Abstract:
Systems and methods for treating hypertension and other maladies are implemented using an implant device that is configured with one or more coils of ribbon which form ring-like structures when deployed in a patient&#39;s vasculature and are interconnected via respective extension arms formed from at least one helical winding. In an illustrative example, the catheter is positioned in the patient&#39;s aorta near the right angle junction with renal vasculature so that the axis of the catheter is substantially perpendicular to the axis of the vasculature. Through operation of an implant device delivery system having a pigtail distal end the ribbon emerges from the catheter tip and coils into the ring-like structures which deploy into the renal vasculature so that the longitudinal axes of the device and vasculature are substantially co-linear.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims benefit of priority to U.S. Provisional Patent Application Ser. No. 61/478,960 filed Apr. 26, 2011 entitled “Method and Device for Treatment of Hypertension and Other Maladies” which is incorporated by reference herein in its entirety with the same effect as if set for at length. 
     
    
     BACKGROUND 
       [0002]    Hypertension is a common and dangerous disease and represents a significant global health issue that continues to grow. Present treatments for hypertension typically include lifestyle changes, surgical procedures such as angioplasty, and various drug therapies which can be effective in some cases. However, the overall rate of control of hypertension and the therapeutic efforts to prevent progression of related maladies such as myocardial infarction, heart failure, chronic kidney disease, and diabetic nephropathy remain unsatisfactory and new treatment options are desirable. 
         [0003]    This Background is provided to introduce a brief context for the Summary and Detailed Description that follow. This Background is not intended to be an aid in determining the scope of the claimed subject matter nor be viewed as limiting the claimed subject matter to implementations that solve any or all of the disadvantages or problems presented above. 
       SUMMARY 
       [0004]    Systems and methods for treating hypertension and other maladies are implemented using an implant device that is configured with one, two, or more coils of ribbon which form ring-like structures when deployed in a patient&#39;s vasculature and, in the case of multiple rings or sets of coils, are interconnected via respective extension arms formed from at least one helical-shaped winding. In an illustrative example, a delivery catheter is positioned in the patient&#39;s aorta near the right angle junction with renal vasculature so that the axis of the catheter is substantially perpendicular to the axis of the vasculature. Through operation of an implant device delivery system having a pigtail distal end, the ribbon emerges from the catheter tip and coils into the ring-like structures which deploy into the renal vasculature so that the longitudinal axes of the device and vasculature are substantially co-linear. 
         [0005]    In some implementations, the present systems and methods facilitate utilization of an implanted device that has an improved safety profile and which minimizes collateral damage over many current therapies. Therapy is delivered within the vessel having a focal tissue effect at the point of contact. Advantageously, no external energy source or capital investment is required for use with the implant device in many typical implementations. Methods utilized with the implant device need not directly integrate the device into the wall surface of the vessels. Rather, in an acute treatment, the implant device is designed and configured to apply and maintain radial or substantially radial force along the circumference of the vessels in which it is implanted, while employing a helical pattern of extension arms, connecting the two or more coils, each forming a ring-like structure. The radial force imparted from the implanted device is found to efficaciously block or retard sympathetic nerve communication to the kidneys which is identified as a principle contributor to the pathophysiology of hypertension, kidney disease, and heart failure. The implant device can be configured with multiple rings so that the radial force can be imparted along a target length of renal vasculature. The implant device may further be delivered using a procedure under only local anesthesia rather than requiring general anesthesia. 
         [0006]    This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  shows an illustrative renal anatomy. 
           [0008]      FIG. 2  schematically illustrates an implant device within a vessel, for example, a renal artery. 
           [0009]    FIGS.  3 (A)-(C) illustrate various views of the implant device of  FIG. 1 , with a single helix connecting two coils or rings. 
           [0010]      FIGS. 4(A)  and (B) illustrate features that may be employed in certain implementations of the implant device. 
           [0011]      FIG. 5  illustrates a feature that may be employed in certain implementations of the implant device. 
           [0012]      FIG. 6  illustrates details of a delivery device that may be employed to deliver the implant device. 
           [0013]      FIG. 7  illustrates details of the device of  FIG. 6 . 
           [0014]      FIG. 8  illustrates additional details of the device of  FIG. 6 . 
           [0015]      FIG. 9  illustrates a perspective view of the device of  FIG. 6 . 
           [0016]    FIGS.  10 (A)-(C) illustrate proximal end, distal end, and distal tip details of the device of  FIG. 6 . 
           [0017]    FIGS.  11 (A)-(C) illustrate various views of another embodiment of the implant device, illustrating how two helices or a dual helix system may be employed to connect two coils or rings. 
           [0018]      FIG. 12  illustrates removal of the implant device from a delivery device using a pusher and ratchet sleeve. 
           [0019]      FIG. 13  illustrates a ratchet sleeve that may be employed to remove the implant device from a delivery device. 
           [0020]    FIGS.  14 (A)-(D) illustrate steps in removing the implant device from one embodiment of a delivery device, where the implant device expands off a mandrel. 
           [0021]      FIGS. 15(A)  and (B) illustrate a grabber device, in both a closed and opened configuration, respectively.  FIG. 15(C)  illustrates a cutaway view of the grabber device in use within a delivery device. 
           [0022]      FIG. 16(A)  illustrates a terminal end of an implant device, showing the end which may be grabbed by a grabber associated with the delivery device, or with a retrieval device.  FIG. 16(B)  illustrates the grabber associated with the delivery device, or with a retrieval device. 
           [0023]    FIGS.  17 (A)-(D) illustrate steps in removing the implant device from another embodiment of a delivery device, where the implant device is pushed out of a tube. 
           [0024]      FIGS. 18(A)  and (B) show an illustrative anatomy of a patient&#39;s stomach. 
           [0025]      FIG. 19  illustrates a feature that may be employed in certain implementations of the implant device. 
       
    
    
       [0026]    Like reference numerals refer to like elements throughout. Elements are not drawn to scale unless otherwise indicated. 
       DETAILED DESCRIPTION 
       [0027]    In some implementations, as described below, a ring system implant device as disclosed may be deployed in the renal vessels for the treatment of hypertension or diabetes. In particular, renal artery stenosis (“RAS”), or narrowing of one or both renal arteries, may lead to hypertension as the affected kidneys release renin to increase blood pressure to preserve perfusion to the kidneys. In the past, RAS was treated with the use of balloon angioplasty and stents, if necessary. However, the ring design as disclosed above may also be deployed in the renal arteries to treat RAS. 
         [0028]    In this implementation, advantage may be taken of a delivery mechanism of even simpler design. In particular, if the ring system implant device is uncoiled and arranged in a delivery catheter or sheath in a substantially linear configuration, then upon deployment, the axis of the ring system will tend to be perpendicular to the axis of the catheter. Such a system is very desirable in a deployment in the renal vessels. 
         [0029]    The renal anatomy  200  is illustrated in  FIG. 1 . As may be seen, a catheter deployed in the aorta  202  meets the renal arteries  205  and  210  at an angle approaching 90°. A ring system implant device emerging from the tip of the catheter having a longitudinal axis perpendicular to that of the catheter would be nearly substantially in proper position for delivery of therapy. Access to the renal arteries  205  and  210  may be gained via a catheter deployed from the femoral artery, as well as by other means. It is believed that the implant device would generally be installed at a location about ½ to ⅔rds of the distance into the renal artery, each of which is about 4 to 5 cm long.  FIG. 1  also depicts a functional representation of the pathway between the renal anatomy  200  and the brain  215  with a system of renal afferent nerves  220  and renal efferent nerves  225 , as well as a pathway with renal afferent nerves  230  between the kidneys  235  and  240 . 
         [0030]    Using the ring system implant device in this way, as well as in others, the implant device may confer a downstream neurological benefit as well as a cellular or electrical benefit. The delivery system for an implant device in the renal arteries would not necessarily require electrodes or other mapping devices on the delivery system in typical implementations. 
         [0031]    Ring Details In one implementation, the implant device may include two or more separated rings that are connected by a single helical wire, a double helical wire, or a set of multiple helical wires. An exemplary implant device  100 , in place within a renal vessel, is illustrated schematically in FIGS.  2  and  3 (A)-(C). The implant device  100  includes a proximal ring  10  and a distal ring  30 , which are separated by a helix or helical wind  20 . FIGS.  3 (A)-(C) illustrate various views of the implant device  100 , where a single helical wind is employed between the proximal and distal rings.  FIGS. 11(A)-11(C)  illustrate various alternative exemplary implant devices  100 , including those employing double helical arms or winds  20  between the distal ring  30  and proximal ring  10  of the implant device. 
         [0032]    The diameter of the undeployed rings may be about 4 mm to 60 mm for the proximal ring, and about 6 mm to 60 mm for the distal ring. The diameter of the deployed rings may be about 2 mm to 40 mm for the proximal ring, and about 3 mm to 40 mm for the distal ring. The rings may be configured in a symmetrical pattern, for example, the diameter of the distal ring may be substantially equal to the diameter of the proximal ring. Alternatively, an asymmetric pattern may be employed having one end of the ring larger or smaller than the other end, for example, a distal end may have a 10 mm diameter while the proximal end may have a larger 25 mm diameter. 
         [0033]    The size of the rings within a particular implant device can vary. For example, the diameter of each subsequent ring in a two-ring device may decrease in a distal direction. In some implementations, a distal ring may employ coils having a common diameter, while the proximal ring may employ coils having a decreasing diameter (decreasing in the distal direction). 
         [0034]    The rings may be designed to deliver a force against the tissue of between about 5 g/mm 2  and 340 g/mm 2 , for example, between about 20 g/mm 2  and 200 g/mm 2 . The distal ring may provide a greater amount of force than the proximal one. Implant devices may be efficacious when configured to deliver a pressure of between about 0.01 to 0.20 N/mm 2  in a cylinder or vessel sized from 10 to 25 mm. More specifically, for smaller diameters, pressures may be from about 0.07 to 0.20 N/mm 2 ; for intermediate diameters, 0.03 to 0.05; and for larger diameters, 0.01 to 0.08. The overall force delivered to the vessel may be between about 1 to 9 N for a 15×15 device, 0.2 to 8 N for a 20×20 device, 0.3 to 7 N for a 25×25 device, and 1 to 5 N for a 30×30 device, although it will be understood that these values may vary with the size of the implant device, including the thickness of the ribbon. Typical values found appropriate are from 0.2 to 10 N, in particular 0.3 to 6 N. In tests, implanting intermediate sized devices (e.g., 27 mm diameter devices in a 19 mm vessel) resulted in the vessel extending to about 23 mm. Similar percentage increases may be expected for other size devices. 
         [0035]    It is believed that the amount of pressure necessary should be more than 10 g/mm 2 , for example, greater than 20 g/mm2, but less than 340 g/mm2, for example less than 200 g/mm2, as noted above. While it may be desirable to have the rings and helices exert a relatively constant force about the circumference of the vasculature, it is more likely given anatomical imperfections, that certain areas will receive more pressure than others. However, compliance of the rings and use of the helix helps to distribute forces around the implant device. In general, it is believed that the amount of pressure needed will primarily be a function of the material used, the diameter of the vasculature, and the thickness of the associated muscle sleeve. 
         [0036]    One or more of the helices may revolve around a central axis  1 , 1.5, or more times. In this way, even when placed in larger vessels, the available expansion room may cause an effective pressure block to be achieved. However, in this regard, it is noted that radial force decreases dramatically as the radius increases. 
         [0037]    For implant devices made from ribbon wires, exemplary values of the ribbon width may be, for example, 1 to 2 mm, and between 0.5 and 2.5 mm. For coverage of greater portions of the renal vasculature, as may be appropriate for greater nerve coverage and thus denervation, the ribbon width may be made significantly wider, e.g., 5, 7, 10 mm, as well as other values. The overall length would likewise be greater, e.g., 1-4 or 5 cm overall. 
         [0038]    To ensure a minimum of migration, the ends of the wire or ribbon forming the ring system may be scalloped or have another shape to increase frictional or mechanical resistance against movement. Such shapes are illustrated in  FIGS. 4(A) and 4(B) . In  FIG. 4(A) , a distal end  24  includes scallops or ribs  26 , while in  FIG. 4(B) , the distal end  28  includes smaller but more frequent scallops or ribs  32 . In addition, the external surface of the implant device  100  may have a textured surface, or may include a polymer sleeve, or a combination of the two, to further aid the device in fixation of the vessel. The polymer sleeve may also include a microcircuit to wirelessly enable electric rim interpretation during and after the procedure. Furthermore, a coating or biological agent of the implant surface may be employed to further reduce migration and/or erosion of the implant device. 
         [0039]    Referring to  FIG. 5 , a distal end  34  of the wire or ribbon may further include a club shape  36  so as to minimize the chance of perforation. The hole in the club-shaped end may be employed to allow two implant devices to be attached to each other. In this way, multiple implant devices may be loaded into a delivery system to allow multiple installations in a single procedure. The implant devices may be attached end-to-end in a way akin to staples or railcars. 
         [0040]    Deployment The implant device may be deployed in various ways. In one implementation, illustrated in  FIGS. 6-9 , a delivery catheter  12  has a handle  64  for steerability and a knob  68  to control a pusher  72 , for example, a flexible wire or elongated spring, at a proximal end. At a distal end, the delivery catheter may have a PeBax® (or other material) loop or pigtail  62 . As shown in detail in  FIG. 7 , the pusher with a tip  76  extends through the delivery catheter  12 , and the same is attached to an implant device  100  at a point within the catheter. The implant device  100  is uncoiled in this undeployed configuration, and the implant device may extend through the pigtail  62  and may further extend a short distance from the distal end of the pigtail during deployment. The distal end of the delivery system may also include a design where the catheter distal end is in a straight or neutral position and then steered using knobs and/or levers on the handle to create the pigtail distal segment. Another lever located on the handle may be employed to deflect or steer the distal segment for cannulation of each vessel. 
         [0041]    By pushing the implant device out of the distal end of the catheter, shown in more detail in  FIG. 7 , the same may take up a position within the renal vessel as desired. One purpose of the PeBax pigtail is to protect the vessel during deployment in the same way that, for example, a Lasso® catheter does. In addition, it is noted that certain PeBax pigtails may be equipped with electrodes  16  for various purposes, as shown in  FIGS. 6 ,  8 , and  9 . For example, selective electrode activation may be employed to ablate desired tissue to further enhance the efficacy of renal denervation provided by the implant device through application of heat or RF (radio frequency) emissions. Alternatively, instead of ablating the tissue with elevated temperatures, the pigtail may be adapted to deliver low temperatures via cryothermia therapy. The implant device may also be adapted to deliver thermal energy to selected tissue portions through inductive heating. The pitch of the distal loop or pigtail may be altered in a known manner, for example, by a control wire, to allow different geometries to be accommodated.  FIG. 6  also illustrates element  66 , which along with elements  74  and  76  of  FIG. 10(A)  may constitute Tuohy-Borst hemostasis valves or adaptors. 
         [0042]    Referring to  FIG. 8 , a rectangular lumen  82  may be employed to contain and deliver the implant device. In addition, it will be understood that more than one rectangular or circular lumen may be employed, and their shapes may differ, according to the needs of any given catheter design, such as an oval lumen  86 , as shown. In systems where the catheter is made fully steerable or deflectable, additional lumens  84  may be employed to provide the necessary control wires for steering or deflection. 
         [0043]      FIGS. 10(A)-10(C)  illustrate a related embodiment, as well as various construction and manufacture details of a specific exemplary version. In these figures, a handle  64  includes a knob  68  which is separated by a distance L 72 . The distance L 72  is chosen to allow for complete deployment of the implant device. A layer of epoxy  112  may seal the handle  64  to the sheath. Referring to  FIG. 10(B) , the sheath  98  is seen to terminate at a distal end at a distal end bushing  88 . A hypo stock sleeve  86  surrounds a layer of epoxy  84  which is used to hold a NiTi tension band  82 . The distal end bushing is coupled to the sheath  98  by a layer of epoxy  92 . Referring to  FIG. 10(C) , greater detail is shown of the distal tip. In particular, a distal end of the NiTi tension band terminates at a hypotube  104  and is held in place by a layer of epoxy  106 . A heat shrink  102  is set around the assembly. 
         [0044]    In a related implementation, as seen in  FIGS. 12 and 13 , the system may employ a small device, for example a ratchet sleeve having a cylinder  48  and extension  46  within the delivery catheter or sheath that can provide a ratcheting function. In this way, the handle may be simplified, and provided with greater control, by having the operator only have to provide a repeated short-stroke motion to controllably cause the implant device to exit the sheath and become implanted in the renal vessel. 
         [0045]    The ratchet or ratcheting mechanism is shown in greater detail in  FIG. 13  (not to scale). In particular, the ratchet sleeve is disposed within the sheath (it is exterior of the sheath for illustrative purposes in  FIG. 12 ). Once the implant device is pulled back into the sheath, and the ratchet sleeve is disposed near the distal tip of the sheath, then the implant device may be deployed by repeatedly pushing it out of the tip, for example, a fraction of a centimeter, such as ¼ centimeter, to 2 inches, at a time. The implant device is prohibited against retracting into the sheath by virtue of the ratchet sleeve. 
         [0046]    In a further related embodiment, a small balloon may be inflated within the ratchet sleeve if desired to provide a way for the ratchet sleeve to grab onto the implant device. By placing a tip of the implant device, for example, the proximal tip, into the ratchet sleeve, and inflating the balloon to fill up the interstitial space, the implant device may be effectively grabbed by being held between the balloon and the wall of the ratchet sleeve. In another embodiment, the inflation lumen and balloon may be provided in the pusher, and the device may be grabbed by inserting the pusher into the ratchet sleeve and inflating the balloon, thereby constricting the implant device tip in the same small diameter as the balloon (within the ratchet sleeve), causing the same to be grabbed. In yet another embodiment, a small balloon may be employed to render the volume within the ratchet sleeve closed, and in that case a small negative pressure may be pulled on the interior of the ratchet sleeve, constricting its walls and causing the same to pull inwards, grabbing onto the implant device in the process. 
         [0047]    In an alternative implementation, illustrated in  FIGS. 14(A)-14(C) , the implant device  100  is coiled around a threaded mandrel  144  and confined by an outer tube  146 . Removal of the outer tube allows the implanted device to spring away from the mandrel by virtue of its shape-memory character.  FIGS. 14(A)-14(C)  illustrate a sequence of deployment steps. In general, removing the outer tube causes immediate deployment, resulting in impingement of the device  100  against a vessel wall  142 . 
         [0048]    To deploy the distal end first, a split catheter shaft may be employed, such that separation of the catheter shaft at a location near the distal end causes the distal end to be deployed first. Of course, in certain implementations, the proximal end may also be deployed first. Such a split catheter shaft may be employed, for example, in the delivery of the implant device shown in  FIGS. 14(A)-14(C) . In this implementation, the distal end of the catheter may employ a polymer tip for atraumatic delivery, and the polymer tip may be radiopaque. As in most of the implementations described, the catheter may be delivered over a guide wire. 
         [0049]    In another implementation, the distal end of the implant device is sutured to the catheter, and the wire of the device is wrapped around the catheter. In this connection it is noted that the implant device, during delivery, undeployed and constrained in a delivery device, may take the form of a straight wire, a helically-wrapped wire, or another configuration. The sutured end causes the distal end to be deployed last, and the final separation of the distal end from the catheter may be effected by way of cutting using a blade configured for that purpose, an electrical arc, or the like. 
         [0050]    Referring to  FIG. 16 , the implant device  100  may also be held by the catheter by a grabber or grip  130 , for example, a toothed grip. In particular, laser (or other) cuts  126  and  128  may be made in a distal cylindrical catheter tip to form a mouth or grip which may grab the proximal end of the implant device. In the figures, the laser cuts are made radially or longitudinally to the cylindrical axis of the grabber. It will be understood that curved cuts may also be employed, according to the needs of the particular application. The cuts allow bending or flexing away from the remainder  132  of the grabber or grabbing device  130 . The mouth or grip may be configured, for example, via heat treatment (e.g., using a memory metal such as nitinol) or design or both, to distend or open when the mouth or grip is not confined by the sheath tube. Once the same is thus extended away from the sheath  96 , the same may open and release the implant device  100 . 
         [0051]    In a related implementation, the implant device may be formed with a groove between elements  114  and  116  (see  FIG. 16(A) ) or other feature to allow the grabber device  130  to hold the same in a secure and/or locked fashion. Similarly, the grabber device may have formed thereon a “tooth”  111  between upper half  118  and lower half  122  to allow additional points of contact (see  FIG. 16(B) ). 
         [0052]    Additional views are also shown in FIGS.  15 (A)-(C). In  FIG. 15(C) , a cutaway view of the grabbing device  130  is shown attached to a pusher  134  within the sheath  12 . 
         [0053]    In any case, when the grabbing device navigates the sheath or delivery catheter, it must navigate both curved sections and straight sections. In some systems, it may be advantageous to provide the same with a small curve or with additional laser cuts to allow the grabber device a degree of flexibility. 
         [0054]    FIGS.  17 (A)-(D) illustrate another embodiment, which deploys the implant device perpendicular to the direction of implantation of the exemplary embodiment shown in  FIGS. 14(A)-14(D) . This deployment direction may be useful in certain patient anatomies. In this embodiment, the shape-memory character of the implant device may be employed to allow the same to be delivered from the end of a straight tube. As will be seen, one ring deploys prior to the other. In some cases, it may be necessary to reposition the implant device if the same does not deploy properly directly out of the tube. In FIGS.  17 (A)-(D), the implant device  100  emerges directly (and initially linearly) out of the distal tip of the catheter  192 . In FIGS.  17 (A)-(D), the distal ring  30  emerges first, followed by the proximal ring  10 , though it will be understood that the order may be reversed. 
         [0055]    In general, the delivery system will have distal and proximal ends, where the distal end employs an atraumatic distal tip and the proximal end includes a handle. The system further includes a catheter shaft having a tubular structure traversing from the proximal end to the distal end. The guide wire lumen includes a luminal space to enable passage of a range of guide wire sizes. In one implementation, the guide wire lumen is further capable of being advanced distally or proximally to enable deployment of the ring-like coil implant device attached along the external surface of the guide wire lumen and contained within the inner surface of the outer catheter shaft. As in some embodiments above, the delivery system catheter may employ a flexible distal segment and a steering wire anchored at the distal portion of the delivery catheter. 
         [0056]    In some implementations, the deployment device, or another device, may allow a degree of recapture to occur in order to fix incorrect implanted device placements within the vessel. For example, where the device is pushed through a tube for deployment, the same two may be used to deliver a small wire equipped with maneuverable jaws at its distal end. For example, a modified guide wire may be employed. A control wire running alongside the guide wire may allow the contraction of one or more jaws in order to grab an errant device. If desired, retraction of the guide wire may then allow the complete removal of the implanted device. In the system described above where a mouth or grip is closed or opened by virtue of its being enclosed by a sheath or not, respectively, the mouth or grip may be employed to recapture an implanted device. In the same way, the ratchet sleeve with incorporated balloon may provide this function as well. 
         [0057]    In another embodiment, a similarly shaped ring system may be employed to treat diabetes in patients. The anatomy of the stomach is illustrated in  FIGS. 18(A)  and (B). Shown are the esophagus  1805 , cardia  1810 , fundus  1815 , body  1820 , antrum  1825 , pylorus  1830 , mucous glands  1835 , and duodenum  1840 .  FIG. 18(B)  also shows the antrum cadiacum  1845 , incisura angularis  1850 , pyloric part  1855 , sulcus intermedius  1860 , pyloric antrum  1865 , pyloroduodenal opening  1870 , lesser curvature  1875 , and greater curvature  1880 . It is noted that, historically, some patients who were treated for obesity using the technique of gastric bypass had a surprising benefit of being treated or even cured of their diabetes. 
         [0058]    It is believed that the placement of the ring system in a location at the lower end of the esophagus, towards the cardia, may in some cases treat diabetes in the same way. In this case, the ring system would simply be deployed down the esophagus. The ring system itself may have a larger diameter with a wider ribbon, and may deliver higher radial forces. Higher radial forces may be achieved by use of a thicker ribbon as well. 
         [0059]    In general, it is noted that any body cavity with a substantially cylindrical shape may benefit from application of the system and method disclosed, if that body cavity benefits from pressure application. 
         [0060]    Mechanism of Operation A single or dual ring system, as well as the helix or helical extension arms, may compress tissue, to cause a narrowing of certain channels within the tissue. For example, sodium, calcium, or potassium channels may be blocked by mild compression. It is believed that a suitable amount of force will result in a compression of the first one to five cellular layers in the tissue. In particular, it may be important to at least compress the first layer. 
         [0061]    It is believed that the amount of pressure necessary should be more than 10 g/mm 2  (for example, greater than 20 g/mm 2 ), but less than 340 g/mm 2  (for example, less than about 200 g/mm 2 ), as noted above. While it may be desired to have the rings and helix or helices exert a relatively constant force around the circumference of the vessel, it is more likely, given anatomical imperfections, that certain areas will receive more pressure than others. However, compliance of the ring and the use of the helix helps to distribute forces around the implant device. In general it is believed that the amount of pressure needed will primarily be a function of the material used, the diameter of the artery or vein, and the thickness of the muscle sleeve. 
         [0062]    It is also noted that the ring may cause the vessel in which it dwells to become more oval or round, or otherwise to maintain a more open shape than that which it adopted before, in the absence of the implant device. In this way, the device acts as a stent, enhancing patency, hemodynamics and the resulting blood flow. The device affects the shape of the vessel, and vice-versa. This effect improves apposition of the implant device to improve outcomes by enabling circumferential contact resulting in laminar blood flow, and can help to treat stenotic vessels. One aspect of the device that assists in this regard is the device ring compliance, which causes the device to conform to the vessel—i.e., the radial expansion helps to keep the device in place in a dynamic way. 
         [0063]    In some implementations, the metallic nature of the implanted device may be employed to provide a level of active heating so as to heat or necrose tissue adjoining the implant device. For example, such heating may be by way of induction using a device external to the patient. The device may be caused to heat the implant device and thus heat (and treat) the tissue creating localized necrosis, and then be easily removed from the vicinity of the patient to stop the heating. In advanced versions of this implementation, the heating device and the implant device may be tuned such that only one implant device is heated at a time, if multiple implant devices have been deployed. 
         [0064]    The mechanism of operation of the device, where the same is disposed in the esophagus is described above in the sections describing their deployment. 
         [0065]    Construction As will be understood, the rings and helices may be constructed of several types of materials. For example, biocompatible metals such as nitinol may be employed, and the same exhibit useful shape memory properties. Biocompatible polymers or elastomers may also be employed. 
         [0066]    The ring may employ a shoulder  18  for stability, as well as a feature  22  to cause pressure, as illustrated in  FIG. 19 . For example, the feature  22  to cause pressure may be any three-dimensional solid capable of exerting additional pressure along a predetermined area, such as a ridge. The portion of the shoulder adjacent to tissue may be roughened or otherwise treated in order to provide an irritant to that tissue, so as to cause endothelialization as discussed above. Such endothelial cells are typically not conductive, and thus act as a long-term-care modality. 
         [0067]    Coatings While not required in all implementations, various coatings or other agents may be applied or made part of the rings and/or helices, such coatings or agents capable of disrupting the propagation of aberrant electrical signals or otherwise treating arrhythmias. Such coatings may include drugs, biologics, chemicals, or combinations, that by themselves or in combination with the mechanical compression act as a treatment for hypertension. As another example, the rings and helices may be coated with tantalum, for example, a 3-5 micron coating. 
         [0068]    The implant device may be permanent, removable, or the same may be configured and designed to be absorbed into the body after a period of time. In a removable embodiment, a removable portion (which may be the entire implant device or a portion thereof) may be installed for a period of time, for example, between 30 minutes and 24 hours, and then removed. 
         [0069]    Variations Other aspects of the invention may include one or more of the following. The device may include a contiguous circumferential ring normally perpendicular to the ostium of the vessel, and the ring or coil structure may have at least one full rotation, as well as a pitch that is &gt;1° from the first ring. The ring or coil structure may provide radial support to stenosed vessels. The ring or coil structure may employ a single ring (with one or more coils or windings) or may have both a distal ring and a proximal ring. The proximal ring may employ a single extension arm or a plurality of extension arms that extend distally toward and connect to the distal ring. The extension arms may have a helical shape and may extend distally toward the distal ring. The ring or coil structure may apply mechanical pressure to tissue. The ring or coil structure may have a material composition, surface treatment, coating, or biological agent and/or drug to cause a human biological response, for example, intimal hyperplasia or endothelization, in a controlled or semi-controlled way in order to cause a desired effect. The ring or coil structure may have at least one full circumferential winding, and indeed more, and may include a helical extension moving distally from the outer diameter of the first ring and terminating within the vessel to prevent migration of the coil or ring structure. The ring or coil may be made of a round wire or ribbon profile that is shaped into a ring or coil. The ring or coil may have various cross-sectional shapes designed to focus mechanical force in a circumferential or helical pattern against the inner surface of a vessel or structure. These shapes include but are not limited to round or circular, triangular, rectangular, “U” shaped, or any number of other shape combinations. The ring or coil structure may have a material composition and/or geometry designed to sufficiently conform to tissue to prevent coagulation or thrombus, and may include a material coating to further reduce or prevent such coagulation or thrombus. The ring or coil structure may have a hexagonal, pentagonal, and/or octagonal shape when viewing in an end view. This geometric shape may be designed to improve conformability to the vessel following implantation. By changing the geometry of the loop or ring, the ring and vessel may be mutually conformed, and the radial force equalized along the circumference of the inner surface of the vessels. The ring or coil structure may have the above-noted shapes at the proximal end but may employ a circular shape at the distal end. 
         [0070]    Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.