Patent Application
20120010692
1. Field of the Invention
This invention relates to medical devices and, in particular, to delivery systems for placement of a prosthesis in a body lumen.
2. Description of Related Art
Endoluminal prostheses, such as stents and stent grafts, are used for treating damaged or diseased body lumens such as the esophagus, bile duct, and blood vessels. For example, endoluminal prostheses may be used for repairing the diseased aorta including abdominal aortic aneurysms, thoracic aortic aneurysms, and other such aneurysms. The prosthesis is placed inside the body lumen and provides some or all of the functionality of the original, healthy vessel.
The deployment of endoluminal prostheses into the lumen of a patient from a remote location by the use of a catheter delivery and deployment device is well known in the art. For example, PCT Publication No. WO 98/53761 entitled “A Prosthesis and a Method and Means of Deploying a Prosthesis,” which is incorporated herein by reference, proposes a delivery and deployment system for an endoluminal prosthesis. The prosthesis is radially compressed onto a delivery catheter and is covered by an outer sheath. To deploy the system, the operator slides the outer sheath over the delivery catheter, thereby exposing the prosthesis. The prosthesis expands outwardly upon removal of the sheath. Such a delivery and deployment device has been referred to as a “push-pull” system because as the operator pulls the sheath proximally in relation to the delivery catheter, the delivery catheter “pushes” the prosthesis out of the sheath.
With some catheter delivery and deployment devices, the force required to withdraw the sheath may be relatively high. The withdrawal force is a function of various factors including, for example, frictional resistance caused by the sliding engagement between components of the system such as the outer sheath, the delivery catheter, the prosthesis, and a hemostatic valve assembly. A delivery and deployment device may require as much as 100 Newtons or approximately 22.5 pounds of force to deploy. This force is typically provided by the physician performing the procedure. Such high force may tire an operator or result in inaccurate placement of the medical device.
Medical device deployment systems are described which may reduce the amount of force required to deploy a medical device within a body lumen or cavity. The embodiments may include any of the following aspects in various combinations and may also include any other aspect described below in the written description or in the attached drawings.
In one aspect, the delivery system may include a sheath having a lumen extending along a central axis thereof, a catheter slideably disposed within the lumen, a hemostatic device comprising a housing disposed around and sealingly engaged with the sheath, with the housing including a first seal, and a sleeve slideably coupled to the catheter. The sleeve includes a second seal that is sealingly engaged the catheter. The sleeve is movable between a first position in which the sleeve is disposed outside of the housing and the first seal is sealingly engaged with an outer surface of the catheter, and a second position in which at least a portion of the sleeve is disposed within the housing between an inner surface of the housing and the outer surface of the catheter. In the second position, the first seal is sealingly engaged with an outer surface of the sleeve and the second seal is sealingly engaged with the outer surface of the catheter. When the sleeve is in the first position the first seal exerts a first sealing force on the catheter that effects a first frictional resistance between the hemostatic device and the catheter. When the sleeve is in the second position the second seal of the sleeve exerts a second sealing force on the catheter that effects a second frictional resistance between the hemostatic device and the catheter. The second frictional resistance is less than the first frictional resistance, thereby reducing a force necessary to effect relative movement between the sheath and the catheter.
In another aspect, the delivery device may also include an expandable prosthesis disposed on a distal portion of the delivery catheter and within the lumen of the sheath.
A method of reducing a force necessary to effect movement between a sheath an a catheter to which the sheath is sealingly engaged may include: providing a delivery device comprising a sheath having a lumen extending along a central axis thereof, a catheter slideably disposed within the lumen, a hemostatic device comprising a housing disposed around and sealingly engaged with the sheath, where the housing comprising a first seal that exerts a first sealing force against an external surface of the catheter that effects a first frictional resistance to relative movement between the catheter and the housing; and advancing a sleeve over the catheter and through the first seal of the housing, whereby the first seal is decoupled from the catheter and sealingly engages an outer surface of the sleeve, such that the sleeve at least partially isolates the catheter from the first sealing force, wherein the sleeve comprises a second seal that applies a second sealing force against the external surface of the catheter that effects a second frictional resistance to relative movement between the catheter and the housing. The second frictional resistance is less than the first frictional resistance, thereby reducing the force necessary to effect relative movement between the catheter and the sheath.
The foregoing paragraphs have been provided by way of general introduction, and are not intended to limit the scope of the following claims. The described embodiments will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.
