Intravascular blood pump

Abstract

It is an object of the present invention to provide a percutaneously insertable blood pump for supporting blood circulation.SOLUTION: The intravascular blood pump (1) comprises a catheter (5), a rotor (10), a housing (11) in which the rotor (10) is accommodated, and a highly flexible drive shaft (12) which extends through the catheter (5) and is rotatably supported in a proximal bearing (13) located proximally of the rotor (10). The proximal bearing (13) comprises a bearing sleeve (30) and an outer bearing ring (32). The bearing sleeve (30) comprises a proximal portion located proximally of the outer bearing ring (32), wherein the proximal portion of the bearing sleeve (30) forms an axial bearing with a proximal surface of the outer bearing ring (32). The bearing sleeve (30) comprises a distal portion extending distally from a proximal portion of the bearing sleeve (30) into the outer bearing ring (32), wherein the distal portion of the bearing sleeve (30) forms a radial bearing with the outer bearing ring (32).SELECTED DRAWING: Figure 12A

Description

[Technical Field]

[0001] The present invention relates to an intravascular blood pump, in particular a percutaneously insertable blood pump, for assisting blood circulation in humans or optionally further animals. For example, the blood pump may be designed to be percutaneously inserted into a patient's femoral artery and guided through the patient's vascular system, for example to assist or replace the pumping action of the heart.

[0002] Although the present invention is described in the context of an intravascular blood pump having an expandable housing containing an expandable rotor driven by an extracorporeal motor via a long, flexible drive shaft, the present invention is also applicable to other types of intravascular blood pumps. [Background technology]

[0003] The aforementioned expandable blood pump is known, for example, from U.S. Patent Publication No. 2013 / 0303969 A1, which discloses a catheter pump assembly. An expandable housing is located at the distal end of a catheter. The expandable housing surrounds an expandable rotor, which is driven by a flexible drive shaft extending through a first lumen of the catheter. The distal portion of the catheter pump assembly can be placed inside the heart via percutaneous access, for example, using the Seldinger technique. The drive shaft includes a central lumen, which allows a guidewire to pass through the drive shaft along with its guide, enabling precise positioning of the catheter pump assembly inside the heart. The rotor is rotatably supported at the end of the catheter and within a proximal bearing located proximal to the rotor. In this specification, "proximal" and "distal" refer to a position relative to the physician. Thus, when placing a catheter, "proximal" refers to a position relatively closer to the physician, while "distal" refers to a position relatively farther away from the physician.

[0004] During use of an intravascular blood pump, the rotor and drive shaft are required to rotate at significant speeds. Therefore, it is necessary to provide a bearing that rotatably supports the drive shaft with low friction while maintaining high durability. Summary of the Invention [Means for solving the problem]

[0005] According to a first aspect of the present invention, an intravascular blood pump includes a catheter and a housing in which a rotor is housed, the housing attached to the distal end of the catheter. Furthermore, in the intravascular blood pump disclosed herein, a flexible drive shaft extends through the catheter. The flexible drive shaft is connected to the rotor and rotatably supported in a proximal bearing located proximal to the rotor. The proximal bearing includes a bearing sleeve and an outer bearing ring, the bearing sleeve having a proximal portion located proximal to the outer bearing ring, the proximal portion of the bearing sleeve forming an axial bearing with a proximal surface of the outer bearing ring. The bearing sleeve further includes a distal portion extending distally from the proximal portion of the bearing sleeve into the outer bearing ring, the distal portion of the bearing sleeve forming a radial bearing with the outer bearing ring. The described proximal bearing design can advantageously achieve low friction and high durability, particularly when a purge fluid is provided to flow through the gap defined by the radial bearing.

[0006] Preferably, the bearing sleeve is fixedly connected to the flexible drive shaft. The bearing sleeve may be crimped, soldered, welded, glued or shrink-fitted to the flexible drive shaft. Gluing the bearing sleeve may advantageously avoid any distortion or twisting of the bearing sleeve.

[0007] The proximal bearing is preferably located inside the distal end region of the catheter and / or inside the proximal end region of the housing. Alternatively, the proximal bearing, preferably the axial proximal bearing, may be located anywhere within the catheter, and there may even be two or more proximal bearings, where the term "proximal" means that the bearing is located somewhere proximal to the rotor. Preferably, the outer bearing ring is fixedly connected inside the distal end region of the catheter or inside the proximal end region of the housing. The outer bearing ring may be press-fit and / or glued into the catheter and / or housing. In some embodiments, the outer bearing ring may be fitted into both the housing and the catheter, thereby connecting the housing to the catheter. A proximal bearing located at the distal end of the catheter or the proximal end of the housing may provide particularly stable support for the drive shaft and rotor.

[0008] Preferably, a restricting member is located inside the catheter and / or housing proximal to the bearing sleeve. It may be fixedly attached inside the proximal end of the housing or inside the distal end of the catheter. The restricting member acts as a stop limiting axial movement of the bearing sleeve relative to the outer bearing ring. The restricting member may advantageously prevent the bearing sleeve from sliding off the outer bearing ring. In some embodiments, the restricting member forms part of the proximal bearing. Preferably, the inner diameter of the restricting member is slightly larger than the diameter of the flexible drive cable to avoid frictional contact with the flexible drive cable and to allow for the passage of purge fluid.

[0009] The inner diameter of the bearing ring is preferably 0.6 mm to 2.2 mm, more preferably 0.9 mm to 1.3 mm. The axial length of the bearing ring preferably corresponds to 1 to 2 times the inner diameter of the bearing ring, more preferably 1.2 to 1.6 times the inner diameter of the bearing ring. In a particularly preferred embodiment, the inner diameter is 1.1 mm and the axial length is 1.6 mm.

[0010] Preferably, the radial bearing gap between the outer bearing ring and the bearing sleeve is 1 μm to 10 μm wide, more preferably 2 μm to 8 μm wide. Most preferably, the radial bearing gap is approximately 3.5 μm wide. Purge fluid can be forced through the radial bearing gap of the proximal bearing. When the radial bearing gap is configured in this way, the purge fluid can flow at a reproducible rate, given a suitable purge fluid pressure.

[0011] Preferably, the flexible drive shaft is at least partially filled with a sealant. Preferably, the sealant completely penetrates the flexible drive shaft, creating a waterproof drive shaft at least in one location. Here, the sealant is a substance that penetrates the layer as a fluid and then hardens sufficiently to prevent penetration of the purge fluid. Examples of sealants within the meaning of the present invention are adhesives, polymers, and / or thermoplastics.

[0012] Preferably, the bearing sleeve and / or outer bearing ring comprise one or more ceramics and / or metals. The metal is preferably MP35, 35NLT, Nitinol, or stainless steel. If made of metal, the bearing sleeve and / or outer bearing may comprise a coating. Preferably, the bearing sleeve and / or outer bearing ring are hard-coated, e.g., DLC-coated. Advantageously, a bearing sleeve or outer bearing ring designed in this manner allows for a lightweight, durable proximal bearing.

[0013] Preferably, the proximal end region of the housing and / or the distal end region of the catheter include one or more radial through-holes. The radial through-holes can increase elasticity, allowing the proximal bearing to be press-fit into the housing and / or catheter. The through-holes also allow for the introduction of glue and for position monitoring during insertion into the proximal bearing. Among other things, glue is used to seal the gap between the bearing and the housing to prevent leakage of the purge fluid; therefore, care must be taken to completely fill the gap. The radial through-holes can have a diameter of 0.5 mm to 1 mm. Slotted holes with circumferential extension can be advantageous for filling the notches in the bearing; in this case, the aforementioned diameter refers to the smaller diameter of the slotted hole.

[0014] Preferably, the highly flexible drive shaft includes a reinforcing element, preferably a coaxial, rigid reinforcing rod, extending longitudinally within the central lumen of the drive shaft. More specifically, in some embodiments, the drive shaft is reinforced by the reinforcing element in its distal end region. This is particularly advantageous when the drive shaft extends into, and in some embodiments, directly against, the distal end of the rotor. Thus, the reinforcing element can extend from a region proximal to the proximal bearing to the distal end of the drive shaft. The reinforcing element is preferably a metal rod, made of, for example, spring steel, metal wire, or carbon wire. In one embodiment, the metal wire is made of 1.4310 stainless steel.

[0015] The bearing sleeve may comprise a distally extending portion of the outer bearing ring, and the rotor may be attached to said distally extending portion of the outer bearing ring. Such a design may allow for a particularly stable configuration of the rotor. In particular, the bearing sleeve may extend along a majority of the axial length of the rotor, more preferably to the distal end of the rotor.

