WO2008148014A2

WO2008148014A2 - Polymer coated stent

Info

Publication number: WO2008148014A2
Application number: PCT/US2008/064733
Authority: WO
Inventors: Chandrashekhar P. Pathak; Robert M. Carr, Jr.
Original assignee: C.R. Bard, Inc.
Priority date: 2007-05-23
Filing date: 2008-05-23
Publication date: 2008-12-04
Also published as: WO2008148014A3

Abstract

An expandable vascular implant is disclosed and can include a body comprising a shape memory material that can have a shape memory temperature. Further, the vascular implant can include a coating on the body that can have a phase transition temperature. The phase transition temperature is greater than the shape memory temperature.

Description

POLYMER COATED STENT

FIELD OF THE DISCLOSURE

The present disclosure relates generally to surgical devices. More specifically, the present disclosure relates to stents.

BACKGROUND

Stents can be used to treat various medical disorders. For example, stents can be used in urology, endovascular surgery, etc. Moreover, stents can be used to treat vascular stenosis.

Vascular stenosis is an abnormal narrowing in a blood vessel. Vascular stenosis can include peripheral artery stenosis, coronary artery stenosis, carotid artery stenosis, and renal artery stenosis. There exist several ways to detect vascular stenosis. For example, a vascular stenosis can be detected using a stethoscope to amplify bruit, i.e., noise, within the blood vessel due to turbulent blood flow through the narrowed blood vessel. Alternatively, one or more imaging methods can be used to detect and locate a vascular stenosis. For example, ultrasound, magnetic resonance imaging, and computed tomography can be used to detect and locate a vascular stenosis.

A common cause of vascular stenosis is atherosclerosis. Atherosclerosis, aka, hardening of the arteries, is a disease that affects the arterial blood vessel. Atherosclerosis is caused by the formation of multiple plaques within the arteries. As plaque builds up within an artery, the diameter of the artery is reduced and results in a stenosis.

Vascular stenosis can be treated using a stent. A stent can be from a shape memory material or a non-shape memory material. A stent made from a non-shape memory material can be installed on a balloon catheter and then, threaded through a patient's cardiovascular system to the stenosis. Once the stent is in place within the stenosis, the balloon catheter can be inflated in order to deform the stent and move the stent to an expanded configuration. Thereafter, the balloon catheter can be deflated and withdrawn from the patient.

A stent made from a shape memory material can be installed on a catheter and a sleeve can be placed over the stent. The catheter and sleeve can be threaded through a patient's cardiovascular system to the stenosis. Once the stent is in place within the stenosis, the sleeve can be removed from the stent. When exposed to the patient's body temperature, the stent automatically can move to an expanded configuration that corresponds to a shape memory configuration. Unfortunately, as the stent is being inserted into the patient, the stent is being warmed to the shape memory temperature, i.e., the temperature at which the stent moves to the expanded configuration. This can cause the stent to deploy immediately upon removal of the sheath. Accordingly, there is a need for an improved stent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a stent delivery device;

FIG. 2 is a plan view of a handle for a stent delivery device;

FIG. 3 is a cross-section view of the handle;

FIG. 4 is a plan view of the stent delivery device engaged with the handle;

FIG. 5 is a plan view of a stent in a collapsed configuration;

FIG. 6 is a plan view of the stent in an expanded configuration;

FIG. 7 is a cross-section view of a strut of the stent; and

FIG. 8 is a flow chart illustrating one method of installing and deploying a stent.

DETAILED DESCRIPTION OF THE DRAWINGS

An expandable medical implant is disclosed and can include a body comprising a shape memory material that can have a shape memory temperature. Further, the medical implant can include a coating on the body that can have a phase transition temperature. The phase transition temperature is greater than the shape memory temperature.

In another embodiment, a stent is disclosed and can include a stent body. The stent body can include a shape memory material and the stent body is configured to move from a collapsed configuration to an expanded configuration. The stent further includes a coating on the stent body. The coating is configured to move from a structurally stable state to a structurally unstable state. In the structurally stable state, the coating substantially prevents the stent body from moving to the expanded configuration.

In yet another embodiment, a method of installing a stent within a patient is disclosed and can include expelling the stent from a stent delivery device to a target location within a cardio vascular system of a patient and exposing the stent to laser energy.

In still another embodiment, an expandable medical implant is disclosed and can include an expandable structure and a restrictive structure engaged with the expandable structure. The expandable medical implant is movable from a restricted configuration to an unrestricted configuration. In the restricted configuration, the restrictive structure prevents expansion of the expandable structure. Further, in the unrestricted configuration, the restrictive structure permits expansion of the expandable structure. DESCRIPTION OF A STENT DELIVERY DEVICE

Referring to FIG. 1, a stent delivery device is shown and is generally designated 100. As shown, the stent delivery device 100 includes a body 102 having a proximal end 104 and a distal end 106. A first syringe attachment 108 can be formed in the body 102 between the proximal end 104 and the distal end 106. In a particular embodiment, the first syringe attachment 108 can be a Luer syringe attachment. The first syringe attachment 108 can provide fluid communication to a lumen formed within an outer sheath 110, described below.

FIG. 1 indicates that the stent delivery device 100 can include an outer sheath 110. The outer sheath 110 can include a proximal end 112 and a distal end 114. Further, the outer sheath 110 can extend from the distal end 106 of the body 102 of the stent delivery device 100. In particular, the proximal end 112 of the outer sheath 110 can be attached to the distal end 106 of the body 102 of the stent delivery device 100. The distal end 114 of the outer sheath 110 can be relatively soft and rounded. The outer sheath 110 can include a lumen 116 formed therein. Further, the distal end 114 of the outer sheath 110 can include a radiopaque band 118.

As illustrated in FIG. 1, the stent delivery device 100 can further include an inner carrier catheter 120. The inner carrier catheter 120 can extend through the body 102 of the stent delivery device 100 and into the lumen 116 formed in the outer sheath 110. The inner carrier catheter 120 can be coaxial with the outer sheath 110. Further, the inner carrier catheter 120 can include a proximal end 122 and a distal end 124. The inner carrier catheter 120 can be formed with a lumen (not shown) that can be sized to fit over a guide wire. In particular, the lumen of the inner carrier catheter 120 can fit over a 0.035 inch guide wire.

As shown in FIG. 1, a stent 126 can be compressed between the inner catheter 120, e.g., the distal end of the inner catheter 120, and the outer sheath 110. A handle 128 can be attached to, or otherwise extend from, the proximal end 122 of the inner carrier catheter 120. The handle 128 can include a proximal end 130 and a distal end 132. The proximal end 130 of the handle 128 can include a second syringe attachment 134. In a particular embodiment, the second syringe attachment 134 can be a Luer syringe attachment. The second syringe attachment 134 can provide fluid communication with the lumen formed within the inner carrier catheter 120.

The stent delivery device 100 can also include a safety clip 140 installed between the body 102 of the stent delivery device 100 and the handle 128 of the inner carrier catheter 120. The safety clip 140 can include a proximal end 142 and a distal end 144. Further, the safety clip 140 can include a butterfly handle 146 between the proximal end 142 of the safety clip 140 and the distal end 144 of the safety clip 140. In a particular embodiment, the safety clip 140 can be installed between the body 102 of the stent delivery device 100 and the handle 128 of the inner carrier catheter 120 such that the proximal end 142 of the safety clip 140 abuts the distal end 132 of the handle 128 and the distal end 144 of the safety clip 140 abuts the proximal end 104 of the body 102. The safety clip 140 can fit over the inner carrier catheter 120. Further, the safety clip 140 can prevent the body 102 of the stent delivery device 100 from moving relative to the handle 128 of the inner carrier catheter 120. Further, the safety clip 140 can prevent the outer sheath 110 from sliding relative to the inner carrier catheter 120. During use, the stent delivery device 100 can be threaded into a cardiovascular system of a patient to a target area. The radio opaque band 118 formed on the outer sheath 110 can be used to guide the stent delivery device into the cardiovascular system of a patient, e.g., with the aid of fluoroscopy. Further, a pair of radiopaque bands on the stent 126 can aid in positioning the stent 126 within the patient. Once the stent 126 is properly positioned, the butterfly handle 146 can be squeezed in order to remove the safety clip 140 from the inner carrier catheter 120 and the stent delivery device 100. Thereafter, the body 102 of the stent delivery device 100 can be moved toward the handle of the inner carrier catheter 120 in order to slide the outer sheath 110 off of the stent 126 and expose the stent 126 inside the patient.

Once the stent 126 is exposed within the patient, the stent 126 can be deployed within the patient by exposing the patient to a laser having a wavelength of approximately seven hundred and eighty nanometers (780 nm). The energy can melt a polymer on the stent 126 and allow the stent 126 to move to a shape memory configuration, e.g., an expanded configuration, within the patient, and be deployed within the patient. After the stent 126 is deployed, the inner carrier catheter 120 can be withdrawn from the patient.

FIG. 2 and FIG. 3 illustrate a handle assembly, generally designated 200 that can be used in conjunction with the stent delivery system 100, described above. As shown in FIG. 2 and FIG. 3, the handle assembly 200 can include a housing 202. The housing 202 can be hollow and can include a proximal end 204 and a distal end 206.

As depicted in FIG. 3, a rail support structure 208 can be disposed within the housing 202 near the proximal end 204 of the housing 202. A pair of rails 210 can extend between the distal end 206 of the housing 202 and the rail support structure 208. The handle assembly 200 can also include a carrier 212 that can be slidably disposed on the rails 210. In a particular embodiment, the carrier 212 can be configured to receive the body of a stent delivery system, e.g., the stent delivery system 100, described above.

A shaft 214 can extend from the housing 202 near the rail support structure 208, e.g., between the rail support structure 208 and the distal end 206 of the housing 202. In a particular embodiment, the shaft 214 is substantially perpendicular to the rails 210. A ratchet wheel 216 can be rotatably disposed on the shaft 214. The ratchet wheel 216 can be formed with a plurality of teeth 218 around the outer periphery of the ratchet wheel 216. The handle assembly 200 can also include a pawl 220 extending from the rail support structure 208. The pawl 220 can be configured to engage the ratchet wheel 216, e.g., the teeth 218 of the ratchet wheel 216, and permit rotation of the ratchet wheel 216 in a single direction, e.g., clockwise. FIG. 3 further shows that the handle assembly 200 can include a cable 222. The cable 222 can include a proximal end 224 and a distal end 226. The cable 222 can extend within the housing along the length of the rails 210. Further, the proximal end 224 of the cable 222 can be wrapped, or otherwise disposed, around the ratchet wheel 216. The distal end 226 of the cable 222 can be attached, or otherwise affixed, to the carrier 212. As the ratchet wheel 216 is rotated, the cable 222 can be rolled onto the ratchet wheel 216 and the carrier 212 can slide along the rails 210 toward the proximal end 204 of the housing 202.

As illustrated in FIG. 3, the handle assembly 200 can also include a trigger 228 extending from the housing 202. The trigger 228 can include a proximal end 230 and a distal end 232. The proximal end 230 of the trigger 228 can be rotatably engaged with the housing 202 and the distal end 232 of the trigger 228 can be free. As such, the trigger 228 can rotate around the proximal end 230 of the trigger 228.

FIG. 3 further indicates that an arm 234 can extend from the trigger 228. The arm 234 can include a plurality of teeth 236 that can engage the teeth 218 formed on the ratchet wheel 216. The handle assembly 200 can also include a spring 238 installed around a post 240 within the housing 202. The spring 238 can bias the trigger 228 outward relative to the housing 202. In a particular embodiment, when the trigger 228 is squeezed inward relative to the housing 202, the arm 234 can rotate the ratchet wheel 216 and cause the carrier 212 to slide within the housing 202 toward the proximal end 204 of the housing 202.

In a particular embodiment, the stent delivery device 100 can be engaged with the handle assembly 200 as shown in FIG. 4. Specifically, the body 102 of the stent delivery device 100 can be inserted within the carrier 212. Further, the inner carrier catheter shown at 120 in FIG. 1 can be installed within the housing 202 of the handle assembly 200 so that the handle shown at 128 in FIG. 1 extends through the proximal end 204 of the housing 202. The handle 128 of the inner carrier catheter 120 can be engaged with the housing 202 so that the handle 128 does not move relative to the housing during operation of the handle assembly 200.

Accordingly, the safety clip shown at 140 in FIG. 1 can be removed from the stent delivery device 100 and the trigger 228 can be squeezed to move the carrier 212 within the handle assembly 200 toward the proximal end 204 of the housing 202. As the carrier 212 moves, the body 102 of the stent delivery device 100 can be moved toward the handle 128 of the inner carrier catheter 120. As the body 102 of the stent delivery device 100 moves toward the handle of the inner carrier catheter 120, the outer sheath shown at 110 in FIG. 1 can slide off of the stent 126 and expose the stent 126 inside a patient.

DESCRIPTION OF A POLYMER COATED STENT

Referring to FIG. 5 and FIG. 6, a polymer coated stent is shown and is generally designated 500. As shown, the stent 500 can include a stent body 502. The stent body 502 can be hollow and generally cylindrical. Further, the stent body 502 can include a proximal end 504 and a distal end 506. The proximal end 504 can include a radiopaque band 508 incorporated therein. The distal 506 can also include a radiopaque band 510 incorporated therein.

As indicated in FIG. 5 and FIG. 6, the stent body 502 can include a plurality of struts 512. Further, the struts 512 can be arranged to establish a plurality of cells 514 within the stent body 502.

In a particular embodiment, the stent 500 can be movable between a collapsed configuration, shown in FIG. 5, and an expanded configuration, shown in FIG. 6. FIG. 5 and FIG. 6 show that the stent 500 can have a diameter 516. The diameter 516 of the stent 500, in the collapsed configuration, is relatively smaller than the diameter 516 of the stent 500 in the expanded configuration. In the collapsed configuration, the cells 514 within the stent body 502 can be collapsed, or otherwise compressed, as indicated in FIG. 5. Conversely, in the expanded configuration the cells 514 within the stent body 502 can be expanded, as indicated in FIG. 6.

In a particular embodiment, the stent 500 can be an expandable structure made from a shape memory material. The shape memory material can include a shape memory polymer, a shape memory metal, or a combination thereof. Further, the shape memory metal can include a metal alloy. The metal alloy can be a nickel titanium alloy, e.g., nitinol. The stent body 502 can have a shape memory temperature at which the stent body 502 deploys from a compressed configuration to an expanded configuration. The shape memory temperature can be approximately equal to human body temperature, i.e., thirty-seven degrees Celsius (37° C).

FIG. 7 illustrates a cross-section of one of the struts 510 of the stent body 502. As shown in FIG. 7, the stent 500 can include a coating 518. In a particular embodiment, the coating 518 can at least partially cover or coat the external surfaces of each strut 510. The coating 518 can overlie the external surface of the struts 510 defining an exterior of the stent body 502, an interior of the stent body 502, internal surfaces of the struts 510 bridging the external surface and internal surface of the stent body 502, or a combination thereof.

The coating 518 can act as a restrictive structure that is engaged with the stent body 502 and the coating 518 can maintain the stent in a restricted configuration. In the restricted configuration, the coating 518 can substantially prevent the stent 500 from expanding while the coating is stable. However, the coating 518 can be rendered unstable in order to allow the stent 500 to expand. In lieu of a coating 518, some other covering, layer, etc., can be used to restrict the stent 500 and prevent the stent from expanding. For example, a fabric can be placed around the stent body 502 in order to prevent the stent 500 from expanding. The fabric can be rendered unstable, e.g., as described herein, to allow the stent 500 to move to an unrestricted, e.g., expanded, configuration.

In a particular embodiment, the stent 500 can be dip coated with a polymer in order to establish the coating 518 on the stent. The coating 518 can have a thickness that is in a range of one micron to one thousand microns (1 μm - 1000 μm). In a particular embodiment, the coating 518 can prevent the stent 500 from expanding when the stent 500 is deployed within a patient at a temperature required to move the stent 500 to a shape memory position. However, the coating 518 can be melted, sublimed, or vaporized, as described herein, in order to allow the stent 500 to move to the expanded shape memory position. The coating 518 can have a phase transition temperature that corresponds to a temperature at which the coating 518 is rendered unstable, i.e., the coating 518 is semi-solid, liquid, vapor. In a particular embodiment, the phase transition temperature can be at least two degrees (2° C) greater than the shape memory temperature of the stent body 502. In another embodiment, the phase transition temperature can be at least five degrees (5° C) greater than the shape memory temperature of the stent body 502. In yet another embodiment, the phase transition temperature can be at least ten degrees (10° C) greater than the shape memory temperature of the stent body 502. In still another embodiment, the phase transition temperature can be at least twenty degrees (20° C) greater than the shape memory temperature of the stent body 502. In yet still another embodiment, the phase transition temperature can be at least thirty degrees (30° C) greater than the shape memory temperature of the stent body 502. In another embodiment, the phase transition temperature is at most fifty (50° C) greater than the shape memory temperature of the stent body 502.

The coating 518 can be a thermoplastic polymer material having a melting point greater than thirty-eight degrees Celsius (38° C) and less than or equal to one hundred degrees Celsius (100° C). For example, the thermoplastic polymer can include polyolefm, polyamide, polyester, acrylic polymer, vinyl acetate, polyurethane, fluoropolymer, polyethylene glycol, or a combination thereof. In a particular embodiment, the polyester can include polycaprolactone.

In a particular embodiment, the coating 518 can include a thermochromic dye compounded therein. For example, the coating 518 can include at least one-tenth percent (0.1%) thermochromic dye compounded therein. In another embodiment, the coating 518 can include at least one half percent (0.5%) thermochromic dye compounded therein. In another embodiment, the coating 518 can include at least three-quarters percent (0.75%) thermochromic dye compounded therein. In yet another embodiment, the coating 518 can include at least one percent (1%) thermochromic dye compounded therein. In still another embodiment, the coating 518 can include at least one and one-half percent (1.5%) thermochromic dye compounded therein. In yet still another embodiment, the coating 518 can include at least two percent (2%) thermochromic dye compounded therein. In another embodiment, the coating 518 can include at least two and one-half percent (2.5%) thermochromic dye compounded therein. In still another embodiment, the coating 518 can include at least three percent (3%) thermochromic dye compounded therein. In yet another embodiment, the coating 518 can include at least ten percent (10%) thermochromic dye compounded therein. In still another embodiment, the coating 518 can include at least thirty percent (30%) thermochromic dye compounded therein. In another embodiment, the coating 518 can include no greater than seventy percent (70%) thermochromic dye compounded therein. Each of the above percentages can be measured by weight. In a particular embodiment, the thermochromic dye can include a color that is not found in a human body in substantial quantities. The thermochromic dye should absorb light within a wavelength range that is not readily absorbed by tissue, blood elements, physiological fluids, water, or a combination thereof. As such, when a laser is used to activate the thermochromic dye the radiation provided by the laser can be absorbed primarily, or selectively, by the thermochromic dye and not by tissue in the patient.

For example, the thermochromic dye can have an absorption wavelength in a range of two hundred and fifty nanometers to one thousand three hundred nanometers (250 nm - 1300 nm). More particularly, the thermochromic dye can have an absorption wavelength in a range of three hundred nanometers to one thousand nanometers (300 nm - 1000 nm). Even more particularly, the thermochromic dye can have an absorption wavelength in a range of five hundred nanometers to eight hundred and fifty nanometers (500 nm - 850 nm). Specifically, the thermochromic dye can have an absorption wavelength of approximately seven hundred and eighty nanometers (780 nm). In a particular embodiment, the thermochromic dye can include an indocyanine green dye. In an alternative embodiment, the coating 518 can be a photochromic material or include photochromic material, e.g., a photochromic dye.

The stent 500 described herein can be deployed using a stent delivery system, e.g., the stent delivery system 100 described above. Further, a catheter capable of delivering or emitting laser energy can be used in conjunction with the stent delivery system. For example, the catheter can include a fiber optic cable therein. Alternatively, the catheter can be a fiber optic cable. The laser energy can be delivered at the distal end of the stent delivery system 100. In a particular embodiment, the laser energy can have a wavelength of approximately seven hundred and eighty nanometers (780 nm). The energy can be selected such that the absorption of the thermochromic dye is substantially maximized.

In other embodiments, various light sources can be use to illuminate the stent 500 and deploy the stent. For example, these light sources can conventional light sources such as mercury lamps, halogen lamps, tungsten lamps, etc. The light from these sources can be concentrated, e.g., using a lens, a collimator, or similar device, to increase the light intensity for deploying the stent 500. Other light sources, e.g., laser-based light sources can also be used to deploy the stent 500. The laser-based light sources can include an argon ion laser emitting at five hundred and twelve nanometers (512 nm), a helium-neon laser emitting at six-hundred and thirty two nanometers (632 nm), and other semiconductor based light sources emitting in a range of seven hundred and fifty nanometers to eight hundred and fifty nanometers (750 nm - 850 nm). Various devices, or methods, can be used to deliver the light energy to the stent. For example, one or more fiber optic cables can be used to deliver the light energy. Alternatively, one or more liquid-based delivery methods can also be used to deliver the light energy.

During deployment, the stent 500 can be delivered to a location within a patient using the stent delivery system 100. The stent 500 can be pushed out, or otherwise expelled from, the stent delivery system 100. After the stent 500 is located within the patient, the stent 500 can be radiated with energy from the laser. The thermochromic dye can absorb the laser energy and convert the laser energy to heat. The heat from the thermochromic dye can increase the temperature of the coating 518 on the stent 500. The coating 518 can undergo a phase transformation, e.g., the coating can melt, vaporize, or sublimate. Once the coating 518 undergoes the phase transformation, the coating 518 can be rendered structurally unstable and the stent 500 can move from the collapsed configuration to the expanded configuration within the patient.

Accordingly, if the coating 518 remains structurally stable, the coating 518 can prevent the stent body 502 from moving to the expanded configuration. However, when the coating 518 is rendered structurally unstable, the coating 518 can allow the stent body 502 to move to the expanded configuration. In a particular embodiment, after the coating 518 is rendered structurally unstable, the coating 518 can then be biodegraded within the patient.

In a particular embodiment, the laser energy can be delivered via the stent delivery system 100. In another embodiment, the laser energy can be directed to the stent 500 from a location external to the patient. Since the laser energy comprises a frequency that cannot be absorbed by the tissue of the patient, the laser energy can pass through the patient to the stent 500 and get absorbed by the thermochromic dye in the coating 518 of the stent 500. In yet another embodiment, an ultrasonic -based heating system can be used to heat the stent 500 to melt the coating 518 and allow the stent 500 to move to the expanded configuration.

DESCRIPTION OF A METHOD OF INSTALLING A STENT

Referring to FIG. 8, a method of installing a stent within a patient is shown and commences at block 800. At block 800, a stent delivery device can be engaged with a cardio vascular system of a patient. At block 802, the stent delivery device can be moved through the cardio vascular system.

Moving to decision step 804, it can be determined whether a target within the patient is reached. The location of the stent within the patient can be determined using fluoroscopy and one or more radiopaque bands on the stent, the stent delivery device, or both. If the target is not reached within the patient, the method can return to block 802 and continue as described herein. If the target is reached, the method can proceed to block 806 and the stent can be expelled from the stent delivery device.

Proceeding to block 808, the stent can be exposed to laser energy to move the stent to the expanded configuration. In a particular embodiment, the laser energy can be delivered to the stent via the stent delivery device. Alternatively, the laser energy can be delivered from a location outside of the patient and directed at the stent with the aid of fluoroscopy and one or more radiopaque bands on the stent. At block 810, the stent delivery device can be withdrawn from the patient. The method can then end at state 812. CONCLUSION

With the configuration of embodiments described above, a stent that can be delivered to a location within a patient and deployed in a controlled manner. Embodiments can be made from a shape memory material having a shape memory temperature equal to approximately thirty-seven degrees Celsius (37° C), i.e., human body temperature. Even though a stent may be exposed to the shape memory temperature once it is installed in a patient, a polymer coating on the stent can prevent the stent from moving to a shape memory configuration, e.g., an expanded configuration. However, once the stent is deployed in a desired location within the patient, the polymer coating can be rendered unstable using an energy source, e.g., a laser. For example, the polymer coating can undergo a phase transformation, e.g., the polymer coating can be melted, vaporized, or sublimated.

Once the polymer coating is rendered unstable, the polymer coating can no longer prevent the movement of the stent to the expanded configuration. As such, the stent can move to the expanded configuration within the patient. The polymer coating allows for a controlled deployment. In other words, embodiments can be placed exactly in a desired location and then, moved to the expanded configuration. The controlled deployment can minimize the likelihood of early deployment that is associated with typical shape memory stents.

In an alternative embodiment, other expandable vascular implants, e.g., an expandable stent graft, an expandable embolic filter, an expandable vena cava filter, an expandable embolization coil, an expandable urological stent, or an another expandable implant, can be coated as described herein in order to provide a controlled deployment of the expandable vascular implant.

In certain surgical applications, e.g., a transjugular intrahepatic portosystemic shunt (TIPS) procedure, a partially coated stent may be desirable. The partially coated stent can include a stent graft that is completely coated. After the stent graft is implanted, a portion of the coating can be removed using laser energy as described herein.

The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments that fall within the true spirit and scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.

Claims

WHAT IS CLAIMED IS:

1. An expandable medical implant, comprising: a body comprising a shape memory material, wherein the shape memory material includes a shape memory temperature; and a coating on the body, wherein the coating includes a phase transition temperature greater than the shape memory temperature.

2. The expandable medical implant of claim 1, wherein the shape memory temperature is at least two degrees (2°) greater than the shape memory temperature.

3. The expandable medical implant of claim 2, wherein the shape memory temperature is at least five degrees (5°) greater than the shape memory temperature.

4. The expandable medical implant of claim 3, wherein the shape memory temperature is at least ten degrees (10°) greater than the shape memory temperature.

5. The expandable medical implant of claim 4, wherein the shape memory temperature is at least twenty degrees (20°) greater than the shape memory temperature.

6. The expandable medical implant of claim 5, wherein the shape memory temperature is at least thirty degrees (30°) greater than the shape memory temperature.

7. The expandable medical implant of claim 1, wherein the body is configured to be deployed to a location within a patient and wherein the body is substantially prevented from moving to a shape memory configuration by the coating.

8. The expandable medical implant of claim 1, wherein the shape memory material comprises a shape memory polymer.

9. The expandable medical implant of claim 8, wherein the shape memory material comprises a shape memory alloy.

10. The expandable medical implant of claim 9, wherein the shape memory alloy comprises a nickel titanium alloy.

11. The expandable medical implant of claim 1 , wherein the phase transition temperature is not greater than one hundred degrees Celsius (100° C).

12. The expandable medical implant of claim 1, wherein the coating comprises a thermoplastic polymer.

13. The expandable medical implant of claim 12, wherein the thermoplastic polymer comprises polyolefin, polyamide, polyester, acrylic polymer, vinyl acetate, polyurethane, fluoropolymer, polyethylene glycol, or a combination thereof.

14. The expandable medical implant of claim 13, wherein the polyester comprises polyc aprol actone .

15. The expandable medical implant of claim 12, wherein the coating further comprises a thermochromic dye compounded with the thermoplastic polymer.

16. The expandable medical implant of claim 15, wherein the coating comprises at least one-tenth percent (0.1%), by weight, of the thermochromic dye compounded therein.

17. The expandable medical implant of claim 16, wherein the coating comprises at least one half percent (0.5%), by weight, of the thermochromic dye compounded therein.

18. The expandable medical implant of claim 17, wherein the coating comprises at least three-quarters percent (0.75%), by weight, of the thermochromic dye compounded therein.

19. The expandable medical implant of claim 18, wherein the coating comprises at least one percent (1%), by weight, of the thermochromic dye compounded therein.

20. The expandable medical implant of claim 19, wherein the coating comprises at least one and one-half percent (1.5%), by weight, of the thermochromic dye compounded therein.

21. The expandable medical implant of claim 20, wherein the coating comprises at least two percent (2%), by weight, of the thermochromic dye compounded therein.

22. The expandable medical implant of claim 21, wherein the coating comprises at least two and one-half percent (2.5%), by weight, of the thermochromic dye compounded therein.

23. The expandable medical implant of claim 22, wherein the coating comprises at least three percent (3%), by weight, of the thermochromic dye compounded therein.

24. The expandable medical implant of claim 15, wherein the thermochromic dye comprises a color that is not found in a human body in substantial quantities.

25. The expandable medical implant of claim 24, wherein the thermochromic dye comprises an absorption wavelength in a range of two hundred and fifty nanometers to one thousand three hundred nanometers (250 nm - 1300 nm).

26. The expandable medical implant of claim 25, wherein the absorption wavelength is in a range of three hundred nanometers to one thousand nanometers (300 nm - 1000 nm).

27. The expandable medical implant of claim 26, wherein the absorption wavelength is in a range of five hundred nanometers to eight hundred and fifty nanometers (500 nm - 850 nm).

28. The expandable medical implant of claim 27, wherein the absorption wavelength is approximately seven hundred and eighty nanometers (780 nm).

29. The expandable medical implant of claim 28, wherein the thermochromic dye comprises a green color.

30. The expandable medical implant of claim 29, wherein the thermochromic dye comprises an indocyanine green dye.

31. The expandable medical implant of claim 30, wherein the coating comprises a thickness in a range of one micron to one thousand microns (1 μm - 1000 μm).

32. The expandable medical implant of claim 1, wherein the expandable medical implant comprises a stent.

33. The expandable medical implant of claim 1, wherein the expandable medical implant comprises a stent graft.

34. The expandable medical implant of claim 1, wherein the expandable medical implant comprises an embolic filter.

35. A stent, comprising: a stent body, wherein the stent body comprises a shape memory material and wherein the stent body is configured to move from a collapsed configuration to an expanded configuration; and a coating on the stent body, wherein the coating is configured to move from a structurally stable state to a structurally unstable state, wherein in the structurally stable state, the coating substantially prevents the stent body from moving to the expanded configuration.

36. The stent of claim 35, wherein in the structurally unstable state, the coating allows the stent body to move to the expanded configuration.

37. The stent of claim 36, wherein the coating is rendered unstable when radiated with energy from a laser.

38. The stent of claim 37, wherein the coating comprises a thermoplastic polymer compounded with a thermochromic dye.

39. The stent of claim 38, wherein the thermochromic dye converts energy from the laser to heat energy.

40. The stent of claim 39, wherein the heat energy from the thermochromic dye renders the coating unstable when a predetermined temperature is reached.

41. A method of installing a stent within a patient, the method comprising: expelling the stent from a stent delivery device to a target location within a cardio vascular system of a patient; and exposing the stent to laser energy.

42. The method of claim 41, wherein a coating on the stent is rendered structurally unstable by the laser energy.

43. The method of claim 42, wherein the stent comprises a shape memory material and wherein the stent is configured to move to an expanded configuration when the coating is rendered structurally unstable.

44. An expandable medical implant, comprising: an expandable structure; and a restrictive structure engaged with the expandable structure, wherein the expandable medical implant is movable from a restricted configuration in which the restrictive structure prevents expansion of the expandable structure and an unrestricted configuration in which the restrictive structure permits expansion of the expandable structure.

45. The expandable medical implant of claim 44, wherein the expandable medical implant is movable from the restricted configuration to the unrestricted configuration by exposing the restrictive structure to an energy source.