Atraumatic fluid delivery devices

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.

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 '508 and '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
 atraumatic 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
 bubble-free 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.

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.sub.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,
 bio-compatable 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 24A of core wire 24 is the largest
 diameter at approximately 0.007". Central portion 24A preferably extends
 about 5.6" in length. Proximal to central portion 24A is tapered portion
 24B (See FIG. 4). Tapered portion 24B tapers down to a diameter of
 approximately 0.004" over a distance of 0.54". Further proximal is
 attachment portion 24C (see FIG. 4). Moving distally from central portion
 24A, core wire 24 includes tapered portion 24D, which tapers smoothly over
 about 1.4" from an outside diameter of approximately 0.0071" down to an
 outer diameter of about 0.00541 . This is followed by untapered portion
 24E, which extends for about 2.5". After that, distal portion 24F tapers
 over about 0.70" down to an outer diameter of about 0.0025". Moving
 further distally, portion 24G extends at about 0.0025" diameter through
 diffuser segment 40. The length of distal portion 24G 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 24C of core wire 24 is
 welded or otherwise secured into opening 28 in the wall of tube 12.
 Portion 24C preferably maintains the approximate 0.004" diameter from
 portion 24B.
 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 30 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 24G.
 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 embodiment
 illustrated in FIG. 3, four diffusers 41 are utilized, wherein the first
 three (two of which are illustrated) 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, 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 24G, 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 41A which direct fluid distally and
 axially along the device to provide atraumatic fluid delivery. Other than
 the switch to a distal opening, diffusers 41A 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 PV01PVP, 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 24C 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 46A 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 46A 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.