Cardiovascular assist pump having an impeller with variable flow area

Abstract

The present disclosure is generally directed to mechanical cardiovascular assist systems used in the medical field to assist in the movement of blood. In particular, the present disclosure is directed to an impeller having features that enable improved performance. The annular flow area around the rotating impeller may be variable along the axial length of the impeller. A first radial gap between a distal region of the impeller and a surrounding tubular housing may be larger or smaller than a second radial gap between a proximal region of the impeller and the surrounding tubular housing.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority benefit of U.S. Provisional Patent Application No. 63 / 078207, filed September 14, 2020, the entire disclosure of which is incorporated herein by reference in its entirety.

[0002] The present disclosure is generally directed to mechanical cardiovascular assist systems used in the medical field to assist the movement of blood. In particular, the present disclosure is directed to mechanical cardiovascular assist devices having features that enable improved performance, such as optimized flow areas between impeller blades or shafts or other components and surrounding inlet tubing, or optimized spacing between certain stationary and moving parts. [Background technology]

[0003] [Description of Related Art] Mechanical circulatory assist devices are used to assist a patient's heart in moving blood throughout the body. They often consist of an electric motor, a tubular inflow cannula with an inflow region at its distal end and an outflow region at its proximal end, and an impeller rotated by the motor that moves blood through the tubular inflow cannula and out through the outflow region. A particular design challenge is optimizing blood flow while minimizing the risk of damage to the device or blood. Higher blood flows than those provided by current devices could improve outcomes for patients with mild cardiogenic shock or high-risk percutaneous coronary intervention patients. However, increased flow rates could also increase the risk of hemolysis or device damage.

[0004] Therefore, there is a need for improved mechanical circulatory support designs that allow for greater blood flow while avoiding the risk of hemolysis or device damage, among other improvements. Summary of the Invention

[0005] The present disclosure relates to a mechanical circulatory assist system having an impeller with a variable outer diameter or having a variable radial gap between the impeller blades or other components of the impeller, and a tubular cannula containing the impeller. Each of the embodiments disclosed herein has multiple aspects, no single one of which is solely responsible for the desirable properties of the present disclosure. Without limiting the scope of the present disclosure, its more prominent features will now be briefly described. After reviewing this description, and particularly after reading the section entitled "Detailed Description of the Invention," one will understand how the features of the embodiments described herein provide advantages over existing systems, devices, and methods of mechanical circulatory assist systems.

[0006] The following disclosure describes non-limiting examples of some embodiments of mechanical circulatory assist devices. For example, other embodiments of the disclosed systems and methods may or may not include features described herein. Furthermore, the disclosed benefits and advantages may only apply to certain embodiments and should not be used to limit the disclosure.

[0007] A first aspect of the present disclosure is a mechanical circulatory assist device including a tubular cannula including an inflow region, an outflow region, and a distal impeller region, and an impeller having a proximal end and a distal end, wherein the impeller is disposed within the tubular cannula at least partially within the outflow region and at least partially within the distal impeller region, wherein a radial gap between the impeller and an inner surface of the tubular cannula varies in size between the proximal end and the distal end, and the size of the radial gap at a particular location between the proximal end and the distal end comprises a radial distance between a maximum impeller width and the inner surface of the tubular cannula at the particular location.

[0008] A second aspect of the present disclosure relates to the device of aspect 1, wherein the impeller includes a distally tapered portion that tapers distally from a first diameter to a distal diameter, the distal diameter being smaller than the first diameter.

[0009] A third aspect of the present disclosure relates to the device of aspect 2, wherein the impeller includes a constant diameter portion extending proximally from the distally tapered portion, the constant diameter portion having a first diameter.

[0010] A fourth aspect of the present disclosure relates to the device of aspect 3, wherein the constant diameter portion extends at least partially within the distal impeller region and at least partially within the outflow region.

[0011] A fifth aspect of the present disclosure relates to the device of either aspect 3 or aspect 4, wherein the constant diameter portion extends from the distally tapered portion to the proximal end of the impeller.

[0012] A sixth aspect of the present disclosure relates to the device of either aspect 3 or aspect 4, wherein the impeller includes a proximal narrowed diameter portion proximal to the constant diameter portion, the proximal narrowed diameter portion having a narrowed diameter smaller than the first diameter.

[0013] A seventh aspect of the present disclosure relates to the device of aspect 6, wherein the narrowed diameter is 0.15 mm to 0.35 mm smaller than the first diameter.

[0014] An eighth aspect of the present disclosure relates to the device of any one of aspects 6-7, wherein the radial gap of the proximal narrowed diameter portion is approximately 0.20 mm greater than the minimum radial gap in the distal impeller region.

[0015] A ninth aspect of the present disclosure relates to the device of any one of aspects 6-7, wherein the radial gap of the proximal narrowed diameter portion is approximately 0.125 mm greater than the minimum radial gap in the distal impeller region.

[0016] A tenth aspect of the present disclosure relates to the device according to any one of aspects 2 to 9, wherein the radial gap is 0.095 mm to 0.125 mm at the distal diameter.

[0017] An eleventh aspect of the present disclosure relates to the device according to any one of the second to tenth aspects, wherein the radial gap is 0.060 mm to 0.090 mm at the first diameter.

[0018] A twelfth aspect of the present disclosure relates to the device according to any one of aspects 2 to 11, wherein the distal diameter is 0.40 mm to 0.100 mm smaller than the first diameter.

[0019] A thirteenth aspect of the present disclosure relates to the device according to any one of aspects 2 to 12, wherein the slope of the tapered portion is about 0.0117.

