Balloon catheter, in particular for delivering drugs or stents in the region of a stenosis

A balloon catheter, in particular for delivering medicaments, stents or medicament-coated stents in the region of a stenosis, comprising

TECHNICAL FIELD

The invention relates to a balloon catheter, in particular for delivering medicaments or stents in the region of a stenosis, the balloon catheter having an outer shaft, an inner shaft and a balloon at the distal catheter end, which balloon is dilatable by a feedable pressure fluid. The balloon is attached with its proximal end to the outer shaft and with its distal end to the inner shaft which protrudes the outer shaft in the distal direction.

BACKGROUND

With respect to the background of the invention it is to be noted that for delivering stents in the region of stenoses or lesions in a body vessel or for releasing medicaments in such body regions, catheters of different designs are used. US 2009/0018501 shows a balloon catheter, the balloon of which is coated with a medicament. The balloon is arranged in the manner of a rolling membrane between outer and inner shaft. When inserting the catheter into the body, the inner shaft is displaced relative to the outer shaft in the proximal direction so that the balloon is covered between outer and inner shaft. At the site of use, the balloon is then inflated by means of a pressure fluid, wherein the outer shaft is displaced relative to the inner shaft in the proximal direction and the balloon opens like a rolling membrane in a rolling and shearing manner and dilates. The problem here is the fact that during opening the rolling membrane balloon, the membrane of the same is subjected to very small bending radii and high shear forces so that the coating with the active ingredient can be peeled off the balloon in an uncontrolled manner. Moreover, when the balloon opens, or already on the way to the site of use, losses of active ingredients can occur.

In connection with the delivery of stents, US 2009/0259286 A1 shows a catheter with a stent which, during the insertion of the catheter, is retained in the contracted position underneath a sheath at the distal end. Said sheath is configured such that when the balloon dilates and thereby the stent expands, it breaks along a predetermined path. This requires a relatively complicated and error-prone design of the sheath. Accordingly, the positioning of the stent can be inaccurate.

Finally, from US 2005/0033402 A1, a delivery device for a stent is known wherein the latter is arranged and covered underneath a sheath during the insertion. For releasing the stent, the sheath is provided with a pull wire by means of which the sheath can be pulled away on the proximal side and accordingly, a release of the stent can be achieved. This, of course, requires an extremely complicated construction of the catheter. Further, the pull wire is susceptible to breaking. In this case, releasing the stent is not possible anymore.

In EP 0 596 145 B1, a method is described by means of which the retention force of the stent on the catheter is achieved by means of embossing the stent pattern under the influence of temperature. Because the balloon shortens under the thermal effect, the embedding with this method is only optimal in the case if the stent itself is embedded in the balloon under thermal effect and the stent is virtually “frozen” in the balloon material. For stents coated with medicaments, this method can only be applied as long as the glass temperature of the balloon material lies far below the degradation temperature of the medicament.

From U.S. Pat. No. 7,651,525 B2, a stent device is known in which a catheter has an outer sheath which extends from the distal to the proximal end and in the distal end region of which, a self-expanding stent is arranged on a dilatable balloon in the contracted state. To deliver the stent, the outer sheath is pulled back manually by a practitioner or by a mechanical actuation in the proximal direction relative to the stent. The latter is positioned in a body vessel while inflating the balloon and self-extracting at the treatment site.

SUMMARY

Based on the described problems of the prior art, the object underlying the invention is to improve a balloon catheter for delivering medicaments or stents in such a manner that this can be carried out reliably and accurately and with simple handling and low constructional efforts for the catheter, and that it is gentle to the active ingredient in the case of a medicament release.

This object is solved by the balloon catheter, wherein a cover sheath is provided which is seated in a covering position over the contracted balloon and is displaceably guided on the outer shaft and which is displaceable on the outer shaft in the proximal direction via its front opening by the dilating balloon while continuously releasing the same from distal to proximal.

Due to this configuration, no separate mechanism is necessary for releasing the balloon by pulling the cover sheath back; in fact, the cover sheath is automatically displaced by the dilating balloon, whereby the balloon is continuously released. Since this releasing process starts from the distal end of the balloon, the balloon catheter can anchor itself in the vessel on the other side of a stenosis so that thereby the blood flow in the vessel is stopped. Thus, in particular a self-expanding stent can be accurately positioned and can be delivered without the tendency to spring during opening.

With this catheter, medicament-coated stents can be reliably transported underneath the cover sheath to the stenosis without the need that the stent has to be embedded separately in the balloon. The thermal load of the medicament coating which is necessary for fixing the stent on the balloon thus is eliminated. If stent segments tend to stand up (“fish scaling”) when passing through narrow curves, the cover sheath ensures that said segments do not get caught in the body or at the guide catheter thereby stripping off the stent.

Also, no separate actuation of the cover sheath is necessary because the same is displaced virtually automatically by the balloon. In the case of a balloon having a medicament coating, due to the balloon dilating from the distal end and the resulting anchoring of the balloon in the vessel thereby stopping the blood stream, no loss of active ingredients is involved because no blood stream is present which could wash off the medicament. When releasing the balloon—in contrast to the aforementioned rolling membrane balloon—the coating is not subjected to narrow bending radii and shearing connections.

According to preferred embodiments of the invention, the axial friction force between balloon or, respectively, stent and sheath can be significantly reduced by generating a counter pressure to the inner pressure of the balloon in the region between balloon and sheath. For this purpose, the cover sheath is preferably displaceably guided in a pressure-tight manner on the outer shaft.

Finally, the pressure equalization in the intermediate space between cover sheath and balloon can be carried out with the pressure fluid used to dilate the balloon, for example in such a manner that the intermediate space between cover sheath and balloon communicates with the pressure fluid line to the balloon via a passage opening in the outer shaft.

According to a further preferred embodiment of the invention, the balloon catheter can be used to place self-expanding stents. For this purpose, the stent is retained in the contracted state on the balloon by the cover sheath in the covering position and is gradually released through the dilating of the balloon.

According to an alternative embodiment, the cover sheath serves for a securely covered transport of the active ingredient-coated balloon to the region of the stenosis and—as already mentioned above—for a gentle release of the active ingredient.

According to a further preferred embodiment, a limit stop is arranged on the outer shaft for limiting the displacement path of the cover sheath in the proximal direction. Thus, the movability of the cover sheath can be limited in such a manner that it is clamped between the cone of the dilated balloon and the limit stop so that a good sealing between the front opening of the cover sheath and the balloon cone is achieved. Then, the balloon can be pressurized with the maximum target pressure without the risk that the pressure fluid escapes through the intermediate space, which is pressurized as well, between balloon and cover sheath.

Stripping off the cover sheath in the distal direction can be constructionally prevented by a dead stop which is larger than the proximal cover sheath diameter. The dead stop can be generated as a ring which is crimped on or glued on, or by deforming the outer shaft.

To facilitate a reliable gradual opening of the balloon during dilatation from distal to proximal it is of advantage that in the covering position of the cover sheath, an initial opening gap for the balloon remains between the front opening and a cone body at the distal end of the inner shaft.

The secure emptying of the balloon during deflation can be ensured by two measures: on the one hand, by setting a higher flow resistance in the direction towards the cover sheath, e.g., by an outlet opening which is only very small compared to the large flow cross-section in the direction towards the balloon or, on the other, by supplementing a check valve with a very thin, resilient ring-shaped membrane which is shrunk on the outside of the outer shaft over the outlet hole. When inflating, said membrane lifts off and supplies the cover sheath with the necessary counter pressure. When deflating with a maximum of 1 bar pressure difference, the membrane securely closes the outlet hole. Both measures can also be combined.

DETAILED DESCRIPTION

Collectively,FIGS. 1-8show the distal end region of a balloon catheter1which is placed in the region of a stenosis2in a body vessel3. The balloon catheter1has an elongated, flexible outer shaft4and an inner shaft6running therein and extending beyond the distal end5of the inner shaft4, which inner shaft is also made of a flexible material. A balloon7which can be dilated by a pressure fluid is fastened at the distal catheter end in a pressure tight manner with its proximal cone8to the distal end5of the outer shaft4and with its distal cone9to the cone body10at the distal end11of the inner shaft6.

Via the annular space13, the balloon volume12can be pressurized between outer and inner shaft4,6with a pressure fluid.

In the drawings, the hatched area designated with the reference number14indicates a coating with a medicinal active ingredient or stent which is to be applied by means of the dilatable balloon7in the region of the stenosis.

Finally, the balloon catheter1is provided at its distal end with a cover sheath15which is displaceably guided in the direction of the longitudinal axis on the outer shaft4. The cover sheath15is seated over the balloon7which is contracted and folded in the position according toFIG. 1and protects the latter together with the coating/stent14when inserting the catheter into the body vessel3. As is apparent fromFIG. 1, the balloon7emerges via the front opening17at the distal end of the cover sheath15, wherein between the front opening17and the cone body10an initial opening gap18remains through which the balloon cone can emerge to the outside.

The cover sheath15protrudes the balloon7in the proximal direction and thus forms an intermediate space19behind the balloon7where a passage opening20in the outer shaft4communicates with the pressure fluid line formed by the annular space13. Thus, with the pressurization of the balloon7, the intermediate space19is pressurized at the same time so that between balloon7and the cover sheath15, a counter pressure is generated which counteracts a “wedging” effect between the balloon7and the cover sheath15.

With distance A to the proximal end16of the cover sheath15, an annular circumferential dead stop21is provided on the outer shaft4. The distance A defines the maximally possible displacement path of the cover sheath15on the catheter in the proximal direction.

The operating mode of the balloon catheter1is now to be described as follows:

In the configuration shown inFIG. 1, the balloon catheter is advanced to the shown stenosis2in the body vessel3. Here, the coating/stent14is properly stored within the cover sheath15, and the balloon7is kept at its minimum diameter. Due to said storage, the catheter has a profile with a small area even after passing narrow radii. In particular, no so-called “fish scaling” of a stent14seated on the balloon7occurs in narrow curves. Furthermore, a separate embedding of a stent14on the stent7is no longer necessary due the cover sheath15.

Upon reaching the target position in the region of the stenosis2, as shown inFIG. 2, the balloon7is pressurized by introducing a pressure fluid via the annular space13. The balloon7begins to expand in the initial opening gap18, whereby at the same time, a stripping force F on the cover sheath15is generated in the axial direction towards proximal. The cover sheath15thus slides back on the outer shaft4and continues to release the balloon7while the same continues to dilate. (seeFIGS. 2 and 3).

Since the balloon7expands at the distal end of the catheter in front of the stenosis2, the balloon with the coating/stent14is distally anchored in front of the stenosis2(FIG. 4) so that then the blood flow through the body vessel3is stopped. Active ingredients in the coating14are thus not washed out and therefore a smaller dosage can be achieved there.

With increasing expansion of the balloon7, the sheath15is continuously displaced in the proximal direction and the coating/stent14is delivered in the region of the stenosis2and the latter is increasingly widened (FIGS. 5 and 6).

In the final phase of the dilatation of the balloon7, the coating/stent14is finally applied on the body vessel3by means of the fully expanded balloon7, whereby, at the same time, the stenosis2is removed (FIG. 7); the cover sheath15has finally reached its end position (FIG. 8) at the dead stop21, whereby the proximal cone8of the balloon7can be supported at the front opening7. The pressurized intermediate space19is thus sealed so that the balloon7can be pressurized with its full target pressure and can be completely dilated.

By pressure relief, the balloon7can contract again and the catheter1can be removed from the body.

It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teaching. The disclosed examples and embodiments are presented for purposes of illustration only. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention.