Patent Application
20220134085
The application relates to a catheter device with a rotor, comprising a drive shaft, according to the preamble of the main claim.
Such catheters are typically used as blood pump arrangements, where the device is positioned in the body of a human or animal, to produce or transmit a torque or rotation movement, such that the rotor effects a flow of blood. The drive shaft runs axially along the longitudinal extension of the catheter between a driving region of the catheter and a distal end region of the catheter. Typically, the driving region is located in a proximal end region, which remains outside the body and is connected to a drive motor. Therefore, the drive shaft should remain pliable and flexible, also under load.
For many applications, it is necessary to guide the catheter along a desired path through the body, for example, along or within blood vessels, in order to position the rotor located at the distal end of the catheter at a desired location within the body, for example, within a heart ventricle of near a heart ventricle, for the duration of the respective application. The rotor and drive shaft then rotate in a rotating direction, according to the desired application, for example, such that a flow of blood from away from the patient's heart, in a proximal direction, is effected. In order to guide the catheter through a lumen, the catheter device can be designed as an expandable pump, where the rotor is designed as a radially compressible rotor, which can be arranged inside a radially compressible housing. Both the rotor and the housing can be transferred into a cannula or sheath, which is typically located proximally of the rotor and has an inner diameter that is smaller than the diameter of the rotor and the housing in an expanded state. For example, by exerting a pulling force on a pliable sheath provided around the drive shaft at the proximal end of the catheter device, the compressible rotor and the compressible housing can be transferred at least in part into the cannula or sheath, and are thereby compressed.
For example, for delivering blood, it can be necessary to produce rotation speeds of more 10,000, more than 20,000 or even more than 30,000 revolutions per minute. Often, the rotation movement must be produced over a longer period of time, such as for several days or even weeks.
For some arrangements, the provision of a distal bearing for stabilizing the distal end of the drive shaft has benefits. In some embodiments, the distal bearing can comprise an elongated polymer part wherein the drive shaft is mounted. The polymer part can for instance be made of Pebax® or Polyurethane or Polyetheretherketone (PEEK). Furthermore, additional bearings, for instance made of ceramics, can be provided inside the elongated polymer part.
Typically, catheter devices of this type comprise a flexible atraumatic tip to avoid damage to the patient's tissue. The atraumatic tip can be made of a flexible medical grade polymer such as Pebax® or Polyurethane. Preferably, the flexible atraumatic tip is designed as a pigtail.
In some embodiments, the elongated polymer end part and the flexible atraumatic polymer tip form a single polymer end part.
Particularly high demands are placed on the mechanical and the chemical loadability of the catheter, the drive shaft, and in particular the distal bearing, which can be in contact with the rotating shaft and can therefore be subject to physical forces leading to heavy abrasive wear. At high rotational speeds, frictional heat is produced, in some cases leading to temperatures of over 160° C., thus exceeding the melting point of some medical-grade polymers used for making the above-mentioned polymer end part. Under these circumstances, a distal bearing made of such a material would be subject to melting.
Material fatigue and damaging processes on the drive shaft and the distal bearing and on other components should only progress as slowly as possible, and moreover as predictably and as controllably as possible, as they not only damage the catheter device, but also present a health hazard to the patient, as wear debris is transferred to the blood and into the patient's body. The risk of tearing and breakage of the drive shaft or the distal bearing or melting of the distal bearing should be minimized. In particular, the bearing should be designed to minimize friction and heat production, which are important factors leading to wear and tear.
Frictional forces and heat production are not only damaging to the pump itself. It should also be taken into account that blood consists of a number of constituents, such as blood cells, which can be damaged both mechanically when in contact with the rotor and the shaft or other parts of the catheter device, or thermally when exposed to the heat produced within the catheter device, for instance due to denaturation. Certain blood proteins will decom-pose at 60° C. so that this can be seen as an upper acceptable limit.
Furthermore, damage to patient tissue caused by the rotating elements should be avoided. For example, intraventricular pumps can cause damage to the heart, as heart tissue, such as for instance tendinous chords or structures pertaining to the mitral valve, can be sucked into the pump or become entangled with rotating parts.
To avoid entanglement of tissue with rotating parts, EP 2047873 describes Polyurethane drive shaft covers which separate the rotating drive shaft from the blood. For this purpose, the gap between the drive shaft and the drive shaft cover is kept very small. However, this can lead to increased wear and tear, especially when flexible drive shafts made out of metal are used. On the other hand, a rigid tube-shaped drive shaft cover requires precise centering of the flexible drive shaft inside the drive shaft cover. EP 2868331 describes a flexible pump, which tolerates bending of the pump head.
However, in a device as described in EP 2868331, in particular in conjunction with a flexible polymer end part at the distal end of the pump head, a rigid drive shaft cover can lead to a kink in the drive shaft upon bending of the catheter device. In particular, a kink can form in the region between the rigid drive shaft cover and the rotor, potentially leading to severe damage of the drive shaft.
In such a configuration, friction leads to relevant heat production between the drive shaft and the bearing, in some cases causing both damage to the blood and melting of the plastic of the pigtail tip. While the heat quantity deposited is not particularly large, it is very concentrated in a small area. The resulting energy density is therefore significant and leads to localized high temperatures, especially if the surrounding material comprises a low thermal heat conductivity such as polymer.
The aim of the application is to address the above-mentioned problems, at least to address one or more of the following points:
This can be achieved by a catheter device according to the independent claim. Advantageous embodiments are given by the dependent claims and the examples provided in the description.
Said catheter device may comprise a drive shaft extending from a driving region of the catheter device, where a motor may be located for driving the drive shaft, to a distal end region of the catheter device. In the distal end region, a rotor may be attached to the drive shaft such that it can rotate together with the drive shaft. A distal bearing can be provided for bearing a distal end of the drive shaft. The distal bearing may comprise a drive shaft cover which is configured to cover a section of the drive shaft extending distally of the rotor. This way, during operation of the catheter device, it can be avoided that for instance tissue, such as tendinous tissue or trabeculae or muscle bridges, might get caught in said section of the drive shaft which is covered by the drive shaft cover.
The distal bearing may comprise an end part which may be designed to be brought in contact with for example tissue of a patient when the catheter pump is used in the patient. The drive shaft cover may be provided in a section of the drive shaft lying between the rotor and the end part, in particular along the entire section. In an embodiment of the catheter device, a distal end of the drive shaft cover may be provided in the end part, i.e. the drive shaft cover may extend into the end part.
On a distal side of the rotor, a radially inner part of the rotor may be recessed with respect to radially outer parts of the rotor to form a hollow space surrounding the drive shaft. In this case, the recessed radially inner part extends less in a distal direction than the outer parts. The hollow space is then open to the distal side.
A proximal end of the drive shaft cover may lie in said hollow space. This means that the end of the drive shaft cover (at which end the drive shaft protrudes from the drive shaft cover and would otherwise be exposed) may be surrounded by the rotor. In this setup, an opening at the proximal end of the drive shaft cover where the drive shaft protrudes, may be in fluid communication with a volume defined by the hollow space.
Having the rotor around the end of the drive shaft cover in the above-described fashion thus helps to protect the section of the drive shaft which lies between the end of the drive shaft cover and the hub of the rotor. With this setup, even very small pieces of tissue can be kept from getting caught in the drive shaft or from getting sucked into the distal bearing. At the same time, the end of the drive shaft cover may remain at a safe distance from the hub of the rotor to avoid that the rotor might contact the drive shaft cover during operation. In a possible design, there is no portion of the rotor hub extending distally from the rotating rotor blades.
The hollow space typically has a cylindrical shape. It may be designed concentrically with the drive shaft and a hub of the rotor. The radially inner part which is recessed may for instance comprise a distal section of the hub or it may be comprised by the distal section of the hub. In one embodiment, the hollow space is provided in the hub of the rotor.
The drive shaft cover may be designed as a hollow tube. It can be essentially cylindrical. Thereby, an inner diameter can be chosen in accordance with a diameter of the drive shaft. The inner diameter and/or the outer diameter of the drive shaft cover may vary along a length of the drive shaft cover. In particular, having two or three cylindrical sections with different outer diameters can be particularly advantageous in view of the desired functionality of the drive shaft cover, as will be explained here below.
The hub of the rotor may be designed in such a way, that touching of parts can be avoided. For example, the hub of the rotor may be designed to extend less than 0.5 mm past the rotor blades in the distal direction, in order to be able to bring the rotor blades closer to the distal bearing or the end part without the hub potentially touching parts of the drive shaft cover. Preferably, the hub extends less than 0.1 mm in distal direction past the rotor blades, particularly preferably the hub does not extend at all past the rotor blades on the distal side, i.e., the hub can be flush with a leading edge of the rotor blades.
Inside the hollow space, a radial gap is formed between the drive shaft cover and the rotor, i.e., between an outer surface of the drive shaft cover and a cylindrical surface of the rotor delimiting the hollow space. Furthermore, an axial gap is formed between the proximal end of the drive shaft cover and a hub of the rotor. Both gaps should be kept large enough to avoid touching of the parts while keeping the hollow space as small as possible to avoid taking too much material away from the rotor. Both gaps can furthermore be used to circulate blood through the gaps by a pumping function of the drive shaft to avoid any blood stagnation or clotting or local overheating.
A length of the hollow space, which is measured in axial direction, i.e. along the drive shaft, may be for instance at least 0.5 mm, preferably at least 0.7 mm, particularly preferably at least 0.9 mm. Additionally or alternatively, the length may be chosen to be at most 2.5 mm, preferably at most 1.5 mm, particularly preferably at most 1.1 mm.
The drive shaft cover may in one embodiment extend at least 0.3 mm, preferably at least 0.4 mm into the hollow space. On the other hand, it can for instance be chosen to extend at most 2.2 mm, preferably at most 0.8 mm, particularly preferably at most 0.7 mm into the hollow space. This length may be called penetration depth.
The catheter device may be designed as an expandable pump, wherein the rotor is located in a housing. The housing and the rotor can then be configured to be compressed at least along a radial direction extending transversely to a longitudinal direction, from an expanded state into a compressed state. Upon compression of the housing, a relative motion of the rotor with respect to the distal bearing can be effected. This can be due to a change in length of the housing which is associated with the compression of the housing. Said change in length thus gives rise to the aforementioned relative motion.
The penetration depth of the drive shaft cover can be chosen such that the proximal end of the drive shaft cover remains within the hollow space in the compressed state. I.e. the penetration depth can in particular be larger than the above-described change in length of the housing.
The axial gap is preferably provided in such a way, that under a typical deformation of the pump that is to be expected during use of the pump, the proximal end does not come into contact with any parts of the rotor, i.e., the axial gap should allow axial displacement which occurs due to elastic deformation of the pump housing during use. In particular, it can be provided in an embodiment of the catheter device, that a change in length of the axial gap that is due to an apical impulse can be tolerated in such a way, that a gap of at least 0.1 mm remains. In general, the axial gap can thus be adjusted, depending on the elastic properties of the pump.
In an exemplary embodiment, a gap size of the axial gap between the proximal end of the drive shaft cover and the hub of the rotor may be for instance at least 0.2 mm, preferably at least 0.3 mm and/or at most 1.5 mm, preferably at most 0.9 mm, particularly preferably at most 0.6 mm, to avoid touching of the parts.
The above-mentioned radial gap is also designed in such a way, that touching of the drive shaft cover and the rotor is avoided. At the same time, the hollow space should be kept as small as possible, so that potential weakening of the hub is minimized.
In an exemplary embodiment, a gap size of the radial gap between the drive shaft cover and the rotor may be chosen to be at least 0.01 mm, preferably at least, 0.04 mm, particularly preferably at least 0.07 mm and/or at most 0.2 mm, preferably at most 0.13 mm. It was found that ovalization of the rotor—in particular of the rotor hub and thus of the hollow space—during operation can be tolerated without touching of the parts when a gap as described here is provided.