[0020] A fourteenth aspect of the present disclosure relates to the device according to any one of aspects 2 to 13, wherein the inner diameter of the tubular cannula is 4.39 mm to 4.45 mm.

[0021] A fifteenth aspect of the present disclosure relates to the device according to any one of aspects 2 to 14, wherein the length of the impeller is 7.5 mm to 8.5 mm.

[0022] A sixteenth aspect of the present disclosure relates to the device according to any one of aspects 2 to 15, wherein the proximal end of the impeller is attached to a drive shaft.

[0023] A seventeenth aspect of the present disclosure relates to the device according to any one of aspects 2 to 16, wherein the distal end of the impeller is a free end.

[0024] An eighteenth aspect of the present disclosure relates to the device of any one of aspects 2-17, further including a motor housing, the motor housing coupled to the proximal end of the inlet cannula.

[0025] A nineteenth aspect of the present disclosure relates to the apparatus of aspect 1, further including a driving magnetic rotor, wherein the impeller is coupled to the driving magnetic rotor.

[0026] A twentieth aspect of the present disclosure relates to the device of aspect 19, further comprising a bearing configured to hold the distal end of the impeller in the axial center of the tubular cannula.

[0027] A twenty-first aspect of the present disclosure relates to the device according to aspect 20, wherein the bearing comprises a plurality of spokes configured to connect the bearing to the tubular cannula and maintain the position of the bearing relative to the tubular cannula.

[0028] A twenty-second aspect of the present disclosure relates to the device of any one of aspects 19 to 21, wherein the driving magnetic rotor is positioned at least partially in the outflow region.

[0029] A twenty-third aspect of the present disclosure relates to a device described in any one of aspects 19 to 22, wherein the radial gap between the impeller and the inner surface of the tubular cannula is larger in the outflow region than in the distal impeller region.

[0030] A 24th aspect of the present disclosure relates to a device described in any one of aspects 19 to 23, wherein the radial gap between the impeller and the inner surface of the tubular cannula is 2 to 3 times larger in at least a portion of the outflow region than in the distal impeller region.

[0031] A twenty-fifth aspect of the present disclosure relates to the device of any one of aspects 19 to 22, wherein the impeller comprises a constant diameter.

[0032] A 26th aspect of the present disclosure relates to a device described in any one of aspects 19 to 25, wherein the impeller includes a first diameter in the distal impeller region and the driving magnetic rotor includes a second diameter in the outlet region that is smaller than the first diameter.

[0033] A 27th aspect of the present disclosure relates to the device described in aspect 26, wherein a radial gap between the impeller and the inner surface of the tubular cannula at the first diameter position is larger than a second radial gap between the driving magnetic rotor and the tubular cannula at the second diameter position.

[0034] A twenty-eighth aspect of the present disclosure relates to the device according to the twenty-seventh aspect, wherein the radial gap between the impeller and the inner surface of the tubular cannula at the first diameter is between 0.065 mm and 0.150 mm.

[0035] A 29th aspect of the present disclosure relates to the device of either aspect 27 or 28, wherein the second radial gap is 2 to 3 times larger than the radial gap between the impeller and the inner surface of the tubular cannula at the first diameter.

[0036] A thirtieth aspect of the present disclosure is a mechanical circulatory assist device including a tubular cannula including an inflow region, an outflow region, and a distal impeller region, and an impeller located within the tubular cannula in a portion of the outflow region and a portion of the distal impeller region, wherein a first radial gap between the impeller and the distal impeller region is smaller than a second radial gap between the impeller and the outflow region of the tubular cannula.

[0037] A thirty-first aspect of the present disclosure relates to the device of aspect 30, wherein the outflow region comprises one or more struts.

[0038] A thirty-second aspect of the present disclosure relates to a device described in any one of aspects thirty to thirty-one, wherein the impeller has a first diameter in the distal impeller region and a second diameter in the outflow region, the second diameter being smaller than the first diameter.

[0039] A thirty-third aspect of the present disclosure relates to the device according to aspect thirty-second, wherein the first diameter is in the range of 3.8 mm to 5.92 mm.

[0040] A thirty-fourth aspect of the present disclosure relates to the device according to aspect 32 or 33, wherein the second diameter is within the range of 0.5 mm to 5.92 mm.

[0041] A thirty-fifth aspect of the present disclosure relates to the device of any one of aspects thirty-second to thirty-fourth, wherein the transition from the first diameter to the second diameter is a step transition.

[0042] A thirty-sixth aspect of the present disclosure relates to the device of any one of aspects thirty-second to thirty-fourth, wherein the transition from the first diameter to the second diameter is a sloped transition.

[0043] A thirty-seventh aspect of the present disclosure relates to the device of any one of aspects thirty-second to thirty-fourth, wherein the transition from the first diameter to the second diameter is a curved transition.

[0044] A thirty-eighth aspect of the present disclosure relates to the device according to any one of aspects thirty to thirty-first, wherein the impeller has a constant diameter.

[0045] A thirty-ninth aspect of the present disclosure relates to the device of any one of aspects thirty-three-first or thirty-eighth, further comprising an insertion sleeve located within the distal impeller region.

[0046] A fortieth aspect of the present disclosure relates to the device of aspect 39, wherein the insertion sleeve includes a chamfered distal end and a chamfered proximal end.

[0047] A forty-first aspect of the present disclosure relates to the device of any one of aspects 39 or 40, wherein the insertion sleeve is made of PEEK.

[0048] A forty-second aspect of the present disclosure relates to the device of any one of aspects 39 to 41, wherein the insertion sleeve includes an inner surface having a lubricious coating.

[0049] A forty-third aspect of the present disclosure relates to the device according to any one of aspects thirty to forty-second, wherein the first radial gap is in the range of 0.04 mm to 0.5 mm.

[0050] A forty-fourth aspect of the present disclosure relates to the device according to any one of aspects thirty to forty-third, wherein the second radial gap is in the range of 0.04 mm to 3 mm.

[0051] A forty-fifth aspect of the present disclosure relates to the device according to any one of aspects thirty to forty-four, wherein the impeller is connected to a drive shaft of the motor.

[0052] A forty-sixth aspect of the present disclosure relates to the device according to any one of aspects thirty to forty-four, wherein the impeller is magnetically coupled to the motor.

[0053] A forty-seventh aspect of the present disclosure relates to the device of any one of aspects thirty to forty-six, wherein the impeller includes at least two impeller blades.

[0054] A forty-eighth aspect of the present disclosure relates to the device of any one of aspects 30-47 in combination with aspect 31, wherein the strut has a thickness greater than a thickness of the tubular cannula.

[0055] A forty-ninth aspect of the present disclosure relates to the device of any one of aspects thirty to thirty-seven, wherein the impeller comprises impeller blades in the distal impeller region, and the device further comprises a radially symmetric conical shape in the outlet region.

[0056] A fiftieth aspect of the present disclosure relates to the device of aspect 49, wherein the radially symmetric conical shape has an electropolished surface.

[0057] A fifty-first aspect of the present disclosure relates to the device of any one of aspects 49 or 50, wherein the radially symmetric conical shape comprises a concave surface.

[0058] A fifty-second aspect of the present disclosure relates to the device according to any one of aspects 49 to 51, wherein the radially symmetric conical shape comprises a convex surface.

[0059] A fifty-third aspect of the present disclosure relates to the device according to aspect 52 in combination with aspect 51, wherein the convex surface is proximal to the concave surface.

[0060] A fifty-fourth aspect of the present disclosure relates to the device of any one of aspects forty-ninth to fifty-third, wherein the radially symmetric conical shape is affixed to or is part of the impeller shaft.

[0061] A fifty-fifth aspect of the present disclosure relates to the device of any one of aspects 49 to 53, wherein the radially symmetric conical shape is affixed to or is part of the motor housing or the tubular cannula.

[0062] A fifty-sixth aspect of the present disclosure relates to the device of aspect fifty-fifth, wherein the impeller shaft of the impeller passes through the cone-shaped bore.

[0063] A fifty-seventh aspect of the present disclosure relates to the device of aspect fifty-six, wherein the bearing is positioned between the impeller shaft and the conical shape.

[0064] A fifty-eighth aspect of the present disclosure relates to the apparatus of aspect fifty-six or fifty-seven, wherein the seal is positioned between the impeller shaft and the conical shape. [Brief explanation of the drawings]

[0065] The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. The present disclosure will be described with additional specificity and detail through the use of the accompanying drawings, with the understanding that these drawings illustrate only some embodiments in accordance with the present disclosure and should not be considered limiting of its scope. In the following detailed description, reference will be made to the accompanying drawings, which form a part hereof. In the drawings, like symbols typically identify like components unless the context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that aspects of the present disclosure, as generally described herein and illustrated in the drawings, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are expressly intended and made a part of this disclosure. [Figure 1] FIG. 1 is a schematic diagram of a mechanical circulatory support (MCS) device. [Figure 2A]FIG. 2A is a schematic diagram of a cutaway view of a portion of an MCS device. [Figure 2B] FIG. 2B is a cross section of the distal impeller region of FIG. 2A. [Figure 2C] FIG. 2C is a cross section of the outflow region of FIG. 2A. [Figure 3] FIG. 3 is a schematic diagram of an MCS device with a constant radial gap in the distal impeller region and in the outflow region. [Figure 4] FIG. 4 is a schematic diagram of an MCS device with minimized radial gap in the distal impeller region and a larger radial gap in the outflow region. [Figure 5] FIG. 5 is a schematic diagram of an MCS device with a minimized radial gap in the distal impeller region and a larger radial gap in the outlet region with an angled transition. [Figure 6] FIG. 6 is a schematic diagram of an MCS device having an impeller with a constant diameter and an insertion sleeve to minimize the radial gap in the distal impeller region. [Figure 7] FIG. 7 is a schematic diagram of an MCS device having an impeller with impeller blades in the distal impeller region and no impeller blades in the outlet region. [Figure 8] FIG. 8 is a schematic diagram of an MCS device having an impeller with impeller blades in the distal impeller region and a conical shape in the outlet region connected to the impeller. [Figure 9] FIG. 9 is a schematic diagram of an MCS device having impeller blades in the distal impeller region and an impeller with a conical shape in the outflow region that remains stationary relative to the motor housing and tubular cannula. [Figure 10] FIG. 10 is a schematic diagram of an MCS device having an impeller with a tapered distal portion. [Figure 11] FIG. 11 is a schematic diagram of an MCS device having an impeller with a tapered distal portion and a proximal narrowed portion. [Figure 12A]FIG. 12A is a schematic diagram of an MCS device having a variable radial gap between the impeller and the surrounding cannula or impeller housing and having a driving magnetic rotor. [Figure 12B] FIG. 12B is an enlarged view of a portion of FIG. 12A. DETAILED DESCRIPTION OF THE INVENTION

[0066] The disclosure herein relates to mechanical circulatory assist devices with features that can optimize their ability to move blood while minimizing the risk of damage to the device or blood. In particular, the disclosure relates to features of impellers or components intended to rotate, as well as their relationship to tubular inflow cannulas or components intended to remain stationary, and their outflow regions. The following detailed description is directed to certain embodiments. In this description, reference is made to the drawings, and for clarity, like parts or steps may be designated with like numerals throughout. References herein to "one embodiment," "an embodiment," or "in some embodiments" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the invention. The appearances of the phrases "one embodiment," "an embodiment," or "in some embodiments" in various places throughout the specification do not necessarily all refer to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. Additionally, various features are described that are exhibited by some embodiments and not by other embodiments. Similarly, various requirements are described that may be requirements in some embodiments but not in other embodiments. Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings.

[0067] 1, a mechanical circulatory support (MCS) device may include an inlet tube or tubular inflow cannula 4 having a proximal end 25 and a distal end 26, an inflow region 5 at the distal end, an outflow region 6 at the proximal end, and a motor 9 for driving an impeller 2 positioned at least partially within the tubular cannula. The rotating impeller draws blood through the inflow region 5 into the stationary inflow cannula 4 and pushes blood out of the device at least partially through the outflow region 6.

[0068] Figure 2A is an enlarged cutaway view of a portion of the MCS device of Figure 1. The outflow region 6 may include struts 8 connecting the tubular inlet cannula 4 to the motor housing 9. For example, the MCS device may have at least two struts 8 (e.g., three, four, or five struts). The outflow region 6 has an opening or window 7 in the tubular cannula defined by the struts 8. The inner or outer edges of the opening, or the cut surface of the opening 7, may be rounded (e.g., with a diameter of curvature equal to the thickness of the tubular inflow cannula, which may range from 0.10 to 0.15 mm). There is a very small radial gap 1a between the outer edges of the impeller blades 3 and the inner surface of the tubular inflow cannula 4. The rotating edges of the impeller blades 3 should not come into contact with the tubular cannula 4 to avoid mechanical wear, friction, loss of impeller speed, increased motor drag, heat generation, or other undesirable effects. However, to maximize efficiency and reduce hemolysis, it may be advantageous to have a minimal radial gap 1a between the impeller blades 3 and the inner surface of the cannula 4. Hemolysis is a form of blood damage that can be caused by hydraulic shear stress applied to blood cells. Hemolysis may be characterized by damaged hemoglobin, and a measure of hemolysis may include hemolytic damage potential (HDP), which corresponds to the ratio of free hemoglobin to the total amount of hemoglobin in a blood sample. The amount of hemolysis may depend on several factors, one of which may be impeller speed. Thus, generally, the higher the efficiency or flow rate generated by a given impeller speed, the higher the flow rate can be while minimizing hemolysis. The effect of minimizing the radial gap 1a may include minimizing reflow, a factor that affects efficiency. As a result, a smaller radial gap 1a between the impeller blades and the inner surface of the tubular cannula 4 may achieve a higher flow rate relative to hemolytic damage potential, promoting the generation of sufficient flow rate while causing acceptably low hemolysis.This applies to the distal impeller region 11, distal to the outflow region 6, where the impeller blades rotate in a rigid portion of the tubular cannula 4; for example, laser cutting is not performed to increase rigidity. Except for a minimal radial gap, blood must flow to the inner surface of the tubular cannula and the space defined by the impeller. At sufficient velocity, the helical pitch of the rotating impeller blades within the confined space defined by the tubular cannula creates a hydraulic operating point that forces blood to flow through the distal impeller region 11 toward the outflow region 6. The displacement of blood creates a pressure differential that draws blood into the inflow region 5 of the tubular cannula 4.

[0069] In the outflow region 6, rotating impeller blades direct blood flow through the outflow window 7. In the outflow region 6, where the tubular cannula 4 has an outflow opening or window 7 defined by struts 8, minimizing the radial gap 1b between the impeller blades 3 and the inner surface of the struts 8 may not contribute much to efficiency compared to the distal impeller region 11 due to flow turbulence that occurs as the blood flow interacts with the struts 8. In some embodiments, minimizing the radial gap 1b in the outflow region 6 may undesirably increase the potential for hemolytic damage, in part, due to hydraulic shear stress applied to blood cells in the space 1b between the impeller blades and the struts. Furthermore, minimizing the radial gap 1b may introduce challenges with very small manufacturing tolerances that can increase the risk of blade and strut contact during use, which can result in material wear, increased motor current, heat production, or other device damage, as well as increased hemolysis. Accordingly, aspects of the present disclosure relate to an MCS device design in which a first radial gap 1a between the impeller blades and the inner surface of the tubular cannula in the distal impeller region 11 is minimized (e.g., in the range of 0.04 mm to 0.5 mm), and a second radial gap 1b between the impeller blades and the inner surface of the strut 8 is larger than the first radial gap (e.g., in the range of 0.04 mm to 3 mm, larger than the first radial gap), which may reduce the risk of damage to the blood or the device itself during use and optimize efficiency.

[0070] One way to increase the second radial gap 1b is to decrease the diameter of the impeller blades in the outlet region 6 relative to the diameter of the impeller blades in the distal impeller region 11 while maintaining a constant inner diameter of the tubular cannula. With this approach, the larger the radial gap 1b, the smaller the diameter of the impeller blades in the outlet region. FIG. 2A shows an example of an impeller 3 having a first radius 27 in the distal impeller region 11 and a second radius 28 in the outlet region 6. FIG. 2B is a cross-sectional view of FIG. 2A at the distal impeller region 11, and FIG. 2C is a cross-sectional view of FIG. 2A at the outlet region 6. The impeller radius 27 is larger than the impeller radius 28, and as a result, the radial gap 1a is smaller than the radial gap 1b.

[0071] Figure 3 is a schematic cutaway view of a portion of an MCS device showing an impeller with a constant impeller diameter, which may represent some configurations in current MCS devices. For simplicity, impeller 2 is depicted as a cylinder, representing the outermost extent of at least two spirally angled impeller blades and showing diameter 13. Impeller 2 may have three or more impeller blades and is preferably radially balanced. The impeller blades may be substantially helical, have a varying pitch, or have multiple bends. Tubular cannula 4 may have an inner diameter 12, for example, in the range of 3.8 mm to 6 mm (e.g., 3.8 mm to 5 mm, or 4.3 mm to 4.5 mm). The impeller has a first diameter 13 in the distal impeller region 11 and a second diameter 14 in the outlet region 6. In Figure 3, first diameter 13 and second diameter 14 are equal, resulting in equal first gap 1a and second gap 1b.

[0072] In contrast to Figure 3, Figure 4 shows an impeller 2 depicted as a cylinder for simplicity, with a first diameter 13 in the distal impeller region 11 and a second diameter 15 in the outlet region 6, with the second diameter 15 being smaller than the first diameter 13. The resulting first gap 1a is minimized for optimal efficiency, e.g., in the range of 0.040 mm to 0.200 mm (e.g., in the range of 0.070 mm to 0.1 mm, approximately 0.075 mm), while the second gap 1b is larger than the first gap 1a, e.g., in the range of 1 to 50 times the size of the first gap 1a (e.g., in the range of approximately 0.040 mm to 2 mm, approximately 0.20 mm). The difference between the first diameter 13 and the reduced diameter 15 can be approximately 0.25 mm. The transition 16 between the first diameter 13 and the second diameter 15 can be a step, as shown in Figure 4. Alternatively, the transition may be a gradual slope 17, as shown in Figure 5. For example, the sloped transition 17 may have a rise vs. run or change in diameter vs. length of the slope ranging from 0.011 to 2 (e.g., 1). Additionally, the transition may be curved or have multiple bends (e.g., an S-shaped curve).

[0073] An alternative embodiment is shown in FIG. 6, which is a schematic diagram of a portion of an MCS device showing a cutaway view of an impeller 2 having a constant diameter, i.e., a first diameter 13 in the distal impeller region 11 equal to a second diameter 14 in the outflow region 6. The tubular cannula 4 has a constant outer diameter in the distal impeller region 11 and the outflow region 6. A sleeve 19 is inserted into the tubular cannula at least in the distal impeller region 11 but not in the outflow region 6. The sleeve 19 is intended to remain stationary relative to the inlet tube during use. The sleeve has an outer diameter that fits snugly over the inner diameter of the tubular cannula, optionally bonded, formed a fit, or press-fitted together, and an inner diameter that is slightly larger than the first impeller diameter 13 by a distance equal to the gap 1a. Because the sleeve 19 is not in the outflow region 6, the gap 1b is larger than the gap 1a by the thickness 18 of the sleeve 19, which can be in the range of, for example, 0.04 to 2 mm. Optionally, sleeve 19 has a distal end and a tapered or chamfered proximal end as shown to improve fluid flow. Optionally, sleeve 19 may be made of a high-density polymer such as PEEK to withstand wear when the impeller contacts the sleeve during use. Optionally, the inner surface of the sleeve may have a lubricious coating to further reduce hydraulic shear stresses in the blood.

[0074] Another embodiment is shown in Figure 7, a schematic diagram of a portion of an MCS device showing a cutaway view of an impeller 2 having impeller blades 3 in the distal impeller region 11 and no impeller blades in the outlet region 6. The impeller shaft 10 may be rod-shaped in the distal impeller region 11, from which the impeller blades 3 extend radially, and the rod-shaped shaft 10 may pass through the outlet region and connect to a motor drive shaft or rotor. A first radial gap 1a between the impeller blades 3 and the inner surface of the tubular cannula 4 may be in the range of 0.04 mm to 0.5 mm (e.g., 0.1 mm), and a second radial gap 1b, spanning the distance between the shaft 10 and the inner surface of the strut 8, may be in the range of 1.75 mm to 3 mm.

[0075] Alternatively, as shown in FIG. 8 , the shaft 10 may be rod-shaped in the distal impeller region 11, followed by a conical shape 30 in the outflow region. Optionally, the conical shape 30 may have a concave taper 31, which may facilitate directing blood flow through the fenestrations 7 in the outflow region 6. Optionally, the proximal portion of the conical portion of the shaft 30 has a convex curve 32. The first radial gap 1a between the impeller blades 3 and the inner surface of the tubular cannula 4 may be in the range of 0.04 mm to 0.5 mm (e.g., 0.1 mm). The second radial gap 1b is the distance between the conical shaft 30 and the inner surface of the strut 8, and the gap 1b at the point closest to the strut 8 may be in the range of 0.04 mm to 2 mm. Optionally, the conical shape 30 may have an electropolished surface.

[0076] Another embodiment is shown in FIG. 9, which is a schematic diagram of a portion of an MCS device showing a cutaway view of an impeller 2 having impeller blades 3 in the distal impeller region 11 and no impeller blades in the outflow region 6. Similar to the device shown in FIG. 8, there is a conical shape 35 in the outflow region. However, the conical shape 35 is not rigidly connected to the impeller shaft 10. Instead, the conical shape 35 is fixed relative to the tubular cannula 4 or the motor housing; for example, the conical shape 35 may be rigidly connected to the motor housing or the tubular cannula. The impeller shaft 10 passes through the conical shape 35. Optionally, a bearing or seal 36 may be positioned between the impeller shaft 10 and the conical shape 35. The conical shape may have a concave surface 37 that facilitates directing blood flow through the window 7. Optionally, the proximal portion of the conical shape 35 may have a convex surface (not shown). The first radial gap 1a between the impeller blades 3 and the inner surface of the tubular cannula 4 may be in the range of 0.04 mm to 0.5 mm (e.g., 0.1 mm). In the outflow region, the second radial gap between the cone shape 35 and the inner surface of the strut 8 may be only 0; in other words, the cone shape 35 may be connected to the strut 8 at its proximal end, and the distance between the cone shape 35 and the strut 8 may increase distally.

[0077] Another embodiment is shown in FIG. 10, which is a schematic diagram of a cutaway of a portion of an MCS device showing the impeller region. For simplicity, the impeller 2 is shown as a contour of the extent of the impeller's outer diameter. Such contour may refer to a geometric reference volume, which may be cylindrical, swept by the rotating impeller 2. Thus, the contour may be the maximum diameter of the impeller blades 3. The impeller 2 may have two or more impeller blades 3 and is preferably radially balanced. In some embodiments, the impeller 2 may be mounted on a drive shaft 10. As shown in FIG. 10, the impeller 2 is positioned within a tubular cannula 4 having an outlet region 6 and a distal impeller region 11, as shown in FIG. 2A. In contrast to other embodiments described herein, the first impeller diameter 13 of at least a portion of the distal region 11 is equal to the second impeller diameter 14 of the outlet region 6. In some embodiments, distal impeller region 11 may have a distally tapered portion 21 that tapers distally to the distal end of region 11. In other words, distal impeller region 11 may include distally tapered portion 21 located distally of constant diameter portion 22. Constant diameter portion 22 may extend proximally from distally tapered portion 21 at least partially within impeller region 11 and may extend into outflow region 6.

[0078] A first radial gap between the impeller 2 and the surrounding tubular structure in a first region may be larger than a second radial gap between the impeller 2 and the surrounding tubular structure in a second region, the second region being located proximal to the first region. The first diameter of the impeller 2 in the first region may be smaller than the second diameter of the impeller 2 in the second region, the second region being located proximal to the first region. The distal diameter 20 may be smaller than the first diameter 13. As used herein, "diameter," "width," "gap," etc., related to the impeller and surrounding structure may be measured relative to the maximum radial outer width of the impeller in that region, which, as described above, may be the outline of a geometric reference volume swept out by the rotating impeller 2.

[0079] In some embodiments, the diameter of the impeller in the distally tapered portion 21 may decrease from a maximum at the first diameter 13 to a relatively small distal diameter 20 over the length of the distally tapered portion 21. In some embodiments, the tapering of the distally tapered portion 21 may prevent contact between the distal aspect of the impeller 2 and the tubular inflow cannula 4. As shown in FIG. 10 , in some embodiments, the impeller 2 may be attached to the drive shaft 10 at its proximal end and not held by a bearing at its distal end. Furthermore, the tubular inflow cannula 4 may be cantilevered from the motor housing. In this configuration, the tubular inflow cannula 4 may deflect slightly, which may be more pronounced in the distal impeller region 11 compared to the outflow region 6. Also, there may be very small imperfections in the mounting of the impeller 2 such that its axis of rotation is precisely parallel and aligned with the axis of rotation of the drive shaft 10. These factors may contribute to the risk of contact between the impeller 2 and the cannula 4, particularly at the distal end of the impeller 2. The dimensions of the distal tapered portion 21 may be selected to reduce or eliminate the risk of contact while having a negligible effect on flow efficiency. These dimensions may depend on the length of the impeller 2 and the inner diameter of the cannula 4.

[0080] In one embodiment of the MCS device, the impeller 2 has a length between its proximal and distal ends in the range of 7.5 mm to 8.5 mm (e.g., 7.97 mm), and the inlet tube has an inner diameter in the range of 4.39 mm to 4.45 mm (e.g., approximately 4.42 mm), at least in the region where the impeller 2 is located. The difference between the first diameter 13 and the distal diameter 20 may be within the range of 0.040 mm to 0.100 mm (e.g., 0.050 mm to 0.090 mm, 0.060 mm to 0.080 mm, or approximately 0.070 mm). The first diameter 13 may be approximately 4.270 mm, the distal diameter 20 may be approximately 4.200 mm, and the length of the tapered portion 21 may be approximately 3 mm. Therefore, the slope of the tapered portion 21 may be (0.07 mm / 2) / 3 mm = 0.0117. The resulting radial gap between the impeller 2 and the cannula 4 may be constant, for example, at a constant diameter portion 22 in the range of 0.060 to 0.090 mm (e.g., about 0.075 mm), and may increase at the distal end of the impeller 2 to a gap in the range of 0.095 to 0.125 mm (e.g., about 0.110 mm), the impeller 2 having a distal diameter 20.

[0081] Optionally, the distally tapered portion 21 may taper with a linear slope. Alternatively, the reduction in diameter may be non-linear, for example, a concave, convex, or compound curve.

[0082] Optionally, as shown in FIG. 11 , the impeller 2 may have a distal tapered portion 21 and may further have a proximal narrowed diameter portion 23 at least partially aligned with the outflow region 6. This embodiment may have the advantage of reducing the risk of contact between the impeller 2 and the cannula 4. This embodiment may also have improved hemolysis in the outflow region 6. The narrowed diameter 15 of the narrowed diameter portion 23 of the impeller 2 may be in the range of 0.15 mm to 0.35 mm (e.g., about 0.25 mm) narrower than the first diameter 13. The radial gap between the impeller 2 and the cannula 4, or at least the outflow strut 8 at the narrowed diameter portion 23 (e.g., at the location of the narrowed diameter 15), may be about 0.20 mm, or about 0.125 mm, larger than the minimum radial gap in the distal impeller region 11 (e.g., at the location of the maximum diameter 13).

