CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 62/455,021 filed on February 6, 2017, the disclosure of which is incorporated herein, in its entirety, by this reference.

BACKGROUND

[0002] The gallbladder is a muscular contractile organ composed of a glandular mucosa, lamina propria, smooth muscle layer, and serosa. The organ is located in the right upper quadrant of the abdomen and bounded by the liver and peritoneum. The gallbladder lumen includes a wide fundus that tapers into the neck and eventually terminating in the 2- 3 mm wide cystic duct outlet. The gallbladder is filled with concentrated bile, which is produced in the liver and stored in the gallbladder. Bile is excreted through the cystic duct and into the common bile duct when the gallbladder contracts. Contraction is stimulated by cholecystokinin release in the small intestine in the presence of food.

[0003] In order to treat certain medical conditions, it may be necessary to anchor an implantable medical device in the lumen of the gallbladder. For example, a filtering device in the gallbladder may be useful for preventing the passage of gallstones from one part of the organ to another or from the organ into the cystic duct. Gallstones range in size from microscopic crystals of cholesterol or calcium to greater than 5 cm in diameter. Gallstones, which are considered highest risk for obstruction, are those with diameters from 3 to 15 mm. Stones in this range can either get stuck at the tapered neck, or escape the organ and lodge downstream in the biliary system. Stones smaller than 2-3 mm pass through the biliary system without incident and stones larger than 10 mm are rarely able to fit through the small cystic duct outlet which is approximately 1 mm wide at rest but is distensible up to 4-5 mm.

[0004] The multi-layered wall, tapering geometry, gallstone size and behavior, and contractile function of the gallbladder all present design challenges, which must be overcome in order to safely and effectively anchor such a device inside the gallbladder lumen. Specifically, solutions are needed to address problems with imaging and delivery of the device to the organ, adequately anchoring the device, and removing the device without damaging or removing the gallbladder. SUMMARY

[0005] Embodiments disclosed herein relate to implantable medical device systems and methods of use. In an embodiment, an implantable medical device system includes an implantable medical device is disclosed. The implantable medical device includes a collar, an expandable body, and a plurality of legs. The collar is configured to detachably couple to at least one of a retrieval instrument or a delivery system. The expandable body extends from the collar and has one or more openings when the expandable body is in an expanded configuration. The expandable body includes a superelastic material and is configured to expand from a collapsed configuration for insertion into a subject to a substantially conical shape of the expanded configuration for anchoring within the subject. The plurality of legs extend from the expandable body distal to the collar.

[0006] In an embodiment, a method for implanting an implantable medical device into an organ of a subject is disclosed. The method includes inserting a portion of an outer release shaft of a hollow catheter of a delivery system at least partially into the organ of the subject. The hollow catheter houses the implantable medical device in a collapsed configuration. The implantable medical device includes a collar, and expandable body, and a plurality of legs. The collar is detachably coupled to a coupling element of an inner control shaft of the delivery system. The expandable body extends from the collar and has one or more openings when the expandable body is in an expanded configuration. The expandable body includes a superelastic material and is configured to expand from the collapsed configuration for insertion into the subject to a substantially conical shape of the expanded configuration for anchoring within the organ of the subject. The plurality of legs extend from the expandable body distal the collar. The method also includes sliding a sliding element on a handle of the delivery system operably coupled to the outer release shaft in a first direction to at least partially retract the outer release shaft of the hollow catheter of the delivery system until the collar of the implantable medical device is positioned outside the outer release shaft. The implantable medical device expands from the collapsed configuration to the expanded configuration as the implantable medical device exits the outer release shaft. When the collar of the implantable medical device is positioned outside the outer release shaft, the coupling element of the inner control shaft disengages from the collar to release the implantable medical device from the delivery system. The method also includes anchoring the plurality of legs within the organ of the subject when the implantable medical device is in the expanded configuration to filter objects having a predetermined size from passing through the organ. [0007] Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art through consideration of the following detailed description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The drawings illustrate several embodiments of the invention, wherein identical reference numerals refer to identical or similar elements or features in different views or embodiments shown in the drawings.

[0009] FIG. 1A is a side view of an implantable medical device in an expanded configuration, according to an embodiment.

[0010] FIG. IB is a top view of the implantable medical device shown in FIG. 1A in an expanded configuration, according to an embodiment.

[0011] FIG. 2A is an outer view of a leg of an implantable medical device, according to an embodiment.

[0012] FIG. 2B is an inner view of a leg of an implantable medical device, according to an embodiment.

[0013] FIG. 2C is a side view of a leg of an implantable medical device having a first radiopaque marker, according to an embodiment.

[0014] FIG. 2D is a side view of a leg of an implantable medical device having a second radiopaque marker, according to an embodiment.

[0015] FIG. 2E is a side view of a leg of an implantable medical device having a third radiopaque marker, according to an embodiment.

[0016] FIG. 3A is an isometric view of a collar of an implantable medical device, according to an embodiment.

[0017] FIG. 3B is a side view of a collar of an implantable medical device, according to an embodiment.

[0018] FIGs. 3C and 3D are side views of a collar of an implantable medical device, according to an embodiment.

[0019] FIG. 3E is a side view of a collar of an implantable medical device, according to an embodiment.

[0020] FIG. 4A is a side view of a delivery system, according to an embodiment.

[0021] FIG. 4B is a side view of a catheter of the delivery system of FIG. 4A, according to an embodiment. [0022] FIG. 4C is a side view of an implantable medical device released from the catheter of the delivery system of FIG. 4A, according to an embodiment.

[0023] FIG. 4D is a side view of a guidewire being inserted into the catheter of the delivery system of FIG. 4A, according to an embodiment.

[0024] FIG. 4E is an isometric view of a peel-away tube and a guidewire analog in the catheter of the delivery system of FIG. 4A, according to an embodiment.

[0025] FIG. 4F is an isometric view of a peel-away tube, according to an embodiment.

[0026] FIG. 4G is a side view of a peel-away tube peeled from delivery system after insertion of the guidewire into the catheter of the delivery system, according to an embodiment.

[0027] FIG. 4H is an isometric view of a funnel for guiding a tip of a guidewire into a peel-away tube, according to an embodiment.

[0028] FIG. 41 is a top view of a funnel guiding a tip of a guidewire into a peel away tube, according to an embodiment.

[0029] FIG. 4J is a top view of a handle of a delivery system, according to an embodiment.

[0030] FIG. 5A is a side view of a spacer spacing a handle of a delivery system from an introducer sheath, according to an embodiment.

[0031] FIG. 5B is an isometric view of an adjustable spacer, according to an embodiment.

[0032] FIG. 5C is an isometric view of a fixed spacer, according to an embodiment. DETAILED DESCRIPTION

[0033] Embodiments disclosed herein relate to implantable medical device systems and methods of for implanting a medical device into an organ of a subject. Delivering an implant to the gallbladder via a catheter-based percutaneous route relies on direct and indirect visualization of the anatomy and the device as the implant is delivered. Once gallbladder access is obtained using conventional ultrasound-guided and over-the-wire techniques, the implant may be visualized as the implant is released and fixed in position inside a neck of the gallbladder. It is further necessary to visualize the device in situ during follow-up visits. Visualization techniques and designs should be non-toxic to the patient, last the life of the device, and not impair the function of the implanted medical device. Owing to the attenuation of the human body, relatively low radiopacity of nickel-titanium alloy, and the small size of implants, many nickel-titanium alloy implants can be difficult to visualize using x-ray imaging and fluoroscopy. Thus, in some embodiments, radiopaque markers may be an advantageous element to assist in ensuring percutaneous delivery to the correct location, as well as confirming anchoring once the delivery system is removed.

[0034] A straight transhepatic access route that includes passage through the adherent portions of the liver and gallbladder is preferred. Passage through the adherent portions of both organs is preferred to minimize bile leakage and relies on the highly vascular liver to contribute a tamponade effect at the puncture site in the gallbladder wall. Bile has no coagulopathic factors in it while hepatic blood will clot over the puncture site, stopping any bile leakage. Furthermore, if leakage does occur at the puncture site bile will be contained to the small constrained area between the two organs and is prevented from leaking out into the sterile peritoneum. The length of this direct path is approximately 5-10 cm from skin to gallbladder lumen. However, in order to navigate to the neck of the organ from a transhepatic approach, a significant deviation is required. This angle may range from 0 to 45 degrees off the straight trajectory required to pass through the right lobe of the liver and enter the gallbladder where the two organs are adherent to each other.

[0035] When considering operator skill and technique, it may be desirable to design a delivery system that can be used successfully by a single operator. It is also desirable to design a delivery device for single-handed use, leaving the other hand free for guidewire manipulation, introducer stabilization, and imaging control. Any delivery system designed for percutaneous use in a luminal organ should be compatible with a number of existing guidewires, aspiration devices like syringes and tubing sets, and introducer sheaths. The delivery device should be sterile and disposable. The delivery device should also be clearly labeled and exhibit a form factor to facilitate proper use.

[0036] When catheter-based medical devices are used over a guidewire, it is common to deploy these devices over a guidewire through a separate catheter called an "introducer sheath". The introducer sheath is advanced into the body over a guidewire before the medical device is loaded onto the wire. An introducer sheath aids in maintaining position in a given lumen or vessel and provides a smooth conduit through which a medical device can be advanced and rotated. However, since catheter lengths are designed to accommodate variable anatomy and different sized patients, it is rarely necessary to advance the medical device to its maximum insertion point with respect to the introducer (i.e. to the point where the handle of the medical device is touching the hub of the introducer). In some cases, for example when placing a central venous catheter in the internal jugular vein, "hubbing" the dilator against the introducer sheath can have serious clinical consequences such as pneumothorax or hemothorax, which can be fatal if not detected and corrected immediately. In cases where the delivery system has a bend in the shaft, it can be important to ensure the bend is positioned outside of the introducer. In cases where the deployment shaft moves with respect to the handle, it can also be important to maintain spacing since visual cues on the shaft to help with depth of insertion are moved during deployment. And in cases where the handle of the medical device is optimally positioned some distance from the introducer hub, the weight of the handle can cause the medical device to slide or bend with gravity, making control and handling more difficult (to the point it requires an additional set of hands to manage) as well as even necessitating additional design elements in the catheter to avoid kinking or damage of the system. As far as catheter handling, most interventional radiologists are manually manipulating the delivery catheter while looking in a different direction at the fluoroscopy screen that shows the distal end of the catheter in the organ or target site of interest. Experienced and/or highly skilled clinicians are able to manually and awkwardly bridge the gap between the introducer and delivery system handle and thereby maintain handle position with respect to the introducer, but in some situations the clinician still requires an additional person to assist in maintaining relative positioning. A device that facilitates single operator operation of the catheter at the appropriate depth with respect to the introducer would be useful for reducing personnel, improving ease of procedure, and limiting the potential of device misuse in some situations.

[0037] Finally, a medical device placed in the gallbladder may need to be removed from the organ due to malpositioning, migration, or deposition build-up such that the device is no longer functioning. It is also conceivable that the patient may no longer require the implanted device to manage their condition, in which case it is preferable to be able to remove the device in as minimally invasive a method as possible. For example, it would be favorable if removal could be accomplished through the same percutaneous access route and visualization methods used to initially place the device.

[0038] This disclosure is directed to improvements and innovations necessary to deliver, position, and anchor a medical device in an organ of a subject, such as but not limited to the neck of the human gallbladder. In some embodiments, ultrasound and fluoroscopic imaging techniques may be used to assist in placement of the medical device in the gallbladder. Historically, instrumentation of the gallbladder under ultrasound and fluoroscopic visualization has been limited to drain placement, which is only broadly constrained to the body of the organ. Drain placement is always temporary and externalized through the skin. Described herein are embodiments of an implantable medical device and delivery system designed specifically for image-guided delivery of the implantable medical device to the tapered neck of the gallbladder, anchor the device in place, and remain in place for the life of the patient with no external instrumentation. Additionally, as it may be necessary to remove the implanted device at some point prior to removal of the entire gallbladder or the patient's death, embodiments are included to facilitate removal of the implantable medical device using various tools and techniques.

[0039] FIG. 1A is a side view of an implantable medical device 100 in an expanded configuration. The implantable medical device 100 includes a collar 110 configured to detachably couple to at least one of a retrieval instrument or a delivery system. The implantable medical device 100 is designed to conform to the anatomy of the gallbladder lumen, specifically to be positioned in the neck of the organ. The implantable medical device 100 is designed to remain inside the gallbladder long term (months or years), changing shape (contracting and elongating) as the gallbladder contracts or expands. While reference is made specifically to use with a human gallbladder herein, the implantable medical device 100 also may be used in other human or animal organs, as will become apparent to one of ordinary skill in the art upon review of this disclosure.

[0040] The implantable medical device 100 also includes an expandable body 120 extending from the collar 110 and having one or more openings 122 when the expandable body 110 is in an expanded configuration. The expandable body 120 is configured to expand from a collapsed configuration (shown in FIG. 4B) for insertion into a subject to a substantially conical shape of the expanded configuration for anchoring within the subject. When in the expanded configuration, the expandable body 100 of the implantable medical device 100 is in the shape of a cone in order to block the passage of objects, such as gallbladder stones, while maintaining sufficient surface area for bile flow through the implantable medical device 100. A distal facing design (wide part of cone facing the outlet) the implantable medical device 100 when implanted in the gallbladder of the subject is advantageous over a proximal facing design in order to minimize the surface area of the implantable medical device 100 in contact with the gallbladder wall.

[0041] The expandable body 120 includes or may be formed from a superelastic material, and the expandable body 120 may be cut from a single tube of the nickel-titanium alloy. The superelastic material may include a nickel-titanium superelastic alloy. More specifically, the single tube of superelastic material can be sized approximately 0.042" OD/0.030" ID and shape-set to a height of about 20 mm and a diameter of about 20 mm. At these dimensions the superelastic material can fit in the neck of the gallbladder when the implantable medical device is in the collapsed configuration. The superelastic material, such as Nitinol SE508, enables self-expansion of the expandable body 120 of the implantable medical device 100 to a desired geometry at body temperature. In some embodiments, the expandable body 120 of the implantable medical device 100 collapses to a diameter that is compatible with a delivery system (described in relation to FIGs. 4A-4J) with an outer diameter of about 4 French (about 1.4mm). The implantable medical device 100 itself has an Austenitic finish temperature below body temperature such that the expandable body 120 of the implantable medical device 100 elastically recovers to be at its pre-set shape in the body of the subject, but not so low that the device is exceedingly stiff in the body of the subject (10-30 °C).

[0042] In some embodiments, the expandable body 120 of the implantable medical device 100 includes a diamond strut architecture having a plurality of terminating points 124 distal the collar 110. The diamond strut architecture may include a plurality of diamond- shaped openings 122 when the expandable body 120 is in the expanded configuration. A diamond strut architecture may be advantageous to other expandable configurations because a diamond strut architecture provides the desired degree of porosity, while also allowing for less expensive manufacture via a laser cut pattern from one piece of superelastic tubing. In other embodiments, the expandable body 120 may include other architectures, while still being cut from one piece of superelastic tubing. For example, the expandable body may include an architecture that, when in the expanded configuration, has a substantially conical shape or other suitable shape, with one or more openings having an oval, circular, triangular, quadrilateral, or other polygonal shape or configuration.

[0043] FIG. IB is a top view of the implantable medical device 100 in the expanded configuration that the implantable medical device 100 may take in the gallbladder of the subject. When in the expanded configuration, each diamond-shaped opening 122 of the plurality of diamond- shaped openings of the implantable medical device 100 is sized to inhibit objects 140, such as gallstones, having a maximum lateral dimension 142 (e.g., a diameter) of about 2 mm to about 5 mm from passing through the plurality of diamond- shaped openings 122.

[0044] The implantable medical device 100 also includes plurality of legs 130 extending from the expandable body 120 distal to the collar 110. The plurality of legs 130 of the implantable medical device may extend from a portion of the plurality of terminating points 124 distal the collar 130 and include an anchoring barb. In some embodiments, the plurality of legs 130 of the implantable medical device 100 extend from the portion of the plurality of terminating points 124 in an alternating pattern such that (1) each leg of the plurality of legs 130 is positioned between to two terminating points of the plurality of terminating points 124 that are devoid of any legs of the plurality of legs 130, and (2) each terminating point of the plurality of terminating points 124 that is devoid of any legs of the plurality of legs 130 is positioned between two terminating points of the plurality of terminating points 130 having a leg of the plurality of legs 130 extending therefrom. More particularly, in some embodiments, the plurality of terminating points 120 of the diamond- strut architecture of the expandable body 120 includes at least six terminating points and the plurality of legs 130 includes at least three legs. In another embodiment, the plurality of terminating points 124 of the diamond-strut architecture of the expandable body 120 includes ten terminating points the plurality of legs 130 includes five legs. In yet another embodiment, the plurality of terminating points 124 of the diamond-strut architecture of the expandable body 120 includes twelve terminating points and the plurality of legs 130 includes six legs.

[0045] Considering the conical surface area, a six-legged embodiment of the implantable medical device 100 with a maximum inscribed circle diameter of 3.5 mm in the implantable medical device 100 design, 3.5, 3.0, 2.5, and 2.0 mm gallstones would have 0%, 1.4%, 5.5%, and 12.3% probabilities of passing through the implantable medical device 100, respectively. If considering the conical surface area of a similarly constructed five-legged embodiment of the device, and a maximum inscribed circle diameter of 3 mm in the implantable medical device 100 design, 3.0, 2.5, and 2.0 mm gallstones would have 0%, 1.7%, and 6.8% probabilities of passing through the implantable medical device 100, respectively. For a maximum inscribed diameter of the implantable medical device 100 of 4 mm, 4.0, 3.5, 3.0, 2.5, and 2.0 mm gallstones would have 0%, 0.9%, 3.5%, 8.0%, and 14.1% probabilities of passing through the implantable medical device 100, respectively.

[0046] FIGs. 2A-2E illustrate various views of a leg 130 of the plurality of legs. Each leg 130 of extends from a terminating point 124 at an intermediate portion 214 of the leg 130 between a leg end 212 of the leg 130 and an anchor end 216 of the leg 130. Each leg 130 is angled at about 30 degrees to about 60 degrees relative to an axis 150 (shown in FIG. 1A) extending through the collar 110 such that the leg 130 intersects a plane formed by the expandable body 120 at the terminating point 124 and the leg 110. In such positioning, the leg end 212 of the leg 130 is proximate the axis 150 and the anchor end 216 of the leg 130 is distal the axis 150. Deflection of backward facing anchor of the leg 130 outwards by about 30 degrees to about 60 degrees and incorporate arrowhead or barb features on the leg 130 increase the tenacity of anchoring of the implantable medical device 100 in the gallbladder.

[0047] The leg end 212 of each leg 130 may be recurved inward and the anchor end 216 of each leg 130 may include a point 218 (e.g., defining a barb or other retention structure). The leg end 212 may be curved inwards to create atraumatic tips so the implantable medical device 100 can be pushed into the taper of the neck of the gallbladder without harming the wall. For example, the implantable medical device 100 can be advanced into the taper of the neck for more secure anchoring. To further enhance passing through the secreting mucosal layer and anchoring into the gallbladder wall, the anchor 217 of the leg 130 can be sharpened to a point 218. The point 218 can be created by laser cut pattern and sharpening with sandpaper or a dremel. The anchors 217 of the plurality of legs 130 are designed to be long enough to penetrate through the mucosal layer and into the muscularis layer of the gallbladder wall but not protrude beyond the serosal layer. This translates to an anchor 217 length of 0.8 mm (assuming an angle of 60° and depth of 0.7 mm) to 3.0 mm long (assuming an angle of 30° and depth of 1.5 mm).

[0048] In order to visualize the certain features of the implantable medical device 100 using plain film X-ray or fluoroscopy, radiopaque markers may be fixed near the leg ends 212 of the legs 130 of the implantable medical device 100 and a sufficiently radiopaque collar is included near the collar 110 of the implantable medical device 100. Radiopaque distal legs and proximal collar provide sufficient visualization of the implant in all dimensions to facilitate delivery, expansion, and release of the implantable medical device 100 as well as enable long-term radiopaque visibility. The radiopaque marker can be formed from any number of biocompatible materials, including tantalum, platinum, iridium, platinum-iridium, combinations thereof, alloys thereof, etc.

[0049] In some embodiments, each leg 130 may include a radiopaque marker positioned on the leg 130 between the leg end 212 and the anchor end 216. For example, in FIG. 2C, the radiopaque marker includes a radiopaque band 222 coupled (wrapped or crimped) to the leg 130 between the leg end 212 and the anchor end 216. In another embodiment, shown in FIG. 2D, the radiopaque marker includes a radiopaque coiled wire 224 wrapped around the leg 130 between the leg end 212 and the anchor end 216. In this or other embodiments, the radiopaque marker may be coupled to a waist region 228 of the leg 130. The waste region 228 is narrower in width than the leg end 212. In another embodiment, shown in FIG. 2E, the radiopaque marker includes a coined radiopaque marker 226 coupled to the leg between the leg end 212 and the anchor end 216. The radiopaque marker may be a radiopaque marker printed or painted on the leg 130 between the leg end 212 and the anchor end 216. Coined markers 226 are a variation on press-fitting into a tight hole. These implementations of radiopaque markers may be advantageous for improving manufacturing consistency, speed, costs, and scalability.

[0050] As noted above, the collar 110 of the implantable medical device 100 is configured to detachably couple to at least one of a retrieval instrument or a delivery system. The implantable medical device 100 is deformable and the architecture incorporates a closed-cell design that enables re-collapse into a sheath if captured on the collar end (proximal end) and drawn into a tubular sheath (FIG. 4B). The collar 110 is large enough to enable snare capture and the barbed legs of the implantable medical device 100 can be retracted into a snare sheath without fragmentation.

[0051] In some embodiments, a slot feature is included on the collar to aid capture with a retrieval instrument. For example, The collar 110 may include at least one side slot on a side of the collar that is configured to detachably couple the collar to at least one of the retrieval instrument or the delivery system. FIGs. 3A-3E show various embodiments of collars configured having at least one side slot that is configured to detachably couple the collar to at least one of the retrieval instrument or the delivery system. Each of the collars shown in FIGs. 3A-3E may be coupled to or otherwise used in conjunction with the expandable body 120 describe above.

[0052] FIG. 3A shows a collar 310 having two opposing flat or U-shaped slots 312 on the side of the collar 310. FIG. 3B shows a collar 320 having two opposing D-shaped slots 322 on the side of the collar 320 to trap a tightening snare and irreversibly attach the snare to the collar 320. FIG. 3C and FIG. 3D show a collar 330 having two opposing angled flat or U-shaped slots on the side of the collar 330 that allow capture with a snare loop from more than one angle of approach. FIG. 3E shows a collar 340 having two opposing C- shaped slots on the side of the collar 340.

[0053] The implantable medical device 100 may include a proximal collar feature that can be captured using forceps or snare tools inserted into the gallbladder through an introducer advanced through the liver and into the gallbladder lumen (a technique similar to that used to implant the implantable medical device 100). As also shown in FIGs. 3A- 3E, the collar 120 also may include a top slot 310. The top slot 310 includes two opposing open necks 312 extending from a top of the collar distal the expandable body 120. Each open neck of the two opposing open necks 312 extends to a different rounded opening 314 on the collar 110. [0054] The implantable medical device 100 can be part of an implantable medical device system that also includes a delivery system or a retrieval instrument. FIGs. 4A-4I show various views of an embodiment of a delivery system 400. The implantable medical device 100 may be assembled into the delivery system 400 and packaged with the delivery system as a single product. Specifically, FIG. 4A shows a side view of a delivery system 400 configured to deploy the implantable medical device 100 into the subject. The delivery system includes a handle 410 and a hollow catheter 420. More specifically, the delivery system 400 for the implantable medical device 100 may include a medical grade polymer handle 410 coupled to a hollow catheter 420 that houses the implantable medical device 100.

[0055] FIG. 4B shows a more detailed view the hollow catheter 420. The hollow catheter 420 is coupled to the handle 410 and sized to house the implantable medical device system 100 in the collapsed configuration. In some embodiments, the hollow catheter can include a bend 425 of about 1 degree to about 45 degrees. The bend 425 enables more efficient aiming at the gallbladder neck, while utilizing a straight transhepatic path from skin to the lumen of the gallbladder. In one embodiment, the bend 425 is about 15 to about 30 degrees. The bend 425 may be located within the distal 3 cm of the delivery catheter 420 (after the implant is exposed) in order to have adequate control of orientation within the body of the gallbladder. The bend 425 will persist even after being passed through an introducer. A mark may be printed on the inner control shaft 424 to visually indicate to the clinician the point at which the bend at the tip will have been inserted past the tip of a particular length introducer. In some embodiments, the mark is located at the point where the bend would be fully unsheathed from an 11 cm introducer.

[0056] The catheter 420 includes an outer release shaft 422 and an inner control shaft 424. Together, outer release shaft 422 and an inner control shaft 424 are used to store and deliver the implantable medical device 100. The outer release shaft 424 is operably coupled to the sliding element 412 of the handle 410 such that the outer release shaft 424 moves in a first direction responsive to the sliding element 412 moving in the first direction and moves in a second direction responsive to the sliding element 412 moving in the second direction. The outer release shaft 422 can include a polyether ether ketone (PEEK) polymer and/or other suitable polymer to allow lubricity, hardness, and a high level of tensile strength despite thin walls.

[0057] The inner control shaft 424 is positioned at least partially within the outer release shaft 422 and includes a coupling element 426 configured to detachably couple to the collar 110 of the implantable medical device 100. The inner control shaft 424 can include stainless steel or other stiff material, such as a nickel-titanium alloy or other medical device relevant metals. When the implantable medical device 100 is in the collapsed configuration and housed within the catheter 420 with the collar 110 detachably coupled to the coupling element 426, moving the sliding element 412 of the handle 410 in the first direction at least partially retracts the outer release shaft 422 relative to the handle 410 and exposes at least a portion of the implantable medical device 100 for expansion of the implantable medical device 100 from the collapsed configuration. When the collar 110 is detachably coupled to the coupling element 426, moving the sliding element 412 of the handle 410 in the second direction at least partially re-sheaths the implantable medical device 100 within the catheter 420.

[0058] For example, in the new and unused state, or at other times, the sliding element 412 is at the forward-most position 471 (shown in FIG. 4J) on the handle 410. Retracting the sliding element 412 will pull back the outer release shaft 422 to expose and expand the implantable medical device 100. If the sliding element 412 is retracted without depressing the slider button 414, then the slider will automatically stop at an approximately two-thirds position 472 (shown in FIG. 4J) of the full stroke. At this point the implantable medical device 100 is still connected to the catheter 420. The sliding element is bidirectional and the implantable medical device 100 may be partially re-sheathed. When removing the delivery system 400 from the body after the implantable medical device 100 has been partially re- sheathed, the delivery system 400 may be retracted through an accompanying introducer sheath to prevent potentially exposed anchor tips from causing tissue damage.

[0059] In some embodiments, the catheter 420 has an external diameter small enough to be compatible with a 4 French (about 1.4mm diameter) introducer sheath, and an internal lumen large enough to accommodate a 0.018" guidewire and simultaneous aspiration and/or injection of bile, saline, and iodine contrast fluid. The handle 410 may include a male luer compatible with a hemostasis valve Y-connector for simultaneous guidewire access and aspiration and/or injection of fluids.

[0060] FIG. 4C shows the implantable medical device 100 outside of the catheter 420 and release from the delivery system 400. In some embodiments, the coupling element 426 of the inner control shaft 424 includes one or more biased paddles 428 configured to engage with at least one side slot on a side of the collar 110 when the collar 110 is positioned within the outer release shaft 420. The one or more biased paddles 428 may be flared or spring loaded paddles configured to lock into features on the collar 110 of the implantable medical device 100. When the outer release shaft 420 is retracted responsive to movement of the sliding element 412 in the first direction to expose the coupling element 426 of the inner control shaft 424, the one or more biased paddles 428 bias outward from the coupling element 426 and disengage from the at least one side slot on the side of the collar 110 to release the implantable medical device 100 from the delivery system 400. The implantable medical device 100 automatically expands to the expanded configuration when the implantable medical device 100 is released from the medical delivery system 400.

[0061] By way of another example, to disconnect the implantable medical device 100 from the catheter 420, the outer release shaft 422 is retracted, causing the paddles 428 on the inner control shaft 426 to flare outward and disengage from the implantable medical device 100. The slider button 414 can then be depressed and the sliding element 412 retracted to its full stroke position 473 (shown in FIG. 4J) to release the implantable medical device 100. After releasing the implantable medical device 100, but prior to retracting the delivery system 400 through the introducer, the sliding element 412 may be moved forward to the retracted position, such as an approximately two-thirds position 472 (shown in FIG. 4J) of the of the full stroke position. This step ensures that the paddles 428 are re-sheathed inside the delivery system 400 prior to removal from the body.

[0062] The inner control shaft 424 may have an interference fit with the implantable medical device 100. This mechanism is composed of the elastic or biased paddles 428 that securely hold onto the implantable medical device 100 when constrained and deflected inwards by the outer release shaft 422 until the release shaft is fully retracted and the elastic or biased paddles 428 are exposed and flare outwards. This enables the operator to expand the implant, position it, and confirm anchoring (tug test) prior to release.

[0063] Visibility of the catheter 420 under fluoroscopic imaging may be achieved by the inherent radiopacity of the stainless steel control shaft 424, and doping the component PEEK tubing of the release shaft 422 with barium sulfate. Visibility of the release shaft 422 also enables visualization of retraction of the release shaft 422 while the implantable medical device 100 is exposed. While only the distal tip 421 of the release shaft 422 needs to be visible, full length radiopacity also is acceptable.

[0064] Returning to FIG. 4A, the handle 410 includes a sliding element 412 slidably coupled to the handle 410. Some embodiments also include a slider button 414 on the sliding element 412 of the handle 410. In operation, if the slider button 414 is not depressed by an operator, then the sliding element 412 automatically stops at a first predetermined position when the sliding element 412 is moved in the first direction and only a portion of the implantable medical device 100 is exposed by retraction of the outer release shaft 422. If the slider button 414 is depressed by the operator, the sliding element 412 is configured to slide past the first predetermined position to a second predetermined position. With the sliding element 412 in the second predetermined position, the outer release shaft 422 is retracted to expose the coupling element 426 of the inner control shaft 424, and the one or more biased paddles 428 bias outward from the coupling element 426 and disengage from the at least one side slot on the side of the collar 110 to release the implantable medical device 100 from the delivery system 400.

[0065] In some embodiments, the handle 410 also may include a locking mechanism 416 configured to selectively lock the sliding element 412 in a predetermined position. The handle 410 may include locking/unlocking mechanisms for exposure and release of the implantable medical device 100 from the delivery catheter. For example, a safety pin can prevent initial exposure of the implantable medical device 100, and a button 416 can be depressed for final release of the implantable medical device 100. The safety pin may penetrate through one outer wall of the handle 410 and into the sliding element 412, thereby securing the sliding element 412 from moving in relation to the handle 410. The delivery system 400 also may include has a male luer fitting 411 at the proximal end of the handle 410 to connect a syringe for irrigation and aspiration during the procedure.

[0066] The catheter delivery system 400 may utilize a traditional guidewire access, and that guidewire access should not be allowed to interfere with the deployment of the implantable medical device 100. Additionally, it is advantageous to minimize the diameter of the catheter 420 as much as possible. Therefore, a guidewire insertion aid is described herein. In one or more embodiments, a removable thin-walled, peel-away tube 430 may be used. The peel-away tube 430 is inserted through the distal end of the constrained implantable medical device 100 before the implantable medical device 100 is packaged in order to: a) protect the lumen of the implantable medical device 100 and b) provide a smooth conduit for a guidewire 445 to be inserted past the implantable medical device 100 during the delivery procedure.

[0067] The peel-away tube 430 is very thin-walled, and thus does not require any more luminal diameter as compared to a device with fluid aspiration/injection capabilities. In some embodiments, the peel-away tube 430 is about 0.001 inches to about 0.010 inches think. In some embodiments, the peel-away tube is about 0.004 inches thick. The peel- away tube 430 also possesses a longitudinal slit along the portion that surrounds the guidewire 445 to allow easy removal from the guidewire 445 without requiring a guidewire change-out. The guide of the peel-away tube 430 can be pulled perpendicular to the guidewire 445 and the slit will deform around the guidewire 445 as the peel-away tube is removed (shown in FIG. 4G). Once the guidewire 445 is loaded in the delivery system 400, the peel-away tube 430 is peeled away and the procedure continues.

[0068] Some disclosed embodiments assist in loading the distal tip 421 of a catheter onto a 0.018" guidewire 445. The wire loading guide 432 protects against disruption of the implantable medical device 100 constrained in the distal tip 421 of the catheter 420 while the tip 442 of the guidewire 445 is loaded. The guide 432 is a temporary, disposable, thin- walled tube that resides within the inner diameter of the constrained implantable medical device 100 and has a lumen large enough to accept a slightly smaller diameter guidewire 445. In one embodiment, the lumen is 0.020 inches in diameter to allow a 0.018 inch diameter guidewire to pass. An example of the loading guide 432 of a peel-away tube 430 is shown in FIGs. 4E and 4F. The stiff tip 442 of the guidewire 445 is inserted into the distal opening of the loading guide 432 and advanced into the delivery catheter. Once the tip 442 of the guidewire 445 is past the implantable medical device 100 and is sufficiently inside of the catheter 420, the loading guide 432 is removed by pulling it out of the catheter 420. A longitudinal slit is incorporated along the length of the loading guide 432 and the peel-away tube 430 so the loading guide 432 and the peel-away tube 430 can be peeled away from the guidewire 445.

[0069] The disclosed embodiments may prevent an inserted guidewire 445 from disrupting the constrained implantable medical device 100 while taking up minimal luminal space and not adding additional profile to the overall catheter 420. A temporary guidewire analog 460 (shown in FIG. 4E) can be inserted to protect the guidewire entry opening on the peel-away tube 430 during shipping.

[0070] FIG. 4D shows a guidewire 445 as the guidewire 445 is inserted into the catheter 420 housing the implantable medical device 100. As shown in FIG. 4D, a peel- away tube 430 positioned partially within the implantable medical device 100 when the implantable medical device 100 is housed within the hollow catheter 420. The peel-away tube 430 is sized to receive a guidewire 445 when the peel-away tube 430 is positioned within the implantable medical device 100. The peel-away tube may include a wire loading guide 432 positioned outside a distal tip 421 of the hollow catheter 420 distal the handle 410 when the peel-away tube 430 is positioned at least partially within the implantable medical device 100. The wire loading guide 100 is configured to receive a guidewire tip 442 (shown in FIG. 41) of the guidewire 445 for insertion of the guidewire 445 into the peel-away tube 430 when the peel-away tube 430 is positioned within the implantable medical device 100.

[0071] Some embodiments of an implantable medical device system may include other apparatus configured to efficiently load the guidewire 445 into the catheter 420 when the implantable medical device 100 is housed within the catheter 420. For example, in some embodiments, the guide can include a distal opening that is flared, tabbed, with a funnel attached, other grip-aids 455 (shown in FIG. 4D), and/or visibly marked in order to assist the guidewire 445 loading into the small lumen of the implantable medical device 100. These additional embodiments can be designed to be low cost and manufacturing-friendly.

[0072] As an example, if tabbed or with a funnel attached, the tab or funnel can be made of materials that are cheap and easy to bond to the portion of the guide inserted into the lumen of the filter. As another example, the funnel can be molded, which can allow bonding at the same time as funnel molding and thereby removing a bonding step which would also reduce manufacturing cost. The molded component can have visual aids integrated into the mold shape, thereby eliminating the need to have a time-consuming marking step to increase ease of use for clinicians. FIGs. 4H and 41 show an embodiment of a funnel 450 configured to detachable couple to the peel-away tube 430 when the peel- away tube is positioned within the implantable medical device 100. The funnel 450 is configured to guide the guidewire 445 into the peel-away tube 430 when the peel-away tube 430 is positioned within the implantable medical device 100.

[0073] After removal of any of the guides disclosed herein, the delivery system 400 can be more compliant due to the removal of the additional material and thereby facilitate use in more tortuous anatomy, as compared to a stiffer delivery system with a permanent shaft or tube. Similarly, this can preserve maximum luminal space for fluid flow through the implantable medical device without increasing outer diameter. In addition, the guide can be made of a radiopaque material such that it will be clear if it is mistakenly pushed into the delivery system 400, reducing the chance that it will end up in the patient during the procedure.

[0074] Some embodiments of an implantable medical device system also can include a plastic spacer configured to maintain a fixed distance between the handle of a medical device and an introducer sheath being used over the same guidewire. For example, as shown in FIG. 5A, a spacer 520 may be an apparatus situated on the catheter 420 of the delivery system 400 that maintains position or location of the handle 410 of the delivery system 400 relative to an introducer hub 532 of the introducer sheath 530. The spacer 520 can be attached on the handle 410 after the device is loaded into the guidewire 445, or the spacer can be permanently or reversibly attached to the handle 410 during manufacture or prior to loading onto the guidewire 445 during a procedure.

[0075] Embodiments of spacers described herein may be advantageous to the clinician or user of the delivery system 400 because the spacers allow for hands and eyes-free control over the position of the handle 410 of the delivery system 100 relative to the introducer sheath 530. This advantage may be important for most interventional radiologists because they are manually manipulating the handle 410 of the delivery system 400 while looking in a different direction at the fluoroscopy screen that shows the distal end 421 of the catheter 420 in the organ or target site of interest. Maintaining the position of the handle 410 of the delivery system 400 relative to the introducer sheath 430 is particularly important for pin- and-pull delivery systems. If the delivery system is too far proximal relative to the introducer sheath 430, there is potential for the implantable medical device to be deployed within the introducer sheath 430, which interferes with positioning and deployment of the implantable medical device. The clinician cannot just maintain relative position between the introducer sheath 430 and catheter 420 because the outer surface of the catheter 420 moves relative to the handle 410 of the delivery system during deployment of the implantable medical device 100. Currently, experienced and/or highly skilled clinicians are able to use their non-dominant hand to awkwardly bridge the gap between the introducer and delivery system handle, and thereby maintain appropriate position. The spacer would obviate the need for that hand maneuver, which would be advantageous for the clinician because it would allow them to use that hand for other functions such as adjusting the C-arm used for visualization, or more finely adjusting the orientation of the delivery system. Additionally, the spacer would potentially allow less skilled clinicians to easily use the medical device, which would increase the market appeal, market penetration, and usability of the system.

[0076] Additionally, a sufficiently stiff spacer can reduce the need to have internal stiffening elements in the medical device, which can be advantageous for less-stiff devices, which are potentially better at navigating more tortuous anatomy. The additional "stiffening" function will reduce the need for an extra pair of hands to separately support the delivery system, and permit a single operator to maintain control over the device and introducer.

[0077] In some embodiments, the spacer can fit a shaft from 1-8 mm in diameter, and have a length of about 1 mm to about 10 cm. The spacer also can fit over a range of introducer sizes. In particular embodiments, the spacer fits about a 1.4 mm catheter shaft and adjusts for a range of lengths of about 1 mm to about 10 cm, and fits over a 4 French introducer.

[0078] FIG. 5B depicts a particular embodiment of an adjustable spacer 510. In this and other embodiments, the instrument retaining components of the adjustable spacer 510 can be adjusted along the length 512 of the adjustable spacer 510 to accommodate different fixed distances between instruments. The adjustable spacer 510 includes a first clasp 516 configured to couple to the introducer hub 532 and a second clasp 514 configured to couple to the catheter 410 and interface the handle 410 of the delivery system 400.

[0079] FIG. 5C depicts another embodiment of a fixed spacer 520. In this and other embodiments the fixed spacer 520 includes a fixed length and slit 522 to be applied over a guidewire 445 or instrument already in use with the distal tip of the instrument inside the patient's body. The fixed spacer 520 includes a first end 524 sized to receive the introducer hub 532 and a second end 526 opposite the first end 524. The second end 526 is positioned to interface with the handle 410 or other component of a delivery system.

[0080] Also disclosed herein is a method for implanting an implantable medical device into an organ of a subject. The method can include an act of inserting a portion of an outer release shaft of a hollow catheter of a delivery system at least partially into the organ of the subject. The hollow catheter houses the implantable medical device in a collapsed configuration. The implantable medical device includes a collar, an expandable body, and a plurality of legs. The collar is detachably coupled to a coupling element of an inner control shaft of the delivery system. The expandable body extends from the collar and has one or more openings when the expandable body is in an expanded configuration. The expandable body includes a superelastic material and is configured to expand from the collapsed configuration for insertion into the subject to a substantially conical shape of the expanded configuration for anchoring within the organ of the subject. The plurality of legs extend from the expandable body distal the collar.

[0081] In some embodiments, inserting the portion of the outer release shaft of the hollow catheter of the delivery system at least partially into the organ of the subject includes using a bend of about 1 degree to about 45 degrees in the hollow catheter to the portion of the outer release shaft of the delivery system at a neck of the organ while utilizing a straight transhepatic path from skin of the subject to the organ.

[0082] In some embodiments inserting the portion of the outer release shaft of the hollow catheter of the delivery system at least partially into the organ of the subject includes: (1) advancing the shaft of the hollow catheter of the delivery system through a percutaneous access route in the subject to a gallbladder of the subject; and (2) inserting the portion of the outer release shaft of the hollow catheter into a gallbladder neck of the gall bladder of the subject.

[0083] The method also includes an act of sliding a sliding element on a handle of the delivery system operably coupled to the outer release shaft in a first direction. Sliding the sliding element in the first direction at least partially retracts the outer release shaft of the hollow catheter of the delivery system until the collar of the implantable medical device is positioned outside the outer release shaft. As the implantable medical device exits the outer release shaft, the implantable medical device expands from the collapsed configuration to the expanded configuration. When the collar of the implantable medical device is positioned outside the outer release shaft, the coupling element of the inner control shaft disengages from the collar to release the implantable medical device from the delivery system.

[0084] In some embodiments, sliding the sliding element on the handle of the delivery system in the first direction includes sliding the sliding element on the handle of the delivery system in the first direction to at least partially retract the outer release shaft of the hollow catheter of the delivery system until (1) the collar of the implantable medical device is positioned outside the outer release shaft and (2) one or more biased paddles of the coupling element bias outward from the coupling element and disengage from at least one side slot on the collar to release the implantable medical device from the delivery system.

