Patent Application
20190269884
The invention relates to a catheter system having a reinforced catheter shaft and a method of manufacturing a reinforced catheter shaft. In particular, the invention relates to a catheter shaft having a reinforcement layer comprised of braids or a coil or combination thereof. The braided reinforcement layer may have a constant picks per inch (PPI) or a variable PPI along the shaft. Similarly, the coiled reinforcement layer may have a constant pitch between coils or a variable pitch between coils. The reinforced catheter shaft may be manufactured by a continuous reel-to-reel process using liquid polymers that are heat-hardened or by a discrete process using extruded tube that is shrunk with heat.
Conventional catheter systems, such as the catheters used in stent and balloon dilatation systems, are widely used during vascular procedures, for example, balloon angioplasty or stenting, for treating vascular disease. These catheters require a high degree of deliverability to properly reach the target location in the blood vessel. Two major aspects of deliverability of a catheter are pushability and flexibility. Pushability is defined as the ability to transmit pushing power from the proximal end of the catheter (held by the operator's hand) to the distal end of the catheter, for example, in order to traverse and cross calcifications, clots, occlusions, narrowed blood vessels, and other obstacles encountered during a vascular procedure. Flexibility is defined as the catheter's ability to bend, for example, during navigation through torturous vessels.
Catheter systems are typically inserted into a blood vessel over a flexible guidewire, which is inserted and navigated through the vessel before insertion of the catheter. During the procedure, the catheter slides over the guidewire through a guidewire shaft—a tube running through the length of the catheter. In some catheter systems, the guidewire shaft runs through the entire length of the catheter while in other systems it may run only in the more distal part of the catheter. In any event, friction between the guidewire and the shaft would reduce pushability and affect flexibility of the catheter thus reducing overall deliverability.
Sometimes, while using a cardiovascular catheter, the effective diameter of the shaft lumen is reduced or the generally circular shape of the shaft lumen changes shape (e.g., becomes more ellipsoidal), and may create or increase the friction between the shaft (more particularly, the inner wall of the catheter) and the guidewire. For example,
Additionally, during balloon inflation in procedures such as balloon angioplasty and stenting, the fluid pressure used to inflate the balloon at the end of the catheter may cause longitudinal elongation of the shaft, thus reducing the diameter of the guidewire lumen. For example,
One possible solution to this requirement may be to increase the diameter of the guidewire shaft. However, that would increase the catheter's crossing profile and reduce deliverability. Another solution may be coating the inner wall of the guidewire shaft with materials having low friction coefficient such as Teflon, HDPE (high density polyethylene), etc. This as well may increase the crossing profile of the catheter and thus reduce deliverability.
Thus, in view of the foregoing, there exists a need to reduce or prevent friction between the guidewire and the guidewire shaft (i.e., the inner wall of the catheter) during vascular procedures. In particular, there exists a need for reducing or preventing friction between the guidewire and the guidewire shaft while maintaining a small crossing profile as possible for the catheter.
A catheter shaft of the present invention comprises a plurality of polymer layers and a reinforcement layer extending through all or a portion of the catheter shaft. The reinforcement layer may comprise a braided or coiled tubular structure or a combination of both. The picks per inch (PPI) in the case of a braided reinforcement layer or the pitch in the case of a coiled reinforcement layer may vary along the shaft or may be constant.
The distal tip of the catheter may be tapered or have a constant diameter with the rest of the catheter. The catheter further comprises an inner polymer layer and one or more additional layers. The distal tip of the catheter may include the reinforcement layer or may consist of only one or more polymer layers to form an atraumatic tip.
The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:
A catheter shaft of the invention generally includes a catheter wall having an inner layer, an outer layer, and a reinforcement layer disposed between the inner and outer layers. Alternatively, the catheter wall may include one or more middle layers in addition to the inner layer, outer layer, and reinforcement layer. Deliverability properties (i.e., pushability and flexibility) of the catheter may be modified by changing the material(s) of the reinforcement layer, the material(s) of the inner layer, the middle layer(s), or the outer layer, the longitudinal (i.e., along the length of the catheter shaft) density of the reinforcement layer (e.g., pitch or PPI), and/or the structure of the reinforcement layer (e.g., a braid and/or a coil). The inner layer of the catheter shaft is defined as the layer that creates the inner luminal surface of the catheter shaft lumen while the outer layer of the catheter shaft is defined as the layer directly abutting a vessel wall and the middle layer (if included) comprises the one or more layers between the inner layer and the outer layer.
