CATHETER PUMP
A catheter pump is provided that includes a rotatable impeller and an elongate cannula. The elongate cannula has a mesh that has a plurality of circumferential members disposed about the impeller. The elongate cannula has a plurality of axial connector extending between a proximal side of a distal circumferential member and a distal side of a proximal circumferential member. The circumferential members are radially self-expandable. The cannula is configured to minimize fracture within at least in the distal zone of the mesh as the elongated cannula moves into a sheathing device.
This application is a continuation of U.S. patent application Ser. No. 17/086,377, filed on Oct. 31, 2020, which is a continuation of U.S. patent application Ser. No. 16/110,648, filed Aug. 23, 2018, entitled Catheter Pump, which is a divisional of U.S. patent application Ser. No. 15/172,664, filed Jun. 3, 2016, entitled Catheter Pump, which is a divisional of U.S. patent application Ser. No. 13/801,528, filed Mar. 13, 2013, entitled Catheter Pump, which claims priority to U.S. Patent Application No. 61/667,903 filed Jul. 3, 2012, entitled Catheter Pump, all of which are hereby incorporated by reference in their entirety.
BACKGROUND OF THE INVENTION Field of the InventionThis application is directed to a catheter pump for mechanical circulatory support of a heart.
Description of the Related ArtHeart disease is a major health problem that has high mortality rate. After a heart attack, only a small number of patients can be treated with medicines or other non-invasive treatment. However, a significant number of patients can recover from a heart attack or cardiogenic shock if provided with mechanical circulatory support.
In a conventional approach, a blood pump having a fixed cross-section is surgically inserted between the left ventricle and the aortic arch to assist the pumping function of the heart. Other known applications involve providing for pumping venous blood from the right ventricle to the pulmonary artery for support of the right side of the heart. The object of the surgically inserted pump is to reduce the load on the heart muscle for a period of time, to stabilize the patient prior to heart transplant or for continuing support. Surgical insertion, however, can cause additional serious stresses in heart failure patients.
Percutaneous insertion of a left ventricular assist device (“LVAD”), a right ventricular assist device (“RVAD”) or in some cases a system for both sides of the heart (sometimes called biVAD) therefore is desired. Conventional fixed cross-section ventricular assist devices designed to provide near full heart flow rate are too large to be advanced percutaneously, e.g., through the femoral artery.
There is a continuing need for improved cannula that provide sufficient expansion force and a stable expanded shape while still allowing for reliable and easy collapse to a delivery size. In other words, the cannula should have sufficient force to expand, but also be collapsible under significant sheathing force while avoiding a risk of damaging the cannula during re-sheathing. There is a continuing need for improved cannula that can be expanded and collapsed, in some cases over many cycles, without risking breakage of the struts and connectors forming the mesh. Broken struts pose a risk of complicating patient treatment and/or compromising the performance of the device.
SUMMARY OF THE INVENTIONThere is an urgent need for a pumping device that can be inserted percutaneously and also provide full cardiac rate flows of the left, right, or both the left and right sides of the heart when called for.
In one embodiment, an apparatus is provided for inducing motion of a fluid relative to the apparatus. The apparatus can be a catheter pump, as discussed below. The apparatus can include a rotatable impeller and an elongate cannula. The cannula has a plurality of circumferential members and a plurality of circumferential connectors. The circumferential members are disposed about a space, e.g., a volume including at least the impeller zone. One or more of, e.g., each of, the circumferential members can have an undulating configuration including a plurality of apices connected by elongate struts. The circumferential connectors can be disposed between alternating struts of adjacent circumferential members. A plurality of axial connectors is disposed between a proximal side of a proximal apex and a distal side of an adjacent circumferential member in the impeller zone of cannula.
In some embodiments, the cannnula is differentiated along its length to have varying stiffness. The elongate cannula has an impeller zone disposed about the impeller and a distal zone disposed distal of the impeller zone. The distal zone can be made more flexible by reducing the number of connectors disposed therein. For example, the impeller zone can have alternating elongate struts that are connected by circumferential connectors and the distal zone can have alternating elongate struts that are free of such connections.
In one variation, each of the connectors of the plurality has a distal end coupled with a proximal side of a proximal apex of a first circumferential member, a proximal end coupled with a distal face of a second circumferential member disposed adjacent to and proximal of the first circumferential member. Each of the connectors has an arcuate section disposed between the proximal and distal ends. In this variation, the arcuate section comprises a single convex portion disposed between the proximal and distal ends.
A first plurality of axial connectors is disposed between a proximal side of a proximal apex and a distal side of an adjacent circumferential member in the impeller zone of the cannula. A second plurality of axial connectors is disposed between a proximal side of a proximal apex and a distal side of an adjacent circumferential member in the distal zone of the cannula.
In another embodiment, an apparatus for pumping blood includes a rotatable impeller, an elongate cannula, and a sheath configured to be positioned over the elongate cannula. The elongate cannula has a plurality of circumferential members disposed about the impeller. One or more of, e.g., each of, the circumferential members can have an undulating configuration. The undulating configuration can include a plurality of proximal and distal apices, with proximal apices connected to distal apices by an elongate strut. The sheath is configured to be positioned over the elongate cannula to actuate the cannula from an expanded configuration to a collapsed configuration. The elongate cannula is configured to deflect radially inwardly in an area around the proximal apices before the apices move into the sheath.
In some configurations, the elongate cannula has an impeller zone disposed about the impeller and a distal zone disposed distal of the impeller zone. For example, the impeller can extend in about one-half or less of the length of the cannula. The distal zone may be more easily compressed by the sheath because the impeller is not present in that area. As a result, the cannula can have a different configuration in the distal zone.
In another configuration, a catheter pump is provided. A catheter pump is an example of an apparatus for inducing motion of a fluid relative to the apparatus. The catheter pump includes a rotatable impeller and an elongate cannula having a mesh comprising a plurality of circumferential members disposed about the impeller. The mesh also has a plurality of axial connectors extending between a proximal side of a distal circumferential member and a distal side of a proximal circumferential member. The circumferential members are radially self-expandable. A sheath is configured to be positioned over the elongated cannula to actuate the cannula from an expanded configuration to a collapsed configuration. The cannula is configured to minimize a risk of fracture within the mesh, e.g., of the axial connectors, as the elongated cannula moves into the sheath.
In a further embodiment, an apparatus for inducing motion of a fluid relative to the apparatus is provided. The apparatus includes a a rotatable impeller and an elongate cannula. The elongate cannula is defines a blood flow channel in which the impeller is disposed. The cannula has an expandable structure comprising that has a plurality of circumferential members, a plurality of circumferential connectors, and a plurality of axial connectors. The circumferential members are disposed about the blood flow channel. The circumferential members have an undulating configuration including a plurality of apices connected by elongate struts. The circumferential connectors are disposed between alternating struts of adjacent circumferential members. The axial connectors have a distal end coupled with a proximal side of a proximal apex of a first circumferential member, a proximal end coupled with a distal face (e.g., an edge) of a second circumferential member disposed adjacent to and proximal of the first circumferential member. The axial connectors have an arcuate section disposed between the proximal and distal ends. The arcuate section comprises a single convex portion disposed between the proximal and distal ends.
In another embodiment, an apparatus for pumping blood is provided that includes a rotatable impeller, an elongate cannula, and an axial member. The elongate cannula has a plurality of circumferential members disposed about the impeller. One or more of the circumferential members has an undulating configuration including a plurality of proximal and distal apices. Each proximal apex is connected to a distal apex by an elongate strut. The axial member has a distal end coupled with a proximal apex of a first circumferential member a proximal end coupled with a second circumferential member disposed proximal of the first circumferential member. The axial member has a length that is less than the distance between the proximal apex to which the distal end of the axial member is connected and a proximal apex of the second circumferential member that is axially aligned with the proximal apex to which the distal end of the axial member is connected.
In another embodiment, a catheter pump is provided that includes a rotatable impeller and an elongate cannula. The elongate cannula has a mesh that has a plurality of circumferential members disposed about the impeller. The elongate cannula has a plurality of axial connector extending between a proximal side of a distal circumferential member and a distal side of a proximal circumferential member. The circumferential members are radially self-expandable. The cannula is configured to minimize fracture within at least in the distal zone of the mesh as the elongated cannula moves into a sheathing device.
