Patent Application
20070088257
1. Field of the Invention
The invention relates to interventional catheters, and more particularly to rapid exchange balloon catheters.
2. Brief Description of the Related Art
Rapid exchange balloon catheters are described in U.S. Pat. Nos. 4,762,129 and 5,040,548, the entireties of which are incorporated herein by reference. These rapid exchange catheters include a distal guidewire lumen which extends through the balloon from a distal end of the balloon to a guidewire exit port that is proximal of the balloon, but which is distal of the proximal end of the catheter. In these and other known rapid exchange balloon catheter systems the catheter shafts include a proximal stiff catheter section extending along about 75% of the catheter length and a distal more flexible portion of the catheter between the stiff section and the balloon. For catheters which are designed for angioplasty or for stent delivery, the portion of the catheter proximal of the balloon and distal to the stiffer proximal catheter section should be simultaneously very flexible to navigate the coronary arteries, have good column strength to provide pushability, and have good kink resistance. The proximal catheter section generally requires good column strength and less flexibility.
Solid wires or hypotubes have been used for the proximal sections of rapid exchange catheters due to their excellent pushability and small diameter. However, the hypotubes and wires which have been used do not have the flexibility required for the distal flexible portion of the catheter.
U.S. Pat. No. 4,762,129, granted to Bonzel, has a short guidewire lumen with the guidewire exiting the catheter shaft just proximal of the balloon. The short exchange length of the Bonzel catheter can provide improved ease and speed of use for the user. The Bonzel catheter has drawbacks, however, including the lack of guidewire support of the distal portion of the catheter shaft resulting in possibilities of kinking and lack of pushability.
Therefore, there is a need for an improved rapid exchange catheter with a short exchange length without sacrificing any of the performance features provided by a longer exchange length.
According to a first aspect of the invention, a rapid exchange catheter is comprised of a proximal catheter shaft formed of a hypotube, a distal catheter shaft formed of a hypotube, an expandable balloon attached to the distal catheter shaft; and a guidewire lumen extending from a distal end of the balloon, through an interior of the balloon to a proximal guidewire inlet adjacent a proximal end of the balloon. The distal catheter hypotube extends to within 3 cm of the proximal guidewire inlet.
According to another aspect of the invention, a rapid exchange catheter is comprised of a catheter shaft formed of a hypotube of a nickel titanium alloy, an expandable balloon attached to a distal end of the catheter shaft and a guidewire lumen extending from a distal end of the balloon, through an interior of the balloon to a proximal guidewire inlet adjacent a proximal end of the balloon. The catheter hypotube extends to within 3 cm of the proximal guidewire inlet.
According to a further aspect of the invention, a catheter is comprised of a first hypotube of a first metal, wherein a distal portion of the first hypotube is cut to provide a change in flexibility from a less flexible proximal end to a more flexible distal end, a second hypotube of a second metal, the second hypotube being more flexible than the first hypotube, wherein a distal portion of the second hypotube is cut to provide a change in flexibility from a less flexible proximal end to a more flexible distal end, a connection between the distal end of the first hypotube and the proximal end of the second hypotube, and a polymer jacket extending over the cut portion of the first and second hypotubes.
According to another aspect of the invention, a balloon catheter is comprised of a stainless steel proximal hypotube, a nickel titanium distal hypotube connected to the proximal hypotube, a cut portion at a distal end of the nickel titanium distal hypotube which provides increased distal flexibility of the catheter and an expandable balloon connected to the distal end of the nickel titanium hypotube. A distance between the spiral cut portion and the balloon is about 40 mm or less.
According to a further aspect of the invention, a balloon catheter is comprised of a stainless steel proximal hypotube, a nickel titanium distal hypotube connected to the proximal hypotube, a cut portion at a distal end of the nickel titanium distal hypotube which provides increased distal flexibility of the catheter and an expandable balloon connected to the distal end of the nickel titanium hypotube. A distance between the spiral cut portion and the balloon is about 40 mm or less.
According to another aspect of the invention, a balloon catheter is comprised of a nickel titanium hypotube having a cut distal end for increased distal flexibility, a polymer jacket surrounding the cut distal end and an expandable balloon connected to the distal end of the nickel titanium hypotube. A distance between the laser cut distal end and the balloon is about 40 mm or less.
According to a further aspect of the invention, a rapid exchange catheter is comprised of a proximal catheter shaft formed of a hypotube having a first outer diameter, a distal catheter shaft formed of a hypotube having a second outer diameter, an expandable balloon attached to the distal catheter shaft, and a guidewire lumen extending from a distal end of the balloon, through an interior of the balloon to a proximal guidewire inlet adjacent a proximal end of the balloon. The second outer diameter is less than the first outer diameter.
According to another aspect of the Invention, a method of performing a vascular procedure in a mammalian patient comprises the steps of inserting a catheter into the vasculature of the patient and moving the catheter to a location in the vasculature of the patient. The catheter includes a proximal catheter shaft formed of a hypotube, a distal catheter shaft formed of a hypotube, an expandable balloon attached to the distal catheter shaft and a guidewire lumen extending from a distal end of the balloon, through an interior of the balloon to a proximal guidewire inlet adjacent a proximal end of the balloon. The distal catheter hypotube extends to within 3 cm of the proximal guidewire inlet and moving the catheter to a location in the vasculature of the patient.
Still other aspects, features, and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of embodiments constructed in accordance therewith, taken in conjunction with the accompanying drawings.
The invention of the present application will now be described in more detail with reference to embodiments of the apparatus and method exemplifying principles of the invention, given only by way of example, and with reference to the accompanying drawings, in which:
Referring to the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures.
A catheter system 10 illustrated in
Because the details of stents and guidewires are well known to those skilled in the art, and because the present invention is not limited by such details, further description of the stent 30 and the guidewire 40 will not be given so as to not obscure the principles of the present invention.
The shaft 28 advantageously includes a structure which changes the flexibility of the shaft. According to an advantageous embodiment of the present invention, a portion of the shaft includes one or more lengths of hypotubing, one or more overlayers or exterior jackets, or both. While several exemplary embodiments of a catheter 20 including hypotubing will now be described, the present invention is not limited to the details of these embodiments.
While the exemplary embodiments described herein refer to two hypotube portions, the present invention is not so limited, and extends to a monolithic hypotube having features described elsewhere herein to modify its flexibility, and extends to a hypotube including more than two portions.
Another advantageous, optional feature of the present invention includes that the hypotube 50 has one or more cuts 56 formed therein, which increases the flexibility of the hypotube in the area of the cut. By way of example and not of limitation, the shape of the cut can be helical, longitudinally slotted, laterally slotted, as well as other shapes and orientations of one or more slots, so that the flexibility of the hypotube increases distally. Additionally, the slot 56, or the density of slots, can be non-uniform, and advantageously can be formed so that the configuration of the slot contributes to the increasing flexibility of the shaft 28. By way of non-limiting example, a helical slot, such as that illustrated in
The distal end of each portion of the hypotube 50 is designed, e.g., by selecting a cut configuration, outer diameter and wall thickness of the hypotube, and the like, so that the flexibilities of the distal and of a proximal portion is similar to that of the proximal end of a distal portion. That is, where two portions of the hypotube meet, there is not a significant increase or decrease in the flexibility of the hypotube 50.
Yet another advantageous, optional feature of the present invention is the further inclusion of an outerjacket 66 over the hypotube 50. By forming the jacket 66 of a biocompatible material, e.g., a biocompatible polymer, the catheter shaft 28 can be made fluid tight to the inflation fluid passing through inflation lumen 64, relatively low friction to assist in passing the catheter 20 through the vasculature of a patient, and the flexibility of the catheter shaft 28 can further be modified. More specifically, the jacket 66 can be formed of a material, and having thicknesses, so that the flexibility of the shaft 28 increases distally. In the embodiment illustrated in
Another advantageous, optional feature of the present invention is that the cut 56 in the hypotube portion(s) terminates before reaching the distal end of that portion, leaving a ring of uncut material at the distalmost part of that hypotube portion. With reference to the exemplary embodiment illustrated in
Turning back to
Turning now to
In the exemplary embodiment illustrated in
Somewhat different from other embodiments described herein, the jacket 66 terminates before the distal end of the distal hypotube portion 54 at a point 84, and the bonding tube 80 is bonded over the end of the distal portion 54 and bonded to the jacket 66. The bonding tube 80 is formed of a material that will, when melted, blend into and with the material of the jacket 66 and the balloon 22. Thus, while
Another advantageous, optional feature of the present invention includes that the flexibility of the shaft 28 is designed to increase from proximal portions of the shaft toward the distal end, so that the shaft is more flexible distally. One exemplary embodiment of the present invention includes a proximal portion 52 which is more rigid, less flexible, than a distal portion 54. This change in flexibility in the shaft 28 can be achieved according to the present invention through one or more of the following: using different materials for the different portions of the hypotube; changing the outer diameter (OD) of the shaft to be smaller distally; changing the composition of the polymer jacket material(s), thickness of the polymer jacket, and number of layers of polymer jackets; and the pattern(s) of the cuts in the hypotubing.
Yet another advantageous, optional feature of the present invention includes one or more coatings on the inner, outer, or both inner and outer, surfaces of the catheter shaft 28. The coatings on the catheter shaft are selected to provide lubricity, drug delivery, and/or other beneficial characteristics to the catheter 20, as well understood and appreciated by the skilled artisan.
According to a yet further advantageous embodiment, proximal portions of the hypotube 50, e.g., the proximal portion 52, are formed of a stainless steel, while distal portions of the hypotube, e.g., the distal portion 54, is formed of a superelastic material, e.g., a nickel titanium alloy, e.g., NiTi. The dimensions and exact alloy materials of the two portions are selected so that the flexibility of the hypotube 50, and the shaft 28, increases distally, as described elsewhere herein. Stainless steel hypotubes extending all the way to the balloon 22 may be less preferable, because they may experience permanent deformation or kinking. A NiTi distal hypotube portion can eliminate the permanent deformation problem, because of its known deformation behavior. While a NiTi shaft extending all the way from the proximal end to distal end can also be used in the present invention, it is also less preferably because of the increased cost of that solution. Alternatively, a NiTi portion can be replaced with a low residual stress stainless steel tubing, or another superelastic material, known well by those of skill in the art.
The cut, jacketed hypotubes translate forces well in compression, translate some forces in tension, and transmit torque very well. Torquability is important to allow the practitioner, e.g., physician, to navigate the catheter through tight lesions or tight turns in the patient's vasculature by rotating the catheter. Pushability, or the ability to transmit forces in compression, and is sometimes measured by comparing the amount of force the physician must apply at the proximal end to get a given force at the distal end. The short rapid exchange length of catheters in accordance with the present invention provides improved trackability because the short contact length between the guidewire lumen and the guidewire provides less friction than a longer guidewire lumen.
The proximal guidewire port 24 can further optionally include a longitudinal groove on the exterior of the shaft 28, such as that described in co-assigned provisional application No. 60/684,775, filed 26 May 2005, entitled “Rapid exchange balloon catheter with reinforced shaft”, by Beau M. Fisher et al., the entirety of which is incorporated by reference herein.
According to a particularly preferred embodiment, the distalmost end of the distal end of the hypotube 50 is a distance X from the proximal guidewire port 24, or is a distance Y from the proximal end of the balloon 22, or both; wherein X is between about 0.05 cm and about 5 cm, preferably less than 3 cm, more preferably less than 2 cm, most preferably between 0.1 cm and 0.3 cm; and wherein Y is between about 0.1 cm and about 10 cm, preferably between about 0.1 cm and about 4 cm, more preferably less than about 3 cm, most preferably between 0.6 cm and 1 cm. It is also useful for understanding principles of the present invention to define the distance Z=Y−X, the distance from the proximal end of the balloon 22 to the proximal guidewire port 24. Another aspect of the present invention is, therefore, dimensioning portions of the catheter 20 so that Z is quite short, that is, the rapid exchange tube 34 extends very little proximally of the proximal end of the balloon 22. For example, Z is preferably about 0.1 cm to about 5 cm, more preferably about 0.2 cm to about 1.5 cm.
In the foregoing description, the flexibility of the catheter shaft 28 has been described as increasing distally. According to a somewhat less preferred embodiment of the present invention, but still within the scope of the present invention, one or more sections of the catheter shaft 28, including but not limited to the one or more junctions between hypotubing portions, may have flexibilities that are less than portions that are proximal thereto. That is, the present invention extends to the optional inclusion in the catheter shaft 28 of some portions of the catheter shaft that are stiffer than in embodiments in which the flexibility of the catheter shaft does not decrease distally. In this context, the present invention also includes embodiments in which the flexibility of the catheter shaft does not change over the length of some portions, and also includes more flexible distal portions and, as described above, less flexible portions.
For both longitudinal 90 and lateral cuts 92, it is preferable that the cuts are formed so that the flexibility of the particular hypotube portion is substantially the same in every lateral direction, that is, the cuts are formed so that the particular hypotube portion has essentially the same flexibility in all radial directions taken from the centerline or longitudinal axis of that hypotube portion.
Although the foregoing describes aspects of the present invention in the context of a rapid exchange balloon angioplasty catheter, the present invention is not limited to such devices. Accordingly, additional embodiments exemplifying principles of the present invention include rapid exchange and non-rapid exchange catheters, balloon and non-balloon catheters including, but not limited to, infusion catheters, angiography catheters, thermal and/or RF and/or laser ablation catheters, and fixed-wire vascular catheters. With reference to
With reference to the drawing figures, an exemplary method embodying further principles of the present invention will now be described. A catheter in accordance with the present invention is inserted into the vasculature of a mammalian, preferably human, patient, optionally over a guidewire, and is advanced to a vascular location of interest. The balloon of the catheter may then be inflated or expanded in a manner well appreciated by the skill artisan, e.g., by increasing the pressure applied to an inflation fluid, and the balloon's diameter increases. When a stent is positioned on the exterior surface of the balloon, the stent is thus expanded, in a well know manner. Thus, the balloon and/or the stent can be expanded against the interior surface of the vascular vessel, which may include plaques, the vascular intima, and other structures.
While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. Each of the aforementioned documents is incorporated by reference herein in its entirety.
