Patent Application
20140025085
The present disclosure relates to a catheter or microcatheter for treating uterine fibroids.
Uterine fibroids are benign tumors that develop in the uterus. A common treatment for uterine fibroids is uterine artery embolization. In this treatment, a relatively small catheter (sometimes called a microcatheter) is inserted into the bloodstream of the patient and positioned near the fibroids. Small particles or beads are delivered through the catheter and are deposited in the uterine arteries. The beads block or limit the blood supply to the fibroids, which may shrink the fibroids and prevent future growth.
There are two main issues with the microcatheters that are currently used to treat uterine artery embolization.
First, because the outer diameter of the beads is often larger than the inner diameter of the lumen of the catheter, a high pressure is required to force the beads through the lumen. In many cases, this high pressure is supplied manually by the practitioner's hand, through a syringe or plunger on the device handle. Supplying such a high pressure may be problematic for some practitioners.
Second, because the small beads are forced through an even smaller lumen, some beads may deform beyond their yield strain, and may emerge from the catheter with a permanent, oval-shaped deformation. It is desirable that the beads maintain their original generally round shape after being deposited, so such a deformation is undesirable.
Accordingly, there exists a need for a microcatheter that can deliver embolization beads without using excessively high pressure, and without significantly deforming the beads.
An embodiment is a catheter. The catheter includes a handle at a proximal end of the catheter. The catheter includes a loading port disposed on the handle. The loading port is capable of receiving an embolization bead. The catheter includes an elongate shaft extending distally from the handle. The catheter includes a radially expandable portion on the elongate shaft. The radially expandable portion has an inner diameter smaller than a diameter of the embolization bead. The embolization bead is capable of being forced distally through the elongate shaft by pressure applied from the handle. As the embolization bead travels distally through the radially expandable portion, the radially expandable portion expands radially locally in the vicinity of the embolization bead.
Another embodiment is a method of forming a radially expandable portion of an elongate catheter shaft. A tubular braid is formed. The braid is longitudinally stretched over a mandrel to produce a longitudinally stretched braid having a smaller diameter than the tubular braid. The longitudinally stretched braid is encased in a lubricious soft polymer. The lubricious soft polymer is sufficiently thick to prevent the longitudinally stretched braid from returning to the size of the tubular braid. The mandrel is removed.
Another embodiment is a method of forming a radially expandable portion of an elongate catheter shaft. A nitinol tube is provided. The nitinol tube has a transition temperature between room temperature and human body temperature. At a temperature below the transition temperature, a plurality of slots is formed in the nitinol tube to produce a slotted tube. At a temperature below the transition temperature, the slotted tube is disposed over a mandrel. At a temperature below the transition temperature, the slotted tube is encased in a lubricious soft polymer. At a temperature below the transition temperature, the mandrel is removed.
The foregoing and other objects, features and advantages disclosed herein will be apparent from the following description of particular embodiments disclosed herein, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles disclosed herein.
In this document, for all of the following descriptions, “proximal” is intended to mean the end closest to the practitioner, “distal” is intended to mean the end farthest away from the practitioner, and “longitudinal” is intended to mean extending between the proximal and distal ends.
A catheter is disclosed, which is capable of delivering embolization beads for treating uterine fibroids. The elongate catheter shaft includes a radially expandable portion at its distal end, which can expand radially locally when an embolization bead passes through it. In some cases, the catheter shaft includes a non-expandable portion, with an inner diameter comparable to the bead diameter, between the handle and the radially expandable portion. In some cases, the radially expandable portion is made from a tubular braid, stretched longitudinally over a mandrel, and encased in a lubricious soft polymer while still stretched. In other cases, the radially expandable portion is made from a slotted nitinol tube, encased in a lubricious soft polymer below the nitinol transition temperature. The polymer is thick enough to prevent the encased element from returning to its unstretched diameter or a larger size above the transition temperature.
The above paragraph is merely a generalization of several of the elements and features described in detail below, and should not be construed as limiting in any way.
