Flexible catheters and methods of forming same

A delivery device for a collapsible prosthetic heart valve includes an inner shaft having a proximal end and a distal end, an outer shaft disposed around the inner shaft and longitudinally moveable relative to the inner shaft, and a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, the compartment being adapted to receive the prosthetic heart valve. At least one of the outer shaft or the distal sheath may have a pattern of cutouts formed therein, the pattern including at least one ring around a circumference of the at least one of the outer shaft or the distal sheath, the at least one ring having at least one of the cutouts.

BACKGROUND OF THE INVENTION

The present disclosure relates to delivery devices for implanting medical devices such as prosthetic heart valves and, more particularly, to assemblies and methods for forming delivery devices having greater flexibility.

Prosthetic heart valves may be formed from biological materials such as harvested bovine valves or pericardial tissue. Such valves may include a valve assembly including one or more leaflets and a cuff or skirt, and are typically fitted within a stent, which may be inserted into the heart at the annulus of the compromised native valve to replace the native valve. To perform such an insertion procedure using a minimally invasive technique, it is typically necessary to compress the stent to a reduced diameter for loading into the delivery device.

The delivery device having the prosthetic heart valve loaded therein is advanced through the patient's vasculature until it reaches the implantation site. Due to the size of the arteries and the tortuosity of the delivery route, it may be difficult to maneuver the delivery system to the implantation site. It would therefore be beneficial to provide a delivery device having a greater degree of flexibility that can more readily navigate tortuous paths.

BRIEF SUMMARY OF THE DISCLOSURE

In some embodiments, a delivery device for a collapsible prosthetic heart valve includes an inner shaft having a proximal end and a distal end, an outer shaft disposed around the inner shaft and longitudinally moveable relative to the inner shaft, and a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, the compartment being adapted to receive the prosthetic heart valve. At least one of the outer shaft or the distal sheath may have a pattern of cutouts formed therein, the pattern including at least one ring around a circumference of the at least one of the outer shaft or the distal sheath, the at least one ring having at least one of the cutouts.

In some embodiments, a delivery device for a collapsible prosthetic heart valve includes an inner shaft having a proximal end and a distal end, an outer shaft disposed around the inner shaft and longitudinally moveable relative to the inner shaft, and a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, the compartment being adapted to receive the prosthetic heart valve. At least one of the outer shaft or the distal sheath may have a pattern of cutouts formed therein, the pattern including a plurality of polygonal cells extending through the at least one of the outer shaft or the distal sheath.

In some embodiments, a method of forming a delivery device for a collapsible prosthetic heart valve includes providing an inner shaft having a proximal end and a distal end, an outer shaft disposed about the inner shaft and being longitudinally moveable relative to the inner shaft, and a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, the compartment being adapted to receive the prosthetic heart valve, and cutting a pattern on at least one of the outer shaft or the distal sheath at different axial extents.

DETAILED DESCRIPTION

Embodiments of the presently disclosed delivery devices are described herein in detail with reference to the drawing figures, wherein like reference numerals identify similar or identical elements. In the description which follows, the term “proximal” refers to the end of a delivery device, or portion thereof, which is closest to the operator in use, while the term “distal” refers to the end of the delivery device, or portion thereof, which is farthest from the operator in use. Also as used herein, the terms “about,” “generally” and “approximately” are intended to mean that slight deviations from absolute are included within the scope of the term so modified.

Referring now toFIGS. 1A-1Bto illustrate the structure and function of the present invention, an exemplary transfemoral delivery device10for a collapsible prosthetic heart valve (or other types of self-expanding collapsible stents) has a catheter assembly16for delivering the heart valve to and deploying the heart valve at a target location, and an operating handle20for controlling deployment of the valve from the catheter assembly. Delivery device10extends from proximal end12(FIG. 1B) to atraumatic tip14at the distal end of catheter assembly16. Catheter assembly16is adapted to receive a collapsible prosthetic heart valve (not shown) in compartment23defined around inner shaft26and covered by distal sheath24.

Inner shaft26may extend from operating handle20to atraumatic tip14of the delivery device, and includes retainer25affixed thereto at a spaced distance from tip14and adapted to hold a collapsible prosthetic valve in compartment23. Retainer25may have recesses80therein that are adapted to hold corresponding retention members of the valve. Details of the heart valve will be described in greater detail below with reference toFIG. 2. Inner shaft26may be made of a flexible material such as braided polyimide or polyetheretherketone (PEEK), for example. Using a material such as PEEK may improve the resistance of inner shaft26to kinking while catheter assembly16is tracking through the vasculature of a patient.

