Patent Application
20070005101
This invention relates to a filter catheter. In particular this invention relates to a filter catheter suitable for rapid exchange over a guidewire.
During advancement of a retrieval catheter through a potentially narrow and/or tortuous vasculature, there is a risk of damage being caused to the vasculature. In addition, a retrieval catheter may be subject to relatively large compressive forces during retrieval of an object, such as an embolic protection filter with a large embolic load, into the catheter. A risk of buckling or kinking of a retrieval catheter may therefore arise during retrieval.
This invention is aimed at providing a filter catheter which addresses at least some of these difficulties.
According to the invention there is provided a filter catheter comprising:—
The tubular reinforcement acts to facilitate push to be transmitted distally without adversely affecting the radial flexibility of the catheter.
In one embodiment of the invention the tubular element extends distally of the guidewire opening. A proximal end of the tubular element may be located adjacent to the guidewire opening and a distal end of the tubular element may be located distally of the guidewire opening. In one case the tubular element terminates proximally of a distal end of the catheter. A distal end of the tubular element may be attached to the catheter shaft. The distal end of the tubular element may be attached to an internal surface of the catheter shaft. At least part of the tubular element may taper distally radially outwardly.
In one embodiment the longitudinal axis of the tubular element is radially aligned with the longitudinal axis of the guidewire opening. The catheter shaft lumen may comprise a guidewire lumen through which a guidewire may be passed for rapid exchange of the catheter over the guidewire. The tubular element lumen may comprise a guidewire lumen through which a guidewire may be passed for rapid exchange of the catheter over the guidewire.
According to the invention there is provided a filter catheter comprising:—
In one embodiment of the invention the catheter shaft has a reception space into which an object may be retrieved. The reinforcement may be substantially elongate. The catheter may comprise a first reinforcement and a second reinforcement.
In one case the catheter shaft proximally of the guidewire opening is relatively stiff to provide the catheter with sufficient column strength and buckle strength during retrieval of an object, such as an embolic protection filter with a large embolic load, into the reception space, and the catheter shaft distally of the guidewire opening is relatively flexible to facilitate advancement of the catheter through a potentially narrow and/or tortuous vasculature without causing damage to the vasculature. The reinforcement acts to reinforce the column strength and buckle strength of the catheter shaft in the region of the guidewire opening to prevent buckling or kinking of the catheter shaft at the transition between the proximal stiff catheter shaft and the distal flexible catheter shaft during retrieval.
In one embodiment the reinforcement extends distally of the guidewire opening. A proximal end of the reinforcement may be located proximally of the guidewire opening and a distal end of the reinforcement may be located distally of the guidewire opening. A proximal end of the reinforcement may be located distally of the guidewire opening and a distal end of the reinforcement may be located further distally of the guidewire opening. The reinforcement may extend distally to a distal end of the catheter. The reinforcement may terminate proximally of a distal end of the catheter.
In another embodiment the catheter shaft has a lumen extending at least partially therethrough, and the reinforcement extends along the catheter shaft within the catheter shaft lumen. By extending the reinforcement within the lumen of the catheter shaft, this arrangement minimises the crossing profile of the retrieval catheter. The catheter shaft lumen may comprise a guidewire lumen through which a guidewire may be passed for rapid exchange of the catheter over the guidewire. The guidewire opening may face in a direction substantially parallel to the longitudinal axis of the catheter shaft. Because the guidewire opening faces parallel to the catheter shaft, the overall crossing profile of the retrieval catheter and the guidewire at the guidewire opening is minimised. The guidewire opening may face in a direction which subtends an acute angle with the longitudinal axis of the catheter shaft. In one case the guidewire opening faces proximally.
In a further embodiment the longitudinal axis of the reinforcement is radially offset from the longitudinal axis of the guidewire opening. The longitudinal axis of the reinforcement may be radially aligned with the longitudinal axis of the guidewire opening. The reinforcement may have a lumen extending therethrough aligned with the guidewire opening. The reinforcement lumen may comprise a guidewire lumen through which a guidewire may be passed for rapid exchange of the catheter over the guidewire. The reinforcement may comprise a guide to guide passage of a guidewire into the reinforcement lumen. The guide may comprise a funnel. In one case the funnel is provided at a distal end of the reinforcement. The reinforcement may comprise a tubular element.