The embodiments may be more fully understood by reading the following description in conjunction with the drawings, in which:
a) is a cross-sectional view of a seal of the hemostatic device of
b) is a perspective view of the seal of
c) is a cross-sectional view of a seal of the hemostatic device of
d) is a perspective view of the seal of
a) is a plan view of a deployment assist device;
b) is a cross-sectional view of the deployment assist device of
a) is a cross-sectional view of the seal of the hemostatic device of
b) is a cross-sectional view of the delivery system taken along the line Z-Z;
a) is a plan view of another embodiment of the deployment assist device; and
b) is a cross-sectional view of the deployment assist device of
Throughout this specification, the terms “distal” and “distally” refer to a position, direction, or orientation that is generally away from the patient. Accordingly, the terms “proximal” and “proximally” refer to a position, direction, or orientation that is generally toward the patient.
Referring now to the figures,
A dilator head 13 is disposed at the distal end of the delivery catheter. The dilator head 13 is tapered in the distal direction to provide for a smooth, atraumatic transition from a guide wire over which the delivery system is advanced into a body lumen or cavity. A guidewire lumen 15 extends longitudinally through the delivery catheter 10 between the proximal and distal ends. The delivery catheter 10 is configured to receive a guidewire 17 via the guidewire lumen 15 as shown in
The release portion 18 of the delivery catheter 10 is disposed generally proximally of the prosthesis 20. The release portion 18 can be manipulated, along with the sheath 12, to selectively deliver and deploy the prosthesis 20 in the body lumen. As shown in
The sheath 12 includes an elongate tubular body having a wall thickness and a proximal and distal end. An inner surface of sheath 12 defines a lumen 14 extending along a longitudinal axis thereof. The lumen 14 may have a generally constant diameter along its length. The sheath 12 extends proximally from the delivery section 2 to the user manipulation section 3. The delivery catheter 10 is slideably disposed within the lumen 14. The sheath 12 may slideably cover and restrain the prosthesis 20 onto the catheter 22 in a radially compressed configuration in which the diameter of the prosthesis 20 is reduced as compared to its unrestrained state. The dilator head 13 may have a recessed portion disposed at its proximal end that is shaped to receive the distal end of the sheath 12 and form a generally smooth transition therebetween so as to prevent trauma to the body lumen or cavity as the delivery catheter 10 is advanced into the patient for delivery and deployment. The proximal end of the sheath 12 may be configured to remain outside of the body during the procedure, in which case the sheath 12 may be directly manipulated by the operator to deploy the prosthesis 20.
The sheath 12 may have a length, as shown in
The sheath may be made of any suitable biocompatible material, for example PTFE, nylon, or polyethylene. The sheath may optionally include a flat wire coil to provide the sheath with increased pushability and kink-resistance as the sheath is advanced through the body lumen or cavity, as discussed in U.S. Pat. No. 5,380,304 and U.S. Published Patent Application No. 2001/0034514 A1, which are incorporated herein by reference in their entirety.
As shown in
The stents 32 may cover and/or may be at least partially covered by a graft material. Various graft materials and configurations may be used. Suitable graft configurations include, but are not limited to films, coatings, sheets of biocompatible fabrics, non-woven materials and porous materials. Examples of suitable graft materials include polyesters, such as poly(ethylene terephthalate), polylactide, polyglycolide and copolymers thereof; fluorinated polymers, such as polytetrafluoroethylene (PTFE), expanded PTFE and poly(vinylidene fluoride); polysiloxanes, including polydimethyl siloxane; polyurethanes, including polyetherurethanes, polyurethane ureas, polyetherurethane ureas, polyurethanes containing carbonate linkages and polyurethanes containing siloxane segments, and bioremodelable materials, such as small intestine submucosa (“SIS”).
As set forth above, the prosthesis 20 may be retained in a radially reduced configuration between the delivery catheter 10 and the sheath 12. The sheath 12 is slideably disposed over the prosthesis 20 and the delivery catheter 10 such that the sheath 12 is movable in a proximal and a distal direction. In operation, the sheath 12 is withdrawn in the proximal direction by sliding the sheath 12 with respect to the delivery catheter 10 and the prosthesis 20 to expose the prosthesis 20. While the sheath 12 is withdrawn proximally, the operator applies pressure to the delivery catheter 10 in the distal direction via the catheter 24. As the catheter 24 is advanced the abutment surface 23 contacts the proximal end of the prosthesis 20 and pushes the prosthesis 20 in the distal direction while the sheath 12 slides proximally in relation thereto. As the sheath 12 slides proximally, the catheter 24 pushes the prosthesis 20 distally from the receiving portion 16 and into the body lumen or cavity.
