Device for controlling reperfusion of tissue

Abstract

A device (100, 200, 300, 400, 500, 600, 700) for controlling reperfusion of tissue to avoid damage to the tissue includes a stent (120, 220, 320, 420, 520, 620, 720) implantable in a vasculature of a patient, the stent having an inner surface that defines a stent opening through the stent having a stent inner diameter; and a bio-resorbable layer (130, 230, 330, 430, 530, 630, 730) arranged on the inner surface of the stent at a predetermined thickness forming a restricted opening through the stent to accommodate blood flow, where the restricted opening has a restricted inner diameter that is initially narrower than the stent inner diameter. The bio- resorbable layer includes at least one bio-resorbable material configured to dissolve over time causing a size of the restricted inner diameter of the restricted opening to gradually increase over time, enabling an amount of blood flowing through the stent to increase as the restricted inner diameter of the restricted opening increases.

Description

DEVICE FOR CONTROEEING REPERFUSION OF TISSUEBACKGROUND

[0001] Coronary heart disease (CHD) and peripheral vascular disease (PVD) impact many people worldwide, and are leading causes of death. Obstruction of blood vessels is one of the main causes of CHD and PVD, so it is important in treating these diseases to restore the blood supply by removing the obstruction as soon as possible, for example, by placing a stent in the blood vessel. However, doing so may result in an adverse effect called reperfusion injury, which is damage from the blood supply returning to quickly to tissue after a period of ischemia or lack of oxygen caused by the obstruction. The absence of oxygen and nutrients from blood during the ischemic period creates a condition in which the restoration of circulation results in inflammation and oxidative damage. This leads to a paradoxical situation in which removing the cause of the disease (the vascular obstruction) results in even more damage to the tissue.

[0002] It is challenging to restore circulation and thus the blood supply to the tissue caused by the occlusion of the blood vessel as soon as possible, while preventing or reducing reperfusion injury, such that the outcome results in maximal recovery of the tissue at risk. Restoring the circulation all at once will restore the perfusion of the myocardial tissue, for example, but the reperfusion will cause damage to this tissue making this a suboptimal solution. Various conventional techniques are directed to limiting inflammation and oxidative damage that occurs after restoring the blood supply. Currently these methods must be provided before or after the blood supply restoring treatment. Essential is that the reperfusion treatment should not result in a delay of (partially) restoring the circulation. Since restoring the blood supply and preventing reperfusion injury are separate treatments makes finding the optimal timing of these therapies to have an optimal result difficult.SUMMARY

[0003] According to a representative embodiment, a device is provided for controlling reperfusion of tissue to avoid damage to the tissue. The device includes a stent implantable in a vasculature of a patient, the stent having an inner surface that defines a stent opening through thestent having a stent inner diameter; and a bio-resorbable layer arranged on the inner surface of the stent at a predetermined thickness forming a restricted opening through the stent to accommodate blood flow, where the restricted opening has a restricted inner diameter that is initially narrower than the stent diameter. The bio-resorbable layer includes at least one bioresorbable material configured to dissolve over time causing a size of the restricted inner diameter of the restricted opening to gradually increase over time, enabling an amount of blood flowing through the stent to increase as the restricted inner diameter of the restricted opening increases.

[0004] According to another representative embodiment, a method is provided for controlling reperfusion of tissue to avoid damage to the tissue implemented by a device including a stent having a bio-resorbable layer formed of bio-resorbable material on an inner surface of the stent, where the bio-resorbable layer defines a restricted opening through the stent by predetermined thickness of the bio-resorbable material, the restricted opening having a restricted inner diameter that is initially narrower than a stent inner diameter of a stent opening defined by the inner surface of the stent. The method includes inserting the stent in a vasculature of a patient using a catheter to accommodate blood flow through the vasculature; deploying the stent through the catheter at a site of an obstruction, where the stent expands within the vasculature to remove the obstruction and to allow blood flow to begin through the restricted opening of the bioresorbable layer; and dissolving the bio-resorbable material in the bio-resorbable layer over time in response to the blood flowing through the restricted opening through bio-resorbable layer, causing the restricted opening to widen over time until the restricted opening is substantially the same size as the stent opening, enabling unrestricted blood flow through the stent.

[0005] According to another representative embodiment, a device is provided for controlling reperfusion of tissue to avoid damage to the tissue. The device includes a stent implantable in a vasculature of a patient, the stent having an inner surface that defines a stent opening through the stent having a stent inner diameter; and a bio-resorbable layer arranged on the inner surface of the stent. The bio-resorbable layer includes at least one porous bio-resorbable material including multiple pores enabling blood flow of blood through the bio-resorbable layer, where sizes of the pores in the porous bio-resorbable material respectively increase over time in response to theblood flow, enabling an amount of blood flowing through the stent to increase as the sizes of the of pores increases.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The example embodiments are best understood from the following detailed description when read with the accompanying drawing figures. It is emphasized that the various features are not necessarily drawn to scale. In fact, the dimensions may be arbitrarily increased or decreased for clarity of discussion. Wherever applicable and practical, like reference numerals refer to like elements.

[0007] FIG. 1A is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue to avoid damage to the tissue, according to a representative embodiment.

[0008] FIG. IB is a latitudinal cross-sectional view of the device for controlling reperfusion of tissue to avoid damage to the tissue, according to a representative embodiment.

[0009] FIG. 1C is a longitudinal cross-sectional view of the device for controlling reperfusion of tissue at an intermediate different stages of dissolution of a bio-resorbable layer within the device, according to a representative embodiment.

[0010] FIG. ID is a longitudinal cross-sectional view of the device for controlling reperfusion of tissue at an end stage of dissolution of the bio-resorbable layer within the device, according to a representative embodiment.

[0011] FIG. 2 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including multiple sub-layers of bio-resorbable material, according to a representative embodiment.

[0012] FIG. 3 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including multiple sub-layers of bio-resorbable material with separating gaps, according to a representative embodiment.

[0013] FIG. 4 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including a bio-resorbable layer having a tapered shape, according to a representative embodiment.

[0014] FIG. 5 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including a bio-resorbable layer having a conical shape, according to a representativeembodiment.

[0015] FIG. 6 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including a bio-resorbable layer having a stepped shape, according to a representative embodiment.

[0016] FIG. 7 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including a bio-resorbable layer having a rotationally asymmetrical shape, according to a representative embodiment.

[0017] FIG. 8 is a flow diagram of a method for controlling reperfusion of tissue to avoid damage to the tissue following removal of an obstruction in vasculature of a patient, according to a representative embodiment.DETAILED DESCRIPTION

[0018] In the following detailed description, for purposes of explanation and not limitation, representative embodiments disclosing specific details are set forth in order to provide a thorough understanding of an embodiment according to the present teachings. Descriptions of known systems, devices, materials, methods of operation and methods of manufacture may be omitted so as to avoid obscuring the description of the representative embodiments. Nonetheless, systems, devices, materials and methods that are within the purview of one of ordinary skill in the art are within the scope of the present teachings and may be used in accordance with the representative embodiments. It is to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be limiting. The defined terms are in addition to the technical and scientific meanings of the defined terms as commonly understood and accepted in the technical field of the present teachings.

[0019] It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements or components, these elements or components should not be limited by these terms. These terms are only used to distinguish one element or component from another element or component. Thus, a first element or component discussed below could be termed a second element or component without departing from the teachings of the inventive concept.

[0020] The terminology used herein is for purposes of describing particular embodimentsonly, and is not intended to be limiting. As used in the specification and appended claims, the singular forms of terms “a,” “an” and “the” are intended to include both singular and plural forms, unless the context clearly dictates otherwise. Additionally, the terms “comprises,” and / or “comprising,” and / or similar terms when used in this specification, specify the presence of stated features, elements, and / or components, but do not preclude the presence or addition of one or more other features, elements, components, and / or groups thereof. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0021] Unless otherwise noted, when an element or component is said to be “connected to,” “coupled to,” or “adjacent to” another element or component, it will be understood that the element or component can be directly connected or coupled to the other element or component, or intervening elements or components may be present. That is, these and similar terms encompass cases where one or more intermediate elements or components may be employed to connect two elements or components. However, when an element or component is said to be “directly connected” to another element or component, this encompasses only cases where the two elements or components are connected to each other without any intermediate or intervening elements or components.

[0022] As used in the specification and appended claims, and in addition to their ordinary meanings, the terms “substantial” or “substantially” mean to within acceptable limits or degree. As used in the specification and the appended claims and in addition to its ordinary meaning, the term “approximately” means to within an acceptable limit or amount to one having ordinary skill in the art. For example, “approximately the same” means that one of ordinary skill in the art would consider the items being compared to be the same.

[0023] In view of the foregoing, the present disclosure, through one or more of its various aspects, embodiments and / or specific features or sub-components, is thus intended to bring out one or more of the advantages as specifically noted below. For purposes of explanation and not limitation, example embodiments disclosing specific details are set forth in order to provide a thorough understanding of an embodiment according to the present teachings. However, other embodiments consistent with the present disclosure that depart from specific details disclosed herein remain within the scope of the appended claims. Moreover, descriptions of well-known apparatuses and methods may be omitted so as to not obscure the description of the exampleembodiments. Such methods and apparatuses are within the scope of the present disclosure.

[0024] Generally, according to various embodiments, a bio-resorbable layer of bioresorbable material is provided around an inner surface of a stent placed in the vasculature of a patient to remove an obstruction. The bio-resorbable layer has a predetermined thickness that creates an opening through the stent. The diameter of the opening gradually increases over time as the bio-resorbable material dissolves and allows the inner diameter of the opening through the stent to increase to a final diameter, where the final diameter may be the inner diameter of the stent with no bi-resorbable layer. The dissolving time of the bio-resorbable material may be tuned, such that the tissue damage due to deprived blood supply and the tissue damage due to the reperfusion damage can have more time to adapt to the new status (gradual adaptation) such that at the end the optimal tissue recovery is achieved.

[0025] FIG. 1 A is a longitudinal cross-sectional view and FIG. IB is a latitudinal cross- sectional view of a device for controlling reperfusion of tissue to avoid damage to the tissue, according to a representative embodiment. FIGs. 1C and ID are longitudinal cross-sectional views of the device for controlling reperfusion of tissue at different stages of dissolution of a bioresorbable layer within the device, according to a representative embodiment .

[0026] Referring to FIGs. 1A and IB, a device 100 is placed in vasculature 110 (e.g., blood vessel or artery) of a patient to address an obstruction (not shown) that has blocked or substantially reduced blood flow through the vasculature 110, depriving tissue located downstream from the obstruction of blood. As used herein, an obstruction be any material or object that fully or partially blocks the vasculature 110, such as plaque, calcium, a thrombus (clot) or an embolus, for example. The device 100 is configured to open the vasculature 110 in a controlled manner to enable gradual reperfusion of the tissue downstream from the obstruction to avoid damage to the tissue.

[0027] The device 100 may be placed in the vasculature 110 in a known manner. For example, a catheter may be inserted into the vasculature 110 from the wrist or the groin of the patient, and guided to the location of the obstruction using medical imaging, such as X-rays or ultrasound. A guide wire may be fed through the catheter, and the device 100 may be inserted in a collapsed state through the catheter along the guide wire to the location of the obstruction. Once in place, the device 100 is expanded from the collapsed (undeployed) state to an expanded(deployed) state to fit the walls of the vasculature 110, widening the obstructed part of the vasculature 110. Once the device 100 is in place, the catheter and wire are removed.

[0028] In the depicted embodiment, the device 100 includes a stent 120 implantable in the vasculature 110 and a bio-resorbable layer 130 arranged on an inner surface of the stent 120. The stent is placed at the location of the obstruction, e.g., using a catheter or other acceptable technique, and expanded to enable blood to begin flowing through the vasculature 110. In the expanded state, the stent 120 has an inner surface that defines a stent opening that passes longitudinally through the stent 120 having a stent inner diameter ds. The bio-resorbable layer 130 is formed of a bio-resorbable material arranged on the inner surface of the stent 120 at a predetermined thickness. The stent 120 is formed of a non-bio-resorbable material capable of expanding within the vasculature 110. The stent 120 may be self-expanding and therefore formed by a material having shape memory, such as nitinol, for example. Alternatively, the stent 120 may be expanded by a balloon that is inflated when the stent is placed at the obstruction location and then deflated for retraction. The stent 120 may be formed of any compatible material, such as nitinol, stainless steel, platinum, gold or titanium, as would be apparent to one skilled in the art. The bio-resorbable layer 130 thus forms a restricted opening 135 to accommodate blood flow through the stent 120, the direction of which is indicated by arrow BF. The restricted opening 135 has a restricted inner diameter drthat is initially narrower than the stent inner diameter ds. The bio-resorbable layer 130 is substantially cylinder shaped in the depicted configuration.

[0029] The bio-resorbable material in the bio-resorbable layer 130 is configured to dissolve over time as it is exposed to the blood flowing through the restricted opening 135. As the bioresorbable material dissolves, the size of the restricted inner diameter drof the restricted opening 135 gradually increases over time. When the bio-resorbable material is entirely (or substantially entirely) dissolved, the restricted inner diameter drhas increased in size to equal the stent inner diameter dsenabling unrestricted blood flow through the stent 120. That is, as the restricted inner diameter drincreases, the amount of blood flowing (blood flow amount) through the stent 120 as function of time likewise increases over time. The tissue downstream from the obstruction is therefore slowly exposed to an increasing amount of blood during reperfusion, thereby avoiding injury that would otherwise result from receiving the full amount of blood flow all at once. Generally, reperfusion injury is an inflammatory process, so it may start in a vessel walland extend to surrounding tissues over time.

[0030] As mentioned above, the device 100 is introduced into the vasculature 110 through the catheter in a collapsed (undeployed) state, so that it is able to fit efficiently through the catheter. In the collapsed state, the device 100 may be compressed and / or folded. Accordingly, more compressible bio-resorbable materials generally may be advantageous over less compressible bio-resorbable materials. Also, it may be more advantageous for the bio-resorbable layer 130 to be shorter in the longitudinal direction to further accommodate compressing and / or folding the device 100 for deployment, as discussed below.

[0031] In the depicted embodiment, the bio-resorbable layer 130 is formed of a single bioresorbable material, for purposes of illustration. The bio-resorbable material may be formed of a substantially homogenous medium, in which case it may dissolve at a uniform rate when exposed to blood flow, resulting in a substantially linear increase in the size of the restricted opening 135 over time. Alternatively, the bio-resorbable material may be formed of a substantially inhomogeneous medium, in which case it may dissolve at a non-uniform rate when exposed to blood flow, resulting in a substantially non-linear increase in the size of the restricted opening 135 over time. The type of material (e.g., homogenous or inhomogeneous) material may vary to provide unique benefits for any particular situation or to meet application specific design requirements of various implementations, as would be apparent to one skilled in the art. Further, it is understood that the bio-resorbable layer 130 may be formed of multiple bio-resorbable materials, as discussed below, without departing from the scope of the present teachings.

[0032] Referring to FIGs. 1C and ID, the restricted inner diameter drof the restricted opening 135 is shown to increase over time as the bio-resorbable material in the bio-resorbable layer 130 dissolves in response to the blood flow. In particular, FIG. 1C shows the bio-resorbable layer 130 about half dissolved and FIG. ID shows the bio-resorbable layer 130 almost completely dissolved, such that the restricted inner diameter dris substantially equal to the stent inner diameter ds. The amount of time required for the bio-resorbable layer 130 to completely dissolve depends at least in part on the type of bio-resorbable material that is used. Generally, the bio-resorbable layer 130 will dissolve over the span of multiple days for a safe rate of tissue reperfusion, although faster reperfusion may be implemented by the device 100 in a matter of hours, depending on the individual circumstances of the patient, without departing from thescope of the present teachings. The purpose is to end the period of ischemia as soon as possible, while avoiding reperfusion injury to the vasculature 110 and / or the tissue that was downstream from the obstruction.

[0033] In an embodiment, the bio-resorbable material of the bio-resorbable layer 130 may include one or more pharmaceutical agents that are released over time as the bio-resorbable material dissolves. The one or more pharmaceutical agents are configured to further limit reperfusion injury to the vasculature 110 and / or the tissue of the patient as they are released into the blood from the bi-resorbable material. Examples of such pharmaceutical agents include atrial natriuretic peptide (ANP), cydosparin-A, exenatide, and glucose insulin potassium (GIK), although other pharmaceutical agents may be included without departing from the scope of the present teachings.

[0034] In another embodiment, the bio-resorbable material of the bio-resorbable layer 130 may include a contrast medium for enhancing medical imaging, such as X-ray imaging or CT scans, for example. The contrast medium is released into the blood stream over time as the bioresorbable material dissolves. The resulting enhanced medical imaging may be used placing the stent 120 during the procedure and / or checking final placement of the stent 120, for example.

[0035] In another embodiment, the bio-resorbable material of the bio-resorbable layer 130 may include at least one biocompatible phase-changing material, such as solid-to-liquid phase changing material or liquid-to-gas phase changing material, for example. The biocompatible phase-changing material is released into the bloodstream over time as the bio-resorbable material dissolves. The biocompatible phase-changing material is configured to release sufficient energy at its phase transition to provide localized cooling, thereby causing hypothermia of the vasculature 110 of the patient as it is released. The hypothermia tends to slow the inflammation process otherwise caused by the reperfusion.

[0036] In another embodiment, the bio-resorbable material of the bio-resorbable layer 130 may be formed of a porous material. The porous material includes pores that allow blood to flow through the bio-resorbable material in addition to flowing through the restricted opening 135. The pores in the porous material increase in size over time, along with the size of the restricted inner diameter drof the restricted opening 135, as the bio-resorbable material dissolves in response to the blood flowing through the bio-resorbable layer 130. In another embodimentincluding porous material, there is no restricted opening 135 through the bio-resorbable layer 130. In this case, the blood flow amount increases through the bio-resorbable layer 130 only by virtue of the pores in the porous material increasing in size over time. The porous material will eventually dissolve entirely, enabling the blood to flow unrestricted through the full stent inner diameter dsof the stent 120.

[0037] In another embodiment, the device 100 may further include an expandable structure (not shown) embedded in the bio-resorbable layer 130 in a compressed state. The expandable structure is configured to gradually expend over time from the compressed state to an expanded (deployed) state as the bio-resorbable material of the bio-resorbable layer 130 dissolves around it, causing the expandable structure to be gradually released. As the expandable structure expands, it exerts additional force on the inner surface of the stent 120 to further increase the size of the restricted inner diameter of the restricted opening. An example of an expandable structure is provided by U.S. Patent No. 9,345,600 to Jantzen et al. (May 24, 2016), which is hereby incorporated by reference in its entirety. The expandable structure may be formed of any compatible light weight material, including metal, such as nitinol, stainless steel, platinum, gold and titanium, for example, or other material having shape memory.

[0038] FIG. 2 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including multiple sub-layers of bio-resorbable material, according to a representative embodiment.

[0039] Referring to FIG. 2, device 200 includes a stent 220 implantable in the vasculature 110 and a bio-resorbable layer 230 arranged on an inner surface of the stent 220, where the bioresorbable layer 230 includes first sub-layer 231 and second sub-layer 232 comprising different bio-resorbable materials, respectively. In the expanded state, the stent 220 has an inner surface that defines a stent opening that passes longitudinally through the stent 220 having a stent inner diameter ds. The second sub-layer 232 is formed of a second bio-resorbable material arranged on the inner surface of the stent 220 at a second predetermined thickness, and the first sub-layer 231 is formed of a first bio-resorbable material arranged on an inner surface of the second sub-layer 232 at a first predetermined thickness. The total thickness of the bio-resorbable layer 230 is thus equal to the sum of the first and second predetermined thickness.

[0040] The bio-resorbable layer 230 forms a restricted opening 235 through the stent 220 toaccommodate blood flow. The restricted opening 235 has a restricted inner diameter drthat is initially narrower than the stent inner diameter ds, and that gradually increases as the first and second sub-layers 231 and 232 dissolve in response to blood flow through the vasculature 110. In particular, the restricted inner diameter drof the restricted opening 235 is initially defined by an opening through first sub-layer 231, and increases in size as the first bio-resorbable material dissolves over time. Then, the restricted inner diameter dris defined by an opening through second sub-layer 232, and continues to increase in size as the second bio-resorbable material dissolves over time until the restricted inner diameter dris substantially equal to the stent inner diameter ds.

[0041] The first and second bio-resorbable materials may have the same or different dissolution rates. When the dissolution rates are different, the size of the restricted opening 235 increases non-linearly over time. For example, the first bio-resorbable material has a first dissolution rate that may be less than a second dissolution rate of the second bio-resorbable material. In this case, the rate at which the restricted inner diameter dr increases is slower at first in accordance with the first dissolution rate while the first sub-layer 231 is present, and then increases in accordance with the second dissolution rate once the first sub-layer 231 is completely dissolved. This may be advantageous in that the tissue is more slowly acclimated to the presence of blood at the beginning of the reperfusion process as compared to the end of the perfusion process. Of course, the second dissolution rate may be less than the first dissolution, or the first and second dissolution rates may differ by various amounts, depending on how the reperfusion is planned, in order to provide unique benefits for any particular situation or to meet application specific design requirements of various implementations, as would be apparent to one skilled in the art. Further, it understood that more than two sub-layers of the same or different bio-resorbable materials may be included in the bio-resorbable layer 230 without departing from the scope of the present teachings.

[0042] FIG. 3 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including multiple sub-layers of bio-resorbable material with separating gaps, according to a representative embodiment.

[0043] Referring to FIG. 3, device 300 is substantially the same as the device 200 in FIG. 2, except that gaps are provided between adjacent sub-layers for separating the adjacent sub-layers.That is, the device 300 includes a stent 320 implantable in the vasculature 110 and a bioresorbable layer 330 arranged on an inner surface of the stent 320, where the bio-resorbable layer 330 includes first sub-layer 331 and second sub-layer 332 comprising different bio-resorbable materials, respectively. The first and second sub-layers 331 and 332 are separated from one another by a gap 333. In the expanded state, the stent 320 has an inner surface that defines a stent opening that passes longitudinally through the stent 320 having a stent inner diameter ds. The second sub-layer 332 is formed of a second bio-resorbable material arranged on the inner surface of the stent 320 at a second predetermined thickness, and the first sub-layer 331 is formed of a first bio-resorbable material arranged on an inner surface of the second sub-layer 332 at a first predetermined thickness. The gap 333 is between the first and second sub-layers 331 and 332. The gap 333 may be an empty space or may be filled with a liquid that is released into the blood after the first sub-layer 331 (sealing layer) dissolves, as discussed below. The total thickness of the bio-resorbable layer 330 is thus equal to the sum of the first and second predetermined thickness, together with the width of the gap 333.

[0044] The bio-resorbable layer 330 forms a restricted opening 335 through the stent 320 to accommodate blood flow. The restricted opening 335 has a restricted inner diameter drthat is initially narrower than the stent inner diameter ds, and that gradually increases as the first and second sub-layers 331 and 332 dissolve in response to blood flow through the vasculature 110. In particular, the restricted inner diameter dr of the restricted opening 335 is initially defined by an opening through the first sub-layer 331, and increases in size as the first bio-resorbable material dissolves over time. The restricted inner diameter drjumps in size by a step equal to the width of the gap 333 when the first bio-resorbable material completely dissolves, increasing immediately to an opening defined by the second predetermined thickness of the second sub-layer 332. The restricted inner diameter drcontinues to increase in size as the second bio-resorbable material of the second sub-layer 332 dissolves over time until the restricted inner diameter dris substantially equal to the stent inner diameter ds.

[0045] The first and second bio-resorbable materials may be the same or different materials and may have the same or different dissolution rates. When the dissolution rates are the same, the size of the restricted opening 335 may increase linearly over time, with the exception of when the restricted opening 335 jumps in size at the gap 333. When the dissolution rates are different,the size of the restricted opening 335 increases non-linearly over time, as discussed above, including the jump in size at the gap 333. Typically, the resorbable materials (e.g., first and second sub-layers 331 and 332) dissolve slowly, limiting the way in which the blood flow amount increases over time. Inclusion of the gap 333 provides more freedom to define how the blood flow amount increases over time, enabling more optimization of how to lower reperfusion injury while restoring the blood flow.

[0046] As mentioned above, the gap 333 may be filled with liquid that is released upon dissolution of the first sub-layer 331. The liquid may contain one or more pharmaceutical agents, which are released immediately into the blood stream upon dissolution of the first sub-layer 331. As discussed above, the pharmaceutical agents may be configured to further limit reperfusion injury to the vasculature 110 and / or the tissue of the patient when coming into contact with the same. Examples of such pharmaceutical agents include ANP, cydosparin-A, exenatide, and GIK, although other pharmaceutical agents and / or other liquids having medicinal properties may be included without departing from the scope of the present teachings. Likewise, the liquid in the gap 333 may contain a contrast medium for enhancing medical imaging, such as X-ray imaging or CT scans, for example, and / or biocompatible phase-changing material for inducing hypothermia, as discussed above. When the liquid contains the pharmaceutical agents, the contrast medium, and / or the phase-changing material, they are released at larger quantities specifically when the gap 333 is exposed after dissolution of the first sub-layer 331.

[0047] As mentioned above, the device may have different shapes other than cylindrical, without departing from the scope of the present teachings. In this regard, FIG. 4 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including a bio-resorbable layer having a tapered shape, according to a representative embodiment. Referring to FIG. 4, device 400 includes a stent 420 implantable in the vasculature 110 of the patient and a bioresorbable layer 430 arranged on an inner surface of the stent 420, where the bio-resorbable layer 430 has a tapered shape.

[0048] Similar to the embodiments discussed above, the bio-resorbable layer 430 is formed of a bio-resorbable material arranged on the inner surface of the stent 420 at a predetermined thickness. The bio-resorbable layer 430 thus forms a restricted opening 435 through the stent 420 to accommodate blood flow. The restricted opening 435 has a restricted inner diameter drthat isinitially narrower than a stent inner diameter dsof the stent 420. The bio-resorbable material in the bio-resorbable layer 430 is configured to dissolve over time, such that the size of the restricted inner diameter drof the restricted opening 435 gradually increases over time. When the bio-resorbable material is entirely (or substantially entirely) dissolved, the restricted inner diameter drhas increased in size to equal the stent inner diameter dsenabling unrestricted blood flow through the stent 420.

[0049] Because of the tapered shape, the bio-resorbable layer 430 dissolves more quickly at the beginning of the reperfusion process at its more tapered end. Accordingly, the blood flow amount through the restricted opening 435 initially increases more quickly than when the bioresorbable layer 430 has dissolved down to its wider base near the inner surface of the stent 420. An advantage of this configuration is that the blood initially returns to the tissue at a faster rate to end the period of ischemia once the device 400 has been inserted and expanded, but then slows as time passes to prevent or lessen the likelihood of reperfusion injury. As the bio-resorbable material continues to dissolve, the restricted inner diameter dr of the restricted opening 435 eventually increases in size to substantially equal that of the stent inner diameter ds. The different shapes enable the user to manipulate how quickly the blood flow returns over time.

[0050] Notably, the bio-resorbable layer 430 is shorter in the longitudinal direction than the cylindrically shaped bio-resorbable layer 130 in FIGs. 1 A-1D, enabling the device 400 to be more compactible (compressible) than the device 100 when they are folded for delivery to the location of the obstruction in the vasculature 110 via the catheter. Indeed, even if the bioresorbable layer 430 and the bio-resorbable layer 130 had the same longitudinal length, the bioresorbable layer 430 would still comprise less material, again enabling the device 400 to be more compactible than the device 100.

[0051] FIG. 5 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including a bio-resorbable layer having a conical shape, according to a representative embodiment. Referring to FIG. 5, device 500 includes a stent 520 implantable in the vasculature 110 of the patient and a bio-resorbable layer 530 arranged on an inner surface of the stent 520. The bio-resorbable layer 530 has a conical shape in the longitudinal direction according to which the bio-resorbable layer 530 becomes thicker in the direction of blood flow (indicated by arrow BF). Stated differently, a restricted opening 535 defined by the bio-resorbable layer 530 toaccommodate blood flow through the stent 520 narrows in a continuous fashion in the direction of the blood flood. The restricted opening 535 has a restricted inner diameter that changes from a wide restricted inner diameter dwron the upstream side to a narrow restricted inner diameter dnr on the downstream side. The entire inner diameter through the bio-resorbable layer 530, from the wide restricted inner diameter dwrto the narrow restricted inner diameter dnr, increases over time as the bio-resorbable material dissolves until each portion reaches the same size as the stent inner diameter ds. This results in a non-linear increase in blood flow amount that is substantially exponential since the rate of increase in the blood flow amount increases more quickly as more time passes. As mentioned above, different shapes (e.g., lengths and / or slope angles of the conical shape) enable the user to manipulate how quickly the blood flow returns over time.

[0052] FIG. 6 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including a bio-resorbable layer having a stepped shape, according to a representative embodiment. Referring to FIG. 6, device 600 includes a stent 620 implantable in the vasculature 110 of the patient and a bio-resorbable layer 630 arranged on an inner surface of the stent 620. The bio-resorbable layer 630 has a stepped shape in the longitudinal direction according to which the bio-resorbable layer 630 becomes thicker in the direction of blood flow (indicated by arrow BF). Stated differently, a restricted opening 635 defined by the bio-resorbable layer 630 to accommodate blood flow through the stent 620 narrows in a stepped fashion in the direction of the blood flood.

[0053] In the depicted embodiment, the bio-resorbable layer 630 includes three representative steps for purposes of illustration. It is understood that more or fewer steps may be included without departing from the scope of the present teachings. The restricted opening 635 has a restricted inner diameter that includes a first (wide) restricted inner diameter drion the upstream side defined by a first step, a third (narrow) restricted inner diameter dr3 on the downstream side defined by a third step, and a second (intermediate) restricted inner diameter dr2 in between the upstream side and the downstream side defined by a second step. The entire inner diameter through the bio-resorbable layer 630, from the first restricted inner diameter drito the third restricted inner diameter dr3, increases over time as the bio-resorbable material dissolves until each stepped portion reaches the same size as the stent inner diameter ds. This results in a non-linear increase in blood flow amount that is substantially exponential since the rate ofincrease in the blood flow amount increases more quickly as more time passes. As mentioned above, different shapes (e.g., lengths, heights and / or number of steps in the stepped shape) enable the user to manipulate how quickly the blood flow returns over time.

[0054] In each of the previous embodiments described with reference to FIGs. 1 A-6, the bioresorbable layer (and sub-layers, if included) has a rotationally symmetrical shape, meaning that the bio-resorbable layer is substantially the same in the longitudinal cross-section on both sides of the restricted opening. Generally, the rotationally symmetrical shapes simplify the manufacturing process, and are more predictable with regard to how dissolution of the bioresorbable material occurs over time in response to blood flow.

[0055] However, in alternative embodiments, the bio-resorbable layer (and sub-layers, if included) may have a rotationally asymmetrical shape, meaning that the bio-resorbable layer is different in the longitudinal cross-section on both sides of the restricted opening. Such rotationally asymmetrical shapes may result from the restricted opening being positioned off center, for example. In more complex designs, the rotationally asymmetrical shapes may result from an irregular and / or serpentine design that is not mirrored on both sides of the restricted opening. For example, the off-center position of the restricted opening may change as a function of position in the longitudinal direction, causing the blood flow through the restricted opening to acquire a velocity component in the direction perpendicular to the blood vessel. That is, such rotationally asymmetrical shapes generally force the blood flow to have a rotational component, which slows down the blood flow. This is because blood molecules in the blood stream must constantly turn, thereby converting part of the forward velocity into a rotational component, resulting in a lower forward velocity and thus reduced blood flow. In an embodiment that includes a bio-resorbable layer formed of porous bioresorbable material, discussed above, the bio-resorbable layer may include multiple channels corresponding to rotationally asymmetrically shaped restricted openings.

[0056] FIG. 7 is a longitudinal cross-sectional view of a device for controlling reperfusion of tissue including a bio-resorbable layer having a rotationally asymmetrical shape, according to a representative embodiment. Referring to FIG. 7, device 700 includes a stent 720 implantable in the vasculature 110 of the patient and a bio-resorbable layer 730 arranged on an inner surface of the stent 720. The bio-resorbable layer 730 has a rotationally asymmetrical shape in thelongitudinal direction according to which a restricted opening 735 defined by the bio-resorbable layer 730 to accommodate blood flow through the stent 720 has a substantially serpentine shape, as discussed above. FIG. 7 also shows latitudinal cross-sectional views of the device 700 at positions A and B along the stent 720. As shown, in the depicted embodiment, the restricted opening 735 is closer to the bottom wall of the stent 720 in position A and closer to the top wall of the stent 720 in position B as a function of the rotationally asymmetrical shape of the bioresorbable layer 730. As in the previous, rotationally symmetrical embodiments, the restricted opening 735 gradually widens as the bio-resorbable material in the bio-resorbable layer 730 dissolves in response to the blood flow, thereby increasing the blood flow amount over time.

[0057] Although each of the bio-resorbable layers 430, 530, 630 and 730 are depicted as including a single layer of bio-resorbable material, it is understood that the bio-resorbable layers 430, 530, 630 and 730 may include multiple sub-layers of bio-resorbable materials, as discussed above with reference to FIGs. 2 and 3, for example. Further, the bio-resorbable material of the bio-resorbable layers 430, 530, 630 and 730 may include one or more of pharmaceutical agent(s) for further mitigating or preventing reperfusion injury to the vasculature 110 and / or the tissue of the patient, a contrast medium for enhancing medical imaging, and / or biocompatible phasechanging material for inducing hypothermia in the tissue, for example, as discussed above with reference to FIGs. 1A and IB. Also, the bio-resorbable material of the bio-resorbable layers 430, 530, 630 and 730 may be porous material including pores that allow blood to flow through the bio-resorbable material in addition to flowing through the restricted openings, also discussed above with reference to FIGs. 1 A and IB.

[0058] With regard to the bio-resorbable materials of the various bio-resorbable layers and sub-layers discussed above, there are generally four types or classes bio-resorbable materials that may be incorporated.

[0059] A first type of bio-resorbable materials includes those currently used in resorbable stents, examples of which are described by Forrestal et al., “Bioresorbable Scaffolds: Current Technology and Future Perspectives,” Rambam Maimonides Medical Journal, Vol. 11, Issue 2 (April 2020), pp. 1-9, which is hereby specifically incorporated by reference in its entirety. These bio-resorbable materials include poly-L-lactic acid (PLLA), poly-D,L-lactic acid (PDLLA), and desaminotyrosine polycarbonate.

[0060] A second type of bio-resorbable materials includes biodegradable constraining element, examples of which are identified by U.S. Patent No. 6,878,160, which is hereby specifically incorporated by reference in its entirety. These bio-resorbable materials include polymers, copolymers, block polymers and combinations thereof. Useful polymers or polymer classes, in particular, include poly(glycolic acid) (PGA), poly(lactic acid)(PLA) and combinations and copolymers thereof, for example. Other useful polymers include polydioxanones, polyoxalates, poly(a-esters), polyanhydrides, polyacetates, polycaprolactones, poly(orthoesters), stereopolymers ofL- and D-lactic acid, copolymers of bis(p-carboxyphenoxy) propane acid and sebacic acid, sebacic acid copolymers of a-amino acids, copolymers of a- amino acids and caproic acid, copolymers of a-benzyl glutamate and polyethylene glycol, copolymers of succinate and poly(glycols), polyphosphazene, polyhydroxy-alkanoates and mixtures thereof, for example, as well as additional materials of biodegradable constraining elements identified therein.

[0061] A third type of bio-resorbable materials includes resorbable suture materials, examples of which are identified by King et al., Biotextiles as Medical Implants (Woodhead Publishing Ltd 2013), Chapter 10 (by CC Chu), which is hereby specifically incorporated by reference in its entirety. The absorbable suture materials include catgut (collagen derived from sheep intestinal submucosa), reconstituted collagen, polyglycolide (e.g., Dexon®, Dexon II®, Dexon S®), poly(glycolide / lactide) random copolymer (e.g., Vicryl®), antimicrobial-coated Vicryl® (Vicryl Plus®), poly-p-dioxanone (e.g., PDS®, PDSII® PDS Plus), poly(glycolide / trimethylene carbonate) block copolymer (e.g., Maxon®), poly(glycolide / s- caprolactone) (e.g., Monocryl®, Monocryl Plus), and poly(gycolide / p-dioxanone / trimethylene carbonate) triblock copolymer (e.g., Biosyn®), poly(glycolide / £-caprolactone / trimethylene carbonate) triblock copolymer (Monosyn®), poly(glycolide / L-lactide / £- caprolactone / trimethylene carbonate) teriblock copolymer (Caprosyn®), and 100% poly-L-lact ide (Orthodek®).

[0062] A fourth type of bio-resorbable materials includes bio-resorbable substrate materials, examples of which are identified by Singh, “A Review of Bioresorbable Implantable Medical Devices: Materials, Fabrication, and Implementation,” Adv. Healthcare Mater. 9 (2020), which is hereby specifically incorporated by reference in its entirety. These bio-resorbable materialsinclude porous silicon (Si), cellulose, chitosan, peptides, chitin, silk, Dextran-base hydrogel, poly(lactic-co-glycolic acid) (PLGA), poly(vinyl alcohol) (PVA), polyglycolide or poly(glycolic acid) (PGA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), desaminotyrosyl ethyl tyrosine polycarbonate (DTE carbonate), poly(ethylene oxide) (PEO), poly octanediol-co-citrate (POC), and polyphenylene sulfide (PPS), for example.

[0063] The designs of the stents vary to provide unique benefits for any particular situation or to meet application specific design requirements of various implementations. For example, a coronary stent may have a diameter of about 3 mm and a length of about 15 mm, and the bioresorbable layer may have a cylindrical shape (e.g., as in FIGs. 1 A-1D) defining a restricted opening that initially may be about 30 percent to about 70 percent of the stent diameter, for example. The thickness of the bio-resorbable layer may be determined based on the desired length of time before the stent is to be fully opened (i.e., the bio-resorbable layer is fully dissolved), allowing unobstructed blood flow, and the dissolution properties of the bioresorbable material(s) used. For example, a bio-resorbable material that dissolves at a slower rate may be provided in a thinner and / or longitudinally shorter bio-resorbable layer to achieve the same outcome as a thicker and / or longitudinally longer bio-resorbable layer of bio-resorbable material that dissolves at a faster rate. Gaps between sub-layers and / or porous bio-resorbable material in the bio-resorbable layer may be included to further speed up the opening process, as discussed above.

[0064] FIG. 8 is a flow diagram of a method for controlling reperfusion of tissue to avoid damage to the tissue following removal of an obstruction in vasculature of a patient, according to a representative embodiment. The method is implemented by a device including a stent having a bio-resorbable layer formed of bio-resorbable material on an inner surface of the stent, embodiments of which are discussed above. The bio-resorbable layer defines a restricted opening through the stent by predetermined thickness of the bio-resorbable material. The restricted opening has a restricted inner diameter that is initially narrower than a stent inner diameter of a stent opening defined by the inner surface of the stent.

[0065] Referring to FIG. 8, the stent containing the bio-resorbable layer is inserted in a vasculature of a patient in block S811. The stent may be inserted through a catheter using a guide wire, for example. The stent is in a collapsed (un-deployed) state during the insertion procedure.To insert the stent, a distal tip of the catheter is navigated to the site of the obstruction.

[0066] In block S812, the stent is deployed from the catheter at the site of the obstruction, expanding within the vasculature to remove the obstruction. Once expanded, the stent allows blood flow to begin through the restricted opening of the bio-resorbable layer.

[0067] In block S813, the bio-resorbable material in the bio-resorbable layer dissolves over time in response to the blood flowing through the restricted opening through bio-resorbable layer, causing the restricted opening to widen over time. Eventually, bio-resorbable material is entirely (or nearly entirely) dissolved, such that the restricted opening is the same size as the stent opening, enabling unrestricted blood flow through the stent. The gradual increase in blood flow amount resulting from the controlled increase of the restricted opening prevent reperfusion injury of the tissue that was downstream from the obstruction.

[0068] In block S814, additional material optionally may be released into the blood stream as the bio-resorbable material dissolves. Such additional material may include pharmaceutical agents for mitigating or preventing additional injury to the tissue, contrast media for enhancing medical imaging, and / or biocompatible phase-changing material for inducing hypothermia in the tissue, for example. The additional material may be incorporated into the bio-resorbable material and released as the bio-resorbable material dissolves. Or, the additional material may be incorporated into liquid contained in gaps between sub-layers of bio-resorbable materials and released with the liquid as the bio-resorbable material in the containing sub-layer dissolves.

[0069] Although the present specification describes components and functions that may be implemented in particular embodiments with reference to particular standards and protocols, the disclosure is not limited to such standards and protocols. Such standards are periodically superseded by more efficient equivalents having essentially the same functions. Accordingly, replacement standards and protocols having the same or similar functions are considered equivalents thereof.

[0070] The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to serve as a complete description of all of the elements and features of the disclosure described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the disclosure. Other embodiments may be utilized and derived from the disclosure,such that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. Additionally, the illustrations are merely representational and may not be drawn to scale. Certain proportions within the illustrations may be exaggerated, while other proportions may be minimized. Accordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive.

[0071] One or more embodiments of the disclosure may be referred to herein, individually and / or collectively, by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any particular invention or inventive concept. Moreover, although specific embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the description.

[0072] The Abstract of the Disclosure is provided to comply with 37 C.F.R. § 1.72(b) and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all of the features of any of the disclosed embodiments. Thus, the following claims are incorporated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter.

[0073] The preceding description of the disclosed embodiments is provided to enable any person skilled in the art to practice the concepts described in the present disclosure. As such, 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 which fall within the true spirit and scope of the present disclosure. Thus, to the maximum extent allowed by law, the scope of the present disclosure is to be determined by thebroadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description. 1

Claims

CLAIMS:

1. A device (100, 200, 300, 400, 500, 600, 700) for controlling reperfusion of tissue to avoid damage to the tissue, the device comprising: a stent (120, 220, 320, 420, 520, 620, 720) implantable in a vasculature (110) of a patient, the stent having an inner surface that defines a stent opening through the stent having a stent inner diameter; and a bio-resorbable layer (130, 230, 330, 430, 530, 630, 730) arranged on the inner surface of the stent at a predetermined thickness forming a restricted opening (135, 235, 335, 435, 535, 635, 735) through the stent to accommodate blood flow of blood, wherein the restricted opening has a restricted inner diameter that is initially narrower than the stent inner diameter, wherein the bio-resorbable layer comprises at least one bio-resorbable material configured to dissolve over time causing a size of the restricted inner diameter of the restricted opening to gradually increase over time, enabling an amount of blood flowing through the stent to increase as the restricted inner diameter of the restricted opening increases.

2. The device of claim 1, wherein the restricted opening through the stent formed by the bio-resorbable layer has a cylindrical shape, resulting in a substantially linear increase in the size of the restricted inner diameter as the at least one bio-resorbable material dissolves over time.

3. The device of claim 1, wherein the restricted opening through the stent formed by the bio-resorbable layer has a conical shape, resulting in a substantially nonlinear increase in the size of the restricted inner diameter as the at least one bio-resorbable material dissolves over time.

4. The device of claim 1, wherein the restricted opening through the stent formed by the bio-resorbable layer has a stepped shape, resulting in a substantially nonlinear increase in the size of the restricted inner diameter as the at least one bio-resorbable material dissolves over time.

5. The device of claim 1, wherein the restricted opening through the stent formed by the bio-resorbable layer has a rotationally asymmetrical shape.

6. The device of claim 1, wherein the bio-resorbable layer comprises a plurality of sublayers separated by gaps, wherein as the at least one bio-resorbable material of the plurality of sub-layers dissolves over time, the restricted inner diameter increases by steps equal to widths of the gaps, respectively.

7. The device of claim 6, wherein the gaps are filled with a liquid that flows through the vasculature when released by the dissolving of the plurality of sub-layers.

8. The device of claim 1, wherein the bio-resorbable layer comprises a plurality of sublayers, and the at least one bio-resorbable material comprises a plurality of different bioresorbable materials of which the plurality of sub-layers are formed, respectively, wherein the plurality of sub-layers dissolve at different rates over time according to characteristics of the plurality of different bio-resorbable materials.

9. The device of claim 1, wherein the at least one bio-resorbable material comprises a porous bio-resorbable material, wherein sizes of pores in the porous bio-resorbable material increase over time, further enabling the blood flow through the stent to increase.

10. The device of claim 1, wherein the at least one bio-resorbable material comprises a contrast medium for X-ray imaging, wherein the contrast medium is released as the at least one bio-resorbable material dissolves over time, thereby enhancing the X-ray imaging used for placement of the stent.

11. The device of claim 1 , wherein the at least one bio-resorbable material comprises at least one of poly-L-lactic acid (PLLA), poly-D,L-lactic acid (PDLLA), or desaminotyrosine polycarbonate.

12. The device of claim 1, wherein the at least one bio-resorbable material comprises at least one of porous silicon, cellulose, chitosan, peptide, chitin, silk, Dextran-base hydrogel, poly(lactic-co-gly colic acid) (PLGA), poly(vinyl alcohol) (PVA), polyglycolide or poly(gly colic acid) (PGA), poly(3-hydroxybutyrate-co-3 -hydroxy valerate) (PHBV), desaminotyrosyl ethyl tyrosine polycarbonate (DTE carbonate), poly(ethylene oxide) (PEO), poly octanediol-co-citrate (POC), or polyphenylene sulfide (PPS).

13. The device of claim 1, wherein the at least one bio-resorbable material comprises at least one pharmaceutical agent that is released over time as the at least one bio-resorbable material dissolves, wherein the at least one pharmaceutical agent is configured to limit reperfusion injury to the vasculature of the patient as the at least one pharmaceutical agent is released.

14. The device of claim 13, wherein the at least one pharmaceutical agent comprises at least one of atrial natriuretic peptide (ANP), cydosparin-A, exenatide, or glucose insulin potassium (GIK).

15. The device of claim 1, wherein the at least one bio-resorbable material comprises at least one biocompatible phase-changing material that is released over time as the at least one bio-resorbable material dissolves, wherein the at least one biocompatible phase-changing material is configured cause hypothermia of the vasculature of the patient as the at least one biocompatible phase-changing material is released.

16. The device of claim 1, further comprising: an expandable metal structure embedded in the bio-resorbable layer formed on the inner surface of the stent, wherein the expandable metal structure is configured to gradually expend as the at least one bio-resorbable material of the bio-resorbable layer dissolves over time, causing the expandable metal structure to exert additional force on the inner surface of the stent to further increase the size of the restricted inner diameter of the restricted opening.

17. The device of claim 1, wherein the at least one bio-resorbable material is compressible.

18. A method for controlling reperfusion of tissue to avoid damage to the tissue implemented by a device including a stent having a bio-resorbable layer formed of bioresorbable material on an inner surface of the stent, wherein the bio-resorbable layer defines a restricted opening through the stent by predetermined thickness of the bio-resorbable material, the restricted opening having a restricted inner diameter that is initially narrower than a stent inner diameter of a stent opening defined by the inner surface of the stent, the method comprising: inserting the stent in a vasculature of a patient using a catheter to accommodate blood flow of blood through the vasculature (S811); deploying the stent through the catheter at a site of an obstruction, wherein the stent expands within the vasculature to remove the obstruction and to allow blood flow to begin through the restricted opening of the bio-resorbable layer (S812); and dissolving the bio-resorbable material in the bio-resorbable layer over time in response to the blood flowing through the restricted opening through bio-resorbable layer, causing the restricted opening to widen over time until the restricted opening is substantially the same size as the stent opening, enabling unrestricted blood flow through the stent (S813).

19. The method of claim 18, wherein the bio-resorbable material comprises at least one pharmaceutical agent, the method further comprising: releasing the at least one pharmaceutical agent into the blood of the vasculature as the bio-resorbable material dissolves to further limit reperfusion injury to the vasculature of the patient.

20. A device for controlling reperfusion of tissue to avoid damage to the tissue, the device comprising: a stent implantable in a vasculature of a patient, the stent having an inner surface that defines a stent opening through the stent having a stent inner diameter; anda bio-resorbable layer arranged on the inner surface of the stent, wherein the bioresorbable layer comprises at least one porous bio-resorbable material comprising a plurality of pores enabling blood flow through the bio-resorbable layer, wherein sizes of the plurality of pores in the porous bio-resorbable material respectively increase over time in response to the blood flow, enabling an amount of blood flowing through the stent to increase as the sizes of the plurality of pores increase.

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