In another embodiment, a cannula for conveying blood is provided that includes an in-situ expandable and collapsible mesh structure and a polymeric enclosure. The in-situ expandable and collapsible mesh structure has a plurality of undulating circumferential members surrounding a lumen. Each circumferential member has proximal and distal vertices. The polymeric enclosure is disposed about the mesh structure to enclose the lumen along a length between an inlet and an outlet. The number of proximal vertices in an area defined between a proximal circumference intersecting the proximal vertex of a circumferential member and a distal circumference intersecting the distal vertex of the same circumferential member adjacent to the proximal vertex is at least two.
A more complete appreciation of the subject matter of this application and the various advantages thereof can be realized by reference to the following detailed description, in which reference is made to the accompanying drawings in which:
More detailed descriptions of various embodiments of components for heart pumps useful to treat patients experiencing cardiac stress, including acute heart failure, are set forth below.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTThis application is directed to apparatuses for inducing motion of a fluid relative to the apparatus. The apparatus can be a catheter pump, e.g., a percutaneous heart pump.
Embodiments of the catheter pumps of this application can be configured with expandable structures to enhance performance. For example, an impeller for moving blood axially can be provided. The impeller can be positioned in an expandable cannula. When so positioned, the expandable cannula provides dual function of enclosing a blood flow lumen through which the impeller can act and also housing the impeller. In that sense, the cannula is also an expandable housing. The expandable cannula and impeller provide a flow rate in the pump that is much larger than would be possible using percutaneous access techniques were these components not capable of expanding. However, it may be possible to reduce flow resistance by increasing the size of a blood-flow cannula even with a fixed diameter impeller. Also, it may be possible to sequentially collapse the impeller, e.g., by withdrawing the impeller into a rigid ring or tubular segment prior to collapsing the impeller. These variant also benefit from many of the embodiments herein and are within the scope of this application even though the impeller may not be housed in the cannula at all times or at all.
While these configurations provide excellent flow rates, a challenge arises in collapsing the expanded structures prior to removal from the patient. The collapsing of the impeller assembly 92 is this manner is not straight-forward. In various embodiments, a mesh is used to support the expandable portion of a blood flow conduit in the impeller assembly 92. The expandable portion can include a self-expanding structure that expands when undulating generally ring-shaped members release stored strain energy arising from circumferential compression. Compression of such a structure involves transforming axial relative movement of the sheath assembly 88 over the catheter body 84 into a circumferential compression force. There is a chance that such movement will cause the distal end to become lodged between adjacent undulating members. Such problems with compression can be more likely to occur when the undulating members are spaced apart by an axial distance that is greater than the wall thickness of the distal end of the sheath assembly 88. While the undulating members could be moved much closer together, such an approach could make the expandable structure too stiff thereby inhibiting collapse of the expandable portion. Some embodiments herein are configured to reduce this risk, while retaining sufficient flexibility. Some embodiments are configured to prevent connectors between adjacent rings from being deformed around the distal end of the sheath assembly 88. Various aspects of the expandable cannula and/or mesh in accordance with the invention achieve a careful balance of expansion force, collapsing force, and structural strength.
Additional details of the structures disclosed in these figures, and various modified embodiments thereof, and method related to the same are discussed in U.S. application Ser. No. 13/343,617, filed Jan. 4, 2012, which is hereby incorporated by reference herein in its entirety. In addition, this application incorporates by reference in its entirety and for all purposes the subject matter disclosed in each of the following concurrently filed applications: application Ser. No. 13/802,556, which corresponds to attorney docket no. THOR.072A, entitled “DISTAL BEARING SUPPORT,” filed on the same date as this application; Application No. 61/780,656, which corresponds to attorney docket no. THOR.084PR2, entitled “FLUID HANDLING SYSTEM,” filed on the same date as this application; application Ser. No. 13/801,833, which corresponds to attorney docket no. THOR.089A, entitled “SHEATH SYSTEM FOR CATHETER PUMP,” filed on the same date as this application; application Ser. No. 13/802,570, which corresponds same date as this application; and application Ser. No. 13/802,468, which corresponds to attorney docket no. THOR.093A, entitled “MOTOR ASSEMBLY FOR CATHETER PUMP,” filed on the same date as this application.