The delivery and deployment device 1 may also include proximal and distal deployment control mechanisms 39, 40 as shown in
The delivery and deployment device 1 may further include a hemostatic valve assembly 19, as shown in
The valve 28 may include, for example, one or more check valves and/or one or more “iris”-type valves. In one embodiment, the valve 28 is comprised of one or more elastic sealing disks, for example three elastic sealing disks. Suitable check valves include CHECK-FLO® valves. Suitable valve assemblies include the CAPTOR® Hemostatic Valve, which are available from Cook Incorporated, Bloomington, Ind., USA, the assignee of the present application. Other suitable valves and valve assemblies are described in the patent literature, for example, in U.S. Pat. Nos. 4,430,081, entitled “Hemostasis Sheath,” 5,006,113, entitled “Hemostasis Cannula,” 5,267,966, entitled “Hemostasis Cannula and Method of Making a Valve for Same,” 6,416,499, entitled “Medical Fluid Flow Control Valve,” 6,663,599, entitled “Hemostasis Cannula,” and 7,172,580, entitled “Hemostatic Valve Assembly.” Each of the foregoing patents is herein incorporated by reference.
A primary function of the valve assembly 19 is controlling and limiting blood loss during a procedure. Accordingly, the valve 28 forms a tight sealing engagement with the catheter 24. A tight seal may be provided, for example, by providing sufficient area of surface contact between the valve 28 and the catheter 24 and by providing sufficient pressure exerted by the valve against the catheter. As shown in
In general, as the quality of the seal improves, the friction between the sheath 12 and the delivery catheter 10 increases, thereby increasing the force required to slide the valve assembly 19 and the attached sheath 12 over the delivery catheter 10. That is, as the inward, compressive force exerted by the valve 28 on the outer surface of the catheter 24 increases, the seal quality also increases. However, the higher the inward, compressive force exerted on the catheter 24 by the valve 28, the higher the frictional force, and therefore the frictional resistance to movement between the catheter 24 and the valve 28. Because the valve assembly 19 is connected to the proximal end of the sheath 12, the valve assembly 19 must be moved in order to effect relative movement between the sheath 12 and the catheter 24. Thus, the frictional resistance between the valve 28 and the catheter 24 may constitute a significant component of the sheath withdrawal force necessary to effect relative movement between the sheath 12 and the catheter 24 and to deploy the prosthesis 20.
However, as discussed above, the valve 28 of the valve assembly 19 is typically configured to provide an adequate sealing force for relatively small diameter components or devices to be inserted therethrough, for example, a guidewire, as well as comparatively large diameter components/devices, such as the catheter 24. Thus, the valve 28 typically exerts a higher force on the catheter 24 than is necessary for normal sealing purposes. Stated differently, the aperture 50 in the valve 28 must be sufficiently small in order to provide an adequate sealing force against a small diameter component, such as a guide wire. Thus, when a larger diameter component, such as the catheter 24, is advanced through the valve 28, the aperture must stretch to accommodate the larger diameter. However, this stretching of the aperture 50 results in a correspondingly higher compressive force on the catheter 24. Assuming the necessary sealing force at the valve/catheter interface is essentially the same as the valve/guidewire interface, it is clear that the higher compressive force exerted on the larger diameter catheter 24 by the valve 28 is higher than the minimum force that is necessary to provide adequate sealing therebetween. This unnecessarily high compressive sealing force results in an unnecessarily high frictional force between the catheter and the sheath 12 via the attached valve assembly 19.
As set forth above, the sheath withdrawal force is typically provided by the operator (e.g. a physician). Thus, as the required sheath withdrawal force increases, it becomes increasingly difficult for the operator to release the prosthesis 20. If the required sheath withdrawal force is too high, it may tire the operator or force the operator to strain and cause sudden or unexpected withdrawal of the sheath 12, thereby causing inaccurate placement of the prosthesis 20. Further, as the sheath withdrawal force increases, it may cause the catheter 24 and/or the prosthesis 20 to compress slightly in the longitudinal or axial direction. This compression cause energy to be stored in the catheter 24 and the prosthesis 20. When the sheath 12 is withdrawn, the stored energy is suddenly released, which may cause the prosthesis 20 to “jump” in the distal direction as it expands, thereby resulting in inaccurate placement. Accordingly, reducing the frictional force between the catheter 24 and the valve 28 of the valve assembly 19 while maintaining adequate sealing force therebetween may be desirable.
a) and (b) illustrate an embodiment of a deployment assist device 100. The deployment assist device 100 includes a sleeve 120 having a tapered distal end 122 that extends from the outer diameter 124 to the diameter of a lumen 126 defined by an inner surface of the sleeve 120. The lumen 126 may have a constant diameter that substantially approximates the outer diameter of the catheter 124. In other embodiments, such as the one depicted in
As shown in
The sleeve 120 may have a constant outer diameter 124, or may vary in diameter along its length. The sleeve 120 may have a housing 134 disposed around a proximal end thereof, as shown in
In another embodiment, shown in
The sleeve 120 and the housing 134 may be formed from a lubricious material, for example and without limitation, polytetrafluoroethylene or PTFE (Teflon) to minimize friction between the sleeve 12 and the catheter 24 at any point(s) of contact therebetween.