In another embodiment the reinforcement has a small cross sectional area relative to the cross sectional area of the guidewire opening. The reinforcement may comprise a wire element.
In a further embodiment the reinforcement has a cross sectional area substantially equal to the cross sectional area of the guidewire opening.
At least part of the reinforcement may taper distally radially outwardly. At least part of reinforcement may taper distally radially inwardly. The tapering part of the reinforcement may be located adjacent to a distal end of the reinforcement. The tapered part of the reinforcement facilitates ease of attachment of the reinforcement to the catheter shaft.
In one case a distal end of the reinforcement is attached to the catheter shaft. In another case a distal end of the reinforcement is detached from the catheter shaft. A proximal end of the reinforcement may be attached to the catheter shaft.
In one embodiment the stiffness of the reinforcement is greater than the stiffness of the catheter shaft. The second moment of area of the catheter shaft may be greater than the second moment of area of the reinforcement.
The catheter shaft may taper proximally radially inwardly towards the guidewire opening. The catheter may comprise a guide to guide passage of a guidewire through the guidewire opening. The reinforcement may comprise the guide. The guide may be provided by an end face of the reinforcement.
In another embodiment the catheter shaft has a substantially uniform outer diameter from the guidewire opening to a distal end of the catheter shaft. The outer diameter of the catheter shaft may vary along the length of the catheter between the guidewire opening and the distal end of the catheter shaft. The catheter shaft may have a reduced diameter portion. The reduced diameter portion may extend longitudinally for a part of the distance between the guidewire opening and the distal end of the catheter shaft. The reduced diameter portion may extend longitudinally for substantially the full distance between the guidewire opening and the distal end of the catheter shaft.
In one case the invention provides a filter retrieval catheter. In another case the invention provides a filter delivery catheter.
The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:—
FIGS. 2(a) and 2(b) are partially cross-sectional, side views of the filter catheter of
FIGS. 2(c) and 2(d) are views similar to
FIGS. 3 to 6 are cross-sectional, side views of other filter catheters according to the invention;
FIGS. 8 to 13 are cross-sectional, side views of other filter catheters according to the invention;
Referring to the drawings, and initially to FIGS. 1 to 2(b) thereof, there is illustrated a filter retrieval catheter according to the invention, which is suitable for retrieving an embolic protection filter 50 from a vasculature. The catheter is particularly suitable for retrieving the type of embolic protection filters described in International patent applications published under numbers WO 01/80777, and WO 03/055412, the relevant contents of which are incorporated herein by reference.
The catheter comprises a catheter shaft 2 having a guidewire opening 4 in a sidewall of the catheter shaft 2. The guidewire opening 4 is a rapid exchange guidewire opening and is located a substantial distance distally of a proximal end of the catheter shaft 2 to facilitate rapid exchange of the catheter over a guidewire 5. In this case, the guidewire opening 4 is located approximately 30 cm from a distal end 1 of the catheter shaft 2.
The guidewire opening 4 faces proximally and is aligned for passage of the guidewire 5 out through the opening 4 in a direction which subtends an acute angle with the longitudinal axis of the catheter shaft 2 (
Distally of the guidewire opening 4, the catheter shaft 2 has a guidewire lumen extending from the guidewire opening 4 to the distal end 1 of the catheter shaft 2. The catheter shaft 2 has an open mouth at the distal end 1, and the guidewire lumen is in communication with the open mouth and with the guidewire opening 4. In this manner, a guidewire 5 may be passed through the open mouth into the guidewire lumen, through the guidewire lumen and out through the guidewire opening 4 for rapid exchange of the catheter over the guidewire 5.
The guidewire lumen acts as a reception space to enable an embolic protection filter 50 to be retrieved from a vasculature into the guidewire lumen through the open mouth.
