Intravascular blood pump

Abstract

The intravascular blood pump has a rotatable shaft (25) carrying an impeller (34) and a housing (20) having an opening (35) through which the shaft extends, and the impeller is positioned outside the housing. The shaft and housing have surfaces (25A, 33A) forming circumferential slits, the circumferential slits having a slit width of not more than 2 μm over at least a portion of the slit length, and at least one of the surfaces forming the slits is made of a material having a thermal conductivity of at least 100 W / mK, specifically a ceramic material, such as SiC.

Description

[0001] Divisional application

[0002] The present application is a divisional application of the patent application for Invention Patent Application No. 201980021509.5, filed on March 21, 2019, entitled "Intravascular Blood Pump". TECHNICAL FIELD

[0003] The present invention relates to an intravascular blood pump, in particular a percutaneously insertable blood pump, for supporting blood circulation in the body of a human being or, optionally, also of an animal. For example, the blood pump can be designed to be percutaneously inserted into the femoral artery and guided through the vascular system of the body, for example, to support or replace the pumping action in the heart. BACKGROUND

[0004] A blood pump of the type mentioned above is known, for example, from EP 0 961 621 B1, which has a drive segment, a catheter attached to the proximal end of the drive segment, which is the end of the drive segment closer to the physician or the "rear end" of the drive segment, and having a line extending therethrough for supplying electrical power to the drive segment, and a pump segment fastened at the distal end of the drive segment. The drive segment comprises a motor housing having an electric motor arranged therein, wherein the motor shaft of the electric motor protrudes distally out of the drive segment and into the pump segment. The pump segment in turn comprises a tubular pump housing having an impeller rotating therein, the impeller being fixed on the end of the motor shaft protruding out of the motor housing. The motor shaft is mounted in the motor housing and in two bearings, which are maximally spaced apart from each other to ensure a true, precisely centered guidance of the impeller within the pump housing. While a radial ball bearing is used for the bearing at the proximal end of the motor housing, the impeller-side bearing, which is the bearing closest to the blood, is configured as a shaft seal for blood made of polytetrafluoroethylene, which has a high hardness and a low coefficient of friction, thus providing support and at the same time preventing blood from entering the motor housing through such a distal shaft bearing. In addition, the entry of blood into the motor housing is counteracted by a washing fluid being conveyed through the motor housing and the impeller-side shaft seal bearing. This takes place at a washing fluid pressure that is higher than the pressure present in the blood.

[0005] An improvement of the blood pump mentioned above is disclosed in US 2015 / 0051436 A1 and shown in the drawings attached hereto Figure 2 Here, the impeller-side bearing at the distal end of the motor housing comprises an axial slide bearing and a radial slide bearing or a combined axial-radial slide bearing, wherein the radial slide bearing replaces the shaft seal bearing mentioned above. Thereby, a washing fluid flows through the gap of the impeller-side radial slide bearing, thus preventing blood from entering the housing.

[0006] Although the invention will be described, and preferably in the context of an intravascular blood pump having a motor housed within the aforementioned housing, the invention is equally advantageously applicable to other types of intravascular blood pumps, wherein the motor is located outside the patient's body, and rotational energy for the impeller is transmitted via a flexible rotary drive cable through a catheter and the housing attached to the distal end of the catheter. Furthermore, in this type of intravascular blood pump, a flushing fluid typically flows through an opening in the drive shaft into the patient's bloodstream.

[0007] Heparin, typically mixed into the cleaning fluid, causes a common problem. Although the cleaning fluid flows through the gap formed between the shaft and the housing, which would tend to push blood entering the housing through such a gap back, blood entry into the gap cannot be completely prevented. In particular, some blood can always enter at least the distal segment of such a gap. Heparin helps prevent blood from clotting in the gap or adhering to the surface, and thus prevents obstruction of shaft rotation. However, physicians often do not want heparin to be administered to the patient's blood via the cleaning fluid. For example, during emergency treatment, heparin may be counterproductive because its prevention of blood clotting can impair healing or hemostasis. Furthermore, the amount of heparin administered to the patient's blood along with the cleaning fluid is difficult to control for various reasons. In particular, the amount of heparin is often more than the physician expects. Accordingly, if necessary, physicians will often prefer to administer heparin to the patient in the required amount separately from the operation of the blood pump.