[0016] The rotor is preferably 0.001 mm to 8 mm from the distal surface of the outer bearing ring. A minimum distance between the rotor and the proximal bearing is desirable as this prevents the rotor from getting stuck on the proximal bearing.

[0017] Preferably, the rotor is additionally supported in a distal bearing.

[0018] The flexible shaft preferably extends throughout the entire catheter. The drive shaft is preferably hollow. The flexible drive shaft preferably consists of or comprises a flexible cable, preferably formed with differently oriented fiber layers. In particular, the flexible drive shaft most preferably comprises multiple coaxial windings, preferably with different winding directions, particularly preferably with alternating winding directions, running helically around an axially extending lumen along the drive shaft. For example, the flexible drive shaft can comprise two coaxial windings with opposite winding directions. The outer diameter of the drive shaft can preferably be 0.4 mm to 2 mm, more preferably 0.6 mm to 1.2 mm, and particularly preferably 0.8 mm to 1.0 mm. The proximal end of the flexible drive shaft is preferably attached to an extracorporeal electric motor. The flexible drive shaft serves to transmit torque from the electric motor to a rotor at the distal end of the drive shaft. In some cases, the flexible drive shaft may have a stiff, rigid shaft at its distal end to provide stability to the rotor, on which the rotor is mounted inside the housing.

[0019] In one embodiment, the flexible drive shaft comprises at least one outer layer and at least one inner layer. At least one outer layer of the flexible drive shaft is preferably absent or thinned in the area where the flexible drive shaft is supported in the proximal bearing. Thus, the drive shaft has a reduced diameter area, and at least the distal portion of the bearing sleeve, which forms a radial bearing together with the outer bearing ring, is located in that area. Preferably, the axial length of the area where at least one outer layer is absent or thinned is 1 to 15 times, preferably 2 to 5 times, e.g., 2 mm to 5 mm, the diameter of the drive shaft in that area.

[0020] At least one outer layer and at least one inner layer are preferably made of metal. More preferably, all layers may be made of metal. In some embodiments, at least one inner layer and / or at least one outer layer may be a wire or cable. The outer layer and / or the inner layer may be made of a hollow metal pipe.

[0021] In some embodiments, at least one of the at least one outer layer and / or at least one of the at least one inner layer comprises or consists of wire wound into one or several windings. Each wire may comprise one or more strands, which may be twisted, for example. Instead of being wound in layers, the wire may preferably be braided, similar to the outer sheath of a kernmantle rope, for example. The windings of at least one inner layer or at least one outer layer may form a helix. Alternatively, some or all layers may each comprise two or more helices, preferably axially shifted, similar to a multiple-start thread. Different layers may have different handedness of the helices, for example, alternating handedness from one layer to the next adjacent layer. The wire may be made of metal or may include metal and additional materials, such as a surface coating.

[0022] Preferably, the flexible drive shaft is at least partially filled with a sealant that penetrates at least one inner layer. If the layer contains holes or is made of wire, the sealant may penetrate across the layer. In some cases, the layers, particularly the wire(s) of the flexible drive shaft, may be partially or completely filled with the sealant.

[0023] For example, the proximal bearing and / or the distal bearing are configured to be purged with a purge fluid. The purge fluid can reduce friction and transport frictional heat away from the proximal bearing. It can also prevent blood from entering through the bearing gap. If the purge fluid can flow through the flexible drive shaft in addition to the bearing gap when passing through the proximal bearing, it is difficult to create a defined purge fluid flow. Therefore, if the flexible drive shaft is filled with a sealant, purge fluid flow through the drive shaft can be prevented and a defined purge fluid flow through the proximal bearing can be facilitated.

[0024] When a flexible drive shaft is filled with a sealant inside the bearing sleeve, the flow of purge fluid through the bearing sleeve can be advantageously prevented. However, in some cases, a flexible drive shaft having several layers can be very difficult to completely fill with sealant. Residual flow of purge fluid through the flexible drive shaft can result. In some embodiments, there is only one inner layer, and the inner layer and at least one outer layer are made of wound wire. At the same time, at least one outer layer can be completely removed in place of the sleeve.

[0025] Alternatively, in designs with three or more outer layers, one or more outer layers can be removed so that only at least one inner layer remains. In this case, filling at least one inner layer inside the bearing sleeve with a sealant can be particularly effective in stopping flow through a highly flexible drive shaft, since the sealant does not need to penetrate the spaces between the layers to completely seal the inside of the bearing sleeve.

[0026] In another embodiment, the inner diameter of the bearing sleeve is approximately equal to the outer diameter of the at least one inner layer or the at least one thinned outer layer of the drive shaft. Preferably, the bearing sleeve is fixedly connected to the at least one inner layer or the at least one thinned outer layer of the flexible drive shaft. The outer diameter of the distal portion of the bearing sleeve is approximately equal to the outer diameter of the at least one outer layer. Thus, the inner radial bearing surface of the proximal bearing corresponds to the outer diameter of the drive shaft and may preferably be slightly larger than the at least one outer layer of the drive shaft to facilitate assembly of the device.

[0027] The at least one inner layer may be axially interrupted inside the bearing sleeve. If the at least one inner layer is axially interrupted inside the bearing sleeve, it may be particularly easy to secure the bearing sleeve onto the at least one inner layer. If there is no axially interrupted inner layer, the at least one inner layer may need to be fed through the bearing sleeve before the next subsequent section of the at least one outer layer can be provided on the at least one inner layer. This is particularly advantageous in embodiments in which the at least one inner layer extends distally beyond the proximal bearing.

[0028] In some embodiments, the internal space of the bearing sleeve is hydraulically separated, i.e., liquid may not flow from one side of the bearing sleeve to the other. In some embodiments, the bearing sleeve may be a cylinder with a wall separating two blind holes, rather than a cylinder with a through hole. In this case, two ends of the at least one axially disconnected inner layer may be inserted into each of the blind holes. The wall between the holes prevents any purge fluid from flowing through the bearing sleeve. As a result, the at least one axially disconnected inner layer does not need to be sealed, but is simply attached to the bearing sleeve.

[0029] In a preferred embodiment, only the distal portion of the bearing sleeve is attached to the drive shaft section having a reduced diameter, while the proximal portion has an increased inner diameter and extends proximally over at least one outer layer of the flexible drive shaft. This effectively reduces the risk of the drive shaft breaking due to a change in stiffness at the transition between different diameters. A distal protective ring, having essentially the same function, may be provided at the distal transition between different diameters and extend over both at least one outer layer of the flexible shaft and the distal extension of the portion of the bearing sleeve.

[0030] The proximal bearing with the bearing sleeve and the distal protective ring can preferably be assembled as follows: At least one inner layer and at least one outer layer of the drive shaft can be mechanically separated from each other, or can be attached during production so that the at least one inner layer protrudes from the at least one outer layer. After mechanically separating the at least one outer layer from the inner layer, the at least one outer layer is peeled off from the inner layer while slightly rotating. A distal portion of the bearing sleeve is positioned over the at least one outer layer of the drive shaft so that its longer portion is mechanically or otherwise fixed to the at least one outer layer of the drive shaft. A shorter portion of the distal portion of the bearing sleeve overlaps the at least one inner layer of the drive shaft. A low-viscosity adhesive is then dispensed into the overlapping area and used to glue the distal portion of the bearing sleeve onto the at least one inner layer of the drive shaft. The distal end portion of the bearing sleeve is positioned so that it reaches into and overlaps the proximal portion of the bearing sleeve. After the adhesive has hardened, the drive shaft and bearing sleeve combination can be tested for liquid impermeability. An outer bearing ring is then positioned over the distal portion of the bearing sleeve. The previously removed at least one outer layer is pressed against the at least one inner layer until it contacts the bearing sleeve and is glued in place. A distal protective ring is then placed over the previously removed at least one outer layer so that it overlaps the distal portion of the bearing sleeve. The distal protective ring is positioned so that a predetermined axial play is set between the outer bearing ring and the bearing sleeve. The distal protective ring is then mechanically or otherwise secured to the drive shaft. Securing the protective ring over the at least one outer layer may additionally prevent loosening of the at least one outer layer. Thus, both the distal protective ring and the proximal portion of the bearing sleeve surround the end of the at least one outer layer adjacent to the bearing sleeve.

[0031] As a result, the proximal portion of the bearing sleeve is axially positioned between the outer bearing ring and the limiting member, which, as described above, acts as a limit to restrict axial movement of the drive shaft relative to the outer bearing ring. In one embodiment, a rotor or rotor shaft mounted distally of the outer bearing ring may form a protective ring, in which case the limiting member advantageously prevents contact of the rotor or rotor shaft with the outer bearing ring.

