DE29919625U1 - Application cutlery for inserting stents - Google Patents

Description

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PATENT ATTORNEYS DIPL.-ING. R. LEMCKE DR.-ING. H. J. BROMMER DIPL.-ING. F. PETERSEN DIPL-ING. D. BLUMENROHR

BISMARCKSTRASSE 16 76133 KARLSRUHE TELEPHONE (07 21) 91 28 00 TELEPHONE (07 21) 2 11 05

25 October 1999 17 885 (A/gr)

Helmut Lindenberg Wolfrainstraße 2 76694 Forst

Application kit for inserting stents PATENT ATTORNEYS

DIPL.-ING. R. LEMCKE DR.-ING. H. J. BROMMER DIPL.-ING. F. PETERSEN

DIPL-ING. D. BLUMENROHR

BISMARCKSTRASSE 16 76133 KARLSRUHE

TELEPHONE (07 21) 91 28 00 TELEPHONE (07 21) 211 05

25 October 1999 17 885 (A/gr)

Description

The invention relates to an application set, in particular for introducing stents to widen stenoses, with a guide element which has a section for carrying a stent, and with a holding element which at least partially fixes the stent in said section and which can be actuated from the proximal end of the set for the particularly sequential release of the stent.

In medical technology, such application instruments are used to insert so-called stents, i.e. hollow cylindrical foreign material implants, in a radially compressed state through a small opening in the body surface of a patient into pathologically narrowed blood vessels or other channel-like passages and to free them from the holder of the instrument. After release, the self-expanding stents that are widely used today expand radially outwards on their own, also expanding the surrounding wall of the blood vessel, for example, and thus permanently eliminating the narrowing.

It is known in the prior art that the holding element, which is formed, for example, from a tubular sheath enclosing the guide element and is then referred to as a lock, completely covers the surface of the stent that has not yet been released and thus fixes the stent on the section of the guide element that supports it.

The stent is initially released at its distal end by pulling back the tubular casing relative to the guide element in the direction of the proximal end of the application set. (In the context of this application, a proximal or distal end is understood to mean the end adjacent or distant from a surgeon inserting the application set into the interior of the body.) The self-expanding stent then expands at this released end until it rests against the adjacent wall of the blood vessel, in which area it detaches from the section of the guide element that supports it. By pulling back the tubular casing further relative to the guide element, the middle area and finally the proximal end area of the stent are released next, so that these areas also expand and detach from the section that supports them. The stent then rests against the blood vessel wall along its entire length.

The guide element and the sheath are then pulled out of the body, leaving the stent in this expanded state.

However, there are disadvantages with such application instruments when it comes to the correct axial positioning of the stent within the blood vessel. If the surgeon sees the need to move the stent to a different position within the blood vessel after the distal end of the stent has already been released, complications may arise because the expanded end of the stent has already become entangled in the blood vessel wall.

The surgeon guiding the instrument can essentially only determine the position of the still fully compressed stent on the guide element indirectly via the platinum markings that delimit the section carrying the stent and are visible on the X-ray screen. If the surgeon now moves the instrument with the guide element and tubular sheath and thus the stent in the proximal direction

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If one wants to, it can happen that the stent remains in its axial position in relation to the blood vessel because its already released distal end gets caught in the blood vessel wall. If the instrument with the guide element and tubular sheath is pulled back further, additional areas of the stent are then unintentionally released. Above all, however, this causes the stent to slip distally from the section of the guide element that supports it. After this, the platinum markings on the guide element no longer determine the correct axial position of the stent. The stent itself, which is still faintly visible on the X-ray screen when compressed, is no longer visible on the screen at all when expanded because the X-rays are then hardly absorbed due to the now significantly lower material density of the stent.

If, however, the surgeon wishes to move the instrument in a distal direction, there is a risk of perforation of the blood vessel wall due to the described entanglement, as the stent is pressed against the wall like a barb with its expanded end region.

After a partial expansion in the end area of the stent, changing its position again is associated with high risks.

It is also not possible, particularly when using self-expanding stents, to return the stent to its original, fully compressed state after partial release, which would be advantageous in order to be able to change its axial position safely. The forces required to move the tubular casing in a distal direction over the already released and expanded end area of the stent are too great and lead to perforations.

Another disadvantage of the application instruments currently in use is that when a self-expanding stent is finally released, i.e. when the tubular sheath is pulled back beyond the proximal end of the stent, the application instruments are moved at speeds of up to 100 mbar and

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A catapult effect occurs during the rapid expansion, so that forces in the distal direction occur, which can initially lead to unintentional perforations of the blood vessel wall through the already expanded distal end. In particular with stents whose diameter was chosen to be only slightly too small in the expanded state, there is a very high risk that the stent will make a "jump" in the distal direction due to insufficient friction between it and the blood vessel wall, which cannot be seen on the X-ray screen, so that it is incorrectly placed.

The invention is therefore based on the object of creating an application kit which avoids the known disadvantages of the prior art and in particular allows a subsequent correction of the axial position of a stent while excluding damage to the vessel wall and prevents the stent from "jumping" from the intended axial position to another position when the stent is completely released.

Starting from an application set as described above, this object is achieved in that at least one holding element is provided on the application set, which fixes one end of the stent and can be actuated independently of the holding element to release this end.

In addition to the holding element, the application kit therefore has an additional holding element which advantageously fixes the distal end region of the stent in particular, while the holding element holds the middle region and the proximal end region of the stent in its position. Of course, several holding elements can also be provided which, for example, fix the proximal end region and the middle region of the stent, while the holding element holds the distal end region in its position.

The application kit according to the invention has the advantage that a large part of the stent can be released, while the stent can still remain fixed at its two end areas and can be held there in a compressed state. By releasing the middle

The stent can expand to its full diameter in this area, so that the surgeon can already observe a widening of the blood vessels in this area on the X-ray screen. However, he will only be able to see such a widening if the stent has expanded in the correct position within the blood vessels, i.e. at the site of the stenosis.

Furthermore, the surgeon is able to see both compressed ends of the stent on the screen in this state, so that he can determine the position of the stent precisely. The platinum markings also help him to correctly identify the section of the guide element that carries the stent.

In addition, it is also possible for the surgeon to reverse the release, i.e. he can compress the stent again in its middle area so that the stent can be safely repositioned within the blood vessel. This is made possible by pushing the holding element in the distal direction over the middle area of the stent, whereby the holding element compresses it again. This creates axial forces on the stent that are directed towards the distal end. The counterforces in the proximal direction that compensate for these forces are applied by the holding element and thus by the application equipment. In the prior art, however, pushing the holding element again over the middle area of the stent in this way leads to the area of the stent that is already in contact with the blood vessel wall being forcibly pushed along the wall by the forces generated by the holding element, which can lead to perforations due to friction.

Thus, the surgeon is not only dependent on the platinum markings or the view of the compressed ends of the stent for correct positioning, but can also significantly increase the accuracy of positioning by test-releasing the middle area of the stent.

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In addition, the catapult effect mentioned above is prevented because the stent is still held at the other end when one end region is completely released, so that an axial "jump" or perforation of the blood vessel wall by the holding element or mounting element of this end is prevented.

In an advantageous embodiment, the mounting element and the holding element together cover the entire surface of the stent. This has the advantage, particularly when using a self-expanding stent, that it cannot expand in any area before it has been brought to the site of the stenosis.

Advantageously, the mounting element and the holding element are each tubular sheaths that radially surround the guide element and the stent and completely fix the stent in the section. The advantage here is that the tubular sheaths represent extremely space-saving mounting elements or holding elements, which ensures that the application equipment can be used gently inside the body.

The tubular sheaths are advantageously made of a plastic whose tensile strength is greater than the radial force of a self-expanding stent. This is necessary when using such stents, as they must be prevented from expanding due to body temperature before they are brought to the site of the stenosis.