[0083] In some embodiments, the MCS device may have an impeller with a different configuration than that shown in FIG. 2A, with a variable radial gap between the impeller and the surrounding cannula or impeller housing. For example, FIG. 12A shows a partial cutaway view of a portion of an MCS device including impeller 2. The distal end of impeller 2 may be held axially centered in tubular inflow cannula or impeller housing 4 by bearing 43. Bearing 43 may have spokes connecting to the cannula or impeller housing 4, maintaining its position relative to the cannula or impeller housing 4. This may reduce or eliminate the risk of the distal end of impeller 2 contacting the cannula or impeller housing 4. In some embodiments, this configuration benefits from a reduced impeller diameter in the outflow region 6 to reduce hemolysis. Thus, the MCS device may have a first radial gap in the distal impeller region 11 and a second radial gap at least partially in the outflow region 6, the second radial gap being larger than the first radial gap, for example, as described in other embodiments herein. The first radial gap may be about 0.075 mm, and the second radial gap may be about 0.200 mm. In some embodiments, the second radial gap may be within a range of 2 to 3 times the first radial gap.

[0084] The impeller 2 may be configured to be coupled to the motor 9 using a non-contact magnetic coupling, as shown in FIG. 12 . To achieve the magnetic coupling, the impeller 2 may be coupled to a drive magnetic rotor 42 that surrounds a second magnetic rotor 44 attached to the drive shaft of the motor 9. Example embodiments of such a configuration are disclosed in International PCT Publication Nos. 2019 / 219874, 2019 / 219883, 2020 / 011795, 2020 / 011797, 2020 / 030700, and 2020 / 064911, and pending U.S. Provisional Patent Application No. 63 / 116,616, which are incorporated by reference herein in their entireties. The drive magnetic rotor 42 may be positioned within the outflow region 6, along with a portion of the impeller blades 3. In some embodiments, the cannula or impeller housing 4 surrounding the impeller 2 may have a constant inner diameter. Impeller 2 may have a first diameter 41, and drive magnetic rotor 42 may have a second diameter 40 smaller than first diameter 41. This results in a first radial gap 1a around impeller 2 that is smaller than a second radial gap 1b around drive magnetic rotor 42 (e.g., in the range of 0.065-0.150 mm, about 0.070-0.110 mm, or about 0.075 mm), which may be in the range of two to three times the first radial gap, as shown in FIG. 12B, an enlarged view of a portion of FIG. 12A. As shown in FIG. 12A, first diameter 41 may be located within distal impeller region 11, and second diameter 40 may be located within outlet region 6. For example, the impeller blades may have a maximum outer diameter that varies from a first diameter 41 in the distal impeller region 11 to a second diameter 40 at least partially in the outflow region 6, and / or the impeller blades may have a maximum outer diameter equal to the first diameter 41 in the distal impeller region 11, and the impeller 2 may include a magnetic coupling 42 having a maximum outer diameter equal to the second diameter 40 positioned at least partially in the outflow region 6.

[0085] Although the above description provides one or more example processes or apparatus, it will be understood that other processes or apparatus may be within the scope of the appended claims.

[0086] The specific embodiments described herein are not intended to limit the scope of any claim, which may encompass processes or apparatuses different from those described below, unless specifically indicated otherwise. The claims are not limited to apparatus or processes having all of the features of any one apparatus or process described below, or to features common to several or all of the apparatuses described below, unless specifically indicated otherwise. The apparatus or process described below may not be an embodiment of any exclusive rights granted by the issuance of this patent application. Subject matter described below to which no exclusive rights are granted by the issuance of this patent application may be the subject of other protection, such as, for example, pending patent applications, and the applicant, inventor, or owner does not intend to relinquish, abdicate, or dedicate such subject matter to the public by disclosure herein.

[0087] Various modifications to the implementations described in this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the spirit or scope of the present disclosure. Thus, the present disclosure is not intended to be limited to the implementations shown herein but is to be accorded the widest scope consistent with the claims, principles, and novel features disclosed herein. The term "exemplary embodiment" is used herein solely to mean "serving as an example, instance, or illustration." Any implementation described herein as an "exemplary embodiment" should not necessarily be construed as preferred or advantageous over other implementations, unless expressly stated otherwise.

[0088] Certain features that are described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation may also be implemented in multiple implementations separately or in any suitable subcombination. Furthermore, even if features are described above as acting in a particular combination and are initially claimed as such, one or more features from a claimed combination may, in some cases, be deleted from that combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0089] Similarly, although operations are illustrated in the figures in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown, or in any sequential order, or that all of the illustrated operations be performed, to achieve desirable results. Moreover, other implementations are within the scope of the following claims. In some cases, the operations recited in the claims may be performed in a different order and still achieve desirable results.

[0090] In general, those skilled in the art will understand that the terms used herein are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," "having" should be interpreted as "having at least," "includes" should be interpreted as "includes but not limited to," etc.). It will be further understood by those skilled in the art that where specific numbers of introduced claim recitations are intended, such intention will be explicitly stated in the claim, and in the absence of such statement, no such intention exists. For example, as an aid to understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce the claim recitations. However, the use of such phrases should not be construed as implying that introducing a claim recitation with the indefinite article "a" or "an" limits any particular claim containing such an introduced claim recitation to embodiments containing only one such recitation, even if the same claim also includes the introductory phrases "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should normally be interpreted to mean "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim recitations. Moreover, even if specific numbers in an introduced claim recitation are explicitly recited, those skilled in the art will recognize that such a recitation should typically be interpreted to mean at least the recited numbers (e.g., the mere recitation of "two recitations" without other modifiers normally means at least two recitations, or more than two recitations).Furthermore, when a convention similar to "at least one of A, B, and C, etc." is used, such an interpretation is generally intended in the sense that one of ordinary skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" includes, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together). When a convention similar to "at least one of A, B, or C, etc." is used, such an interpretation is generally intended in the sense that one of ordinary skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" includes, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together). It will be further understood by those skilled in the art that virtually any disjunction and / or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibility of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B," or "A and B."

Claims

1. 1. A mechanical circulatory assist device, comprising: a tubular cannula (4) including an inflow region (5), an outflow region (6), and a distal impeller region (11); an impeller (2) having a proximal end and a distal end, said impeller (2) being positioned within said tubular cannula (4) at least partially within said outlet region (6) and at least partially within said distal impeller region (11); a radial gap between the impeller (2) and the inner surface of the tubular cannula (4) varies in size between the proximal end and the distal end, and the size of the radial gap at a specific position between the proximal end and the distal end comprises a radial distance between a maximum impeller width and the inner surface of the tubular cannula (4) at the specific position; the impeller (2) comprises a distally tapered portion (21) tapering distally from a first diameter (13) to a distal diameter (20), the distal diameter (20) being smaller than the first diameter (13); The mechanical circulatory assist device, wherein the impeller (2) comprises a constant diameter portion (22) extending proximally from the distally tapered portion (21), the constant diameter portion (22) having the first diameter (13).

2. 2. The device of claim 1, wherein the constant diameter portion (22) extends at least partially within the distal impeller region (11) and at least partially within the outflow region (6).

3. 3. The device of claim 2, wherein the constant diameter portion (22) extends from the distally tapered portion (21) to the proximal end of the impeller (2).

4. The radial gap is between 0.095 mm and 0.125 mm at the distal diameter (20).

2. The device of claim 1, wherein the diameter is 1 / 2 mm.

5. The apparatus of claim 1, wherein the radial gap is between 0.060 mm and 0.090 mm at the first diameter (13).

6. The device of claim 1, wherein the distal diameter (20) is 0.040 mm to 0.100 mm smaller than the first diameter (13).

7. 7. The device according to claim 6, wherein said tapered portion (21) tapers in a linear slope.

8. The device of claim 1, wherein the distal diameter (20) is 0.06 mm to 0.08 mm smaller than the first diameter (13).

9. 9. The device according to claim 8, wherein said tapered portion (21) tapers in a linear slope.

10. 2. The device according to claim 1, wherein the slope of the tapered portion (21) is 0.

017.

11. 1. A mechanical circulatory assist device, comprising: a tubular cannula (4) including an inflow region (5), an outflow region (6), and a distal impeller region (11); an impeller (2) having a proximal end and a distal end, said impeller (2) being positioned within said tubular cannula (4) at least partially within said outlet region (6) and at least partially within said distal impeller region (11); a driving magnetic rotor (42) in which the impeller (2) is coupled to the driving magnetic rotor (42); a radial gap between the impeller (2) and the inner surface of the tubular cannula (4) varies in size between the proximal end and the distal end, and the size of the radial gap at a specific position between the proximal end and the distal end comprises a radial distance between a maximum impeller width and the inner surface of the tubular cannula (4) at the specific position; the impeller (2) comprises a distally tapered portion (21) tapering distally from a first diameter (13) to a distal diameter (20), the distal diameter (20) being smaller than the first diameter (13); The mechanical circulatory assist device, wherein the impeller (2) comprises a constant diameter portion (22) extending proximally from the distally tapered portion (21), the constant diameter portion (22) having the first diameter (13).

12. a bearing (43) configured to hold the distal end of the impeller (2) in the axial center of the tubular cannula (4); 12. The device of claim 11, wherein the bearing (43) comprises a plurality of spokes configured to connect the bearing (43) to the tubular cannula (4) and maintain the position of the bearing (43) relative to the tubular cannula (4).

13. 12. The apparatus of claim 11, wherein the driving magnetic rotor (42) is at least partially positioned in the outflow region (6).

14. 12. The device of claim 11, wherein the radial gap between the impeller (2) and the inner surface of the tubular cannula (4) is larger in the outlet region (6) than in the distal impeller region (11).

15. The apparatus of claim 11 , wherein the impeller comprises a constant diameter.

16. 1. A mechanical circulatory assist device, comprising: a tubular cannula (4) including an inflow region (5), an outflow region (6), and a distal impeller region (11); an impeller (2) positioned within the tubular cannula partially in the outflow region (6) and partially in the distal impeller region (11); a first radial gap (1a) between the impeller (2) and the distal impeller region (11) is smaller than a second radial gap (1b) between the impeller (2) and the outlet region (6) of the tubular cannula; the impeller (2) comprises a distally tapered portion (21) tapering distally from a first diameter (13) to a distal diameter (20), the distal diameter (20) being smaller than the first diameter (13); The mechanical circulatory assist device, wherein the impeller (2) comprises a constant diameter portion (22) extending proximally from the distally tapered portion (21), the constant diameter portion (22) having the first diameter (13).

17. 17. The device of claim 16, wherein the outflow area (6) comprises one or more struts (8).

18. 18. The device of claim 17, wherein the strut has a thickness greater than a thickness of the tubular cannula.

19. 17. Apparatus according to claim 16, wherein the first radial gap (1a) is in the range of 0.04 mm to 0.5 mm.

20. The device according to claim 16, wherein the second radial gap (1b) is in the range of 0.04 mm to 3 mm.

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