1. Field of the Invention
The present invention relates to surgical catheters, and more particularly to devices for removing thrombus, and other blockages and materials from blood vessels.
2. Background Information
Certain snare and similar devices have become available over recent years for retrieving malfunctioning or misplaced devices or blockages such as plaque and thrombus within the cardiovascular and non-vascular regions of the body. These typically consist of fairly large diameter sheaths, which house a movable central wire or wires whose distal ends are formed into a loop, plurality of loops or other purpose-built shape. The loop is used to ensnare and capture the desired object for withdrawal and removal from the body, while other shapes may be used to grasp or capture softer biological materials. In use, the snare or another distal tool is typically passed through a guiding catheter or other introducing catheter that is placed within the vasculature and is directed to the vessel or area where the misplaced or malfunctioning device is located. The snare/distal tool can then capture the intended device or material and retrieve it out of the body through the introducing catheter or by withdrawing both the snare and the introducing catheter in tandem.
Currently available snares and similar distal tools are generally designed using large diameter outer sheaths that require relatively large entry sites. This may result in complications such as excessive bleeding and/or hematomas. Additionally, because of the large diameter, it may be necessary to remove the existing catheters and exchange to other larger devices, resulting in an increase in the overall time and cost of the procedure. A third disadvantage of the old means is that the outer sheath, which is typically made of a plastic material, exhibits little or no torque control, which can make ensnaring the misplaced or malfunctioned device or removing other materials very difficult. Lastly, because of the size and stiff design of these snare/distal tool devices, they have a very sharp distal leading edge which cannot be safely advanced into small diameter vessels such as those in the coronary and cerebral vasculature without risking damage to the vessel wall.
An exemplary small-diameter snare design that overcomes many of the concerns above is provided in commonly owned U.S. Pat. No. 6,554,842, entitled SMALL DIAMETER SNARE by Heuser, et al., the teachings of which are expressly incorporated herein by reference. Devices, such as the exemplary Heuser design, are characterized by a small-diameter outer sheath that has a relatively thin wall (for example, approximately 0.0020 inch or less in wall thickness) so as to accommodate an axially movable/rotatable central core wire of approximately 0.008 inch. The structure allows a snare loop attached to the distal end of the core wire and housed within the open distal end of the sheath to be selectively extended from the sheath end, withdrawn and torqued. This sheath is at least partially composed of metal. However, the thinness of the tube, and its metallic content make it susceptible to splitting, fracturing and fatigue failure under stress. In addition, the metal section of the tubular outer sheath tends to experience permanent (plastic) deformation when bent, and once deformed, the central core wire will tend to bind upon the lumen of the sheath, rendering the device inoperable for its intended purpose. In addition, the outer wall of the metal tube section has a lubricious coating, such as PTFE (Teflon), which is typically approximately 0.0010 inch in thickness. This necessitates further downsizing of the sheath overall outer diameter thereby reducing the inner diameter available for accommodating the central core wire and at the same time increasing the risk of inadvertent failure of the device through breakage or plastic deformation.
Further considerations arise in the case of a non-snare device used to remove materials from blood vessels. Within the U.S. alone, approximately 700,000 strokes occur every year. The majority of these (83%) are ischemic strokes due to blood clots (thrombus) that become lodged in and block cerebral vessels. It has been documented that if the blockage can be eliminated within a short period of time (up to 8 hours), the patient can experience a full recovery from the stroke. Presently, clot-dissolving drugs can be administered to break up the clot and restore blood flow, however these drugs must be administered within 3 hours of symptom onset as they take considerable time to become effective. Unfortunately, not all patients are medically eligible to receive these drugs and even those who otherwise are eligible often do not arrive for medical treatment within the 3 hour limit. In these patients, mechanical removal of the blood clot has been shown to have a significant positive outcome for such patients.
Several devices have been designed to break up and suction-out thrombus in the large vessels of the legs and coronary arteries. These use a variety of therapeutic means to accomplish the breaking up, such as water jets, mechanical maceration, ultrasound or photo-acoustic shock waves, and laser ablation. All of these devices, however, have limitations when working in the cerebral vessels. First, they tend to be large and bulky and very difficult or impossible to navigate above the skull base. Secondly, their therapeutic means can be extremely vigorous, resulting in damage to the delicate blood vessels in the brain. In use, the devices require removal of an already placed microcatheter, and the insertion of a replacement catheter that accommodates the device.