[0008] Therefore, there is a need for an intravascular blood pump that, if desired, can operate using a cleansing fluid containing little or no heparin. Summary of the Invention

[0009] Therefore, according to a first aspect of the invention, an intravascular blood pump may include a rotatable shaft carrying an impeller and a housing having an opening, wherein the shaft extends through the opening, the impeller is positioned outside the housing, and the shaft and housing have surfaces forming a circumferential slit within the opening. This is essentially no different from the prior art discussed above, and the slit may specifically constitute a radial sliding bearing for the shaft. However, in the blood pumps disclosed herein, the width of the slit is 2 μm or less over at least a portion of the slit's length; for example, only the front end or impeller side of the slit may have a slit width of 2 μm or less, or, in one embodiment, the width of the slit is 2 μm or less along its entire length, and, furthermore, at least one of the two surfaces forming the circumferential slit is made of a material having a thermal conductivity λ ≥ 100 W / mK.

[0010] The following attempts to explain why the measures mentioned above contribute to the operation of intravascular blood pumps that can be operated using a cleansing fluid that does not contain heparin at all, or even without a cleansing fluid for a short period of time. Specifically, it is believed that red blood cells, with a diameter of approximately 8 μm and a thickness of approximately 2 μm, are unlikely to enter and block the gap due to the small gap width of 2 μm or less. Furthermore, due to the small gap width, the cleansing fluid flows through the gap at high speed, thereby propelling the blood back out of the gap by high kinetic energy. However, experiments show that although red blood cells appear to be successfully prevented from entering the gap, biomaterial accumulates in the gap and causes axial blockage. It is believed that this biomaterial still originates from plasma entering the gap despite the strong cleansing fluid flow. More specifically, it is believed that the biomaterial deposited in the gap mainly consists of denatured portions of plasma that adhere to and block the surface forming the gap, particularly fibrin. This is hypothesized to be caused by the high temperature generated in the gap, due to the very small gap width and the heat generated by shear within the gap. Further experiments have shown that by manufacturing the surface with a material having relatively high thermal conductivity, the temperature in the gap can be kept at a low level, preferably 55°C or lower, thereby preventing the denaturation of fibrin in the plasma.

[0011] Most surprisingly, it has been found that intravascular blood pumps with the properties mentioned above can operate for extended periods without blockage, even without any flushing fluid moving through the gap. This is believed to be attributed to plasma entering the gap and forming a slippery biofilm on one or more surfaces within the gap. This constitutes a substantial safety factor for intravascular blood pumps and is therefore extremely beneficial to them.

[0012] A material having one or more surfaces forming a slit with a thermal conductivity of 100 W / mK is sufficient to conduct heat away from the slit and thus maintain the temperature within the slit at 55°C or lower. However, the thermal conductivity is preferably at least 130 W / mK, more preferably at least 150 W / mK, and most preferably at least 200 W / mK.

[0013] To transfer heat away from the gap into the bloodstream, it is preferable that the surface forming the gap comes into thermal contact with the blood flowing through the pump. According to thermodynamics, flowing blood carries away heat faster than non-flowing blood. The faster the blood flows, the more heat is carried away through conductive heat transfer. The blood flow velocity through the pump is typically higher than the blood flow velocity outside the pump. Accordingly, for example, the heat generated in the gap and that heats the surface forming the gap can be further conducted from the shaft surface through the shaft body into the impeller at the end of the shaft, and from there into the blood flowing along the impeller. However, because the distance for heat to flow axially through the shaft body and further through the impeller into the bloodstream is relatively long, it is more preferable to conduct heat (alternatively or only) radially away from the gap, i.e., through the radially outer surface forming the gap. It is preferable to carry heat away in the radial direction, not only because of the relatively short radial distance required for heat to flow from the gap to the flowing blood, but also because it is easier to increase the thermal conductivity area that heat can be conducted radially compared to the thermal conductivity cross-sectional area of ​​the shaft body through which heat can be conducted axially. That is, the cross-sectional area A of the shaft body 轴向 It is A 轴向 =πd 2 / 4, and the cross-sectional area A of the radial outer surface forming the gap. 径向 It is A 径向 =πdl. Therefore, increasing the diameter of the slit (e.g., to d = 1 mm) will affect the cross-sectional area A of the radial outer surface forming the slit. 径向 The positive impact is four times greater than the cross-sectional area A of the main body of the axis. 轴向 Furthermore, increasing the length (l) of the gap only affects the cross-sectional area A of the radially outer surface forming the gap. 径向 It has a positive impact on the cross-sectional area A of the shaft body. 轴向 There is absolutely no impact. In any case, the slit should preferably be long and have a large diameter. However, because a large diameter can counteract the amount of heat generated in the slit, the diameter of the slit should not be too large (preferably d about ≤1 mm). Most preferably, the surfaces forming the slit have high thermal conductivity, at least 100 W / mK, and are in contact with the heat conduction of blood flow.

