Medical appliance delivery apparatus and method of use

[0001] This application is a continuation of U.S. application Ser. No. 10/281,429, filed Oct. 26, 2002, now abandoned which is hereby incorporated herein in its entirety by reference.

[0002] The present invention relates generally to medical devices directed to the prevention of nonvascular vessel or passageway occlusion, and more particularly to stent deployment apparatuses and methods for utilizing these devices in the treatment of both benign and malignant conditions.

[0003] Stents are devices that are inserted into a vessel or passage to keep the lumen open and prevent closure due to a stricture, external compression, or internal obstruction. In particular, stents are commonly used to keep blood vessels open in the coronary arteries and they are frequently inserted into the ureters to maintain drainage from the kidneys, the bile duct for pancreatic cancer or cholangiocarcinoma or the esophagus for strictures or cancer. Nonvascular stenting involves a range of anatomical lumens and various therapeutic approaches, however, accuracy of installation is universally important.

[0004] In order to serve its desired function, the stent must be delivered precisely and oriented correctly. In order to facilitate the delivery of stents, medical device companies began to design deployment apparatuses that allow physicians to deploy stents more precisely. Unfortunately, guidance of the stent has substantially remained a function of physician skill resulting from substantial practice. This fact has become particularly evident with the advent of radially expanding stents. If after full deployment of the stent, the physician discovers the stent has been implanted incorrectly, there is no conventional way of correcting the error short of removing the stent. In particular, as a rule of thumb, once the exterior catheter, of conventional delivery devices, has been retracted beyond 60%, it generally cannot be realigned with respect to the stent. As a result, physicians must be sure of their stent placement prior to deploying the stent beyond the 60% point. We will refer to this 60% point throughout the application as the critical deployment point.

[0005] Conventional stent delivery devices, however, do not have any safety mechanism to prevent excessive deployment of a misaligned stent. In fact, conventional delivery devices require the physician to estimate extent of deployment, which results in either overly conservative or excessive deployment—both of which leads to stent misplacement.

[0006] An additional limitation of conventional stent delivery devices is the distal tip of conventional stent delivery devices are not adequately designed to (1) facilitate the clearance of obstructed lumen, or (2) facilitate the removal of the delivery device once the stent is radially expanded. In particular, most distal tips are not configured to comfortably guide the delivery device through a diseased or occluded lumen so that the stent can be delivered in the most beneficial location. Moreover, once the stent is radially expanded conventional designs rely exclusively on dimensional mismatching to ensure proper removal of the delivery device. In the event the stent does not adequately expand to preset dimensions, a conventional delivery device would be stuck in the patient until some invasive procedure is performed to remove it and the defective stent.

[0007] Therefore, there remains an existing need for a stent deployment apparatuses that has a safety mechanism to prevent excessive deployment of a misaligned stent. Preferably it would be desirable if the safety mechanism had a physical and/or audible indication means to inform the physician when she has reached maximum reversible deployment. As an additional safety feature, there is an existing need for a distal tip designed to allow for the removal of the deployment apparatus even if the stent does not radially expand to its preset expansion diameter. An existing need also exists for a stent deployment apparatus that has a distal tip adequately configured to navigate through diseased and/or occluded lumens so that the stent can be delivered to this target area.

[0008] There also remains an existing need for a stent deployment apparatus that increases physician control during stent deployment. Moreover, there exists a need for a stent deployment apparatus that allows for the insertion of an optical scope to facilitate stent delivery.

[0009] It is a principal objective of an exemplary stent deployment apparatus in accordance with the present invention to provide a device that can facilitate the precise delivery of stents in a safe and repeatable fashion. In the furtherance of this and other objectives, a preferred deployment apparatus allows the physician to concentrate on correct placement without having to estimate extent of deployment. In particular, in a preferred embodiment, the present deployment apparatus has a physical safety mechanism that limits deployment to the critical deployment point (i.e., ˜60%). The critical deployment point may range form 5% to 95% but is preferably about 60%. At this point, if the physician is satisfied with placement, she can engage the safety means to what we refer to as the Proceed Orientation (PO) and fully deploy the stent. It is preferred that when the safety mechanism is engaged to the PO, a physical twist and a possible audible indicator sounds to inform the physician that if she deploys the stent any further, she can no longer retract the stent beyond this point. Though the present stent and delivery system eliminates the need for repositioning, such safety features are still preferable. In a preferred embodiment, the slight audible indication is the sound of a tab or stop snapping to allow free deployment of the stent.