It is also advantageous that the tubular casing forming the holding element covers both the proximal end region and the middle region of the stent. With this arrangement, the holding element then covers the distal end region of the stent. This makes it possible for the entire middle region of the stent to be released simply by pulling back the tubular casing forming the holding element in the direction of the proximal end of the application set, so that it can expand there to its full diameter.

Furthermore, the tubular casing forming the holding element can be guided at least as far as the proximal end area of the application set. This ensures that the holding element can be actuated from there and thus the release of the stent area fixed by the holding element is easily possible from the proximal end of the application set.

In this context, it is advantageous that the coverage of the stent caused by the tubular casing forming the holding element can be reduced or increased to complete coverage of the stent by an axially directed relative movement between the guide element and the tubular casing. The stent can therefore be partially released by pulling back the tubular casing forming the holding element in the direction of the proximal end of the application set, but a corresponding counter-movement of the tubular casing also makes it possible to cover the stent again, returning it to its initial compressed state. In this state, adjustments to the axial position of the stent within the blood vessel are possible without danger, as the risk of perforation is avoided.

The proximal end region of the stent can be released by reducing the overlap to zero. Once the stent has assumed its optimal axial position, the tubular casing forming the holding element can be pulled back in relation to the guide element to such an extent that the proximal end region of the stent is released. It is advantageous that the distal end region of the stent continues to be fixed by the holding element, which avoids the catapult effect mentioned above.

Furthermore, an overridable stop can be provided at the proximal end of the application set, which limits the reduction of the coverage by limiting the relative movement in a first release step to a release of the middle area of the stent.

The stop that can be overcome prevents the surgeon from accidentally pulling the tubular casing that forms the holding element back so far in the direction of the proximal end of the application instrument that the proximal end area of the stent is immediately released, expands and comes into contact with the surrounding blood vessel wall. This would make it impossible to safely correct the position of the stent. The stop therefore means that the stent is initially held at both of its end areas, which means that it can be positioned safely. After this positioning, the surgeon can overcome the stop, for example by lowering it, and completely release the proximal end area of the stent.

In a further advantageous embodiment, the tubular sheath forming the holding element is connected to a catheter tip attached to the guide element. The connection of the tubular sheath, guide element and catheter tip ensures that after the proximal end region of the stent has already been released and the resulting friction of the stent on the blood vessel wall surrounding it, the guide element and with it the tubular sheath can be moved in the distal direction, whereby the distal end region of the stent is released.

Furthermore, the catheter tip can be designed in a hollow cone shape, so that it can be easily inserted into very narrow blood vessels.

The guide element is advantageously designed as a flexible tube so that the inside of the tube can be used to guide medicines to the site of the stenosis, for example. The flexibility of the tube is particularly important in view of the fact that the application equipment must be guided through convoluted blood vessels inside the body, which rarely run in a straight line.

In order to be able to make the position of the stent visible even in the compressed state, it is also advantageous that the guide element

The section intended to carry the stent is limited on both axial outer sides by X-ray sensitive rings. These rings are therefore visible on an X-ray screen and allow the position of the stent to be determined indirectly.

Further features and advantages of the invention will become apparent from the following description of an embodiment with reference to the accompanying drawings. They show:

Figure 1 is a side view of an application kit according to the present invention with a stent completely covered by two tubular sheaths; _y -

Figure 2 is a side view of the application device with the stent released in its central region;

Figure 3 shows a side view of the application kit with the stent only fixed at its distal end;

Figure 4 is a side view of the application kit with the stent fully released;

Figure 5 shows a cross-section of a prior art application device with a self-expanding stent within a blood vessel;

Figure 6 is a side view of the catapult effect occurring with these cutlery items.

Figure 5 shows an application set known in the prior art, in which a tubular sleeve 1 forming the holding element radially encloses a tubular guide element 2. A hollow cone-shaped catheter tip 3 is connected to the guide element 2. Also shown is an X-ray-sensitive ring 5 which encloses the guide element and is used to determine the position of a stent on an X-ray screen. A guide wire 4 can also be seen which, after a puncture of the body surface, is inserted into the body before the application set and pushed to the location of the stenosis. The guide wire 4 then serves as a "sliding rail" for the application.

cation set, over which the set is guided to the site of the stenosis. The guide wire 4 is not part of the application set.

