CATHETER HAVING RETRACTABLE SHEATH
Field of the Invention
[0001] The invention relates to catheters, and specifically to a catheter having a retractable sheath and configured to be advanced within a patient's body.
Background of the Invention
[0002] Stents and other prostheses for implantation in body canals, such as blood vessels, for repair or dilation are known in the art. Stents can be formed from various materials and using different designs. Many stents require a balloon catheter or similar device to forcibly expand the stent from its small delivery diameter to a larger deployed diameter. Another type of stent is the so- called self-expanding stent, which is biased toward an enlarged diameter so that it will self-expand when released.
[0003] Atherosclerosis is the deposition of fatty plaques on the luminal surface of arteries, which in turn causes narrowing of the cross-sectional area of the artery. Ultimately, this deposition blocks blood flow distal to the lesion causing ischemic damage to the tissues supplied by the artery. Atherosclerosis of the arteries, coronary or peripheral, is a pervasive disease. For example, coronary artery atherosclerosis disease (CAD) is the most common, serious, chronic, life-threatening illness in the United States, affecting more than 11 million persons. The social and economic costs of atherosclerosis vastly exceed that of most other diseases. Narrowing of the coronary artery lumen causes destruction of heart muscle resulting first in angina, followed by myocardial infarction and finally death. There are over 1.5 million myocardial infarctions in the United States each year, and six hundred thousand (or 40%) of those patients suffer an acute myocardial infarction and more than three hundred thousand of those patients die before reaching the hospital (Harrison's Principles of Internal Medicine, 14th Edition, 1998). Narrowing of the peripheral arteries can be debilitating and can severely affect the quality of life of afflicted patients.
[0004] A number of percutaneous intravascular procedures have been developed for treating stenotic atherosclerotic regions of a patient's vasculature to restore adequate blood flow. Among the most successful of these treatments is percutaneous transluminal angioplasty (PTA), In PTA, a catheter having an expansible distal end, usually in the form of an inflatable balloon, is inserted into a peripheral artery and threaded through the arterial system into the blocked artery and is positioned in the blood vessel at the stenotic site. The balloon is then inflated to flatten the obstructing fatty plaque and dilate the vessel, thereby restoring adequate blood flow beyond the diseased region. Other procedures for opening stenotic regions include directional arthrectomy, rotational arthrectomy, laser angioplasty, stenting, and the like. While these procedures have gained wide acceptance (either alone or in combination, such as PTA in combination with stenting), a disadvantage of PTA and other known procedures for opening stenotic regions is the frequent occurrence of restenosis.
[0005] Restenosis refers to the re-narrowing of an artery after an initially successful angioplasty. Restenosis afflicts approximately up to 50% of all angioplasty patients, and can be the result of injury to the blood vessel wall during the lumen opening angioplasty procedure. In some patients, the injury initiates a repair response that is characterized by smooth muscle cell proliferation referred to as "hyperplasia" in the region traumatized by the angioplasty. Acutely, restenosis can involve recoil and shrinkage of the vessel, followed by proliferation of medial smooth muscle cells. This proliferation of smooth muscle cells re-narrows the lumen that was opened by the angioplasty within a few weeks to a few months, thereby necessitating a repeat PTA or other procedure to alleviate the restenosis. Many patients who are treated by PTA require a repeat procedure within six months to correct restenosis. [0006] Narrowing of the arteries can occur in vessels other than the coronary arteries, including, but not limited to, the aortoiliac, infrainguinal, distal profunda femoris, distal popliteal, tibial, subclavian, mesenteric, carotid, and renal arteries. Peripheral artery atherosclerosis disease ("PAD", also known as peripheral arterial occlusive disease) commonly occurs in arteries in the extremities (feet, hands, legs, and arms). Rates of PAD appear to vary with age, with an increasing incidence of PAD in older individuals. One set of data from the National Hospital Discharge Survey estimates that every year, 55,000 men and 44,000 women have a first-listed diagnosis of chronic PAD and 60,000 men and 50,000 women have a first-listed diagnosis of acute PAD. Ninety-one percent of the acute PAD cases involved the lower extremity. The prevalence of comorbid CAD in patients with PAD can exceed 50%. In addition, there is an increased prevalence of cerebrovascular disease among patients with PAD.
[0007] A number of different techniques have been used to overcome the problem of restenosis, including treatment of patients with various pharmacological agents or mechanically holding the artery open with a stent or synthetic vascular graft (Harrison's Principles of Internal Medicine, 14th Edition, 1998). Of the various procedures used to overcome restenosis, stents have proven to be among the most effective. Stents are small tubular scaffolds, often formed of metal, that are permanently implanted in the diseased vessel segment to hold the lumen open and improve blood flow. Placement of a stent in the affected arterial segment thus prevents recoil and subsequent closing of the artery.
[0008] There are broadly two types of stents: self-expanding stents and balloon expandable stents. Stents are typically formed from malleable metals, such as 300 series stainless steel, or from resilient metals, such as super-elastic and shape memory alloys, e.g., Nitinol™ alloys, spring stainless steels, and the like. They can also, however, be formed from non-metal materials such as non- degradable or biodegradable polymers or from bioresorbable materials such as levorotatory polylaclic acid (L-PLA), polyglycolic acid (PGA), or other materials such as those described in U.S. Patent No. 6,660, 827.
[0009] A variety of stent geometries are known in the art, including, without limitation, slotted tube type stents, coiled wire stents and helical stents. Stents are also classified into two general categories based on their mode of deployment. The first type of stent is expandable upon application of a controlled force, such as the inflation of the balloon portion of a dilatation catheter that upon inflation of the balloon or other expansion device expands the compressed stent to a larger, fixed diameter to be left in place within the artery at the target site. The second type of stent is a self-expanding stent formed from shape memory metal or super-elastic alloy such as nickel-titanium (NiTi) alloys that automatically expands or springs from a compressed state to an expanded shape that it remembers.