In one embodiment, the catheter shaft may include more than two polymer layers. For example, the catheter wall may include multiple polymer layers, e.g., three, four, or five layers of polymers, although one skilled in the art will recognize that any suitable number of layers may be used to form the catheter shaft. In any case, each layer may include the same polymer or a different polymer.
The catheter shaft may further include a balloon coupled to a distal end of the outer wall at a bonding region. The balloon may be secured to the catheter wall by, for example, adhesives or other suitable polymer-to-polymer bonding as is known in the art.
The catheter shaft may further include a catheter tip at the distal end of the catheter shaft. The catheter tip may extend beyond the bonding region by about 0.3 mm to 10 mm. In one embodiment, the catheter tip may include a distal taper, tapering from a first diameter to a second, smaller diameter at the distal-most end of the catheter shaft. The catheter tip may taper from the balloon bonding region to a distal-most end of the catheter shaft. In another embodiment, the longitudinal length of the catheter shaft may have a uniform diameter along its entire length. In this embodiment, the distal-most end may have a rounded edge. In another embodiment, the distal tip may include a tapered outer diameter and a tapered inner diameter. For example, the outer diameter and the inner diameter may both taper at the same rate. In another example, the outer diameter may include a taper at a first rate while the inner diameter tapers at a second rate.
The reinforcement layer of the catheter shaft may comprise a braided reinforcement layer and/or a coiled reinforcement layer disposed between the inner layer and the outer layer of the catheter. In embodiments having more than two layers, the reinforcement layer may be disposed between any two adjacent layers in the catheter shaft. The reinforcement layer may extend to the distal-most end of the catheter shaft. Alternatively, the braided reinforcement layer or coiled reinforcement layer may terminate proximal to the distal-most end, leaving a portion of the catheter tip made entirely of one or more layers of polymer as an atraumatic tip. The atraumatic tip may have a length between 0.3 mm and 10 mm.
In the embodiment where the catheter shaft includes a taper on either or both of the inner diameter and the outer diameter, the reinforcement layer (either the coil or the braided reinforcement layer) may also have a taper. For example, the reinforcement layer may have a first, constant diameter along a first length of the catheter shaft and taper to a second, smaller diameter along a second length that is distal to the first length.
The reinforcement layer of the catheter shaft may include a braided reinforcement structure/layer. A braided reinforcement layer includes crisscrossing wires that are woven around the circumference of the catheter wall. The braided reinforcement layer may include a picks per inch (PPI) of about 20 to about 150. PPI is defined as the number of weft threads of wire per inch of woven braid. A higher PPI value corresponds to a higher number of windings per inch of the catheter wall and a more flexible catheter wall. A lower PPI value corresponds to a lower number of windings per inch of the catheter wall and a corresponding less flexible catheter wall. In an example, the braided reinforcement layer may have a constant PPI along the entire length of the catheter wall. In an alternative example, the braided reinforcement layer may have a variable PPI along the length of the catheter. The braided reinforcement layer may include any suitable braid as is known in the art. For example, the braided reinforcement layer may include a “1 under 2 over 2” braid. Other suitable braids may include “over 1 under 1,” “over 2 under 2,” a diamond pattern, or a variable pick.
The reinforcement layer of the catheter shaft may include a coiled reinforcement structure/layer. A coiled reinforcement layer includes one or more coiled wires around the circumference of the catheter wall. The coiled reinforcement layer may include a pitch (i.e., a distance between adjacent coils) of about 0.1 mm to about 0.5 mm. A lower pitch corresponds to a higher number of windings per inch of the catheter wall and a more flexible catheter wall. A higher pitch corresponds to a lower number of windings per inch of the catheter wall and a less flexible catheter wall. In an example, the coiled reinforcement layer may have a constant pitch between adjacent windings along the entire catheter length. In another, the coiled reinforcement layer may have a variable pitch along the catheter length. As an example of a coiled reinforcement layer having variable pitch, the coiled reinforcement layer may gradually increase in pitch from a proximal end to a distal end of the catheter wall or the coiled reinforcement layer may gradually decrease in pitch from a proximal end to a distal end of the catheter wall. At the distal-most end of the catheter shaft, the coiled reinforcement layer may be wound into a circular ring so as not to leave a free end of wire.