Furthermore, a self-expanding stent 6 is visible, which sits on a section of the guide element before it expands as shown, with its proximal end region 7 being covered and fixed by the tubular sheath 1. Both its middle region 8 and its end region 9 are already in an expanded state corresponding to the full diameter of the stent 6, which was achieved by pulling the tubular sheath 1 back in the direction of the proximal end of the application set 10.

The distal end region 9 of the stent 6 has become entangled with the wall 11 of a blood vessel 12. As can be seen in the picture, the position of the stent 6 with respect to the stenosis 13 of the blood vessel 12 that is to be widened is not optimal, i.e., for optimal positioning, the application set 10 together with the stent 6 must be moved in the direction of the proximal end of the application set 10 so that the stent 6 can be completely released there.

However, there is now a risk that the movement of the application tool could lead to perforations in the wall 11 due to the distal end region 9 of the stent 6 becoming caught in the wall 11. Furthermore, the position of the X-ray-sensitive ring 5 in relation to the stent 6 could change if the stent 6 remains in its position in relation to the wall 11 due to the catch, while the position of the guide element 2 is changed by moving the entire application tool 10 in the direction of the proximal end of the tool 10. This would make it impossible to determine the correct position of the stent.

The two drawings (A) and (B) of Figure 6 show the so-called catapult effect, which occurs when the application set 10 is used in combination with the stent 6 as soon as the stent 6 is completely released from the tubular sheath 1.

In the drawing 6 (A), both the distal end region 9 and the middle region 8 of the stent 6 are already exposed, while the end region 7 is still covered by the distal end region of the tubular casing 1. Both the distal end region 9 of the stent and its middle region 8 are therefore already fully expanded, so that both regions are widened to their final diameter.

In contrast, in drawing 6 (B) it is shown that the now completely released stent 6 executes a forward movement in the direction of arrow 14, i.e. the distal end of the application set, which is also referred to as "jumping". The cause of the "jumping" is the sudden release of the proximal end region 7 of the stent 6, whereby it expands to its full diameter at up to the speed of sound and is accelerated forwards like a catapult from the tubular casing 1, i.e. towards the distal end of the application set 10.

Figure 1 shows an application kit 10 which is designed according to the present invention.

The set 10 consists of a tubular casing 1 that forms the holding element, at the end of which a second tubular casing 14 that forms the holding element is connected, so that both completely cover the surface of a self-expanding stent 6 that is not visible in this drawing. The tubular casing 1 is guided - not visible here - to the proximal end area of the application set. In addition, the two tubular casings made of plastic enclose an internal, flexible tube 2 that serves as a guide element but is not visible in this illustration. Medicines can be guided to the site of the stenosis through the inside of the tube.

The tubular sheath 14 is connected to a hollow cone-shaped catheter tip 3, which in turn is attached to the flexible tube 2.

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Furthermore, two X-ray-sensitive graft rings 5 are provided, which delimit the section carrying the self-expanding stent 6 at its distal and proximal end regions and thereby enable the determination of the axial position of the stent 6 within the blood vessel in the fully compressed state on an X-ray screen.

Figure 2 shows the application kit 10 with the stent 6 released in its central region 8, with the stent sitting on a section of the guide element. The central region 8 has already expanded to its final diameter.

This state was achieved by pulling back the tubular sheath 1 in the direction of the proximal end region of the application set 10, so that the covering of the stent 6 in the middle region 8 by the tubular sheath 1 was removed. It is also visible that the stent 6 is still completely held by the tubular sheaths 1 and 14 in its end regions 7, 9. It is therefore easily possible to push the tubular sheath 1 back in the direction of the distal end of the application set 10, so that it compresses the stent 6 and again completely covers it. A subsequent correction of the axial position of the stent 6 within the blood vessel is then possible without any problems, without damaging the surrounding wall of the blood vessel.

Figure 3 shows the application kit after the tubular sheath 1 has completely released the proximal end region 7 of the stent 6.

Clearly visible in the figure are both the flexible pipe 2 and a filling material 15 surrounding the pipe.

In contrast to Figure 2, in Figure 3 the proximal end region 7 has already been released and expanded to its full diameter by further retracting the tubular sheath 1 in the direction of the proximal end of the application set 10. The other tubular sheath 14, on the other hand, continues to fix the distal end region 9 of the stent 6, whereby the

The force resulting from the catapult effect is absorbed in the direction of the distal end of the application instrument 10. This prevents the stent 6 from "jumping" and allows for very precise positioning of the same.

The final, complete release of the stent 6 is shown in Figure 4. After the release of the proximal end region 7 of the stent 6 shown in Figure 3, the distal end region 9 of the stent 6 can also be released by moving the flexible tube 2 in the direction of the distal end of the application set 10. This is possible because the proximal end region 7 of the stent 6 rests against the wall 11 of the blood vessel 12 (not shown here), remains in its axial position and thereby changes its position with respect to the tubular casing 14.

After release, the distal end region 9 of the stent 6 also expands at up to the speed of sound, so that by subsequently withdrawing the entire application set 10 only the stent remains within the stenosis.

Claims (13)

1. Application set ( 10 ), in particular for introducing stents ( 6 ) for widening stenoses ( 13 ), with a guide element ( 2 ) which has a section for carrying a stent ( 6 ), and with a holding element ( 1 ) which at least partially fixes the stent ( 6 ) in said section and which can be actuated from the proximal end of the set ( 10 ) for the particularly sequential release of the stent ( 6 ), characterized in that at least one holding element ( 14 ) is provided which fixes one end ( 9 ) of the stent ( 6 ) and can be actuated independently of the holding element ( 1 ) for the release of this end ( 9 ). 2. Application kit according to claim 1, characterized in that the mounting element ( 1 ) and the holding element ( 14 ) together cover the entire surface of the stent ( 6 ). 3. Application kit according to claim 1, characterized in that the mounting element ( 1 ) and the holding element ( 14 ) are each tubular sheaths ( 1 , 14 ) which radially enclose the guide element ( 2 ) and the stent ( 6 ) and completely fix the stent ( 6 ) in the section. 4. Application kit according to claim 3, characterized in that the tubular sheaths ( 1 , 14 ) are made of a plastic whose tensile strength is greater than the radial force of a self-expanding stent ( 6 ). 5. Application kit according to claim 3, characterized in that the tubular sheath ( 1 ) forming the holding element ( 1 ) covers both the proximal end region ( 7 ) and the middle region ( 8 ) of the stent ( 6 ). 6. Application set according to claim 3, characterized in that the tubular sheath ( 1 ) forming the holding element ( 1 ) is guided at least from the proximal end region ( 7 ) of the stent ( 6 ) to the proximal end region of the application set ( 10 ). 7. Application kit according to claim 3, characterized in that the coverage of the stent ( 6 ) caused by the tubular sheath ( 1 ) forming the holding element ( 1 ) can be both reduced and increased up to complete stent coverage by an axially directed relative movement between the guide element ( 2 ) and the tubular sheath ( 1 ). 8. Application kit according to claim 7, characterized in that a release of the proximal end region ( 7 ) of the stent ( 6 ) is effected by an overlap reduced to zero. 9. Application set according to claim 7, characterized in that an overcoming stop is provided at the proximal end of the application set ( 10 ), which restricts the reduction of the coverage by limiting the relative movement in a first release step to a release of the central region ( 8 ) of the stent ( 6 ). 10. Application kit according to claim 3, characterized in that the tubular sheath ( 14 ) forming the holding element ( 14 ) is connected to a catheter tip ( 3 ) fastened to the guide element ( 2 ). 11. Application kit according to claim 10, characterized in that the catheter tip ( 3 ) is hollow cone-shaped. 12. Application kit according to claim 1, characterized in that the guide element ( 2 ) is designed as a flexible tube ( 2 ). 13. Application kit according to claim 1, characterized in that the section is limited on both axial outer sides by X-ray sensitive rings ( 5 ).