[0032] Preferably, the protective ring and / or the proximal portion of the bearing sleeve are fixedly connected to the flexible drive shaft. The protective ring is preferably crimped, soldered, welded, glued or shrink fitted to the at least one outer layer and / or to the bearing sleeve.

[0033] Preferably, the guard ring comprises one or more ceramics and / or metals, in particular MP35, 35NLT, Nitinol, or stainless steel. If metal, the guard ring may be hard-coated, for example DLC-coated.

[0034] The surface of the proximal portion of the bearing sleeve facing the bearing ring preferably forms an axial bearing with the opposite surface of the bearing ring. The distal protective ring preferably forms a stop element for the bearing ring to prevent it from sliding off the bearing sleeve.

[0035] Preferably, two different adhesives are used in the drive shaft. The first adhesive is preferably used to penetrate at least one outer layer and / or at least one inner layer, particularly their outer and / or inner windings. The first adhesive may be a sealant. The first adhesive preferably has a particularly low viscosity so that it can completely penetrate the outer and / or inner windings. The first adhesive preferably has a viscosity in the range of 80 cPs to 200 cPs before curing. A suitable adhesive is a two-component epoxy resin. A different second adhesive is preferably used to connect the sleeve and / or distal protective ring to the flexible drive shaft. Preferably, the first adhesive has a lower viscosity than the second adhesive. The second adhesive preferably has a medium or paste-like viscosity. A suitable adhesive is a two-component epoxy resin.

[0036] According to a particularly preferred embodiment, the bearing sleeve extends into the rotor, and is often stiffer than the drive shaft so that the rotor may have a stiffer support compared to other embodiments in which the rotor is attached to the distal end of the drive shaft.

[0037] Preferably, the radial bearing gap between the outer bearing ring and the bearing sleeve is 1 μm to μm wide, more preferably 2 μm to 8 μm wide, more preferably approximately 3.5 mm wide.

[0038] The intravascular blood pump may further include a distal bearing for rotatably supporting the distal end of the rotor. The distal bearing is located either inside or distal to the rotor. Preferably, the distal bearing includes a static support member that protrudes into or facing the distal end of the rotor. Alternatively, the distal end of the drive shaft or bearing sleeve may be supported by the distal bearing.

[0039] In another embodiment, the drive shaft is not supported in the distal bearing. Instead, the rotor is mounted on the distal end of the drive shaft, or on the distal extension of the proximal bearing sleeve, respectively, such that the distal end of the rotor is supported by a static support member that preferably extends into or against the rotor. In this way, the tendon structure is less likely to get caught on the rotating part, especially if the rotating structure does not extend beyond the tips of the rotor blades. This may lead to a safer intravascular blood pump with a longer lifespan.

[0040] The intravascular blood pump is preferably designed as an expandable blood pump with a housing having an expandable section. In some embodiments, the housing comprises or consists of a shape-memory material, particularly nitinol. The diameter of a percutaneously insertable blood pump is generally limited by the inner diameter of the smallest blood vessel to be traversed. The intravascular blood pump can be moved through the vessel with the housing in a collapsed state. Upon reaching the heart or a larger vessel, the housing of the intravascular blood pump can be expanded. This allows for the percutaneous insertion of a larger blood pump into the heart than would otherwise be possible. Such a larger blood pump may be capable of generating a higher blood flow rate.

[0041] When the blood pump is designed as an expandable pump, a cannula is preferably provided around a portion of the drive shaft proximal to the rotor, and the housing and rotor are configured to be transferred at least partially into the cannula. During such transfer, the expandable section of the housing and rotor are compressed from an expanded state to a compressed state at least along a radial direction extending transverse to the longitudinal direction. Preferably, portions of the rotor, such as the rotor blades, or the entire rotor, are also expandable to allow a larger rotor to be inserted into the heart, which can improve flow rate.

[0042] In some embodiments, the static support member of the distal bearing protrudes facing the distal end of the rotor. Compared to embodiments in which the static support member protrudes into the rotor, a particularly flexible pump section of the intravascular blood pump can be created. The high flexibility of the pumping device is particularly advantageous during insertion and removal of the intravascular blood pump. If the static support member did not protrude into the rotor but instead simply rested facing the distal end of the rotor, it could be intentionally disengaged from the rotor as the pump section flexes during operation of the pumping device through a blood vessel. When the pump section reaches its final destination inside the heart, it can straighten, and the static support member can resume its position where it protrudes facing the distal end of the rotor.

[0043] Preferably, a static support member is attached to the distal end of the housing, and expansion of the housing can provide an axial force onto the distal end of the rotor via the static support member. Preferably, the force is 1.8 N or less. When the static support member protrudes against the distal end of the rotor, it can limit further expansion of the housing.

[0044] When the housing is compressed, the static support member preferably moves away from the distal end of the rotor. In this state, the pump section is more flexible because relative radial movement of the static support member and rotor is permitted, which can be advantageous during insertion or retrieval of the intravascular blood pump.

[0045] In certain embodiments, the intravascular blood pump includes a nose portion at the distal end of the rotor. When the housing is in an expanded state, the nose portion protrudes into the static support member, which preferably has a correspondingly formed recess. The nose portion serves the purpose of centering the rotor's rotation and ensuring the correct relative positioning of the rotor and static support member after expansion of the housing. The nose portion protrudes above the peripheral surface of the rotor by preferably 0.1 mm to 2 mm, more preferably 0.2 mm to 1 mm, and most preferably 0.3 mm to 0.5 mm. The depth of the recess in the static support member corresponds to the nose portion and is preferably 0.1 mm to 2 mm, more preferably 0.2 mm to 1 mm, and most preferably 0.3 mm to 0.5 mm.

[0046] In some embodiments in which the static support member protrudes into the rotor, the rotor includes an axial stop for the static support member, such as a recess at its distal end having a base or step. The base or step defines an axial stop for the proximal end of the static support member at the distal end of the rotor. This is particularly advantageous in the context of an expandable blood pump. In its expanded state, the proximal end of the static support member protruding axially into the rotor can be in contact with the axial stop, thereby preventing further expansion of the housing and thus limiting the radial gap width between the outer edge of the rotor blades and the inner surface of the expandable housing. Alternatively, in the expanded state of the expandable blood pump, the proximal end of the static support member and the axial stop can form a gap that is preferably 0.01 mm to 1 mm, more preferably 0.01 mm to 0.1 mm, and most preferably 0.01 mm to 0.05 mm in width in the axial direction.

[0047] The length of the recess at the distal end of the rotor, measured axially, is, for example, 0.5 mm to 8 mm, preferably 1 mm to 5 mm, and particularly preferably 1.5 mm to 2.5 mm. When the housing is moved into the cannula, it preferably extends axially by 0.5 mm to 2.5 mm, more preferably 1 mm to 2 mm, and most preferably approximately 1.7 mm.

[0048] Inside the distal end of the drive shaft, i.e., inside the rotor shaft, the intravascular blood pump may include an optional fluid line arranged to guide purge fluid through the rotor to the distal bearing. In some embodiments, the rotor includes a hollow section as part of the fluid line, and the intravascular blood pump is arranged to guide purge fluid through the hollow section of the rotor to the distal bearing. The purge fluid may be transported to the fluid line via a catheter. The purge fluid may enter the catheter and / or drive shaft inside the housing of the electric motor. The purge fluid may flow inside the catheter adjacent to the drive shaft. If the drive shaft is hollow, the purge fluid may flow partially, mainly, or entirely through the drive shaft lumen. The purge fluid may flow through the drive shaft from the distal end of the catheter to the rotor. The drive shaft may include a cover at least in the space between the distal end of the catheter and the proximal end of the rotor to prevent purge fluid from leaking from the space.

[0049] Alternatively, the purge fluid may not be directed through the main lumen of the catheter, including the drive shaft, but rather through one or more separate secondary lumens.

[0050] In the distal end region of the catheter, the purge fluid preferably travels into the fluid lines inside the rotor shaft. In some cases, the rotor shaft or rotor hub may have a central lumen to accommodate the fluid lines. In particular, in the case of a hollow drive shaft, the drive shaft may extend into the rotor to form both the rotor shaft and the fluid lines, or the hollow drive shaft may be extended by a hollow tube to form both the rotor shaft and the fluid lines. Alternatively, a distal extension of the bearing sleeve of the proximal bearing may form the hollow drive shaft. The hollow drive shaft may be permeable to the purge fluid in some locations.