One such device that is used to treat blood clots is a mechanical capture device whereby the blood clot is grasped and pulled out of the distal vessels of the brain. The MERCI retrieval device (available from Concentric Medical of Mountain View, Calif.) is a 0.014-inch guidewire that can be passed through a catheter and into the blood clot as a straight wire and then can be remotely shaped into a corkscrew configuration (e.g., by extending the straight wire out of a surrounding sheath, thus “springing” into the pre-shaped corkscrew), becoming intertwined within the blood clot. The wire is then withdrawn from the distal cerebral vessel pulling the blood clot with it. Although this device addresses the ability to navigate above the skull base, it has one major shortcoming, namely, the corkscrew segment of the wire must be very soft and flexible in order to navigate within the brain. This reduces the ability of the device to remain in the cork-screw shape as it is withdrawing the blood clot. During withdrawal, the wire can straighten and the blood clot can be partially or fully released resulting in greater injury to the patient through thromboembolism. A more effective tool for removal of thrombus reduced risk of release or breakup and the ability to navigate smaller blood vessels is highly desirable.
This invention overcomes prior disadvantages by providing a device (e.g., a small-diameter device) for removing thrombus and other materials from vascular lumens consisting of a hollow, elongate (e.g., thin-walled) outer sheath, a core/actuating wire, and a capture mechanism. The sheath may be constructed from polymer, e.g., at least at a distal part thereof for enhanced flexibility and can be metal at an adjoining proximal part for added strength. A single central core wire extends through the entire length of the sheath. The outer diameter of the core wire is sized close to the inner diameter of the sheath while allowing for axial sliding, in order to maximize the support to the body portion of the snare device. The distal end of the core wire has a tapered section of reduced diameter or cross section to provide a “guidewire-like” flexibility to the distal portion of the device. Also, a tool tip (or “capture segment”) for removal of thrombus is provided at the distal end of the sheath and core wire that can be controllably expanded to engage a thrombus and remove the thrombus from the blood vessel. In particular, the controllably expansive capture segment may illustratively comprise a braided or meshed screen-like material adapted to open and close around a thrombus.
In use, the controllably expansive thrombus removal tool tip is collapsed by pushing on the actuating handle. The device is then advanced into a balloon or guiding catheter until the distal end of the core wire has reached (exited) the distal end of the thrombus. The tool tip is then expanded by pulling the actuating handle backward; and the radially extended (expanded) tool tip is moved to receive and substantially surround (e.g., encompass) the thrombus. The tool tip may then be collapsed again by pushing on the actuating handle to engage (tighten around) the thrombus, and the device may be withdrawn from the patient's body through the vascular system with the thrombus engaged by the tool tip.
The invention description below refers to the accompanying drawings, of which:
A. Thrombus Retrieval Device and General Design Details
In one embodiment, the sheath is constructed from polyimide with a tungsten filler for radiopacity. The radiopaque filler may be added to the sheath polymer during processing, or a radiopaque material may be added to the outer surface via vapor deposition, plating, ion implantation processes, or the like. Alternatively, radiopaque markers can be applied at the distal end and/or other known locations along the sheath, and thus, an overall tungsten filler/radiopaque coating can be omitted. As discussed further below, the outer surface can include thereon a polytetrafluoroethylene (PTFE or “Teflon”) coating upon some, or all, of its outer surface for enhanced lubricity. Alternatively, the outer sheath coating can be constructed form a hydrophilic material that provides lubricity, instead of a PTFE coating. The sheath polyimide material is commercially available for a variety of vendors and sources and is becoming accepted in a variety of medical device applications. It has the property of allowing a very strong, thin-walled cylindrical-cross section tube to be made therefrom, with wall thicknesses on the order of approximately 0.00075 inch to 0.010 inch in normal applications. Nevertheless, the resulting polyimide tube can withstand high pressures in excess of 750 PSI when employed in the size range of the sheath of this invention. Polyimide also resists high temperatures, as much as 1000 degrees F., or greater. Accordingly, polyimide is desirable as a sheath material based upon all of the above-described superior performance characteristics. Nevertheless, it is expressly contemplated that other equivalent plastic/polymer materials suitable for forming a thin-walled sheath tube with similar or better properties (e.g. high strength, thin wall-thickness limits, small diametric sizing) may also be employed as an acceptable “polymer” herein.
The outer sheath 102, which forms the main support and outer framework of the device 100 has an overall length sufficient to traverse the body's varied vasculature, and is (for most applications) permissibly in a range of between approximately 20 cm and 500 cm (more typically between 120 cm and 300 cm), such as depending upon (among other factors) the location of the insertion point into the body cavity/vasculature, and the location of the target thrombus, or other material, to be acted upon by the device. The outer diameter DSO of the sheath is, for most applications, in a range of between approximately 0.010 inch to 0.045 inch (more typically between 0.010 inch and 0.021 inch), although the diameter may fall within the range of 0.008 inch to 0.250 inch. In general, where the outer diameter is less than 0.35 inch, the device 100 may fit easily through a standard balloon catheter.
A single central core wire (or “actuating wire”) 110 extends through the entire length of the sheath 102. The outer diameter DC of the body of the core wire is sized close to the inner diameter DSI of the sheath while allowing for axial sliding (double arrow 112), in order to maximize the support imparted by the core wire 110 to the body portion/sheath 102 of the snare device 100. (For instance, example guidewire dimensions are 0.014 inch and 0.035 inch diameters.) The distal end 114 of the core wire 110, however, may have a tapered section 116 of reduced diameter or cross section to provide a “guidewire-like” flexibility to the distal portion of the device. According to one or more illustrative embodiments, a tool tip or capture segment 122 (shown collapsed) may extend from the end of the sheath configured in a manner described herein so as to increase the ability to ensnare and capture objects (e.g., a thrombus). Capture segment 122 may be attached at a proximal end 126 to the outer sheath 102, and at a distal end 128 to the distal-most portion 130 of the central core wire 110, as described further below. For example, depending upon its materials and configuration, the capture segment 122 may be attached at its ends via welding, soldering, brazing (or other high-strength metal-flowing means), adhesives, wrappings, sewing, etc. The core wire 110 may be further secured slideably to the outer sheath (e.g., through a loop, not shown) in order to maintain the core wire's orientation to one side of the capture segment 122.
The central core wire 110 may be made from metal for flexibility and strength. In one embodiment, the central core wire 110 may be made by connecting a proximal stainless steel portion, for support and stiffness, to a distal nitinol portion, for torqueability and kink resistance. Likewise, it can be made from 300-series stainless steel or a stronger, heat settable material such as 400-series stainless steel, alloy MP35N, a chromium-cobalt alloy such as Elgiloy, or nitinol in its super elastic or linear elastic state.
Note, because a thin-walled polymer sheath is illustratively employed, it advantageously allows for a maximized central core wire diameter, which in turn, provides stiffness for torque control and axial pushability of the device. In this and other embodiments described herein, however, the sheath can be all polymer along its entire length, or can be constructed from a combination of polymer and metal. For example, the distal part of the sheath can be the above-described polyimide material (or another appropriate polymer), while the proximal part can be constructed from 300-series stainless steel or any other appropriate metal. This affords the desired flexibility in the distal part, while providing greater strength and rigidity against buckling in the proximal part. Flexure is required less and beam strength (so as to assist in driving the device distally) is required more in the proximal part. The distal part may be joined to the proximal part at a joint (not shown) located at a predetermined distance along the device. The joint can be accomplished using adhesive or any other acceptable joining technique. In one example, the polymer distal part is approximately 40 centimeters in length, while the metal proximal part is approximately 140 centimeters in length. These measurements are widely variable depending upon the overall length of the sheath, the purpose of the device (e.g. where it will be inserted) and the distance of the distal part in which high flexibility is required.
After assembly of the core wire 110, its insertion into the sheath 102, and the attachment of the capture segment 122, a second short, hollow tube may be fitted over the proximal end 152 of the central core wire 110 and attached thereto by a filler or adhesive 154 to provide an actuating handle 150 so as to slideably move the central core wire axially (as indicated by double arrow 112) within the sheath 102, thus selectively expanding and contracting the capture segment 122 at the open distal end 104 of the sheath 102. In one embodiment, the actuating handle 150 may be sized with an outer diameter DOO similarly (or identically) in outer diameter DSO to the main body of the sheath 102. The exposed proximal end 152 of the core wire 110 may include a narrowed-diameter end 160, with a special connection so that an additional length of wire 166 can be attached to it, thereby extending the overall length of the snare device. This extension may have a similarly sized outer diameter DA to that of the handle 150 (DOO) and sheath 102 (DSO). The attachment of this similarly small-diameter extension allows for the exchange of one catheter for another catheter over the body of the snare (and extension). The entire device when complete (including the actuating handle 150) can be made less than 0.014 inch in overall outer diameter, and is therefore capable of being placed directly through a PTCA balloon catheter or other small-diameter catheter 180, having a sufficiently large inner diameter CD, that may already be in place within the patient (e.g. CD>DSO). Since the actuating handle is equally small in diameter, it also passes through the small-diameter catheter with an extension piece joined behind the handle to the attachment end 160, and thereby allowing the device to be guided even deeper into the patient when needed. The capture segment and device may also be passed through the guiding catheter along side of the balloon or access catheter without the need to remove the prior device and, thus, lose temporary access to the site within the patient. For example, the device 100 may be initially passed through the PTCA balloon catheter, which is already located within the target area. The balloon catheter can then be removed and replaced with a larger-inner diameter catheter to allow removal of the object (e.g., thrombus).
The actuating handle 150 may consist of a metal or a polymer tube. In an alternate embodiment (not shown) the actuating handle may consist of a tube slideable within a second metal tube that is attached to the proximal end 170 of the sheath to maintain an axial orientation between the proximal end of the core wire 102 and sheath, thereby minimizing permanent bending or kinking of the core wire at or near this proximal location.
While the depicted actuating handle 150 is of similar outer diameter as the sheath 102, it is expressly contemplated (where the handle will not be passed into another catheter) that the actuating handle may be made in a diameter significantly larger than the snare device so that it may also serve as a torquing handle, similar to those utilized in routine small-diameter guidewire placement.
The handle attachment 202 includes a base ring 210 that is secured to the outer surface of the proximal end 170 of the sheath 102. In a detachable-handle embodiment, the ring can consist of a conventional lockable collet structure in which turning of an outer element reduces the diameter of an inner locking element to deliver securing hoop stress to the distal end 170 outer surface of the sheath 102. The base ring is connected to two or more ribs 212 and 214 that are also shown in cross section in
A second actuating ring 220 is secured onto the actuating handle 150 either permanently or detachably. Where it is detachable, the ring may also utilize a locking collet structure (not shown) as described above. The ring 220 includes at least two apertures 230 and 232 to allow passage of the respective ribs 212 and 214 through the ring, such that the ring 220, actuating handle 150 and core wire 110 can slide axially (double arrow 240) to move the core wire with respect to the sheath 102. The ribs, with their square or rectangular cross-section prevent rotation of the ring 220 and interconnected core wire 110 and handle 150 relative to the sheath. The connection is sufficiently strong so that rotation of the handle assembly 202 causes torquing of the entire device so as to rotate the capture segment 122 (in one or more embodiments) into a desired rotational orientation. In an alternate embodiment, the ring 220 may have a non-circular cross-section. In another alternate embodiment (also not shown), the ring 220 may also allow at least limited rotation of the core wire relative to the sheath by utilizing arcuate slots at the ribs.
The handle assembly 202 includes a rear gripping member 250 that connects to the proximate ends of the ribs 212 and 214. The gripping member remains outside the body and is sized to provide an ergonomic hand piece for a practitioner during a procedure. In one embodiment the member 250 has an outer diameter of approximately ½ to ¾ inch and an external length of approximately 4 to 5 inches. However, it is expressly contemplated that both these dimensions are widely variable outside the stated ranges herein. The member 250 defines an inner cylindrical barrel 252 having an inner diameter sized to slideably receive and guide the proximal end of the actuator handle 150. The barrel 252 is sufficiently long so that its inner end wall 262 (of end cap 260) is not struck by the end 160 of the device at maximum withdrawal (as approximately shown) of the core wire 110 into the sheath 102 (for expansion of capture segment 122, as described below).
Coatings can be applied to the outer surfaces of each of the core assembly and the sheath assembly to reduce friction between the core and the tube as well as to enhance movement of the retrieval device within a catheter. In one embodiment, a lubricious coating, such as PTFE (Teflon), hydrophilic, or diamond-like coating (DLC) may be applied to the outer surface of the sheath to reduce friction. Likewise, one of these coatings may be applied to the outer surface of the core wire to reduce friction with respect to the sheath. Since the coating adds a quantifiable thickness to the thickness of the sheath and/or diameter of the core wire, the overall size of components should be adjusted to compensate for the thickness of any lubricating coating. For example, the outer diameter of the sheath may need to be reduced to maintain a desired 0.035-inch or less outer diameter. Likewise, the thickness of the uncoated wall of the sheath may be reduced to maintain the desired inner diameter and create a final wall thickness, with coating, of approximately 0.0020 inch.
B. Controllably Expansive Thrombus Retrieval Device
Having described the general structure of the device, a more specific description of the braided mesh/screen capture segment is now described with reference to
The proximal end of the braided capture segment 403 may be attached about its periphery to the distal end of the outer sheath 401, at point 404, and the distal end of the braided capture segment may be attached at (or along) one side to the distal end 405 of the actuating wire 402. The distal end of the capture segment thus remains open when the capture segment is in its expanded state, thus creating a void within the capture segment for receiving a thrombus or other material. For example, the mesh/screen material may, though need not, be pre-formed, such by heat setting or other process (e.g., pre-bending), to create a desired shape when expanded (and/or when compressed/collapsed) to optimize capturing ability, such as the open shape as shown. Notably, while a single core wire attachment is shown, a plurality of attachments (e.g., for a split core wire 402) may be made, so long as the distal end of the capture segment generally consists of one or more opening that are sufficient in size to capture a thrombus as described herein. Also, while the core wire 402 is shown on the inside of the capture segment 403, other locations may be possible, such as on the outside of the capture segment or within the capture segment (that is, a part of and thus neither inside nor outside the capture segment) as may be appreciated by those skilled in the art.
In operation, as shown in
In particular, for controlling expandability operation of this embodiment, when the actuating/core wire 402 is advanced forward, as shown in
As noted, in a collapsed state, the OD of the capture segments may be sized substantially similar to the OD of outer sheath itself (e.g., no greater than an ID of a catheter in which the outer sheath/device is meant to traverse). In an expanded state, the capture segment extends to approximately the vessel diameter so that it may be used to capture a thrombus or other material within the vessel. The capture segment may then be collapsed to move the thrombus/material, e.g., removing it from the vessel or otherwise repositioning the thrombus/material to another location. The range of radial extension of a fully-deployed tool tip or other capture segment is highly variable. It can be anywhere from 1 millimeter to 100 millimeters in various embodiments. This radial sizing depends partly upon the size of the space into which the capture segment is being inserted. More typically, a capture segment will have maximum radial extension between approximately 2 millimeters and 35 millimeters. In other words, the radial projection (RT) of the distal tool tip should be sufficient to surround the approximate dimension of the thrombus/material to be cleared, yet remain smaller than the inner diameter of lumen of any vessel through which the deployed tool is expected to carry. This helps to reduce the chance of injury to vascular walls. The distal-to-proximal length (LT) is also highly variable, depending upon the position of the core wire, and the current and/or desired radial projection.
Notably, in alternative or additional embodiments a distal atraumatic spring portion may be added to the distal end of the core wire to facilitate movement through the blood vessels without causing damage. In particular, as shown in
Further, in addition or in the alternative, the outer sheath 401 may contain a flexible coil portion on its distal end. For example,
In each embodiment described herein, the mesh/screen of the capture segment 403 is straightened out and thus collapsed for insertion of the device into the body when the actuating core wire is advanced, and expanded (e.g., enlarged or opened) when the core wire is retracted/withdrawn. The capture segment 403 may then be re-collapsed (e.g., around a thrombus) by advancing the actuating core wire 402. Also, in use, the actuating wire may be withdrawn or advanced and locked in position as described above, such that the capture segment remains in the capture/collapsed state to remove the thrombus or move the thrombus/material to a desired location, as described below.
Note that each of the tool designs described herein is by way of example. For instance, the size of the capture segment can be varied based upon the size of the target vessel, as well as the size and characteristics of the material being engaged. Further, while the capturing segment is illustratively shown as a symmetric design, the segment 403 may be configured in multiple fixed diameters, or as other pre-configured shapes and/or varying diameters not explicitly shown. These illustrations, therefore, are merely representative, and should not be limiting on the scope of the present invention.
C. Procedures for Withdrawal of Thrombus and Other Materials with Controllably Expansive Capture Segments
Having described the general structure of the device and more specifically an illustrative braided mesh/screen capture segment, a procedure of removing a thrombus or other material from a blood vessel is now described in further detail.
Once positioned adjacent to the thrombus 806, the core/actuating wire 402 is withdrawn allowing the capture segment 403 to expand into its open state, e.g., substantially sized to the inner diameter of the vessel 815, as illustrated in
Once the thrombus 806 is enclosed within the capture mechanism 403, the core/actuating wire 402 is re-advanced causing the capture mechanism 403 to collapse around the thrombus 806, thereby providing a secure capture of the thrombus/material (
The capture segment may instead be maintained in its collapsed state, pushed through and into the thrombus so that the capture segment resides at least partially within the thrombus, and then expanded by withdrawal of the core wire, allowing the capture mechanism to expand outward into the thrombus. The device may then be withdrawn, removing the thrombus from the vessel (e.g., from patient's body), while maintaining outward pressure from within inside the thrombus.
The above-described insertion procedures can be modified to accommodate the characteristics of the particular tool tip shape and size. A variety of additional tools and/or internal scanning devices can be employed to facilitate the procedure in accordance with known medical techniques. Note also that the proximal end of the thrombus-removal device described herein includes a proximal end that allows removal of the actuator handle and addition of a small-diameter extension. When the extension is added, the practitioner can pass another catheter over the inserted device sheath, thereby using the device as a guide for the larger diameter catheter.
Notably, the controllably expansive capture segments described above should be substantially sized in its expanded state so that it approximates the vessel diameter. For instance, vessel diameters where such a device may be used can typically range from 1 mm to greater than 35 mm, however, most thrombus retrieval procedures are performed in vessels ranging between 1 mm and 10 mm. In this manner, the capture of the thrombus is assisted by substantially allowing the capture segment to more fully surround and encompass the thrombus.
Further, in accordance with one or more embodiments of the present invention, the capture segment may be advantageously coated with a material to attract a thrombus, such as an ionic charge, or may include brushes and/or filaments (not shown). Also, the capture segment may be coated with a thrombus dissolving drug, such as Integrelin®, ReoPro®, or other thrombolytic agents as will be understood by those skilled in the art. Alternatively or in addition, the device may be constructed with a gap between the outer sheath and the actuating/core wire in order that localized drugs (e.g., thrombolytics) may be infused through the outer sheath and delivered directly to the thrombus.
The thrombus removal devices described herein may also operate to open the impeded vessel to allow blood flow. While removal of the thrombus is discussed above, the embodiments may instead be maneuvered within or proximate to the thrombus to puncture and/or break up the thrombus. Also, the thrombolytic agents applied to the capture segment may allow the capture segments to more readily enter/pass through the thrombus to puncture and/or break up the thrombus.
The foregoing has been a detailed description of illustrative embodiments of the invention. Various modifications and additions can be made without departing from the spirit and scope of this invention. For example, while specified materials are described, it is expressly contemplated that similar or superior materials may be employed if and when available for the described components of this invention. In particular, a variety of metals, polymers, composite, nano-materials and the like having desirable memory characteristics can be employed for capture segments and other components herein. Likewise, alternate techniques and materials can be employed for joining components. In addition further attachments can be provided to the devices described herein, with appropriate mounting hardware and locations to facilitate other, non-described procedures using the device. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of the invention.
The present application is related to commonly assigned copending U.S. patent application Ser. No. 12/098,201, which was filed on Apr. 4, 2008, by Richard M. DeMello, et al. for a SYSTEM AND METHOD FOR REMOVAL OF MATERIAL FROM A BLOOD VESSEL USING A SMALL DIAMETER CATHETER, which is a continuation-in-part of commonly assigned copending U.S. patent application Ser. No. 11/583,873, which was filed on Oct. 19, 2006, now published as U.S. Publication No. US2007-0118165 on May 24, 2007, by Jonathan R. DeMello, et al. for a SYSTEM AND METHOD FOR REMOVAL OF MATERIAL FROM A BLOOD VESSEL USING A SMALL DIAMETER CATHETER, which is a continuation-in-part of U.S. patent application Ser. No. 11/074,827, which was filed on Mar. 7, 2005, now published as U.S. Publication No. US2005-0234474 on Oct. 20, 2005, by Richard M. DeMello, et al. for a SMALL DIAMETER SNARE, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/551,313, which was filed on Mar. 8, 2004, by Richard M. DeMello et al., for a SMALL-DIAMETER SNARE, each of which are hereby incorporated by reference.