Distal sheath24surrounds inner shaft26and is slidable relative to the inner shaft such that it can selectively cover or uncover compartment23. Distal sheath24is affixed at its proximal end to outer shaft22, the proximal end of which is connected to operating handle20. Distal end27of distal sheath24abuts atraumatic tip14when the distal sheath is fully covering compartment23, and is spaced apart from the atraumatic tip when compartment23is at least partially uncovered.

Operating handle20is adapted to control deployment of a prosthetic valve located in compartment23by permitting a user to selectively slide outer shaft22proximally or distally relative to inner shaft26, thereby respectively uncovering or covering the compartment with distal sheath24. In some examples, operating handle20is configured to repeatedly cover or uncover the compartment with distal sheath24. For example, compartment23may be uncovered to expose a valve and allow it to expand at a target location. Once at the location, the functionality and positioning of the valve may be examined prior to complete release of the valve. If the functioning or position of the valve is improper, distal sheath24may be advanced to cover the compartment and the valve may be redeployed in a different position or orientation.

Typically, outer shaft22may be made of a flexible material such as nylon 11 or nylon 12, and it may have a round braid construction (i.e., round cross-section fibers braided together) or flat braid construction (i.e., rectangular cross-section fibers braided together), for example. The proximal end of inner shaft26may be connected in substantially fixed relationship to outer housing30of operating handle20, and the proximal end of outer shaft22may be affixed to carriage assembly40that is slidable along a longitudinal axis of the handle housing, such that a user can selectively slide the outer shaft relative to the inner shaft by sliding the carriage assembly relative to the handle housing. A hemostasis valve28may be provided and may include an internal gasket adapted to create a seal between inner shaft26and the proximal end of outer shaft22.

Handle housing30includes a top portion30aand a bottom portion30b. The top and bottom portions30aand30bmay be individual pieces joined to one another as shown inFIG. 1B. Collectively, top and bottom portions30aand30bdefine elongated space34in housing30in which carriage assembly40may travel. Elongated space34preferably permits carriage assembly40to travel a distance that is at least as long as the anticipated length of the prosthetic valve to be delivered (e.g., at least about 50 mm), such that distal sheath24can be fully retracted from around the prosthetic valve. Carriage assembly40may further include a pair of carriage grips42each attached to body portion41by a respective carriage grip shaft (not shown).

Handle housing30further defines a pocket37that extends through the top portion30aand bottom portion30bfor receiving a deployment actuator21. Deployment actuator21is internally threaded for selective engagement with a threaded rod45. When the deployment actuator21is in threaded engagement with the threaded rod, rotation of the deployment actuator in one direction (either clockwise or counterclockwise depending on the orientation of the threads on the threaded rod) causes the threaded rod to move proximally, at the same time pulling the body portion41of carriage assembly40proximally through elongated space34, and pulling outer shaft22and distal sheath24proximally relative to inner shaft26. Similarly, when deployment actuator21is in threaded engagement with the threaded rod, rotation of the deployment actuator in the opposite direction causes the threaded rod to move distally, at the same time pushing body portion41of carriage assembly40distally through elongated space34, and pushing outer shaft22and distal sheath24distally relative to inner shaft26.

FIG. 2shows a bioprosthetic valve100such as that described in U.S. Patent Publication No. 2012/0053681, the contents of which are hereby incorporated herein by reference. Prosthetic valve100is designed to replace a native aortic valve. Valve100has a collapsed condition and an expanded condition and may be formed from a collapsible framework or stent102, with valve assembly104internally connected to the stent. Stent102may be formed from any suitable biocompatible material, such as nitinol or any other suitable elastic or shape memory material, and may include annulus section106, aortic section108, and sinus section110located between the annulus section and the aortic section. Aortic section108may have a larger cross-section than annulus section106. Valve assembly104includes a plurality of leaflets112and cuff114attached to stent102. Leaflets112and cuff114may be formed from a biocompatible polymer, from natural tissue such as bovine or porcine pericardial tissue, or from other appropriate biocompatible materials. Valve assembly104is preferably connected to stent102generally within annulus section106. A plurality of tabs or retainers118may be spaced around one or both ends of stent102for engagement with recesses80of retainer25, described above. Retainers118may also be utilized to collapse valve100for loading into delivery device10.

Valve100is preferably stored in its expanded or open condition as bioprosthetic valve assembly104may be compromised by storage in a collapsed condition for extended periods of time. As such, it is necessary to crimp valve100into a collapsed condition of reduced cross-section for loading into delivery device10just prior to the surgical implantation procedure. In order to effectively limit the time period valve100is collapsed, the crimping process is preferably conducted in the operating arena by the surgeon, interventional cardiologist or surgical assistant using a specialized assembly.

FIG. 3is a schematic representation of a human heart300. The human heart includes two atria and two ventricles: a right atrium312and a left atrium322, and a right ventricle314and a left ventricle324. As illustrated inFIG. 3, heart300further includes an aorta310, and an aortic arch320. Disposed between left ventricle324and aorta310is aortic valve330. During ventricular systole, pressure rises in left ventricle324. When the pressure in the left ventricle rises above the pressure in aorta310, aortic valve330opens, allowing blood to exit left ventricle324into the aorta310. When ventricular systole ends, pressure in left ventricle324rapidly drops. When the pressure in left ventricle324decreases, the aortic pressure forces aortic valve330to close. Blood flows through heart300in the direction shown by arrows “B”.

A dashed arrow, labeled “TF”, indicates a transfemoral approach for treating or replacing heart tissue using a delivery device, such as that shown inFIGS. 1A-C. In transfemoral delivery of an aortic valve, an incision is made adjacent the hip and threaded up the femoral artery and around the aortic arch as shown. A dashed arrow, labeled “TA”, indicates a transapical approach for treating or replacing heart tissue. In transapical delivery, a small incision is made between the ribs and into the apex of the left ventricle324at position “P1” in heart wall350to deliver the prosthetic heart valve to the target site. In order to more easily advance a catheter to a target site using either of these approaches, or any other approach, a catheter with greater flexibility than conventional catheters may preferably be employed.

In order to increase the flexibility of the delivery system, an outer shaft of a delivery device may be laser cut in a repeating pattern. As shown inFIG. 4A, outer shaft410is formed of a generally cylindrical hypotube having proximal end412and distal end414. Outer shaft410may be formed of a metal, such as nitinol, Elgiloy, or stainless steel, or a biocompatible polymer. Outer shaft410may have a size of approximately 24 French or less with outer wall416defining lumen418extending therethrough from proximal end412to distal end414.

Portions of outer wall416may be removed to form cutouts420, for example, by laser cutting. As shown in the enlargement ofFIG. 4B, multiple cutouts420may be made to form a repeating pattern419. For example, three cutouts420a,420b,420cmay be formed in outer wall416about the circumference of outer shaft410, each cutout being spaced from adjacent cutouts by a distance s1to form a discontinuous ring421about the circumference at a given longitudinal extent (FIG. 4C). As used herein, the term “ring” is used to describe any number of cutouts aligned with one another about the circumference of a body, and is not limited to a single cutout that forms a complete circle about the circumference of the body. The number of cutouts420per ring421may vary as desired and may include as few as one or two cutouts420or as many as four, five, six or more cutouts420.

Multiple rings421may be formed along the length of outer shaft410. In the example shown, rings421are divided into two sets, a first set of rings421aand a second set of rings421b. Rings of the first set of rings421amay all be aligned with one another along the length of outer shaft410as shown, and rings of the second set of rings421bmay be offset from the first set of rings421aby a predetermined radial angle (e.g., offset by 90 degrees). Successive rings may be chosen such that the rings alternate between the two sets as shown. Though two sets are shown, it will be understood that the rings may be formed in any number of sets, for example, three, four or five sets, that are circumferentially offset from one another.

Turning now toFIG. 4D, the details of cutouts420will be more fully described. As shown, each cutout420includes an elongated portion422and a pair of teardrop portions424on opposing ends of the elongated portion422. The combined length of the cutouts420around each ring may make up between about 50% and about 90% of the circumference of outer shaft410. In this example, cutouts420are disposed perpendicular to the longitudinal axis of outer shaft410. Teardrop portions424may provide added flexion for outer shaft410, while providing strain relief and maintain adequate compression resistance of outer shaft410. In some examples, each cutout420includes a teardrop portion424at only one end of elongated portion422. In other examples, cutouts420may include portions of other shapes such as triangles, circles, semicircles, or the like at one or both ends of elongated portion422, instead of teardrop portions424.

Variations of the embodiment ofFIGS. 4A-4Dare possible depending on the length and/or diameter of the outer shaft, the materials chosen for forming the shaft and other considerations. For example, cutouts420may include a combination of shapes discussed above. The number of rings421cut into outer shaft410may also be varied. In some examples, outer shaft410includes between about 40 and about rings421. Additionally, the axial distance between adjacent rings421may be between about 0.3 mm and about 1 mm. Rings421may be spaced from one another evenly or unevenly in the axial direction. Each ring421may also include the same or a different number of cutouts420. For example, a first ring may include only two cutouts, while an adjacent ring includes three cutouts.

Either the same, a similar or a different pattern of rings may also be laser cut into the distal sheath of a delivery device. Thus, the distal sheath and/or outer shaft may be laser cut as shown to increase the flexibility of the delivery device over current devices of a similar size, while maintaining comparable compression resistance needed for resheathability. Thus, by providing a continuous wall of an outer shaft from one end to the other, the wall having a plurality of cutouts, comparable compression strength is maintained while flexibility is increased.

FIGS. 5A and 5Billustrate an embodiment of a distal sheath of a delivery device having improved flexibility over conventional distal sheaths. In this example, a pattern519is cut into distal sheath511of a delivery device. It will be understood that the same or similar pattern may also be formed in the outer shaft of the delivery device or in both the distal sheath and the outer shaft. Distal sheath511is formed of a generally cylindrical hypotube having proximal end512and distal end514. Distal sheath511may be formed of a metal, such as nitinol, Elgiloy, or stainless steel, or a biocompatible polymer. Distal sheath511may have a size of approximately 24 French or less and may include outer wall516defining lumen518extending therethrough from proximal end512to distal end514.

Instead of forming elongated cutouts420, polygonal cutouts, hereinafter referred to as cells520, may be cut in outer wall516of distal sheath511to form pattern519having a stent-like structure (FIG. 5B). In forming cells520, struts521remain about each cell520, the struts being flexible and aiding in the maneuverability of distal sheath511. Thus, certain cells520may compress at portions of the distal sheath while other cells expand at other portions of the distal sheath when the distal sheath511is bent. In one example, cells520are substantially diamond-shaped, with each cell being defined by four struts521. In at least some examples, the length of each cell in the axial direction of distal sheath511is between about 0.5 mm and about 5 mm when distal sheath511is substantially straight. The number of cells formed in the distal sheath may be varied. In some examples, three, four, five or six cells may be formed about the circumference of outer wall516at a given longitudinal extent of the distal sheath. Also, the number of rows of cells axially disposed along the length of distal sheath511may vary. Generally, the smaller the cells in the axial direction and the greater the number of rows of cells, the greater the amount of flexibility that will be imported to distal sheath511.

After cutting pattern519into outer wall516of distal sheath511, a polymer jacket550may be added to the abluminal (i.e., outer) surface of outer wall516in order to increase the column strength of distal sheath511and prevent blood/debris from impinging on the valve (FIG. 6). Polymer jacket550may be formed of any suitable biocompatible polymer, including polyether block amide (e.g., PEBAX®), nylons, polyester resins, urethanes or suitable combinations thereof. A non-polymeric material may also be used to form jacket550. Additionally, a liner552, such as a polytetrafluoroethylene (PTFE) liner, may be added to the luminal (i.e., inner) surface of outer wall516to add lubricity to portions of the outer wall516that may contact the heart valve in compartment23of the delivery device.

Thus, after a pattern is cut into outer wall516of distal sheath511, the distal sheath still has enough column strength to be able to resheath a transcatheter aortic replacement valve while being flexible enough to traverse body tissue to the target location. For example, in transfemoral delivery, the distal sheath511is capable of more easily crossing the aortic arch and aligning with the native aortic annulus. Having distal sheath511formed of nitinol or another suitable material that is laser cut in this fashion provides the requisite column strength and flexibility. Additionally, wall516may be made thinner compared to traditional braided constructions because the conventional braided wires overlap one another, adding to the overall wall thickness.

FIGS. 7A and 7Billustrate the use of delivery device700having features of the present disclosure to deliver a medical device, such as a prosthetic heart valve, to an implant location. Delivery device700may include all of the features discussed above with reference toFIGS. 1-3and generally has proximal end702and distal end704. Delivery device700includes operating handle706for use by a physician or operator coupled at one side to outer shaft710, which in turn extends to slidable distal sheath712, forming compartment714therein for housing a prosthetic heart valve (not shown) disposed about an inner shaft (also not shown). The delivery device700further includes a conical distal tip716at distal end704. As shown in the enlargement ofFIG. 7B, the laser cut pattern719(e.g., the process of cutting cells720with struts721) in distal sheath714allows the distal sheath to easily bend during use, making the implantation process easier and quicker. The same or a similar pattern may, likewise, be cut into outer shaft710instead of, or in addition to, the pattern cut into distal sheath714.

FIG. 8is a comparison between a conventional distal sheath formed of braided construction and a laser-cut sheath formed with pattern519ofFIGS. 5A and 5B. In this comparison, a three-point bend test was performed on the two sheaths to displace a midpoint of each sheath between 0 and 0.5 inches. In this illustration, the two end points of each sheath were disposed about 3 inches apart. As seen from the comparison, almost 0.9 pounds of force is required to displace the midpoint of a sheath of braided construction a distance of 0.5 inches. Conversely, to displace the midpoint of a distal sheath having a laser-cut pattern519a distance of 0.5 inches, less than 0.4 pounds of force is required. Thus, the frame construction ofFIGS. 5A and 5Brequires less than half of the force of the braided construction for a displacement of 0.5 inches. This flexible construction reduces the risk of trauma to body tissue during delivery around tight turns.

Numerous modifications may be made to the illustrative embodiments and other arrangements may be devised without departing from the spirit and scope of the present disclosure as defined by the appended claims. For example, though the delivery system has been shown as a transfemoral delivery system, it will be understood that the teachings of the present disclosure are not so limited and that similar patterns may be cut into the outer sheath and/or distal sheath of transapical, transseptal or other delivery systems. Additionally, while the examples have been shown for a delivery system for transcatheter aortic valve replacement, the disclosed teachings are equally applicable for other valve replacement, such as, for example, mitral valve replacement, as well as for other catheters for valve replacement and/or repair. Moreover, the present disclosure may also be applied to catheters for other medical purposes, such as the implantation of stents and other medical devices, other types of percutaneous or laparoscopic surgical procedures and the like.

In some embodiments, a delivery device for a collapsible prosthetic heart valve includes an inner shaft having a proximal end and a distal end, an outer shaft disposed around the inner shaft and longitudinally moveable relative to the inner shaft, and a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, the compartment being adapted to receive the prosthetic heart valve. At least one of the outer shaft or the distal sheath may have a pattern of cutouts formed therein, the pattern including at least one ring around a circumference of the at least one of the outer shaft or the distal sheath, the at least one ring having at least one of the cutouts.

In some examples, the pattern includes a plurality of rings disposed along a longitudinal axis of the outer shaft or the distal sheath; and/or the plurality of rings may include a first set of rings having a first pattern and a second set of rings having a second pattern, the first pattern, the first set of rings being offset from the second pattern by a predetermined angle in the circumferential direction; and/or the first pattern may be offset from the second pattern by 90 degrees; and/or successive rings may alternate between a ring from the first set of rings and a ring from the second set of rings; and/or the at least one ring may include multiple discontinuous cutouts aligned with one another at a predetermined position along a longitudinal axis of the outer shaft in the distal sheath; and/or the at least one ring may include three discontinuous cutouts; and/or the at least one cutout may include an elongated portion and two teardrop portions on opposing ends of the elongated portion; and/or at least one of the outer shaft or the distal sheath may include stainless steel.

In some embodiments, a delivery device for a collapsible prosthetic heart valve includes an inner shaft having a proximal end and a distal end, an outer shaft disposed around the inner shaft and longitudinally moveable relative to the inner shaft, and a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, the compartment being adapted to receive the prosthetic heart valve. At least one of the outer shaft or the distal sheath may have a pattern of cutouts formed therein, the pattern including a plurality of polygonal cells extending through the at least one of the outer shaft or the distal sheath.

In some examples, the plurality of polygonal cells may include diamond-shaped cells; and/or the pattern may be formed in the distal sheath; and/or may further include a liner disposed on a luminal surface of the distal sheath; and/or may further include a polymer jacket disposed on an abluminal surface of the distal sheath; and/or at least one of the outer shaft or the distal sheath may include stainless steel.

In some embodiments, a method of forming a delivery device for a collapsible prosthetic heart valve includes providing an inner shaft having a proximal end and a distal end, an outer shaft disposed about the inner shaft and being longitudinally moveable relative to the inner shaft, and a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, the compartment being adapted to receive the prosthetic heart valve, and cutting a pattern on at least one of the outer shaft or the distal sheath at different axial extents.

In some examples, cutting a pattern may include forming at least one cutout having an elongated portion and two teardrop portions on opposing ends of the elongated portion; and/or the at least one cutout may include a plurality of cutouts arranged in a ring; and/or cutting a pattern may include forming at least one polygonal cutout on an outer surface of at least one of the outer shaft and the distal sheath; and/or the at least one polygonal cutout may include a plurality of diamond-shaped cells.