Patent Application
20090234282
The invention relates generally to a medical device. More particularly, the present invention relates to a catheter having an inflatable balloon at the distal end thereof joined on to the inside of an outer catheter shaft. In addition, the present invention relates to a balloon as bonded to the outer catheter shaft in an unexpanded configuration that has uniform dimensions including wall thickness, inner diameter, and outer diameter along its full length.
Cardiovascular disease, including atherosclerosis, is the leading cause of death in the U.S. One method for treating atherosclerosis and other forms of coronary narrowing is percutaneous transluminal coronary angioplasty, commonly referred to as “angioplasty” or “PTCA”. The objective in angioplasty is to enlarge the lumen of the affected coronary artery by radial hydraulic expansion. The procedure is accomplished by inflating a balloon of a balloon catheter within the narrowed lumen of the coronary artery. Radial expansion of the coronary artery occurs in several different dimensions, and is related to the nature of the plaque. Soft, fatty plaque deposits are flattened by the balloon, while hardened deposits are cracked and split to enlarge the lumen.
In addition to PTCA, balloon catheters are used for delivery of stents or grafts, therapeutic drugs (such as vaso-occlusion agents or tumor treatment drugs) and radiopaque agents for radiographic viewing. Other uses for such catheters are well known in the art.
In the design of catheter balloons, balloon characteristics such as strength, flexibility and compliance must be tailored to provide optimal performance for a particular application. In order to treat very tight stenoses with small openings, there has been a continuing effort to reduce the profile of the balloon catheter so that the balloon can reach and pass through the small opening of the stenoses.
Catheter balloons preferably have high flexibility and softness for improved ability to track the tortuous anatomy and cross lesions in the uninflated state. The anatomy of coronary arteries varies widely from patient to patient. Often a patient's coronary arteries are irregularly shaped, highly tortuous and very narrow. The tortuous configuration of the arteries may present difficulties to the physician in advancement of the balloon catheter to a treatment site. A highly tortuous coronary anatomy typically will present considerable resistance to advancement of the catheter over the guidewire. Therefore, it is important for the balloon catheter to be flexible and have a smooth profile to enable the balloon to be tracked to the treatment site. However, it is also important for a catheter shaft to be stiff enough to push the catheter into the vessel in a controlled manner from a position far away from the distalmost point of the catheter.
One factor that affects the profile of the balloon catheter is the joint between the proximal balloon neck and the outer catheter shaft. Typically, the balloon is welded or otherwise mechanically attached to the outer catheter shaft by placing the proximal balloon neck on the outside of the catheter shaft. By placing the balloon neck on the outside of the catheter shaft, the catheter presumably possesses a smoother profile for tracking the balloon to the treatment site since the “edge” created by the balloon to shaft joint is not pushed against the vessel wall while the balloon is being tracked through the patient's tortuous anatomy.
Another factor that affects the profile of the balloon catheter is the wall thickness of the balloon material. The profile of the deflated balloon is limited by the thickness of the neck and taper portions of the balloon. Usually, the neck and taper wall thicknesses of a torpedo-shaped angioplasty balloon are thicker than that of the body of the balloon due to the smaller diameter of the neck and taper portions. The thicker neck walls contribute to the overall thickness of the catheter, making tracking, crossing and re-crossing of lesions more difficult. Further, thick necks interfere with refolding of the balloon on deflation such that further inserting or withdrawing the deflated balloon may be difficult, occasionally even damaging the blood vessel. Reducing the wall thickness of the neck and taper portions reduces the overall profile of the deflated balloon.
Another factor which affects the profile of the balloon catheter is the balloon material itself. Angioplasty balloons are generally formed from relatively strong materials in order to withstand the pressures necessary for various procedures without failing. Typically, such characteristics require the use of a material that does not stretch appreciably. Use of polymeric materials that do not stretch appreciably consequently necessitates that the balloon is first formed by blow molding, and then the deflated balloon material, in the form of deflated wings, are folded around the catheter shaft prior to introduction of the balloon into the patient's body lumen. However, it may be desirable to employ balloons that do not have deflated folded wings, but which instead can be expanded to the working diameter within the patient's body lumen from an essentially wingless, cylindrical or tubular shape which conforms to the catheter shaft.
Thus, it is one aspect of the present invention to provide a balloon catheter with improved crossability and trackability, having a smooth reduced profile while simultaneously being sufficiently stiff to be tracked to the treatment site.
