US20020198586A1

Movatterモバイル変換

Info

Publication number: US20020198586A1
Application number: US09/366,419
Authority: US
Inventors: Kanji Inoue
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-04-12
Filing date: 1999-08-04
Publication date: 2002-12-26
Also published as: US6364901B1

Abstract

An artificial blood vessel A comprises a pair of discrete end wire rings10₁, 10₂, a tubular cover7made of a sheet of flexible, tensile material which connects the end wire rings10₁, 10₂, and a plurality of intermediate wire rings12arranged spaced apart between the end wire rings10₁, 10₂and circumferentially fixed to the cover7by suturing or with adhesive. All of the rings are located on the outside of the cover. To implant the vessel A via a catheter, a plurality of dividing points41₁, 43₁which bisect the circumference of the front end wire ring10₁are pulled forward while the movement of the midpoints42₁, 44₁between the dividing points41₁, 43₁following the movement of the dividing points41₁, 43₁is restrained by the projections18con a tapered surface18dof a funneled tube18so as to fold the front end wire ring10₁into a wavy shape, with the dividing points41₁, 43₁forming forwardly directed peaks and the midpoints42₁, 44₁forming the bottoms of forwardly directed valleys. The dividing points of the front wire ring are pulled farther forward so as to fold the intermediate wire rings12and the rear end wire ring10₂into a regular wavy shape having the same phase as that of the front wire ring10₁by the effect of restraint by the tapered surface18dand the projections18c, thereby to collapse the artificial blood vessel A as a whole into a small size for passage through the catheter. Upon release of the artificial vessel from the catheter at the affected portion of the blood vessel, the artificial vessel is restored to its original shape. The end wire rings, the cover, and the intermediate wire rings alone keep the shape of the artificial vessel.

Description

This application is a divisional of application Ser. No. 08/77,717, filed Dec. 20, 1996, which is a continuation-in-part of application Ser. No. 08/411,670, filed Apr. 12, 1995, now abandoned, which is a U.S. national phase application of PCT/JP93/01171, filed Aug. 20, 1993.[0001]

FIELD OF THE INVENTION

This invention relates to appliances for medical treatment and, more particularly, to an appliance collapsible for insertion into a human organ and capable of resilient restoration (which will be referred to as “the appliance to be implanted” in this specification and claims), to a method of collapsing the appliance to be implanted, and to a device for introducing the collapsed appliance to be implanted into a catheter.[0002]

PRIOR ART

The artificial blood vessel is an example of the appliance to be implanted. At present, treatment of, for example, aortic aneurysm is conducted by implanting an artificial blood vessel. In particular, the portion of a blood vessel which has an aneurysm is removed by resection, and an artificial blood vessel is implanted in place of the resected portion and connected to the remaining blood vessel by suturing or the like.[0003]

The above-mentioned method of surgically implanting artificial blood vessels for treatment of aortic aneurysm, however, is highly dangerous. Especially, an emergency operation for treatment of a ruptured aneurysm has a low life-saving rate, and an operation of dissecting aortic aneurysm is difficult to conduct and has a high death rate.[0004]

Therefore, in order to treat these diseases without a surgical operation, a method has been developed of introducing into a catheter an appliance such as an artificial blood vessel in collapsed condition into a human organ such as a blood vessel, and transporting the appliance to a desired position such as an affected or constricted portion thereof, where the appliance is released so as to be expanded and implanted there with accuracy.[0005]

The appliance to be implanted comprises a pair of end wire rings and a frame mainly composed of connecting wires which connect the above-mentioned end wire rings. The appliance is pushed at the rear end wire ring into a catheter and transported to a desired organ in a human body. In order to transport the appliance, the force applied to the rear end wire ring should be transmitted to the front end wire ring. Therefore, it is indispensable that the frame should be made of comparatively strong metal and that the appliance should have the frame as an inevitable constructing element. If the above-mentioned frame is used, interference is likely to take place between the end wire rings and the frame and prevents the end wire rings from being folded, which makes it difficult to fold the end wire rings into a regular wavy shape. The difficulty in folding the end wire rings will make it difficult to collapse the whole appliance to be implanted into a small size.[0006]

As the end wire rings have an elastic limit, if a force exceeding the elastic limit is applied to the rings, the end wire rings folded for insertion into a catheter suffer plastic deformation so that the end wire rings may not be restored to a proper shape when released at an objective position in a human organ. The distortions caused by the plastic deformation may give rise to sliding resistance and prevent the appliance to be implanted from traveling in a catheter, thereby to make it difficult or impossible for the appliance to be transported to a desired position.[0007]

In addition, a frame, if used in the appliance to be implanted, is likely to hinder the appliance from being implanted in an appropriate shape into a human organ. Especially, in placing the appliance into a bent portion of a human organ, the frame may be deformed into a flat shape because different parts of the frame interfere with each other. Even if the appliance has been implanted, it may not be able to function as it is intended to. In the conventional frame, the wire of the wire rings provided at the opposite ends of the frame is exposed, so that the inner wall of a human organ may be scratched and damaged by the wire and blood is likely to leak out from the end wire rings because the rings are not adhered closely to the inner wall of the human organ.[0008]

Even though a check valve is provided at the outer end of a catheter whose front end has been inserted into the blood vessel of a human body beforehand, the check valve must be temporarily opened when the collapsed appliance is introduced into the catheter, thereby to cause a lot of bleeding. It is therefore desirable to provide means for preventing bleeding.[0009]

The present invention has been accomplished to solve the above-mentioned problems. The object of the invention is to develop an appliance of non-frame type, which can solve all of the above-mentioned problems.[0010]

SUMMARY OF THE INVENTION

The method of collapsing the appliance to be implanted in accordance with the invention is characterized by that the appliance to be implanted comprises a pair of discrete end wire rings, a tubular cover made of a sheet of flexible, tensile material which connects the above-mentioned end wire rings, and a plurality of intermediate wire rings arranged spaced apart between the above-mentioned end wire rings and circumferentially fixed to the above-mentioned cover by suturing or with adhesive; and that the method comprises the steps of: pulling forward the front end wire ring at a plurality of dividing points which equally divide the circumference of the front end wire ring while restraining the midpoints between each adjacent two dividing points by a tapered surface from moving forward following the forward movement of the dividing points, thereby to fold the front end wire ring into a wavy shape with the dividing points forming forwardly directed peaks and the midpoints forming the bottoms of forwardly directed valleys, and pulling the dividing points of the front wire ring farther forward thereby to fold the intermediate wire rings and the rear end wire ring into a wavy shape having the same phase as that of the front end wire ring by the effect of restraint with the tapered surface.[0011]

A loop for a pull string to be passed through may be formed at each of the dividing points on the front end wire ring so that a front pull string may be passed through each of the loops and pulled forward. In particular, a common pull string may advantageously be passed through a plurality of loops so that the dividing points may be gathered together by pulling the common front pull string. A funneled guide tube whose bore diameter is gradually reduced toward its forward end may be used to gather the dividing points and the midpoints by pulling forward the dividing points on the front end wire ring of the appliance to be implanted inserted into the funneled guide tube through its rear opening. In particular, resiliently deformable projections can be formed on the tapered inner surface of the funneled guide tube so as to bring the midpoints into contact with the projections thereby to effectively restrain the midpoints from moving forward following the movement of the dividing points and cause the midpoints to approach to each other. The end wire rings can be circumferentially covered with elastic protective material.[0012]