The reinforcement layer of the catheter shaft may be a hybrid of the two reinforcement layers described above, such that the reinforcement layer includes both a coiled reinforcement layer region and a braided reinforcement layer region. In one embodiment, the coiled reinforcement region may be proximal to the braided reinforcement region. In an alternative embodiment, the coiled reinforcement region may be distal to the braided reinforcement region. Each of the coiled reinforcement region and braided reinforcement region may provide different deliverability characteristics. For example, the coiled reinforcement region may be more flexible in bending but less resistant to an axial load (e.g., pulling forces or pushing forces) when compared to the braided reinforcement region. Each of the coiled reinforcement region and braided reinforcement region may have any suitable length along the length of the catheter wall. The preferred length for the coiled portion is about 3 mm to 300 mm and the preferred length for the braided portion is about 150 mm to 300 mm. The interface region between the coiled reinforcement region and braided reinforcement region can be located anywhere between the proximal end of the catheter and the distal tip.
Generally, the inner layer of the catheter shaft may include a thickness of 0.025 mm to 0.5 mm, preferably about 0.13 mm. The optional middle layer(s) may include a thickness of 0.025 mm to 0.5 mm, preferably about 0.06 mm. The outer layer may include a thickness of 0.025 mm to 0.5 mm, preferably about 0.04 mm.
The inner layer of the catheter shaft may comprise a polymer that has a low coefficient of friction so as to minimize any friction against a guidewire when the catheter shaft is inserted over the guidewire. For example, the inner layer may be made of expanded polytetrafluoroethylene (ePTFE or Teflon) or any other suitable polymer as is known in the art, preferably one having a low frictional coefficient.
The middle and outer layers may be made of the same or different biocompatible material. For example, the middle and outer layers may be made from polyether block amide (PEBAX), polyamide, polypropylene, polyether ether ketone (PEEK), polyimide (PI), polyolefins (e.g., polypropylene, polyethylene) or other suitable materials as is known in the art.
The braided reinforcement layer and/or the coiled reinforcement layer may comprise one or more metals or metal alloys. For example, the braided reinforcement layer and/or the coiled reinforcement layer may be made of stainless steel, titanium, gold, cobalt-chromium, platinum-iridium, nitinol, an amorphous metal alloy and/or any suitable combination of metals or metal alloys. Alternatively, the braided reinforcement layer and/or the coiled reinforcement layer may be made of a polymer. For example, the braided reinforcement layer and/or the coiled reinforcement layer may be made of polyamide, nylon, polyurethane, poly-paraphenylene terephthalamide, polyether ether ketone (PEEK), or any suitable biocompatible polymer as is known in the art.
The individual wires of the braided reinforcement layer and/or the coiled reinforcement layer may have a width of 0.0002 inch (0.00508 mm) to 0.01 inch (0.254 mm) and may have any suitable cross section, e.g., rounded or rectangular. One of skill in the art will recognize that any suitable width and diameter of wire may be used for the reinforcement layer.
As the catheter shaft bends and/or twists during insertion or retraction from a blood vessel (or other lumen), the braided reinforcement layer and/or the coiled reinforcement layer prevents the catheter wall from collapsing to a reduced diameter causing friction against the guidewire. Moreover, during inflation of a balloon, the braided reinforcement layer and/or the coiled reinforcement layer prevents the catheter wall from stretching, deforming, and/or shrinking due to the higher fluid pressure around the catheter wall in the balloon region. Stretching, deforming, and/or shrinking of the catheter wall may reduce the diameter of the catheter wall and thus also contribute to friction against the guidewire.