[0051] In purged proximal and / or distal bearings, blood is less likely to enter the bearing gap. As a result, blood clots are prevented. Additionally, purged bearings may have less friction than alternative bearings in the prior art. In particular, the purging fluid can lubricate the bearing and transport frictional heat away from the bearing. This may enable higher rotational speeds, lower power consumption, and increased lifespan of the blood pump. The purging fluid may be any biocompatible fluid suitable for purging bearings. Examples of suitable medical fluids include saline, glucose solution, and / or water, each with or without heparin.

[0052] In an alternative embodiment, the proximal and / or distal bearings are not purged, and therefore there is no delivery of purge fluid to the proximal and / or distal bearings, and the intravascular blood pump may not include fluid lines.

[0053] The distal bearing is preferably positioned to allow purge fluid to exit between the static support member and the distal end of the rotor into or facing the static support member. Preferably, the distal bearing is positioned so that purge fluid flows from the distal end of the fluid line to the distal bearing. In particular, the intravascular blood pump may be configured so that any purge fluid passing through the hollow drive shaft or rotor shaft exits, in whole or in part, through the distal bearing. By applying a suitable pressure, the purge fluid can be forced through a bearing gap in the distal bearing, which in some embodiments is a gap surrounded by the static support member and adjacent areas of the rotor. Preferably, the pressure of the purge fluid is in the range of 300 mmHg (0.4 bar) to 1500 mmHg (2 bar), more preferably in the range of 600 mmHg (0.8 bar) to 1100 mmHg (approximately 1.5 bar). When the distal bearing is purged and the rotor includes a nose portion that protrudes into the static support member, the nose portion may include at least one opening to allow purge fluid to enter the bearing gap between the nose portion and the static support member.

[0054] In some embodiments, the distal end of the static support member is attached to the distal end of the housing, which can provide stable support for the static support member that supports the distal end of the rotor.

[0055] The static support member preferably includes a pin extending from distal to proximal and projecting into, or preferably into, the distal end of the rotor. The pin may thus be positioned to form a distal bearing for the rotor. In embodiments in which the distal bearing is purged, the pin is preferably positioned to allow purge fluid to exit between the pin and the rotor attached to it.

[0056] Preferably, the pins have a circular cross-section. However, other cross-sections are equally possible for the distal portion of the pin located outside the rotor. For example, the pins may have an oval cross-section. In some embodiments, the pins may be hollow. Alternatively, the pins may be made of a solid material. Preferably, the pins are tapered toward their proximal ends. The pins may preferably be resiliently bendable so that the rotor remains concentric relative to the housing during flexion of the pump head.

[0057] Preferably, the inner diameter at the distal end of the rotor where the static support members, in particular the pins, protrude axially inward is between 0.3 mm and 1.5 mm, more preferably between 0.5 mm and 1.2 mm, and most preferably between 0.7 mm and 0.9 mm wide. Preferably, the radial bearing gap between the outside of the pin and its opposite bearing surface is between 1 μm and 10 μm wide, more preferably between 2 μm and 8 μm wide.

[0058] In some embodiments, the pin is particularly long, protruding into the rotor and extending proximally through the entire rotor. Preferably, the pin exits the rotor proximally and continues inside the drive shaft, terminating, for example, inside the proximal bearing. In this case, the end of the pin may be located inside the portion of the drive shaft that is positioned in the proximal bearing. By employing a long pin that extends through the entire length of the rotor and into the proximal bearing, a particularly stiff, low-vibration pump may be created. Alternatively, the pin may extend further to a point proximal to the proximal bearing. Pins that extend through the rotor may or may not be purged and may be used in conjunction with hollow drive shafts or drive shafts that are hollow along only a portion of their length.

[0059] Preferably, the material of the pin comprises at least one of the following materials: a biocompatible material, in particular one or more of MP35N, 35NLT, Nitinol, stainless steel (in particular medical grade stainless steel), and ceramics. The surface of the pin may comprise a coating, for example a hard coating, for example a diamond-like carbon (DLC) coating.

[0060] Preferably, the length of the pins that protrude into the distal end of the rotor during operation of the intravascular blood pump is 0.5 mm to 8 mm, preferably 1 mm to 5 mm, and particularly preferably 1.5 mm to 2.5 mm. The longer the protruding length, the stiffer the rotor support, and therefore the better the width of the gap between the outer edge of the rotor blades and the inner surface of the housing can be controlled. The blades must not contact the inner surface of the housing, and the gap must be large enough to prevent blood damage. A more stiffly supported rotor can also be operated with lower deflection and less vibration, which improves hemocompatibility.

[0061] The pins may have a sufficient length to remain within the distal end of the rotor when the housing and rotor are in a compressed state. The length of the pins that remain inside the distal end of the rotor when the housing and rotor are in a compressed state is preferably greater than 1.5 mm, more preferably greater than 1.7 mm, and most preferably greater than 2 mm. When the housing and rotor are compressed prior to deployment of the blood pump, the housing is longitudinally extended, and the static support members, particularly the pins, that extend into the distal end of the housing may possibly slip out entirely from the rotor. Then, when the housing is expanded again, the pins may not return into the rotor, and the pump may not be functional. Therefore, such problems can be avoided if the pins are selected with a sufficient length so that they remain inside the rotor even in the compressed state of the housing.

[0062] In embodiments involving pins, the distal bearing surface is the surface of the pin as well as the distal outer bearing surface, which may be provided by the rotor itself or by a distal bearing sleeve within the hub of the rotor. In some cases, the distal outer bearing surface may be provided by the stiffening element mentioned above.

[0063] The distal bearing sleeve may preferably have an inner diameter ranging from 0.3 mm to 1.5 mm, more preferably from 0.5 mm to 1.2 mm, and most preferably from 0.7 mm to 0.9 mm.

[0064] In some embodiments, the intravascular blood pump includes a flexible atraumatic tip to avoid damage to the patient's tissue. The atraumatic tip may be made of a flexible medical-grade polymer such as Pebax® or polyurethane. Preferably, the flexible atraumatic tip is designed as a pigtail or in a J-shape. According to a second aspect of the present invention, the intravascular blood pump described above is used intrapatiently, i.e. it is inserted inside the patient and operated therein to assist blood flow.

[0065] The invention will now be described, by way of example only, with reference to the accompanying drawings, which are not drawn to scale. In the drawings, identical or corresponding components illustrated in various figures are represented by the same numerals. For clarity, not every component is numbered in every figure. [Brief explanation of the drawings]

[0066] [Figure 1] 1 is a schematic diagram of an intravascular blood pump positioned within the left ventricle of the heart. [Figure 2] 1 is a schematic diagram of an intravascular blood pump. [Figure 3A] 1A-1C are schematic diagrams of an intravascular blood pump in expanded and compressed states. [Figure 3B] 1A-1C are schematic diagrams of an intravascular blood pump in expanded and compressed states. [Figure 4A] 1 is a schematic diagram of an intravascular blood pump according to a first embodiment with a static support member extending into the distal end of the rotor. FIG. [Figure 4B] 1 is a schematic diagram of an intravascular blood pump according to a first embodiment with a static support member extending into the distal end of the rotor. FIG. [Figure 4C] 1 is a schematic diagram of an intravascular blood pump according to a first embodiment with a static support member extending into the distal end of the rotor. FIG. [Figure 5] 10 is a schematic diagram of an intravascular blood pump according to a second embodiment with a static support member extending into the distal end of the rotor. FIG. [Figure 6A] 10 is a schematic diagram of an intravascular blood pump with a rotor having a nose at its distal end according to a third embodiment. FIG. [Figure 6B] 10 is a schematic diagram of an intravascular blood pump with a rotor having a nose at its distal end according to a third embodiment. FIG. [Figure 6C] 10 is a schematic diagram of an intravascular blood pump with a rotor having a nose at its distal end according to a third embodiment. FIG. [Figure 6D] 10 is a schematic diagram of an intravascular blood pump with a rotor having a nose at its distal end according to a third embodiment. FIG. [Figure 7] FIG. 1 is a schematic diagram of an intravascular blood pump with proximal and distal bearings. [Figure 8A] FIG. 1 is a schematic diagram of the path of purge fluid within an intravascular blood pump. [Figure 8B] FIG. 1 is a schematic diagram of the path of purge fluid within an intravascular blood pump. [Figure 9A] FIG. 1 shows a drive shaft with an outer layer and an inner layer. [Figure 9B] FIG. 1 shows a drive shaft with a bearing sleeve, an outer bearing ring and a protective ring. [Figure 10A] FIG. 1 shows a hydraulically split bearing sleeve. [Figure 10B] FIG. 1 shows a bearing with a restricting member. [Figure 11A] FIG. 1 shows a bearing with a restrictor member and a rotor. [Figure 11B] FIG. 1 shows a bearing with a restrictor member and a rotor. [Figure 12A] 1A-1C show two different embodiments of a proximal bearing with an outer bearing ring and a specially formed bearing sleeve. [Figure 12B] 1A-1C show two different embodiments of a proximal bearing with an outer bearing ring and a specially formed bearing sleeve. [Figure 13A] FIG. 1 illustrates a hydrodynamic axial bearing. [Figure 13B] FIG. 1 illustrates a hydrodynamic axial bearing. [Figure 13C] FIG. 1 illustrates a hydrodynamic axial bearing. [Figure 13D] FIG. 1 illustrates a hydrodynamic axial bearing. DETAILED DESCRIPTION OF THE INVENTION