The appliance to be implanted in accordance with the invention is characterized by a pair of discrete end wire rings which are resiliently foldable and provided at opposite ends; that the end wire rings are connected by only a tubular cover made of a sheet of flexible, tensile material; and that a plurality of intermediate wire rings are arranged between the above-mentioned end wire rings and fixed to the above-mentioned cover at appropriate points on the circumference thereof by suturing or with adhesive.[0013]

The flexible, tensile sheet may be made, for example, of warps extending in the axial direction of the appliance to be implanted woven with wefts extending in the circumferential direction thereof. The warps are made of mono-filament of polyester capable of keeping its shape and the wefts are made of multi-filament of polyester having waterproofness.[0014]

The tubular cover may be in the form of bellows. Especially, the end wire rings may advantageously be connected by restraining strings so as to prevent the bellows from overstretching to exceed a given limit. The end wire rings can be circumferentially covered with an elastic protective material. Further, thorns can be provided on the circumference of at least one of the wire rings so as to stick into a human organ to be embedded therein. The thorns may be effectively formed by curving a wire into a loop, crossing the opposite end portions of the wire, and fixing the crossing point, thereby to form the opposite end portions into the thorns.[0015]

The device for introducing the appliance to be implanted in a collapsed state into a catheter in accordance with the invention comprises an attachment having a flexible check valve which closes an open end thereof and fixed to an open end of a catheter, and a cartridge removably attachable to the above-mentioned attachment and having an open end closed by a flexible check valve and a front end portion connected to the above-mentioned catheter when the cartridge is attached to the attachment; and by that the check valve of the cartridge is pushed open to introduce the appliance to be implanted into the cartridge, and while the check valve of the cartridge is kept nearly closed, the front end portion of the cartridge is inserted into the catheter by pushing the check valve of the attachment open.[0016]

The bore diameter of the attachment of the catheter is made larger than that of the open end of the catheter, so that when the cartridge is attached, the bore of the front end portion of the cartridge may be smoothly connected to the open end of the catheter through the attachment of the catheter.[0017]

With the method of collapsing the appliance to be implanted in accordance with the invention, the operation of collapsing the appliance can be conducted with ease and accuracy. It is difficult to fold the front end wire ring into such a small size that can be contained in a catheter just by applying non-directional external force thereto. However, if the dividing points which equally divide the circumference of the front end wire ring are pulled forward with the midpoints provided between the dividing points being restrained by a tapered surface from moving forward following the dividing points, the front end wire ring is folded into a wavy shape with the midpoints serving as footholds and with the dividing points forming forwardly directed peaks and the midpoints forming the bottoms of forwardly directed valleys. After the front end wire ring has been bent, the intermediate and the rear end wire rings also are folded into a wavy shape having the same phase as that of the front end wire ring by pulling farther forward the dividing points on the front end wire ring to transmit the pulling force to the intermediate and the rear end wire rings through the tensile cover, and by simultaneously restraining the intermediate and the rear end wire rings by means of a tapered surface, thereby to collapse the whole appliance into a small size with ease.[0018]

What should especially be referred to is that the method of collapsing the appliance to be implanted in accordance with the invention is characterized by that a pair of end wire rings provided at the opposite ends of the appliance are connected by only a tubular cover which is made of a sheet of flexible, tensile material; and that the front end wire ring is pulled forward. The conventional method, in which the rear end portion of the appliance to be implanted is pushed to insert the appliance into a human organ, requires a relatively strong frame made mainly of connecting wire rings in order to transmit the force applied to the rear end of the appliance to the forward portion thereof. However, the invention is based on pulling the front end wire ring forward, thereby to make it possible to insert the appliance with ease even without a frame. In addition, the cover follows the movement of the wire rings being folded and is transformed into any desired shape, thereby to avoid interference between the wire rings and the frame. Consequently, by the method of collapsing the appliance in accordance with this invention it is possible to fold each of the wire rings into a wavy shape and to collapse the whole appliance into a small size with ease.[0019]

The operation of folding the wire rings is conducted with ease by forming loops for a pull string to be passed through at the dividing points on the front end wire ring and pulling forward a front pull string passed through the loops. In particular, a common front pull string passed through a plurality of loops is more effective to change the pulling force to a force to fold the wire rings because the dividing points are gathered toward each other.[0020]

In collapsing the appliance, a funneled guide tube whose bore diameter is gradually reduced in the forward direction may advantageously be used, so that the dividing points and midpoints of the wire rings are gathered toward each other as the appliance to be implanted is inserted farther into the funneled tube, thereby to collapse the appliance as a whole into a small size. If projections resiliently deformable and engageable with the midpoints are formed on the tapered inner surface of the funneled guide tube, the midpoints are urged toward each other by the counterforce from the projections, and a space is formed between the end wire rings and the funneled guide tube, thereby effectively to prevent the appliance and the funneled guide tube from closely contacting each other to increase sliding resistance therebetween so that the appliance cannot be moved in the guide tube.[0021]

Elastic protective material circumferentially covering the end wire rings is useful to prevent the appliance from being damaged when collapsed into a small size. If the wire ring is bent to such a degree that the elastic limit is exceeded, not only does it becomes difficult for the ring to be restored to its original annular shape but also it becomes impossible to move the ring in a catheter due to the bent portion being caught in the catheter. However, if protective material is provided, the material disperses the tension which would otherwise be exerted locally on the dividing points when the points are strongly pulled, thereby to prevent tension from being applied locally to the dividing points so that the elastic limit is exceeded to bend the wire ring. The protective material prevents the front end wire ring from being plastically deformed, and provides it with a proper capability of resilient restoration to an annular shape and of traveling smoothly in a catheter, thereby to fold the front end wire ring into a regular wavy form.[0022]

The appliance having no frame, as mentioned above, properly functions as an artificial blood vessel. The appliance in accordance with the invention has a feature that the cover itself is tensile and is held by the wire rings at both ends and the intermediate wire rings at appropriate points thereof. Therefore, when the whole is appliance is released from the state of being collapsed and each of the wire rings are resiliently restored to the annular shape, the cover is resiliently restored to its original proper tubular shape. The conventional appliance having a frame is likely to be deformed flatly because of mutual interference of the component parts when it is arranged in a bent portion of a human organ. However, the appliance of the invention having no frame can be transformed into any desired shape so as to conform to different shapes of a human organ.[0023]

A sheet woven with warps and wefts, in which the warps are made of monofilament of polyester and the wefts are of multi-filament of polyester, makes the whole appliance flexible. In addition, the warps provide the cover of the appliance with tensile strength in the axial direction and a capability of keeping its shape, and the wefts make the sheet closely woven and increase its waterproofness.[0024]

If the sheet of the cover is in the form of bellows, the whole appliance is bent smoothly, thereby to improve the condition of the appliance when implanted into a human organ. If the sheet of the cover is in the form of bellows, restraining strings connecting the front and the rear end wire rings can prevent the bellows from stretching to such a degree that the elastic limit is exceeded to be flat.[0025]

The elastic protective material circumferentially covering the wire rings can prevent, as mentioned previously, not only the wire rings from being plastically deformed when folded into a small size but also the inner wall of a human organ from being damaged by direct contact with the wire rings. The protective material also acts as a seal to attach both ends of the appliance to be implanted tightly to the inner wall of a human body, thereby to effectively prevent leakage of blood through the ends of the appliance when implanted.[0026]

When thorns are provided projecting from the wire rings, they stick into the inner wall of a human organ to be embedded therein so that the whole appliance is fixed to the human organ. Therefore, the thorns effectively prevent the appliance from being displaced or even carried by blood flow downstream in a blood vessel. The thorns are formed with ease by curving a wire into a loop, crossing both end portions of the wire, and fixing the crossed parts with a string or the like, even though the material of the wire is difficult to weld. The thorns thus formed reliably function as mentioned above for a long time.[0027]

In addition, with the device for introducing a collapsed appliance to be implanted into a catheter in accordance with the invention it is possible to introduce the appliance to be implanted smoothly into a catheter. In particular, the appliance to be implanted is inserted into the cartridge by pushing the check valve open as far as the appliance reaches a position at which it is almost completely contained in the cartridge. Before or after the insertion, the cartridge is attached to the attachment provided at the open end of the catheter, and then the appliance is pulled farther forward in that condition so as to be introduced into the catheter through the attachment. When the check valve in the attachment is opened, the check valve of the cartridge is closed, so that blood flowing into the cartridge is prevented from flowing outside the body through the cartridge without fail. In addition, if the appliance is to be inserted directly into the catheter, the appliance cannot be inserted smoothly because of the catheter and the appliance being flexible, and the catheter is bent by the force applied to the appliance, thereby to block the passage through which the appliance is to be inserted or to make the catheter fragile. On the other hand, if the appliance is to be inserted into the catheter through the attachment and the cartridge, by making the attachment and the cartridge strong and of such a shape as to be handled with ease it is possible to solve the problem of the catheter being bent or otherwise deformed, thereby to enable the appliance to be introduced into the catheter smoothly and with ease. If the bore diameter of the attachment is made bigger than that of the catheter and the bore diameter of the front end of the cartridge is smoothly connected to that of the open end of the catheter when the cartridge is attached to the catheter, it is possible to prevent the appliance to be implanted from being temporarily swollen in the attachment and caught therein, and to introduce the appliance to be implanted deep into the catheter.[0028]

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an artificial blood vessel used in one embodiment of the invention.[0029]

FIG. 2 is a vertical cross-sectional view of part of the artificial blood vessel.[0030]

FIG. 3 is a perspective view of a device for transporting the artificial blood vessel, used in the embodiment.[0031]

FIG. 4 is a perspective view of a device for introducing the artificial blood vessel, used in the embodiment.[0032]

FIG. 5 is an enlarged vertical cross-sectional view of part of the attachment shown in FIG. 4.[0033]

FIG. 6 is an enlarged vertical cross-sectional view of part of the cartridge shown in FIG. 4.[0034]

FIG. 7 is a perspective view of the artificial blood vessel through which the device for transporting the artificial blood vessel is loosely inserted.[0035]

FIG. 8 is a perspective view showing a step to hold the artificial blood vessel by means of the device for transporting the artificial blood vessel.[0036]

FIG. 9 is a perspective view showing a step to hold the artificial blood vessel by means of the device for transporting the artificial blood vessel.[0037]

FIG. 10 is an enlarged perspective view showing part of the artificial blood vessel kept by the device for transporting the artificial blood vessel.[0038]

FIG. 11 is a perspective view showing a step to introduce the artificial blood vessel into a catheter.[0039]

FIG. 12 is a perspective view showing a step to introduce the artificial blood vessel into the catheter.[0040]

FIG. 13 is a perspective view showing a step to introduce the artificial blood vessel into the catheter by means of the device for introducing the artificial blood vessel.[0041]

FIG. 14 shows the front end wire ring of the artificial blood vessel being folded.[0042]

FIG. 15 shows the front end wire ring of the artificial blood vessel being folded.[0043]

FIG. 16 shows the front end wire ring of the artificial blood vessel being folded.[0044]

FIG. 17 shows the front end wire ring of the artificial blood vessel being folded in a funneled tube.[0045]

FIG. 18 shows the intermediate wire rings and the rear end wire rings of the artificial blood vessel being folded.[0046]

FIG. 19 shows the collapsed artificial blood vessel.[0047]

FIG. 20 shows the artificial blood vessel being inserted into the cartridge.[0048]

FIG. 21 shows the artificial blood vessel inserted into the cartridge.[0049]

FIG. 22 shows the artificial blood vessel transported from the cartridge to the attachment.[0050]

FIG. 23 is a cross-sectional view showing the artificial blood vessel transported to the affected portion.[0051]

FIG. 24 shows a step to release the artificial blood vessel at an affected part in a blood vessel.[0052]

FIG. 25 shows a step to release the artificial blood vessel at the affected part in the blood vessel.[0053]

FIG. 26 is a cross-sectional view showing the artificial blood vessel released at the affected portion in the blood vessel.[0054]

FIG. 27 shows a step to expand the artificial blood vessel by means of a balloon catheter.[0055]

FIG. 28 shows the principle of another embodiment of the invention.[0056]

FIG. 29 shows the principle of a different embodiment of the invention.[0057]

FIG. 30 is a perspective view corresponding to FIG. 12 of a further different embodiment of the invention.[0058]

FIG. 31 is an enlarged perspective view of part of the above embodiment.[0059]

FIG. 32 is an enlarged cross-sectional view along the line Z-Z in FIG. 31.[0060]

FIG. 33 is a perspective view corresponding to FIG. 31 of a modified form of the embodiment.[0061]

FIG. 34 is a partial cross-sectional view of an artificial blood vessel in accordance with the invention, positioned within an affected part of a blood vessel.[0062]

FIG. 35 is a partial cross-sectional view of a related art artificial blood vessel positioned within an affected part of a blood vessel.[0063]

FIG. 36 is a partial cross-sectional view of a modified embodiment of the inventive artificial blood vessel.[0064]

FIG. 37 is a schematic close-up view of a cover material usable in an artificial blood vessel in accordance with the invention.[0065]

FIG. 38 is an end elevational view of an artificial blood vessel representing another modified embodiment of the invention.[0066]

FIG. 39 is an end elevational view of an artificial blood vessel representing a further modified embodiment of the invention.[0067]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be described in detail with reference to the embodiments thereof shown in the accompanying drawings.[0068]

The artificial blood vessel A as the appliance to be implanted, which is collapsed by the method in accordance with this invention, comprises, as shown in FIG. 1, a[0069]

cover

7, end wire rings10₁,10₂and intermediate wire rings12.

The[0070]

cover

7, as shown in FIG. 2, consists of a flexible, tensile sheet shaped into a tube of bellows, the diameter of which generally corresponds to the normal diameter of that portion of the human blood vessel at which the artificial blood vessel A is to be implanted. The sheet of thecover7 is, for example, of warps extending in the axial direction of the artificial blood vessel A woven with wefts extending in the circumferential direction thereof, wherein the warps are of mono-filament made of polyester (about 15 denier) and the wefts are of multi-filament made of a plurality of superfine filaments (about 50 denier) interwoven. Thecover7 is coated, if necessary, with waterproof material, for example, collagen or albumin, to prevent leakage of blood.

The end wire rings[0071]10₁,10₂, whose inner diameter generally corresponds to that of the above-mentionedcover7, are axially spaced apart and arranged face to face, and are fixed to the opposite ends of thecover7 by suturing or with adhesive as shown in FIG. 2. The circumferences of the end wire rings10₁,10₂are covered withprotective braid members10a, which are closely fixed to the end wire rings10₁,10₂at appropriate positions with thread, adhesive or the like.

The intermediate wire rings[0072]12, which comprise, as shown in FIGS. 1 and 2, one or two wire rings12awrapped withprotective film12bmade of cloth or the like, are arranged axially equidistantly between the end wire rings10₂and10₂, and fixed to thecover7 at appropriate positions on the circumference thereof with thread, adhesive or the like. The above-mentioned end wire rings10₂,10₂and the intermediate wire rings12 help keep the tubular shape of thecover7.Thorns12a₁are formed at two diametrically opposite positions on each of those two intermediate wire rings12 each of which comprises two wire rings12a, so that thethorns12a₁may stick into a human organ so as to be embedded therein. In particular, thewires12aof theintermediate rings12 as well as those of the end wire rings10₂,10₂are made of Ti—Ni alloy or the like. The wires of Ti—Ni alloy have a high resilient restoring force, but are hard to weld. As the Ti—Ni alloy has the above-mentioned characteristic, thethorns12a₁are formed by forming a length ofwire12ainto a loop, whose opposite end portions are crossed so as to provide a pair of short lengths of wire projecting from the crossing point, which is tied with a string or the like, and the projecting end wire portions are bent to provide thethorns12a₁on the ring. In the same manner, a pair ofthorns12a₁are provided on another ring formed of a length ofwire12a. The two rings are arranged side by side, with thethorns12a₁on one of the rings arranged diametrically opposite to thethorns12a₁on the other ring. The two rings12aare covered with aprotective film12b, through which thethorns12a₁project outside.

As shown in FIG. 1, let it be assumed here that the circumference of the front end wire ring[0073]10₁to be first introduced into thecatheter8 is bisected by two points which will be referred to as the dividing points41₁,43₁, and the two midpoints between the two dividing points41₁,43₁will be referred to as the midpoints42₁,44₁. On the circumference of the rear end wire ring10₂, those points whose phases are the same as the dividing points41₁,43₁and the midpoints42₁,44₁will be referred to as the points41₂,43₂corresponding to the dividing points41₁,43₁and the points42₂,44₂corresponding to the midpoints42₁,44₁, respectively. On the circumference of theintermediate wire ring12, those points whose phases are the same as the dividing points41₁,43₁and the midpoints42₁,44₁will be referred to as the points41₃,43₃corresponding to the dividing points41₁,43₁and the points42₃,44₃corresponding to the midpoints42₁,44₁, respectively. As shown in FIG. 1, a pair ofloops13 of thread or the like are so formed that the centers thereof are positioned at the dividing points41₁,43₁of the front end wire ring10₁. Restraining strings14 bridge the end wire rings10₁and10₂so as to prevent the artificial blood vessel A from being stretched unnecessarily too much along the axis thereof.

In order to implant the artificial blood vessel A of the above-mentioned construction into a target organ of a human body, a device B for transporting artificial blood vessels (see FIG. 3) is used to transport the artificial blood vessel A to the target organ of the human body through the[0074]

catheter

8 and a device C for introducing artificial blood vessels (see FIG. 4) is used to introduce the artificial blood vessel A into thecatheter8.

The device B for transporting artificial blood vessels, as shown in FIG. 3, comprises a flexible[0075]

metallic tube

2 whose front end portion is connected to ahelical spring2afor guiding, aside window1 formed adjacent the front end of thetube2, a pair ofstrings4 having both their ends fixed to thetube2 adjacent theside window1 and their middle portions formed intoloops4a, and a length ofwire3 slidably inserted into thetube2.

The device C for introducing artificial blood vessels, as shown in FIG. 4, comprises an[0076]

attachment

5 integrally connected to thecatheter8 through anopen end8athereof, and acartridge6 removably attached to theattachment5. As shown in FIGS. 4 and 5, theattachment5 comprises a first and a second

annular member

51,52 which are internally threaded to form female screws, a thirdannular member53 which is externally threaded to form male screws at opposite ends, which engage the above-mentioned female screws thereby to connect the first and the second

annular members

51,52, and astraw member54 which liquid tightly joins the interior of the firstannular member51 with that of theopen end8aof thecatheter8. Acheck valve55 made of elastic membrane is provided inside the secondannular member52 to close the open end thereof. Thecartridge6, as shown in FIGS. 4 and 6, is of generally the same construction as theattachment5 and comprises first and second

annular members

61,62 which are internally threaded to provide internal female screws, a thirdannular member63 which is externally threaded to form male screws at opposite ends, which engage the above-mentioned female screws at opposite ends to connect the first and second

annular members

61,62, and astraw member64 which projects from the firstannular member61 in the direction of insertion. Acheck valve65 made of elastic membrane is provided inside the secondannular member62 to close the open end thereof.

As shown in FIG. 4, the[0077]

straw member

64 of thecartridge6 is so constructed that thefront end portion6athereof is removably fitted into therear end portion5aof theattachment5 which is connected integrally to theopen end8aof the above-mentionedcatheter8. In particular, as shown in FIGS. 4, 5, and6, the bore diameter di of thestraw member54 of theattachment5 is a little larger than the bore diameter d₂of thestraw member64 of thecartridge6, and the length L₂of thestraw member64 is approximately equal to the full length L₁of theattachment5. Similarly the bore diameter d₂of thestraw member64 of thecartridge6 is approximately equal to the bore diameter d₃of theopen end8aof thecatheter8. When thecartridge6 is inserted a certain length into theattachment5, thestraw member64 is inserted into thestraw member54 so that the bore d₂of thestraw member54 is smoothly connected to the bore d₃of theopen end8aof thecatheter8. The above-mentioned

check valves

55,65 are made of elastic membrane, in each of which a normally closed hole, not shown in drawings, is formed.

A funneled[0078]

tube

18, as shown in FIG. 4, is provided as a guide tube to help collapse the artificial blood vessel A. The funneledtube18 is provided with an inlet opening18aof an enlarged diameter at the rear end portion, through which the tubular artificial blood vessel A is inserted into the funneledtube18. The funneledtube18 is gradually reduced in diameter from the inlet opening18ato end in atubular connector18bof a smaller diameter at the front end portion thereof, so that thetube18 has a taperedinner surface18d. The funneledtube18 is removably connected to the cartridge by inserting thefront connector18binto therear end portion6bof thecartridge6. Elasticallytransformable projections18care provided at regular intervals from the rear end portion to the front along two specific generatrices on the taperedinner surface18dof the funneledtube18. When the artificial blood vessel A travels along the taperedinner surface18dof the funneledtube18, theprojections18care elastically transformed by the vessel A to exert a resilient counterforce to the artificial blood vessel A thereby to contract vessel A.

In order to form the[0079]

projections

18cwith ease, as shown in FIG. 4, several pairs ofholes18eare formed on the taperedwall18dof the funneledtube18, and awire18fis inserted through one of each pair ofholes18eand drawn out through the other of the pair ofholes18eso as to form a loopedprojection18cerect on the inner side of the taperedinner surface18d, with appropriate portions of thewire18fbeing tied with astring18g.

The operations of collapsing the artificial blood vessel A and implanting it into a target portion (an affected part[0080]26) of a blood vessel9 by means of the device B for transporting artificial blood vessels and the device C for introducing artificial blood vessels of the above-mentioned constructions, will now be described below.

First, the[0081]

tube

Before or after the above step, the funneled[0082]

tube

18 is attached to acartridge6 as shown in FIG. 13. In attaching the funneledtube18 to thecartridge6, theconnector18bof the funneledtube18 is inserted into theannular member62 of thecartridge6 so that thecheck valve65 of the elastic membrane provided inside theannular member62 is pushed open by theconnector18bof the funneledtube18, and theconnector18bis inserted a little into thestraw64 of thecartridge6. Thefront pull string20 is inserted into the funneledtube18 through therear end portion18athereof and withdrawn forward through thestraw64 at the front end of thecartridge6, with thetube2 inserted a certain length into the funneledtube18. Under the condition, thefront pull string20 is pulled forward to introduce the artificial blood vessel A into the funneledtube18 through the enlarged inlet opening18athereof.

Under the condition, as the[0083]

front pull string

20 is farther pulled, the dividing points41₁,43₁on the front end wire ring10₁of the artificial blood vessel A are pulled by thefront pull string20, as shown in FIG. 14, and the midpoints42₁,44₁are engaged by theprojections18cprovided along the generatrices on the taperedsurface18d, so that the front end wire ring10₁is deformed with the dividing points41₁,43₁approaching toward each other with the midpoints42₁,44₁serving as footholds as shown in FIG. 15. The midpoints42₁,44₁are restricted by theprojections18cand left behind the dividing points41₁,43₁, and urged by the resilient counterforce of theprojections18cto approach each other, thereby to cause the front end wire ring10₁to be folded flat as shown in FIG. 16. In short, the front end wire ring10₁is transformed from the shape shown in FIG. 14 to the shape shown in FIG. 15, and thence to the shape shown in FIG. 16, with the dividing points41₁,43₁where theloops13 are provided forming forwardly directed peaks and the midpoints42₁,44₁forming the bottoms of forwardly directed valleys, so that the front end wire ring10₁as a whole takes a regular wavy shape. In short, as shown in FIG. 17, the front end wire ring10₁is passed through the funneledtube18 while being farther folded. Since thecover7 is tensile, as thefront pull string20 is pulled forward, the pulling force is transmitted through thecover7 to the points41₃,43₃on theintermediate rings12 corresponding to the dividing points and the points41₂,43₂on the rear end wire ring10₂corresponding to the dividing points, as shown in FIG. 18. The points42₃,44₃on theintermediate rings12 corresponding to the midpoints and the points42₂,44₂on the rear end wire ring10₂corresponding to the midpoints are restrained by theprojections18cwhen they move along the generatrices on the taperedsurface18d, with the points41₃,43₃,41₂,43₂corresponding to the dividing points forming forwardly directed peaks and the points42₃,44₃,42₂,44₂corresponding to the midpoints forming the bottoms of forwardly directed valleys, as shown in FIG. 19, so that the intermediate wire rings12 and the rear end wire ring10₂are also folded to take a wavy shape having the same phase as that of the front end wire ring10₁. As the rings10₁and10₂are folded, thebraid members10acircumferentially arranged about the end wire rings10₁,10₂are also folded to take a wavy shape. As the artificial blood vessel A is collapsed, thethorns12a₁are pushed down to extend rearward or forward because of the above-mentioned construction.

Thus, the artificial blood vessel A inserted into the[0084]

connector

18bis introduced into thestraw64 of thecartridge6, as shown in FIG. 20, by pulling thefront pull string20 farther forwardly. Under the condition, thefront pull string20 is untied and pulled at its end so as to be withdrawn from theloops13, and the funneledtube18 is withdrawn from thecartridge6 through therear end portion6bthereof. Consequently, the artificial blood vessel A is contained in thestraw64 of thecartridge6, as shown in FIG. 21, and only thepipe23aof theballoon catheter23 through which thetube2 is passed is exposed outside through therear end portion6bof thecartridge6 with thecheck valve65 opened a little.

On the other hand, the[0085]

catheter

As mentioned above, in accordance with the invention, the artificial blood vessel A is implanted into the affected[0086]

portion

26, and restored to its original shape thereby to effectively prevent occlusion of the affectedportion26 in the blood vessel9. With the above-mentioned collapsing method, the artificial blood vessel A can be collapsed with ease and accuracy. It is difficult to fold the front end wire ring10₁into such a small shape that can be contained in acatheter8 merely by applying non-directional external forces thereto. However, the dividing points41₁,43₁which equally divide the circumference of the front wire ring10₁are pulled forward and the midpoints42₁,44₁between the dividing points41₁,43₁are restrained from moving forward following the dividing points41₁,43₁by a taperedsurface18d, so that the dividing points41₁,43₁form forwardly directed peaks and the midpoints42₁,44₁form the bottoms of forwardly directed valleys with the midpoints42₁,44₁serving as footholds, so that the front end wire ring10₁as a whole takes a regular wavy shape. After the front end wire ring10₁has been folded, as the dividing points41₁,43₁provided on the front end wire ring10₂are farther pulled forward by thefront pull string20, the pulling force is transmitted to the points41₃,43₃on theintermediate rings12 corresponding to the dividing points and the points41₂,43₂on the rear end wire ring10₂corresponding to the dividing points through thetensile cover7, and at the same time the points42₃,44₃on theintermediate rings12 corresponding to the midpoints and the points42₂,44₂on the rear end wire ring10₂corresponding to the midpoints are restrained by the taperedsurface18d, so that the intermediate wire rings12 and the rear end wire ring10₂are also folded to take a wavy shape having the same phase as that of the front end wire ring10₁, thereby to enable the artificial blood vessel A to be collapsed into a small size with ease.

What should especially be referred to is that the method of collapsing the appliance to be implanted in accordance with the invention is characterized by that the end wire rings[0087]10₁,10₂provided at the opposite ends of the artificial blood vessel A are connected by only atubular cover7 which is made of a flexible and tensile sheet; and that the front end wire ring10₂is pulled forward by means of the device B for transporting artificial blood vessels. The conventional method, in which the appliance to be implanted is pushed at the rear end so as to be inserted into a human organ, requires a relatively strong frame mainly of connecting wire rings in order to transmit the force applied to the rear end portion of the appliance to the forward portion thereof. However, the invention is based on the idea of pulling the front end wire ring10₁forward, thereby to make insertion of the appliance easy even though no frame is provided. In addition, thecover7 is transformed into any desired shape as the wire rings10₁,12,10₂are folded, thereby to avoid the mutual interference of thecover7 and the wire rings10₁,12,10₂which would otherwise occur if frames are provided. Therefore, the method of collapsing the appliance in accordance with this invention makes it possible to collapse the whole artificial blood vessel A into a small size with ease by folding each of the wire rings10₁,12,10₂, into a wavy shape.

In this embodiment, in order to collapse the appliance, the[0088]

loops

13 are formed at the dividing points41₁,43₁of the front end wire ring10₁and thefront pull string20 is passed through theloops13 and pulled forward, thereby to make the operation of collapsing the appliance very easy. In particular, the pulling force can effectively be transformed to a collapsing force because the dividing points41₁,43₁are gathered to approach each other by pulling the commonfront pull string20 passed through the pair of

loops

13,13.

In this embodiment, the funneled[0089]

tube

18 whose inner surface is gradually reduced in diameter toward the front end thereof is used to collapse the artificial blood vessel A. As the artificial blood vessel A is inserted into the funneledtube18 deeper, the dividing points41₁,43₁and the midpoints42₁,44₁are gathered to approach each other, thereby to enable the artificial blood vessel A as a whole to be collapsed into a small size. In this embodiment, as resilientlydeformable projections18care formed on the taperedinner surface18dof the funneledtube18 so as to engage with the midpoints42₁,44₁, the midpoints42₁,44₁are pushed to approach each other by the counterforce of the projections13c. A space is formed between the front end wire ring10₁and the funneledtube18 due to theprojections18c, thereby effectively to prevent the artificial blood vessel A from being securely caught in the funneledtube18 due to the sliding resistance which would otherwise be increased if the front end wire ring10₁were in tight contact with the funneledtube18. The same is true with the intermediate wire rings12 and the rear end wire ring10₂.

In this embodiment, the[0090]

flexible braid members

10aare circumferentially arranged on the end wire rings10₁,10₂so as to prevent particularly the front end wire ring10₁from being damaged to cause the artificial blood vessel A to lose its function. In particular, if the front end wire ring10₁is bent beyond its elastic limit, not only does it become difficult for the ring to be restored to its original annular shape but also it becomes impossible to move the ring in thecatheter8 because the bent portion is caught in thecatheter8. However, as thebraid members10aare provided, they diffuse the tension which would otherwise be locally applied to the dividing points41₁,43₁when the dividing points41₁,43₁are strongly pulled, thereby to prevent the dividing points from being bent beyond the elastic limit of the ring10₁. Consequently, thebraid members10aprevent plastic deformation of the front end wire ring10₁, provide the ring with a proper capability of restoring to the annular shape and of traveling smoothly in a catheter, and enable the front end wire ring10₁to be folded into a regular wavy form.

The artificial blood vessel A constructed without a frame as mentioned above properly functions for the intended purpose. The artificial blood vessel A in accordance with the invention is so constructed that the[0091]

cover

7 itself is made of a tensile material and is held by the intermediate wire rings12 at appropriate points thereof and that when the whole artificial blood vessel A is released from the state of being collapsed and each of the wire rings10₁,10₂,12 is resiliently restored to the annular shape, thecover7 is restored to the original proper tubular shape by the wire rings10₁,10₂,12. The conventional appliance having a frame, if put in a bent portion of a human organ, is likely to be deformed flatly because of mutual interference of the component parts. However, the artificial blood vessel A having no frame in this embodiment can be transformed into any desired shape so as to conform to different shapes of human organs.

In this case, as the[0092]

cover

7 is of a sheet woven with warps and wefts, and the warps are made of mono-filament of polyester (about 15 denier), whose stiffness helps keep the shape of thecover7, and the wefts are of multi-filament of polyester (about 50 denier), whose closeness gives the sheet waterproofness, thewhole cover7 is flexible, resistive to axial tension, keeps its tubular shape by itself, and can prevent leakage of blood.

As the sheet of the[0093]

cover

7 is in the form of bellows, the whole artificial blood vessel A is easily bendable so that the condition of the artificial blood vessel A implanted into a human organ is improved. As the restraining strings14 bridge the end wire rings10₁,10₂, the bellows can be prevented from stretching beyond the limit to become flat.

In this embodiment, as the[0094]

flexible braid members

10aare circumferentially arranged on the end wire rings10₁,10₂of the artificial blood vessel A, the inner wall of a human organ can be prevented from being damaged by direct contact with the end wire rings10₁,10₂in addition to the advantage that the front end wire ring10₁can be prevented from being plastically deformed when folded into a small size as mentioned above. Thebraid members10aalso help seal both ends of the implanted artificial blood vessel A tightly to the inner wall of a human body, thereby to effectively prevent leakage of blood through the ends of the artificial blood vessel A when implanted.

As the[0095]

thorns

12a₁project from the intermediate wire rings12, they stick into the inner wall of a human organ to be embedded therein so that the whole artificial blood vessel A is fixed to the human organ. Therefore, after the artificial blood vessel A has been implanted in the human organ, thethorns12a₁effectively prevent displacement of the artificial blood vessel A, which may cause the vessel A to be carried by blood flow downstream in the blood vessel. As each of thethorns12a₁is formed by curving a wire into a loop, crossing both end portions of the wire, and fixing the crossed parts with a string or the like, thethorns12a₁can be formed with ease and remain reliable in use for a long time, even though the intermediate wire rings12 are made of a material which is difficult to weld.

On the other hand, by using the device C for introducing artificial blood vessels in accordance with the invention, the artificial blood vessel A can be smoothly introduced into the[0096]

catheter

The invention is not limited to the above-mentioned embodiments. For example, in the above embodiment, the front end wire ring[0097]10₁has its circumference divided into two equal arcs to set two dividing points41₁,43₁and the two midpoints42₁,44₁. As shown in FIG. 28, four dividing points141₁,143₁,145₁,147₁and four midpoints142₁,144₁,146₁,148₁may be set by quadrisecting a front end wire ring110₁. As shown in FIG. 29, three dividing points241₁,243₁,245₁and three midpoints242₁,244₁,246₁may be set by trisecting a front end wire ring210₁.

In the above embodiment, the device B for transporting artificial blood vessels is provided with a pair of[0098]

strings

4 withloop portions4a. Thestrings4 need not always be provided in a pair. However, the strings provided in a pair are effective because a balanced pulling force can be applied to the artificial blood vessel A. Theloop portions4amay be twisted as a whole.

As the[0099]

balloon catheter

23 is used in the above embodiment, the device B for transporting artificial blood vessels is incorporated into theballoon catheter23. If theballoon catheter23 is unnecessary, the artificial blood vessel A may be introduced into or taken out of the catheter by directly operating thetube2 of the device B for transporting artificial blood vessels.

In such a case, it is effective to use both a method of and a device for pulling the artificial blood vessel A back to the proper position after it has been released.[0101]

FIGS. 30 and 31 show a device D for helping restoration for the above purpose, which comprises a pair of[0102]

tubes

By using these devices jointly, a proper distance between the front end wire ring[0103]10₁and the rear end wire ring10₂can always be maintained. Therefore, it is possible to prevent the artificial blood vessel A from being shrunk longitudinally to deform its proper shape, and to complete insertion of theballoon catheter23 and adjustment of the position of the artificial blood vessel A quickly and accurately.

The device for helping restoration of the appliance to be implanted can be of a construction shown in FIG. 33. The device is provided near the[0104]

side window

101 of thetube102 with a pair ofstrings104 each of which has its front end portion formed into a loop. The loop portion of eachstring104 is passed through a pair ofrear loops13aand hooked by thewire103 like the device B for transporting artificial blood vessels. Thetube102 also is contained in the pipe24aof theballoon catheter23 and transported like the above-mentionedtube102.

In the above-mentioned embodiments, in some cases the[0105]

balloon catheter

23 is not used. In such cases thetube102 is to be detachably connected with the device for transporting the artificial blood vessel so that the tube and the device can be transported as a unit.

The appliance according to the present invention, especially when used as an artificial blood vessel, has various effects or advantages such that (1) the appliance has improved liquid proofness and positional stability or fixedness at the position where it has been implanted, and (2) that it has improved implanted condition with resulting reduction of adverse influences otherwise caused by implantation of such artificial appliances in a human body. Reasons for the improvement of the liquid proofness and fixedness will be explained with reference to FIGS. 34 and 35.[0106]

When the artificial blood vessel has been released in a blood vessel adjacent to an affected portion thereof where an aortic aneurysm exists, the wire rings p[0107]1 arranged outside the cover p2 are brought into direct contact with the inner wall surface p3 of the blood vessel due to its own restoring force without the cover p2 intervening. On the contrary, if the wire rings were arranged inside the cover q2 as shown at q1 in FIG. 35, the cover would intervene between the wire rings q1 and the inner wall surface q3 of the blood vessel to effect an indirect surface contact therebetween, with the resilient restoring force of the rings q1 being dissipated by the intervening cover.

In FIG. 34 the wire rings p[0108]1 of the artificial blood vessel of the present invention directly contact the inner wall surface p3 of the blood vessel without the cover p2 intervening, thereby to effect a linear contact rather than a surface contact therebetween, so that the wire rings p1 exercise a pressing force onto localized areas on the inner wall surface p3 of the blood vessel. This effects a good sealed condition between the wire rings and the inner wall of the blood vessel.

Since the wire rings p[0109]1 are arranged outside the cover p2, the blood p flowing through the cover p2 exerts a fluid pressure as shown at p5 from inside the cover to expand it, and the expanding force of the cover is likely to be concentrated on the wire rings p1 to expand them radially outwardly, so that the expanding force added to the resilient restoring force of the wire rings increases the sealing effect between the implanted artificial blood vessel and the inner wall surface p3 of the blood vessel. In FIG. 35, the pressure q5 of the blood q4 flowing through the cover q2 acts on the cover q2 from inside it but scarcely acts on the wire rings q1 to expand them radially outwardly, so that the sealing effect of the wire rings q1 on the inner wall surface q3 of the blood vessel is scarcely increased.

The artificial blood vessel of the present invention is able to provide an effective seal at the wire rings contacting the inner wall of the blood vessel thereby to prevent leakage of blood through a gap therebetween, to provide an improved liquid tightness between the implanted artificial blood vessel and the adjacent portions of the blood vessel thereby to prevent leaking blood, if any, from reaching the affected part of the blood vessel such as an aortic aneurysm, and to provide improved positional stability of the implanted artificial blood vessel by effectively preventing the wire rings from slipping on the inner wall of the blood vessel and consequently the whole of the implanted artificial blood vessel from being displaced or moved away from the position where it must stay.[0110]

The above effects are marked especially where the intermediate wire rings contact the inner wall surface of the blood vessel. Unlike the end wire rings, the intermediate wire rings are fixed to the cover at positions other than the opposite ends of the cover, so that the expanding force of the cover caused by the blood pressure inside it acts as a whole to uniformly expand the intermediate wire rings radially outwardly, and the total force acting on the intermediate wire rings is greater than that acting on the opposite end wire rings. Therefore, even if blood should enter the space between the end wire rings and the inner wall surface of the blood vessel, the intermediate wire rings contact the inner wall surface of the blood vessel at a greater pressure and more tightly than the end wires so as to efficiently prevent the entering blood from reaching the aneurysm. Thus, the invention provides a double or multiple-stage sealing system.[0111]

In one conventional type of artificial blood vessel (not shown) in which the opposite end wire rings are connected by an elastic wire framework, the support rod exerts a force on the wire rings to prevent the resilient restoration thereof, so that the artificial blood vessel has a lower adhesiveness and positional stability of the wire rings to the inner wall of the blood vessel than in the prevent invention (which is free of an elastic wire framework extending between and connecting the end wire rings) and it is difficult to prevent leakage of blood without fail.[0112]

Reasons for the improved condition of the implanted blood vessel and reduction of adverse influences caused by the implantation of the artificial blood vessel of the present invention will now be described.[0113]

The human body has a characteristic such that when a foreign body enters a blood vessel, the intima of the blood vessel covers or envelopes the foreign body to assimilate it. In particular, when an artificial blood vessel has been implanted in a blood vessel to be treated, the intima of the blood vessel expands over the inner wall surface of the implanted artificial blood vessel to cover and assimilate it. In the arrangement of FIG. 35, in which the wire rings are disposed inside the cover, the projections provided by the rings q[0114]1 on the inner surface of the cover q2 become an obstacle to smooth, uniform expansion of the intima from the adjoining blood vessel. In other words, the expansion of the intima is likely to be impeded by the projections and it takes a considerably long time for the intima to uniformly cover the implanted artificial blood vessel, in which a thrombus is likely to be formed in the course of expansion of the intima. As the thrombus grows, the blood vessel becomes constricted, and there is danger of the thrombus coming off to be carried over to a capillary vessel and cause necrosis in the adjacent cells.

In accordance with the present invention, the wire rings p[0115]1 are provided outside the cover p2, the inner surface of which is continuously smooth from one end thereof to the other, so that the intima of the blood vessel will expand over the inner surface of the cover of the implanted artificial blood vessel smoothly and at an efficient speed. This means that the implanted artificial blood vessel is easily assimilated into the tissue of the inner wall of the blood vessel, with resulting reduction of the danger of a thrombus being formed to cause serious damage, such as necrosis, and realization of a long, stable fixed condition of the implanted artificial blood vessel.

In the previously described conventional type of artificial blood vessel including an elastic wire framework inside the cover, the framework impedes expansion of the intima as in the arrangement of FIG. 35 so that no such effects or advantages as in the present invention can be expected.[0116]

In accordance with the invention, if the inner pressure of the cover of the implanted artificial blood vessel should increase to an abnormally high level, the wire rings provided outside the cover can effectively prevent occurrence of serious situations such as rupture of the cover to cause profuse bleeding.[0117]

Further advantages provided by preferred features of the invention are described below.[0118]

Relatively hard, stiff thread must be used to form an artificial blood vessel as a concrete, solid structure if it is not to be supported by an elastic wire frame. If such stiff thread were used in the whole of the cover of the artificial blood vessel, however, the cover would become too bulky and stiff to be smoothly introduced into a blood vessel.[0119]

In accordance with the invention, the warps with which the cover is woven are preferably made of mono-filament so as to keep the cover sufficiently rigid as a structure and make it possible to fold the artificial blood vessel into a less bulky size than otherwise. Since the artificial blood vessel of this type is usually introduced into a relatively thin blood vessel such as the femoral blood vessels, the fact that the artificial blood vessel of the present invention can be folded into a small size is an important factor to enable successful implantation of the artificial blood vessel. In addition, since the wefts of the cover are preferably made of multifilament, when the intima of the blood vessel expands over the implanted artificial blood vessel to assimilate it, the intima is likely to enter the spaces among the filament fibers to effect a stable fixed state of the implanted artificial blood vessel. Due to entanglement of the fibers of the wefts the cover is finely meshed and highly liquid proof.[0120]

When an artificial blood vessel is to be implanted in a curved portion of a blood vessel, that portion of the wall of the artificial blood vessel which is to lie along the outer lateral side of the wall of the curved blood vessel, which has a relatively large radius of curvature, must be stretched or lengthened while the opposite side portion of the wall of the artificial blood vessel which is to lie along the opposite inner lateral side of the wall of the curved blood vessel, which has a relatively small radius of curvature, must be shrunk or shortened so that the implanted artificial blood vessel may be properly positioned with the openings of the opposite end wire rings being held perpendicularly to the wall of the blood vessel. This is readily achieved in accordance with the present invention by forming the cover of the artificial blood vessel as a bellows. With implanted artificial blood vessels not formed into bellows, it is difficult for the implanted artificial blood vessel to be transformed in such a manner and to be brought into close contact with the wall of the blood vessel particularly at that portion thereof which has a relatively small radius of curvature.[0121]

This is particularly true with that type of artificial blood vessel which contains a wire frame, which is highly resistive to curving or transformation of the artificial blood vessel and consequently makes it extremely difficult to effect proper implantation thereof. Moreover, there is a danger of the opposite ends of the frame sticking into the wall of the blood vessel to break it. With the conventional type of artificial blood vessel with a wire framework or without bellows it is quite difficult to accomplish a proper implanted condition, and leakage is likely to occur between the blood vessel and the implanted artificial blood vessel in loose contact therewith. Due to the loose contact or low positional stability the implanted artificial blood vessel is likely to be pushed away by the blood flow.[0122]

The artificial blood vessel of the invention, having the cover formed into bellows, can easily conform to the curvature of the blood vessel in which it is to be implanted so as to be kept in close contact therewith at a fixed condition. In addition, due to the bellows, it is possible to change the axial length of the artificial blood vessel within a certain range, so that after the artificial blood vessel has been implanted, it may be axially adjusted so as to accomplish the most appropriate implanted condition. Due to the bellows, it is also possible to lengthen or shorten the artificial blood vessel so that it can be reduced in size for easier introduction into a catheter.[0123]

The above is not possible with the conventional type of artificial blood vessel, in which the wire frame connecting the opposite end rings is detrimental to transformation of the artificial blood vessel.[0124]

In the artificial blood vessel of the present invention, all the wire rings, including the end wire rings, are arranged outside the cover. There is a risk that the exposed end wire rings may pierce the wall of the blood vessel to cause bleeding. To minimize this risk, in accordance with a preferred aspect of the invention, a protective material covering the end rings functions as a buffer against the inner wall of the blood vessel.[0125]

The thorns of the inventive artificial blood vessel preferably project from the circumference of at least one of the wire rings. Since the wire rings are outside the cover, there is no danger of the thorns piercing the cover, so that it is possible to fix the artificial blood vessel onto the inner wall of a blood vessel with good liquid proofness and positional stability.[0126]

Since the artificial blood vessel of the present invention has no supporting frame or rod, the provision of the rear pull means (see, e.g.,[0127]

rear loops

13ain FIG. 30) makes it possible to freely adjust the length of the artificial blood vessel after it has been released from the catheter at a position in a blood vessel where it is to be implanted. A blood vessel has branches such as the aortic arch having the brachiocephalic trunk branching therefrom, and the artificial blood vessel must be positioned accurately at the required position so as not to block those branches which are not to be blocked. Erroneous blocking of such branches is likely to result in a critical damage. With the rear pull means accurate positioning of the artificial blood vessel is facilitated.

FIG. 36 shows a modified embodiment of the invention, in which the end wire rings W[0128]1 comprise a plurality, e.g., four, wire elements W2 bound together, and in a similar manner the intermediate wire rings W3 comprise a plurality, e.g., four, elements W4 bound together. The wire elements W2 and W4 are preferably made of nickel-titanium alloy. With the arrangement, the wire rings W1 and W3 have both sufficient flexibility and strength so that there is little danger of the wire rings injuring the blood vessel, and they are able to move in response to the pulsation of the blood vessel, and endure the repeated load caused thereby, for a long time. Should any of the wire elements be broken, the rings would not immediately do harm to the human body.

As the wire rings comprise a bundle of wire elements, they are more flexible than a wire ring which comprises a single wire element having a high strength. The rings can softly contact the inner wall of the blood vessel while maintaining a sufficient strength. Rigid wire rings might stick the inner wall of a human blood vessel and break it. Since the wire rings of the artificial blood vessel of the present invention are flexible, there is less danger of the wire rings breaking the wall of the blood vessel, and the flexibility of the material enables proper restoration of the folded wire rings. Since the human blood vessel pulsates, the implanted artificial blood vessel receives from the pulsating blood vessel a repeated load for a long time. The wire rings of the invention made of a plurality of wire elements are flexible so as to move in response to the pulsation and more resistive to the repeated load than if they were made of a single strong wire element. Breakage of one of the wire elements does not result in immediate failure of the whole wire ring and consequently the implanted artificial blood vessel.[0129]

FIG. 38 shows a modified embodiment of the invention, in which each of the intermediate wire rings[0130]1012 is provided with a pair ofthorns1010 shaped like a Japanese Katakana letter “
” (a squared U-shape) in transverse section. Thethorns1010 are fixed at the diametrically opposite positions of thewire ring1012 by means of athread1011 so as to be directed radially outwardly. Since the intermediate wire rings1012 are provided outside thecover1013, the thorns thereon do not pierce the cover, so that the artificial blood vessel may be kept liquid tight. In FIG. 39 thethorns1020 are L-shaped in transverse section and fixed to theintermediate wire ring1022 by means of athread1021, similar to thethorns1010 in FIG. 38.
Since all the wire rings are arranged outside the cover, the thorns are provided on the rings without piercing the sheet of the cover. Thus, the artificial blood vessel can be fixed at a required position in a blood vessel without influencing the liquid tightness of the implanted artificial blood vessel.[0131]
Nickel-titanium alloy is highly flexible and resilient. With the wire rings of the invention made of this alloy the artificial blood vessel can be folded into a small size when it is inserted into a catheter and restored to its original size without fail when it is released at the target position. Even if the implanted artificial blood vessel receives a pulsating load caused by the pulsation of the blood vessel via its wall for a long time, the flexible, resilient nickel-titanium alloy enables the wire rings to move in response to the pulsation without causing damage to the implanted artificial blood vessel. The end wire rings which comprise a bundle of wire elements made of nickel-titanium alloy have increased strength and flexibility and reduced probability of being broken. The manners in which the thorns are formed and fixed to the wire rings, as shown in FIGS. 38 and 39 and described above, are effective especially when the wire rings are made of nickel-titanium alloy which is hard to weld.[0132]
FIG. 37 schematically shows the material or sheet of an artificial[0133]blood vessel cover1001 expanded and enlarged. The sheet is woven with warps ofmonofilament1002 and wefts of multi-filament1003. In particular, the mono-filament1002 may comprise about 12- denier thick polyester fiber. The multi-filament1003 comprises a twist of an about 52-denier bundle of ultra finemicro fibers1003aof polyester and an about 10-denier reinforcing thread1003bof Vectran (a trade name of thermotropic liquid crystal). The resulting cover of the artificial blood vessel has a combined strength of the mono-filament1002 and the reinforcingthread1003band the flexibility, liquid proofness and fixability to the inner wall of the blood vessel of the ultra finemicro fibers1003aof the multi-filament1003. Since the artificial blood vessel must endure a high blood pressure for as long a time as decades of years, it is essential that it should have a sufficient strength in the radial direction. The above-mentioned Vectran provides not only as high a strength as the conventional artificial blood vessel used in the surgical replacement of blood vessels, but also a flexibility to enable easy folding of the artificial blood vessel of the invention.
Possible Applications in Industry[0134]
As mentioned above, the method of collapsing the appliance to be implanted in accordance with the invention is useful to fold the wire rings, which are components of the appliance, into small, regular wavy shapes of the same phase, thereby to collapse the appliance into a small size. The appliance to be implanted in accordance with the invention can be implanted into a target position without fail and has an appropriate construction so as not to hinder the operation of collapsing. The device for introducing the appliance to be implanted into the catheter is useful to introduce the appliance into the catheter without bleeding.[0135]

Claims

1. An appliance to be implanted wherein a plurality of elastically foldable wire rings are arranged spaced apart from each other and are interconnected by a tubular cover formed with a flexible tensile sheet, characterized by that said wire rings alone are made of metal and all remaining parts of said appliance are made of nonmetal material which is flexibly deformable to follow a folding movement of the wire rings.

2. The appliance to be implanted described inclaim 1, wherein said wire rings comprise a pair of end wire rings, each of which is discretely arranged and interconnected by said cover, and an intermediate wire ring which is arranged between the end wire rings and fixed to the cover at specified positions on the circumference thereof.

3. The appliance to be implanted described inclaim 1, wherein said wire rings are mainly made of Ti—Ni alloy.

4. The appliance to be implanted described inclaim 2, wherein said wire rings are mainly made of Ti—Ni alloy.