In a preferred example, the balloon may be secured to the outer wall by heat welding to fuse polymer of the balloon with polymer of the outer layer of the catheter shaft. Heat welding may include contacting a heated die to a portion of the balloon and the outer layer of the catheter wall at a balloon bonding region.
Optionally, the distal tip of the catheter may include an atraumatic tip comprising a taper. The atraumatic tip may include any of the same polymers that comprise the catheter shaft as described above such as, for example, polyimide (PI), polyamide (PA), or PEBAX. The distal tip may be tapered by reducing the diameter of the outer layer by, for example, machining the outer layer using a lathe. The distal tip may be tapered using a thermal process including a heated die having the desired tapered shape. In particular, the steps of tapering the distal tip include: positioning a heat shrink tube around the distal tip of the catheter, positioning the distal tip (having the heat shrink tube thereon) within a heated die, and closing the heated die over the distal tip to form the desired tapered shape. As the die closes on the tip, the combination of heat, die geometry, and the heat shrink tube form the distal tip into the desired tapered shape.
In another embodiment, the distal tip of the catheter may include a rounded, non-tapered tip. The rounded, non-tapered tip may be formed by positioning the distal tip in a heated die having the desired tip shape and end finish. The heated die is closed such that the polymer at the distal tip is pressed and formed into the desired rounded, non-tapered shape.
The following examples may incorporate one or more of the features described above. Said examples do not limit the invention but serve to illustrate exemplary embodiments within the scope of the invention.
A braided reinforcement layer 302 includes crisscrossing wires woven around the circumference of the catheter wall 304. In
As described above, the braided reinforcement layer 302 is disposed between polymer layers of the catheter wall 304. In one embodiment, the braided reinforcement layer 302 may be embedded within a layer of the catheter wall 304 (e.g., if a continuous process of manufacturing is used as described below).
The catheter shaft 300 of
Similar to the braided reinforcement layer of
In another embodiment (not shown), the proximal reinforcement region may have a higher PPI than the distal reinforcement region. The resulting catheter shaft is more flexible in the proximal reinforcement region than the distal reinforcement region. Thus, the catheter wall may be more flexible at the proximal end of the catheter wall and stiffer at the distal end of the catheter wall in this embodiment.
The coiled reinforcement layer 406 includes a coiled wire around the circumference of the catheter wall 404. In
Similar to the coiled reinforcement layer of
Alternatively (not shown), the proximal reinforcement may have a lower pitch than the distal reinforcement region. In this embodiment, the proximal reinforcement region is more flexible than the distal reinforcement region. In this embodiment, the resulting catheter wall will be more flexible at the proximal end of the catheter wall and stiffer at the more distal end of the catheter wall.
In some embodiments of the invention, combining the unique properties of a coiled reinforcement and a braided reinforcement in a single catheter shaft may provide additional utility to an operator.
The catheter wall 504 of
In
As described above, the braided reinforcement region and coiled reinforcement region may have any suitable length. In
Similar to the catheter wall 504 of
The proximal reinforcement region 552a and distal reinforcement region 552b include a variable PPI that gradually increases from a proximal end of the catheter wall 554 to a distal end of the catheter wall 554. In an alternative embodiment, the PPI of the braided reinforcement region may gradually decrease from a proximal end of the catheter wall 554 to a distal-most end 564 of the catheter wall 554.
In
Each of the coiled reinforcement region 556 and proximal 552a and distal 552b reinforcement regions may have any suitable length along the length of the catheter wall 554. For example, the catheter wall 554 may include proximal 552a and distal 552b reinforcement regions along the length of the catheter shaft 550 that houses all or a portion of the balloon 560. The distal reinforcement region 552b has a higher PPI and may correspond to a location along the balloon 560 where the greatest forces are exerted on the catheter wall 554 during inflation because a higher PPI braided reinforcement will provide greater resistance to any deformation of the catheter wall 554. The portion of the catheter wall 554 corresponding to the catheter tip 558 may include a coiled reinforcement region 556 as the coiled reinforcement region may provide more flexibility than a braided reinforcement region. In an alternative embodiment (not shown), the coiled reinforcement region may be proximal to the reinforcement regions. For example, the catheter tip may include a braided reinforcement region while the proximal portion of the catheter wall corresponding to the balloon may include a coiled reinforcement region having either a constant pitch or a variable pitch.