Embodiments of the present invention relate to a catheter having an outer catheter shaft, an inner catheter shaft, and a balloon. The outer catheter shaft has a proximal portion, a distal portion, an inside surface, an outside surface, and an inflation lumen extending there through. The inner catheter shaft has a proximal portion, a distal portion, an inside surface, an outside surface, and a guidewire lumen extending there through, wherein at least a portion of the inner catheter shaft is disposed within at least the distal portion of the outer catheter shaft. The balloon has a proximal end, a distal end, an inside surface, an outside surface, and an interior which is in fluid communication with the inflation lumen, wherein the outside surface of the balloon at the proximal end of the balloon is attached to the inside surface of the outer catheter shaft at the distal portion of the outer catheter shaft. In one embodiment of the present invention, the balloon has a uniform wall thickness, a uniform inner diameter, and a uniform outer diameter along its full length in an unexpanded configuration.
The foregoing and other features and advantages of the invention will be apparent from the following description of the invention as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. The drawings are not to scale.
Specific embodiments of the present invention are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. The drawing in which an element first appears is typically indicated by the leftmost digit(s) in the corresponding reference number. The terms “distal” and “proximal” are used in the following description with respect to a position or direction relative to the treating clinician. “Distal” or “distally” are a position distant from or in a direction away from the clinician. “Proximal” and “proximally” are a position near or in a direction toward the clinician.
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. It is noted that the invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Although the description of the invention is in the context of treatment of blood vessels such as the coronary, carotid and renal arteries, the invention may also be used in any other body passageways where it is deemed useful. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
Embodiments of the present invention relate to a balloon catheter having an outer catheter shaft having a balloon mounted at the distal portion thereof. The profile of the balloon catheter is improved by placing the proximal balloon neck inside the outer catheter shaft. This outer shaft to balloon neck joint allows for a smaller outer diameter at the joint between the outer catheter shaft and the balloon, thus providing a reduced catheter profile in the joint transition area with improved crossability, trackability and stiffness. In one embodiment of the present invention, the balloon as bonded to the outer catheter shaft in an unexpanded configuration has uniform dimensions including wall thickness, inner diameter, and outer diameter along its full length. A balloon with such uniform dimensions provides for a more flexible balloon by eliminating the thicker neck and taper portions of the balloon. A balloon with such uniform dimensions is not folded prior to inflation, but is instead expanded to the working diameter from a generally cylindrical or tubular shape. This no-fold aspect of the balloon also reduces the profile of the balloon catheter, thus resulting in improved crossability and trackability. Another advantage associated with a balloon having uniform dimensions as described above is ease of manufacture. By eliminating the neck and taper regions from the balloon, the balloon may be formed from a simple mould design, which can be longer than the balloon length required, thus allowing multiple balloons be cut to length from balloons formed from the overlength mould. Further explanation and details will now be described with reference to
Referring now to
Catheter 100 includes an outer catheter shaft 106 which includes at least one continuous lumen 214 extending from at or near its proximal end 110 to at or near its distal end 112 in order to provide for balloon inflation. Balloon 108 is located at or near distal end 112 of shaft 106, and a hub 116 is located at or near proximal end 110 of shaft 106. Hub 116 includes a balloon inflation port 118 to allow fluid communication between inflation lumen 214 and balloon 108 so that the balloon 108 may be inflated. Hub 116 will serve in a conventional manner to provide a luer or other fitting in order to connect the catheter 100 to a source of balloon inflation, such as conventional angioplasty activation device.
Balloon 108 includes a proximal neck end 120 and a distal neck end 122. At joint transition area 124, proximal neck end 120 of balloon 108 is placed inside and joined to the distal end 112 of outer catheter shaft 106, as shown in
In addition, edge 426 may be modified in order to create a tapered edge 427. Tapered edge 427 is illustrated as a dotted line in
Referring now to
In the coaxial dual lumen arrangement illustrated in
Other embodiments of balloon catheter 100 may have guidewire lumen 230 and inflation lumen 214 in other dual lumen arrangements, such as a circular guidewire lumen above a D-shaped inflation lumen or a circular guidewire lumen set above a crescent-shaped inflation lumen. For example, an alternative non-coaxial dual lumen arrangement is illustrated in
As previously described, the embodiments illustrated in
One skilled in the art can appreciate how the balloon to catheter joint of the present invention, described in detail above, may also be incorporated in a rapid exchange (RX) catheter. A RX catheter has a guidewire shaft that extends within only the distalmost portion of the catheter. Thus, during a PTCA procedure only the distalmost portion of a RX catheter is tracked over a guidewire.
Outer catheter shaft 106 may be formed of any appropriate polymeric material. In addition, inner shaft 128 may be made of any appropriate polymeric material. Non-exhaustive examples of material for outer catheter shaft 106 and inner shaft 128 include polyethylene, PEBAX, nylon or combinations of any of these, either blended or co-extruded. Preferred materials for shafts 106 and 128 are polyethylene, nylon, PEBAX, or co-extrusions of any of these materials.
Optionally, shafts 106 and 128 or some portion thereof may be formed as a composite having a reinforcement material incorporated within a polymeric body in order to enhance strength, flexibility, and/or toughness. Suitable reinforcement layers include braiding, wire mesh layers, embedded axial wires, embedded helical or circumferential wires, and the like. For example, at least a proximal portion of outer catheter shaft 106 may in some instances be formed from a reinforced polymeric tube. As a further alternative, at least a proximal portion of outer catheter shaft 106 may in some instances be formed from a metal, highly elastic, or super elastic hypotube material.
Balloon 108 can be any appropriate shape or size, and any material which is relatively elastic and deformable. Non-exhaustive examples for balloon 108 include polymers such as polyethylene, PEBAX, PET, nylon, polyurethane.
Now referring to
Preferably, length 652 of balloon 508 is about 0.5 cm to about 4 cm and typically about 2 cm. When bonded to outer catheter shaft 506 in an unexpanded configuration, outer diameter 756 of balloon 508 is generally approximately 0.6 mm to about 0.9 mm along the full length 652 of balloon 508. Wall thickness 758 of balloon 508 is generally approximately 0.035 mm to about 0.05 mm, and inner diameter 754 is thus generally approximately 0.53 mm to about 0.8 mm. When inflated, balloon 508 assumes a torpedo shape having an inflated working outer diameter of about 1 mm to about 5 mm, typically about 3 mm, in order to enlarge the lumen of the affected coronary artery.
Catheter 500 includes outer catheter shaft 506 which includes at least one continuous lumen 614 extending from at or near its proximal end 510 to at or near its distal end 512 in order to provide for balloon inflation. Balloon 508 is located at or near distal end 512 of shaft 506, and a hub 516 is located at or near proximal end 510 of shaft 506. Hub 516 includes a balloon inflation port 518 to allow fluid communication between inflation lumen 614 and balloon 508 so that the balloon 508 may be inflated. Hub 516 will serve in a conventional manner to provide a luer or other fitting in order to connect the catheter 500 to a source of balloon inflation, such as conventional angioplasty activation device.
Similar to the embodiment described above with respect to
Inner shaft 528 and outer catheter shaft 506 may be arranged in various dual lumen configurations. Similar to the embodiment described above with respect to
Other embodiments of balloon catheter 500 may have guidewire lumen 630 and inflation lumen 614 in other dual lumen arrangements, such as a circular guidewire lumen above a D-shaped inflation lumen or a circular guidewire lumen set above a crescent-shaped inflation lumen. For example, similar to the configuration illustrated in
As previously described, the embodiments illustrated in
One skilled in the art can appreciate how the balloon to catheter joint of the present invention, described in detail above, may also be incorporated in a rapid exchange (RX) catheter. A RX catheter has a guidewire shaft that extends within only the distalmost portion of the catheter. Thus, during a PTCA procedure only the distalmost portion of a RX catheter is tracked over a guidewire.
Outer catheter shaft 506 may be formed of any appropriate polymeric material. In addition, inner shaft 528 may be made of any appropriate polymeric material. Non-exhaustive examples of material for outer catheter shaft 506 and inner shaft 528 include polyethylene, PEBAX, nylon or combinations of any of these, either blended or co-extruded. Preferred materials for shafts 506 and 528 are polyethylene, nylon, PEBAX, or co-extrusions of any of these materials.
Optionally, shafts 506 and 528 or some portion thereof may be formed as a composite having a reinforcement material incorporated within a polymeric body in order to enhance strength, flexibility, and/or toughness. Suitable reinforcement layers include braiding, wire mesh layers, embedded axial wires, embedded helical or circumferential wires, and the like. For example, at least a proximal portion of outer catheter shaft 506 may in some instances be formed from a reinforced polymeric tube. As a further alternative, at least a proximal portion of outer catheter shaft 506 may in some instances be formed from a metal, highly elastic, or super elastic hypotube material.
As previously described, balloon 508 with such uniform dimensions as described above is not folded prior to inflation, but is instead expanded to the working diameter from a generally cylindrical or tubular shape. This no-fold aspect of balloon 508 reduces the profile of catheter 500 during insertion, thus resulting in improved crossability and trackability. Once balloon 508 is inflated, balloon 508 assumes a torpedo shape having a working outer diameter of approximately 3 mm in order to enlarge the lumen of the affected coronary artery. Upon deflation, shrinkage of the working outer diameter of the balloon occurs such that balloon 508 may be folded around catheter 500 and catheter 500 may be retracted from the patient.
The process of molding balloons for balloon catheters is generally known in the art. The process generally begins by placing an extruded tubular parison made of a drawable polymer having a specified diameter and wall thickness into the cavity of a mold. The balloon is then heated to a temperature in the range from the second-order transition temperature to the first-order transition temperature of the polymer used. Although the heating temperature will depend on the material, a temperature in the range of about 220-285° F. will generally suffice. While heated, the balloon is pressurized so that it will radially expand. A pressure in the range of about 300-450 psi is generally sufficient. The tubular product may also be axially elongated by stretching before, during, or after being radially expanded. Longitudinally stretching the material at a controlled velocity and distance thins out the material thickness in the balloon to the point where it will radially expand at the temperature and pressure in the balloon. The material of the balloon is thus biaxially oriented. A second process step is often used in balloon forming whereby the balloon inside the mould is exposed to a normalising or stress relieving step. This is usually achieved by applying a specific heat and pressure to the balloon for a fixed time period. Frequently the temperatures and pressures chosen for this process step are different to the heats and pressures used in the initial forming steps described above. This process step is often called a post-heat stage and its purpose is to impart uniformity to the balloons properties and to stabilise the balloon during storage and in further processing. Finally, the balloon is cooled in the mold to a temperature below the second-order transition temperature of the polymer. The completed balloon may then be removed from the mold.
In order to form balloon 508 having no-fold characteristics, the pressure is turned off during the post-heat stage (that is, after the balloon material is stretched both radially and longitudinally) in the balloon forming process to allow the balloon to shrink radially. In the post-heat stage of the manufacturing process, the balloon is in its stressed configuration. By turning off the pressure during this stage, the balloon in its stressed configuration is allowed to shrink radially to obtain an appropriate wingless unexpanded outer diameter.
By eliminating the importance of the neck and taper regions, a simpler mould design can be used to form balloon 508 since the taper and cone regions of the mould do not have to be tightly controlled as is the case with moulds for standard balloon designs. Balloon 508 is preferably formed from cut to length tubing. More specifically,
In the alternative, balloon 508 may be formed by removing or cutting off the neck and taper regions of a torpedo-shaped balloon. In this method of manufacture, balloon 508 may be formed by heat-shrinking a blow-molded torpedo-shaped balloon to shrink the balloon to an appropriate wingless unexpanded outer diameter. Thereafter, the neck and taper regions may be cut off or otherwise removed to form balloon 508 having a uniform wall thickness, a uniform inner diameter, and a uniform outer diameter along its entire length.
Balloon 508 can be formed from any appropriate material which is relatively elastic and deformable. Non-exhaustive examples for balloon 108 include polymers such as polyethylene, PEBAX, PET, nylon, polyurethane, and polyamide. The preferred material for obtaining the no-fold aspect of balloon 508 is elastic, such as polyurethane.
Other advantages associated with balloon 508 having uniform dimensions as described above are ease of manufacture. The manufacturing process is simplified because balloon 508 eliminates the importance of the neck and taper regions during balloon forming.
While various embodiments according to the present invention have been described above, it should be understood that they have been presented by way of illustration and example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents. It will also be understood that each feature of each embodiment discussed herein, and of each reference cited herein, can be used in combination with the features of any other embodiment. All patents and publications discussed herein are incorporated by reference herein in their entirety.
