WO1998022044A1

WO1998022044A1 - Device and method for mounting an endovascular stent onto a balloon catheter

Info

Publication number: WO1998022044A1
Application number: PCT/IB1997/001459
Authority: WO
Inventors: Enzo Borghi
Original assignee: Bard Galway Limited
Priority date: 1996-11-20
Filing date: 1997-11-18
Publication date: 1998-05-28
Also published as: AU4880697A; ITBO960597A0; ITBO960597A1; IT1286780B1

Abstract

An endovascular stent (2) is fitted to a balloon catheter (3) by means of a device (1) that comprises an elongated sheath (50) with at least two component parts (51, 52). The sheath (50) is defined by a number of linear fingers (4a, 4b) arranged in tubular formation and serving to create a longitudinal space (5) receptive to the distal end of the catheter; the fingers are anchored rigidly at one end (4a', 4b'), the opposite ends (4a'', 4b'') projecting freely in such a way as to fashion a splayed entry (7) through which the catheter (3) can be inserted into the space. The two parts (51, 52) are associated with respective independently embodied first and second supports (6a, 6b) capable of movement one relative to another along a common axis (2a) in such a way that the respective linear elements (4a, 4b) are retractable independently from their positions within the stent (2), inserted end to end as a means both of support and of guidance along which the stent is advanced and in the process expanded from a radially compact initial configuration to a circumferentially enlarged final configuration ready for transfer to the catheter (3), around which it will contract ultimately in a stable coaxial fit.

Description

DESCRIPTION

DEVICE AND METHOD FOR MOUNTING AN ENDOVASCULAR STENT ONTO A BALLOON CATHETER

Technical Field

The invention relates to devices and techniques for mounting an endovascular stent onto the balloon of a delivery catheter to enable the catheter to deliver and deploy the stent in a body lumen such as a coronary or peripheral blood vessel. The invention may be used in connection with techniques in which diseased or traumatized blood vessels are dilated and a stent is placed in the vessel to restore and maintain the natural patency of the vessel.

Background of the Invention

Among the techniques for placing an endovascular stent has been to mount the stent onto a folded balloon of a balloon catheter and then insert and advance the stent and catheter together into the body lumen to locate the stent at the intended site of implantation. When the stent is correctly positioned, the balloon then is inflated to expand the stent into engagement with the vessel wall to support the vessel wall.

The stent may be placed onto the balloon of the catheter manually or with the aid of devices or tools. Among the devices that may be used to place a stent on a balloon is that disclosed in Italian patent application B095A000430 filed September 13, 1995 and International application

PCT/IB96/00918 filed September 10, 1996 (International publication no. WO97/09946), the disclosures of which are incorporated in their entireties. The device described in those applications includes a loading device that comprises a longitudinal sheath having an opening into which the balloon is inserted. The stent is supported slidably along the outside of the sheath so that it can be slid along the sheath into a position coaxially about the balloon. The stent then is released into stable and secure engagement with the balloon by withdrawing the sheath from between the stent and the balloon. The sheath may comprise a number of relatively flat elongate fingers attached at one end to a support, with the fingers being arranged to define a space of substantially conical shape receptive to the balloon. The free ends of the fingers define an entrance through which the catheter can be advanced into the sheath. The device also includes a stylet anchored rigidly in the support adapted to be inserted into the lumen of the balloon catheter to aid in directing the catheter slidably along the stylet into the spaced defined by the sheath. So inserted, the balloon is located coaxially within the sheath-defining fingers. The device may be provided in a preassembled form in which the stent is premounted on and is supported by the sheath-defining fingers. So mounted, the fingers pass through the sheath and define an initial minimal radial configuration.

When the device is used, the stent, which may be elastically deformed, is forced manually onto the fingers toward the free ends. The fingers, having an inherent resilience, cause the stent to expand somewhat circumferentially, the splayed, divergent configuration of the fingers facilitating such elastic deformation of the stent. As described in the aforesaid applications, after the stent has been shifted beyond the ends of the fingers and is no longer restrained, the stent returns elastically to its contracted configuration, tightening about the balloon of the catheter.

Although the foregoing device performs satisfactorily with standard length stents, that is stents shorter than about 22 to 23 millimeters, the use of the device with longer stents, such as those more than 22 to 23 millimeters in length, may present some difficulties, such as the additional friction that can be expected when sliding a longer length stent along the sheath-defining fingers of the device. Where correct positioning of the stent on the catheter necessarily involves manual dexterity of the physician and where certain clinical situations may present difficult operating conditions, it would be desirable to enhance the ease with which a long (e.g., greater than 22-23 millimeters in length) stent can be mounted onto the balloon. It is desirable, therefore, to reduce the frictional resistance so that a physician, typically wearing surgical gloves, will be able to grip the stent and apply sufficient pressure to control the sliding movement of the stent off of the sheath. Should considerable frictional resistance be presented, there would be additional risk that the stent might not be positioned correctly or that it could slide off of the balloon, rubbing against the balloon and presenting further risk that the stent might be rendered useless and the integrity of the balloon also compromised.

