . 
     In a specific embodiment, as shown in  FIGS.  13 - 15   , the impeller  21  defines therein a first installation groove  2111  and a second installation groove  2112 . In particular, the first installation groove  2111  and the second installation groove  2112  are formed in the hub  211 . Both openings of the first installation groove  2111  and the second installation groove  2112  face the motor casing  32 . The first installation groove  2111  is circular and arranged in the center of the impeller  21 , the second installation groove  2112  is circular and surrounds the first installation groove  2111 , the second installation groove  2112  and the first installation groove  2111  are arranged concentrically, that is, a center line of the second installation groove  2112 , and a center line of the first installation groove  2111 , and a center line of the entire impeller  21  coincide. An end of the transmission shaft  22  away from the limiting groove  322  is accommodated in the first installation groove  2111 , and the magnetic member  212  is accommodated in the second installation groove  2112 , so that the magnetic member  212 , the transmission shaft  22 , and the impeller after installation  21  are arranged concentrically. When the stator  31  applies a rotating magnetic field to the magnetic member  212 , the magnetic member  212  drives the transmission shaft  22  and the impeller  21  to rotate, and the magnetic member  212 , the transmission shaft  22  and the impeller  21  coaxially rotate. 
     As shown in  FIG.  6   , the magnetic member  212  is in an annular shape and installed in the second installation groove  2112 . The second installation groove  2112  is also covered with a seal cover  213 , and the magnetic member  212  is sealed by the seal cover  213  and fixed In the second installation groove  2112 , therefore, the magnetic member  212  is prevented from being contaminated by blood or the perfusate, which would otherwise damaging the efficacy. 
     As shown in  FIG.  6   , one end of the transmission shaft  22  is inserted into the first installation groove  2111 , and the transmission shaft  22  can be fixed in the first installation groove  2111  by interference fit, welding, pasting, or fasteners. 
     In a specific embodiment, as shown in  FIG.  6    and  FIGS.  12 - 15   , the impeller  21  defines therein a flow guiding hole  2113 . The flow guiding hole  2113  has two openings. One opening of the flow guiding hole  2113  faces the liquid outlet  12 , and the other opening faces the limiting groove  322 . In some illustrated embodiments, the flow guiding hole  2113  is defined in the hub  211 . Based on the arrangement of the flow guiding hole  2113 , the perfusate injected into the limiting groove  322  from the second channel  41  can enter the interventional tube  10  through the flow guiding hole  2113  and flow out via the liquid outlet  12 ; meanwhile, the blood flowing from a first gap between the interventional tube  10  and the impeller  21  to a second gap between the impeller  21  and the motor casing  32  can flow back to the liquid outlet  12  through the flow guiding hole  2113  to form a secondary flow field, so as to flush the blood and reduce the blood retention. And along the radial direction of the impeller  21 , the respective flow guiding holes  2113  are arranged between the first installation groove  2111  and the second installation groove  2112 . 
     Further, a plurality of the flow guiding holes  2113  are defined in the impeller  21 , the plurality of the flow guiding holes  2113  are arranged at equal intervals around the rotation axis of the impeller  21 . Each of the plurality of the flow guiding holes  2113  has one opening facing one of the liquid outlets, and the other opening facing the limiting groove  322 . 
     In an illustrated embodiment, the number of the flow guiding holes  2113  are four, and the four flow guiding holes  2113  are specifically formed in the hub  211 . It should be noted that the flow guiding hole  2113  is not limited to four, the flow guiding hole  2113  can also be one, two, three, or more than four, and the number of the flow guiding hole  2113  can be determined according to practical needs. 
     Further, as shown in  FIGS.  6  and  15   , the first installation groove  2111  comprises: a straight hole portion  2111   a,  and an inclined hole portion  2111   b  in communication with the straight hole portion  2111   a.  An aperture of the inclined hole portion  2111   b  gradually increases in a direction far away from the straight hole portion  2111   a.  The inclined hole portion  2111   b  faces the limiting groove  322 , and an opening of the flow guiding hole  2113  far away from the liquid outlet  12  is arranged at a sidewall of the inclined hole portion  2111   b.  The end of the transmission shaft  22  away from the limiting groove  322  is accommodated in the inclined hole portion  2111   b  and the straight hole portion  2111   a,  and is in fixed connection with a sidewall of the straight hole portion  2111   a.  In this way, after the transmission shaft  22  is installed in the first installation groove  2111 , a third gap is provided between the transmission shaft  22  and an inner wall of the inclined hole portion  2111   b,  and the perfusate flowing out of the limiting groove  322  can directly flow into the flow guiding hole  2113  via the third gap. That is, the inclined inner wall of the inclined hole portion  2111   b  functions in flow guiding, which quickly guides the perfusate or blood into the flow guiding hole  2113  to form a secondary flow field. 
     In another embodiment of the present application, the hole assembly  324  and the limiting groove  322  may be connected in other ways, as shown in  FIG.  16   , the groove wall of the limiting groove  322  is a cylindrical surface, and the hole assembly  324  comprises a first hole  3241  and a plurality of second holes  3242 , the first hole  3241  and the plurality of second holes  3242  are all in communication with the perfusion cylinder  40  and the limiting groove  322 , the first hole  3241  faces an end surface of one end of the transmission shaft  22  far away from the impeller  21 , and the plurality of the second holes  3242  are evenly arranged at intervals in a circle around a center line of the first hole  3241 . Specifically, the plurality of second holes  3242  are arranged on the sidewall of the limiting groove  322 , and the plurality of second holes  3242  face a peripheral side of the transmission shaft  22 . In this way, by the arrangement of the plurality of second holes  3242 , the perfusate can be introduced into the limiting groove  322  and acts on the peripheral side of the transmission shaft  22  respectively, so as to realize the radial balance of the transmission shaft  22 . 
     The above is only the preferred embodiments of the present application, and is not intended to limit the application. For those skilled in the art, the application may have various alterations and changes. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application are included in the protection scope of the present application.