In yet another embodiment, the coiled reinforcement region 556 may include a variable pitch between the coils. The coiled reinforcement region 556 may include proximal coils having a smaller pitch and distal coils having a larger pitch. In an alternative embodiment, the coiled reinforcement region 556 may include proximal coils having a larger pitch and distal coils having a smaller pitch.
The braided reinforcement layer 602 (and/or coiled reinforcement layer) may terminate proximal to a distal-most end 614, leaving a portion of the catheter tip 608 entirely made of one or more polymer layers as an atraumatic tip 616.
In another embodiment (not shown), the catheter wall and catheter tip may have a uniform diameter along the entire length of the catheter shaft. In this embodiment, the distal-most end may have a rounded edge. The rounded distal most end may be formed by polishing the distal-most end until smooth.
The catheter shaft of the invention may be manufactured in a continuous (reel-to-reel) manufacturing process or a discrete manufacturing process using a mandrel. The continuous “reel-to-reel” method of manufacturing a catheter shaft may include forming an inner catheter wall layer around a mandrel. The mandrel may be made of a metal, such as, for example, stainless steel, titanium, or copper. To form an inner layer of polymer, the mandrel may be passed through a first polymer in a liquid state, such as liquid PTFE. The liquid first polymer may be cured by heating in, e.g., an oven. One or more optional middle layer(s) of polymer may be formed over the inner layer by passing the mandrel and hardened inner layer through a second polymer in a liquid state, such as, e.g., liquid PEBAX. The liquid second polymer may be cured by heating in, e.g., an oven. A reinforcement layer may be wound or woven over the first layer of polymer by a winding/braiding machine. In the embodiment wherein one or more middle layer(s) are formed, the reinforcement layer may be wound or woven over any one of the one or more middle layer(s). For example, a coil may be wound around the first, inner layer (or one of the optional middle layers) and/or a braid may be woven around that layer. The mandrel, the first layer of polymer, the optional one or more middle layer(s) of polymer, and the reinforcement layer may be passed through a third layer of polymer in a liquid state, such as, e.g., liquid PEBAX. The liquid third polymer may be cured by heating in, e.g., an oven. In certain embodiments, no first polymer (i.e., the inner layer having a low friction coefficient) is used and the resulting catheter shaft includes at least two polymer layers with a reinforcement layer therebetween.
In an alternative method of manufacturing a catheter shaft, the inner layer, one or more optional middle layer(s), and outer layer are formed from extruded tubes that are heat shrunk over one another. In particular, a first polymer tube (e.g., PTFE) may be extruded and positioned on the mandrel. The first polymer tube may be heated to thereby shrink the tube around the mandrel. One or more optional second polymer tube(s) (e.g., PEBAX) may be extruded and positioned on the mandrel and shrunk over the first polymer tube to form one or more of the optional middle layers. The optional second polymer tube may be heated to thereby shrink the tube in a similar fashion around the mandrel and first polymer tube. Similar to the continuous process, a reinforcement layer may be wound or woven over the first layer of polymer by a winding/braiding machine. In the embodiment wherein one or more middle layer(s) are formed, the reinforcement layer may be wound or woven over any one of the one or more middle layer(s). For example, a coil may be wound around the first polymer tube and/or a braid may be woven around the first polymer tube. A third polymer tube (e.g., PEBAX) may be extruded and positioned on the mandrel, first polymer tube, optional one or more middle tube(s), and reinforcement layer. The third polymer tube may be heated to thereby shrink the tube around the mandrel, first polymer tube, optional one or more middle tube (s), and reinforcement layer.
Variations and modifications will occur to those of skill in the art after reviewing this disclosure. The disclosed features may be implemented, in any combination and subcombination (including multiple dependent combinations and subcombinations), with one or more other features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated in other systems. Moreover, certain features may be omitted or not implemented.
Examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the scope of the invention disclosed herein. All references cited herein are incorporated by reference in their entirety and made part of this application.