In order to be able to make the hollow space as small as possible while maintaining a desired radial gap size, a wall thickness of a portion of the drive shaft cover penetrating the hollow space may for instance be at least 0.03 mm, preferably at least 0.05 mm, and/or at most 0.3 mm, preferably at most 0.08 mm, particularly preferably at most 0.07 mm.
Diameters of for instance the drive shaft cover or the gap are chosen in accordance with a diameter of the drive shaft, i.e., gaps or wall thicknesses as mentioned above can be maintained for all typical diameters of the drive shaft. An outer diameter of the drive shaft can for instance lie between 0.4 mm and 2 mm, preferably lies between 0.6 mm and 1.2 mm, particularly preferably between 0.8 mm and 1.0 mm.
In an embodiment of the catheter device, a diameter of the hollow space (measured orthogonally to the axis of the drive shaft, i.e. in radial direction) may be at least 0.5 mm, preferably at least 0.8 mm, particularly preferably at least 1.1 mm. Additionally or alternatively, the diameter of the hollow space may be chosen to be at most 2 mm, preferably at most 1.5 mm, particularly preferably at most 1.3 mm.
It can be advantageous to provide a section with an increased outer diameter distally of a proximal section penetrating the hollow space. The proximal section may then have the above-described wall thickness of the portion penetrating the hollow space. The proximal section of the drive shaft cover extends into the hollow space, with a portion of the proximal section typically remaining outside of the hollow space. In this case, the outer diameter of the drive shaft cover increases at a distance from the rotor. The section lying distally of the proximal section typically has a wall thickness that is increased with respect to the wall thickness of the proximal section. Thereby, an inner diameter may be constant along the two sections or it may change. In particular, the inner diameter may be increased in the section lying distally of the proximal section.
The outer diameter of a proximal section of the drive shaft cover which penetrates into the hollow space can for instance be at least 0.1 mm smaller than the outer diameter of the section lying distally thereof (with increased outer diameter), preferably at least 0.14 mm smaller. Additionally or alternatively, it may be at most 0.6 mm smaller than the outer diameter of the section lying distally of the proximal section, preferably at most 0.3 mm smaller.
In an embodiment where a section with increased outer diameter of the above-described type is envisioned, the wall thickness of the portion of the drive shaft cover penetrating the hollow space may preferably be chosen to be less than 0.3 mm, such as for instance at most 0.08 mm or at most 0.07 mm. It is also possible not to provide an increased diameter of this type. In such an embodiment, the wall thickness of the portion of the drive shaft cover penetrating the hollow space may be the same wall thickness as in a further section of the drive shaft cover lying between the rotor and the end part. In such an embodiment the wall thickness may be for instance up to the above-mentioned 0.3 mm.
The proximal section with reduced outer diameter may have a length of at least 0.6 mm, preferably at least 0.8 mm, particularly preferably at least 0.9 mm. Additionally or alternatively, it may have a length of for instance at most 2 mm, preferably at most 1.5 mm, particularly preferably at most 1.1 mm.
The difference in outer diameter between the proximal section of the drive shaft cover and the section lying distally thereof (being for instance between 0.14 mm and 0.3 mm as mentioned above) may be chosen to be for example twice the radial gap size (meaning the difference in radius is at least equal to the radial gap size). This way, upon axial alignment of the rotor and the drive shaft cover, the section with increased diameter lying distally of the proximal section is larger in diameter than the hollow space. This helps to prevent tissue from entering the hollow space.
A portion of the proximal section remaining outside of the hollow space may be provided to avoid touching of the drive shaft cover and the rotor. Similar to the case of the axial gap, upon typical bending of the catheter device, changes in length are expected and touching of the parts should be avoided by providing a sufficient distance between the distal end of the rotor and the section of increased radius. The portion of the proximal section remaining outside of the hollow space may for instance be chosen to have the same length as the axial gap. It may for instance have a length of at least 0.2 mm, preferably at least 0.3 mm and/or at most 1.5 mm, preferably at most 0.9 mm, particularly preferably at most 0.6 mm i.e., in this case, at a distance of at least 0.2 mm, preferably at least 0.3 mm and/or at most 1.5 mm, preferably at most 0.9 mm, particularly preferably at most 0.6 mm from the distal end of the rotor, the outer diameter of the drive shaft cover may increase. The increase in outer diameter occurs for instance smoothly over an axial section of for instance 0.2 mm or less, preferably 0.1 mm or less.
In a possible embodiment of the catheter device, the rotor may comprise a stiffening element. The stiffening element may be designed to surround the hollow space and can help to prevent or reduce deformation of the rotor, in particular of the rotor hub, during operation. It may for instance be designed as a tube, hollow cylinder or ring-structure that is connected to a material of the rotor.
The stiffening element may be made of a material of a higher stiffness than a material of the rotor, i.e., of the hub and/or the blades of the rotor.
The stiffening element may be moulded into the material of the rotor such that it is completely surrounded by the material of the rotor, in particular it may be moulded into the hub of the rotor. This means that in this case there is additional material of the rotor provided on the inside of the stiffening element. It is however also possible to provide the stiffening element around the hollow space such that the stiffening element itself delimits the hollow space, i.e., with the inner surface of the stiffening element being exposed and an outer surface of the stiffening element being connected to the material of the rotor.
The stiffening element may be provided along the full length of the hollow space. The stiffening element may thereby extend past the hollow space in proximal direction. For example, the stiffening element may be longer than the hollow space, e.g. 1.5 times as long or twice as long as the hollow space.
The stiffening element may comprise structures to provide better attachment to the rotor. For example, microstructures and/or macrostructures can be provided. The microstructures and/or macrostructures can for instance be designed as protrusions, indentations or holes. The microstructures and/or macrostructures can be provided on the outside and/or on the inside of the stiffening element. The microstructures and/or macrostructures may be provided over a whole length of the stiffening element or over part of the length of the stiffening element.
