Patent Application
20100228150
None
This invention relates to guide wire apparatuses and to methods for using same. More specifically, the present invention relates to guide wire apparatuses with improved torque and flexure characteristics.
Catheter guidewires (hereafter “guide wires”) have been used for many years to “lead” or “guide” catheters to target locations in animal and human anatomy. This is typically done via a body lumen, for example, such as traversing luminal spaces defined by the vasculature to the target location. The typical conventional guide wire is from about 135 centimeters to 195 centimeters (or more) in length. The guide wire generally comprises a generally solid core wire and a distal coil spring or coil, often made from a radiopaque material. The core wire is tapered on the distal end to increase its flexibility. The coil spring is typically soldered to the core wire at a point where the inside diameter of the coil spring matches the outside diameter of the core wire. Platinum is selected for the coil spring because it provides radiopacity for better fluoroscopic or other radiologic imaging during navigation of the guide wire in the body, and because it is biocompatible.
Navigation of a guide wire through the anatomy is usually achieved with the assistance of radiographic imaging. This is conventionally done by viewing the guide wire in the body lumen using X-ray fluoroscopy or other comparable methods. The guide wire optionally can be provided with a tip that is curved or bent to a desired angle so as to deviate laterally a short distance. By proximal rotation of the guide wire the curved distal tip can be made to deviate in a selected direction from an axis of the guide wire about which it rotates.
In use a guide wire is inserted into a catheter so that the guide wire can be advanced so that its distal end protrudes out the distal end of the catheter, and also is pulled back in a proximal direction so as to be retracted into the catheter. Visualization is by fluoroscope, for example, or another device. The guide wire and catheter are introduced into a luminal space, comprising for example, a vessel or duct and advanced therethrough until the guide wire tip reaches a desired luminal branch. The user then twists the proximal end of the guide wire so as to rotate and point the curved distal tip into the desired branch so that the device may be advanced further into the anatomy via the luminal branch. The catheter is advanced over the guide wire to follow, or track, the wire. This procedure is repeated as needed to guide the wire and overlying catheter to the desired target location of medical interest.
A guide wire having a relatively low resistance to flexure yet relatively high torsional strength is very desirable. As the guide wire is advanced into the anatomy, internal resistance from the typically tortuous turns, and surface contact, decreases the ability to advance the guide wire further within the luminal space. This, in turn, may lead to a more difficult and prolonged procedure. A guide wire with high flexibility helps overcome the problems created by internal resistance. However, if the guide wire does not also have good torque characteristics (torsional stiffness), the user will not be able to twist the proximal end in order to rotate the distal tip of the guide wire as required. Flexibility and good torque transmission characteristics are especially needed when the guide wire is intended to be used in the highly complex neurovasculature and neuroanatomy.
This invention relates to medical guide wires which provide the desired performance characteristics. Yet more specifically, this invention relates to guide wires having distal and proximal coil on core construction wherein the distal coil comprises a radiopaque material and the proximal coil is a multifilar guide wire and comprises a super elastic material. A core wire or mandrel of this invention generally is not super elastic and preferably has a flattened extreme distal end coupled to an atraumatic tip.
The present invention will now be illustrated in the attached FIGS in which like numerals are used to designate like features, and in which:
The above FIGS should be understood as illustrative and not limiting of the invention.
Thus, in
Shown in
Generally speaking, core wire 18 comprises a non-super elastic material such a stainless steel or MP35N. Other core wire metals and alloys, optionally including hydrophilic, lubricious or hydrophobic coatings, may be used on proximal core wire length 12. Proximal core wire length 12 may include exchange wire coupler structures (not shown), see e.g., U.S. Pat. No. 5,282,478 to Fleischhacker, Jr., et al. and U.S. Pat. No. 5,546,958 to Thorud et al. Alternatively proximal core wire length 12 may comprise the rest of an exchange wire or other proximal guide wire structure known to the art (also not shown), potentially increasing guide wire length to 250 cm or more.
Optional flattening 27 of core wire 18 immediately proximate tip 20 provides an enhanced tip stiffness in a direction in the plane of the flattened tip and an enhanced floppiness in a direction perpendicular to the plane of the flattened core wire tip (arrows 24 and 26 respectively). Thus by rotation of the guide wire the medical professional can determine for herself whether the floppiness or stiffness feature of this invention (or both) are to be utilized. Flattening of core wire 27 is an optimal but preferred feature of a guide wire (especially a neuro guide wire) of this invention.
Core wire 18 is attached to coil structures 14, 16 by means of, for example, a solder joint 30, or an adhesive joint 32. Joints 30, 32 provide a smooth, gradual transition from coil wire 18 to coil 14 for interventional or diagnostic devices (e.g., a catheter) being guided or steered to a vascular site of medical interest. This is especially true of joint 30 where it is necessary to avoid an abrupt change in overall guide wire diameter so that a device passing thereover could encounter resistance. Joint 32, in addition to providing a smooth transition between coils 14, 16 (for any cooperating device) must also be flexible e.g., to bend with coil 18, so as not to produce a kink point at that juncture. Atraumatic tip 20 is usually a solder joint or bulb (it is bullet-shaped in this embodiment) and must also be smooth and rounded to prevent tissue injury as the tip 20 passes through the vasculature. Tip 20 may be made of other materials, adhesives, polymers, metals or alloys and may have other exterior shapes (e.g., spherical, bulbous) as long as such shapes are atraumatic to vascular structures. The distal end of coil 16 is coupled to core wire 18 with the same solder joint or bulb which creates and defines tip 20.
Coils 14, 16 and especially coil 14 constitute a particularly important feature of this invention. Coil 14 is multifilar, having between 4 and 15, preferably 5 to about 12 filars or wires helically wound in the same direction. A sectional view of a 7 filar embodiment of coil 14′ is shown in
There is shown in
Of particular importance to obtaining the advantageous characteristics of the present invention is the helical angle defined by the substantially parallel lines of contact between adjacent helices of the coil. The helical angle is defined as the angle between a line of closest approach between adjacent or neighboring helices of the coil and a plane which includes and could rotate around the central axis of the coil (shown at 40, 40′ in
The determination of helical angle or alpha (α) angle is shown in
Illustrating the above calculation, assuming a 0.0015 inch filar diameter, dimension “D” of 0.014′, and a tightly wound coil the calculated α angles would be as follows:
Alpha helical angle is determined by the diameter of the filars, the tightness of the wrap and the number of filars in the coil. Generally speaking the helical angle of coils 14 of this invention will fall in the range of 5° to about 35°, preferably 6° to about 30°, and most preferably 7° to about 25°.
Multifilar coil 14 which is immediately proximal to coil 16 but is still disposed on the distal portion or segment of core wire 18 and comprises a superelastic material. Super elastic materials as the term is used herein are well known to this art. The preferred superelastic material for use herein is a nickel titanium alloy commonly known as nitinol. While metallic superelastic materials are well known, non-metallic e.g., polymeric, materials having the performance characteristics of super elastic metallic alloys could be used.
The vasculature that feeds the neuro-anatomy is referred to as the neuro-vasculature. The neuro-vasculature is deemed to begin at either the aortic branch (left carotid artery) or the brachiocephalic artery (right carotid artery). Near the jaw the carotid bifurcates into the external and internal carotid artery. The external carotid feeds the outer portions of the face and temporal regions such as the jaw and face. The internal carotid feeds the inner portion of the brain. It provides the life sustaining blood flow to the functioning part of the brain. Both branches are considered tortuous and difficult to navigate through with a guide wire.
The internal carotid artery has been mapped out to include common curvatures that are referred to as the Cervical segment (C1), Petrous segment (C2), Lacerum segment (C3), Cavernous segment (C4), Clinoid segment (C5), Ophthalmic segment (C6) and finally the Communicating segment (C7). At this point the vasculature joins into a feature called the Circle of Willis. These are a series of arteries that are anywhere from 1-4 mm in diameter and can have curvatures ranging in 3-7 mm in radius. These turns and other complicated arterial and venous structures of the neuroanatomy are difficult to navigate with a guide wire and commonly cause guide wires to camber and possibly kink. This creates complications when trying to steer the guide wire to the diseases location. The present guide wire has been found to be particularly advantageously used in navigating the neuro-vasculature.
