WO1993017747A1

WO1993017747A1 - Apparatus and method for retaining a catheter in a blood vessel in a fixed position

Info

Publication number: WO1993017747A1
Application number: PCT/US1993/001866
Authority: WO
Inventors: Thomas R. Kirkman
Original assignee: Kirkman Thomas R
Priority date: 1992-03-02
Filing date: 1993-03-02
Publication date: 1993-09-16
Also published as: CA2131329A1

Abstract

A method and apparatus for retaining a catheter tip in a fixed position within a blood flow and preventing it from contacting a blood vessel wall. The apparatus includes a tip retainer at the distal end of the catheter that anchors the tip of the catheter within the blood vessel. The catheter tip is retained within the blood vessel spaced from the wall to ensure that it does not contact the wall of the blood vessel. This reduces damage to the blood vessel caused by chronic movement and contact between the catheter tip and the wall of the blood vessel. In one embodiment, the tip retainer includes a prong that penetrate the wall of the blood vessel, thus preventing the catheter tip from moving longitudinally within the blood vessel. In alternative embodiments, the tip retainer contacts the wall but does not penetrate the wall.

Description

APPARATUS AND METHOD FOR RETAINING A CATHETER IN A BLOOD VESSEL IN A FIXED POSITION

Cross-Reference to Related Application

This patent application is a continuation-in- part of U.S. Serial No. 07/844,715, filed March 2, 1992 by Thomas R. Kirkman. This application contains subject matter related to an application titled "APPARATUS AND METHOD FOR CONSTRUCTING A TIP RETAINER FOR A CATHETER, RETAINING A CATHETER IN A BLOOD VESSEL IN A FIXED POSITION, AND POSITIONING A CATHETER WITHIN A BLOOD VESSEL" by Thomas R. Kirkman, Margo L. Gisselberg, Timothy Alan Abrahamson, and Pauline Young filed concurrently herewith.

Technical Field

This invention relates to intravascular catheters that have means for reducing stenosis and thrombosis at the tip of the catheter.

Background of the Invention

The treatment of a number of medical conditions requires the placement of catheters within a patient's blood vessel for an extended period of time. These long- term applications include blood access for hemodialysis, chemotherapy, parental nutrition, blood transfusions and blood sampling. Vascular access with catheters was first introduced more than 20 years ago. With the advent of soft, flexible silicone double lumen catheters, both acute and chronic hemodialysis became a routine procedure. Although subclavian dialysis catheters are easily inserted and well tolerated, catheter lifespan averages about three months. This is of great concern to patients on maintenance dialysis. It is well known in the medical field that chronic placement of a catheter in a patient's blood vessel often results in catheter failure due to aspiration of the blood vessel wall into the tip of the catheter, clot or thrombus formation at the tip of the catheter, or stenosis around the tip of the catheter. A catheter failure resulting from one or more of these mechanisms is evidenced by an inability to aspirate and/or infuse fluid through the catheter, generally referred to as catheter occlusion. Typically, catheter occlusions caused by aspiration of the blood vessel wall or clot formation at the catheter tip may be resolved by repositioning the catheter tip or infusing an ithrombotic agents.

Stenosis is a narrowing of the blood vessel lumen as seen in a venogram and, in general, can be due to either the formation of a thrombus within the blood vessel or a thickening of the blood vessel wall. The generally accepted view is that stenosis around the tip of a catheter implanted within a blood vessel is due to the formation of a thrombus resulting from a biochemical reaction to the introduction of a foreign material into the blood vessel. Previous attempts to prevent catheter occlusion have centered around thromboresistant coatings on the catheter surface in order to prevent the biochemical reaction of the patient's blood to the material of which the catheter is formed.

Prior art related to the present invention deals with the placement of stents within a diseased blood vessel to treat the problems associated with stenosis. Stents range from simple wire meshes used in U.S. Patent No. 4,800,882, to a canister made of hydrophilic plastic which expands upon placement in a blood vessel as in U.S. Patent No. 4,434,797. Stents are typically secured to a deployment catheter for insertion into the patient's blood vessel via a percutaneous procedure. Surgical placement of these stents is achieved by feeding the catheter from a distant site, e.g., a percutaneous puncture into the femoral artery, to the stenosis target. The deployment catheter is then removed, leaving the stent within the blood vessel lumen.

Prior publications on the subject of mounting devices in the blood stream include "Registration of Phoric Changes of Blood Flow by Means of a Catheter-Type Flowmeter," by Heinz Pieper printed in The Review of Scientific Instrument .29_.(11) :965-967, November 1958, and U.S. Patent Nos. 4,425,908; 4,936,823; 4,813,930; 5,135,517; and 4,654,028. However, none of these address and solve the problems presented in the field of the present invention.

Summary of the Invention The present invention is directed to an intravascular catheter that has means to retain the tip of the catheter within a blood vessel lumen such that the tip of the catheter is prevented from contacting the wall of the blood vessel. This prevents repeated impact between the catheter tip and blood vessel wall. This reduces denudation and damage to the endothelial and smooth muscle cells that line the blood vessel wall. By reducing damage to these cells, the invention allows for the cells to continue to release the bioactive molecules that normally prevent and reverse the thrombotic and coagulation processes in blood.

Most vascular injury research is in the area of arterial injury; however, the mechanism that regulates cellular growth in injured veins is not known. It is a reasonable assumption that the "response to injury hypotheses" proposed in Ross, R. , Glomset, J.A. , "The Pathogenesis of Atherosclerosis," N. Enql. J. Med. 295;369-77 , 1976, can also be applied to injuries in the venous system. This hypothesis is based on the following observations after injury to the lumen of the blood vessel: (1) platelet adherence and degranulation precedes smooth muscle cell proliferation; (2) intimal thickening in injured arteries of thrombocytopenic animals is reduced; (3) platelet granules contain potent mitogens for cultured smooth muscle cells. Based upon these observations, Ross and Glomset suggested that a high local concentration of growth factors, particularly platelet- derived growth factors released from degranulating platelets could stimulate smooth muscle cell proliferation. Their hypothesis is based on a relationship between the thrombosis that occurs within ah injured vessel and the subsequent cell growth associated with repair of the injured vessel wall.

Normally, hemostasis results from a delicate balance between clot-stimulating and clot-inhibiting processes. Endothelial cells and smooth muscle cells in a normal blood vessel are probably the main source of clot regulating factors such as heparin or heparan sulfate. These heparin and heparin-like molecules prevent the adherence of blood proteins and platelets to the surface of a normal blood vessel. Since the endothelium is a critical component of hemostasis control, localized injury and denudation of the endothelium by repeated impact with a catheter tip results in a shift of this delicate balance toward clot and thrombus formation within a denuded region. This clot formation may occur even if the catheter is composed of a material that normally would not create a reaction in the body.

Physical damage to the wall of the blood vessel affects the release and production of a number of growth- stimulating factors such as basic fibroblast growth factor and platelet-derived growth factor. These growth factors help to overcome the antiproliferative activities of the heparan sulfates, thus helping to initiate cellular proliferation and the migration of smooth muscle cells that ultimately leads to stenosis. Therefore, preventing physical damage to the endothelial cell lining of the blood vessel wall reduced stenosis, as well as thrombosis, at the tip of the catheter. Prior art catheters allow chronic and repeated contact between the catheter tip and the wall of the blood vessel, resulting in damage to the blood vessel as discussed previously. The tip of the catheter may repeatedly bump into different locations inside the blood vessel, or the same location a number of different times, causing a reaction, or worse, damage to the vessel wall. Further damage is caused by the aspiration of the blood vessel wall into the catheter lumen. This occurs when blood is withdrawn through the catheter, such as in the performance of dialysis.