[0067] FIG. 1 illustrates the use of an intravascular blood pump 1 to support, in this particular example, the left ventricle 2 of a human heart. The intravascular blood pump 1 includes a catheter 5 and a pumping device, the pumping device including a pump section 4 attached to the distal end region of the catheter 5. The intravascular blood pump 1 may be placed inside the heart using a percutaneous transluminal technique. For example, the intravascular blood pump 1 may be introduced through the femoral artery. However, alternative vascular access, such as access through the subclavian artery, is also possible. After passing through the femoral artery, the catheter 5 may be pushed into the aorta such that the pump section 4 passes through the aortic valve and into the heart. The positioning of the pump section 4 in FIG. 1 serves merely as an example; different arrangements are possible, such as positioning the pump section 4 inside the right ventricle of the heart.

[0068] The pump section 4 includes a rotor 10 for driving blood from a blood inlet 6 at the distal end of the pump section 4 to a blood outlet 7 located proximal to the blood inlet 6. The catheter 5 houses a drive shaft 12 driven by an electric motor 8, preferably located outside the patient's body. The drive shaft 12 drives a rotor contained inside the pump section 4. At its distal end, the pump section 4 possesses a flexible atraumatic tip 9 having a pigtail or J-shaped configuration, which facilitates placement of the intravascular blood pump 1 by aiding in navigation inside the patient's vasculature. Furthermore, the softness of the flexible atraumatic tip 9 allows the pump section 4 to stand free and unimpaired against the wall of the left ventricle 2.

[0069] FIG. 2 shows intravascular blood pump 1 in further detail. Rotor 10 is located inside housing 11. In this embodiment, both rotor 10 and housing 11 are compressible. In this case, intravascular blood pump 1 is transported through a patient's vascular system while both rotor 10 and housing 11 are in a compressed state. When pumping section 4 reaches its target location, housing 11 and rotor 10 are expanded. A flexible, atraumatic tip 9 is positioned at the distal end of housing 11. Drive shaft 12 is realized as a drive shaft cable. Drive shaft 12, with rotor 10 disposed at its distal end, can be seen protruding from the distal end of catheter 5. As rotor 10 inside housing 11 is rotated by drive shaft 12, blood is transported into blood inlet 6 at the distal end of housing 11 and through housing 11 into downstream tubing 20 attached to and extending proximally to housing 11. The blood then exits the downstream tubing 20 and is expelled into the aorta through a more proximal blood flow outlet 7 provided within the downstream tubing 20, which includes multiple outlet openings. The downstream tubing 20 is made of a highly flexible material so that it can be compressed by the aortic valve when the patient's heart is beating. The downstream tubing 20 typically expands primarily due to the active blood flow generated by the rotating rotor 10. By locating the blood flow inlet 6 inside the left ventricle 2 and the blood flow outlet 7 inside the aorta, the intravascular blood pump 1 can support the patient's systemic blood circulation. If the intravascular blood pump 1 were configured and positioned differently, it could, for example, be used to support the patient's pulmonary blood circulation instead.

[0070] In this example, a liquid, specifically a purge fluid, is supplied to the pump section 4 from outside the patient's body through a catheter 5. Inside the pump section 4, the liquid may be used to purge one or more bearings to reduce friction and cool the pump section 4, as further described in connection with FIGS. 4 and 5. Preferably, the liquid is used to purge at least the distal bearing. In such a case, the pressure of the purge fluid is selected to be higher than the patient's blood pressure to prevent blood from entering the bearings. Preferably, the pressure of the purge fluid is in the range of 300 mmHg (0.4 bar) to 1500 mmHg (2 bar), more preferably in the range of 600 mmHg (0.8 bar) to 1100 mmHg (approximately 1.5 bar).

[0071] Housing 11 is preferably fabricated from a shape memory material such as nitinol and provides a cage around rotor 10. As seen in Figure 5, the central portion of housing 11 holds a sleeve that defines a channel through which blood is pumped by rotor 10. Proximal and distal to this channel, housing 11 allows blood to be drawn into housing 11 and pushed out of housing 11 into downstream tubing 20 (as shown in Figure 2).

[0072] 3A and 3B show the pump section 4, its rotor 10, and its housing 11 in expanded and compressed states, respectively. A cannula 16 is disposed at the distal end of the catheter 5. Initially, prior to deployment of the intravascular blood pump 1, the pump section 4 is provided in its compressed state inside the cannula 16. The cannula 16 may be a cannula 16 attached to the catheter 5 or a peel-away sheath to aid in insertion of the catheter 5 into the patient's body. When the physician determines that the catheter 5 is properly positioned inside the patient's vasculature, the physician pushes the housing 11 out of the cannula 16. When the cannula 16 is removed, the housing 11 expands due to its shape-memory properties. Simultaneously, the rotor 10 expands due to its elasticity. As the housing 11 expands radially away from the drive shaft 12, it contracts longitudinally.

[0073] Rotor 10 is supported within a distal region of rotor 10 by distal bearing 14, which includes static support member 18 having pin 19 attached to housing 11 at one end and extending into the distal end of rotor 10 at its opposite end by pin 19, so that pin 19 can move axially inside rotor distal end 10 upon expansion of housing 11. Preferably, pin 19 is long enough to remain inside rotor 10 when housing 11 is in its compressed state. When intravascular blood pump 1 is in its expanded state and needs to be removed from the heart, the physician pulls housing 11 back into cannula 16, thereby radially compressing housing 11 and longitudinally extending it, so that the distal end of housing 11 moves away from rotor 10 along with static support member 18 and its pin 19, which extends into the distal end of rotor 10. The smaller diameter of the housing 11 thus achieved facilitates removal of the intravascular blood pump 1 from the patient.

[0074] In prior art distal bearings 14, the drive shaft 12 sometimes extends distally of the rotor 10 and into the distal bearing. However, this can cause the cardiac chordae tendineae to become entangled with the drive shaft 12, potentially leading to clotting and device failure. Therefore, the use of a static support member 18 as part of the distal bearing 14 that does not involve rotating portions distal to the rotor 10 and distal to the rotor blades is advantageous.

[0075] 4A and 4B illustrate in further detail the pump section 4 according to the first embodiment, including the housing 11 and the rotor 10 driven by the drive shaft 12. The drive shaft 12 is rotatably supported in both a proximal bearing 13 at the distal end of the catheter 5 proximal to the rotor 10 (or within the proximal portion of the housing), and in a distal bearing 14 located at the distal end of the rotor 10. In FIG. 4A, the drive shaft 12 is hollow at its distal end, or more specifically, the rotor shaft is hollow to form a fluid line 15 through which purge fluid can be pumped towards the distal bearing 14. If the drive shaft is hollow and extends to the distal end of the rotor 10, the rotor 10 can be formed directly at the distal end of the drive shaft 12 such that the rotor shaft is formed by the drive shaft, whereby in the regions of the proximal and distal bearings, the drive shaft 12 can be stiffened, for example by injection-molded plastic material, and provided with appropriate outer and inner bearing surface finishes, respectively. Alternatively, the entire end region of the drive shaft 12, including the bearing section, can be stiffened to obtain a stiffer pump section. For example, the drive shaft 12 can be thinned at its distal end, and a stiff hollow tube can be placed over the thinned end and extended distally to form the rotor shaft and bearing section. Purge fluid can be transported to the distal bearing 14 through a fluid line 15 within the rotor shaft. In the embodiment shown in FIG. 4A, the purge fluid is forced through the central fluid line 15, exits the drive shaft 12 at its distal end, and further through the bearing gap of the distal bearing 14 and into the bloodstream. Purging the distal bearing 14 with purge fluid results in less friction and therefore less wear on the distal bearing, and also prevents blood from entering and clogging the bearing gap.

[0076] For an intravascular blood pump 1 to be efficient, a large rotor diameter is desirable. However, as the clearance between the rotor 10 and the housing 11 decreases, the risk of damage to blood cells or the rotor 10 increases. If only the proximal bearing 13 is used, the system may vibrate, and the clearance between the tips of the rotor 10 blades and the inner surface of the housing 11 may undergo significant changes. When the flexible, atraumatic tip 9 contacts the heart wall, heart movement can cause the housing to bend, which can lead to the housing contacting the rotor. Contact between the housing and rotor during use can cause significantly increased damage to blood cells and can also cause wear due to particles from the housing and / or rotor entering the bloodstream. As illustrated in Figures 4A and 4B, by using both the proximal bearing 13 and the distal bearing 14, the position of the rotor 10 is more stable, and the variation in the size of the clearance is lower than with only one bearing. For a given housing 11, this can allow the rotor 10 diameter to be larger, thereby enabling a higher flow rate of the intravascular blood pump 1 without the housing contacting the rotor.

[0077] At its distal end, rotor 10 includes a recess 17. A static support member 18, which is fixed to the distal end of housing 11, projects into recess 17 by its pin 19. The bottom 19 of recess 17 in FIG. 4A is formed as a step and defines an inner stop for rotor 10 against which pin 19 of static support member 18 can rest. In FIG. 4A, fluid line 15 passes through the bottom of recess 17 to allow purge fluid to exit distal bearing 14 between pin 19 and recess 17.

[0078] The embodiment of intravascular blood pump 1 in FIG. 4B is similar to the embodiment in FIG. 4A. Importantly, however, the distal bearing in FIG. 4B is not purged but instead is designed to operate in blood. Therefore, drive shaft 12 does not need to be hollow. Thus, fluid line 15 is absent in FIG. 4B. The bottom of recess 17 does not include an opening for purge fluid to flow through the bearing gap between pin 19 and recess 17. In such an embodiment, less purge fluid may be required. If the proximal bearing is not purged, the intravascular blood pump may not require purge fluid at all.

[0079] 4A and 4B, in which the pin 19 is particularly long and extends proximally through the rotor shaft and into the drive shaft 12. In the embodiment of FIG. 4C, the proximal end of the pin 19 is located inside the portion of the drive shaft 12 that is located inside the proximal bearing 13.

[0080] In alternative embodiments, the proximal end of pin 19 may be located, for example, proximal to proximal bearing 13 or between rotor 10 and proximal bearing 13. By having pin 19 extending into proximal bearing 13, greater stiffness of intravascular blood pump 1 may be achieved. Furthermore, pin 19 shown in FIG. 4C may help reduce vibration of intravascular blood pump 1 during its operation and may reduce undesired flexing.

[0081] The proximal bearing 13 in Figure 4C is located inside the housing 11, distal to the location of the proximal bearing 13 in Figures 4A and 4B. The distance between the proximal bearing 13 and the rotor 10 is particularly small in the embodiment shown, e.g., smaller than the outer diameter of the proximal bearing 13. The short distance may further increase the stiffness of the intravascular blood pump 1.

[0082] The pin 19 in Figure 4C may, in some embodiments, be combined with a hollow drive shaft 12 so that purge fluid can flow through the drive shaft 12, past the pin 19, and exit at the distal end of the rotor 10. Alternatively, in some embodiments, purge fluid may not be used. In this case, the long pin 19 of Figure 4C may be combined with a drive shaft that is hollow only along some portion of its length.

[0083] FIG. 5 shows a pump section 4 according to a second embodiment, again with a rotor 10 driven by a compressible housing 11 and a hollow drive shaft 12. The hollow drive shaft 12 is rotatably supported in a proximal bearing 13 disposed proximal to the rotor 10 at the distal end of the catheter 5. In this embodiment, the pin 19 of the static support member 18, which forms part of the distal bearing 14, has a pointed end. If the dimensions of the housing 11 and pin 19 are such that the pin 19 exits the rotor 10 when the housing 11 is compressed, the pointed end of the pin 19 facilitates re-introduction of the pin 19 into the opening at the distal end 10 of the rotor when the housing 11 is again expanded. Preferably, the pin 19 is long enough to remain inside the rotor 10 when the housing 11 is in its compressed state. This can avoid a situation where the pin 19 cannot re-enter the rotor 10 when the housing 11 is expanded. In some cases, proper functioning of the required bearing clearance over the entire length of the pin 19 is not necessary. Rather, it is sufficient that the bearing gap between the outside of the pin 19 and the opposite bearing surface is between 1 μm and 10 μm, more preferably between 2 μm and 8 μm wide, at least in one location.

[0084] In this embodiment, rather than providing a bottom or step in the opening at the rotor's distal end 10, the static support member 18 may be provided with a shoulder against which the rotor 10 abuts in the expanded state of the housing 11, thereby limiting further expansion of the housing 11, if desired. In some embodiments, the distal bearing 14 may be exclusively a radial bearing.

[0085] Again, purge fluid is supplied through fluid line 15 of drive shaft 12 toward distal bearing 14, passes through pins 19 that form the distal radial bearing for rotor 10, and can exit rotor 10 at its distal end. This prevents blood from entering rotor 10, reduces friction, and cools distal bearing 14. Alternatively, distal bearing 14 may not be purged; therefore, fluid line 15 may not be present.

[0086] Furthermore, in the embodiment shown in Figure 5, the pin 19 is inside the central duct of the rotor 10 when the housing 11 is expanded. In this case, for example, the drive shaft 12 may terminate at the distal end face of the rotor 10. Alternatively, the distal end of the drive shaft 12 may be located inside the rotor 10, for example at the level of the bottom of the recess, as can be seen in the embodiment of Figure 4, so as to form a stop for the pin 19.

[0087] FIGS. 6A, 6B, 6C, and 6D show a third embodiment of a pump section 4 with a compressible housing 11 and a static support member 18 attached to the housing 11. The rotor 10 includes a nose portion 21 at its distal end. In FIGS. 6A, 6B, and 6C, the fluid line 15 inside the distal end of the drive shaft 12 leads to an opening in the nose portion 21 through which purge fluid can enter the bearing gap of the distal bearing 14 between the nose portion 21 and a corresponding recess 22 at the proximal end of the static support member 18. However, in FIG. 6D, the distal bearing 14 is not purged. Thus, the embodiment of FIG. 6D does not have a fluid line 15 and an opening in the nose portion 21. The non-purged distal bearing 14 may reduce the amount of purge fluid required to operate the intravascular blood pump 1. In combination with the non-purged proximal bearing 13, the intravascular blood pump 1 may not require any purge fluid at all.

[0088] When the housing 11 is compressed, the nose portion 21 disengages from the recess 22, thus making the intravascular blood pump 1 more flexible. When the housing 11 is expanded at the target site, the nose portion 21 automatically moves into the recess 22, and the conical, spherical, or otherwise converging shape of the nose portion 21 helps guide the nose portion 21 into the recess 22, centering the rotor 10 relative to the static support member 18. Figure 6b shows an enlarged cross-section of the distal bearing 14 with the nose portion 21 and corresponding recess 22 on the rotor 10. The vertical dashed-dotted line in Figure 6b indicates the cross-sectional plane of Figure 6C. The cross-section presented in Figure 6C displays the distal bearing 14 as concentric circles. From the periphery to the center, the concentric circles indicate the recess 22, the distal bearing gap between the recess 22 and the nose portion 21, the nose portion 21, and the opening of the fluid line 15 into the distal bearing gap.

[0089] FIG. 7 shows a schematic representation of an intravascular blood pump 1 with its catheter 5 and its pumping section 4. In this embodiment, the intravascular blood pump 1 includes a proximal bearing 13 inside the distal end of the catheter 5. Inside the proximal bearing 13, an inner bearing sleeve 24 is glued onto the drive shaft 12 to provide a smooth bearing surface. To accommodate the bearing sleeve 24, the drive shaft 12 has had some of its outer windings removed to reduce its diameter. Purge fluid can now flow through the catheter 5 and exit the proximal bearing 13 through the bearing gap. Some of the purge fluid also flows through the drive shaft 12 and into the rotor 10.

[0090] The proximal bearing sleeve 24 may have an inner diameter ranging preferably from 0.3 mm to 1.5 mm, more preferably from 0.5 mm to 1.2 mm, and most preferably from 0.7 mm to 0.9 mm.

[0091] The outer diameter of the bearing sleeve 24 of the proximal bearing is preferably 0.5 mm to 2 mm, more preferably 0.8 mm to 1.8 mm, and most preferably 0.9 mm to 1.2 mm. The bearing gap of the proximal bearing is preferably 1 μm to 10 μm, more preferably 2 μm to 8 μm.

[0092] From the drive shaft 12 inside the rotor, the purge fluid flows through fluid line 15 into recess 17 of rotor 10. Disposed inside recess 17 is the sleeve of distal bearing 25 of rotor 10. The inner surface of the sleeve of distal bearing 25 and the outer surface of pin 19 form the bearing surface of distal bearing 14. The purge fluid exits rotor 10 through the bearing gap between the sleeve of distal bearing 25 and pin 19.

[0093] The sleeve of the distal bearing 25 preferably has an inner diameter of 0.3 mm to 1.5 mm, more preferably 0.5 mm to 1.2 mm, and most preferably 0.7 mm to 0.9 mm. The outer diameter of the sleeve of the distal bearing 25 is preferably 0.5 mm to 1.7 mm, more preferably 0.7 mm to 1.4 mm, and most preferably 0.9 mm to 1.1 mm. The bearing gap between the pin 19 and the sleeve of the distal bearing 25 is preferably 1 μm to 10 μm, and more preferably 2 μm to 8 μm.

[0094] FIG. 8A shows a schematic diagram of a purge fluid path inside an intravascular blood pump. Inside the motor 8 housing, purge fluid is supplied into the catheter 5 and into the drive shaft 12. Here, the proximal bearing 13 is shown schematically, and its components, particularly the outer bearing ring 32 and bearing sleeve 30, are not shown. At the proximal bearing 13, the purge fluid exits the catheter 5 through a bearing gap to reduce friction and cool the proximal bearing 13. A portion of the purge fluid does not exit the catheter 5 through the bearing gap but flows through the drive shaft 12 into the rotor 10. In some embodiments, the drive shaft 12 may include a cover to allow purge fluid to flow from the catheter 5 to the rotor 10 without leaking from the drive shaft 12 between the distal end of the catheter 5 and the proximal end of the rotor 10. Inside the rotor 10, the purge fluid continues to flow through a fluid line 15 and then into a recess 17 at the rotor's distal end 10. In an alternative embodiment, the drive shaft 12 may continue up to or into the recess 17 such that the purge fluid flows from the drive shaft 12 directly into the recess 17. From there, the purge fluid flows through the bearing gap of the distal bearing 14 between the pin 19 and the adjacent surface of the rotor 10.

[0095] Figure 8B shows a blood pump embodiment similar to Figure 8A. In Figure 8B, the proximal bearing 13 is closer to the rotor 10 than in Figure 8A and is separated from the rotor 10 only by a small gap through which purge fluid can leak, as shown by the arrows.

[0096] 9A shows an example of a drive shaft 12 including one outer layer 28 and one inner layer 29. In this embodiment, the outer layer 28 and the inner layer 29 are made of helically wound wire, with the helix of the inner layer 29 being right-handed and the helix of the outer layer 28 being left-handed. As shown in FIG. 9A, a portion of the outer layer 28 has been removed from the inner layer 29 to show it separately. Removal of the portion of the outer layer 28 can be performed by pulling on the outer layer 28 while slightly rotating it. The bearing sleeve 30 can be pushed onto the exposed inner layer 29 until it abuts the outer layer 28, and this portion of the outer layer 28 can then be installed back onto the inner layer 29 adjacent the bearing sleeve 30.

[0097] 9B shows a highly flexible bearing shaft 12 with an outer layer 28 and an inner layer 29, where the outer layer 28 is not in a central location and the bearing sleeve 30 is positioned on top of the inner layer 29 in said central location. Additionally, on either side of and overlapping the bearing sleeve 30 are two protective rings 31 that fit over the ends of the outer layer 28 facing the bearing sleeve 30. A shorter portion of the protective ring 31 overlaps the bearing sleeve 30, while a larger portion covers the outer layer 28. In this way, the risk of breakage of the drive shaft due to changes in stiffness at the transition between smaller and larger shaft diameters is reduced.

[0098] During assembly, the outer layer 28 may be cut and removed from one end of the drive shaft 12. At this point, the drive shaft 12 resembles the view in FIG. 9A. A first protective ring 31 is then placed over the end of the remaining outer layer 28. A bearing sleeve 30 is then placed over the inner layer 29 from which the outer layer 28 was removed, overlapping the protective ring 31. An outer bearing ring 32 is placed over the bearing sleeve 30. The previously removed outer layer 28 is then reinstalled over the inner layer 29, with the second protective ring 31 overlapping the end of the outer layer 28 and the bearing sleeve 30. The bearing sleeve 30 and protective ring 31 may be attached to the drive shaft 12 using a low-viscosity adhesive. After the adhesive has set, the bearing sleeve 30 may be tested for cure, i.e., it may be tested for the ability of purge fluid to pass through the bearing sleeve 30.

[0099] The bearing sleeve 30 is rotatably supported within an outer bearing ring 32, which is fixed to the catheter or the proximal end of the housing in which the rotor is housed. The bearing sleeve 30 and outer bearing ring 32 form a radial bearing, while the guard ring 31 forms an axial stop and, in some embodiments, an axial bearing with the outer bearing ring 32. The bearing sleeve 30, together with the guard ring 31, may be constructed from a single piece of material. As mentioned, the bearing sleeve 30 and guard ring 31 are fixedly connected to the drive shaft 12, preferably by glue. Glue is also used to fill the windings of the inner layer 29 and outer layer 28 to prevent purge fluid from leaking through the drive shaft 12.

[0100] In this example, the inner diameter of the bearing sleeve 30 is approximately the same as the outer diameter of the inner layer 29. The outer diameter of the bearing sleeve 30 is approximately the same as the outer diameter of the outer layer .

[0101] FIG. 10A shows a hydraulically divided bearing sleeve 30 including a wall between two blind holes. The inner layer 29 is axially disconnected. Each blind hole of the bearing sleeve 30 receives a respective axial end of the axially disconnected inner layer 29. The bearing sleeve 30 does not allow any purge fluid to pass axially. Due to this, the inner layer 29 does not need to be filled with glue to prevent any flow of purge fluid through the inner layer 29. Glue can still be used to attach the inner layer 29 to the bearing sleeve 30, but alternative attachment techniques such as soldering, crimping, and welding are also possible. The outer bearing ring 32 rests on the bearing sleeve 30 and is prevented from being extruded from the bearing sleeve 30 by two protective rings 31. Again, the bearing sleeve 30, together with one of the protective rings 31, can be constructed from a single piece of material.

[0102] 10B shows another embodiment with an outer bearing ring 32 that forms a radial bearing together with the bearing sleeve 30. Furthermore, the proximal guard ring 31a and the distal guard ring 31b are axially fixed relative to the bearing sleeve 30 in the manner previously described. If the drive shaft 12 moves distally (to the left in FIG. 10B), the proximal guard ring 31a abuts the proximal surface of the outer bearing ring 32, preventing any further distal movement. If the drive shaft 12 moves proximally, the proximal guard ring 31a abuts the distal face of the limiting member 33, stopping any further movement in the proximal direction. The maximum distance a between the proximal surface of the distal guard ring 31b and the distal surface of the outer bearing ring 32 is max The minimum distance c between the distal surface of the restricting member 33 and the proximal surface of the proximal guard ring 31a is max , the distal guard ring 31b never contacts the outer bearing ring 32. This condition is equivalent to the inequality a>b+c, where b+c is a constant.

[0103] 11A, when the rotor 10 is mounted on the distal protection bearing 31b, distances a, b, and c selected according to the above inequality prevent the rotor from contacting the outer bearing ring 32. Similarly, and when the rotor 10 is mounted on the distal extension of the bearing sleeve 30, as shown in FIG. 11B, the above condition prevents the rotor 10 on the bearing sleeve 30 from contacting the outer bearing ring 32. Contact between the rotor 10 and the outer bearing ring 32 could otherwise cause damage to the rotor 10 or to the proximal bearing 13.

[0104] FIG. 12A shows an intravascular blood pump 1 with a rotor 10 attached to a housing 11 and a drive shaft 12. A proximal bearing 13 includes a bearing sleeve 30 rotatably supported within an outer bearing ring 32. The drive shaft 12 is glued into the bearing sleeve 30. The drive shaft 12 surrounds a reinforcing element 35, implemented as a coaxial rod, for stabilizing the distal end of the drive shaft. The rod extends from proximal to the proximal bearing 13 to the distal end of the rotor 10. Alternatively, the drive shaft 12 may be hollow to allow purge fluid to reach the distal bearing. A restricting member 33 is located proximal to the bearing sleeve 30 and prevents the bearing sleeve 30 from disengaging from the outer bearing ring 32. Both the restricting member 33 and the outer bearing ring 32 are press-fit and / or glued into the distal end of the housing 11. Additionally, the restricting member 33 is press-fit and / or glued into the catheter 5. Thus, the restricting member 33 connects the housing 11 and the catheter 5. The radial through-holes 34 in the housing 11 serve to introduce glue to fixedly connect the restricting member 33 and the outer bearing ring 32 to the housing 11. The glue may be distributed circumferentially along grooves 36 provided in both the restricting member 33 and the outer bearing ring 32. Furthermore, the radial through-holes 34 may be used to control the position of the outer bearing ring 32 and the restricting member 33. Both connections are glued to keep the connection tight and to prevent leakage of the purge fluid.

[0105] 12A , the bearing sleeve 30 includes a proximal portion 30a located proximal to the outer bearing ring 32 and a distal portion 30b extending distally from the proximal portion 30a into the outer bearing 32. The proximal portion 30a forms an axial bearing with the proximal surface of the outer bearing 32, while the distal portion 30b forms a radial bearing with the outer bearing ring 32. The axial bearing and the radial bearing together constitute the proximal bearing 13.

[0106] Purge fluid pushed from proximal to distal through the proximal bearing 13 first passes through the proximal portion 30a of the bearing sleeve 30 along its radially outer surface, then flows radially inward through a bearing gap between the distal surface of the proximal portion 30a and the proximal surface of the outer bearing ring 32, and finally flows further distally through a bearing gap formed radially between the distal portion 30b of the bearing sleeve 30 and the radially inner surface of the outer bearing ring 32. The bearing gap can be designed with little tolerance by applying a suitable pressure proximally to the purge fluid so that the purge fluid flows through the bearing gap in a closely controllable manner. Radial notches (not shown) can be provided on the proximal surface of the static outer bearing ring 32 to ensure that purge fluid can flow into the radial bearing gap between the outer bearing ring 32 and the distal portion 30b of the bearing sleeve 30 when the rotor 10 pulls the bearing sleeve 32 distally during operation.

[0107] Figure 12B shows an alternative embodiment to that of Figure 12A. Here, drive shaft 12 has a reduced diameter section, and distal portion 30b of bearing sleeve 30 is disposed in the reduced diameter section. In this manner, although not specifically shown in Figure 12B, the outer diameter of outer bearing ring 32 can be correspondingly reduced, and consequently, the outer diameter of catheter 5 can be similarly reduced. In this manner, a more flexible and more maneuverable catheter can be achieved.

[0108] The structure of the bearing sleeve 30 as shown in Figure 12B is comparable to the bearing structure as described above in connection with Figures 13-15. More specifically, the proximal portion 30a of the bearing sleeve 30 corresponds to the proximal protective ring 31a (see Figure 10B). Accordingly, a distal bearing ring 31b overlapping both the drive shaft 12 and the distal end of the distal portion 30b of the bearing sleeve 30 is also provided in the embodiment shown in Figure 12B. It limits axial movement of the shaft 12 within the outer bearing ring 32 in the same manner as described in connection with Figures 13-15.

[0109] FIG. 13A shows a graphic representation of the stationary surfaces of a hydrodynamic axial bearing. Specifically, FIG. 13A shows the proximal surface of the outer bearing ring 32 with the drive shaft 12 located in the center. The curved radial lines in FIG. 13A represent the raised portions of the bearing surfaces, which are shown in more detail in FIG. 13B. The arrows in FIGS. 13A and 13B illustrate the direction of counter surface movement, which then corresponds to the direction of lubricant film movement within the axial bearing gap. The surfaces have slopes that form a converging gap with the flat counter stationary surface. This causes hydrodynamic pressure to build up within the lubricant film, so that the surfaces forming the axial bearing gap remain spaced apart.

[0110] Figure 13C shows the inner bearing sleeve 30 and outer bearing ring 32 of the housing 11. The bearing sleeve 30 has a flat distal surface. Here, the opposing proximal surface of the outer bearing ring 32 is sloped to form a converging gap. In use, this creates the lubricating film required for hydrodynamic bearings.

[0111] 13D shows spiral grooves in another embodiment of the proximal bearing surface of the outer bearing ring 32. The spiral grooves are preferably configured in the moving surface of the proximal bearing 13, i.e., the proximal portion 30a of the bearing sleeve 30. In this case, several grooves are positioned in the shape of a spiral on the distal surface of the proximal portion 30a of the bearing sleeve 30. When the bearing sleeve 30 rotates in the direction indicated by the arrow in FIG. 13D, a lubricating film is transported radially inward along the grooves, creating pressure between the bearing surfaces and keeping them apart.

Claims

1. a catheter (5); a housing (11) in which a rotor (10) is housed, the housing (11) being attached to the distal end of the catheter (5); a flexible drive shaft (12) extending through the catheter (5) and connected to the rotor (10), the drive shaft (12) being rotatably supported in a proximal bearing (13) located proximal to the rotor (10); An intravascular blood pump (1) comprising: The proximal bearing (13) comprises a bearing sleeve (30) and an outer bearing ring (32); the bearing sleeve (30) comprises a proximal portion (30a) located proximal to the outer bearing ring (32), the proximal portion (30a) of the bearing sleeve (30) forming an axial bearing of the proximal bearing together with a proximal surface of the outer bearing ring (32); The intravascular blood pump (1) is characterized in that the bearing sleeve (30) has a distal portion (30b) extending distally from the proximal portion (30a) of the bearing sleeve (30) into the outer bearing ring (32), and the distal portion (30b) of the bearing sleeve (30) forms a radial bearing for the proximal bearing together with the outer bearing ring (32).

2. 2. An intravascular blood pump (1) according to claim 1, characterized in that the bearing sleeve (30) is fixedly connected to the highly flexible drive shaft (12).

3. 3. An intravascular blood pump (1) according to claim 1 or 2, characterized in that the outer bearing ring (32) is located inside the distal end region of the catheter (5) or inside the proximal end region of the housing (11).

4. 4. An intravascular blood pump (1) according to claim 1, characterized in that a limiting member (33) for limiting axial movement of the bearing sleeve (30) relative to the outer bearing ring (32) is located inside at least one of the catheter (5) and the housing (11) and proximal to the bearing sleeve (30).

5. An intravascular blood pump (1) according to any one of claims 1 to 4, characterized in that the highly flexible drive shaft (12) is at least partially filled with a sealant.

6. 6. An intravascular blood pump (1) according to any one of claims 1 to 5, characterized in that at least one of the bearing sleeve (30) and the outer bearing ring (32) comprises at least one of the following materials: ceramics and metals.

7. An intravascular blood pump (1) according to any one of claims 1 to 6, characterized in that at least one of the bearing sleeve (30) and the outer bearing ring (32) comprises a coating.

8. An intravascular blood pump (1) according to any one of claims 1 to 7, characterized in that one or both of the proximal end region of the housing (11) or the distal end region of the catheter (5) comprises one or more radial through holes.

9. 9. An intravascular blood pump (1) according to any one of claims 1 to 8, characterized in that the highly flexible drive shaft (12) includes a reinforcing element (35) extending longitudinally within a central lumen of the drive shaft (12).

10. An intravascular blood pump (1) according to any one of claims 1 to 9, characterized in that the radial bearing clearance between the outer bearing ring (32) and the bearing sleeve (30) is between 2 μm and 10 μm, preferably between 3 μm and 4 μm.

11. An intravascular blood pump (1) according to any one of claims 1 to 10, characterized in that the bearing sleeve (30) comprises a distally extending portion of the outer bearing ring (32), and the rotor (10) is attached to the distally extending portion of the bearing sleeve (30).

12. An intravascular blood pump (1) according to any one of claims 1 to 11, characterized in that the rotor (10) is located at a distance of 0.001 mm to 8 mm from the outer bearing ring (32).

13. 13. An intravascular blood pump (1) according to any one of claims 1 to 12, characterized in that it comprises a purge fluid supply line arranged to supply the purge fluid so that the purge fluid flows through a gap defined by the radial bearing.

14. An intravascular blood pump (1) according to any one of claims 1 to 13, characterized in that the drive shaft (12) has a section of reduced diameter and at least the distal portion (30b) of the bearing sleeve (30) is arranged in the section of reduced diameter.

15. An intravascular blood pump (1) according to any one of claims 1 to 14, characterized in that the rotor (10) and the housing (11) are radially expandable.

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