[0014] Such thermal conductive contact can be direct or indirect. Direct thermal conductive contact can be achieved if the various thermally conductive surfaces forming the gap constitute part of a structural element, the structural element is entirely made of a thermally conductive material, and the intravascular blood pump is in direct contact with the blood flow passing through the pump while it is operating in the patient's blood vessels. This can be the case when the shaft and impeller are formed as a single integral part of a thermally conductive material, and / or when the distal end of the housing forming the through-hole for shaft passage is a single integral part of a thermally conductive material.

[0015] Alternatively, indirect thermal conductivity contact can be achieved if one or more slit-forming surfaces each constitute part of a structural element, the structural element being entirely made of a thermally conductive material and having at least one other surface thermally conductively connected to the separate thermally conductive elements. When the intravascular blood pump is operating in the patient's blood vessels, the separate thermally conductive elements are in direct contact with the flowing blood, or indirectly in contact with the flowing blood via one or more other thermally conductive elements, such that heat from the slit-forming surfaces can be dissipated into the flowing blood through thermal conduction. Of course, the thermally conductive elements themselves should have high thermal conductivity, preferably higher than the preferred thermal conductivity of the slit-forming surfaces, i.e., higher than 100 W / mK, preferably higher than 130 W / mK, more preferably higher than 150 W / mK, and most preferably higher than 200 W / mK.

[0016] Because the surface forming the slit can preferably constitute a radial sliding bearing for a shaft, the surface should have a very small surface roughness, preferably 0.1 μm or less. While such a surface roughness can be obtained using diamond-like carbon (DLC) coatings, as proposed in US2015 / 0051436A1 as a coating for shafts, it is impossible to achieve a slit width of 2 μm or less over the entire slit length using current technology by applying a DLC coating with such precision. Therefore, it is preferable to manufacture one or more slit-forming surfaces from materials different from DLC and / or by different methods, most preferably from ceramic materials, particularly from sintered ceramic elements. That is, preferably, the heat-conducting surface is not a coating on a structural element, but the surface of one or more structural elements, i.e., the surface of one or more elements assembling the pump.

[0017] A common problem with ceramics is that ceramic materials typically have very low thermal conductivity. For example, zirconium oxide (ZrO2), mentioned in US2015 / 0051436 A1, has a thermal conductivity of only 2.5 to 3 W / mK. Alumina (Al2O3) is a well-known ceramic with a relatively high thermal conductivity of 35 to 40 W / mK, but it is still substantially lower than that of metals such as copper. One of the very few ceramics with substantially high thermal conductivity is silicon carbide (SiC). Typical processed silicon carbide has a thermal conductivity between 100 W / mK and 140 W / mK, but silicon carbide with even higher thermal conductivity is also available. Pure silicon carbide has a thermal conductivity of 350 W / mK. Unlike other ceramics, silicon carbide is very brittle and therefore difficult to handle. It can easily break during manufacturing and assembly. Nevertheless, due to its good heat capacity, silicon carbide is a preferred material for the purposes of this invention for at least one of the surfaces forming the slit, preferably the radially outer surface of the slit, and is not a preferred material for the shaft due to its brittleness. Therefore, the individual surfaces or the entire structural element forming such surfaces comprises or is preferably composed of silicon carbide.

[0018] If silicon carbide forms one surface of the sliding bearing, then the mating opposing surfaces of the sliding bearing can be substantially any other type of material, particularly any other type of ceramic material. The preferred ceramic material for the various other surfaces is alumina-toughened zirconia (ATZ) due to its high durability, however, it has a thermal conductivity of only 25 W / mK. Therefore, it is preferred to manufacture the shaft with ATZ and the sleeve in which the shaft slides with SiC, allowing heat to be easily conducted radially outward from the gap into the flowing blood.

[0019] Because the pressure drop of the cleaning fluid flowing through the slit from proximal to distal is high due to the small slit width, the slit width preferably narrows from wide to narrow towards the impeller-side end of the slit (the impeller-side end of the slit is the blood-contacting side of the slit), such that only the distal end or a relatively short distal segment of the slit has a slit width of 2 μm or less. That is, the advantage of a slit that narrows towards the proximal or impeller-side end or distal end (these terms have the same meaning) is that the pressure drop in the cleaning fluid flowing along the length of the slit from proximal to distal can be kept low, as compared to the pressure drop in a non-contracting slit of the same length with the minimum width over the entire length of the slit. In this way, a cleaning fluid pump providing, for example, a pressure of 1 to 1.5 bar can also be used, even with a very small minimum slit width.

[0020] More specifically, the slit may narrow toward the front end or impeller-side end of the slit, such that the minimum width of the slit is located somewhere within 30% of the length of the impeller-side end of the slit closest to the slit. More preferably, the minimum width exists at least at the impeller-side end of the slit.

[0021] When the minimum slot width is effectively limited to the impeller-side end of the slot, i.e., limited to a segment with an infinitely short slot length, this can lead to increased wear in the corresponding segment of the slot. Therefore, according to a preferred embodiment, the segment of the slot with the minimum slot width can extend through 50% or less of the length of the slot, preferably 30% or less, but preferably not less than 20% of the slot length, to keep wear at a low level. The length of such a segment can be in the range of 0.1 to 0.7 mm, more preferably between 0.2 and 0.4 mm.

[0022] The narrowing of the slot can be achieved by one or two tapered surfaces forming the slot: an outer tapered surface formed by the inner surface of the opening through the housing wall, and an inner tapered surface formed by the shaft surface. The tapering of the outer surface of the slot refers to a decrease in the diameter of the wall opening towards the impeller-side end of the slot, while the tapering of the inner surface of the slot refers to an increase in the diameter of the shaft towards the impeller-side end of the slot. Preferably, the tapering is formed in the shaft surface, while the opening constituting the outer boundary of the slot can be cylindrical, as this is easier to manufacture.

[0023] The preferred length of the slit is in the range of 1 to 2 mm, preferably 1.3 to 1.7 mm, while the minimum slit width can be 5 μm or less, preferably 4 μm or less, more preferably 3 μm or less, and most preferably 2 μm or less. The maximum slit width is typically located at the end of the slit opposite to the impeller-side end of the slit and reaches 15 μm or less, preferably 10 μm or less, more preferably 8 μm or less, and most preferably 6 μm or less. Most preferably, it is a contracted slit having a maximum slit width of about 6 μm and a minimum slit width of 2 μm or less.

[0024] Furthermore, the gap can continuously, especially linearly, contract at least a portion of its length until the gap reaches its minimum width. Attached Figure Description

[0025] The invention will be explained below by way of embodiment with reference to the accompanying drawings. The drawings are not intended to be drawn to scale. In the drawings, each identical or approximately identical component illustrated in various figures is represented by similar numbers. For clarity, not every component may be labeled in every figure. In the drawings:

[0026] Figure 1This is a schematic diagram of an intravascular blood pump inserted into the left ventricle, with the suction cannula positioned within the left ventricle.

[0027] Figure 2 This is a schematic longitudinal section of an exemplary prior art blood pump.

[0028] Figure 3 yes Figure 2 An enlarged view of a portion of a blood pump, however, showing a structure according to a preferred embodiment of the invention, and

[0029] Figures 4A to 4I This is a magnified view of the distal radial bearing of the pump, showing the variation of the contracted circumferential gap.

[0030] Figure 1 This embodiment illustrates the use of a blood pump to support the left ventricle. The blood pump includes a catheter 14 and a pumping device 10 attached to the catheter 14. The pumping device 10 has a motor segment 11 and a pump segment 12, which are coaxially arranged one behind the other and result in a rod-shaped configuration. The pump segment 12 has an extension in the form of a flexible suction tubing 13, often referred to as a "cannula". An impeller is disposed in the pump segment 12 to induce blood flow from a blood flow inlet to a blood flow outlet, and the rotation of the impeller is caused by an electric motor disposed in the motor segment 11. The blood pump is positioned such that it is primarily located in the ascending aorta 15b. The aortic valve 18, in the closed state, becomes an abutment against the pump segment 12 or its suction tubing 13. The blood pump, having the suction tubing 13 in the foreground, is inserted anteriorly into the indicated position via a probing catheter 14, optionally with a guidewire. In this way, the inhalation tubing 13 travels retrogradely past the aortic valve 18, so blood is drawn in through the inhalation tubing 13 and pumped into the aorta 16.

[0031] The uses of blood pumps are not limited to Figure 1 The application of the symbol in Figure 1 The applications described herein are only typical examples of the applications. Therefore, the pump could also be inserted through other peripheral vessels, such as the subclavian artery. Alternatively, reverse application to the right ventricle can be conceived.

[0032] Figure 2 An exemplary embodiment of a blood pump according to prior art US 2015 / 0051436 A1 is shown, which is equally suitable for use in the context of this invention, except for the front end marked with "I" and surrounded by an improvement according to the invention. A preferred embodiment of such an improvement is... Figure 3As shown in the diagram, the motor segment 11 has an elongated housing 20 in which the electric motor 21 can be housed. Typically, the stator 24 of the electric motor 21 can have a plurality of circumferentially distributed windings and a magnetic return path 28 in the longitudinal direction. The magnetic return path 28 can form the outer cylindrical sleeve of the elongated housing 20. The stator 24 can surround a rotor 26 connected to a motor shaft 25 and consists of permanent magnets magnetized in the direction of movement. The motor shaft 25 can extend through the entire length of the motor housing 20 and protrude from it at its distal end through an opening 35. There, it carries an impeller 34 from which pump blades 36 protrude, the impeller 34 being rotatable within a tubular pump housing 32, which is securely connected to the motor housing 20.

[0033] The proximal end of the motor housing 20 has a flexible conduit 14 to which it is hermetically attached. A cable 23 for supplying power to and controlling the electric motor 21 can extend through the conduit 14. Additionally, a cleaning fluid line 29 can extend through the conduit 14 and penetrate the proximal end wall 22 of the motor housing 20. Cleaning fluid can be supplied into the interior of the motor housing 20 via the cleaning fluid line 29 and exits through the end wall 30 at the distal end of the motor housing 20. The cleaning pressure is selected such that it is higher than the present blood pressure to prevent blood from seeping into the motor housing, and is between 300 and 1400 mmHg depending on the application.

[0034] As mentioned above, the same cleaning seal can be combined with a pump driven by a flexible drive shaft and a remote motor.

[0035] As the impeller 34 rotates, blood is drawn in through the distal opening 37 of the pump housing 32 and transported axially backward within the pump housing 32. The blood flows out of the pump section 12 through the radial outlet opening 38 in the pump housing 32 and further along the motor housing 20. This ensures that heat generated in the motor is carried away. Alternatively, the pump section can be operated in the reverse flow direction, causing blood to be drawn in along the motor housing 20 and exit from the distal opening 37 of the pump housing 32.

[0036] In one aspect, the motor shaft 25 is mounted in a radial bearing 27 at the proximal end of the motor housing 20, and in another aspect, in a radial bearing 31 at the distal end of the motor housing 20. The radial bearings, particularly the radial bearing 31 in the opening 35 at the distal end of the motor housing, are constructed as sliding bearings. Furthermore, the motor shaft 25 is also axially mounted in the motor housing 20, and the axial bearing 40 is similarly constructed as a sliding bearing. The axial sliding bearing 40 serves to withstand the axial force acting on the motor shaft 25 in the distal direction when the impeller 34 delivers blood from the distal end to the proximal end. If the blood pump is used to deliver blood also or only in the reverse direction, then the corresponding axial sliding bearing 40 may (or only) be arranged in a corresponding manner at the proximal end of the motor housing 20.

[0037] Figure 3 More details are shown in Figure 2 The portion marked with "I" has been structurally improved according to a preferred embodiment of the invention. Specifically, the radial sliding bearing 31 and the axial sliding bearing 40 can be seen. The bearing gap of the radial sliding bearing 31 is formed, in one aspect, by the circumferential surface 25A of the motor shaft 25, and in another aspect by the surface 33A of the through hole in the bushing or sleeve 33 of the end wall 30 of the motor housing 20, the end wall 30 of the motor housing 20 defining an outer gap diameter of approximately 1 mm, although the outer gap diameter may be larger. In this embodiment, the bearing gap of the radial sliding bearing 31 has a gap width of 2 μm or less, not only at the front end or impeller-side end of the gap, but also along the entire length of the radial sliding bearing. Preferably, the gap width is between 1 μm and 2 μm. The length of the gap can be in the range of 1 mm to 2 mm, preferably from 1.3 mm to 1.7 mm, for example 1.5 mm, corresponding to the length of the radial sliding bearing 31. The surface forming the gap of the radial sliding bearing 31 has a surface roughness of 0.1 μm or less.

[0038] Shaft 25 is preferably made of ceramic material, and most preferably of alumina-toughened zirconia (ATZ) to prevent shaft breakage. ATZ has a relatively high thermal conductivity due to aluminum's thermal conductivity being between 30 and 39 W / mK. The impeller 34, carried at the distal end of shaft 25, is preferably made of a material with even higher thermal conductivity. In this way, the heat generated in the very narrow gap of the radial sliding bearing 31 can be dissipated through shaft 25 and impeller 34 into the blood flowing along the outer surface of impeller 34.

[0039] However, in an embodiment where the impeller is made of a material with low thermal conductivity, such as PEEK, or even in an embodiment where the impeller is made of a material with high thermal conductivity, as mentioned above, it is advantageous to use a material with high thermal conductivity to manufacture the sleeve 33 in the end wall 30 of the housing 20, preferably at least 100 W / mK, more preferably at least 130 W / mK, even more preferably at least 150 W / mK, and most preferably at least 200 W / mK. In particular, the sleeve 33 can be a ceramic sleeve, more specifically made of sintered ceramic material. As a particularly preferred ceramic material, the sleeve 33 can comprise or consist entirely of SiC due to its high thermal conductivity.

[0040] While the entire end wall 30 can be formed as a single piece made of a highly thermally conductive material, it is preferable to assemble the end wall 30 from a sleeve 33 and one or more radially external elements 33B that are themselves thermally conductive. This may be particularly important when the sleeve 33 is made of a brittle material such as SiC. Accordingly, the radially external thermally conductive elements 33B are thermally conductively connected to the sleeve 33 and have a thermal conductivity that is preferably higher than that of the sleeve 33, and in any case at least 100 W / mK, thereby ensuring that heat from the sleeve 33 can be dissipated into the flowing blood through thermal conduction and diffusion via the thermally conductive elements 33B.

[0041] If it is possible to Figure 3 Furthermore, as seen in Figure 2 Compared to the prior art structure shown, the axial length of the end wall 30 of the housing 20 is relatively long. More specifically, the path for blood to flow along the outer surface of the end wall 30 of the housing 20 is longer in the axial direction than in the radial direction. This provides a large surface area for heat transfer from the end wall 30 of the housing 20 into the blood flow. For example, blood flow can be guided outward along the end wall 30 of the housing 20 over a radial distance between 0.5 and 1 mm, preferably about 0.75 mm, while flowing 1.5 mm to 4 mm, preferably about 3 mm, in the axial direction.

[0042] Regarding the bearing gap of the axial sliding bearing 40, it is formed by the axial inner surface 41 of the end wall 30 and its opposing surface 42. The opposing surface 42 may be part of a ceramic disk 44, which may be distally fixed to the motor shaft 25 of the rotor 26 and rotate with the rotor 26. A channel 43 may be provided in the bearing gap surface 41 of the end wall 30 to ensure that cleaning fluid flows towards the radial sliding bearing 31 through the bearing gap surfaces 41 and 42 of the axial sliding bearing 40. Apart from this, the surfaces 41 and 42 of the axial sliding bearing 40 may be flat. The bearing gap of the axial sliding bearing 40 is very small, a few micrometers.

[0043] When the bearing clearance surface 41 of the axial sliding bearing 40 is formed by the sleeve 33, such as in Figure 3 As shown, and when the sleeve 33 is made of SiC, the ceramic disk 44 forming the opposing surfaces 42 of the axial sliding bearing 40 is preferably made of alumina-toughened zirconia (ATZ). Alternatively, the opposing bearing gap surfaces 42 may be DLC-coated or may also be made of SiC.

[0044] The pressure of the cleaning fluid is regulated such that the pressure drop along the radial sliding bearing 31 is preferably about 500 mmHg or more, in order to maintain a high axial cleaning flow velocity (≥0.6 m / s) within a narrow 1 to 2 μm gap. The blood pump 10 can be operated using a cleaning fluid without heparin. If cleaning fails, the blood pump can continue to operate for at least several hours even without any cleaning fluid.

[0045] Figures 4A to 4C Variations of the circumferential gap (specifically designated here by reference numeral 39) of the radial sliding bearing 31 defined at the distal end of the blood pump housing 20 are shown. More specifically, in these variations, the circumferential gap 39 narrows from the proximal end to the distal end. Arrows indicate the flow direction of the cleaning fluid used to clean the radial sliding bearing 31.

[0046] The first embodiment of the contracting gap 39 is in Figure 4A As shown in the figure. Here, the slit narrows continuously from the proximal end to the distal end, more specifically linearly, so that the minimum slit width is precisely located at the impeller-side end 39A of the slit 39.

[0047] exist Figure 4B In the embodiment shown, the slit 39 similarly tapers continuously and linearly from the proximal end to the distal end of the impeller side 39A, but the minimum slit width extends through a portion of the length of the slit 39, thus forming its cylindrical end segment. As in Figure 4B The cylindrical end segment of the slit 39 shown in the figure, for example in Figure 4A The pointed end segments shown in the embodiments are less prone to wear. In both embodiments, the gap can selectively shrink non-linearly, particularly convexly or, in other words, shrinking gradually from the proximal end to the distal end.

[0048] exist Figure 4A and Figure 4B In the embodiment shown, the contraction of the slit 39 is due to the tapering of the distal opening 35, which has a narrower diameter compared to the proximal end, while at the same time Figure 4C and Figure 4DOne implementation involves the contraction of the slot 39 being achieved by the tapering of the shaft 25. More specifically, in both cases, the outer diameter of the shaft 25 extends toward the impeller-side end 39A of the slot 39. Figure 4C In this configuration, the outer diameter of shaft 25 expands from a constant-diameter shaft segment near the proximal end of slot 39 to its maximum outer diameter within slot 39, the constant-diameter shaft segment extending through the end of slot 39 opposite to the impeller-side end 39A of slot 39. Figure 4D In the embodiment shown, the outer diameter of the shaft has a circumferential groove that extends through the slit 39 to the end opposite to the impeller-side end 39A of the slit 39. In the illustrated embodiment, the diameter of the groove increases linearly from the proximal end to the distal end, such that the minimum slit size is quickly reached before the impeller-side end 39A of the slit 39. However, instead of a linearly contracting slit 39, the diameter of the shaft 25 can be increased, for example, progressively towards the impeller-side end 39A of the slit 39.

[0049] exist Figures 4A to 4D The variations described in relation to the embodiments shown can be combined in any suitable manner, i.e., the contracted slit 39 can be formed either by a tapered diameter extending through the opening therein via a shaft 25, or by a tapered shaft 25.

[0050] Figures 4E to 4I This relates to an embodiment of the distal radial bearing 31 of the pump optimized for ease of manufacture, concerning the contraction gap 39. Figure 4E The intermediate bearing 31 is divided into two bearing rings 31A and 31B, with the distal bearing ring 31A, which is in contact with blood, having an opening of a smaller diameter than the proximal bearing ring 31B. Figure 4F The narrowing gap is achieved by a circumferential groove 25B in surface 25A of shaft 25, the groove 25B having a simple curved cross-section. Figure 4G The contraction gap is similarly achieved by a circumferential groove 25B in the surface 25A of the shaft 25, but here the groove 25B gives the shaft 25 a conical axial cross-section in the region of the gap 39. Figure 4H The intermediate bearing 31 is formed through a stepped bore, the stepped bore having a smaller diameter at its distal end in contact with blood compared to the proximal end of the slit 39. Figure 4E The implementation methods are similar. Figure 4I In this embodiment, bearing 31 is again divided into two bearing rings 31A and 31B, such that the distal bearing ring 31A, which is in contact with blood, has a smaller diameter than the proximal bearing ring 31B. However, in this embodiment, the proximal bearing ring 31B has a cylindrical inner surface, while the distal ring 31A has a conical inner diameter that tapers toward the impeller-side end 39A of the slit.

Claims

1. An intravascular blood pump, characterized in that, The device includes a rotatable shaft (25) carrying an impeller (34) and a housing (20) having an opening (35), wherein the shaft (25) extends through the opening (35), the impeller (34) is positioned outside the housing, the shaft and the housing have surfaces (25A, 33A) forming a circumferential slit within the opening (35), wherein the slit has a length and a width of 5 μm or less over at least a portion of the length, and wherein at least one of the surfaces (25A, 33A) forming the slit is made of a material having a thermal conductivity of at least 100 W / mK.

2. An intravascular blood pump, characterized in that, The device includes a rotatable shaft (25) that carries an impeller (34) and a housing (20) having an opening (35), wherein the shaft (25) extends through the opening (35), the impeller (34) is positioned outside the housing, the shaft and the housing have surfaces (25A, 33A) forming a circumferential slit within the opening (35), wherein at least one of the surfaces (25A, 33A) forming the slit is at least a radially outer surface, the at least radially outer surface being made of a material having a thermal conductivity of at least 100 W / mK.

3. The intravascular blood pump according to claim 2, wherein the slit has a length and a width of 5 μm or less over at least a portion of the length.