It is among the objects of the invention to provide a device and method for loading a stent onto a delivery catheter in a manner that frictional resistance to sliding movement of the stent along the sheath is reduced and may be used with stents of any practical length.

Disclosure of the Invention

The objects of the invention are achieved with a device in which the sheath is formed from component parts movable longitudinally relative to each other in a manner as to allow their separation from the stent independently before the stent is transferred to the catheter. By separating component parts of the sheath, the resistance to sliding of the stent from the remaining portions of the sheath onto the catheter is reduced. In particular, the relative movement of the component parts is achieved with a control means that is grippable and operable with ease with one hand.

Description of the Drawings

The invention will be appreciated more fully from the following example, with the aid of the accompanying drawings in which:

FIG. 1 is an illustration of the device embodying the present invention arranged in a configuration in which the stent has been advanced to the distal ends of the fingers and has been expanded slightly and elastically, in readiness to be transferred onto a catheter;

FIG. 2 is an overall view of the device as shown in FIG. 1 , illustrating the configuration of its components during the transference of the stent from the device onto the catheter; and

FIG. 3 is a fragmented, partly sectional illustration of the portion of the device denoted as A in FIG. 1 , in a view rotated through 90° in relation to FIG. 1 and with certain types omitted for ease of illustration.

Description of the Illustrative Embodiment

As shown in FIGS. 1 and 2, the loading device, indicated generally at 1 is provided for loading a stent 2 onto a catheter 3. In the following description, the term "distal" will refer to a direction that is toward the patient and the term "proximal" will refer to a direction along the axis 2a of the device that is away from the patient, e.g., toward the physician. Thus, the end of the catheter onto which the stent is loaded may be considered as the distal end of the catheter and the end of the catheter that remains outside of the patient and is operated by the physician is the proximal end of the catheter. The catheter is provided with an inflatable balloon that is initially folded and wrapped around the shaft of the catheter. The stent 2, mounted on the balloon, can be delivered to and expanded within a blood vessel. The device 1 includes a guiding stylet 21 by which the catheter shaft can be guided into the device, as described below. As shown also in FIG. 3, the device may be considered to comprise an elongate flexible sheath 50 defined by four elongate flexible fingers including two pairs of fingers 4a, 4b. The sheath 50 is constructed to include two component parts 51 , 52 that are movable longitudinally with respect to each other, as described below. One of the component parts 51 includes one pair of fingers 4a and the other component part 52 includes the other pair of fingers 4b. The stylet 21 is attached to the part 52 and extends proximally through the space 5 within the sheath. One pair of fingers 4a is anchored, at its distal ends 4a', to an independent support 6a and the distal ends 4b' of the other pair of fingers 4b is anchored to an independent support 6b. The pairs of fingers 4a, 4b cooperate to define a space 5 within the sheath-defining fingers. The free, proximal ends 4a" and 4b" of the fingers 4a, 4b are arranged to define an open end 7 through which the balloon can be inserted into the space 5.

The supports 6a and 6b may be cylindrical in shape and are assembled coaxially for relative linear movement along a common axis 2a.

The supports 6a, 6b cooperate to prevent relative rotation about the axis 2a. To that end, the first support 6a may be formed to include a pair of longitudinally extending, laterally opposed slots 20 that receive the ends of a cylindrical pin 8 that is attached to the second support 6b and projects into the slots 20. The pin 8 serves as a rotating stop to cooperate with the slots

20 to prevent relative rotation about axis 2a.

The supports 6a, 6b can be moved relative to each other along the common axis 2a by a control arrangement including grippable elements in the form of a cross piece 9 and a plunger 10, formed integrally with the support 6b, 6a respectively. The cross piece 9 and the plunger 10 define a manually grippable elements adapted to facilitate their operation with one hand only.

The device is assembled with the stent by inserting the fingers 4a, 4b through the stent 2 to support the stent slidably from within and enabling movement of the stent on the fingers longitudinally and parallel to the axis

2a.

In operating the device, the catheter is advanced through the entry 7 into the void, with the stylet 21 having been inserted into the open distal end of a lumen of the catheter. The stylet serves to guide and align the catheter within the sheath. With the balloon of the catheter aligned within the sheath, the stent 2 is slid along the fingers 4a, 4b. Because of the flared configuration of the fingers, that will tend to cause slight elastic enlargement of the stent from its minimum radial configuration. The stent is slid along the fingers to the free ends 4a", 4b" of the fingers 4a, 4b to the slightly expanded circumferential configuration greater than that of the balloon of the catheter 3 as shown in FIG. 2. In this configuration, the stent is in readiness to be transferred onto the balloon.