In a possible embodiment, the stiffening element comprises structures of the above-described type, which are designed as one or more anchoring elements extending radially on the outside of the stiffening element. The one or more anchoring elements may be designed and positioned in such a way that they extend past the hub of the rotor and into a material of the rotor blades. In this case, they are preferably designed to allow compression of the rotor for insertion of the rotor into the heart. This can be achieved by having the anchoring elements penetrate into the material of the blades only to an extent where the blades can still be compressed of folded. The anchoring elements may further comprise one or more recesses, indentations or undercuts into which the material of the rotor may penetrate. To allow compression or folding of the blades, in a possible embodiment of the catheter pump, anchoring elements extend for example 0.5 mm into the material of the blades, such that the blades remain compressible.
As mentioned, the stiffening element may, additionally or alternatively, comprise holes or indentations to provide a better connection with the material of the rotor. In particular in the case where the stiffening element is completely surrounded by the material of the rotor, one or more holes which may be designed as through-holes or blind holes may be provided in the tube, allowing the material of the rotor to penetrate through a wall of the stiffening element and enabling a particularly reliable connection between the rotor and its stiffening element. A cross section of the holes or indentations is typically not limited to a specific geometry. They may be circular or polygonal. The indentations or holes may for instance have a diameter or edge length of at least 0.02 mm preferably 0.03 mm and/or at most 0.5 mm, preferably at most 0.1 mm.
The stiffening element may be made of a bio-compatible material. This should in particular be the case in embodiments where the inner surface of the stiffening element is exposed. The stiffening element may for instance comprise one or more of MP35N, 35NLT, Nitinol, stainless steel (in particular medical grade stainless steel), and ceramics.
A wall thickness of the stiffening element may be for instance at least 0.03 mm, preferably at least 0.04 mm and/or at most 0.08 mm, preferably at most 0.07 mm.
It can be advantageous to provide the drive shaft cover with a pliable section to enable bending of the drive shaft. In this case, wear and tear on the drive shaft should be reduced and it should be ensured that no kink occurs in the drive shaft. The embodiments described here below are advantageous when it comes to safely bearing the drive shaft while allowing bending of the drive shaft as it is required when introducing the pump or during operation. In particular, bending of the drive shaft while it is rotating at full operating speed is possible. Having the pliable section in conjunction with other aspects of the application can be particularly advantageous.
The pliable section can be provided between a distal end of the rotor and a proximal end of the end part. In particular, the pliable section may be the section lying distally of the proximal section with decreased diameter or it may be a portion of that section.
The pliable section can for instance be provided by having at least one opening in the drive shaft cover in the pliable section. The at least one opening is then typically designed as a through-opening, connecting an inside of the drive shaft cover to an outside of the drive shaft cover.
The openings in the pliable section may be provided such that due to an elasticity of the material of the drive shaft cover, a restoring force brings the drive shaft cover back into an original straight position after bending.
The at least one opening in the pliable section may comprise one or more slits. The slit or slits may have a course with a tangential component. In particular, one or more slits with a spiral shape can be provided, such that the pliable section forms a spiral sleeve.
If one or more slits with a spiral course are provided, a pitch of the spiral course may be for instance at least 0.2 mm, preferably at least 0.3 mm, particularly preferably at least 0.5 mm and/or at most 1.2 mm, preferably at most 0.9 mm, particularly preferably at most 0.8 mm.
The one or more openings may be cut into the drive shaft cover using a laser. Edges of the one or more openings may be smoothened or rounded to avoid wear and/or tissue damage.
Slits may for instance have a width of at least 0.005 mm, preferably at least 0.01 mm, particularly preferably at least 0.025 mm and/or at most 0.2 mm, preferably at most 0.1 mm.
In one embodiment, the pliable section features several slits following a single course, for instance a single spiral course, the several slits being separated by bridges of material between ends of the slits.
If one or more slits are provided, holes may be provided at one end or at both ends of one or more of the slits, the holes having a diameter that is larger than a width of a given slit at which they are provided. This can improve the durability of the drive shaft cover as it can help to prevent tear propagation along a course defined by the slit.
The pliable section of the drive shaft cover may also be designed as a so-called hypotube, i.e., the slits may be cut in such a fashion, that a particular hypo-tube-design is provided in the pliable section of the drive shaft cover.
In one embodiment, the slits may have a closed course, completely surrounding the drive shaft cover and thereby cutting the drive shaft cover into several segments having no material bridges between them. The segments can be connected to each other for instance by having protrusions of one segment lying inside recesses of a neighboring segment, resembling pieces of a jigsaw-puzzle. It is also possible to have disconnected segments that are only held together by the flexible tube.
In the case of disconnected segments or in some designs, in particular some known hypotube-designs, the pliable section may be limp, i.e. the drive shaft cover itself will not restore its original shape after deformation. In this case, the flexible tube may have a “memory” characteristic and help restore the original shape of the drive shaft cover.
The slits of the pliable section may be designed to limit bending of the pliable section, i.e. allow bending only up to a given minimal bending radius.
Thus bending can be ensured and in some cases also be limited by the width and the course of the slits. Thereby the minimal bending radius can be limited to a bending radius which does not permanently deform or kink the drive shaft.
Having one or more slits or holes can have the effect that blood may penetrate through the slits or holes. It can be a desired feature to enable a flow of blood, for instance from the inside of the drive shaft cover to the outside.
In some embodiments, a flexible tube may be provided around the pliable section of the drive shaft cover. The flexible tube can for instance be a shrink hose. The flexible tube can be used for tuning the bending properties of the pliable section, for instance stiffening the pliable section to a desired degree.
The flexible tube may comprise a polymer or be made of a polymer. In particular it may comprise or be made of silicone and/or Pebax® and/or PU and/or PET.
If one or more openings such as holes or slits are provided, the one or more openings may be covered by the flexible tube at least in part.
It is possible to leave a section or a subset of the one or more openings uncovered, to locally enable the above-described flow of blood. In particular, the flexible tube may be designed to leave a distal portion of the at least one opening uncovered. Thereby, blood can enter between the drive shaft and the drive shaft cover from within the hollow space of the rotor and can be delivered up to the most distal opening within the drive shaft cover. Thus blood can circulate along the drive shaft to prevent overheating and blood stasis.
Additionally or alternatively, the flexible tube may comprise one or more holes to allow fluid communication with a portion of the at least one opening to enable the above-described flow of blood.