The present invention solves the problems by approaching them from an entirely different view than the prior art attempts; namely, by preventing repeated impact between the catheter tip and the blood vessel wall. The inventors have found that repeated impact with the vessel wall and a catheter tip, even if it is a soft tip, causes a physical reaction in the blood vessel wall. This reaction occurs because of repeated contact between the catheter tip and the wall of the blood vessel even if the catheter tip is soft, and even if the tip is properly coated with antithrombotic agents. This catheter-induced reaction in the blood vessel wall may lead to the formation of a mural thrombus and/or abnormal cellular proliferation within the blood vessel wall, thus resulting in stenosis and catheter occlusion. Prior art efforts to prevent catheter occlusion through the use of thromboresistant coatings do not alleviate the physical reaction that the catheter tip may cause to the blood vessel wall by repeated impact. Therefore, chronic placement of a catheter in a patient still results in catheter occlusion in the majority of cases.

In accordance with aspects of the present invention, chronic contact between and aspiration of the blood vessel wall by the catheter tip is prevented. This reduces damage to the endothelial cells lining the blood vessel, thus reducing catheter occlusion due to stenosis and thrombosis. In addition, the occurrence of catheter occlusion resulting from aspiration of the vessel wall will be reduced.

The present invention includes, in one embodiment, an antistenotic intravascular catheter for insertion into a blood vessel. The catheter includes a tip retainer, located at the distal end of the catheter, for retaining the tip of the catheter within the blood vessel and preventing the catheter from contacting the wall of the blood vessel. The tip retainer positions the tip of the catheter within the blood vessel without substantially obstructing fluid flow through the blood vessel. The catheter also includes an internal passageway for permitting fluids to pass through the catheter. Numerous alternative embodiments are disclosed for the tip retainer. In some embodiments, the tip retainer does not penetrate the wall of the blood vessel. In one embodiment, the tip retainer includes a penetrating member that does penetrate the blood vessel wall. In all embodiments, the tip of the catheter is retained in the blood vessel by anchoring the tip with respect to the wall of the blood vessel.

In one preferred embodiment, the tip retainer is two or more loops of wire that flex outward and contact the wall. The loops do not penetrate the wall tissue, but do anchor the tip in a fixed position in the blood vessel, retaining it in the blood flow and preventing contact of the tip with the vessel walls.

In a further embodiment the tip retainer includes fletching to anchor the catheter tip in the blood vessel. Alternatively, the tip retainer is a plurality of single straight wires that are prestressed to flex outward or straight wires with loops on the end.

In accordance with one embodiment of the invention, the tip retainer includes penetration means for penetrating the wall of the blood vessel and preventing the tip of the catheter from moving longitudinally within the blood vessel. In this embodiment, the tip includes a loop for limiting the depth of penetration.

In one embodiment of the invention, a plurality of members run from the proximal end of the catheter to the distal end where they extend radially outward until they contact the wall of the blood vessel. In this embodiment, the catheter includes withdrawal means for withdrawing the positioning means into the catheter such that the positioning means is prevented from damaging the wall of the blood vessel when the catheter is withdrawn from the blood vessel. The withdrawal means includes a guideway that runs from the proximal end of the catheter to the distal end of the catheter. The positioning means extends from the proximal end to the distal end of the catheter within the guideway.

According to one aspect of the present invention, a method for reducing catheter failure due to stenosis or thrombosis at a catheter tip is provided. Positioning means is attached to the catheter tip, and the catheter tip and attached positioning means are placed within the blood vessel without substantially obstructing fluid flow through the blood vessel and such that the catheter tip is prevented from contacting the blood vessel wall.

Brief Description of the Drawings

Figure 1 is a perspective view of a first preferred embodiment of the antistenotic intravascular catheter of this invention. Figure 2A is an enlarged perspective view of a first preferred embodiment of the tip retainer as deployed.

Figure 2B is an enlarged perspective view of the preferred embodiment of Figure 2A showing the tip retainer after it has been partially withdrawn into the guide tube. Figure 3 is an enlarged perspective view of the distal end of a second embodiment of the tip retainer. Figure 4 is an enlarged perspective view of an alternative embodiment for connecting the tip retainer to the catheter.

Figure 5 is an enlarged perspective view of an alternative embodiment of the tip retainer.

Figure 6 is an enlarged perspective view of an alternative embodiment of the tip retainer.

Figure 7 is an enlarged perspective view of a further alternative embodiment of the tip retainer. Figure 8 is an enlarged perspective view of a further alternative embodiment of the tip retainer.

Figure 9 is an enlarged perspective view of a further alternative embodiment of the tip retainer.

Figure 10A is an enlarged perspective view of a further alternative embodiment of the tip retainer.

Figure 10B is an end view of the device of Figure 10A.

Figure 11 is a perspective view of a further alternative embodiment of the catheter showing an alternative embodiment of the tip retainer.

Figure 12 is an enlarged view of a further alternative embodiment of the tip retainer.

Figure 13 is an enlarged view of a further alternative embodiment of the tip retainer. Figure 14 is an enlarged view of a further alternative embodiment of the tip retainer.

Figure 15 is an enlarged • view of a further alternative embodiment of the tip retainer.

Figure 16 is an enlarged view of a further alternative embodiment of the tip retainer.

Figure 17A is a top view of the embodiment of Figure 15 using fletching attached straight as the tip retainer.

Figure 17B is a top view of an alternative embodiment of Figure 17A.

Figure 18 is an end view of the embodiment of Figure 17A as installed within a large blood vessel. Figure 19 is an end view of the embodiment of Figure 17A as installed in a small blood vessel.

Figure 20 is a top view of an alternative embodiment using fletching attached at a cant as the tip retainer.

Figure 21 is an end view of the embodiment of Figure 20.

Figures 22-24 illustrate a further alternative embodiment for placing the catheter having the tip retainer on the end thereof within a blood vessel.

Detailed Description of the Invention

Figure 1 is a perspective view of a first preferred embodiment of an antistenotic intravascular catheter 2 of the present invention. Catheter 2 includes a tube 4 formed from a material suitable for placement i a blood vessel, such as silicone rubber. The catheter includes a Dacron® anchor cuff 14 for anchoring the catheter subcutaneously. An in-line clamp 16, for preventing fluid flow, is placed on tube 4 adjacent th proximal end 6. The proximal end 6 of the catheter i attached to a luer-lock adapter 18 which is sealed b threading an injection sealing cap 20 onto the adapter i a manner known in the art. According to one aspect of one embodiment of th present invention, the intravascular catheter 2 includes tip retainer 9 for retaining the distal end 8 in th bloodstream and preventing the tip of the catheter fro contacting the wall of a blood vessel 30. In a first embodiment, the tip retainer includes four wires 12 positioned within the catheter wal and extending along the length of the catheter, from th distal end of the catheter towards the proximal end 6 o the catheter. This ensures that the proximal ends 34 o the wires 12 will be accessible outside the patient's bod after the catheter has been implanted in a blood vesse 30. The proximal ends 34 of the wires 12 are secured t the catheter by an appropriate method such as heat shrink Teflon® tubing 32 that is placed over the wires and shrunk in place. The proximal end of the wires could also be secured through the use of a band integrally formed in the tube 4 or other structures which prevent movement of the proximal end 34 of the wires 12 until they are controlled by a physician.

The wires 12 are preferably made of or coated with a material which does not cause an adverse reaction when placed in the patient's body. Suitable materials include stainless steel, titanium, some plastics such as nylon, some composite materials, and Teflon®-coated wires, including Teflon®-coated stainless steel. Depending upon the application, the wires 12 have a diameter ranging from .0025 to .076 cm. In some applications, it may be desirable to treat the wires 12 with an antithrombotic coating, for example, dipping the wires in a coating or applying a coating through plasma polymerization in order to reduce blood clotting on the wires. Plasma polymerization is explained in detail in Yeh et al. , "Blood compatibility of surfaces modified by plasma polymerization," Journal of Biomedical Materials Research 22_.:795-818, 1988.

As shown in Figure 2A, in one embodiment, the wires 12 extend along the length of the catheter through guideways 38 and exit the guideways at openings 40. The guideways 38 protect the wires 12 while also maintaining proper positioning between the individual wires. Guideways 38 and wires 12 are preferably extruded as an integral part of tube 4, or alternatively are extruded individually and are later attached onto the outside of the tube 4 or inserted into tube 4. In the embodiment shown, four wires 12 are used, however, a different number of wires, such as three or five, could be used, depending upon the application.

Preferably, the four wires 12 are equally spaced circumferentially located around the distal end 8 such 11

that they serve as a tip retainer 9 and positioning mean for positioning the tip of the catheter within the bloo vessel 30. The tip retainer ensures that the tip of th catheter does not contact the inner wall 27 of the bloo vessel 30. The thin wires 12 restrict movement of the ti of the catheter to prevent it from hitting the inne wall 27 while not substantially obstructing the fluid flo through the blood vessel and not causing clots.

In the embodiment illustrated in Figure 2A, loop 25 is formed near the end of each wire 12, and short penetration prong 26 is formed that extend outwardly from each loop. The prongs 26 penetrate th wall of the blood vessel 30. Each prong 26 is sized an extends from loop 25 such that the prong penetrates th wall of the blood vessel to a depth in the range of .1 t 3 mm after placement within the blood vessel. Th loops 25 serve as limiting means for limiting the depth t which the prongs 26 penetrate. This prevents the tip 8 o the catheter from moving longitudinally within the bloo vessel 30.

Other structures could also be used to perfor the penetration and limiting functions. As an example instead of forming a loop near the end of each wire, a enlarged section such as thickening of the wire ban welded or bonded to the wire or a bend near the tip of th wire could be used.

The distal end of the catheter is retaine within the blood vessel and prevented from contacting th endothelial cells lining the blood vessel by rubbing o aspirating the wall of the blood vessel by the ti retainer 9. Although penetration of the wall 27 by prong 26 causes some damage to the blood vessel, the damag caused is not significant in comparison to the damage tha would be caused by repeated impact or chronic rubbing o the tip 8 or by aspiration of the inner wall 27, which ma occur with prior art catheter designs. By reducing th contact with and damage to the endothelial cells, th present invention allows for the continued release of anticoagulant molecules by the endothelial cells in the vicinity of the distal end of the catheter as explained previously. Correspondingly, there is a reduction in thrombosis and/or stenosis of the blood vessel lumen at the distal end of the catheter and thus reduced catheter occlusion.

The antistenotic intravascular catheter 2 (Figure 1) may be placed within the blood vessel 30 using a sheath introducer of the type shown in more detail in Figures 22-r25, an embodiment of which is explained with respect to those Figures. In one embodiment, a tubular introduction sheath is inserted within a patient's blood vessel, with the sheath terminating at the point within the blood vessel where the distal end 8 of the catheter is to be placed. The catheter 2 is then placed within the introduction sheath with the wires temporarily constrained along the catheter's longitudinal axis by the sheath. The catheter is then pushed down the sheath until the distal end 8 of the catheter exits the introduction sheath. As the distal end of the catheter exits the introduction sheath, the wires 12 spread radially to contact and penetrate the blood vessel wall as shown in Figure 2A. After placement of the catheter into the blood vessel, the introduction sheath is removed from the blood vessel.

Another technique for placing the inventive catheter tip retainer within the blood vessel wall is with an inflatable balloon. Small balloons for insertion into the blood stream and methods to inflate them are known in the field of medical treatment devices. According to one aspect of installing this invention, the wires 12 are positioned circu ferentially around such a deflated balloon. The balloon is then introduced into the blood vessel by any acceptable technique. When the tip of the catheter is at the proper location, the balloon is inflated and the wires 12 contact the wall 30. In the embodiment in which prongs 26 are present on the ends of wires 12, the prongs are solidly pressed and embedded int the vessel wall 30 under the force of the balloon. Th balloon is then deflated and removed. If thi installation technique is used, the wires 12 do not nee to be spring-biased outward; the force of the balloon wil press them outward into contact with the wall 30.

The catheter 2 is removed from the blood vesse by first removing the heat shrink Teflon® tubing 32 o other structure which secures the proximal ends 34 of th wires. Each wire 12 is then withdrawn from contact wit the blood vessel wall 27 into its respective guid tube 38. Figure 2B shows the wires in this partiall withdrawn position. Each wire 12 is withdrawn until th loops 25 and prongs 26 are retracted into the soft silico rubber that forms tube 4 and guideways 38. Afte withdrawing each wire 12 into its respective guide tube, the catheter is withdrawn from the blood vessel usin standard catheter withdrawal procedures. The ability t withdraw the prongs 26 and loops 25 into the guideways 3 reduces damage to the blood vessel upon removal of th catheter.

Figure 3 shows the distal end of a secon embodiment of the present invention. The secon embodiment comprises a tube 41 with an elliptical cros section and two lumens 42 and 44 that run the length o the catheter. The second embodiment is intended to b used for hemodialysis applications in which one of th lumens is used to aspirate blood and the other lumen i used to infuse blood after dialysis. As in the firs embodiment, four positioning wires 50 extend the length o the catheter within guideways 52. In the secon embodiment, two of the wires 50 are located along th major axis of the elliptical tube 41 while the other wire are located along the minor axis. In this embodiment, th two wires 50 located along the major axis may extend fro the tube 41 at a different angle than the two positionin wires which are located along the minor axis. Eac wire 50 has a loop 54 and tip 56 near its end. The tips 56 serve as penetration means for penetrating the wall of the blood vessel, while the loops 54 serve as limiting means for limiting the depth to which the tips 56 penetrate.

Figure 4 shows the distal end of a third embodiment of the present invention. The third embodiment has four positioning wires 60 attached to the distal end 62 through the use of securing hoops 64 and heat shrink Teflon® tubing 66, which is placed over the hoops and shrunk into place. The combination of the securing hoops 64 and Teflon® tubing 66 helps ensure that the hoops 64 and wires 60 are securely attached to the distal end 62 of the catheter. In an alternate embodiment, not shown, the wires 60 could be integrally formed into the catheter, thus eliminating the need for securing hoops 64 and tubing 66.

The positioning wires 60 extend radially outward from the securing hoops 64. The wires 60 may be attached to securing hoops 64 by welding, brazing or other appropriate means. In some applications, it may be desirable to treat the wires 60 with an antithrombotic coating to reduce blood clotting on the wires, as explained for the first embodiment. Each wire 60 has a loop 68 formed near the end of the wire, such that a short penetration tip 70 extends outwardly from each loop. The prongs 70 serve as penetration means for penetrating the wall of the blood vessel, while the loops 68 serve as limiting means for limiting the depth of penetration. This third embodiment of the antistenotic intravascular catheter is inserted into a patient's blood vessel using the same process as described for the first embodiment. Although the third embodiment is structurally simpler than the first embodiment, it requires a more complex procedure in order to remove the catheter from the patient's blood vessel. The third embodiment may be removed using a procedure similar to the catheter insertion procedure described in the first embodiment. tubular introduction sheath of the type shown in Figure 22-25 is placed over the catheter at the location wher the catheter enters the blood vessel, and is subsequentl slid down the catheter until it reaches the distal end o the catheter. The tubular introduction sheath slides ove the positioning wires 60, withdrawing the loops 68 an prongs 70 from contact with the wall of the blood vessel After withdrawing the loops and tips into the introductio sheath, the catheter is slid within the introductio sheath and withdrawn from the blood vessel. Th introduction sheath could be removed during or subsequen to removal of the catheter from the patient's bloo vessel. Figure 5 illustrates a tip retainer 9 at th distal end 8 of the catheter constructed according to a alternative embodiment for retaining the catheter ti within the blood flow stream and preventing the tip fro contacting the inner wall 27 of the blood vessel 30 According to this alternative embodiment of Figure 5, th tip retainer 9 includes wires 72 having a blun terminating end 74 for contacting the inner wall 27 of th blood vessel 30. The blunt end 74 does not include sharp tip of the type previously described with respect t tips 26 and 56. Instead, the blunt end 74 contacts th inner wall 27 but does not penetrate the wall of the bloo vessel 30. The four wires 72 act to anchor the tip 80 o the catheter with respect to the blood vessel wall an retain the tip within the flow in the blood vessel whil preventing the tip 8 from contacting the blood vessel wal with the advantages as previously described. The wires 7 are prestressed to be resiliently spring biased outwar with an equal pressure from each of the wires 72 such tha the tip 8 is generally centered within the blood vesse 30.

An indexing mark 76 is also included on th catheter tube 4 , extending along the length of th catheter tube 9. The indexing mark 76 visually indicates to a user the rotational orientation of the tip 8 within the blood vessel. The position of the indexing mark 76 may indicate, for example, that the rotational orientation of the tip 8 is such that one of the wires 72 is positioned where two of the blood vessels join together and is not contacting any wall of the blood vessel or providing stabilization. The user may then elect to change the rotational orientation of the tip 8 such that each of the wires 72 is firmly in contact with the blood vessel wall. This could be done, for example, with the catheter within the introducer tube.

However, one reason for providing four wires 72 is because contact with three wires is generally deemed sufficient to stabilize and retain the tip 8 such that it does not contact the wall 27. For example, the catheter 4 having the inventive tip retainer at the distal end 8 may be positioned at or near the brachial cephalic junction. There is a risk that one or more of the wires 12 may fall into the junction. By having at least three wires, one advantage is that the tip 8 can be stably anchored even if one of the wires is not anchored to the wall; the others will hold it in position. Thus, even if one of the wires 72 is not contacting the blood vessel wall, the other wires 72 will be contacting the wall and will retain the tip 8 in a position to prevent it from repeatedly bumping against the inner wall 27 of the blood vessel 30.

Figure 6 illustrates an alternative embodiment for the tip retainer 9 having wires 78. The wires 78 include enlarged loops 80 at their distal end. The enlarged loops 80 do not penetrate the blood vessel wall 30. Instead, they rest firmly against the inner wall 27, as an anchor to firmly the retain the tip 8 in a fixed position within the blood vessel. The loops 80 have an enlarged surface area to ensure that the blood vessel wall 30 is not penetrated while providing a firm support for the tip retainer 9. The loop 80 abuts firmly against the 17

inner wall 27 without penetrating it in a manner simila to the anchor of a ship resting on the bottom but no penetrating through the floor. The tip retainer 9 in thi way anchors the tip 8 without penetrating the wall of th blood vessel 30.

Figure 7 illustrates an alternative embodimen of the tip retainer 9 having wires 82 formed in a enlarged loop 84. The loops 84 are formed from a singl piece of wire that is bent at the end and terminates b being contacted to itself at the end 87, a single wir being within the guideway. Alternatively, the loop 84 i formed from the wire 82 being bent in half and having tw sections of the wire 82 extend within the guideway 86 The two ends of the wire 82 extend out of the proximal en of the tube 4 at position 34 as shown with respect t Figure 1. The wires 82 can therefore be extended o retracted, according to the user's preference, to provid loops 84 of a desired size and shape. The wires of th loops 84 are prestressed or bent to be resiliently sprin biased outward so they extend with equal force and equa distance from the tip 8 so as to retain the tip 8 i approximately the center of the blood vessel 30. Use o loops 84 provides the advantage of broad contact area 8 with the inner wall 27 while ensuring there is n penetration of the wall. The broad contact area at distal region of each of the loops 84 is a further aid fo centering the tip 8 and ensuring that it is firml retained within the blood flow and the blood vessel an does not contact the inner wall 27. Figure 8 is an alternative embodiment generall along the lines of Figure 7 with the loops 84 formed in cloverleaf arrangement. The cloverleaf shape of the wir 84 serve to further increase the contact area and provid strength in anchoring the tip 8 of the catheter 4 with the blood vessel but without penetrating the wall of t blood vessel. In one embodiment, the loops exit from t tip region 8 a selected distance 95 back from the end the tip. Having the wires exit spaced back from the tip end 120 decreases the risk of creating blood clots at the end 120 or facing the lumen shut at the face 120 under a heavy spring force. The end region 8, particularly the face 120, may be constructed of a somewhat stiffer material to keep the lumen opening from being partially closed when the wire loops 84 are deployed.

In the cloverleaf arrangement of Figure 8, each end of one wire extends down the same guideway 86, or alternatively each has its own guideway 86, permitting user manipulation of individual wires. The wires may exit from the face 120 of tip 8, or, as shown, exit from the sidewall and extend forward, toward the tip.

Figure 9 illustrates an alternative embodiment for the tip retainer 9 of a three-leaf clover configuration. Three loops 89, 91, and 93 are provided that extend out of the surface of tip end 120 if desired. The three loops 89, 91, and 93 are positioned equidistant around the catheter tube 4. Using three wires provide the advantage of fewer wires in the blood flow, but still produces sufficient anchoring force. For example, as previously discussed with respect to Figure 5, the catheter may be installed such that the tip is at or near the brachial cephalic junction. Even if one of the loops 89 falls into the junction itself, the other two loops 91 and 93 will contact the wall and provide a stable contact to anchor the tip 8 within the vessel and not contacting the wall.

The wires 82 of loops 84 of Figures 8 and 9 are formed with a preselected resilient bias outwards as determined by their shape and construction. In some embodiments, a very light spring action is provided by having a light, resilient bias outward so that the device may be used in a wide range of size of blood vessels, from very small to very large, with assurances that the blood vessel wall will not be penetrated. In the embodiment of Figures 8 and 9, the spring bias force outward is easily adjusted by varying the angle of connection between th straight portion within the guideway and the loop portio 84. For example, the angle at which the straight portio 84 extends from the tip 8 can be selected at a desire angle.

One distinct advantage of the present inventio over the prior art is that the catheter end 8 is retaine within the flow of the blood and prevented from contactin the wall of the blood vessel without holding the cathete end 8 absolutely rigid. According to some prior ar techniques, such as that described in the article o Pieper, as discussed in the background of the invention the concept is to hold the tip as rigid as absolutel possible. While this may have some benefit in som embodiments, one distinct advantage of the presen invention is that the invention will still operat properly even if the tip is permitted to move to differen locations within the blood vessel. For example, the tip may move to one side or the other within the blood vessel based on movement of the patient, or of a rubbing of th blood vessel. Additionally, the tip 8 may mov longitudinally, along the direction of the blood flow a the blood pulses. This is desirable in many embodiment and may actually act to relieve some of the stress create by the presence of the catheter. The retaining assembly includes members having a light spring force which permit some relative movement between the catheter tip 8 and th wall 27 of the blood vessel. However, the springs hav sufficient force that the catheter tip rarely actuall contacts the blood vessel wall, thus preventing damage t the blood vessel wall. In some of the embodiment described herein, the spring force becomes stronger as t catheter tip approaches the wall, thus serving to maintai the catheter tip in a space relationship from the vess wall, even if some force is acting on the catheter tip to push it toward the wall. The light spring force at extended location of the spring permits some catheter ti movement, but as the catheter tip becomes closer to the wall, the spring force gradually increases, making it more difficult for the catheter tip to actually contact the wall. In some embodiments disclosed herein, the spring force is sufficiently strong that as the catheter gets extremely close to the wall, it is forced back with significant pressure to prevent an actual impact with the wall.

As will be appreciated, the tip retainer assembly 9 of each of the embodiments of Figures 5-21 are made of or coated with the appropriate antithrombotic material that does not cause an adverse reaction when placed within a patient's body, as previously described.

The physician extends or withdraws the wires in the embodiments of Figures 1-8 to contact the blood vessel wall with the desired force. If the wall has a large diameter, the wires are extended further. Similarly, if a high retaining force is desired, the wires can be extended slightly farther. On one hand, if the physician encounters a small vessel, or one in which a weak retaining force is sufficient to anchor the tip 8, he may withdraw the wires as necessary.

The physician also selects a catheter tip having a properly sized and spring biased tip retainer assembly 9 for his intended uses. If the spring force is found to be too weak, or alternatively, too strong, he may select another tip that is manufactured having a tip assembly 9 of a slightly different spring force, as necessary. (This may be done for each of the embodiments of Figures 1-21, as desired.) Similarly, a range of loop sizes and shapes is provided to permit the physician to select the one that best suits the needs of a particular use.

The physician may observe the placement and operation of the catheter tip inside the blood vessel to ensure that it is properly anchored as the procedure progresses. This observation can be carried out with known ultrasonic imaging equipment, for example. Alternatively, the tip 8 may have a radioactive isotope o other marker placed therein to permit the physician t ensure that the tip is immobilized and not contacting th vessel wall. A fluoroscope may also be used to image th tip.

Often the tip must be in position for a extended period, many hours or sometimes many days. Soli placement of the tip, spaced from the wall and anchore with respect to the wall followed by confirmed observatio of this by a physician is thus helpful to permit long-ter placement of the catheter without injury to the bloo vessel.

Figures 10A and 10B illustrate a furthe alternative embodiment of the invention. According t thi alternative embodiment, an intravascular stent 154 i provided at the distal tip 8 of the catheter 4 for th prevention of stenosis and subsequent catheter occlusion. The stent 154 is an intraluminal vascular prosthesi constructed of braided stainless steel, or other alloys. They are, of course, coated with the appropriate material to prevent interaction with the blood. Curren applications of a standard stent include placement in th urinary system, and more recently, within arteries fo arterial and coronary disease as an intra-arterial wal support usually following balloon angioplasty.

To deploy the stent according to the invention, an expandable balloon 162 is positioned near the ti region 8 along the outer wall of the catheter 4, o alternatively, a rolling membrane is provided around th stent 154 and constructed near the catheter tip. Th balloon 162 is covered with the self-anchoring stent 154 the entire assembly being attached along the sidewall o the catheter tube 4 when it is inserted into the bloo vessel. After the catheter 4 has been inserted into th blood vessel with a tip 8 at the desired location, th balloon 162 is inflated to deploy the stent 154. Th stent 154 includes prongs 162 that penetrate the wall o the blood vessel to solidly affix the stent 154 and the catheter end 8 to the wall of the blood vessel. The balloon 162 is then deflated. The stent 154 is connected to the catheter tip 8 by one or more anchoring wires 156, 158, and 160. If desired, to facilitate catheter removal, the prongs 162 may be connected to the stent 154 with prestressed breakaway points so that they may be easily broken off and the stent 154 removed. The prongs 162 may be composed of a material which is absorbed by the body over time. Alternatively, the wires 156, 158, and 160 which connect the tip 8 to the stent 154 may have prestressed breakaway points at the surface of the stent, interfacing between the catheter and the stent 154. The catheter 4 may be removed by withdrawing it, applying pressure to sever the prestressed breakaway points near the surface of the stent 154. In this embodiment, the stent 154 remains within the body and, is preferably constructed of a material which can be absorbed by the body over time rather than being constructed of stainless steel. Materials which can be absorbed by the body are well known in the art and anyone of those which is commonly known is acceptable for use to construct stent 154 or prongs 162.

According to the embodiment of Figures 10A and 10B, the stent 154 is preferably a braided mesh, or an alternative embodiment, includes a slit extending longitudinally along its entire length. Having a slit in the stent 154, or alternatively constructing it of a braided material permits the stent to be completely collapsed, in a tight position around the catheter 4 and then expanded by balloon 162 to have enlarged diameter along the inside surface of the blood vessel.

By using the techniques according to the concept of this invention, as disclosed in Figures 10A and 10B, as well as all other figures of this invention, the catheter tip 8 is immobilized, preventing damage to the blood vessel wall and thus preventing cellular proliferation an stenosis.

Figure 11 illustrates a further alternativ embodiment of the catheter having a tip retainer 9 at distal end thereof composed of fletching 100. Th fletching 100 is positioned adjacent the tip 8 or, in on embodiment, recessed back from the tip portion 8 a sligh distance as shown in Figures 15 and 16 and explained i more detail herein. An advantage of the use of fletching 100 is tha the tip retainer 9 is constructed in which the fletchin 100 is a plastic or polymer which is injection molded. I one preferred embodiment, the fletching 100 is injectio molded or extruded simultaneously with the injectio molding or extruding of the tube 4 so that th manufacturing cost is minimized and the entire assembly i provided as a single, unitary member.

Figures 12-14 illustrate alternative embodiment for the shape of the fletching 100 which provides the ti retainer assembly 9. According to the embodiment o Figure 12, three fletchings are provided, 102, 104 an 106. The fletching 100 is composed of the same materia as the tube 4 , being constructed from a unitary member i a preferred embodiment. In the embodiment of Figure 12 the fletching 102 contains a flat surface region 108. Th flat surface region 108 extends circumferentially alon the same radius of the catheter 4. ^• That is, the fla surface 108 faces upward, presenting a planar surfac generally at a tangent to the circular catheter 4. Th fletching 102 then extends upward, away from the ti portion 8, narrowing to terminate in a tip region 110 The fletching 102 has a preselected resilient spring bia outward as it extends upward from a base region 11 towards the tip region 110. The tip region 110 contact the wall of the blood vessel but does not penetrate th wall. The contact at the tip 110 performs the function o anchoring the tip 8 with respect to the blood vessel wal so that the tip 8 is retained in a fixed position with respect to the blood vessel wall, without contacting the wall and remaining within the blood flow. In a preferred embodiment, three fletchings are provided, 102, 104 and 106, each constructed similarly to that which has been described in detail with respect to fletching 102 and each providing a similar spring biased force outward to center the tip portion 8 within the blood vessel.

According to the embodiment as shown in Figure 12, the tip portion 110 of each of the fletchings 102, 104 and 106 is positioned beyond the end of the tip region 8, so that the anchoring position is beyond the distal end of the tip portion 8. Providing fletchings 102, 104 and 106 that extend beyond the tip 8 is easily provided during the manufacturing process during the molding or extruding of the tubing 4, or alternatively by cutting the tip short after the extruding process so that the tip 110 extends beyond the end of the tip 8.

In an alternative embodiment the fletchings 102 are positioned such that the tip portion 110 of the fletching 102 that contacts the blood vessel wall is approximately at the end of the tip portion 8 as explained with respect to other alternative embodiments herein.

Figure 13 shows an embodiment in which a fletching 114 has a flat planar portion 116 in generally the same orientation as the planar portion 108 of fletching 102. That is, the fletching extends flat with respect to the tubing 4, generally in the same circumferentially extending radius as the tubing 4. However, the fletching 114 has a rounded tip portion 118 providing a broader contact surface for anchoring the tip region 8 with respect to the blood vessel wall. The broad surface area 118 provides a large contact surface area to ensure that the tip portion 8 is firmly retained in the desired position, spaced from the wall a selected distance at all times. Three fletchings are provided similar to fletching 114, spaced equidistant around the tubing 4. This structure may also be used in the embodiments of Figures 1-10 by aligning the respective wires or loops to contact the blood vessel wall approximately adjacent to or behind the tip 120. Figure 13 also illustrates an embodiment in which the contacting portion 118 terminates prior to the end 120 of the tip portion 8 of the catheter tubing 4. In some embodiments, having the contact location to the blood vessel wall approximately aligned with or slightly behind the actual tip 120 of the tip portion 8 provides advantages in the operation and structure of the device.

Figure 14 illustrates an alternative embodiment for fletchings 100 illustrating individual fletchings 122, 124 and 126. According to the embodiment of Figure 14, the fletching 122 extends perpendicular, to the cathete tubing 4. That is, the fletching 122 is vertical wit respect to the catheter tube 4. As best shown in Figur 14, in this embodiment the fletching is formed in a shap which curves quickly upward, and extends in a generall straight, long tapered edge 127 for an extended distance. The thin edge 127 contacts the inter wall 27 of the bloo vessel, to anchor the tip portion 8 at a selected positio with respect to the blood vessel wall. The fletching ha an extended contact edge along the blood vessel wall, t more firmly retain the tubing 4 in a desired angula orientation and prevent rotation of the tubing 4. (Thi same advantage is provided by selected shapes of the wire of Figures 1-10 as well.)

In one embodiment, the fletching 120 i relatively stiff, so as to slightly stretch the bloo vessel and at the particular point of contact create slight depressed channel in which the fletching rests Preferably, the fletching is not so stiff as to penetrat the wall of the blood vessel but, is sufficiently stiff t prevent undesirable rotation of the tip 8. The upper edg 128 may also be tapered to be thinner in cross sectio than the lower edge 130 if desired, as explained in more detail with respect to Figures 18 and 19 herein.

Figures 15 and 16 illustrate an alternative embodiment in which the tip retainer 9 is composed of fletchings 132, 134 and 136 very much like the fletchings on an arrow. That is, as explained specifically with respect to fletching 132, the fletching has a long, tapered region 138, a rounded upper region 140 and a rounded region 142. Just like the fletching on an arrow, the fletching 132 extends vertically away from the tube 4, perpendicular to the catheter tubing 4, similar to the direction of orientation of fletching 122 of Figure 14.

In the embodiment of Figure 15, the fletchings 132, 134, and 136 are spaced a selected distance 138 from the end 120 of the tip portion 8. The rounded upper portion 140 contacts the blood vessel wall spaced a selected distance from the tip portion 8, as illustrated in Figure 15. In the embodiment of Figure 16, the fletchings 132, 134 and 136 are positioned such that the rounded upper portion 140 is positioned approximately aligned at the end 120.

An advantage of the embodiment of Figure 15 is that the flow at the catheter end 120 is not obstructed, interfered or altered by the fletchings 132, 134 and 136. Rather, the blood flow is affected only by the presence of the tip portion 8 which can be configured along conventional lines as known in the art to achieve a desired purpose. The contact to the blood vessel walls by the rounded portion 140 is sufficiently close to the tip portion 8 that the tip portion is retained within the blood flow and is prevented from contacting the blood vessel wall.

On the other hand, in the alternative embodiment of Figure 16, having the rounded portion 140 approximately aligned with the end 120 provides a firm control exactly at the tip 120 to ensure the maintaining of the tip portion 8 at a fixed location within the blood vessel at all times. The end 120 is exactly anchored in position and undergoes little or no movement because the anchor locations around the blood vessel wall are directly aligned with the tip end 120. This provides a fir positioning system for the tip portion 8 to ensure that the end 120 does not contact the blood vessel wall, even under agitated conditions.

Figures 18 and 19 illustrate a particular advantage of the fletching according to the present invention. The fletching is tapered as it extends outward. That is, the fletching is relatively thick at the base 144 where it extends from the tubing 4 and tapers to a very thin edge at the outside regions, particularl at region 140. Having the fletching tapered provides the advantage that one size fletching will fit all blood vessel sizes within a selected range.

For example, as best shown in Figure 18, th catheter 4 is in a relatively large blood vessel th fletchings 132, 134 and 136 extend straight, and int contact with the blood vessel wall 127. The tip 140 ma roll over slightly, depending upon the size of the larg blood vessel 146. The size of the fletching 132 i selected to ensure that it will at least contact the inne wall 127 of any blood vessel into which it is to be use so that it may perform the tip retaining function as ha previously been described. However, in a large bloo vessel, such as the type shown in Figure 18, the tip 14 may slightly contact the edge, thus providing an adequat anchor surface area to retain the catheter tubing 4 in fixed position as has been described.

Figure 19 illustrates a smaller blood vessel, i which the fletching is rolled over at the edges, in broad circumferential contact with the blood vessel wal 127. The edge 140 can easily roll over and be positione along the surface of the wall 27 without taking u significant blood vessel area while providing a relativel large contact surface within a small blood vessel. Th tapering of the fletching and providing it with thin edges at 140 provides the advantage that even in a small blood vessel, the same fletching may be used except that a larger surface area of the edge portion of the fletching 140 will be in abutting contact with the surface of the wall. This provides the additional advantage of increasing the cross-sectional area of contact between the fletching and the blood vessel, to more securely retain the tip portion 8 within the central region of the blood vessel and prevent contact with the wall 27.

The tapered fletching provides the additional advantage that a preformed tip assembly 9 can be used in a desired blood vessel. A single blood vessel may have a large inner diameter lumen at one region and a small inner diameter lumen in a different region. The difference in diameter may be caused by localized thickening of the walls, injury fatty build up, or other causes. When the catheter is placed in the vessel, the physician may not be aware of the exact diameter of the blood vessel at the desired location (even though it might be measured ultrasonically, for example) . The physician is assured that the catheter tip will be properly retained in the blood flow and spaced from the wall even if the exact dimensions are not as was expected at the installation site. (This advantage is provided in the embodiment of Figures 1-8 by the selective withdrawal or extension of the wires, as previously explained.)

Having tapered edges provides another distinct advantage: the relative flexibility and spring bias within the fletching may be easily altered along the fletching as it extends outward. That is, at the very edge of the fletching near rounded portion 140, the resilient bias can be very light because the fletching is very thin at the edges. Closer to the base, the fletching gradually becomes thicker, naturally increasing the spring strength and resilient bias within the fletching. This has the advantage of increasing the centering ability of the tubing 4 because if the tubing begins to be presse out of position, towards one wall the fletching on tha side of the tubing will have the base region presse closer to the wall; however, the base region being thicke and having a stronger spring action will tend to increas the resilient bias away from the wall to push with mor force away from the wall and tend to center the tubing within the blood vessel. Each of the fletchings ar constructed with uniform spring bias to act together i centering the tubing 4 within the blood vessel and preven the tubing from becoming too close to the blood vesse wall on any side.

In one embodiment, the spring strength of th fletching varies proportional to the thickness of th fletching. In an alternative embodiment, the fletching i constructed such that the spring bias is not uniform wit respect to the thickness of the fletching. For example, relatively strong spring bias can be placed adjacent th base, even more than would otherwise be present, to ensur that the tubing 4 is always spaced at least a minimu distance from the wall 27. Alternatively, a slightl stronger spring bias may be placed right at the tip 14 than would otherwise be present based on the edges bein extremely thin because the edges may be so thin as to hav little or no spring bias based on their own thickness. I such an embodiment, the properties of the material or th type of material used may be slightly altered at the ver tip region 140 to provide sufficient spring strength t anchor the end even though the tip portions are extremel thin.

It is contemplated, for example, that a thi wire 139, such as the type shown in Figure 5, could b positioned along the tapered edge 138 and along th rounded edge 140 if desired for ensuring that the rounde tip portion 140 always has sufficient spring bias t perform the anchoring function, even in a large bloo vessel, and yet have the fletching sufficiently thin fo an extended length that it can roll over, providing the improved characteristics of an increased surface contact area if desired.

Figure 17B illustrates a further alternative embodiment for the fletching in which an aperture 143 extends through the fletching. The fletching is thus a ridge of material having a top edge 140. The aperture 143 provides an additional opening for blood flow while the ridges firmly retain the tube 4 within the vessel. The size and shape of the aperture can be varied to alter the spring strength, as desired.

Figures 18-22 also illustrate alternative embodiments for the orientation of the fletching on the tubing 4. According to one alternative embodiment as shown in Figures 18, 19 and 21, the fletching is straight, directly in line with the tubing 4. This is the same style for mounting the fletching on some arrows, as is known in the prior art. Alternatively, the fletching may be mounted at a cant to provide a spiraled fletching as best shown in Figures 20 and 22. When the fletching is mounted at a cant, so as to slightly spiral around the tubing 4 that provides the advantageous effect of more smooth blood flow through the blood vessel while aiding to maintain the tip 4 in a straight-line orientation with respect to the blood vessel.

The fletching as illustrated in Figures 15-20 has the advantage of being easily constructed. In one embodiment, the molding 4 and fletching is constructed as an integral piece by injection molding methods known in the art. The material can be constructed from a polymer, silicone, or any other well-known nonthrombogenic material. Alternatively, the tubing 4 can be extruded with the fletching being provided in an extrusion mold process. Another advantage of the fletching is that it permits easy sheath removal and insertion, as will be explained later in more detail. The fletching also is easily constructed with graduated stiffness along the length of the fletching as it extends away from the tubing 4 providing the advantages previously described.

The insertion and removal of the catheter tubing 4 having the tip retainer on the end thereof will now be explained in particular detail with respect to Figures 22- 25. The description of Figures 22-25 is particularly directed towards the embodiment previously described wit respect to Figure 9; however, this is for illustration purposes only and the same method of insertion and removal is uniformly applicable to each of the embodiments described herein, from embodiment of Figure 1 through t the embodiments of Figures 15-21.

Referring now to Figure 22, the catheter 4 having the tip retainer 9 at the end thereof is prepare for introduction into the blood vessel by placing i within an introducer sheath 148. The introducer sheat 148 is preferably made of polyurethane, plastic or som other relatively pliable material that is sufficientl stiff to overcome the spring bias of the retainer membe so that the entire assembly has a diameter approximatel equal to that of the catheter tubing 4. The introduce sheath 148 includes a handle portion 150 which th physician may use to manipulate the introducer sheath 14 and guide it into the proper position within the bloo vessel. In a preferred embodiment, the introducer sheat 148 has a slight taper 152 at the distal end to make th introduction into the blood vessel more simple.

As shown in Figure 23, the introducer sheath i advanced into the blood vessel 30 until the catheter tub is at the desired location within the blood vessel. A this position, the tip retainer 9 is held within th introducer sheath and does not contact the wall of th blood vessel 30.

As shown in Figure 24, the introducer sheath 14 is then removed from the catheter tubing 4. According t a preferred embodiment, the introducer sheath 148 i constructed of a relatively thin layer of polyurethan which is easily ripped or torn by the physician. In order to remove the introducer sheath, the physician firmly grabs the handles 150 on either side and begins to tear apart the introducer sheath. The introducer sheath will separate into two pieces, tearing apart outside of the blood vessel and withdrawing the introducer sheath from the catheter tubing 4. As the introducer sheath is withdrawn from the catheter tubing 4, the tip retainer is released and automatically extends outward according to the preset spring bias to contact the blood vessel wall and retain the tip portion 8 at the selected location as has been previously described.

In an alternative embodiment, the sheath is simply removed by sliding it backwards, rather than tearing the sheath into two pieces. As will be appreciated, tearing the sheath into two separate pieces provides the distinct advantage of permitting the introducer sheath to be around only a portion of the tubing 4 and easily separated from a portion of the tubing without having to completely slide off either end of the tubing. It also provides the advantage that the physician may easily and uniformly withdraw the introducer sheath while leaving the tubing 4 in the preset position, to permit the tip retainer to be deployed to retain the tip portion 8 in the desired position within the blood vessel.

Removal of the catheter 4 having the tip retainer 9 on the end thereof is easily accomplished with each of the alternative embodiments. In the alternative embodiments of Figures 5-21, it will be appreciated that the tip retainer does not penetrate the blood vessel wall 27. Further, in many of these embodiments the tip retainer is constructed to permit easy withdrawal or removal from the blood vessel. According to one method of removal, the catheter 4 is simply withdrawn from the blood vessel, and simultaneously withdraws the tip retainer while in the deployed position. Even though the tip retainer is deployed, such is shown in Figures 8, 9, 10, and others, the orientation is such that the withdrawal may be easily accomplished because the spring bias permits the tip retainer 9 to be pressed inward slightly as necessary. To advance the tip retainer would be difficult, or impossible, because this would serve to increase the spring bias and press the tip retainer 9 more firmly into position against the blood vessel wall, increasing the anchor strength. On the other hand, the withdrawal of the catheter tube 4 tends to pull the tip retainer 9 away from the wall and permit easy removal without excessive stress on the blood vessel wall.

According to an alternative embodiment, the tip retainer is withdrawn from the deployed position so as to not contact the wall by sliding an introducer sheath once more over the tip portion 8 to withdraw the tip retainer 9 from the blood vessel wall. The sheath and catheter tube 4 may then be withdrawn from the blood vessel.

While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

Claims

1. A catheter adapted for insertion into a blood vessel having blood flowing therethrough, comprising: a catheter having an internal passageway for permitting fluids to pass through the catheter; and a tip immobilizing means located at a distal end of the catheter for anchoring the distal end of the catheter within the blood flow to maintain a tip of the catheter in a spaced relationship from a blood vessel wall and prevent the tip of the catheter from contacting a wall of the blood vessel without substantially obstructing fluid flow of blood through the blood vessel, such that catheter failure due to stenosis or thrombosis at the catheter distal end is reduced.

2. The apparatus according to claim 1 wherein the tip immobilizing means includes a prong at a distal end of the immobilizing means, the prong being adapted to penetrate the blood vessel wall and extend into said wall for a selected distance to anchor the catheter tip at a fixed position with respect to said wall.

3. The apparatus according to claim 1 wherein the tip immobilizing means includes a loop portion at a distal end of the immobilizing means, the loop portion being adapted to contact the blood vessel wall but not penetrate the wall to anchor the catheter tip at a fixed position with respect to said wall.

4. The apparatus according to claim 2, further including a loop at the base of the prong to prevent the prong from extending more than a selected distance into the blood vessel wall.

5. The apparatus according to claim 1 wherein the immobilizing means includes a plurality of looped wires that extend at selected angle from the catheter tip and have preselected resilient spring bias to exert force on the bloo vessel walls to maintain the catheter tip a fixed distanc from the wall.

6. The apparatus according to claim 5 wherei looped wires are at a tip portion of respective single wire that extend from the catheter tip.

7. The apparatus according to claim 5 wherein th looped wires extend in loops from the catheter tip and provid a large surface area for contact with the blood vessel wall.

8. The apparatus according to claim 1 wherein th immobilizing means includes a plurality of fletchin positioned adjacent the catheter tip portion.

9. A catheter adapted for insertion into a bloo vessel comprising: a catheter having a lumen therein that permit fluids to pass through said catheter, the catheter having tip portion and a proximal portion spaced from the ti portion; a tip retainer assembly attached to the tip portio of the -catheter; and a plurality of wall contact members, each of whic contacts a blood vessel wall when the catheter is within blood vessel, the wall contact members being a part of the ti retainer assembly, the wall contact members including a wal contact portion and spacer portion, the wall contact portio contacting the blood vessel wall at a selected location an remaining in contact with the blood vessel wall at the sam selected location for an extended time and the spacer portio that extending for a distance spaced from the wall, the space portions and wall contact portions being attached to sai catheter tip portion and maintaining the catheter tip a space distance from the blood vessel wall and preventing th catheter tip from contacting the blood vessel to prevent damage to the blood vessel wall by repeated contact between the catheter tip and the blood vessel wall.

10. The catheter according to claim 9 wherein each of said wall contact members is spring biased with a selected spring force for extending into abutting contact with said blood vessel wall, each of said wall contact members being spaced from each other circumferentially around the catheter tip portion to provide a tip retainer assembly that resiliently biases the catheter tip a fixed distance spaced from said blood vessel wall and maintains the catheter tip within the blood flow region.

11. The apparatus according to claim 10 in which said wall contact members include a looped portion having a relatively narrow spring biased section and a relatively large area wall contact portion for contacting the blood vessel wall under a firm, spring biased force over a relatively large area to firmly maintain said catheter tip a spaced distance from the blood vessel wall at all times under the spring biased force.

12. The catheter according to claim 9 wherein the tip retainer assembly includes a plurality of fletchings that are attached to the catheter tip and extend from the catheter tip to a position spaced from the catheter- tip and having said wall contact portion as a distal portion of said fletchings.

13. The catheter structure according to claim 12 wherein said fletchings are an integral part of said catheter tube, being formed from the same material and being a unitary member with said catheter.

14. The apparatus according to claim 12 wherein said fletching is broader at a base portion than at a distal portion and tapers gradually inward from the base towards the tip portion to provide a relatively thin, pliable tip portion.

15. The catheter according to claim 13 in which the fletching is positioned on the catheter at a cant to provide a spiral member extending along the catheter tip portion.

16. The catheter according to claim 9 wherein said wall contact portion contacts said wall at a position adjacent the tip of said catheter tip.

17. A method of forming a catheter having a retainer assembly therein comprising: forming a catheter tube; and inserting a tip retainer assembly into said catheter tube to solidly attach an attachment portion of the tip retainer assembly within the catheter tube and maintain a wall contact portion of the tip retainer assembly outside of the catheter tube.

18. The method according to claim 17, further including forming a preselected bend in the tip retainer assembly prior to attaching it to the catheter tube to create a spring bias of a selected force and in the selected direction.

19. The method of forming a catheter tube and tip retainer assembly combination comprising: injecting into a mold a catheter tube, the mold having a shape to provide a tip retainer assembly as an integral portion of the molded catheter tube at a distal catheter tip portion of said tube, the tip retainer assembly including a wall contact portion that is adapted to contact the wall of a blood vessel and a spring bias portion that provides a preselected spring force to resiliently bias the wall contact portion away from the catheter tube and into abutting contact with a blood vessel wall; curing the material in the mold; and removing the material in the mold to obtain a catheter tube assembly having a tip retainer as an integral unitary member with the catheter tube.

20. A method of inserting a catheter having a tip retainer assembly attached at one end thereof into a blood vessel, comprising: placing a sheath insertion tube assembly within a. blood vessel, the sheath insertion tube assembly including an insertion sheath having handles at a proximal end thereof which are not inserted into the blood vessel, a tip portion which is inserted into a blood vessel and a catheter within the insertion sheath, said catheter having a tip retainer assembly at a distal end of said catheter; maneuvering the insertion sheath assembly with the catheter therein to a selected position within the blood vessel; and withdrawing the insertion sheath from the catheter tube while maintaining the catheter tube at a fixed position within the blood vessel, the withdrawal of the insertion sheath causing the tip retainer assembly to be deployed in a spaced position away from the catheter tube such that the tip retainer assembly contacts the blood vessel wall with a preselected resilient spring biased force and maintains the catheter tip anchored at a preselected location and held a selected distance from the blood vessel wall to prevent the catheter tip from contacting the blood vessel wall.

21. The method according to claim 20, further including: selectively extending or retracting wires at a distal region of the tip retainer to ensure that the tip retainer assembly contacts the blood vessel wall with sufficient force to retain the tip spaced from the wall but not with excessive force such as to significantly distort the blood vessel wall shape or penetrate through the wall.