In order to effect the transfer, the device 1 can be held in one hand and the grippable elements 9, 10 are drawn together, thereby causing the second support 6b to slid distally in relation to the first support 6a which remains stationary. The fingers 4b attached to the second support 6b thus are caused to be retracted longitudinally from within the stent 2 (see FIG. 2).

With the pair of fingers 4b retracted, the stent 2 remains supported only by the pair of fingers 4a that extend through the stent and by the catheter 3.

With the fingers 4b having been retracted, the frictional resistance presented to sliding of the stent off of the sheath is reduced. The stent 2 can be slid, by hand, along the remaining fingers 4a and ease gradually onto the catheter 3. The frictional resistance presented to sliding movement of the stent 2, however, will have been reduced substantially. Consequently, the transfer of the stent onto the balloon is made easier with conventional length stents as well as with longer stents.

From the foregoing, it will be appreciated that the objects of the invention are fully realized, that a stent of any given length can be placed with ease and positioned correctly on the catheter. The device is of simple construction and is adapted for low cost disposable use. It is readily preassembled with a stent at the stent manufacturing facility. The device and the method by which it achieves its objectives enhance the ability of a physician to place the stent safely, and quickly.

Claims

1. A device (1) for loading an endovascular stent (2) onto a catheter (3) insertable into a body vessel comprising: an elongate sheath (50) defining an internal space (5) receptive to the catheter (3); the sheath (50) being insertable through the lumen of a tubular stent (2) and being configured to provide support for the stent (2) and along which the stent can be slidably advanced and transferred from the sheath to the catheter; the sheath (50) being constructed in at least two component parts (51 , 52) movable relative to each other to enable one of the components to be withdrawn from within the stent while the stent remains supported by the remaining components of the sheath.

2. A device as in claim 1 , wherein the component parts (51 , 52) of the sheath (50) include supports (6a, 6b) slidably coupled to each other.

3. A device as in claim 2, wherein the supports (6a, 6b) are coaxially disposed and have cooperative members preventing their relative rotation about the common direction (2a).

4. A device as in claim 3, wherein the cooperative members comprise at least one stop (8) carried by one of the supports (6a, 6b) and coupled with a slot (20) on the remaining support.

5. A device as in claim 1 , further comprising the supports (6a, 6b) having grippable elements (10, 9) adapted to enable the device (1) to be held and the component parts (51 , 52) of the sheath to be retracted from the stent (2) utilizing one hand only.

6. A device as in claim 5, comprising grippable elements (10, 9) embodied integrally with the supports (6a, 6b) and capable of movement in opposition one to another.

7. A device (1 ) for mounting an implantable endovascular stent

(2) to a catheter (3) of an expandable delivery system insertable into a blood vessel of the human or animal body, comprising first means (51 ) by which a stent (2) of tubular embodiment is supported from within in a configuration of minimum radial proportions; second means (52) by which the tubular stent (2) is supported from within in said configuration; the first and second means

(51 , 52) cooperating to accommodate and ensheath the catheter (3) in such a manner that the device will serve as a guide along which to direct the stent (2) slidably towards and ultimately onto the catheter (3); wherein the first means (51 ) and the second means (52) of support can be distanced independently from positions occupied between the stent (2) and the catheter (3) so as to allow of reducing the resistance to sliding movement encountered by the stent (2) when transferred to the catheter (3).

8. A method of mounting an endovascular stent (2) to a catheter (3), comprising the steps of: placing the stent (2) on an elongated sheath (50) consisting in at least two independently controllable component parts (51 , 52); distancing at least one component part (51 , 52) of the sheath (50) along the axis (2a) of the stent (2) to the point at which the selfsame part (51 , 52) is at least partly retracted from the stent (2); and then transferring the stent from the sheath onto the catheter.

9. A method as defined in claim 8 further comprising: inducing elastic expansion of the stent to a diameter greater than that of the catheter while the stent is on the sheath; and while transferring the stent from the sheath to the catheter, eliminating the elastic force of expansion so that the stent (2) can contract under the influence of its inherent elasticity, about the catheter.

10. A disposable assembly comprising an endovascular stent (2) and a relative device (1) for the fitment of the stent to a catheter (3), as in preceding claims.

11. A device for loading a stent onto the balloon of a delivery catheter comprising: a tubular sheath having an open end adapted to receive the balloon of the catheter, the sheath being insertable into a stent and adapted to support the stent in surrounding relation to and about the balloon; the sheath being formed from a plurality of components, at least one of which can be withdrawn from within the stent before the stent is transferred, slidably with respect to the sheath, onto the balloon whereby during such transfer, thereby to reduce the frictional resistance between the stent and the sheath during transfer.