WO1993008864A1

WO1993008864A1 - Fluted catheter

Info

Publication number: WO1993008864A1
Application number: PCT/US1992/009582
Authority: WO
Inventors: Gene E. Myers
Original assignee: Myers Gene E
Priority date: 1991-11-05
Filing date: 1992-11-05
Publication date: 1993-05-13

Abstract

A catheter comprises a fluted portion or portions, possibly also with tunnels, to allow functional passage of blood past various points of engagement of the catheter with blood vessel walls.

Description

FLUTED CATHETER

Field of the Invention

This invention relates to catheters for use in diagnosis and treatment of blood vessel pathologies. More specifically, this invention relates to catheters having fluted shaft portions allowing functional passage of blood past various points of engagement of the catheters with blood vessel walls.

Paςkground of the Invention Coronary angiography is a standard procedure for evaluating patients suspected of having stenotic, or occluded, coronary arteries. Performing a coronary angiogram involves the placement of a pre-formed tube (catheter), generally under local anesthesia, into the origin (ostium) of a coronary artery or bypass graft. Radiopaque contrast is injected through the catheter with exit into the vessel to be visualized, and X-ray imaging film (i.e., fluoroscopic tape and 35 mm film) exposed for a permanent record. Radiopaque contrast generally consists of a liquid medium that blocks the passage of X-rays or other imaging energy frequencies. In other words, such a liquid medium is "opaque" to diagnostic X-rays just as a coin or other metallic object is opaque to such X-rays. As a result, the radiopaque contrast may be visualized on a X-ray imaging film as a white or unexposed area due to failure of the X-rays to expose the film in that region. If radiopaque contrast occupies the lumen of a blood vessel, the shape of the lumen, and therefore the topography of the blood vessel walls surrounding the lumen, may be visualized on X-ray imaging film.

During "diagnostic catheterization" the only task required of the catheter is that it be selectively placed in the ostium of the vessel to be visualized, in order to inject a radiopaque contrast. If a stenotic or occluded vessel is located, percutaneous transluminal coronary angioplasty (PTCA) may be chosen as a therapeutic alternative to coronary artery bypass surgery.

Performing PTCA requires the placement of a guiding catheter, which generally has a larger diameter than a purely diagnostic catheter, in the ostium of the stenotic vessel. Radiopaque contrast is injected and then visualized and recorded on videotape to provide a contoured image, or "road map" of the vessel undergoing interventional treatment. The guiding catheter not only must be capable of functioning as a diagnostic catheter to conduct radiopaque contrast into the vessel, but it must also be large enough to provide a conduit through which the flexible dilation balloon catheter and balloon catheter wire system can be introduced into the stenosis, or narrowed area. Additionally, the guiding catheter must provide a platform of sufficient strength to resist expulsion from the cannulated ostium of the vessel when pressure is exerted upon the distal balloon catheter as it crosses the stenosis. The external diameter of the guiding catheter is frequently similar to the diameter of the ostium of the stenotic vessel, leading to cessation of functional blood flow at points downstream of (distal to) the catheter tip. However, even if the guiding catheter is able to pass readily through the osHum, frequently the cannulated vessel rapidly tapers to a small diameter downstream of the ostium. In this case, the catheter tip usually advances (beyond the operator's control) until it is stopped by the smaller vessel wall, again effectively blocking downstream blood flow. Thus, it is frequently impossible for even the most skilled operator to place the guiding catheter tip proximate the area of synopsis within the vessel without severely impeding blood flow to the heart muscle.

In some cases the PTCA procedure can be successfully accomplished with a relatively short "diagnostic" phase and a single one- to two-minute balloon inflation. Under these conditions the patient may be able to tolerate the induced pain of angina pectoris, representing the physiological manifestation of oxygen starvation to the cardiac muscle (myocardium). More often than not, however, the pain is intolerable to the patient and the physician operator cannot safely proceed without jeopardizing the myocardium. To reestablish blood supply to the myocardium and relieve the angina, the physician operator will have to intermittently withdraw the guiding catheter from the ostium of the vessel. Such in and out movement of the catheter may result in injury and trauma to the vessel wall and may result in dislodgement of the dilation balloon catheter from within the stenosis.