The embolization beads 10 are typically small spheres, and are sometimes referred to as microbeads. The beads 10 are commercially available in various diameters, typically from about 0.5 mm to about 1 mm, and various materials, such as acrylic copolymers and PDA. Some beads 10 may be formed as layered structures, which may include more than one material. Depending of materials, structure and size, some beads 10 may be more elastic than others. It is envisioned that the catheters described herein will work with many, if not all, known beads 10, regardless of the elasticity of the beads 10, which is advantageous.
The catheter 1a of
The handle 2 may include a loading port 3, which is capable of receiving an embolization bead 10. The loading port 3 is drawn as a simple opening in
The catheter 1a includes an elongate shaft extending distally from the handle 2. Once a bead 10 is loaded into the catheter through the loading port 3 on the handle 2, it is advanced distally down the elongate shaft by pressure supplied by the practitioner pressing on the syringe. It is assumed that the handle 2 and the shaft are mated in a known manner, with a suitable connection that allows the bead 10 to pass easily from the handle 2 to the shaft.
The catheter shaft of
There may be advantages to using the relatively large-inner-diameter proximal portion 4. First, the distal travel of the bead 10 may be initiated with relatively little pressure from the handle. Second, there is no deformation of the bead 10 in the proximal portion 4 of the shaft. Third, the relatively large size may improve navigation within large blood vessels. More specifically, the relatively large proximal portion 4 may be easier to push forward in the large vessel that make up most of the path to the target site, when compared with a typical known catheter.
The relatively large inner diameter cannot be used all the way to the distal end of the shaft, though, because it would be too large for the vessels close to the target site. Instead, the shaft includes a radially expandable portion 5 at its distal end, which has an inner diameter smaller than both the inner diameter of the proximal portion 4 and the diameter of the bead 10. Such a radially expandable portion 5 may be relatively short in length, compared with the relatively long proximal portion 4, since the small diameter is only required relatively close to the target site.
The radially expandable portion 5 is intended to expand locally as a bead 10 is passed through it. Typically, the expansion is piece-wise down the length of the radially expandable portion 5, with the expansion occurring only in the immediate vicinity of the bead 10, and the expansion following the bead 10 distally from the proximal portion 4 to its exit at the distal end of the radially expandable portion 5. Alternatively, it is also possible for the full radially expandable portion 5 to expand all at once, and remain expanded during the entire travel of the bead 10 through it.
Some typical diameters for the catheter shaft portions are as follows. A typical inner diameter for the proximal portion 4 is 0.055 inches (1.40 mm) to 0.058 inches (1.47 mm). A typical outer diameter for the proximal portion is 0.065 inches (1.65 mm), which corresponds to a catheter size of 5F. A typical inner diameter for the radially expandable portion 5 is 0.020 inches (0.5 mm) to 0.027 inches (0.7 mm). A typical outer diameter for the radially expandable portion 5 is 0.030 inches (0.77 mm) or 0.035 inches (0.90 mm), which corresponds to a catheter size of 2.3F or 2.7F. It is understood that any suitable size may be used, and not just the sizes listed here.
There may be advantages to using the relatively short radially expandable portion 5 at the distal end of the shaft. First, the relatively small outer diameter improved maneuverability inside the small vessels near the target site. Second, the catheter lumen may inflate to a larger inner diameter under the injection pressure. This, in turn, may reduce deformation of the bead 10 and may create less pressure against the catheter lumen wall when the bead 10 passes through the catheter lumen. The reduction of pressure may result in less friction force between the bead 10 and the lumen wall, and may therefore require less injection pressure to sustain the movement of the bead 10. Third, the radially expandable portion 5 may be made of or made with a highly elastic polymer. Once the pressure is removed, the radially expandable portion 5 may recover back to its original smaller inner diameter on its own. Fourth, the radially expandable portion 5 may allow for use of harder and less elastic beads than typical known catheter shafts.
Thus far, one configuration has been described, where the elongate shaft has a relatively large-diameter proximal portion adjacent or directly adjacent to the handle, followed by a relatively small inner-diameter distal portion, where the distal portion 2 is radially expandable as a bead 10 passes through it. For this configuration, the proximal portion 4 is generally longer than the radially expandable portion 5, since the relatively small-diameter portion is required only near the target site. Alternatively, the proximal portion 4 may be the same length as the radially expandable portion 5 or shorter than the radially expandable portion 5, although these two cases are less common.
Many of the advantages of the configuration of
There are various structures that may be used for the radially expandable portion 5. A first example is a braided tube 6a, which may be stretched longitudinally and encased in a lubricious soft polymer 9, which can be commercially available and sold under names as such as Tecophilic 83A. A second example is a slotted nitinol tube 6b, which may also be encased in a lubricious soft polymer 9. Both of these examples are described more fully below.
In
In
In
The thickness of the polymer 9 depends on the precise geometry and materials for the braid, but in general, the polymer should be thick enough so that when released from the mandrel 8, the polymer 9 prevents the braid 7 from returning to its original unstretched size, namely that of the tubular braid 6a. If the polymer 9 is made too thick, it will stiffen the longitudinally stretched braid 7 and will reduce the amount that it can radially expand, under the influence of a given inflation pressure. As such, in general, the radially expandable portion 5a has a radial expandability that depends on the thickness of the lubricious soft polymer 9; the thinner the polymer wall, the easier it is to inflate the tube.
Finally, in
Note that in the radially expandable portion 5a of
First, a tube is provided, made of nitinol, although any suitable shape memory material may also be used. The nitinol tube may have a transition temperature between room temperature and human body temperature. Below the transition temperature, the nitinol may have a relatively small size. Above the transition temperature, the nitinol may have a relatively large size. To form the radially expandable portion 5b shown and described herein, the steps below are all performed below the transition temperature, such as at room temperature or some other cooled temperature.
Next, slots or holes in the tube are cut, etched or ablated, to form a slotted tube 6b, as shown in
Note that if the slotted tube 6b were heated above the transition temperature at this stage, it would expand to a larger size. An example of a low-temperature (below the transition temperature, such as room temperature) inner diameter is 0.027 inches (0.7 mm), and of a high-temperature (above the transition temperature, such as human body temperature) inner diameter is 0.055 inches (1.4 mm). These sizes are just examples, and any suitable sizes may be used.
In
In
One way to deposit the lubricious soft polymer 9 onto the slotted tube 6b is to dip the slotted tube 6b into a solution of hydrophilic polymer, done at a temperature below the transition temperature. Such a dipping may produce a single layer, as shown in
In some cases, it may be that a single layer doesn't have enough thickness to adequately restrain the nitinol tube at higher temperatures. For these cases, the tube 6b may be dipped again.
Finally,
In some cases, the polymer 9 may be formed as discrete longitudinal segments, along the length of the radially expandable portion 5, 5a, 5b. For instance, the polymer 9 may be formed as a single segment, and then cut into segments afterwards. In other cases, the polymer 9 may be formed in discrete pieces. In general, it is easiest to manufacture elements having five or fewer polymer segments.
It will be understood that the catheters 1a, 1b described herein may also be used for therapies other than for treating uterine fibroids.
It will also be understood that polymers having a variety of elasticities may be used, as long as one adjusts the thickness of the polymers appropriately. In general, the polymer coating of an element should be thick enough to prevent the element from expanding in diameter of its own volition, whether through resistance to an applied longitudinal expansion or through shape memory.
Unless otherwise stated, use of the words “substantial” and “substantially” may be construed to include a precise relationship, condition, arrangement, orientation, and/or other characteristic, and deviations thereof as understood by one of ordinary skill in the art, to the extent that such deviations do not materially affect the disclosed methods and systems.
Throughout the entirety of the present disclosure, use of the articles “a” or “an” to modify a noun may be understood to be used for convenience and to include one, or more than one, of the modified noun, unless otherwise specifically stated.
Elements, components, modules, and/or parts thereof that are described and/or otherwise portrayed through the figures to communicate with, be associated with, and/or be based on, something else, may be understood to so communicate, be associated with, and or be based on in a direct and/or indirect manner, unless otherwise stipulated herein.
Although the methods and systems have been described relative to a specific embodiment thereof, they are not so limited. Obviously many modifications and variations may become apparent in light of the above teachings. Many additional changes in the details, materials, and arrangement of parts, herein described and illustrated, may be made by those skilled in the art.
This application claims the benefit of U.S. Provisional Application No. 61/672,946 filed Jul. 18, 2012.
| Number | Date | Country | |
|---|---|---|---|
| 61672946 | Jul 2012 | US |