The wall pattern 200 illustrates a plurality of circumferential members 224 and a plurality of circumferential connectors 228. In the flat view of
In various embodiments, the polymer material is a coating disposed about the cannula mesh structure 204. Suitable materials for the polymer coating include, but are not limited to a biocompatible polymer, a drug-eluting polymer, and a functionalized polymer such as a thromboresistant material. In various embodiments, the polymer material is Hapflex™ or Thoralon™. In the exemplary structure, the polymer material fills the voids in the mesh structure. The polymer material also coats the inner and outer walls such that the mesh structure does not come into contact with blood and tissue. In various embodiments, the polymer material is a thin coating. In various embodiments, the polymer coating has a maximum thickness of less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron. In various embodiments, the polymer coating is formed of a plurality of layers. In various embodiments, the polymer coating is configured to reinforce the mesh structure. The polymer material may be applied by dip coating, molding, spinning on a mandrel, or other techniques. One will appreciate from the description herein that the polymer coating may be configured and applied in various other manners. Further details of suitable materials are set forth in U.S. Pat. Nos. 4,675,361 and 6,939,377, which are incorporated by reference herein in their entireties and for all purposes.
The circumferential members 224 preferably are configured to be self-expandable, also described as self-expanding herein.
The circumferential connectors 228 can be disposed between alternating struts 236 of adjacent circumferential members 224 in at least one of the distal and impeller zones 208, 212. For example, the connectors 228 (or other connectors discussed herein) can join a node on one circumferential member to a node on an adjacent circumferential member. In the case of the connectors 228, the nodes are offset from the peaks and valleys. At least one of the nodes can be disposed on a strut that extends between adjacent nodes. In some cases, connectors are disposed between the crests and trough and can be disposed between a crest the a transverse mid-point of a sinusoidal circumferential member. In some patterns, the width of nodes are greater in the impeller zone than distal thereof.
In various embodiments, there can be different groups of circumferential connectors 228. For example, in
In one embodiment, substantially all of the impeller zone 212 has enhanced rigidity connectors 252A.
Enhanced concentration of material (e.g., increased struts per unit area) makes the connection between the apices 232B and adjacent proximal circumferential member 224 more robust. In particular, larger forces are encountered in the impeller zone 212 during collapsing of, sometimes referred to as re-sheathing of, the cannula, e.g., after the catheter pump has been used.
The distal zone 208 is substantially free of the helical zones 260 or other concentration of material in the embodiment of
Also, the distal zone 208 can be made less susceptible to fracture by providing circumferential connectors 228 in some embodiments. In the illustrated embodiment, every other elongate struts 236 of a circumferential member 224 in the distal zone 208 is connected to an adjacent elongate struts 236.
One technique for minimizing fracture risk in the distal zone 408 is to configure the mesh structure 404 to produce helical zones 460 throughout the structure, including in the distal zone 408 where there area no circumferential connectors. This can be achieved by heat setting the expanded shape in a material that would operate in an elastic range in this application. For example, nitinol can be configured to be compressed for delivery and heat set to expand to the shape seen in
The pattern arrangements in
Another approach to easing re-sheathing involves reducing an amount of open area in the formed cannula wall pattern around relative stiff proximally oriented structures. For example, the axially oriented undulating connectors in
As shown in
In addition to the connectors 470, 470A, the pattern 462 includes connectors 476 disposed between proximal oriented apices (or valleys, if the pattern is held distal end up) and distal edge of a circumferential member disposed proximally of the apex. The connectors 476 are relatively slender in order to permit the apices to which they are connected to flex upon expansion and collapse of the cannula into which the wall pattern 462 is incorporated. The proximal portion 462A also provides enhanced concentration of material around the connectors 476 to minimize a chance of fracturing these connectors upon expansion and collapse of the cannula.
Other methods can be used to provide some of these benefits, include making the axial length of the rings shorter and increasing the number of sinusoidal waves within a ring. These features will result in other changes to the cannula pattern. Shorter rings tend to increase the strain the material must undergo in changing from the collapsed to expanded state. Suitable materials, such as nitinol, may be more prone to permanent deformation or fracture with increasing strain. Increasing the number of sinusoidal waves within a ring increases the diameter of the collapsed cannula, if other relevant factors (such as strut width) remains the same, may reduce the stress and strain to which the struts are subjected.
Other cannula patterns can be provided to reduce unsupported film area without increasing the number of embedded rings. For example, an arm feature could be added between two struts of adjacent rings. As the cannula transforms from the collapsed to expanded form, the arm orientation moves from a more axial to more radial orientation (in some cases, forming an “A” shape). More details of these structures are set forth in connection with
In a transition zone between the proximal portion 462A and the central portion 462B, modified connectors 470A are provided that are much shorter in a direction parallel to the longitudinal axis of the struts 474 than are the connectors 470. The shorter connectors 470A make the central portion 462B much more flexible than the proximal portion 462A. Such flexibility can provide less irritation to heart tissue and than higher biocompatibility as discussed elsewhere herein.
A proximal end of each of the connectors 476 is coupled to a portion of the strut 474 that is also connected to the connector 470 or 470A. This structure provides a concentration of material around the more flexible and elongate connector 476 to minimize the chance of fracture of this structure when the cannula is collapsed by a sheath, as discussed herein. Because the sheathing forces are less in the distal portion of the cannula corresponding to the distal portion 462C, the concentration of material in the distal portion 462C around the connectors 476 can be less than in the proximal portion 462A.
Various additional advantageous features are found on the proximal and distal portions 462A, 472C in various embodiments. For example, when the pattern 462 is formed a sheet-like zone 480 is provided that is advantageous for mechanically integrating the pattern 462 into various catheter bodies in an assembly. A plurality of cantilevered projections 482 is disposed in the sheet-like zone 480 and is disposed about the circumference of the proximal portion 462A when the pattern 462 is formed into a tubular body. The projections 482 can be deflected into mating recesses in the catheter body 84 or another structure of a catheter assembly to provide a resistance to detachment of the pattern 462 (and the cannula into which it is incorporated) from the catheter body or assembly. Such resistance advantageously minimizes inadvertent separation of the cannula from the catheter body 84 during re-sheathing.
Also, the peak-to-peak distance between the proximal-most circumferential member 466 and the circumferential member immediately distal thereof is greater than the average peak-to-peak distance of adjacent circumferential members distal thereof. A consequence of this is that the connector 470 between the proximal-most circumferential member and the adjacent circumferential member is located closer to the peaks of the proximal most circumferential member. This creates an enlarged space 488 that aids in transitioning the diameter of the expanded cannula into which the pattern 462 is incorporated from a larger size disposed about the impeller to the diameter of the sheet-like zone 480 when formed into a tubular body.
The distal portion 462C of the wall pattern includes elongate members 490 that are for mechanically integrating the pattern into a catheter assembly. The elongate members 490 extend from distal apices of the distal portion 462C of the pattern 462. The connectors 470A and 476 disposed between the distal-most circumferential member 466 are shifted closer to the peak of the adjacent circumferential member 466 such that a larger space 492 is provided between the distal-most two circumferential members 466. The shifting of these connectors provides a larger peak-to-peak distance between the distal-most two circumferential members 466 than is provided between other circumferential members of the pattern 462. By increasing this distance, the transition from the enlarged diameter of the expanded cannula into which the pattern is incorporated to the smaller diameter of distally located non-expandable components of a catheter assembly can be facilitated.
In one embodiment, the connector 530 is connected approximately in the middle of adjacent struts, e.g., half way between adjacent peaks and valleys on each circumferential member. This arrangement roughly reduced by 50 percent the unsupported area between these struts. Long slender struts may be more prone to shearing upon being collapsed into the sheath. Accordingly, it may be desirable to locate the struts 530 in areas of local minima of a sheathing force curve as discussed below in connection with
The foregoing features of mesh patterns can be combined with other features for improving tip gap control. Such features can be incorporated into a distal bearing, as discussed in concurrently filed Application Ser. No. 13/802,556, which corresponds to attorney docket no. THOR.072A, entitled “DISTAL BEARING SUPPORT,” filed on the same date as this application; and/or in impeller or impeller blade construction, as discussed in application Ser. No. 13/802,570, which corresponds to attorney docket no. THOR.090A, entitled “IMPELLER FOR CATHETER PUMP,” filed on the same date as this application. Both of these applications are incorporated by reference herein in their entirety.
Although the inventions herein have been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present inventions. It is therefore to be understood that numerous modifications can be made to the illustrative embodiments and that other arrangements can be devised without departing from the spirit and scope of the present inventions as defined by the appended claims. Thus, it is intended that the present application cover the modifications and variations of these embodiments and their equivalents.
Claims
1. A catheter pump assembly, comprising:
- an elongate body having a distal end and a proximal end opposite the distal end;
- an expandable cannula coupled with the distal end of the elongate body, the expandable cannula comprising: a mesh structure that includes a plurality of nitinol members defining a cannula distal portion and a cannula proximal portion, the cannula proximal portion tapering from an expanded diameter to a smaller diameter at the distal end of the elongate body and coupled to the distal end of the elongate body, the cannula distal portion defining a plurality of inlet spaces between the plurality of nitinol members to permit blood to enter the expandable cannula; and a coating formed over the mesh structure and forming a conduit for the flow of blood from the cannula distal portion to the cannula proximal portion; and
- an impeller coupled with the distal end of the elongate body, the impeller configured to rotate to induce blood flow through the expandable cannula.
2. The catheter pump assembly of claim 1, wherein the expanded diameter is at least 5 millimeters.
3. The catheter pump assembly of claim 1, wherein the cannula proximal portion tapers at an angle in the range of 30 degrees to 40 degrees relative to the longitudinal axis of the elongate body.
4. The catheter pump assembly of claim 1, wherein the expandable cannula is configured to collapse to a delivery configuration having a delivery diameter for insertion into a patient, and expand to the expanded diameter for operation.
5. The catheter pump assembly of claim 1, wherein the coating comprises a biocompatible polymer.
6. The catheter pump assembly of claim 1, wherein the plurality of nitinol members forms connection structures for securing the mesh structure to the elongate body.
7. The catheter pump assembly of claim 6, wherein the connection structures secure the mesh structure to the elongate body at a hub structure.
8. The catheter pump assembly of claim 7, wherein the connection structures engage slots formed in the hub structure.
9. The catheter pump assembly of claim 6, wherein the connection structures comprise loop elements.
10. The catheter pump assembly of claim 6, wherein the connection structures comprise linear elements.
11. A cannula comprising:
- a self-expandable mesh structure having a proximal portion and a distal portion, the mesh structure comprising: a plurality of struts, each strut of the plurality of struts disposed adjacent at least one other strut and spaced apart axially from the least one other adjacent strut, the plurality of struts extending at least partway between the proximal portion of the mesh structure and the distal portion of the mesh structure, the proximal portion tapering from an expanded diameter to a smaller diameter and configured to be coupled to a distal end of a catheter body, the distal portion defining a plurality of inlet spaces between the plurality of struts to permit blood to enter the self-expandable mesh structure; and a polymeric enclosure disposed about at least a portion of the mesh structure to define a lumen along a length of the mesh structure from the proximal portion to the distal portion.
12. The cannula of claim 11, wherein the expanded diameter is at least 5 millimeters.
13. The cannula of claim 11, wherein the cannula proximal portion tapers at an angle in the range of 30 degrees to 40 degrees relative to the longitudinal axis of the elongate body.
14. The cannula of claim 11, wherein the expandable cannula is configured to collapse to a delivery configuration having a delivery diameter for insertion into a patient, and expand to the expanded diameter for operation.
15. The cannula of claim 11, wherein the coating comprises a biocompatible polymer.
16. The cannula of claim 11, wherein the plurality of nitinol members forms connection structures for securing the mesh structure to the elongate body.
17. The cannula of claim 16, wherein the connection structures secure the mesh structure to the elongate body at a hub structure.
18. The cannula of claim 17, wherein the connection structures engage slots formed in the hub structure.
19. The cannula of claim 16, wherein the connection structures comprise loop elements.
20. The cannula of claim 16, wherein the connection structures comprise linear elements.
Type: Application
Filed: Nov 10, 2022
Publication Date: Mar 9, 2023
Inventors: Keif M. Fitzgerald (San Jose, CA), Richard L. Keenan (Livermore, CA), William J. Harrison (Signal Mountain, TN)
Application Number: 18/054,482