In operation, the deployment assist device 100 is advanced over the catheter 24 in the distal direction to the valve assembly 19. Initially, the tapered end 122 of the sleeve 120 contacts the proximal most portion of the valve 28 and facilitates expansion of the aperture 50 as the deployment assist device 100 is advanced through the valve 28 and into the housing 25. The deployment assist device 100 may then be detachably or fixedly coupled to the valve assembly 19. This coupling may be accomplished by advancing the deployment assist device 100 until the interlocking mechanism 140 contacts and engages with a lip or the like disposed on the valve housing 29 in a snap-fit arrangement, as shown in
As shown in
Because the aperture of the valve 28 must be stretched to an even wider diameter 56 to accommodate the sleeve 120, the sealing force exerted by the valve 28 of the valve assembly 19 may be significantly higher on the sleeve 120 than the normal sealing force exerted on the catheter 24 at the diameter 54 when no deployment assist device 100 is present. Thus, the sealing force exerted on the sleeve 120 by the valve 28 will typically result in a frictional force that is greater than the 50-60 Newtons exerted on the inner catheter 24. The sleeve 120 may be formed from materials having sufficient rigidity to maintain patency of the lumen 126 even when exposed to this increased compressive sealing force applied by the valve 28. Thus, even in embodiments having a constant diameter lumen 126, the deployment assist device 100 may effectively isolate the catheter 24 from the high sealing force exerted by the valve 28 on the sleeve 120. Accordingly, the catheter 24 is only exposed to the sealing force of the seal(s) 132 of the deployment assist device 100. This sealing force is significantly lower than the sealing force exerted by the valve 28 on the catheter 24 when the deployment assist device 100 is not present, and accordingly is also lower than the sealing force exerted by the valve 28 when the deployment assist device 100 is present. For example, the sealing force exerted on the catheter 24 by the seal(s) 132 results in a withdrawal (frictional force) of 25-35 Newtons. In other embodiments, the sheath may partially or substantially shield or isolate the catheter 24 from the high sealing force exerted by the valve 28 on the sleeve 120, resulting in a somewhat lower reduction of the force necessary to withdraw the sheath 12 relative to the catheter 24.
In either case, because the primary component of the frictional force is the normal force exerted on the catheter 24 by the seals 132, the frictional force between the seal(s) 132 of the deployment assist device 100 and the catheter 24 is much lower than the frictional force between the valve 28 and the outer surface of the sleeve 120. Thus, the force necessary to effect movement between the valve assembly 19, and hence the sheath 12, relative to the catheter 24 is significantly reduced as compared to a delivery system without the deployment assist device 100. For example, the sheath withdrawal force may be reduced by about 10% to about 50% of the normal sheath withdrawal force, and in one embodiment, the sheath withdrawal force is reduced by about 25%. In some instances, the deployment assist device 100 may lower the sheath withdrawal force by about 25 Newtons. The amount of reduction in sheath withdrawal force may be influenced by a number of factors, including, for example and without limitation, the materials used to form the sleeve 120 (which affects properties such as rigidity under compression and the like), the valve 28 and the seals 132. Additionally, the size differentials between the aperture 50 of the valve 28, the catheter 24 and the deployment assist device 100 may also influence the amount of reduction in sheath withdrawal force.
Once the sheath 12 has been withdrawn and the prosthesis 20 has been deployed, the inner catheter and other components disposed within the sheath 12 are typically withdrawn through the sheath and the hemostatic valve assembly 19 in the proximal direction to allow the insertion of additional delivery systems or other tools through the valve assembly 19 and the sheath 12. However, when doing so, it is necessary to also remove the deployment assist device 100 in order to maintain the hemostatic seal between the valve assembly 19 and the guidewire 17 once the inner catheter and other larger components have been removed. The deployment assist device 100 may be decoupled from the valve housing 29 or the housing 25 by withdrawing the catheter 24 in the proximal direction while holding the valve assembly 19 and the sheath 12 steady. That is, following deployment of the prosthesis 20, the operator withdraws the catheter 24 relative to the sheath until a step 150 that extends radially outward from the surface of the catheter 24, contacts the distal tapered end 122 of the deployment assist device 100 and causes the interlocking mechanism 140 to become decoupled from the valve housing 29, thus releasing and removing the deployment assist device 100 from the valve assembly 19. In this way, the valve assembly 19 is able to maintain sufficient sealing force and prevent leak paths even after the inner catheter assembly has been removed from the delivery system. In another embodiment, the proximal end of the dilator head 13 may be sized large enough to contact be distal tapered end 122 of the deployment assist device 100 and decouple the deployment assist device 100 from the valve assembly 19 as the inner catheter 24 is withdrawn.
While preferred embodiments have been described, it should be understood that the invention is not so limited, and modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein. Furthermore, the features described above are not necessarily the only features of the invention, and it is not necessarily expected that all of the described features will be achieved with every embodiment of the invention.