In summary, PTCA procedures performed with prior art catheters frequently result in a reduction, or complete cessation, of blood flow to the heart muscles served by the catheter-occluded vessel. This, in turn, may produce severe chest pain, permanent injury to the heart muscle (myocardial infarction), irregularity of the heartbeat, formation of blood dots due to blood flow stagnation and even sudden death.

Several modifications of PTCA catheters in the prior art were directed at alleviating the problem of blood cessation following placement of a PTCA catheter in an ostium of a coronary artery. In one approach, single or multiple side ports are placed in the guiding catheter shaft proximal to the- point of contact of the distal portion of the catheter shaft with the coronary vessel walls at the ostium. With this structural modification, red blood cells and other blood cells are able to pass through the side ports, into the catheter's central lumen, out the distal end of the catheter and then to points downstream of the catheter location. The result is an apparent alleviation blood flow cessation problems.

A second alternative approach, the so-called "topless catheter exemplified in U.S. Patent No. 4,976,691 is also designed to alleviate bloo flow cessation. Manufacture of a topless catheter is accomplished by remov or absence of a portion of the wall in the distal portion of the cathete producing a "guiding finger". This configuration theoretically allo introduction of a PTCA balloon catheter into the ostium witho substantially impeding red blood cell flow to downstream artery locations. In application, however, the side port and topless cathet configurations create a new problem potentially of equal or greater magnitud than the problem of blood flow cessation. Simply stated, the problem is los of radiopaque contrast through the side ports and through the topless cathete segments. A useful guiding catheter must meet certain criteria. First, guiding catheter must be able to deliver a high concentration of radiopaqu contrast directly into the affected vessels, with minimal leakage into the aort in order to provide a pre-treatment "road map" of the intra-vesse topography so that the site of blockage can be accurately located. The contras also must be available to provide additional road maps during and afte intervention relieves the blockage. The volume of contrast must b minimized to limit patient exposure to potential toxic side effects of larg contrast volumes and to reduce the expense of the procedure. Second, guiding catheter must permit continuous blood flow into the vessel distal t the distal end of the guiding catheter in order to provide blood supply to the myocardium, thereby avoiding the severe chest pain, myocardial infarction irregularity of heartbeat and possible sudden death due to stagnation of blood flow and thrombosis (blood dot) formation. Third, a guiding catheter must provide a strong structural platform upon which interventional apparatus may be inserted and advanced into an area of stenosis. Although other criteria may be desirable, these three areas of concern are considered quite important with respect to this invention.

Although the side port and topless catheter configurations address, to an extent, the problem of blood flow cessation, neither configuration provides satisfactory results when judged by the first criterion above. For example, when an operator exerts external hand injection pressure to inject the radiopaque contrast through the central lumen of the catheter shaft, the induced pressure is likely to be 5-10 fold greater than that of the physiological aortic pressure. As a consequence, the contrast takes the path of least resistance. It is estimated that at least 30-40% of the contrast may leak into the ascending aorta rather than penetrating into regions distal to the tip of the catheter. The result frequently is a requirement for increased volumes of contrast (with increased risk to the patient and increased expense), incomplete and unsatisfactory visualization of the affected vessels both before and after treatment, and prolongation of procedural time. In many instances, the entire PTCA apparatus, induding guiding catheter, PTCA balloon catheter and wire, must be removed and exchanged for a diagnostic catheter. If the PTCA procedure turns out not to have been successful, the patient is exposed again to a repeat procedure with re-insertion of the entire apparatus. This may result in trauma to the origin vessel and result in difficulty in re-crossing the area that was partially angioplastied in the first procedure.

As such, it would be useful to produce a catheter allowing for continuity of blood flow during angioplasty as well as delivery of concentrated radiopaque contrast without significant leakage. It would be useful in addition to produce a catheter providing a strong structural platform for insertion and advancement of one or more balloon catheters. A diagnostic catheter having similar attributes is also desirable. Summary of the Invention

A catheter is provided for either diagnostic or therapeut treatment of blood vessels. The blood vessels comprise interior linings whi normally cfrcumferentially contact the external surfaces of any cathete What is provided is a catheter having an elongated hollow member with distal portion circumferentially engageable by the vessel lining, but th catheter indudes passage means for achieving functional blood flow past th catheter distal portion regardless of such engagement by the vessel lining.

A preferred catheter comprises either or both external an internal passage means. Such passage means may comprise parallel or no parallel grooves or flutes. Twisted or helical grooves may be provided i order to optimize (i.e. minimize) the wrapped diameter of a balloon cathete used with this invention. Different materials and surface coatings may b applied to the catheter and the passage means to further facilitate blood flo past the catheter. Sheath means may be provided to protect the flow of bloo from blockage by tissue prolapsing into the passage means.

Brief Description of the Drawings

Figure 1 is a prior art view of a catheter which is blocking the ostium of a blood vessel. Figure 2 is a prior art view of a tapered tip catheter which is blocking the ostium of a blood vessel.

Figure 3A is a prior art catheter, similar to that depicted in Figure 1, illustrating the inability of blood passage past the catheter.

Figure 3B is _.a sectional view of the catheter of Figure 3A taken along lines B-6.

Figure 3C is a sectional view of the vessel of Figure 3A taken along lines C-C.

Figure 4A is a prior art catheter having side ports which permit some passage of blood flow distally past the catheter. Figure 4B is a sectional view of the catheter of Figure 4A taken along lines B-B.

Figure 4C is a sectional view of the vessel of Figure 4A taken along lines C-C. Figure 5A is a prior art catheter illustrating the flow of contrast material into the vessel.

Figure 5B is a sectional view of the catheter of Figure 5A taken along lines B-B.

Figure 5C is a sectional view of the vessel of Figure 5A taken along lines C-C.

Figure 6A is a prior art catheter illustrating the loss of contrast material through blood perfusion ports.

Figure 6B is a sectional view of the catheter of Figure 6A taken along lines B-B. Figure 6C is a sectional view of the vessel of Figure 6A taken along lines C-C.

Figure 7 A is a prior art catheter illustrating the flow of blood past the catheter.

Figure 7B is a sectional view of the catheter of Figure 7A taken along lines B-B.

Figure 7C is a sectional view of the vessel of Figure 7A taken along lines C-C.

Figure 8A is a prior art catheter illustrating the loss of contrast material out the topless portion of the catheter. Figure 8B is a sectional view of the catheter of Figure 8A taken along lines B-B.

Figure 8C is a sectional view of the vessel of Figure 8A taken along lines C-C. Figure 9 is a side view of a fluted catheter illustrating blood flo past the catheter into the vessel.

Figure 10 is a side view of a fluted catheter illustrating bloo flow past, and contrast flow through, the catheter. Figure 11 is a side view of a fluted catheter with tunnels into distal surface for perfusion of blood.

Figure 12 is a side view of a fluted catheter with tunnels into lumen for perfusion of blood.

Figure 13 is a partial perspective view of a fluted external surfac of a catheter having parallel flutes.

Figure 14 is an end view of the device of Figure 13. Figure 15 is a partial perspective view of a fluted external surfac of a catheter having twisted flutes.

Figure 16 is an end view of the device of Figure 15. Figure 17 is an end view of an alternate embodiment externa surface having flutes configured to minimize tissue prolapse and maximize blood flow through the flute valleys.

Figure 18 is an end view of an alternate embodiment external surface having a sawtoothe fluted configuration. Figure 19 is an end view of a non-fluted catheter.

Figure 20 is a partial perspective view of a fluted and tunnelled catheter.

Figure 21 is an end view of a fluted end of the device of Figure 20. Figure 22 is a sectional view of one embodiment of the device of

Figure 20 taken at a catheter section after the tunnels have connected to the central lumen.

Figure 23 is an end view of another embodiment showing a tunnelled end of the device of Figure 20. Figure 24 is a partial sectional view illustrating optional widths of different portions of a fluted catheter according to the present invention to accommodate tunnel means and the like.

Figure 25 is a sectional view of a catheter having an external fluted surface.

Figure 26 is a sectional view of a catheter having an external fluted surface and tunnel means.

Figure 27 is a sectional view of a catheter having an external fluted surface and tunnel means. Figure 28 is a partial perspective view of a catheter having internal and external fluted surfaces in a parallel configuration.

Figure 29 is a partial perspective view of a catheter having internal and external fluted surfaces configured as a gentle helical twisted flute configuration. Figure 30 is a side view of a fluted catheter illustrating a circumferential sheath extending to a position proximal to a soft distal tip.

Figure 31 is a side view of a fluted catheter illustrating a circumferential sheath extending to a position at the connection between the catheter and a soft distal tip. Figure 32 is a side view of a fluted catheter illustrating a circumferential sheath extending to a position at the distal end of a soft distal tip connected to the catheter.

Figure 33 is a side view of a fluted catheter illustrating a circumferential sheath extending to a position beyond the distal end of a soft distal tip connected to the catheter, in the manner of an eaved tip to optimize blood flow and minimize tissue damage or prolapse.

Figure 34 is an end view of the catheter and circumferential sheath taken along lines 34-34 of Figure 33. Figure 35 is an environmental illustration of a fluted cathet having an eaved tip sheath extension functionally located in a blood vessel.

Figure 36 is an environmental illustration of a helically flute catheter having an eaved tip sheath extension functionally located in a bloo vessel.

Figure 37 is an end view of a catheter generally configured wit external and internal ripple surface flutes and having an eave circumferential sheath. Detailed Description of the Invention Referring to Figure 1, an exemplary prior art catheter 10 is show with distal end 14 positioned in ostium 20 of vessel 24. Catheter 10 ma comprise either a diagnostic or guiding catheter. Figure 2 illustrates a alternate embodiment prior art catheter 30 having distal tapered end 3 extending beyond ostium 20 in vessel 24. Catheter 10 and catheter 30 eac comprise wall portions 36 37 respectively which substantially completel ocdude functional flow into regions of vessel 24 distal to each of the catheters The potential harmful effects of such occlusion have been previousl discussed herein. It is suffiάent to observe that such ocdusion is not desired. Figures 3A, 3B, and 3C illustrate the problem noted in Figures and 2, but with more particular focus on a guiding catheter 40 having guid wire 42 and balloon 45. Catheter 40 also has a wall portion 47 which, whe positioned in ostium 20 of vessel 24, causes disruption and possible complete ocdusion of functional blood flow into downstream regions of vessel 24 dista to catheter tip 49. One prior art attempt to overcome this problem is illustrated in Figures 4A, 4B, and 4C, wherein catheter 40 has been modified to indude apertures 52 defined by wall portions of catheter 40. Apertures 52 are constructed so that blood cells 54 may enter catheter 40 central lumen 57 proximal to ostium 20 and exit central lumen 57 distal to ostium 20. Figures 5A, 5B, and 5C illustrate flow of radiopaque contrast 61 injected into catheter 40 and vessel 24. However, as previously noted, when catheter 40 is configured with wall portion 47 occluding blood flow past ostium 20 and when no apertures 52 are provided, then catheter 40 is inadequate. Alternately, when apertures 52 are included as shown in Figure 6A, then the leakage of contrast 61 results proximal to ostium 20 in a region which does not need such contrast. Moreover, the leakage may result in commensurate reduction of contrast 61 flow distal to catheter tip 49, as shown in Figures 6A, 6B, and 6C.

Another prior art catheter 70 is depicted in Figures 7A-7C and 8A- 8C. Catheter 70 is constructed in a manner to, apparently, alleviate blood flow cessation (Figure 7A). However, catheter 70 also permits substantial loss of contrast 61 away from the region of prime interest (Figure 8A). This results in substantial unnecessary expense and procedural ineffidency. Accordingly, catheter 70 is also of inadequate design. Referring now to Figure 9, one embodiment of the apparatus for the present invention is disclosed. The apparatus of the present invention depicted in one embodiment in Figure 9 comprises a guiding catheter 110 adapted for use with a balloon dilation catheter 112. Guiding catheter 110 comprises an axially elongated, and preferably substantially cylindrical, shaft 116 having a wall 118 forming a central lumen 120. A fluted portion 125 of the external surface 128 of wall 118 includes one or more grooves 132 each defined by valley portion 133, side wall portions 134, and ridge portion 135. The grooves 132 comprise ridge portions 135 which may preferably be coplanar (i.e., of the same diameter) with the full exterior diameter of cylindrical shaft 116. The fluted portion 125 of cylindrical shaft 116 is preferably but not^' exclusively designed for positioning proximate the distal end 137 of catheter 110.

Guiding catheter 110 preferably extends from the ascending aorta 139 into the ostium 140 of the left main coronary artery 143, proximal to the left anterior descending coronary aorta (LAD) and the drcumflex artery. It to be understood that catheter 110 of the present invention is applicable to a vessel in the human (or animal) body, whether cardiac or non-cardi arteries, veins, bypass grafts, or artifiάal vessels. Fluted portion 125 of cylindrical shaft 116 allows function passage of red blood cells 54 and other blood cells from the ascending aorta 1 or other regions proximal to distal end 137 of cylindrical shaft 116 into t lumen 152 of left main coronary artery 143 or other regions distal to the dist end 137. Such functional passage of blood cells to regions downstream catheter 110 permits full application of the selected diagnostic or therapeuti procedure while avoiding unacceptable adverse consequences (e.g. permane damage to cardiac muscle) due to reduced blood flow. This is als accomplished with optimal flow of contrast 61 into the downstream vess regions to be iUuminated as shown in Figure 10. The pathways defined by grooves 132 may be confine exdusively to the external surface 128 of wall 118, as depicted in Figure 9 an Figure 10, or such grooves may be along an internal surface to provid improved wrap capability, as depicted in Figure 28 and Figure 29. In a external groove embodiment, grooves 132 originate in regions proximal t the point at which external surface 128 of catheter 110 contacts the endothelia lining 160 of the vessel, and the grooves terminate on external surface 128 a or near the catheter distal end 137. Alternately, as depicted in Figure 11 grooves 132 may pass below external surface 128 and proceed as passages o tunnels 165 within the structure of wall 118, finally emerging as openings 16 at distal end 137 of catheter 110. In a further alternative embodiment, groove 132 may pass through the structure of the wall 118 and emerge as openings o the internal surface of the wall 118, providing fluid communication betwee grooves 132 and lumen 120 of the cylindrical shaft 116, as depided in Figure 12. The configuration of fluted portion 125 allows blood to proceed from regions proximal to the ostium to downstream regions distal to catheter 110. This is so even though the catheter may be designed to be of the same diameter, or even of a slightly larger diameter, than the ostium or blood vessel of final location. Passage of blood past the ostium under these conditions is accomplished without the need for openings in the catheter shaft 116 proximal to the ostium, as in the prior art. Such openings, unlike the fluted region of the present invention, allow significant leakage of radiopaque contrast before the contrast is able to enter the distal vase ulature. The catheter of the present invention likewise presents advantages over "guiding finger" catheters in which a portion of the distal wall of the catheter is removed so as to facilitate blood flow to the distal vasculature. In the various embodiments of the present invention, there is no need to prevent any section of wall from continuing in an uninterrupted fashion to the distal end of the catheter. That is, the distal end of the catheter of the present invention may be defined by a full circumference of wall structure, or a plurality of full diameter sections spaced by grooves 132. The result is that the distal portion of the catheter becomes substantially fully circumferentially engaged with the endothelial lining of the ostium or blood vessel. As such, there is little or no loss of radiopaque contrast or other injected agents to the ascending aorta or other blood vessels upstream of (proximal to) the fluted region.

The catheter of the present invention allows not only the infusion of diagnostic agents such as radiopaque contrast but also for infusion of therapeutic agents such a tissue plasminogen activator (TPA) or other drugs. Thus, the fluted configuration of catheter 110 is appropriate not only for guiding catheters adapted to be used in conjunction with a dilation balloon catheter, but also with diagnostic catheters or other catheters adapted for infusion of therapeutic agents. This is because the fluted configuration, as described above, allows diagnostic or therapeutic agents to be delivered t selected locations with a minimum of exposure of upstream areas to th agent. This defined localization of the agent(s) may be desirable in order t minimize toxic or other side effects of the agent at upstream locations, and t minimize the expensive loss of such agents.

Referring now to Figures 13 through Figure 34, variou configurations and constructions of catheter 110 are shown. To accommodat a variety of procedures and blood vessel placements, the grooves 132 may b manufactured in different ways. For example, axially oriented depressions 201 (referred to herein substantially interchangeably as grooves 132 which ar the sectional version of depressions 201) may be U-shaped in cross section, as depicted in Figures 13-16, 21, and 30-34. In alternate embodiments, longitudinal depressions 201 may be- V-shaped as depicted in Figure 18. In a further alternative embodiment, medial extensions 212 of ridge portions 135 of sidewalls 118 may partially cover longitudinal depressions 201, as depided in Figure 17. Such medial extensions 212 are adapted to prevent prolapse of the endothelial lining of blood vessels into grooves 132 or depressions 201. In accordance with the desired procedure and location of catheter 110 the number of grooves 132 in the fluted region may be varied from one or very few to a multiplicity of grooves. Numerous different methods of manufacture may also be employed. Indeed, as depicted in Figures 28, 29, and 37, a crimping method may be employed to shape the external and/or internal surfaces of catheter 110.

Figure 25 illustrates, in sectional fashion, catheter 110 having grooves 132 and a distal tip 263, such as a soft tip, attached. Figure 26 is a similar view as Figure 25, but depicting catheter 110 having an external fluted surface and tunnel means 165 extending through wall 118 to lumen 120. Similarly, Figure 27 shows catheter 110 having tunnel means configured to exit at distal apertures 168 as previously shown in Figure 11. Figures 30-34 illustrate sheath means 272, also described as a membrane, which is preferably circumferentially arranged around catheter 110. In Figure 30, sheath means 272 extends to a position proximal soft distal tip 263. In Figure 31, sheath means 272 extends to a position at or near the connection between catheter 110 main body and soft distal tip 263. Figure 32 shows sheath means 272 at a position at the distal end of soft distal tip 263. Figure 33, however, illustrates sheath means 272 extending beyond the distal end of soft distal tip 263, in the manner of an eaved tip extension 280. This configuration provides protection of distal ends of grooves 132 or tunnel means from blockage by tissue. Figure 34 is an end view of such sheath means 272 around catheter 110. A further advantage of sheath means 272 is the manner in which it ads as an abrasion reducing member. The membrane effect of sheath means 272 thus results in the least amount of frictional weak points. This permits improved life cycles for catheter(s) 110 and less potentially environmentally harmful disposal of such devices. Figures 35 and 36 show alternate embodiments of catheter 110 each having a protective eaved tip extension 280 in operational view within a vessel.

Having disclosed the subject matter of this invention, it should be apparent that many substitutions, modifications, and variations of the invention are possible in view of the above teachings. It is therefore to be understood that the invention as taught and described herein is only limited to the extent of the breadth and scope of the appended daims.

Claims

WHAT IS CLAIMED IS: 1. A guiding catheter for use in diagnostic and therapeuti treatment of blood vessels, said blood vessels having an interior lining, sai catheter comprising: an axially elongated hollow member having a distal portio circumferentially engageable with the interior lining of blood vessels, and proximal portion, each of said distal and proximal portions having a external surface and an internal surface defining a lumen; passage means for achieving functional blood flow past sai distal portion when said distal portion is circumferentially engaged by sai interior lining. 2. The catheter according to daim 1 wherein said passage means comprises a fluted wall portion. 3. The catheter according to daim 2 wherein said fluted wall portion comprises a helical shaped flute. 4. The catheter according to claim 2 wherein said fluted wall portion is located on said catheter external surface. 5. The catheter according to claim 2 wherein said fluted wall portion is located on said catheter internal surface. 6. The catheter according to daim 1 wherein said passage means comprises a catheter surface having a hydrophilic coating. 7. The catheter according to daim 1 wherein said passage means comprises a material having a coeff ident of friction relatively lower than that of the remainder of the catheter. 8. The catheter according to daim 1 wherein said passage means comprises a material having a composition that is different from the remainder of the catheter. 9. The catheter according to claim 1 wherein the catheter is construded of transparent material. 10. The catheter according to claim 2 wherein said fluted wall portion comprises parallel flutes. 11. The catheter according to claim 2 wherein said fluted wall portion comprises non-parallel flutes. 12. The catheter according to claim 1 wherein said passage means comprises a circumferential sheath around a portion of said catheter to prevent tissue prolapse and blockage of blood flow through said passage means. 13. The catheter according to claim 12 wherein said sheath extends distally beyond said catheter distal portion and any tip extension attached thereto. 14. A catheter for use in diagnostic and therapeutic treatment of blood vessels, comprising: an axially elongated cylindrical shaft having a proximal end and a distal end, said shaft including a wall defining a central lumen, said wall having an internal surface adjacent said lumen, and an external surface; and passage means comprising a fluted wall portion, said fluted wall portion adapted to permit functional passage of blood cells from a region proximal to said distal end to a region distal to said distal end, when said catheter is operationally positioned for use. 15. The catheter of daim 14, wherein said fluted portion comprises a section of said wall having structure defining at least one longitudinal groove on said external surface of said wall, said at least one longitudinal groove having a first end proximal to said distal end of said shaft and a second end at said distal end of said shaft. 16. The catheter of claim 14, wherein said fluted portion comprises: a first section of said wall having structure defining at least one longitudinal groove on said external surface of said wall, said at least one longitudinal groove having a first end on said external surface proximal said distal end of said shaft and a second end distal to said first end; and a second section of said wall distal to said first section, sai second section having structure defining at least one tunnel therein, said least one tunnel having a first end contiguous with a corresponding secon end of said at least one longitudinal groove, and a second end forming a opening in said wall at said distal end of said shaft. 17. The catheter of claim 14, wherein said fluted wall portio comprises: a first section of said wall having structure defining at least on longitudinal groove on said external surface of said wall, said at least on longitudinal groove having a first end on said external surface proximal t said distal end of said shaft and a second end distal to said first end; and a second section of said wall distal to said first section, sai second section having structure defining at least one tunnel therein, said a least one tunnel having a first end contiguous with, a corresponding secon end of said at least one longitudinal groove, and a second end forming a opening at said internal surface of said wall. 18. A method of passing blood past a catheter within a blood vesse comprising the steps: placing one or more flutes on a surface of the catheter; and arranging sheath means circumferentially around the cathete flutes to prevent tissue prolapse into the flutes.