[0010] An additional objective of a preferred embodiment of the present invention is to provide a stent deployment apparatus where the handle portion is held and the outer tubular member of the device is retracted.

[0011] Yet another objective in accordance with the present invention is to provide a deployment apparatus having a distal tip designed to facilitate the clearance of obstructed lumen. In the furtherance of this and other objectives, the exemplary distal tips are configured to comfortably guide the deployment apparatus through a diseased or occluded lumen so that the stent can be delivered in the most beneficial location.

[0012] Still another objective of a preferred deployment apparatus in accordance with the present invention is to provide a distal tip that facilitates the removal of the deployment apparatus once the stent is radially expanded. In the furtherance of this and other objectives, the distal tip is designed to clear the stent during removal, in the event the stent does not adequately expand to preset dimensions. In a preferred embodiment, removal is facilitated by providing a distal tip that has a substantially bidirectional conic shape. This allows for the removal of the present deployment apparatus, while conventional deployment apparatuses would be stuck in the patient until some invasive procedure was performed to remove it and the defective stent. This results from the fact that conventional deployment apparatus designs rely exclusively on dimensional mismatching between the distal tip and the radially expanded stent to ensure proper removal of the deployment apparatus. As a function of the design of the present invention, the compressed stent is adequately retained in place and does not prematurely creep up the proximally facing conic end of the distal tip and prematurely deploy.

[0013] An additional objective in accordance with an exemplary embodiment of the present invention is to provide a stent deployment apparatus that allows for the insertion of an optical scope to facilitate stent delivery. In the furtherance of this and other objectives, the device is capable of letting a flexible optical scope of about 5-6 mm diameter be coupled along the exterior of the outer tubular member thereof. Alternatively, it is envisioned that an ultra thin optical scope may pass along side the guidewire through the internal diameter of the internal tubular member of the device.

[0014] In addition to the above objectives, an exemplary stent deployment apparatus preferably has one or more of the following characteristics: (1) applicable for various interventional applications such as addressing stenosis; (2) biocompatible; (3) compliant with radially expanding stents; (4) capable of distal or proximal stent release; (5) smooth and clean outer surface; (6) length of the device variable according to the insertion procedure to be employed; (7) outer dimension as small as possible (depends on the diameter of crimped stent); (8) dimensions of the device must offer enough space for the crimped stent; (9) radiopaque markers, preferably on the inner tubular member, to indicate proximal and distal ends of the stent; (10) sufficient flexibility to adapt to luminal curvatures without loss of ability to push or pull; (11) low friction between the inner tubular member and outer tubular member; (12) sufficient resistance to kinking; (13) good deployment, ability to reposition partially deployed stent; (14) added with a scale to observe the stent position during the insertion procedure; (15) insertion procedure should require low force; or (16) sufficiently economical to manufacture so as to make the deployment apparatus disposable.

[0015] Further objectives, features and advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0026] A general problem in the diagnosis and therapy of both vascular and nonvascular anomalies is the fact that the instruments must be inserted into or pass the area of maximum diameter of about 15 mm. As a result, the inserted instruments take away a very large portion of the free lumen and may increase the danger of injury to the patient.

[0027] Therefore, it is the primary objective of the present invention to provide an instrument, which con be inserted gently, ensures a good utilization of the available space and makes it possible to carry out active therapeutic measures, wherein the instrument is to be particularly suitable for the introduction and placement of stents.

[0028] A preferred embodiment of the present deployment apparatus comprises inner and outer tubular members interactively coupled with each other in a manner that one can move rotationally and proximally or distally with respect to the other. The tubular members are preferably nonpyrogenic. In order to deliver the stent, the deployment apparatus comprises a distal tip and a stent retaining hub, between which the stent is placed. The distal tip and the stent-retaining hub are both functionally coupled with the inner tubular member. The inner tubular member terminates with a luer or in a preferred embodiment, a proximal handle similar to the outer handle hub. The luer is preferably a female threaded luer, but alternative termini are within the skill of the stent deployment device engineer. In fact, a suitable alternative would be a handle having similar internal diameter characteristics as the luer while providing greater surface area for manipulating the deployment apparatus. As stated above, a preferred alternative would be a proximal handle that is similar in geometrical shape but preferably smaller than the outer handle hub, to facilitate movement, however the proximal handle may be of any size functionally acceptable by the user. The deployment apparatus is preferably sterilized by a validated sterilization cycle EtO. Moreover, the device is capable of resterilization (validated cycle) with no degradation of performance. However, it is preferable to provide a disposable device.

[0029] The deployment apparatus is preferably about 100 cm±2 cm total. The inner diameter of the inner tubular member is approximately about 1 mm and the outer diameter of the outer tubular member is preferably about 5 to 6 mm in diameter. For purposes of this discussion, the usable length of the inner tubular member shall be from the inner tubular member distal hub/handle end to the distal tip. The usable length of the outer tubular member shall be from the distal hub/handle end of the outer tubular member to the distal tip. The overall length of the device shall be from the distal hub/handle end of the outer tubular member to the distal tip of the inner tubular member when assembled and not deployed. There will also be preferably three radiopaque (platinum iridium) markers for marking the stent, the stent deployment distance, and depth. The outer tubular member is preferably manufactured of stiffer synthetic material. In a preferred embodiment, the length of the outer tubular member is preferably shorter than that of the inner tubular member.

[0030] However, these dimensions may differ as a function of the stent diameter and/or if an optical scope is employed to facilitate stent delivery. The outer tubular member may be configured to allow for the coupling of an optical scope along the outer diameter thereof. Alternatively, the inner diameter of the inner tubular member may be enlarged sufficiently to accommodate the optical scope and additionally the increased crimped stent diameter. However, it is expected, though not required, that the smallest diameter that allows for example a bronchoscope to pass will be employed in this alternative embodiment. It should be understood that through hindsight, after exposure to the present specification, one of ordinary skill would be able to adapt the current device to receive an ultra thin optical scope to the internal diameter of the device without undo experimentation and without departing from the spirit of the present objectives.

[0031] An exemplary deployment apparatus in accordance with the present invention is durable while affording adequate flexibility to navigate through anatomical lumens without kinking. To this end, it is preferable that the deployment apparatus is formed of biocompatible synthetics and in a preferred embodiment reinforced with metal structure. This should allow for deployment within an accuracy of about ±3 mm. Moreover, the stent is preferably released with a force lower than 30 Newtons at 37° C. though the force and deployment temperatures may be modified to suit the needs of specific anatomical conditions.

[0032] The inner tubular member is composed of a thin elastic synthetic material, such as polyurethane or Teflon®. At its proximal end, the inner tubular member has a standard adaptor or connector. At its distal end, the inner tubular member is equipped with a tip specific for various anatomical lumens.

[0033] The inner tubular member and the outer tubular member can be displaced relative to each other in longitudinal direction as well as in a radial direction. The deployment apparatus in accordance with the present invention can be used most advantageously for the placement of stents. Such stents are available in various embodiments of metal and/or synthetic material. They usually are composed of a fabric of metal wires, which expand by themselves as a result of their natural tension. Stents of a so-called shape memory alloy are also known. These stents have a small radial diameter at a low temperature, while they expand radially when exceeding an upper threshold temperature, so that they can keep a stenosis open in this manner. It is particularly advantageous to use stents of an alloy of nickel and titanium, the so-called nitinol.

[0034] An exemplary deployment apparatus according to the present invention can be used for the placement of various stents, whether they are self-expanding stents or stents, which require an activation. For this purpose, the stent is placed in the free space between the outer tubular member and the inner tubular member. Positioning of the stent in the deployment apparatus can be carried out in the area between the tip and the stent retaining hub at the distal end of the inner tubular member. Alternatively, in its insertion position, fasteners or other suitable retaining elements may hold the stent.

[0035] In relevant embodiments, when the stent is inserted and after the stenosis has been passed, the outer tubular member is retracted, so that the stent is released. Alternatively, the distal end of the outer tubular member may be placed about the stenosis so that the inner tubular member may be extended so that the stent is placed in direct contact with the desired location prior to expansion. A self-expanding stent then by itself assumes the expanded position. This eliminates the need for post expansion positioning techniques. With an alternative embodiment of the device, the device has fasteners that retain contact with a portion of the stent in the event that the stent needs to be retracted or repositioned. A stent suitable for such procedures would be one in accordance with the disclosure in co-pending U.S. patent application Ser. No. 10/190,770, which is incorporated herein in its entirety by this reference.

[0036] The following reference numbers and corresponding stent placement and deployment device components are used when describing the device in relation to the figures:

[0037]

10	Stent Delivery & Deployment Device
12	Guidewire
14	Proximal Handle/Female Threaded Luer
16	Hypotube
18	Safety Mechanism
20	Stop
22	Female Locking Member on the Stop
24	Tab of the Stop
30	Inner Tubular Member
32	Inner Diameter of Inner Tube
40	Handle
42	Cavity in Proximal Portion of Handle
44	Base of Handle Cavity
46	Male Locking Member
48	Inner Handle Hub
49	Outer Handle Hub
50	Outer Tubular Member
52	Outer Diameter of Outer Tubular Member
54	Distal Region of Outer Tubular Member
56	Inner Diameter of Outer Tubular Member
60	Distal Tip
62	First End of the Tip
64	Medial Region of the Tip
66	Second End of the Tip
68	Axial Passage
70	Retaining Hub
72	Distal Region of Retaining Hub
74	Proximal Hub of Retaining Hub
76	Pusher
80	Proximal Marker
82	Medial Marker
84	Distal Marker
100	Optical Scope

[0038] The figures show an exemplary placement and deployment device 10 in accordance with the present invention. Referring in particular to FIGS. 1-2, the present invention provides a stent deployment apparatus 10 that includes an outer tubular member 50 and an inner tubular member 30, wherein the outer tubular member 50 and the inner tubular member 30 can be displaced relative to each other. At the proximal end of an exemplary device 10 is a threaded female luer 14, coupled with a portion of the inner tubular member 30 and preferably a portion of a hypotube 16. As stated earlier, a suitable alternative terminus may be employed as long as it provides the minimum benefits provided by a luer. The hypotube 16 is disposed about the inner tube 30 and extends from a location adjacent to the luer 14 through a portion of the handle 40 of the deployment apparatus 10. In an alternative embodiment, the hypotube 16 terminates within the luer 14. A safety mechanism 18 is provided that is formed in part by the complementary fitting of a portion of the handle 40 and a stop 20 coupled with the hypotube 16 between the luer 14 and the handle 40. The stop 20 is preferably molded onto the hypotube 16, the molding process resulting in a tab 24 formed on the stop 20 that is subsequently broken when the physician desires to place the deployment apparatus 10 in the proceed orientation. In an exemplary embodiment, when the tab 24 is broken and the deployment apparatus 10 is placed in the proceed orientation; the stop 20 may potentially rotate freely about the hypotube 16. It should be kept in mind that the stop 20 may take a variety of shapes, including but not limited to, rectangular, round, conical etc. In a preferred embodiment, the stop 20 is conical with a tapered effect to facilitate entrance and removal from the base handle cavity 44.

[0039] As illustrated in FIGS. 3A-3D, a preferred stop 20 includes female locking members 22 comprising channels formed along the exterior thereof that are complementary to the male locking members 46 formed on the interior cavity 42 along the proximal region of the handle 40. The cavity 42 of the handle 40 is designed to receive the stop 20 and prevent further deployment. As a result, the stop 20 is molded at a distance along the hypotube 16 such that the distance between the distal end of the stop and the base 44 of the complementary cavity 42 of the handle 40 roughly corresponds to the critical deployment point. It should be noted that the female locking members 22 and male locking members 46 of the safety mechanism 18 might be reversed so that the female locking members 22 and male locking members 46 are on the handle 40 and the stop 20, respectively. Additionally, alternative safety mechanisms may be employed to ensure accurate deployment beyond the critical deployment point.

[0040] The handle 40 is preferably molded to a portion of the outer tubular member 50, which extends from the handle 40 to the distal tip 60 of the device 10. The outer tubular member 50 is disposed about the inner tubular member 30. In an exemplary embodiment, the outer tubular member 50 is clear so that the inner tubular member 50 is visible there through. Moreover, markers 80-84 preferably formed on portions of the inner tubular member 30 are also visible through the outer tubular member 50.

[0041] Referring now to FIGS. 4A-4B, in the distal region 54 of the device 10, there is a stent placement hub 70, which holds the stent (not shown) during the placement procedure. In a preferred embodiment, the stent placement hub 70 comprises two double conical shaped elements, one disposed at each end of the stent and coupled with the inner tubular member 30. In an exemplary form, the distal most double conical shaped element is the distal tip of the device 60. In alternative embodiments, the stent placement hub may also comprise proximal 72 and distal 74 stops between which the stent rests in its crimped state. Moreover, the proximal end of the stent may also be restrained by conventional coupling methods (not shown) to facilitate retrieval if necessary. By way of example, which is in no way to be construed as limiting, a stent having suture disposed about its proximal end may be retained by the stent retaining hub 70 that has releasable finger-like members engaging the suture.

[0042] The device is configured such that an optional guidewire 12 may be passed through the internal diameter 32 of the device through the luer 14 at the proximal end, the distal tip 60 at the distal end and the inner tubular member 30 there between. In an alternative embodiment, the internal diameter 32 of the device 10 is sufficient to receive an optical scope (not shown) there through.

[0043] Referring to the functional aspects of the device 10, there is shown in FIG. 1 a deployment apparatus 10 that includes an elongate and flexible outer tubular member 50 constructed of at least one biocompatible thermoplastic elastomer, e.g. such as polyurethane and nylon, typically with an outside diameter 52 in the range of about between 6-9 mm. A central lumen 56 runs the length of the outer tubular member 50. A distal region 54 of the outer tubular member 50 surrounds the stent to be placed (not shown), and maintains the stent in a crimped delivery configuration, against an elastic restoring force of the stent. The stent, when in a normal unrestrained configuration, generally has a diameter (for example, 10-20 mm) substantially larger than the interior diameter 32 of the inner tubular member 30. Typically the expanded stent is larger in diameter than the body lumen in which the stent is fixed, and the restoring force tends to maintain the stent against the tissue wall.

[0044] Outer tubular member 50 is mounted at its proximal end to a handle 40. Outer tubular member 50 can be pushed and pulled relative to inner tubular 30 by hand manipulation of the handle 40 at the proximal end of the outer tubular member 50 and holding the proximal end of the handle 14.

[0045] A guidewire 12 is preferably disposed within the interior lumen 32 of an elongate and flexible inner tubular member 30, which can be constructed of materials similar to those employed to form the outer tubular member 50. However, it is preferable that inner tubular member 30 is formed from a more durable material. A distal tip 60 is coupled with inner tubular member 30 about the distal end thereof. Also attached to the inner tubular member 30 are a proximal marker 80, at least one medial marker 82 and a distal marker 84. The markers are constructed of a radiopaque material, e.g. platinum iridium, and surround the inner tubular member 30. Markers 80, 82 and 84 are axially spaced apart to mark the length of the stent and to mark the critical deployment distance for that stent length. The markers identify a stent-retaining hub 70 of the inner tubular member 30, more particularly the distal region of the inner tubular member 30 is surrounded by stent 12. The markers may also be of varying sizes and shapes to distinguish distance between distal and proximal regions. Markers 80 and 84 may have outer diameters slightly smaller than the interior diameter of outer tubular member 50. The outer tubular member 50 thus functions as a carrier for the stent, with inner tubular member 30 providing a retaining means for radially compressing the stent and maintaining the stent along the stent retaining hub 50, so long as the outer tubular member 50 surrounds the stent.

[0046] In an alternative embodiment, items 72 and 74 are marker bands (not retaining hubs) formed on the outer tubular member 50. These marker bands visually mark the ends of the stent and thus will be over the step area of the tip and the pusher 76. All the marker bands—including 80, 82 and 84 are preferably either Platinum Iridium or Stainless Steel. Moreover, the marker bands of 80, 82, and 84 will be depth marks and will be spaced in preferably 1 cm intervals. These depth marks are preferably formed on the inner tubular member 30 and are a visual aid for the physician to assist with determining the depth at which the stent has been advanced.

[0047] Inner tubular member 30, along its entire length, has an interior lumen 56 open to both the proximal and distal ends of the inner tubular member 30. An axial passage 68 through distal tip 60 continues lumen 32 to allow the guidewire 12 to pass from the luer 14 through the distal tip 60.

[0048] Handle 40 and outer tubular member 50 are movable relative to inner tubular member 30. More particularly, the handle 40 is moved proximally relative to the stent-retaining hub 70, facilitating the movement of outer tubular member 50 relative to inner tubular member 30 so as to provide a means for controllably withdrawing the outer tubular member 50, relative to the inner tubular member 30, resulting in the release of the stent for radial self-expansion.

[0049] When the device 10 is used to position the stent, the initial step is to position guidewire 12 within the anatomy of a patient. This can be accomplished with a guide cannula (not illustrated), leaving guidewire 12 in place, with the exchange portion of the guidewire extended proximally beyond the point of entry into the anatomy of the patient. Deployment apparatus 10 is then advanced over the guidewire 12 at the exchange portion, with the guidewire 12 being received into passage 68 of distal tip 60. As device 10 is inserted into the body, the proximal portion of guidewire 12 travels proximally (relative to the device) to the proximal end of guidewire lumen 32.

[0050] Once device 10 is positioned, the physician maintains a guidewire 12 and inner tubular member 30 substantially fixed with one hand, while moving handle 40 in the proximal direction with the other hand, thus to move outer tubular member 50 proximally relative to inner tubular member 30. As the outer tubular member 50 is retracted, the stent remains substantially fixed relative to inner tubular member 30, and thus radially self-expands. As the handle 40 and correspondingly the outer tubular member 50 is retracted, the handle 40 encounters the safety mechanism 18 for the critical deployment point. The inner tubular member 30, via the handle 14, may have to be rotated to align and insert the stop 20 into the handle 40. When fully inserted, further deployment cannot occur without twisting and snapping the tab 24 portion of the stop 20. Continued retraction of the outer tubular member 50 results in complete deployment of the stent.

[0051] After deployment, the stent ideally radially self-expands to a diameter greater than the diameter of outer tubular member 50. Accordingly, device 10 can be withdrawn proximally through the stent. However, in the event that the stent does not radially expand fully, distal tip 60 is configured to facilitate removal of deployment apparatus 10 through the lumen of the stent.

[0052] Guidewire 12 can be withdrawn as well. The guidewire 12 emerges from the proximal end of the luer 14. However, should the medical procedure involve further treatment, e.g., placement of a further stent, the deployment apparatus 10 can be removed without removing the guidewire 12. Device 10 is removed by progressively pulling the device away from the guidewire 12 (which removes the guidewire from within the inner tubular member 30), all while maintaining guidewire 12 in place.

[0053] Returning to distal tip 60, as illustrated in FIGS. 4A-4B and 6, distal tip 60 can have a variety of confirmations, but by way of non-limiting example, distal tip 60 comprises first 62 and second 66 ends having a smaller diameter than the medial region 64 thereof. In a preferred embodiment, each end is conical in shape so as to allow the tip 60 to wedge through an incompletely expanded stent when pulled proximally with respect to the stent. Moreover, the dual conical end design facilitates removal but sufficiently prevents the crimped stent from releasing from the stent retaining hub 70 and prematurely expanding. Distal tip 60 may alternatively have a flared medial region 64 so as to facilitate retrieval and retraction of a misaligned stent 12.

[0054] With respect to additional safety features incorporated in the present device 10, in a preferred embodiment, the device 10 has a deployment safety mechanism 18 that comprises male 46 and female 22 locking members that are brought into functional engagement as the stent is being deployed. Once the stent has reached the critical deployment point, the distal end of the stop 20 is substantially flush with the base 44 of the handle cavity 42 and the female locking members 22 of the stop 20 are in operative communication with the corresponding male locking members 46 formed on the interior surface of the cavity 42 of the handle. When the safety mechanism 18 is engaged as described above, the stent cannot be deployed further without physician intervention. In order to deploy the stent beyond this point, the physician has to rotate the stop 20 to cause the tab 24 to break. Once the tab 24 is broken, the device 10 is in the proceed orientation and deployment may proceed.

[0055] In a preferred embodiment, the physician will feel a tactile indication that the device 10 can be deployed further. Alternatively, the breaking of the tab may also, or as a substitute to tactile indication, results in an audible indication that further deployment is possible. Additionally, the physician is apprised of the fact that deployment beyond this point is irreversible except for interventional retrieval methods. As discussed earlier, the critical deployment point is preferably about 60% deployment, beyond which retraction is not recommended. As a result, the safety mechanism 18 removes the need to estimate extent of deployment and provides a reliable means of accurately deploying stents. Alternative locking mechanisms may be provided as long as they retain the important characteristic of giving the physician a sensory indication of extent of stent deployment and removes the need to estimate extent of deployment. By way of non-limiting example only, the locking mechanism could comprise a breakable seal, tab/stop lock, diverted channel locking mechanism, etc.

[0056] Referring particularly to FIG. 5, an alternative safety mechanism 118 is presented that is a principally a diverted channel mechanism. In practice, a detent 90 formed preferably on the hypotube has free proximal/distal travel to the critical deployment point at which time physician intervention is required to continue deployment. In a preferred embodiment, the Inner Tubular Member 30 is rotated until the travel of the detent is no longer obstructed. The channel in which the detent travels may be of a variety of geometrical shapes such as M, W, L, S Z, etc: the preferred geometry being substantially Z shaped, as shown in FIG. 5.

[0057] In an additional embodiment (not shown) of deployment safety mechanism 118, the device 10 has a deployment safety mechanism that comprises male and female locking members that are brought into functional engagement as the stent 12 is being deployed. Once the stent 12 has reached the critical deployment point, the male locking member cannot be advanced further because of a detent formed on the inner diameter of the outer tubular member catches the cavity formed on the corresponding portion of the male locking member. As a result, in order to further advance the device 10 to fully deploy stent 12, the inner tubular member must be rotated so as to break the detent. Once the detent is broken, the physician will feel a tactile indication that the device 10 can be deployed further.

[0058] Alternatively, the breaking of the detent may also, or as a substitute to tactile indication, results in an audible indication that further deployment is possible. Additionally, the physician is apprised of the fact that deployment beyond this point is irreversible except for interventional retrieval methods. As discussed earlier, the critical deployment point is preferably about 60% deployment, beyond which retraction is not recommended. As a result, the safety locking system 60 removes the need to estimate extent of deployment and provides a reliable means of accurately deploying stents. Alternative locking mechanisms may be provided as long as they retain the important characteristic of giving the physician a sensory indication of extent of stent deployment.

[0059] The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.