[0085] In even more particularly embodiments, sliding the sliding element on the handle of the delivery system in the first direction includes: (1) sliding the sliding element on the handle of the delivery system in the first direction until the sliding element is stopped at a first predetermined position to partially retract the outer release shaft of the hollow catheter of the delivery system with only a portion of the implantable medical device positioned outside the outer release shaft and the collar positioned within the outer release shaft; (2) depressing a slider button on the sliding element; and (3) sliding the sliding element in the first direction past the first predetermined position to at least partially retract the outer release shaft of the hollow catheter of the delivery system until the collar of the implantable medical device is positioned outside the outer release shaft and the one or more biased paddles bias outward from the coupling element and disengage from the at least one side slot of the collar to release the implantable medical device from the delivery system. [0086] In some embodiments, sliding the sliding element on the handle of the delivery system in the first direction to at least partially retract the outer release shaft of the hollow catheter of the delivery system until the collar of the implantable medical device is positioned outside the outer release shaft includes sliding the sliding element on the handle, positioned outside the subject, in the first direction to at least partially retract the outer release shaft of the hollow catheter of the delivery system until the collar of the implantable medical device is positioned outside the outer release shaft and inside the gallbladder neck of the gallbladder of the subject. The implantable medical device expands from the collapsed configuration to the expanded configuration in the gallbladder neck as the implantable medical device exits the outer release shaft and the implantable medical device is released from the delivery system when the coupling element of the inner control shaft disengages from the collar.

[0087] The method also includes anchoring the plurality of legs within the organ of the subject when the implantable medical device is in the expanded configuration to filter objects having a predetermined size from passing through the organ. Anchoring the plurality of legs within the organ of the subject may include anchoring the plurality of legs of the implantable medical device in an alternating pattern within the organ of the subject. The plurality of legs of the implantable medical device may extend from a portion of a plurality of terminating points on a diamond strut architecture of the expandable body cut from a single tube of the superelastic material such that: (1) each leg of the plurality of legs is positioned between to two terminating points of the plurality of terminating points that are devoid of any legs of the plurality of legs anchoring the implantable medical device to the organ of the subject; and (2) each terminating point of the plurality of terminating points that is devoid of any legs of the plurality of legs is positioned between two terminating points of the plurality of terminating points having a leg of the plurality of legs extending therefrom and anchoring the implantable medical device to the organ of the subject.

[0088] In some embodiments, anchoring the plurality of legs of the implantable medical device in an alternating pattern within the organ of the subject includes anchoring each leg of the plurality of legs to the organ of the subject at angle of about 30 degrees to about 60 degrees relative to an axis extending through collar such that the leg intersects a plane formed by the expandable body at the terminating point and the leg.

[0089] In some embodiments, anchoring the plurality of legs within the organ of the subject when the implantable medical device is in the expanded configuration to filter objects having the predetermined size from passing through the organ includes anchoring the plurality of legs within the gallbladder neck of the gallbladder of the subject when the implantable medical device is in the expanded configuration to filter gallbladder stones having the predetermined size from passing through the gallbladder neck of the gallbladder.

[0090] In some embodiments, the method also includes filtering, with the implantable medical device, one or more gallbladder stones having the predetermined size from passing through the one or more openings of the implantable medical device and into the gallbladder neck of the gallbladder. The predetermined size of the one or more gallbladder stones is a lateral dimension of about 2.0 mm to about 3.0 mm, about 2.0 mm to about 3.5 mm, or about 2.0 mm to about 4.0 mm.

[0091] In some embodiments, the method also includes retrieving the implantable medical device from the gallbladder of the subject. More particularly, the implantable medical device may be retrieved from the gallbladder of the subject by: (1) advancing a sheath of a retrieval instrument through the percutaneous access route in the subject to the gallbladder of the subject; (2) inserting a portion of the sheath of the retrieval instrument into the gallbladder neck of the gall bladder of the subject; (3) coupling a sheath tip of the sheath to the collar of the implantable medical device; (4) collapsing the implantable medical device to the collapsed configuration while drawing the implantable medical device into the sheath; and (5) removing the sheath of the retrieval instrument from the gallbladder of the subject while the implantable medical device is housed within the sheath.

[0092] The method also may include an act of determining a location of the implantable medical device in the organ of the subject using one or more radiopaque markers positioned on one or more legs of the plurality of legs. The method also may include an act of selectively locking the sliding element in a predetermined position with a locking mechanism on the handle.

[0093] The method also may include an act of inserting a tip of a guidewire into a wire loading guide of a peel-away tube positioned partially within the implantable medical device when the implantable medical device is housed within the hollow catheter, the wire loading guide positioned outside a distal tip of the hollow catheter distal the handle. The method also may include an act of detachably coupling the wire loading guide to a funnel such that inserting the tip of the guidewire into the wire loading guide includes inserting the tip of the guidewire into the wire loading guide through the funnel detachably coupled to the wire loading guide. The method also may include an act of advancing the tip of the guidewire into the hollow catheter and at least partially through the implantable medical device. The method also may include an act of removing the peel-away tube while the tip of the guidewire is in the hollow catheter. The method also may include an act of advancing the implantable medical device along the guidewire. The method also may include an act of detachably coupling the wire loading guide to a funnel such that inserting the tip of the guidewire into the wire loading guide includes inserting the tip of the guidewire into the wire loading guide through the funnel detachably coupled to the wire loading guide.

[0094] The method also can include an act of coupling an introducer sheath to the guidewire. The method also can include an act of advancing the introducer sheath to the organ of the subject. The method also can include an act of coupling the introducer sheath to a first spacer coupling of a spacer, the spacer including a predetermined length. The method also can include an act of coupling the hollow catheter of the delivery system to a second spacer coupling of the spacer distal to the first spacer coupling before inserting the portion of the outer release shaft of the hollow catheter of the delivery system at least partially into the organ of the subject to inhibit the handle of the delivery system from interfacing the introducer sheath.

[0095] The method also can include an act of sliding the sliding element on the handle of the delivery system in a second direction to at least partially re-sheath the implantable medical device within the catheter.

[0096] While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting.