Abstract:
The present invention is a device for insertion into a human or animal body, in a preferred embodiment a perfusion guidewire capable of delivering perfusion fluids to a vascular site while at the same time exhibiting handling characteristics associated with existing non-perfusion guidewires. Preferred embodiments include a perfusion guidewire which closely matches the dimensions and physical characteristics of standard guidewires. Preferred embodiments also permit high pressure perfusion of oxygen-supersaturated solutions, and include a diffuser segment which divides the flow and reduces fluid velocity, thereby providing an atraumatic, non-cavitating, bubble-free delivery to the patient. The invention also encompasses the attachment of a core wire within a tubular housing to provide superior characteristics to such guidewires, balloon catheters and similar devices.

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 09/092,254, filed Jun. 5, 1998, (now U.S. Pat. No. 6,235,007 B1,) which is a continuation-in-part of U.S. patent application Ser. No. 08/669,662, filed Jun. 24, 1996 (now U.S. Pat. No. 5,957,899), which is a continuation-in-part of U.S. patent application Ser. No. 08/563,057, filed Nov. 27, 1995 (now U.S. Pat. No. 5,797,876), all of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates generally to medical devices for insertion into the human or animal body and more particularly to guiding members with central lumens, particularly perfusion devices and balloons. Even more particularly, the present invention relates to a perfusion guidewire capable of delivering gas supersaturated solutions at high pressure atraumatically and bubble-free. 
     Various medical procedures require fluids to be delivered to specific locations within the body, typically via a fluid delivery catheter. A narrow steerable guidewire is often used to maneuver through narrow, tortuous, and/or branching body passageways. After the guidewire has been directed to the desired location, a fluid delivery catheter may be inserted over the guidewire. The guidewire is usually removed before fluid delivery begins. Alternatively, guidewires which are themselves capable of fluid delivery are also known in the art. Examples of such guidewires are disclosed in U.S. Pat. Nos. 4,964,409 and 5,322,508. Although the devices disclosed in these two patents do not appear to have been commercialized, it would appear that both would suffer from similar drawbacks in manufacturability and handling characteristics due to the manner in which the core wire is attached within each device. 
     Another application of such fluid delivery devices is in balloon angioplasty and similar procedures. In balloon angioplasty, a catheter equipped with a small balloon is inserted (usually over a guidewire) into an artery that has been narrowed, typically by the accumulation of fatty deposits. The balloon is then inflated to clear the blockage or lesion and widen the artery. During balloon inflation, blood flow distal to (i.e., “downstream” from) the inflated balloon may be completely or almost completely blocked. 
     Myocardial ischemia (i.e., a reduction in blood perfusion to the heart muscle) occurs transiently in many patients undergoing coronary angioplasty procedures, such as balloon angioplasty, directional atherectomy, rotational atherectomy, and stent deployment. The permissible duration of occlusion due to balloon inflation or other device deployment is normally determined by the severity of myocardial ischemia. Typically, evidence of severe ischemia (including patient chest pain and ECG changes) requires that the operator deflate the balloon or remove the occlusive device after approximately 60 to 120 seconds. For anatomically difficult lesions, such as type B and C lesions, longer periods of balloon inflation (or other device deployment) are frequently desirable for the first balloon inflation or other device deployment. 
     Autoperfusion balloon catheters can in some circumstances allow longer periods of balloon inflation. However, the blood (or other physiologic liquid) flow through such devices is frequently insufficient to provide an adequate oxygen supply to tissues distal to the angioplasty balloon or other occlusive device. 
     Recent advances in the generation and delivery of supersaturated oxygen solutions have made it possible to deliver greater amounts of oxygen to tissues distal to an angioplasty balloon. For example, U.S. Pat. No. 5,407,426, entitled “Method for Delivering a Gas-Supersaturated Fluid to a Gas-Depleted Site and Use Thereof” and U.S. Pat. No. 5,599,296 entitled “Apparatus and Method of Delivery of Gas-Supersaturated Liquids” disclose various methods for the generation and delivery of supersaturated oxygen solutions. 
     As is described in the two above patents, the generation, transport, and delivery of supersaturated oxygen solutions may require the application of high hydrostatic pressures. Accordingly, there is a need for a high pressure device capable of infusing bubble-free fluid, which is supersaturated at high pressures (preferably with oxygen), to vessels or ducts through and beyond the central lumen of a balloon angioplasty catheter or similarly occlusive device. There is a further need for a high pressure guidewire capable of delivering such supersaturated oxygen solutions to small vessels without rupturing or otherwise damaging those vessels. The guidewire disclosed in the &#39;508 and &#39;409 patents referenced above would not be well suited to such applications for a variety of reasons. For example, the internal fluid lumens and fluid exits are not configured to eliminate bubble formation which can result from the delivery of gas supersaturated liquids. Bubble formation in the coronary arteries can be fatal. Also these devices are not designed to handle the high pressures necessary for adequate oxygen delivery while maintaining an a traumatic flow out of the device. There thus remains a need in the art for a fluid delivery device with standard guidewire handling characteristics capable of atraumatically delivering gas supersaturated fluids at high pressure into tortuous vasculature. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a guidewire capable of delivering perfusion fluids to a vascular site while at the same time exhibiting handling characteristics associated with existing non-perfusion guidewires so that additional education or retraining of operators is reduced or eliminated. 
     It is a further object of the present invention to provide a guidewire capable of delivering supersaturated solutions at high pressures to vessels or ducts atraumatically. 
     A preferred embodiment of the present invention meets the foregoing needs by providing a perfusion guidewire which closely matches the dimensions and physical characteristics of standard guidewires in diameter, length, flexibility, column strength, torque transfer, surface friction, kink resistance, radiopacity (i.e., opacity to x-rays), non-thrombogenicity (i.e., tendency not to promote blood clots) and bio-compatibility. A preferred embodiment of the invention includes a diffuser which provides bubblefree injection of metastable supersaturated solutions. The diffuser is provided with sleeves positioned so that the rapid flow from the diffuser is deflected axially along the device to protect vessels from rupture. A perfusion guidewire according to the present invention preferably includes four general sections: a tubular proximal segment, which comprises the greater part of the perfusion guidewire length; a transitional region which provides for attachment of the core wire such that the fluid delivery requirements are met without compromising guidewire handling; a distal diffuser segment which provides a pressure and velocity drop for the delivered fluid and serves to optimally deflect fluid flow; and a coil tip which mimics the distal functions of a standard coronary guidewire. A further aspect of the present invention includes a method of attaching a core wire to a tubular housing in a fluid delivery guidewire or other device. A preferred embodiment of the method includes forming a side hole in the tubular housing, passing an end of the core wire through the hole in the tubular housing, melting a ball on the end of the core wire, pulling the core wire to position the ball against the tubular housing and welding it in place. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference is next made to a brief description of the drawings, which illustrate an exemplary embodiment of a perfusion guidewire according to the present invention. The drawings and detailed description which follow are intended as an example of the present invention, the scope of which is set forth in the appended claims. 
     FIG. 1 illustrates a transluminal fluid delivery system including a fluid delivery device according to an embodiment of the present invention; 
     FIG. 2 is a cross-sectional view of the proximal portion or handle of a perfusion guidewire according to an embodiment of the present invention; 
     FIG. 3 is a partial cross-sectional view of the distal part of a perfusion guidewire according to the invention; 
     FIG.  4 . is an enlarged, partial cross-sectional view of the transitional region, identified by circle  4  in FIG. 3; 
     FIG. 5 is an enlarged, partial cross-sectional view of the diffuser segment of the perfusion guidewire identified by circle  5  in FIG. 3; 
     FIG. 6 is an enlarged, partial cross-sectional view of the distal diffuser identified by circle  6  in FIG. 3; and 
     FIG. 7 is a partial cross-sectional view of the distal tip of a perfusion guidewire according to the present invention; 
     FIG. 7A is a partial cross-sectional view of a portion of a perfusion guidewire showing an alternative diffuser segment and a distal tip according to an alternative embodiment of the invention; 
     FIGS. 8A-E illustrate steps in attaching the core wire to the first tubular housing according to an embodiment of the invention; and 
     FIG. 9 is a cross-sectional view of the distal end of a balloon catheter according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     The structure and function of the preferred embodiments can best be understood by reference to the drawings where the same reference numerals appear in multiple figures, the numerals refer to the same or corresponding structure in those figures. 
     FIG. 1 shows a transluminal fluid delivery system  100  including a perfusion guidewire according to the present invention. Fluid delivery system  100  includes a source of supersaturated fluid at high pressure  102 , such as a pump or reservoir, connector  101 , tube  104  connecting an output of fluid source  102  to an input of connector  101 , and high pressure delivery device  108 , which will be described according to the present invention in terms of a preferred embodiment as a coronary guidewire. As will be discussed further below, perfusion guidewire  108  includes proximal segment  10 , transitional region  20 , distal diffuser segment  40 , and coil tip  50 . 
     In preferred embodiments of the invention, fluid source  102  will provide oxygen supersaturated liquid (such as physiologic saline) at high pressure and under conditions which maintain the oxygen in solution without bubble formation. An example of a fluid source is described in U.S. Pat. No. 5,599,296 entitled “Apparatus and Method of Delivery of Gas-Supersaturated Liquids”. Utilizing such a system, generation and delivery of oxygen-supersaturated fluids at pressures from about 100 to 10,000 psi, with oxygen concentrations of about 0.1 to 2 cc O 2 /g, are achievable. The device according to the present invention is preferably capable of withstanding fluid pressures up to at least about 500 psi. More typically, operating pressure may vary within the perfusion guidewire embodiment from about 2000 psi at the distal end to about 5000 psi at the proximal end, and thus preferred embodiments would be capable of withstanding such pressure. Such a system permits delivery of approximately 0.1 to 50 cc of fluid, such as oxygen superaturated fluid, per minute. With the high pressure delivery device described herein, such flows can be safely delivered to the patient with great accuracy of placement in tortuous vasculature and reduced risk of bubble formation or trauma to the vasculature. 
     Referring now to FIG. 2, a portion of proximal segment  10  of guidewire  108  is shown. Proximal segment  10  includes a first tube  12  which defines fluid lumen  14 . Tube  12  is made of bio-compatible material, has the appropriate dimensions, and the appropriate burst strength, flexibility, torque transfer, and kink resistance characteristics, selectable by a person of skill in the art, for use in the particular intended application. Tube  12  may be coated over most of its length with a thin film of low friction, biocompatible coating  13 , such as PTFE. Tube  12  and lumen  14  open at proximal end  16  for connection to source  102  shown in FIG.  1 . 
     In one embodiment, tube  12  of proximal segment  10  is preferably a  304  stainless steel tube having an outside diameter of approximately 0.0140″, an inside diameter of approximately 0.009″, and a length of approximately 150 cm. Tube  12  preferably has a burst strength exceeding about 10,000 psi. Tube  12  preferably also has a 0.0002″ to 0.0005″ thick coating  13  of PTFE over its full length, except for a few centimeters at each end. If necessary, to avoid kinking during the initial part of a procedure, a support wire or stylet (not shown) may be inserted in tube  12 . The support wire or stylet would be withdrawn before liquid is introduced into tube  12 . 
     Referring now to FIG. 3, a preferred embodiment of the distal part of perfusion guidewire  108  is shown. The distal part includes transitional region  20 , diffuser segment  40  and coil tip  50 . Transitional region  20  comprises the region of perfusion guidewire  108  where the distal end of tube  12  connects to core wire  24 , and to second tube  30 . Transitional region  20  also includes the region wherein core wire  24  is provided with the appropriate cross sectional shape, length and diameter to provide desired handling characteristics. The distal end of core wire  24  is, in a preferred embodiment, ground with a series of taper and barrel grinds in order to provide a balance of stiffness, flexibility, pushability and torqueability to navigate the tortuosity of the vascular system as well as control fluid velocity of perfusion fluids delivered through the device. In particular, the profile of core wire  24  according to a preferred embodiment of the invention is designed, as explained below, to control the velocity of an oxygen supersaturated solution delivered at high pressure so as to reduce or eliminate bubble formation which may result from shear forces acting on the solution. Core wire  24  is preferably coated with a thin film of an appropriate hydrophilic coating which also helps reduce the possibility of bubble formation along its length. Based on the teachings of the present invention, a person of ordinary skill in the art may adapt the configuration of the core wire to different sizes of guidewires and to provide variations in handing characteristics. 
     In an exemplary embodiment, core wire  24  is approximately 30 cm long with a circular cross section. Central portion  24 A of core wire  24  is the largest diameter at approximately 0.007″. Central portion  24 A preferably extends about 5.6″ in length. Proximal to central portion  24 A is tapered portion  24 B (See FIG.  4 ). Tapered portion  24 B tapers down to a diameter of approximately 0.004″ over a distance of 0.54″. Further proximal is attachment portion  24 C (see FIG.  4 ). Moving distally from central portion  24 A, core wire  24  includes tapered portion  24 D, which tapers smoothly over about 1.4″ from an outside diameter of approximately 0.007″ down to an outer diameter of about 0.005″. This is followed by untapered portion  24 E, which extends for about 2.5″. After that, distal portion  24 F tapers over about 0.70″ down to an outer diameter of about 0.0025″. Moving further distally, portion  24 G extends at about 0.0025″ diameter through diffuser segment  40 . The length of distal portion  24 G is about 1.0″. 
     The attachment of core wire  24  and second tube  30  to tube  12  is best illustrated, according to a preferred embodiment, in FIG. 4. A method for securing the core wire according to the invention is described below in connection with FIGS. 8A-8E. Attachment portion  24 C of core wire  24  is welded or otherwise secured into opening  28  in the wall of tube  12 . Portion  24 C preferably maintains the approximate 0.004″ diameter from portion  24 B. 
     In order to provide for attachment of second tube  30  by epoxy adhesive  32 , the distal end of tube  12  is tapered, preferably over about a distance of 0.25″, to an outside diameter of about 0.0118″. Second tube  30  is preferably a polyimide tube, having an outside diameter of approximately 0.0130″ and an inside diameter of approximately 0.011″. Second tube  30  has greater flexibility than tube  12 . Other materials which exhibit desirable properties of flexibility and strength, such as polyester, may be used also. Second tube  30 , in conjunction with core wire  24 , provides an annular fluid path going forward from the attachment point of the core wire. The reduced outside diameter at the proximal end of tube  12  facilitates attachment of second tubular housing  30  while maintaining a low profile joint. 
     Referring again to FIG. 3, at the distal end of transitional region  20  is a connection to diffuser segment  40 . The connection comprises a short outer support tube  32  secured by epoxy adhesive bonds  34  and  36  to both second tube and third tube  46  of diffuser segment  40 . Diffuser segment  40  is preferably approximately 1.0-2.0 cm long, and third tube  46  defines a further extension of fluid lumen  14 . 
     Tube  46  preferably may be made of polyimide which has excellent hoop strength as well as good burst strength and bondability. In the exemplary embodiment, so far described, third tube  46  has an inside diameter of about 0.006″ and outside diameter of about 0.008″. Fluid lumen  14  in this segment is also annular and of constant cross section due to the constant diameter of core wire portion  24 G. 
     A plurality of outlet ports  44  are provided in third tube  46 ; however, the ports are shielded by diffusers  41 . Diffusers  41  include sleeves  42  which surround tube  46 . Ports  44  communicate with proximally directed fluid channels defined around housing  46  by sleeves  42 . This creates a reverse flow which is generally parallel to the axis of perfusion guidewire  108 . The design protects the vessel from trauma due to fluid impingement when the distal tip of perfusion guidewire  108  is placed, for example, deep into a small side branch of a coronary artery. Any number of diffusers may be utilized to provide a desired flow. According to the illustrated embodiment, four diffusers  41  are utilized, wherein the first three (illustrated in FIG. 5) vary slightly in construction from the fourth and distal-most diffuser (illustrated in FIG.  6 ). 
     In the exemplary embodiment, illustrated in FIG. 5, each sleeve  42  is approximately 0.06″ in length, with an outside diameter of approximately 0.014″ and an inside diameter of approximately 0.012″. Preferred materials are again polyimide and polyester. Each sleeve  42  is secured to tube  46  at the distal ends by epoxy joints  43 , which is bevelled to be atraumatic. Annular polyimide bushing  45  also helps center the sleeves. The distance between the distal edge of one sleeve and the distal edge of the next sleeve in this embodiment is approximately 0.10″. The proximal edge of the sleeves incorporate radius  47  to provide a non-catching, atraumatic profile. All joints exposed to supersaturated fluid flow have been filleted to provide a smooth flow path that eliminates bubble formation by filling in all sharp right angle edges exposed to the flow path. The angle of the fillets of the diffuser region assist in reducing the shear of the supersaturated oxygen solution during delivery. 
     Diffuser segment  40  divides the flow and reduces the fluid velocity, thereby providing an atraumatic, non-cavitating, cavitating, gentle, non-bubbling flow of high pressure oxygenated fluids. As shown in FIG. 6, fluid lumen  14  ends within tube  46  at the distal end of diffuser segment  40  where it is sealed by filler tube  52  and epoxy adhesive layers  48  and  49 . Each of core wire portion  24 G, filler tube  52 , third tube  46  and epoxy layers  48  and  49  continue as a solid, but flexible, member into coil tip  50 . 
     FIG. 7A illustrates an alternative embodiment wherein diffuser segment  40  includes distally open diffusers  41 A which direct fluid distally and axially along the device to provide atraumatic fluid delivery. Other than the switch to a distal opening, diffusers  41 A are preferably essentially the same as (mirror image of) diffusers  41  as described above. Coil tip  50  is also preferably as described below in connection with FIG.  7 . 
     FIG. 7 shows coil tip  50  of perfusion guidewire  108 . The material properties and dimensions of coil tip  50  are preferably selected to at least approximately match the physical properties, in particular handling characteristics, of standard coronary guidewires. At the proximal end of coil tip  50 , filler tube  52 , third tube  46  and epoxy layers  48  and  49  continue from the diffuser segment. Distal coil  54  is attached via epoxy adhesive  56 , which fills between a number of the proximal coils as shown. Distal coil  54  serves as a compliant leading edge for the atraumatic and formable guidewire. The general requirements, construction, and dimensions of such a distal coil are well known to those skilled in the art. In a preferred embodiment, distal coil  54  is approximately 2 cm long with an outside diameter of about 0.014″. Preferably distal coil  54  is radiopaque. A preferred material is platinum. 
     A length of stainless steel ribbon  58  is inserted into distal coil  54  until the proximal end of stainless steel ribbon  58  is positioned in the proximal end of distal coil  54 . Distal coil  54  and stainless steel ribbon  58  are attached to filler tube  52  by epoxy joint  56 . Stainless steel ribbon  58  is trimmed flush with the distal end of distal coil  54  and joined using silver solder  60  or other appropriate material. The distal end of core wire  24  is preferably finished off by flattening to approximately 0.001″ thick. 
     Preferably, distal coil  54  is encapsulated in and filled by a flexible, soft durometer, medical grade, rubber material  62 . Preferred adhesives for material  62  are urethane adhesive and U.V. adhesives. A thin flexible film of a lubricous hydrophilic coating may then be applied over flexible material and to approximately 30 cm of the distal end of perfusion guidewire  108 . Appropriate hydrophilic coatings, such as BSI PV0 1 /PVP, are well known to those skilled in the art. Material helps eliminate bubble formation due to nucleation sites on the coil surface and between the coils by filling in the space between the coil wraps and captures the distal end of core wire  24 . The soft durometer of material  62  allows the coil to be shaped while maintaining a hermetic seal between the individual coils. 
     The disclosed perfusion guidewire  108  may be inserted and used in the same manner as a standard coronary guidewire using a conventional torquing handle (not shown). Preferred embodiments of the invention exhibit substantially the same performance characteristics as a standard guidewire, and can be inserted and used with conventional instrumentation and techniques. Additionally, it is contemplated that features of the invention may be incorporated into non-guidewire fluid delivery devices without departing from the scope of the invention. For example, the diffuser segment may be readily adapted to other applications requiring delivery of fluids atraumatically through small flexible lumens. Also, the configuration of the coil tip described herein may be utilized with other fluid delivery guidewires or devices to reduce interference of the coils with fluid flow around the coil. 
     The connection of core wire  24  and tubular housing  12 , as shown in FIG. 4, provides a smooth transition and flexibility and uniform transmission of a torque as between the tubular housing and core wire, such that the device, according to the present invention, exhibits handling characteristics substantially the same as standard guidewires. In particular, a smooth, even rotary action is required and provided by the guidewire of the present invention, even in a tortuous, vascular pathway. The connection, as disclosed, also provides a smooth transition with respect to fluid flow characteristics which is important when perfusing gas supersaturated fluids in order to minimize or prevent bubble formation. In particular, the connection of the core wire does not create sudden flow restrictions or pressure drops which may be presented in prior fluid delivery guidewires. A method for securing the core wire to the tubular housing, as shown in FIG. 4 is described below in connection with FIG. 8A-8E. Referring to FIG. 8A, notch  70  is cut into the wall of tubular housing  12  and a 0.0045″ hole  72  is punched through the wall of tubular housing  12  centrally within notch  70 . As shown in FIG. 8B, attachment portion  24 C at the proximal end of core wire  24  is ground to a point at end  74 . The point is then threaded through inner lumen  14  from the distal end and pushed up through hole  72 . As illustrated in FIG. 8C, ball  76  is formed on end  74 . Ball  76  preferably has a diameter of approximately 0.010″ and may be formed, for example, by a laser welder. As shown in FIG. 8D, core wire  24  is pulled distally with respect to tubular housing  12  until ball  76  rests in notch  70 . Finally, as shown in FIG. 8E, core wire  24  and tubular housing  12  are welded together, with welding material  78  filling notch  70 . Any roughness may be ground smooth. 
     The described connection technique is one method for attaching the core wire to a tubular housing so as to achieve the advantages described above and combine high strength with a reliable and repeatable manufacturing process. This technique also permits the core wire to be attached directly to the tubular housing wall without an intervening structure, which could disrupt the flow characteristics and/or create discontinuities in torque and flexibility, while at the same time, permitting the core wire to become substantially centrally located within the tubular housing lumen, approximately at the point of attachment. Such central location reduces the length of tubing with an eccentric annular lumen. 
     The core wire attachment according to the present invention, as described above, may also be utilized advantageously in other devices, such as balloon catheters, including integral core wire construction. An example of such a balloon catheter is illustrated in FIG.  9 . In this embodiment, core wire  24  is secured to first tubular housing  12 , as shown in FIG.  4  and described above in connection with FIGS. 8A-8E. Second tubular housing  30  is attached to the first tubular housing as previously described. Balloon  80  may be formed from a third tubular housing  46 A or alternatively may be formed directly from second tubular housing  30 . Distal coil  54 , with solder tip  60  and safety wire  58 , are provided as previously described. Third tubular housing  46 A is joined to core wire  24  at its distal end, and to coil spring  54  via epoxy joint  82 . Epoxy  32  also joins the second and third tubular housings. Such a balloon may be formed by techniques known in the art and may include additional features such as a self-venting passage or holes for delivery of medication, which are described, respectively, in U.S. Pat. No. 4,793,350 and U.S. Pat. No. 5,087,244, each of which is incorporated by reference herein. Additionally, the distal coil of the balloon embodiment may incorporate filler material  62  if desired. 
     It is to be understood that the present invention has been described in terms of an exemplary embodiments. Thus, the invention is not limited to the specific embodiments depicted and described. Rather, the scope of the invention is defined by the appended claims.