Proximally of the guidewire opening 4, the catheter shaft 2 is of a relatively stiff material to ensure that the catheter has sufficient column strength and buckle strength to enable an embolic protection filter 50 to be retrieved into the catheter. Retrieval of the embolic protection filter 50 may involve relatively large forces being exerted on the catheter shaft 2 as the filter 50 with a potentially large embolic load is collapsed and retrieved through the open mouth and into the guidewire lumen (FIGS. 2(a) and 2(b)).
The distal end 1 of the catheter shaft 2 preferably has an expansile tip to accommodate retrieval of a potentially large embolic filter into the catheter shaft 2, as illustrated in
Distally of the guidewire opening 4, the catheter shaft 2 is of a relatively flexible material to ensure that the catheter is sufficiently trackable and flexible to prevent damage being caused during advancement of the catheter through a potentially narrow and/or tortuous vasculature.
To prevent buckling or kinking of the catheter shaft 2 in the region of the guidewire opening 4 during retrieval of the embolic protection filter 50, the catheter comprises two elongate reinforcement elements 6, 3 extending along the catheter shaft 2 within the guidewire lumen. The reinforcements 6, 3 have respective stiffnesses greater than the stiffness of the catheter shaft 2, and respective second moments of area less than the second moment of area of the catheter shaft 2. This arrangement results in the reinforcements 6, 3 acting to reinforce the column strength and buckle strength of the catheter shaft 2 in the region of the guidewire opening 4 during retrieval. The reinforcements provide a linear transition in stiffness. The inner tube 3 is made from a higher stiffness (E) polymer to provide additional compression resistance during retrieval. Even though the inner tube 3 has a high material modulus (E), its smaller outer and inner diameters means that the 2nd moment of Area (I) value for the inner tube 3 is lower than for the outer tube 2.
The combined EI value for the outer tube 2—inner tube 3 construction is lower than for a single tube made from the same material.
The first reinforcement element 6 comprises an elongate wire element extending from a proximal end located proximally of the guidewire opening 4 to a distal end located distally of the guidewire opening 4. The wire 6 extends through a wire lumen in the catheter shaft 2 proximally of the guidewire opening 4, exits the wire lumen distally of the guidewire opening 4 at a lumen outlet, and extends through the guidewire lumen to the distal end of the wire 6. The proximal end of the wire 6 is fixedly attached to the interior surface of the catheter shaft 2, for example by means of welding.
As illustrated in
A polymer jacket 7, for example of polyethylene, is provided around the wire 6 and extending along the wire 6.
At a distal region 6a, the wire 6 tapers distally radially inwardly (
The second reinforcement element 3 comprises an elongate tubular element extending from a proximal end located adjacent to and distally of the guidewire opening 4 to a distal end 9 located further distally of the guidewire opening 4. In this case, the distance between the proximal end and the distal end 9 is approximately 15 cm. The longitudinal axis of the tube 3 is aligned with the longitudinal axis of the guidewire opening 4. As illustrated in
The tube 3 has a guidewire lumen extending therethrough. The proximal end of the guidewire lumen is aligned with and is in communication with the guidewire opening 4, and the distal end of the guidewire lumen is aligned with and is in communication with the guidewire lumen of the catheter shaft 2. In this manner, a guidewire 5 may be passed from the guidewire lumen of the catheter shaft 2 through the guidewire lumen of the tube 3, and out through the guidewire opening 4 for rapid exchange of the catheter over the guidewire 5.
The tube 3 tapers distally radially outwardly adjacent to the distal end 9. This tapered part 9 of the tube 3 is fixedly attached to the interior surface of the catheter shaft 2, for example by means of a weld joint 10, and the proximal end of the tube 3 is also fixedly attached to the interior surface of the catheter shaft 2. The inner tube 3 is preferably welded to the outer tube 2 at both the flared section 9 and at the RX exit port 4.
The flare on the distal end 9 of the inner tube 3 provides a weld zone to the interior surface of the outer tube 2 and a guiding face to direct the guidewire 5 through the RX port 4 during back loading of the catheter.
The inner tube 3 and the outer tube 2 are welded to the polymer jacket 7 of the proximal shaft wire 6 along a welding region 8 (
It will be appreciated that other means of attachment may be employed in addition to or as an alternative to welding.
As illustrated in
The inner tube 3 acts to reinforce the catheter shaft 2 to minimise the possibility of buckling or kinking of the catheter shaft 2 during retrieval. The inner tube 3 also acts as a guide to guide passage of the guidewire 5 from the guidewire lumen of the catheter shaft 2 out through the rapid exchange guidewire opening 4.
The tapered distal end 9 of the inner tube 3 provides a convenient means of attaching the inner tube 3 to the outer tube 2. The tapered distal end 9 also assists in guiding the guidewire 5 into the inner tube 3 in the means of a funnel.
The use of a different material on the inner tube 3 allows the use of a material with a lower coefficient of friction to reduce wire movement forces.
As illustrated in FIGS. 2(c) and 2(d), the wire 6 may extend distally into the attachment region 10, and the distal end of the wire 6 may be fixedly attached to the inner tube 3 and the catheter shaft 2 at the attachment region 10, for example by means of a weld joint.
The distance 11 between the distal end 9 of the inner tube 3 and the distal end 1 of the catheter shaft 2 may be varied to vary the degree of reinforcement provided, as illustrated in
The distal region 17 of the wire 6 may remain untapered, as illustrated in
In the retrieval catheter of
The retrieval catheter of
In the retrieval catheter of
The outer shaft 2 may terminate just proximally of the guidewire opening 4 (
The retrieval catheter of
The hinge region 13 may be of a different material to the remainder of the catheter shaft 2, for example of a more compliant material (
In the retrieval catheter of
By providing this reduced diameter portion 13, the bending/trackability characteristics of the retrieval catheter are enhanced while retaining sufficient compressive strength/pushability. This aspect of the invention is explored in further detail as follows. Reducing the diameter of a shaft has a greater impact on the bending stiffness of the shaft compared to its impact on compression resistance. This is because the shaft bending stiffness is related to the EI value where I has a quadratic relationship to the inner and outer radius of the shaft. The compression resistance is related to EA where A is the cross sectional area, which is related to the square of the inner and outer radius. Therefore, by reducing the shaft diameter it is possible to reduce bending stiffness, but maintain compression resistance by increasing the modulus of the shaft material to maintain the overall EA product.
The distal tip 1 retains the larger diameter to facilitate reception of the embolic protection filter 50 into the tip 1. Also the catheter shaft 2 in the region of the guidewire opening 4 retains the larger diameter to facilitate passage of the guidewire 5 through the guidewire opening 4.
In the case of the retrieval catheter of
It will be appreciated that the reduced diameter portion 13 may alternatively extend longitudinally along the catheter shaft 2 for a relatively large distance. For example in the retrieval catheter of
In the retrieval catheter of
The retrieval catheter of
In further detail, the catheter shaft 2 provides reinforcement to the inner tube 3, in particular in the region of the guidewire opening 4. As illustrated in
The retrieval catheter of
A further advantage of having a reduced diameter portion with the retrieval catheter of the invention is illustrated with respect to
The retrieval catheter of
It will be appreciated that the first reinforcement element 6 may be manufactured using a variety of different materials. For example the element 6 may be a wire, or a hard durometer polymer. Any material which achieves the desired properties of pushability may be employed.
The jacket 7 may be attached to the reinforcement element 6 in a variety of different ways. For example welding, or extruding may be employed.
The use of a small diameter inner tube 3 means that the distal shaft is more constrained around the tensioned guidewire 5 during retrieval of an embolic load. It is thus less likely to snake or concertina under compression load.
The smaller inner tube 3 helps to prevent a kink in the proximal section of the outer tube 2 inhibiting wire movements through the catheter.
In
By profiling the inner tube geometry, the catheter can achieve zones of varying stiffness without changes in outer profile.
The filter catheters described previously with reference to the drawings may be employed as filter retrieval catheters. In alternative embodiments, the filter catheters may be employed as filter delivery catheters.
The invention is not limited to the embodiments hereinbefore described, with reference to the accompanying drawings, which may be varied in construction and detail.
This application claims the benefit of U.S. Patent Application Ser. No. 60/672,431, filed Apr. 18, 2005, the entire teachings of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60672431 | Apr 2005 | US |