[0010] Exemplary stents are described in U.S. Pat. No. 4,553,545 to
Maass et al.; U.S. Pat. Nos. 4,733,665 and 4,739,762 to Palmaz; U.S. Pat. Nos. 4,800,882 and 5,282,824 to Gianturco; U.S. Pat Nos. 4,856,516, 4,913,141, 5,116,365 and 5,135,536 to Hillstead; U.S. Pat. Nos. 4,649,922, 4,886,062, 4,969,458 and 5, 133,732 to Wiktor; U.S. Pat. No. 5,019,090 to Pinchuk; U.S. Pat. No. 5,102,417 to Palmaz and Schatz; U.S. Pat. No. 5,104,404 to Wolff; U.S. Pat No. 5,161,547 to Tower; U.S. Pat. No, 5,383,892 to Cardon et al.; U.S. Pat. No. 5,449,373, 5,733,303, 5,843,120, 5,972,018, 6,443,982, and 6,461,381 to Israel et al.; U.S. Pat Nos. 5,292,331, 5,674,278, 5,879,382 and 6,344,053 to Boneau et al.; U.S. Pat. Nos. 5,421,955, 5,514,154, 5,603,721, 5,728,158, and 5,735,893 to Lau; U.S. Pat. No. 5,810,872 to Kanesaka et al.; U.S. Pat. No. 5,925,061 to Ogi et al.; U.S. Pat. No. 5,800,456 to Maeda et al.; U.S. Pat. No. 6,117,165 to Becker; U.S. Pat. No. 6,358,274 to Thompson; U.S. Pat. No. 6,395,020 to Ley et al.; U.S. Pat. Nos. 6,042,597 and 6,488,703 to Kveen et al.; and U.S. Pat. No. 6,821 ,292 to Pazienza et al. [0011] Stents are usually delivered in a compressed condition to the target site, and then deployed at that location into an expanded condition to support the vessel and help maintain it in an open position. The delivery system used to implant or deploy the stent at the target site in the diseased vessel often comprises a catheter that carries the stent as well as a control system that allows the stent to be deployed from the catheter into the vessel.
[0012] A common method for using such a stent delivery system is to advance the catheter into the body of a patient by directing the catheter distal end percutaneously through an incision and along a body passage until the stent is located within the desired site. The term "desired site" refers to the location in the patient's body currently selected for treatment by a health care professional. After the stent is deployed at the desired site, it can (depending on the particular stent involved) tend to resiliently expand to press outward on the body passage.
[0013] Like many catheter systems, a stent delivery system is often used with a flexible guidewire. The guidewire is often metal, and is slidably inserted along the desired body passage. The catheter system is then advanced over the guidewire by "back-loading" or inserting the proximal end of the guidewire into a distal guidewire port leading to a guidewire lumen defined by the catheter system.
[0014] Many catheter systems include guidewire lumens that extend along the most of or the entire length of the catheter. Such catheter systems are described as "over-the-wire" catheters, in that the guidewire resides inside a catheter lumen throughout the length of the catheter. In some circumstances it may be desirable to provide a "rapid-exchange" catheter system, which offers the ability to easily remove and exchange the catheter while retaining the guidewire in a desired position within the patient. Rapid exchange catheters are disclosed in U.S. Pat. Nos. 5,380,283 and 5,334,147 to Johnson; U.S. Pat. No. 5,531,690 to Solar; U.S. Pat. No. 5,690,644 to Yurek et al.; U.S. Pat. No. 6,613,075 to Healy et al; and U.S. Re. Pat. No. 36,104 to Solar. Use of coils in catheters can be found in U.S. Pat. No. 5,279,596 issued to Castaneda et al. on Jan. 18, 1994. The use of braiding reinforcing layers can be found in U.S. Pat. No. 3,585,707 issued to Stevens on Jun. 22, 1971 ; U.S. Pat. No. 5,045,072 issued to Castillo et al. on Sep. 3, 1991; and U.S. Pat. No. 5,254,107 issued to Soltesz on Oct. 19, 1993.
[0015] Rapid-exchange dilatation catheters are capable of advancement into the vascular system of a patient along a pre-positioned guidewire for balloon angioplasty or similar procedures. The guidewire occupies a catheter lumen extending only through a distal portion of the catheter. With respect to the remaining proximal catheter portion, the guidewire exits the internal catheter lumen through a proximal guidewire port, and extends in parallel along the outside of the catheter proximal portion. The entire catheter and guidewire assembly is often contained within the lumen of a guiding catheter, which retains a majority of the catheter and guidewire effective lengths together.
[0016] Because most of the guidewire in a rapid-exchange assembly is outside the catheter shaft, it may be manually held in place as the catheter is removed. Moreover, because the distal catheter guidewire lumen is shorter than the guidewire length that remains outside the patient, the catheter may be removed while also holding the guidewire in place, until the guidewire may be grasped at a point distal of the catheter. Completing a catheter exchange with rapid-exchange catheters simply requires reversing the removal process. This rapid exchange technique enables a single physician to exchange balloon catheters, without requiring guidewire extension to temporarily double the guidewire length.
[0017] Stent delivery systems can possess certain characteristics. For example, the stent delivery system can protect the stent from damage or deformation during delivery. It may further be desirable that the stent delivery system be flexible and able to push through and traverse as many different anatomical arrangements and stenosis configurations as possible. In addition, the stent delivery system may be configured to provide for high visibility under fluoroscopy. Often the stent delivery system will be used in conjunction with an outer guiding catheter, which surrounds and guides the stent delivery system to the desired site. The visibility of the stent delivery system on a fluoroscope may be affected by the size of the lumen through which radiopaque contrast fluid is injected. This fluid is generally injected through the annular space between the guiding catheter and the stent delivery system. The visibility in such systems can, therefore, be increased by further reducing the outer diameter of the stent delivery system .
[0018] Moreover, the stent delivery system may have a positive mechanism for retaining the stent on the catheter prior to deployment and then releasing and deploying the stent at the desired site. Thus, a delivery system for implanting a self-expanding stent may include an inner catheter or tube upon which the compressed or collapsed stent is mounted and an outer restraining sleeve or sheath that is initially placed over the compressed stent prior to deployment. When the stent is to be deployed in the body vessel or accurately positioned at a damaged site, the outer sheath is moved in relation to the inner tube to "uncover" the compressed stent, allowing the stent to assume its expanded condition. Some delivery systems utilize a "push-pull" type technique in which the outer sheath is retracted while attempting to retain the inner lumen stationary. The delivery system may also use an actuating wire that is attached to the outer sheath. When the actuating wire is pulled to retract the outer sheath and deploy the stent, the inner lumen remains stationary, preventing the stent from moving axially within the body vessel. Many different types of delivery systems have been developed for delivering self- expanding stents, but most require a retractable outer sleeve or sheath.
[0019] Because of the narrowness of the human vascu lature, self- expanding stents are generally retained in a highly compressed state within the outer sleeve or sheath. As a result of the compressive forces necessary to compress the stent to a small diameter within the sheath or sleeve, relatively large forces may be required to retract the sheath from the stent. Currently, some stent delivery systems utilize hand held devices with pivoting levers to provide the necessary forces to retract the sheath from the stent, i.e., deploy the stent. Examples of devices related to medical delivery of devices or guide wires are shown in U.S. Patent Publication Nos. 2006/0173524, published on August 3, 2006, 2007/0043430, published February 22, 2007, and 2007/0060999, published on March 15, 2007. Others are shown in U.S. Patent Nos. 3,835,854, 6,187,015, 6,290,675, and 7,207,995.
[0020] Another issue related to the placement of self-expanding prostheses such as stents is the speed of stent deployment, which is often governed by the speed of withdrawal of the surrounding sheath from around the stent. If the sheath is initially withdrawn too rapidly, the stent may expand more rapidly than desired, and the stent distal end may even move from the desired deployment position. However, once the distal end of the stent is released and the stent distal portion has expanded in the desired position, a user may then desire to increase the speed of sheath withdrawal. A variable-speed delivery system can allow the self-expanding stent to be deployed slowly at first to allow the stent to be accurately positioned at a target site within the vasculature. Once positioned and impinged against the inner vessel wall, is often desirable to provide for more rapid deployment to maintain the position and to increase the speed of the overall procedure. As more of the stent impinges against the wall of the body lumen, the speed of deployment can continue to increase because there is more stent contacting the wall and resisting movement of the stent from its originally deployed position and, therefore, less risk of the stent movement. Hence, there is a need for an improved system for delivery and/or deployment of self-expanding devices or other medical devices that provides the user with the ability to vary the speed of sheath withdrawal in a smooth and predictable manner. The current invention fulfills this need, as set forth below. Summarv of the Invention
[0021] The invention relates to a medical device deployment system with a variable angle of attack (and/or alternatively a variable pitched) drive screw. In one embodiment, and by way of example only, the an apparatus and method for stent deployment has a protective sheath is withdrawn in a variable- speed process. In a first or initial stage, the protective sheath is withdrawn slowly. At a selected time in the initial withdrawal of the protective sheath, such as once the stent has begun to deploy, a second stage of withdrawal can be initiated wherein the protective sheath is withdrawn more rapidly than in the first or initial stage. In a further embodiment of the invention, the speed of sheath withdrawal can continuously increase as the sheath is withdrawn. Sheath withdrawal can be driven by physical force applied by a user and/or by a motor.
[0022] In one embodiment of the invention, a system includes a catheter and stent, which may be a self-expanding stent. The catheter includes a sheath passing from around the stent at the catheter distal end to a point just proximal of the catheter handle. As the sheath passes through the catheter handle, it is driven by gears and/or one or more drive wheels that are driven by a motor, rotating knob, or other rotation control device that can be activated by a user.
[0023] The sheath may include a split, either along its entire length or just in a selected portion, which permits internal structures of the catheter to pass within the sheath. The catheter may include a cutting blade or similar device configured to lengthen the sheath split as the sheath is withdrawn.
[0024] The catheter may be configured to vary the speed of sheath withdrawal. In one embodiment, a motor provides a generally constant speed of rotation while gearing elements or other devices provide a varying speed of sheath withdrawal in response to the constant rotation of the motor. In a further embodiment the motor has a variable speed that can be adjusted by the user, [0025] In an embodiment of the invention, the user physically rotates or otherwise moves a drive element, and gearing elements and/or other devices provide a varying speed of sheath withdrawal in response to the rotation of the drive element.
[0026] The catheter may include a removable portion that the user can pull off of the main catheter handle. The removable portion may be secured to a portion of the sheath, and/or may be configured to grasp a proximal portion of the sheath and be withdrawn quickly in a proximal direction, so that the sheath is also rapidly moved proximally along with the removable portion of the handle.
[0027] Other objects, features, and advantages of the present invention will become apparent from a consideration of the following detailed description.
Brief Summary of the Drawings
[0028] FIGURE 1 depicts a perspective view of a catheter and stent system according to an embodiment of the invention;
[0029] FIG. 2 depicts a side view, in cross section, of the system of FIG.
1;
[0030] FIGS. 3A-3C depicts cross-sectional views of the gearing assembly from the system of FIGS. 1 and 2;
[0031] FIG. 4A-4C depict cross-sectional views of a gearing assembly according to an embodiment of the invention;
[0032] FIG. 5 depicts a cross-sectional view of a gearing assembly according to an embodiment of the invention; [0033] FIG. 6 depicts a cross-sectional side view of a system according to an embodiment of the invention;
[0034] FIG. 7 depicts a cross-sectional side view of a system according to an embodiment of the invention, and
[0035] FIG. 8 depicts a cross-sectional side view of a system according to an embodiment of the invention.
Detailed Description of the Preferred Embodiment
[0036] The delivery system shown in the accompanying Figures shows a device, and associated method, for delivering stents (or any other medical device) at a variable speed. More particularly, the variable speed stent delivery system is configured for delivering self-expanding stents at speeds that increase from a relatively slow initial deployment speed to a significantly faster deployment speed. The variable speeds facilitate accurate positioning and initial impingement of the deployed portions of the stent against the inner wall of a body lumen while also improving the efficiency of the procedure by reducing the time to deploy the later portions of the stent and reducing risks of the stent being dislodged as the stent is rapidly deployed once positioned.
[0037] In general, delivery systems for self-expanding stents include a catheter assembly and a handle or control handle. A proximal end of the catheter assembly is coupled to the handle, and the catheter assembly extends outwardly from the handle. While the catheter assembly may be any useful length, the assembly in one embodiment is between about 50 cm and 200 cm in length.
[0038] The catheter assembly in one embodiment comprises coaxial inner and outer tubes. The outer tube is a tubular sheath and the inner tube is a guide tube (or shaft). The sheath has a lumen extending from a proximal end to a distal end, and a stent, such as a self-expanding stent, is mounted on the inner guide tube and positioned or housed in a compressed state within a distal area of the lumen of the sheath. As will be explained in detail with reference to the Figures, the sheath can be attached to the handle such that it can be retracted into the handle to expose or release the compressed stent during deployment. The guide tube is also secured to the handle.
[0039] The inner (guide) tube or shaft is a generally longitudinal structure having proximal and distal ends, and in one embodiment the proximal end of the shaft has a Luer or other guidewire hub attached thereto. The proximal portion of the shaft may, depending on the particular application, be made from a relatively stiff material such as stainless steel, Nitinol, or any other suitable material known to those of ordinary skill in the art. The shaft also includes a distal portion, which may be made from a co-extrusion high density polyethylene for the inner portion and polyamide for the outer portion. Other suitable materials for the distal portion are known to those of ordinary skill in the art, and include polyurethane, polyimide, polyetheretherketone, and Nitinol. These materials may be utilized as single or multi-layer structures, and may also include reinforcement wires, braid wires, coils, filaments, or the like. The two portions, distal and proximal, of the shaft can be joined together by any number of means known to those of ordinary skill in the art, including heat fusing, adhesive bonding, chemical bonding, or mechanical attachment. The proximal end may preferably give the shaft the necessary rigidity or stiffness it needs to effectively push out the stent, while the distal portion may provide the necessary combination of flexibility (to navigate tortuous vessels) and column strength (to effectively push out the stent).
[0040] The distal portion of the shaft may preferably have a distal tip attached thereto. The distal tip can be made from any number of materials known in the art including polyamide, polyurethane, polytetrafluoroethylene, and polyethylene including multi-layer or single layer structures. The distal tip may have a proximal end whose diameter is substantially the same as the outer diameter of the sheath which is immediately adjacent thereto. The distal tip often tapers to a smaller diameter from its proximal end to its distal end, wherein the distal end of the distal tip has a diameter smaller than the inner diameter of the sheath. The distal tip helps to prevent blood from entering the sheath as the apparatus is being navigated through the body vessels. In a preferred embodiment, attached to the distal portion of the shaft is a stop, which is proximal to the distal tip and the stent. The stop can be made from any number of materials known in the art, including stainless steel and/or a highly radiopaque material such as platinum, gold, tantalum, or a radiopaque filled polymer. The stop may be an integrally-formed step formed on the outer surface of the shaft, and/or can be attached to the shaft by mechanical or adhesive bonding, or by any other means known to those skilled in the art. The diameter of the stop may be large enough to make sufficient contact with the loaded stent at its end without making frϊctional contact with the inner layer of the outer sheath. The stop helps to "push" the stent out of the sheath during deployment, by preventing the stent from migrating proximally within the sheath during retraction of the sheath for stent deployment.
[0041] In one embodiment, proximal to the stop is a sleeve, which can be made from any number of materials known to those skilled in the art including plastic. The sleeve is attached to the shaft immediately proximal to the stop by any number of ways known to those skilled in the art including thermal or mechanical bonding. The sleeve acts to reinforce the stop during deployment of the stent. The sleeve is large enough to make sufficient contact with the stop in order to reinforce the stop. However, it is also preferably small enough not to interfere with the taper of the outer sheath when the inner shaft is inside the outer sheath. During deployment, the outer sheath is moved in a proximal direction relative to the stationary inner shaft. The radiopaque stop also aides in positioning the stent within the target lesion during deployment within a vessel, as is described below. [0042] A radiopaque marker can be attached to the shaft, such as at a point distal to the distal end of the loaded stent. The radiopaque marker can be made of platinum, iridium coated platinum, gold, tantalum, stainless steel, or any other suitable material known in the art. The shaft may preferably have a guidewire lumen extending along its length, where the guidewire enters through the guidewire hub and exits through its distal tip. This allows the shaft to receive a guidewire much in the same way that a balloon angioplasty catheter receives a guidewire. Such guidewires are well known in the art and help to guide catheters and other medical devices through the vasculature of the body.
[0043] Alternatively, the shaft may comprise three tubing sections
(proximal shaft, distal shaft, and distal tip). The proximal shaft may be constructed of 304 stainless steel hypo-tubing (O.D.=0.032" and wall thickness=0.0045") and be approximately 10-12 inches long. The proximal end of the proximal shaft can attached to a typical medical luer connector or "hub." Use of the stainless hypotubing will provide the necessary stiffness and column strength to support the system while the outer sheath is retracted for stent deployment. The distal shaft may be constructed of a coextruded tube consisting of an outer layer of nylon-12 (or another suitable polymer) and an inner layer of a maleated high-density polyethylene such as PLEXAR PX209, sold by the Quantum Chemical Company. PLEXAR PX209 is a maleated high- density polyethylene that chemically bonds to nylon-12 in the extrusion process. The distal shaft is designed to take advantage of the properties of nylon-12 while providing a lubricous inner lumen for tracking over a guidewire. Also, PLEXAR PX209 polymer bonds tenaciously to stainless steel in a typical heat fusing process. U.S. Pat. No. 5,538,510, issued on July 23, 1996, discloses the use of such materials in manufacturing catheters. The distal tip of the inner member may be sealed or insert molded to the distal shaft and constructed of an approximate 25D Shore hardness polyamide elastomer or equivalent. Use of nylon-12 as the outer layer of the distal shaft helps to facilitate this seal. The tip is designed to be atraumatic, which can be beneficial when working in the carotid region. Being soft and relatively sticky, the tip may be coated with a hydrophilic coating to provide better lubricity.
[0044] The sheath may be a polymeric catheter having a proximal end terminating at a Luer hub and a distal end which terminates at the proximal end of the distal tip of the shaft when the stent is in its undeployed position. The distal end of the sheath can include a radiopaque marker band, which may be disposed along the sheath outer surface. The sheath radiopaque marker band can indicate to the surgeon or other user that the sheath is fully withdrawn from the stent, indicating that the stent is fully deployed and that it is now safe to remove the delivery system from the patient's body.
[0045] In one embodiment, the distal end of the sheath includes an enlarged section, which has larger inside and outside diameters than the inside and outside diameters of the sheath proximal to the enlarged section. The enlarged section can house the pre-loaded stent, the stop, the sleeve, and the stent bed, which is the portion of the shaft over which the stent is disposed. Proximal to the sleeve, the outer sheath may taper proximally to a smaller size diameter. The tapering of the sheath allows for higher injection rates of radiopaque fluid, both before and after deployment of the stent.
[0046] In certain designs, the stent of some self-expanding delivery systems can become lodged within the sheath or catheter in which it is disposed, although such systems are safe. To overcome this issue, the sheath may preferably comprise an outer polymer (preferably polyamide) layer and an inner polymer (preferably polytetrafluroethylene) layer. Other suitable polymers for the inner and outer layers include any suitable material known to those skilled in the art including polyethylene or polyamide, respectively. Positioned between the outer and inner layers may be a wire reinforcing layer, which may be a braided wire. The braided reinforcing layer may be made from stainless steel. [0047] The outer sheath can incorporate a single outer polyamide layer from its proximal end to its distal end or can be a series of fused transitions decreasing in material durometer from the proximal end to the distal end along the outer layer of the sheath. The inclusion of transitions of varying material durometers can effectively enhance the catheter performance as it is pushed over the guidewire through the vascular anatomy. The flexibility of the delivery system from the proximal end to the distal end of the sheath can improve the manner in which the system tracks over the guidewire.
[0048] In the 3-layered sheath embodiment discussed above, the multiple layers can collectively enhance stent deployment. They can help to prevent the stent from becoming too imbedded within the sheath prior to stent deployment. The braid layer provides radial support to the inner layer creating sufficient resistance to the outward radial force of the stent within the sheath. The inner layer also provides a low coefficient of friction surface to reduce the forces required to deploy the stent. In addition to the above mentioned benefit, the braid layer offers many other advantages. It gives the sheath better pushability, i.e., the ability to transmit a force applied by the physician at a proximal location on sheath to the distal tip, which aids in navigation across tight stenotic lesions within the vascular anatomy. The braid layer also gives the sheath better resistance to elongation and necking as a result of tensile loading during sheath retraction for stent deployment. The configuration of the braid layer can be changed to change system performance. This is achieved by changing the pitch of the braid, the shape of the individual braid wires, the number of braid wires, and the braid wire diameter. Additionally, coils could be incorporated similarly to the braid layer of the sheath to minimize stent embedment and enhance system flexibility.
[0049] The outer sheath of the system may comprise three tubing sections (proximal sheath, distal sheath, and distal end). The proximal sheath may be constructed of 304 stainless steel hypo-tubing (O.D. =0.065", LD. 0.053") and be approximately 20 inches long. The proximal end of the proximal shaft can be attached to a valve that provides a seal to blood flow when closed, and allows free movement over the inner member when opened. Again, the use of stainless steel for the proximal end will give the physician the necessary stiffness and column strength to manipulate the system for deployment. The distal sheath of the outer member may be constructed of a coextruded tube of nylon- 12 over the PLEXAR PX209 polymer. The distal sheath may be heat fused to the stainless steel hypotube of the proximal sheath.
[0050] When being inserted into a patient, the sheath and the shaft may be locked together at their proximal ends by a lock mechanism such as a Tuohy Borst valve. This prevents any sliding movement between the shaft and sheath which could result in a premature deployment or partial deployment of the stent. When the stent reaches its target site and is ready for deployment, the valve is opened so that the sheath and the shaft are no longer locked together.
[0051] Note that a number of catheter assemblies (or at least distal portion configurations) and/or stents may be used to practice the invention. In other words, the invention is useful with nearly any catheter assembly that employs a retractable outer sheath. For example, the dista! portions or catheter assemblies and/or stents described in the following patents may be used with handle: U.S. Pat. No. 6,375,676 to Cox; U.S. Pat. No. 6,019,778 to Wilson et al; U.S. Pat. No. 6,613,075 to Healy et al.; U.S. Pat. No. 6,117,140 to Munsinger; U.S. Pat. No. 6,520,983 to Colgan et al.; U.S. Pat. No. 6,443,979 to Stalker et al.; and U.S. Pat No. 6,129,755 to Mathis et al.
[0052] FIGS. 1 and 2 depict a system for deploying a medical device such as a stent in a patient's body. In the particular embodiment of FIGS. 1 and 2, the system 10 includes a catheter 12 having a sheath 14 with a distal end 16 and proximal end 18. A sheath lumen 20 passes through the sheath 14 along the length of the sheath 14, The system 10 includes a stent 22 positioned within the sheath lumen 20 adjacent the sheath distal end 16. The stent 22 includes a stent distal end 24 and stent proximal end 26. The stent 22 can be self- expanding and/or balloon-expandable,
[0053] The catheter 12 includes a distal end 27 and a proximal end 29, with a handle 28 at the proximal end 29 through which the sheath 14 passes, so that the sheath distal end 16 is distal of the handle 28, and the sheath proximal end 18 is proximal of the handle 28, Note that the sheath proximal end could alternatively be positioned in the handle itself, depending on the particular application. The handle 22 includes a rotatable knob 30 which controls movement of the sheath 14 with respect to the handle 22 via a gear assembly 32, Note that other controls for sheath movement (i.e., other than or in addition to a rotatable knob) are within the scope of the invention.
[0054] The catheter 12 includes catheter shaft in the form of an inner longitudinal structure 34 extending within the sheath lumen 20 and extending from the handle 28 to the stent 22. The inner longitudinal structure 34 includes a structure distal portion 36 around which the stent 22 is mounted. The inner longitudinal structure 34 helps to hold the stent 22 in a desired position within the catheter 12. In the particular embodiment of FIGS. 1 and 2, the inner longitudinal structure 34 includes a distal end 38 as well as a distal-facing surface 40 that engages against the proximal end 26 of the stent 22, preventing the stent 22 from being withdrawn proximally when the sheath 14 is retracted proximal Iy. Alternatively, the stent could be positioned just distally of the inner longitudinal structure distal end, with the inner longitudinal structure distal end forming a distal-facing surface that engages the stent proximal end to prevent proximal retraction of the stent. For a balloon-expandable stent, the stent could be crimped onto the inner longitudinal structure distal portion, with the crimping serving to hold the stent onto the inner longitudinal structure. Other methods of preventing proximal and other unwanted movement of the stent could be used. [0055] The handle 28 includes a handle main body 42 and handle proximal portion 44 through which the sheath 14 passes. The handle proximal portion 44 includes finger grip surfaces 46 on opposing sides thereof. The handle proximal portion 44 also includes a proximal opening 48 out of which the sheath 14 exits. A luer access port 50 enters through a side area of the handle proximal portion 44, with the luer access port 50 providing access to an inner lumen 52 of the inner longitudinal structure 30 via a connecting structure 54. The luer access port 50 and inner lumen 52 can be used to access the treatment area, to inject or remove fluids such as saline, etc. In additional to providing a connection between the luer access port 50 and inner lumen 52, the connecting structure 54 also serves to hold the inner longitudinal structure 30 in place with respect to the handle 28.
[0056] The sheath 14 includes a slit 56 which permits the sheath 14, as it is being retracted proximally, to accommodate internal structures of the handle 28, including the connecting structure 54 between the handle 28 and inner longitudinal structure 30. The slit 56 may be pre-formed along much and/or al! of the length of the sheath 14, and/or may be formed and/or lengthened during proximal retraction of the sheath 14. For example, a cutting blade 57 can be positioned distally of the connecting structure 54, or even on a distal side of the connecting structure 54 itself, with the cutting blade 57 engaging against the sheath 14 to create and/or lengthen the slit 56 as the sheath 14 is retracted proximally. The slit 56 thus permits the sheath 14 to be retracted around and past the connecting structure 54.
[0057] The handle proximal portion 44 is detachably connected to the handle main body 42 to permit a user to grasp the handle proximal portion 44 and remove it in a proximal direction from the handle main body 42. The handle proximal portion 44 can be configured so that, when outside pressure is applied thereto (such as the gripping pressure applied by a user grasping the handle proximal portion 44), the handle proximal portion 44 engages against the sheath 14 passing therethrough so that the sheath 14 is fixedly held within the handle proximal portion 44. For example, the opposing finger grip surfaces 46 could include or be attached to flexible and/or otherwise movable portions that engage inwardly against the sheath 14 in response to outside pressure being applied to the finger grip surfaces 46. With such a configuration, the user can grasp the handle proximal portion 44, thereby fixing the sheath 14 within the handle proximal portion 44, and then withdraw the handle proximal portion 44 and sheath 14 proximal Iy from the handle main body 42 in a single movement. The handle proximal portion 44 could also be configured so that the handle proximal portion 44 automatically engages against the sheath 14 when the snap- like connection is opened and/or when the handle proximal portion 44 is otherwise moved proximally from the handle main body 42.
[0058] The handle proximal portion 44 can be detachably connected to the handle main body 42 via a snap-like connection, so that the user must pull on the handle proximal portion 44 with sufficient force to overcome the initial resistance of the snap-like connection before the handle proximal portion 44 will move relative to the handle main body 42. Once the initial resistance of the snap-like connection is overcome, the handle proximal portion 44 will slide relatively easily away from the handle main body 42. With a gripping pressure applied to sheath 14 from the handle proximal portion 44 via the finger grip portions 46, the sheath 14 can be held securely within the handle proximal portion 44. Because the inner longitudinal structure 34 and stent 22 are secured to the handle main body 44, pulling the handle proximal portion 44 away from the handle main body 42 causes corresponding retraction of the sheath distal end 16 from the stent 22 and inner longitudinal structure distal portion 36.
[0059] FIGS. 3A-3C depict more detailed views of the rotatable knob 30 and gearing assembly 32 that can be used to cause and control proximal retraction of the sheath 14. The rotatable knob 30 is configured to rotate about an axis 59, and includes a circular gear ring 58 on a side thereof and having an inner geared surface 60. Note that the geared surface could alternatively be on the outer surface of the gear ring. The inner geared surface 60 drives first and second drive gears, which in the embodiment of FIGS. 3A-3C are an upper drive gear 62 and a lower drive gear 64. The upper and lower drive gears 62, 64 are coupled to first and second drive wheels, which in the embodiment depicted are upper and lower drive wheels 66, 68. The upper and lower drive wheels 66, 68 engage against opposite sides of the sheath.
[0060] As depicted in FIG. 3B, the upper and lower drive wheels 66, 68 rotate in opposite directions when driving the sheath 14 in a proximal (or distal) direction. In the side view of FIG. 3B, where the proximal direction is to the right and the distal direction is to the left, the upper drive wheel 66 rotates counterclockwise to drive the sheath proximally, while the lower drive wheel 68 rotates clockwise. However, as depicted in FIG. 3C, the upper and lower drive gears 62, 64 will both rotate in the same direction in response to rotation of the rotatable knob 30. In the embodiment of FIG. 3C, which also has proximal to right and distal to left, clockwise rotation of the rotatable knob 30 causes clockwise rotation of both the upper and lower drive gears 62, 64. Because the lower drive gear 64 is rotating in the same direction (i.e., clockwise) that is desired for the lower drive wheel 68, the lower drive gear can be connected directly to the lower drive gear. However, the upper drive gear 62 is rotating in the opposite direction desired for the upper drive wheel 66. To transfer the clockwise rotation of the upper drive gear 62 to the desired counterclockwise rotation of the upper drive wheel, the upper drive gear is connected to the upper drive wheel 68 via an intermediary gear 70.
[0061] Another approach to transferring the rotation of the rotatable knob 30 to the proper rotations of the drive wheels is depicted in FIGS. 4A-4C, wherein the circular gear ring 58 has an inner geared surface 60 as well as an outer geared surface 61. The outer geared surface 61 engages against the upper drive gear 62, while the inner geared surface 60 engages against the lower drive gear 64. As depicted in FIG. 4C, the upper and lower drive gears 62, 64 will now rotate in opposite directions to each other, namely counterclockwise for the upper drive gear 62 and clockwise for the lower drive gear 64. Because each of the drive gears 62, 64 is rotating in the same direction that is desired for the corresponding drive wheel 66, 68, respectively, each of the drive gears 62, 64 can be connected directly to the corresponding drive wheels 66, 68.
[0062] In another embodiment of the invention, depicted in FIG. 5, only one drive wheel is used, which in the particular embodiment is the lower drive wheel 68. An opposing wheel 65, which in the embodiment is an upper wheel, can still be present, but it is not a drive wheel because it is not connected, via gears or otherwise, to the rotatable knob 30. Instead, the opposing wheel 65 can freely spin in response to movement of the sheath 14, The opposing wheel 65 serves to hold the sheath 14 against the lower drive wheel 64, while the lower drive wheel 64 provides the rotating force that moves the sheath 14 proximally within the handle. Note that the upper wheel could be the drive wheel, with the lower wheel serving as the opposing non-drive wheel.
[0063] In the embodiment of FIGS. 1-3, the rotatable knob 30 provides for precise albeit relatively slow retraction of the sheath 14, while the handle proximal portion 44 provides, when pulled proximally away from the handle main body 42, rapid retraction of the sheath 14. The handle proximal portion 44 can also provide a back-up method for retracting the sheath 14 in case of any problem with the rotatable knob 30 and/or gear assembly 32 and/or drive wheels 66, 68.
[0064] To deploy the stent, a user can advance the catheter distal end (including the sheath distal end and stent) to a desired treatment location. The user can use the rotatable knob for the initial retraction of the sheath, which may include the initial deployment of the distal portion of the stent. Once initial deployment is achieved, e.g., once the distal portion of the stent is secured to the artery or other body lumen, the user can pull the handle proximal portion away from the handle main body to rapidly retract the sheath to complete the release of the remainder of the stent. With the sheath retracted and the stent deployed, the user can then withdraw the catheter entirely from the patient's body, leaving the stent deployed at the desired treatment site.
[0065] FIG. 6 depicts depict a further embodiment of a system 80 including a catheter 82 and stent 84. The catheter 82 includes a sheath 86, inner longitudinal structure 88, and handle 90. The handle 90 includes a handle main body 92 and a handle proximal portion 94 rotatably connected to the handle main body 92.
[0066] The handle 90 includes a generally tubular structure 96 rotatably positioned within the handle 90. The generally tubular structure 96 is connected, either directly or via gears, to the handle proximal portion 94, so that rotation of the handle proximal portion 94 causes a corresponding rotation of the generally tubular structure 96. The generally tubular structure 96 includes a tubular inner surface 98 bearing a variable helical thread pattern 100 thereon.
[0067] The sheath 86 has a proximal portion 102 connected to a block
104 or similar structure having an outer surface 106 configured to engage against the helical thread pattern 100 on the tubular inner surface 98. In the embodiment of FIGS. 6 and 7, the block outer surface 106 includes opposing outwardly-extending tabs 108 that each rest within one of the two spiral slots 110 formed by the double helical thread pattern 100. The block 104 is prevented from rotating with respect to the handle main body 92, which could be accomplished by various devices and/or methods known in the art. For example, the block 104 might have a tab that engages against a part of the elongate longitudinal structure 88 to prevent rotation of the block 104. When the generally tubular structure 96 is rotated, the gear-like interaction between the block outer surface 106 and tubular inner surface 98 draws the block 104 and attached sheath 86 in a desired direction.
[0068] In the embodiment depicted in FIG. 6, the helical thread pattern
100 is a double helical thread pattern formed by two spiral slots 1 10. Other thread patterns are also within the scope of the invention, as are thread patterns formed by slots or other partial or complete openings in the tubular inner surface and/or by raised structures (e.g., ridges, etc.) on the tubular inner surface.
[0069] The catheter 82 is configured so that rotation of the handle proximal portion 94 will cause the sheath 86 to be withdrawn at an initially slower rate of withdrawal per rotation of the handle proximal portion 94, but with the speed of sheath withdrawal increasing with respect to further rotations of the handle proximal portion 94 as the sheath 86 moves proximally. To achieve this difference in speed of the sheath withdrawal (with respect to rotation of the handle proximal portion 94), the angle of attack (or pitch) of the double helical thread pattern 100 is relatively small in the distal portion 112 of the generally tubular structure 96, but increases in the proximal portion 114 of the generally tubular structure 96. This increase in the angle of attack or pitch of the helical thread pattern 100 causes the block 104 (and hence the sheath 86) to be withdrawn with greater speed (for the same rotational movement of the generally tubular structure 96) as the block 104 moves proximally within the generally tubular structure 96. In the particular embodiment depicted in FIG. 6, it will take approximately three (3) complete rotations of the generally tubular structure 96 for the block 104 to be withdrawn from the distal end 116 of the distal portion 112 to the dividing point 118 between the distal portion 112 and proximal portion 114 of the generally tubular structure 96. Once the block 104 reaches the dividing point 118, approximately three (3) more complete turns will move the block 104 a much larger distance, namely to the proximal end 120 of the generally tubular structure 96. The increase in the angle of attack of the helical thread pattern 100 can be relatively constant, thereby providing a constant increase in the speed of sheath withdrawal. The helical thread pattern may have one or more relatively sudden increases in the angle of attack, thereby providing one or more relatively sudden and uneven increase(s) in the speed of sheath withdrawal. The thread pattern may increase up to a constant level as well. [0070] Other variations are also within the scope of the invention. For example, the positioning of the helical thread pattern and interacting tabs could be reversed, so that the helical thread pattern is on the drive block and the tabs or similar structures are on the inner surface of the generally tubular structure. Such an embodiment is shown in FIG. 7, where the drive block 104 has an outer surface 122 bearing a helical thread pattern 124 thereon, either as a raised structure or as a partial or complete opening in or on the drive block outer surface 122. The generally tubular structure 96 includes an inner surface 98 having one or more inwardly extending tabs 126 or other structures (such as slots, etc.) configured to engage against or otherwise interact with the helical thread pattern 124 on the drive block outer surface 122. Note that the helical thread pattern 124 angle of attack increases from the drive block proximal end 127 to the drive block distal end 129, which causes the speed of sheath withdrawal to increase as the drive block 104 is pulled proximally with respect to the generally tubular structure 96.
[0071] FIG. 8 depicts a further embodiment, wherein a system 130 includes a catheter 132 and stent 134. The catheter 132 includes a motor 136 in the catheter handle 138. The motor 136 is controlled by a control button 137, and drives a gear 139 or other rotator that drives the rotation of a generally tubular structure 140 having a geared inner surface 142 in the form of a double helical thread pattern 144. The sheath 146 is secured to a block 148 having an outer surface 150 that engages the geared inner surface 142 of the generally tubular structure 140. As with the embodiment of FIG. 6, the angle of attack (or pitch) of the double helical thread pattern 144 changes along the length of the generally tubular structure 96. In the particular embodiment of FIG. 8, the angle of attack increases from the distal end 152 to the proximal end 154 of the generally tubular structure 140. Accordingly, the speed of withdrawal of the sheath 146 from the stent 134 and inner longitudinal structure 156 will increase for each rotation of the generally tubular structure 140 as the sheath 146 is withdrawn. The catheter 132 includes a proximal end 158 with a Iuer lock 160 thereon.
[0072] In a device such as that depicted in FIG. 8, if the motor 136 is a generally one-speed device (i.e., that rotates at a generally constant speed when activated), the generally constant speed of the motor 136 combined with the changing double helical thread pattern 144 will cause an increasingly fast withdrawal of the sheath 146 as the sheath 16 is withdrawn. The motor 136 and/or other elements of the catheter 132 could be configured to provide a variable speed of rotation to the generally tubular structure 140, either through gears, electric controls, or other methods known in the art for varying motor speed and/or rotation of motor-driven elements. This configuration of a variable speed of rotation for the motor and/or generally structure could be combined with, or in lieu of, a changing geared inner surface (e.g., double helical thread pattern) of the generally tubular structure 140.
[0073] Note that various elements of the embodiments depicted and described could be combined. For example, the motor 136 and/or variable helical thread pattern 144 of FIG. 8 could be combined with the detachable proximal handle portion 44 and/or sheath-grabbing finger grips 46 of FIGS. 1 and 2, and/or the catheter assembly FIG. 7.
[0074] While the invention has been described with reference to particular embodiments, it will be understood that various changes and additional variations may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention or the inventive concept thereof. For example, while the invention is specifically discussed in application with deployment of stents, it has applicability in other areas where it is desired to withdraw a sheath or similar device using variable speeds of withdrawal. In addition, many modifications may be made to adapt a particular situation or device to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed herein, but that the invention will include all embodiments falling within the scope of the appended claims.