Additionally or alternatively, fluid communication enabling a flow of blood as described above may be provided by having one or more venting holes in the drive shaft cover, the venting holes connecting the inside of the drive shaft cover and the outside of the drive shaft cover. The venting holes may for instance be provided in a region where the flexible tube is not provided, in particular distally from the flexible tube. The venting holes may have a design that is different from the design of the openings, In particular, the venting holes, as opposed to the openings, do not have to render the drive shaft cover pliable. Therefore, the venting holes may have a design that can be optimized for the envisioned through-flow of blood. Furthermore, in the case of the venting holes, the design can be such that clogging and suction of tissue into the venting holes can be avoided. In other words, if venting holes are provided, all of the openings of the pliable section may be covered and a blood flow can still be ensured. This way, both the venting holes and the openings can both be optimized with regard to their primary purpose. The venting holes may for instance have a circular or elliptical shape or they may be designed as slits having a course with an axial component or only an axial component.
In one embodiment, a distal end of the drive shaft cover lies within the end part, with a portion of the drive shaft cover extending into the end part. The drive shaft cover may comprise a distal section with a diameter that is larger than a diameter of a section of the drive shaft cover lying proximally thereof. Said distal section may be designed to lie entirely or in part inside the end part.
The section lying proximally of the distal section may be the section lying distally of the proximal section, amounting to a total of three sections with different outer diameters. I.e., in a possible embodiment of the catheter device, there is a proximal section (extending into the hollow space) with a first outer diameter, a pliable section lying distally thereof, with a second (increased) outer diameter, and a distal section extending into the end part, with a third (further increased) outer diameter. The outer diameter of the distal section may be at least 1.15 mm, preferably at least 1.25 mm and/or at most 2 mm, preferably at most 1.8 mm, particularly preferably at most 1.6 mm.
An inner diameter of the drive shaft cover may also vary over the length of the drive shaft cover. For instance, at the proximal end of the drive shaft cover, the diameter may be reduced with respect to an inner diameter of the drive shaft cover at the distal end of the drive shaft cover. The reduction in diameter may for instance occur between the proximal section and the section lying distally thereof. The inner diameter may be reduced by at least 0.02 mm and/or by at most 0.12 mm. The inner diameter can for instance be kept constant along the pliable section and the distal section. A gap between the drive shaft and the drive shaft cover may be kept particularly small in the proximal section to keep the rotor and the drive shaft cover concentrically aligned. In particular, a difference in diameter between the inner diameter of the drive shaft cover in the proximal section and the outer diameter of the drive shaft may be chosen to be 0.1 mm or less, preferably 0.06 mm or less, particularly preferably 0.03 mm or less.
The drive shaft cover may comprise MP35N, 35NLT and/or ceramics and/or a diamond-like-carbon coating.
The drive shaft cover may be manufactured from a single piece. In particular it may be designed as a single piece. It is however also possible, that slits are cut into the drive shaft cover such that several segments are formed. These segments may be held together but not connected to each other in the sense that no material bridges of the material of the drive shaft cover exist (see above). These slits can be cut into an originally provided single piece. The heat conductivity can depend on the course of the slits. In particular, advantageous heat conducting properties can be provided by having more material bridges.
The drive shaft cover may have heat conducting properties enabling a heat transfer away from the end part.
The end part may comprise an atraumatic tip. The end part can for instance be made of a polymer. It can have an elongated portion, wherein the atraumatic tip is provided distally thereof. The atraumatic tip can be attached to the elongated portion, in particular the elongated portion and the atraumatic tip can be designed as a single piece. The atraumatic tip can for instance be a pigtail.
The drive shaft is typically flexible. The drive shaft can be made up of a plurality of coaxial windings, preferably with different winding directions, particularly preferably with alternating winding directions, running spirally around a cavity extending axially along the drive shaft. For example, a drive shaft can comprise two coaxial windings, with opposite winding directions, and an outer diameter of the drive shaft can lie between 0.4 mm and 2 mm, preferably lies between 0.6 mm and 1.2 mm, particularly preferably between 0.8 mm and 1.0 mm.
In the distal end region, the drive shaft is in some embodiments reinforced by a reinforcement element, for example a metal wire or a carbon wire, that is provided in the cavity extending axially along the drive shaft. In one embodiment, the reinforcement element extends from an area near the proximal end of the rotor housing, in particular from a proximal bearing configuration of the rotor housing to the distal end of the drive shaft. In one embodiment the metal wire is made of 1.4310 stainless steel.
The flexible tube can for instance be made of a flexible material such as silicone, Pebax®, PU or PET. In one embodiment, the flexible tube of the drive shaft cover is a shrink hose. The flexible tube of the drive shaft cover can also be provided on the outside of the end part, extending beyond the end part proximally of the end part. Alternatively or additionally, a flexible tube of the drive shaft cover is provided in part inside the end part, extending beyond the end part proximally of the end part. As the drive shaft bends during operation, the drive shaft cover is sufficiently flexible to avoid a kink in the drive shaft between the drive shaft cover and the rotor. Its elasticity can also allow the drive shaft cover to bend. The bending stiffness is typically mostly defined by the drive shaft cover and the drive shaft.
In another alternative embodiment, the flexible tube can be provided around the drive shaft cover, proximally of the end part and in a manner distanced from the end part. In this case, one or more openings of the drive shaft cover can be provided in a section of the drive shaft cover which lies between the end part and the flexible tube. I.e., these openings are not covered by the flexible tube. In this case, a stream of blood between the inside of the drive shaft cover and the outside of the drive shaft cover can be enabled through the uncovered openings. In particular, the openings can be the aforementioned openings of the drive shaft cover which are at the same time configured to ensure flexibility of the drive shaft cover. This configuration can also be useful in embodiments that do not feature the rotor with the hollow space as described above. It is also possible to provide holes or openings in the flexible tube to allow for a stream of blood between the inside of the drive shaft cover and the outside of the drive shaft cover, while providing the flexible tube for instance along the whole length of the drive shaft cover or along the whole length of the portion having openings.
In one embodiment, the drive shaft cover comprises a spiral sleeve on the inside of the flexible tube for bearing the drive shaft. The spiral sleeve supports the flexible tube of the drive shaft cover from the inside, while ensuring flexibility. With such a spiral sleeve, friction between the drive shaft and the drive shaft cover, as well as wear and tear on the drive shaft cover, can be reduced.
In another embodiment, the drive shaft cover comprises a heat conducting part, or several heat conducting parts, designed to conduct heat away from the drive shaft and/or conduct heat away from the distal bearing. For instance, the heat conducting part can be configured to transfer heat to the blood of the patient during operation and/or to distribute the heat to avoid local hotspots.
The heat conducting part or the heat conducting parts may have an inner side, facing the drive shaft, and an outer side, facing away from the drive shaft.
The heat conducting part may be designed as a tube surrounding the drive shaft. The heat conducting part can for example also be designed as one or more metal plates or tongues which are provided near the drive shaft.
The spiral sleeve and the heat conducting part or tube can each be provided in separate embodiments, for instance in conjunction with a flexible tube. An embodiment featuring both a spiral sleeve and a heat conducting part designed as a tube can be particularly advantageous.
The spiral sleeve can for example be provided in conjunction with a heat conducting part, both with or without the flexible tube. For instance, the spiral sleeve can be arranged at least in part inside the heat conducting part designed as a tube, typically extending out of the tube.
The spiral sleeve and the heat conducting part can also be designed as a single piece. The spiral sleeve can be the pliable section of the drive shaft cover.
The spiral sleeve can for instance be made of round wire or it can be made of flat tape with a winding. The drive shaft is then also rotatably mounted within the spiral sleeve. The bearing spiral sleeve is preferably made of metal, for instance made of MP35N® or 35NLT®, or made of ceramics. The bearing spiral sleeve ensures the flexibility of the drive shaft cover to tolerate bending of the pump head, thus avoiding a kink between the distal bearing and the rotor, and providing sufficient resistance to wear and tear. Thus bending is ensured and in some cases also limited by the defined gap between adjacent windings of the spiral sleeve. Thereby the minimal bending radius can be limited to a bend radius which does not permanently deform or kink the drive shaft. In one embodiment, the flexible tube is provided around the full length of the spiral sleeve. In one embodiment, the flexible tube is provided only around a proximal portion of the spiral sleeve. In one embodiment, the flexible tube is provided around the outside of a portion of the end part and around a portion of the spiral bearing extending out of the end part.
Alternatively, an embodiment of multiple metal rings instead of a spiral is possible, preferably arranged with gaps between the rings. Preferably the rings or the sleeve are made of flat tape. The rings can be made of the same material as the spiral sleeve described above.
A spiral sleeve or rings for bearing a drive shaft have an inner diameter ranging between 0.4 mm and 2.1 mm, preferably between 0.6 mm and 1.3 mm, particularly preferably between 0.8 mm and 1.1 mm. The tape forming the spiral sleeve or rings has a thickness between 0.05 mm and 0.4 mm. The tape forming the spiral sleeve or the rings can for instance have a width between 0.4 and 0.8 mm. The gap between the rings or between the windings can for instance be between 0.04 mm and 0.2 mm.
The winding slope of the spiral sleeve and the thickness of the flexible tube, which influence the flexibility of the drive shaft cover, are preferably chosen such that the rotor can be kept at the desired position upon bending of the catheter device.
The thickness of the flexible tube can be between 5 μm and 100 μm, preferably between 10 μm and 50 μm.
In one embodiment, the inner diameter of the spiral sleeve or rings is chosen to be between 0.01 mm and 0.08 mm larger than the outer diameter of the drive shaft, preferably between 0.01 mm and 0.05 mm, for mounting the drive shaft rotatably and avoiding vibrations, while allowing at most small amounts of blood to enter the gap region.
In one embodiment, the proximal end of the spiral sleeve or rings, is located close to the rotor in the expanded state. For instance, the proximal end of the spiral sleeve or rings can be designed to have a distance of between 0.2 mm and 0.7 mm from the rotor in the expanded state, preferably a distance between 0.25 mm and 0.4 mm, to avoid that the rotor touches the drive shaft cover or spiral sleeve during operation.
Preferably, the flexibility of the drive shaft cover is such that upon bending of the pump head, the drive shaft and the rotor remain centered within the flexible housing, to avoid that the rotor touches the flexible housing during operation.
In one embodiment, a hub of the rotor extends less than 0.5 mm past the rotor blades in the distal direction, in order to be able to bring the rotor blades closer to the distal bearing without the hub potentially touching parts of the distal bearing. Preferably, it extends less than 0.1 mm in distal direction past the rotor blades, particularly preferably the hub does not extend at all past the rotor blades on the distal side.
In one embodiment, the winding direction of the spiral sleeve, when following the winding of the sleeve in the distal direction, when looking from the proximal end to the distal end of the bearing sleeve, is the opposite direction of a preferred rotating direction of the drive shaft, when looking along the drive shaft towards the distal end of the drive shaft, such that a tapered or pointed end of the spiral sleeve would not damage a rotor rotating in the preferred rotating direction if the rotor touches the spiral sleeve in the event of failure. The preferred winding direction can be the same direction as the winding direction of the outermost coaxial winding of the drive shaft or it can be the opposite direction from the winding direction of the outermost coaxial winding of the drive shaft.
The ends of the spiral sleeve are preferably face ground and the edges, at least the edges of both ends, are rounded and smooth, preferably with a ten-point mean roughness Rz of Rz≤2 μm, according to the ISO 1302 standard.
In another embodiment, a proximal section of the drive shaft cover is provided proximally of the spiral sleeve, the proximal section extending into the hollow space of the rotor. This means that the ends of the spiral sleeve are protected by the proximal section of the drive shaft cover.
Preferably, the spiral sleeve and/or the drive shaft cover is arranged in such a manner, that, if a force is exerted at the proximal end of the catheter device to transfer the rotor and the housing into a cannula under compression, such that a relative motion of the drive shaft with respect to the distal bearing and therefore the spiral sleeve or the drive shaft cover is effected. The relative motion is for instance due to a change in length of the housing which is effected by compression of the housing, as described above. The distal end of the drive shaft can remain within the distal bearing at all times, i.e., depending on the embodiment, the distal end does not escape the drive shaft cover, the spiral sleeve, the ceramic bearing or the heat conducting tube.
In one embodiment, an additional ceramic bearing is provided within the distal bearing, located distally of the spiral sleeve.
As mentioned earlier, the catheter device can comprise a heat conducting part or tube in addition to the spiral bearing or the catheter device can comprise a heat conducting part or tube solely in combination with a bearing.
If the heat conducting part or tube is provided without the spiral bearing, a ceramic bearing, for example a ring bearing, can be provided inside the distal bearing.
If the heat conducting part or tube is provided in addition to the spiral sleeve, it can be provided around at least a portion of the spiral sleeve.
The heat conducting part or tube can lie in part within the end part and in part outside of the end part. Thus, heat transfer from within the distal bearing to the blood of the patient is enabled. In one embodiment, the heat conducting part or tube extends between 0.5 mm and 2 mm out of the end part, preferably between 1 mm and 1.5 mm.
The flexible tube of the drive shaft cover can be provided around the spiral bearing on the inside of the heat conducting part or tube. Then, an outer side of the heat conducting part or tube can be brought in direct contact with the blood of the patient.
The flexible tube can also be provided around the outside of a portion of the end part, the outside of a portion of the heat conducting part or tube extending out of the end part, and a portion of the spiral sleeve that extends beyond the heat conducting part or tube. In the latter configuration, the part of the heat conducting part or tube, which extends out of the end part, cannot be brought in direct contact with the blood. Rather, the flexible tube is in direct contact with the blood. In this configuration, heat is also transferred from the heat conducting part or tube to the blood, through the thin walls of the flexible tube.
The heat conducting part or tube can also lie entirely within the end part, such that the heat is redistributed within the distal bearing and conducted away from the spiral bearing or the rings.
The heat conducting part or tube is for instance made of a medical grade stainless steel, such as 1.4441 stainless steel, and possesses a higher thermal conductivity than the end part or the ceramic bearing.
An inner diameter of the heat conducting part designed as a tube can lie between 0.5 mm and 2.6 mm, preferably between 0.7 mm and 1.8 mm, particularly preferably between 0.9 mm and 1.6 mm.
The thickness of the heat conducting part or tube can be between 0.05 mm and 0.5 mm.
The section of the outer surface of the heat conducting part or tube which is configured to be in contact with the blood of a patient is preferably smooth.
In one embodiment, the ten point mean roughness Rz according to the ISO 1302 standard in said section or portion of the outer surface of the heat conducting part is Rz≤1.2 μm.
In one embodiment, the inner side of the heat conducting part or tube is configured to be glued to the spiral sleeve. To facilitate gluing the inner side of the heat conducting part or tube to the spiral sleeve, the inner side of the part or tube can be rough. For instance, the arithmetic average surface roughness of the inner side of the heat conducting part or tube can have an average surface roughness Ra according to the ISO 1302 standard of Ra≥0.8 μm.
In one embodiment, the inner diameter of the heat conducting part designed as a tube is chosen to be between 0.04 mm and 0.1 mm larger than the outer diameter of the spiral sleeve or the rings so that glue can be applied in the gap.
Such catheter pumps with a heat conducting part or tube can result in shifting of the temperature hot-spot. For example, the hot spot can be shifted from a region of the drive shaft that lies inside the end part to a closer to the proximal end of the end part, or to a region which lies outside of the end part.
Such a setup can also result in a lower maximum temperature, for example a maximum temperature which is between 20° C. and 60° C. lower than the maximum temperature in a setup without heat conducting part. In particular, the maximum temperature at the hotspot can be kept below the melting point of Pebax® or other medical grade polymers.
It is also possible to provide a catheter device which features a heat conducting part or tube as presented here, but where the distal bearing does not feature a spiral sleeve or rings.
The present application may further relate to a drive shaft cover as described above or below, and/or to a bearing system comprising the drive shaft cover and the flexible tube.
Aspects and embodiments of the catheter device according to the application are exemplified in
The heat conducting part (13), which can be designed as a tube, can be provided inside the polymer end part 10 independently from the spiral sleeve 14, for example if a different kind of bearing or no additional sleeve for bearing the drive shaft 4 is envisioned.
The distal bearing 9 is provided for bearing the distal end of the drive shaft 4. The distal bearing 9 comprises the end part 10 and the drive shaft cover 11. The drive shaft cover 11 covers a section of the drive shaft 4 which extends between the rotor 2 and the end part 10. The drive shaft cover 11 thereby covers said section of the drive shaft 4 along a whole length of the section.
On a distal side of the rotor 2, a radially inner part of the rotor 2, in particular of the rotor hub 2.1 is axially recessed with respect to radially outer parts of the rotor 2 and the rotor hub 2.1 to form a hollow space 2.3 surrounding the drive shaft 4. The hollow space 2.3 is cylindrical and open towards the distal side. A proximal end of the drive shaft cover 11 lies in the hollow space 2.3. The section of the drive shaft 4 which protrudes from the drive shaft cover 11 at its proximal end is therefore protected by the portions of the rotor 2 surrounding it.
A proximal section 11.1 of the drive shaft cover 11 partially lies within the hollow space 2.3. The proximal section 11.1 has a first outer diameter. Distally thereof, a second central section 11.2 of the drive shaft cover 11 is provided with a second diameter that is larger than the first diameter. The central section 11.2 comprises one or more openings 11.4 to make it pliable. A distal section 11.3 is provided distally of the central pliable section 11.2. The distal section 11.3 has a third diameter which is larger than the second diameter and extends into the end part 10. A portion of the distal section 11.3 thereby remains outside of the end part 10 to enable efficient heat transfer away from the end part. Heat conductivity is enhanced in this version, since the drive shaft cover 11 is designed as a single heat conducting piece.
The housing 3, the drive shaft 4 and the drive shaft cover 11 as shown in
The drive shaft cover 11 comprises metal, for example 35NLT® and/or MP35N®, and/or ceramics and/or a diamond-like-carbon coating. It is manufactured from a single piece and designed as a single piece.
It is also possible to have a drive shaft cover with a different design extend into the hollow space 2.3 of the rotor 2. For instance it is possible, to have the hollow space of the rotor in combination with one of the drive shaft covers shown in
In the Example from
The flexible tube 12 from
The hollow space 2.3 has a length lh of between 0.9 mm and 1.1 mm. A penetration depth p of the proximal section 11.1 into the hollow space is between 0.3 mm and 0.7 mm, leaving some space between the proximal end of the drive shaft cover 11 and the rotor 2 to avoid touching of the parts.
Thereby, the penetration depth p is chosen such that lengthening of the housing 3 as shown for instance in
Typically, a distance of at least 0.3 mm and at most 0.6 mm is provided in axial direction between the parts as an axial gap (lh−p). The axial gap allows for clearance under the expected bending loads occurring during use of the pump.
A radial gap between the parts of the rotor 2 radially delimiting the hollow space 2.3 and an outer surface of the drive shaft cover is between 0.07 mm and 0.13 mm to avoid touching of the parts upon for example ovalization of the rotor 2, i.e., ovalization of the rotor hub 2.1. It is advantageous to keep a diameter dh of the cylindrical hollow space 2.3 as small as possible. A constraint for an inner diameter di1 of the proximal section 11.1 of the drive shaft cover 11 is however given by the diameter of the drive shaft 4. A wall thickness w of the proximal section 11.1 of the drive shaft cover 11 is therefore chosen to be as small as possible. In this example, the wall thickness w is between 0.05 mm and 0.07 mm. Given a typical diameter of the drive shaft 4, the diameter dh of the hollow space may for instance be between 1.1 mm and 1.3 mm to achieve a radial gap given by dh−w−di1, having the above-described dimensions.
An inner diameter di1 of the drive shaft cover in the proximal section 11.1 is thereby chosen in accordance with an outer diameter of the drive shaft 4 to provide good bearing of the drive shaft 4 while enabling rotation of the drive shaft 4 without unnecessary wear and tear.
Some of the proximal section 11.1 remains outside of the hollow space 2.3. Thus, the diameter of the drive shaft cover 11 increases at a distance from a distal end of the rotor 2, depending on the length of the proximal section, for instance at least 0.3 mm away from the distal end of the rotor 2 (cf.
The slits 11.4 can be arranged such that a so-called hypotube-design is achieved. Examples of such hypotube-designs are for instance shown in
In the distal section, which is provided inside the end part 10, indentations are provided on the outside of the drive shaft cover. This way, a material of the end part, such as a polymer, may enter the indentations and thus form a particularly stable connection with the distal section 11.3.
In
Distally of the proximal section 11.1, a central section 11.2 is provided. The outer diameter d2 of the central section 11.2 is between 0.14 mm and 0.3 mm larger than d1. The length l2 of the central section 11.2 can be for instance between 5 and 8 mm.
The distal section 11.3 has a length l3 which can be between 5 and 8 mm and an outer diameter d3 which is larger than d2. The outer diameter d3 can be for instance between 1.25 mm and 1.6 mm. Furthermore, on the outer surface of the distal section 11.3, axial and circumferential grooves are realized for a solid connection to the end part 10.
In
The pitch of the spiral can also be chosen according to the desired bending properties. The pitch can therefore change along a length of the spiral, having a first pitch associated with a length first length p1 at the distal end of the spiral and a second pitch associated with a second length p2 at the proximal end of the spiral, wherein p1 is for example larger than p2. The pitch may also be kept constant in an embodiment of the drive shaft cover.
The pitch may be for instance between 0.5 mm and 0.8 mm.
The slit can be cut into the drive shaft cover 11 using a laser.
In the setup shown in
In one embodiment, the width of the slits arranged as in
The widths of the slits can be the same as in the case of the spiral slit and they can also be cut using a laser.
The distance r between the slits, as indicated in
In particular in a setup of this type, where the material of width r between the slits can be deformed, it is also possible to have more than two slits arranged at the same height, for instance three slits at the same height, each slit running around less than a third of the circumference, in this case having three bridges, for instance of the above-described width. Then, bending of the pliable section can be enabled via deformation of the material of width r between the slits, rather than deformation of the bridges. It is of course also possible to have more than three slits and three bridges, such as for instance four slits and four bridges.
The slit 11.4 is wide enough to provide play between the two segments, rendering the section pliable, more specifically, rendering the section limp. The section has a minimal bending radius that is limited by the play provided by the slit 11.4, i.e., bending is only possible to a certain degree, until the segments abut.
A restoring force for straightening the drive shaft cover after it has been bent can be provided for instance by providing the flexible tube 12 around the pliable section 11.2 of the drive shaft cover 11.
All of the stiffening elements 2.4 shown in
The stiffening elements 2.4 may be made of a bio-compatible material. They may comprise one or more of MP35N, 35NLT, Nitinol, stainless steel (in particular medical grade stainless steel), and ceramics.
An inner diameter dis of the stiffening element 2.4, in the case of each of the embodiments shown in
An outer diameter dos may be chosen to be smaller than an outer diameter of the hub 2.1 of the rotor.
A wall thickness of the stiffening element, may, in each case, be for instance at least 0.03 mm, preferably at least 0.04 mm and/or at most 0.08 mm, preferably at most 0.07 mm.
In the case of
The section having through-holes, which can extend proximally of the hollow space 2.3 can be completely surrounded by the material of the rotor. The material of the rotor may penetrate through the through-holes, enabling a particularly reliable connection between the rotor 2 and the stiffening element 2.4. A cross section of the holes is circular. It is however not limited to this specific geometry. They may be circular or polygonal. The holes have a diameter of between 0.03 mm and 0.5 mm.
The application further relates to the following aspects:
| Number | Date | Country | Kind |
|---|---|---|---|
| 19158904.3 | Feb 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/054626 | 2/21/2020 | WO | 00 |