4. The intravascular blood pump according to any one of claims 1 to 3, wherein the thermal conductivity is at least 130 W / mK.

5. The intravascular blood pump according to any one of claims 1 to 3, wherein the thermal conductivity is at least 150 W / mK.

6. The intravascular blood pump according to any one of claims 1 to 3, wherein the thermal conductivity is at least 200 W / mK.

7. The intravascular blood pump according to any one of claims 1 to 3, wherein the surface forming the slit constitutes a radial sliding bearing for the shaft.

8. The intravascular blood pump according to any one of claims 1 to 3, wherein at least one of the surfaces (25A, 33A) forming the slit constitutes part of a structural element (33), the structural element (33) being entirely made of the material and in direct contact with flowing blood when the intravascular blood pump is used in a patient's blood vessels.

9. The intravascular blood pump according to any one of claims 1 to 3, wherein at least one of the surfaces (25A, 33A) forming the slit constitutes part of a structural element (33), the structural element (33) being entirely made of the material and having at least one additional surface thermally conductively connected to a heat-conducting element (33B), the heat-conducting element (33B) being in direct contact with flowing blood or indirectly in thermal conduction contact with flowing blood via one or more additional heat-conducting elements when the intravascular blood pump is in operation in a patient's blood vessel, such that heat from at least one of the surfaces (25A, 33A) forming the slit can be dissipated into the flowing blood by thermal conduction, wherein the thermal conductivity of the one or more heat-conducting elements is at least 100 W / mK.

10. The intravascular blood pump according to any one of claims 1 to 3, wherein each of the surfaces (25A, 33A) forming the slit has a surface roughness of 0.1 μm or less.

11. The intravascular blood pump according to any one of claims 1 to 3, wherein the at least one surface is made of a ceramic material.

12. The intravascular blood pump according to any one of claims 1 to 3, wherein the at least one surface constitutes part of a ceramic sleeve in which the shaft (25) is slidable.

13. The intravascular blood pump according to any one of claims 1 to 3, wherein the shaft (25) forming the surface of the slit is made of a ceramic material.

14. The intravascular blood pump of claim 13, wherein the surface of the shaft forming the slit is made of alumina-toughened zirconia (ATZ).

15. The intravascular blood pump according to any one of claims 1 to 3, wherein the at least one surface comprises silicon carbide (SiC).

16. The intravascular blood pump of claim 15, wherein one of the at least one surface (25A, 33A) comprises silicon carbide (SiC), and the other of the at least one surface (25A, 33A) comprises alumina-toughened zirconia (ATZ).

17. The intravascular blood pump according to any one of claims 1 to 3, further comprising a cleaning fluid supply line (29) connected to the housing and configured to guide cleaning fluid into the housing and exit the housing through the opening (35).

18. The intravascular blood pump according to claim 1 or 3, wherein the slit (39) narrows toward the impeller-side end (39A) of the slit (39), and the width of 2 μm or less is located somewhere within 50% of the length of the slit (39) closest to the impeller-side end (39A) of the slit (39).

19. The intravascular blood pump of claim 18, wherein the width of 2 μm or less is present at the impeller-side end (39A) of the slit (39).

20. The intravascular blood pump of claim 18, wherein the width of 2 μm or less extends through 30% or less of the length of the slit (39).

21. The intravascular blood pump according to claim 18, wherein the diameter of the opening (35) narrows toward the impeller-side end (39A) of the slit (39).

22. The intravascular blood pump according to claim 18, wherein the outer diameter of the shaft (25) expands toward the impeller-side end (39A) of the slit (39).

23. The intravascular blood pump according to claim 22, wherein the outer diameter of the shaft (25) has a circumferential groove extending through the slit (39) to an end opposite to the impeller-side end (39A) of the slit (39).

24. The intravascular blood pump according to claim 22, wherein the outer diameter of the shaft (25) is expanded from a constant diameter shaft segment extending through the slit (39) to the maximum outer diameter within the slit (39) at the end opposite to the impeller-side end (39A) of the slit (39).

25. The intravascular blood pump according to claim 18, wherein the maximum width of the slit (39) is 15 μm or less.

26. The intravascular blood pump according to claim 25, wherein the maximum width of the slit (39) is 6 μm or less.

27. The intravascular blood pump according to any one of claims 1 to 3, wherein the length of the slit (39) is in the range of 1 to 2 mm.

28. The intravascular blood pump according to claim 27, wherein the length of said slit (39) is in the range of 1.3 to 1.7 mm.

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