Patent Publication Number: US-2019191964-A1

Title: Vascular force reduction system

Description:
PRIORITY CLAIM 
     This invention claims the benefit of priority of U.S. Provisional Application Ser. No. 62/610,701, entitled “Vascular Force Reduction System,” filed Dec. 27, 2017, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The present embodiments relate generally to medical devices, and more particularly, to guidewires, catheters, introducers, sheaths, and other devices used in procedures to treat diseased vessels. 
     In the field of endovascular intervention, physicians treat diseased or damaged vessels using a number of standard procedures. These procedures frequently utilize endovascular devices such as guide wires, catheters, cannulas, sheaths, balloons, stent grafts, etc. Oftentimes, physicians enter the patient&#39;s anatomy from a relatively remote location (e.g., the femoral artery), and must navigate instruments through relatively long distances in order to reach the treatment zone. The long distances and tortuous anatomy can require the physician to exert relatively large forces to manipulate the devices. 
     At the treatment zone and elsewhere, physicians routinely encounter diseased vessels, for example vessels with atherosclerosis and other occlusive diseases. In such diseases, atherosclerotic plaque forms within the walls of the vessel. In occluded areas, it may be difficult to advance or retract endovascular devices, and may be difficult to position the device on a small scale, e.g., millimeters or nanometers. Additionally, because the placement and tracking of endovascular instruments can exert pushing and friction forces against the vessel and plaque, the risk of plaque disruption and downstream embolization can be high. 
     SUMMARY 
     The disclosed embodiments relate to medical devices suitable for use in endovascular procedures. In one aspect, a system may include a medical device with a proximal end, a distal end, and a section of material therebetween. The system may also include a vascular force reduction system positioned along the section. The vascular force reduction system may have at least one support structure supporting at least one rotating assembly that may have a vessel contact surface. The rotating assembly may be configured to rotate toward the proximal and the distal ends. 
     The rotating assembly may include a bearing and/or a band, such as a band with a traction element. The rotating assembly may include a plurality of rotating elements connected by a band. The section of material of the medical device may include an endovascular device, such as a guidewire, a catheter, an introducer, a sheath, and other device. The support structure may be formed integrally to the section of material, may have a guard, and may include an aperture. The support structure may include a first support structure and a second support structure, which may have a common or different position along a length of the section of the medical device, and/or may have a common or different radial position about the section. The rotating assembly may be configured to rotate within a plane that is approximately coincident or parallel with the section. 
     In another aspect, a system may include a plurality of rotating assemblies that may be positioned upon a medical device having a section of material positioned between a proximal end and a distal end. Each rotating assembly of the plurality may have a vessel contact surface and may be configured to rotate substantially toward the proximal and the distal ends. The plurality of rotating assemblies may suspend at least a portion of the section within a core protective zone, which may be at least partially bounded by the vessel contact surface of each rotating assembly. The core protective zone may extend along the section from a location of a proximal rotating assembly to a location of a distal rotating assembly. The core protective zone may have a maximum cross sectional dimension of less than approximately 10 mm. 
     In another aspect, a method may include providing a medical device having a section of material with a proximal end and a distal end and at least one support structure positioned along the section. The support structure may support at least one rotating assembly, which may have a vessel contact surface. The method may further include rolling the vessel contact surface over a vessel wall. The method may further include suspending the section of material in a core protective zone that may be at least partially bounded by the vessel contact surface of at least one rotating assembly. 
     Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be within the scope of the invention, and be encompassed by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  is an isometric view of a vascular force reduction system-equipped guidewire traversing a plaque deposit within a vessel lumen. 
         FIG. 2  is a front view of the vascular force reduction system of  FIG. 1 . 
         FIG. 3  is a top view of the vascular force reduction system of  FIG. 1 . 
         FIG. 4  is a side view of the vascular force reduction system of  FIG. 1 . 
         FIG. 5  is an isometric view of another embodiment of a vascular force reduction system. 
         FIG. 6  is an isometric view of yet another embodiment of a vascular force reduction system. 
         FIG. 6A  is a front view of the vascular force reduction system of  FIG. 6 . 
         FIG. 7  is an isometric view of yet another embodiment of a vascular force reduction system. 
         FIG. 7A  is a front view of the vascular force reduction system of  FIG. 7 . 
         FIG. 8  is an isometric view of a vascular force reduction system-equipped catheter. 
         FIG. 9  is an isometric view of another vascular force reduction system. 
         FIG. 9A  is a front view of the vascular force reduction system of  FIG. 9 . 
         FIG. 10  is an isometric view of yet another vascular force reduction system. 
         FIG. 10A  is a front view of the vascular force reduction system of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the present application, the term “proximal” refers to a direction that is generally closest to the heart, while the term “distal” refers to a direction that is generally furthest from the heart. The embodiments below are described in connection with endovascular aortic repair procedures, but could also be used for other procedures. 
     The aorta is the largest artery in the human body and carries blood away from the heart. The size of the aorta normally decreases with distance from the aortic valve in a tapering fashion. The normal diameter of the ascending aorta has been defined as about 21 mm and of the descending aorta as about 16 mm, while the normal diameter of the abdominal aorta is regarded to be less than 30 mm, although the normal range may vary based upon age and sex, as well as daily workload. Raimund Erbel and Holger Eggebrecht,  Aortic Dimensions and the Risk of Dissection,  92 Heart Journal 137 (2006). The aortic arch is located distally to the ascending aorta and proximal to the descending aorta. The aortic root is the section of the aorta closest to the heart, and includes the aortic valve and coronary ostia. The right coronary artery and left coronary artery are peripheral vessels in the ascending aorta and circulate blood to the heart tissue itself. Other peripheral vessels near the aortic arch include the brachiocephalic artery, right subclavian artery, right common carotid artery, left common carotid artery, and left subclavian artery. From the aortic arch, the descending aorta continues downward toward the lower limbs. The thoracic aorta is the segment of the descending aorta extending from the aortic arch to about the twelfth vertebrae at the aortic hiatus in the diaphragm, and feeds the bronchial arteries, esophageal arteries, and posterior intercostal arteries, among other branches of the vascular system. The abdominal aorta commences at the distal end of the thoracic aorta and continues downward until it splits into the two common iliac arteries near the fourth lumbar vertebra, supplying the celiac artery, mesenteric arteries, and renal arteries, among other branches. Each common iliac artery subsequently splits into an internal iliac and an external iliac artery. The external iliac artery continues downward until the upper thigh, where it becomes the femoral artery, the primary conduit to carry blood to the lower limbs. For common endovascular procedures, especially aortic repair procedures, physicians often access a patient&#39;s vasculature via the femoral artery since it approaches the skin and can be easily palpated. During endovascular procedures, physicians often encounter vessels affected by arteriosclerotic disease. 
     Referring to  FIGS. 1-4 , an atherosclerotic vessel may be characterized by plaque deposits formed upon the vessel wall, which may occlude the vessel and complicate passage of endovascular devices. Such deposits may be so brittle or unstable that they become detached from the vessel wall when an endovascular device exerts a friction or pushing force upon the deposit. This plaque disruption can be highly dangerous to the patient, for example if it causes downstream embolism. 
     An endovascular device  10  is equipped with a vascular force reduction system  20 . In this embodiment, the endovascular device  10  includes a guidewire  30 , although it may alternatively include a catheter, introducer, sheath, or other device. As shown, the guidewire  30  may traverse a plaque deposit  40  within a vessel  50  by “rolling” over it rather than sliding. The endovascular device  10  may have a slender section  60  comprising a material suitable for endovascular procedures, e.g., stainless steel, nitinol, polymeric or other materials, a proximal end  70  that a physician inserts into a patient&#39;s vasculature as part of an endovascular procedure, and a distal end  80  that terminates outside the patient&#39;s body. The guidewire  30  may generally have a circular cross section, but need not have a circular cross section and need not have the same cross section along its length. However, the cross sectional dimensions of the guidewire  30  should be sufficiently small to permit introduction into a patient&#39;s vasculature. The section  60  may be coated with a hydrophilic coating to reduce the input force necessary to move the guidewire  30  in the proximal or distal direction. Additionally or alternatively, the section  60  may be coated with a pharmacological substance, such as heparin or the like. 
     The force reduction system  20  may include a plurality of rotating assemblies  90  rotatably mounted upon a plurality of support structures  110 , such that a vessel contact surface  92  of each rotating assembly  90  may directly or indirectly contact the vessel wall  52  or plaque deposit  40 . In different embodiments, the support structure may assume different forms, including branch-type, 8-shape, S-shape, E-shape, aperture-type, and other shapes. The rotating assemblies  90  may be mounted upon the support structures  110  such that each rotating assembly  90  may rotate substantially toward the proximal and distal ends  70 ,  80  of the endovascular device  10 . To enable this rotation, in some embodiments, each rotating assembly  90  may rotate within a plane that is substantially parallel to or coincident with a section of the endovascular device  10 . Each rotating assembly  90  may include a rotating element  100  and optionally a band  104 . The vessel contact surface  92  of the rotating assembly  90  may be the surface of each rotating element  100  or band  104  that may come into direct contact with a vessel wall  52  or plaque deposit  40  during an endovascular procedure, which may correspond to a radial outermost surface of the rotating element  100  or a band  104 . Greater surface area of vessel contact surface  92  may advantageously correspond with lower vessel wall pressures. The plurality of rotating assemblies  90  may be positioned near the proximal end  70  of the endovascular device  10 , but may extend distally along a portion of or the entire length of the device  10 . In operation, contact between the vessel contact surface  92  and the vessel wall  52  or plaque deposit  40  enables the endovascular device  10  to roll along the vessel wall  52  instead of sliding, for example during an endovascular procedure when a physician manipulates an endovascular device  10  in the proximal or distal directions. The static and dynamic friction forces created by this friction reduction system  20  may be substantially lower than the friction forces created between a vessel wall  52  and the guidewire  30 , catheter, introducer, sheath, or other endovascular device  10  not equipped with a vascular force reduction system  20 . 
     Each rotating element  100  of the rotating assembly  90  may include a roller, a bead, a bearing, or other component capable of continuous and reversible revolution within a rotational plane  120  about a revolutionary axis. The rotating element  100  may be generally cylindrical or spherical, but may otherwise include other shapes with approximately constant cross section about the revolutionary axis. The rotating element  100  may have a diameter, a width, an outermost surface  102  (which may correspond to the vessel contact surface  92  in embodiments without bands), and may include a bore capable of receiving an axle  140 . Alternatively, the rotating element  100  may include other mounting means to rotatably mount the rotating element  100  upon the support structure  110 . Exemplary bearings for the rotating element  100  include No. B0.6-1h26 ball bearings, produced by ISC NSK Micro Precision Co., Ltd. of Tokyo, Japan. The B0.6-1h26 ball bearing features an outside diameter of 2.0 mm, making it dimensionally suitable for endovascular navigation of the femoral artery, along with the iliac artery and aorta, the diameters of which generally exceed that of the femoral artery. See Sandgren, Thomas, et. al,  The Diameter of the Common Femoral Artery in Healthy Human: Influence of Sex, Age, and Body Size,  29 Journal of Vascular Surgery, Issue 3, 503-510 (finding a mean common femoral artery diameter of 9.8 mm in male subjects and 8.2 mm in female subjects). 
     To mitigate sterilization concerns related to the incorporation of rotating assemblies  90  into endovascular devices  10 , any rotating assembly  90  may be manufactured with sufficiently tight tolerances to prevent introduction of blood into any internal components, e.g., between a cage and a ball or a roller of a bearing. Additionally, the rotating assembly  90 , including the rotating element  100 , may be coated with antimicrobial agent(s) to prevent infection or other harmful biological reaction. Like the endovascular device  10  itself, the rotating assembly  90  may be coated with a hydrophilic coating to reduce the input force necessary to move the endovascular device  10  in the proximal or distal direction. 
     As noted above, each rotating assembly  90  may optionally include one or more bands  104  to enhance vessel wall traction and to reduce pressure exerted upon the vessel wall  52 . In such embodiments, each band  104  may completely or partially surround one or more surfaces of the rotating element  100  (e.g., roller, a bead, a bearing, or other component) such that band  104  can make contact with the vessel wall  52  during an endovascular procedure. Thus, in embodiments that include one or more bands  104 , a radially outermost surface of the band  104  may correspond with the vessel contact surface  92  of that rotating assembly  90 . In some embodiments, one or more rotating elements  100  may include one or more bands  104  snugly fitted to a radial outermost surface  102  of each rotating element  100 . In such embodiments, the band  104  may retain its position relative to the corresponding rotating element  100  by friction fit, adhesion, or alternative method. In other embodiments, one or more bands  104  may connect a plurality of rotating elements  100  by running along the radially outermost surface  102  of each rotating element  100 ; such embodiments may further reduce vessel wall pressures by increasing the surface area in contact with the vessel wall  52 . 
     The band(s)  104  may be constructed from a number of suitable materials, including polymers such as silicone or other suitable materials that provide a high-friction interface with a vessel wall  52 . The bands  104  may have a relatively flat cross section with a thickness comparatively small relative to the band width. Alternatively, the bands  104  may have a cross sectional thickness that approaches or exceeds the band width in certain locations, such as a V-shape. In some embodiments, bands  104  may reside within a channel formed into the radially outermost surface  102  of one or more of the rotating elements  100 , and may further be located by one or more flanges and/or bead seats. Each band  104  may have a high-friction outer surface  180  that makes direct contact with the vessel wall  52  (i.e., forming the vessel contact surface  92 ), and the outer surface  180  may feature traction elements  190  capable of reversibly attaching to the vessel wall  52 . Ideally, the traction elements  190  will not disturb plaque deposits  40  formed within the vessel  50 , for example by exerting relatively large shear forces. One suitable traction element  190  is a synthetic setae configuration, such that the traction element  190  creates a strong retention force with the vessel wall  52 , which may be reversed with a relatively small force. Such a traction element  190  configuration is unlikely to disrupt plaque deposits, disrupt the vessel lining, or otherwise damage the vessel or cause vessel trauma. Alternative traction elements may also be suitable, for example ribs, treads, blocks, other raised elements, grooves, and sipes. 
     The support structure  110  may assume different configurations, for example depending upon whether the vascular force reduction system  20  forms part of a guidewire, a catheter, introducer, sheath, or other endovascular device. Generally, the support structure  110  may include an axle  140  to support each rotating assembly  90 , although one axle  140  may support more than one rotating assembly  90 . The axle  140  may support the rotating assembly  90  such that the outermost surface  102  of the rotating element  100  or the band  104  can directly or indirectly contact the vessel wall  52  during an endovascular procedure. The axle  140  may be distinct from the guidewire, catheter, or other endovascular device  10 , or it may be integral to the device  10 . The support structure  110  may enable the rotating assembly  90  to rotate substantially in the proximal and distal directions, e.g., the rotating element  100  may rotate within a rotational plane  120  that is substantially coincident with or parallel to the section  60  of the guidewire, catheter, or other endovascular device  10  upon which the rotating element  100  is mounted. An angle between the rotational plane  120  and the portion of the guidewire, catheter, or other endovascular device  10  may range from zero to about thirty degrees. As the endovascular device  10  navigates tortuous anatomy, the relative positions of the support structures  110  may change. To enable adaptation to dynamic vascular geometry, the support structures  110  may be spaced apart by sufficient distance to enable the endovascular device  10  to flex under bending and torsion forces without one support structure  110  interfering with the operation of another, e.g., by at least approximately 0.1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 10 mm, 15 mm or greater spacing. 
     Advantageously, the vascular force reduction system  20  protects the endovascular device  10  within a core protective zone  200 : an elongate volumetric space bounded by one or more rotating assemblies  90  that protects the portion of the endovascular device  10  supporting the vascular force reduction system  20 . For any given embodiment, the core protective zone  200  may have a cross sectional area that approximates a circle, rectangle, or other shape that circumscribes the radial outermost points of the endovascular device  10 , e.g., the radial outermost points of one or more rotating assemblies  90 . Furthermore, the core protective zone  200  may have a maximum cross sectional dimension that is less than the smallest vascular diameter to be traversed in an endovascular procedure. This maximum cross sectional dimension may vary between embodiments and may further vary based upon the sex, ethnicity, age, and other physiological variable of the intended patient. For example, the maximum cross sectional dimension of the core protective zone  200  may be less than approximately 10 mm, 9 mm, 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, or other dimension depending upon the application. 
     The core protective zone  200  may begin near the proximal-most rotating assembly  90  and may extend distally along the endovascular device  10  until at least the distal-most rotating assembly  90 . The vascular force reduction system  20  suspends a portion of the endovascular device  10  within the core protective zone  200 , where one of the rotating assemblies  90 —rather than the side of an endovascular device (e.g., an outer surface of guidewire section  60  or a catheter wall)—is likely to make contact with the vessel wall  52  and plaque deposit  40 . In operation, as a physician guides the endovascular device  10  through a patient&#39;s vasculature, a section of the guidewire, catheter, introducer, sheath, or other device is likely remain within the core protective zone  200 , where it is unlikely to make direct contact with the vessel wall  52 . Rather, the rotating assemblies  90  contact the vessel wall  52 , and the endovascular device rolls along the vessel wall  52  instead of sliding. In this manner, the endovascular devices described herein exert lower forces on the vessel wall, plaque deposits, occlusions, or other portions of the patient&#39;s vasculature. 
     The vascular force reduction system described herein may be constructed in a number of configurations and incorporated into a number of endovascular devices. It shall be understood that technical features of the embodiments illustrated herein may be selectively adapted to different embodiments to suit the needs of a wide range of applications. 
     For example, the endovascular device  10  of  FIGS. 1-4  includes a guidewire  30  equipped with a vascular force reduction system  20  having a plurality of unguarded, branch-type support structures  110 , with each support structure including an axle  140  mounted upon the guidewire  30  in a staggered planar opposed configuration, and with each axle  140  supporting a rotating assembly  90 , each of which include a rotating element  100  having an optional band  104  with an outer surface corresponding to the vessel contact surface  92 . Each successive rotating assembly  90  resides on approximately the opposite side of the guidewire  30  relative to the next successive rotating assembly  90 , with some or all rotating assemblies  90  occupying approximately the same horizontal plane when viewed along the guidewire  30  as shown in  FIG. 2 . The support structures  110  are spaced apart in order to enable the guidewire  30  to conform to the tortuous anatomy of a patient without one support structure  110  interfering with the operation of another. In the embodiments of  FIGS. 1-4  and other embodiments, the support structures  110  may be spaced apart by approximately 0.1 mm to approximately 15 mm, e.g., 10 mm. Each axle  140  may protrude radially outwardly from the guidewire  30  at approximately a ninety degree angle, and may be affixed to the guidewire  30  by any suitable method, for example soldering or welding. In other embodiments, the support structures, including axles, may protrude from the endovascular device at a different angle, for example between approximately sixty to ninety degrees. Each axle  140  may fully extend through the bore of each rotating element  110  or partially therethrough. In either case, the rotating element  100  may be retained upon the corresponding axle  140  by a clip, retainer, cap, detent-notch combination, or similar structure. In this embodiment, to enable contact with the vessel wall  52 , the diameter of each rotating assembly  90  may exceed the diameter of the guidewire  30  so that when viewed from the side as in  FIG. 4 , each rotating assembly  90  projects both above and below the guidewire  30 . In this embodiment, the core protective zone  200  has a cross sectional area that approximates a rectangle circumscribing the frontal profile of the rotating assemblies  90  when viewed from the front as in  FIG. 2 , and has a length that extends from approximately the proximal-most rotating assembly  90  to the distal-most rotating assembly  90 . In particular, the vessel contact surfaces  92  of the rotating assemblies  90  may bound the largest cross sectional dimension of the core protective zone  200 . In operation, a portion of the guidewire  30  resides within this core protective zone  200 , where it is unlikely to contact the vessel wall  52  directly. 
     Referring now to  FIG. 5 , another endovascular device  210  may include a guidewire  220  with a vascular force reduction system  230  having a plurality of S-shaped support structures  240  arranged in a coincident aligned configuration along the guidewire  220 . A plurality of rotating assemblies  242  include a plurality of rotating elements  250  that rotate within approximately the same rotational plane as each other, which rotational plane may be approximately coincident with the guidewire  220  for improved tracking, or parallel to the guidewire but separated by a small distance. Other embodiments may utilize different support structures, such as S-type, E-type, or 8-type support structures, to enable rotating elements to rotate within one or more planes that are approximately coincident with the endovascular device. In such other embodiments, each successive support structure may have a different radial orientation than an adjacent support structure, such that each rotating element may rotate within a different rotational plane from adjacent rotating elements. The embodiment of  FIG. 5  advantageously offers the potential for a reduced cross-sectional area relative to other configurations. Each support structure  240  may have at least four bends, each with an approximately ninety degree interior angle. The bends of each support structure  240  may form a proximal window  260  and a distal window  270 . The central leg of each support structure  240  may serve as an axle  280  for supporting the rotating assembly  242 , including the rotating element  250  and a band  252  having a vessel contact surface  254 . As the rotating element  250  rotates about the axle  280 , it traverses the proximal and distal windows  270 ,  280 . Additionally, a proximal guard  290  and a distal guard  300  may prevent plaque or endovascular debris from fouling operation of the rotating element  250 . To reduce vessel trauma in this embodiment and other embodiments with guards, junctions between guards may be smoothed, rounded, blunted, or otherwise formed to avoid point or sharp edges. The elongate band  252  may connect a plurality of the rotating assemblies  242 , which may advantageously reduce vessel trauma in operation by distributing forces over the vessel contact surface  254 . A vessel contact surface  254  with greater surface area may exert lower pressures on the vessel wall  52 , as compared to a vessel contact surface  254  with lesser surface area. A core protective zone  310  may have a frontal cross section that approximates a rectangle or an oval circumscribing the frontal area of the endovascular device  210 . Advantageously, the guards  290 ,  300  further protect a portion of the guidewire  220  within the core protective zone  310 . 
       FIGS. 6-6A  illustrate another endovascular device  320  including a guidewire  330  and a vascular force reduction system  340  having a helical arrangement of support structures  350  and rotating assemblies  352 , each rotating assembly  352  including a rotating element  360  and optionally a band  362 . The illustrated embodiment utilizes unguarded, lateral, branch-type support structures  350  that protrude radially outward from the guidewire  330  in a helical series, with each successive support structure  350  protruding at a different angle relative to the adjacent support structures  350 . An axle  370  of each successive support structure  350  may have an angle of protrusion that differs by about fifteen to sixty degrees from the axle of the preceding and/or succeeding support structure  350 . Successive support structures  350  may be spaced apart by approximately 0.1 mm to approximately 15 mm, e.g., 10 mm, and may be arranged such that an outermost surface of each rotating element  360  or band  362  corresponds to a vessel contact surface  380 . When constructed in this configuration, the vascular force reduction system  340  suspends the guidewire  330  within a core protective zone  390  having a cross sectional area that approximates a circle circumscribing the frontal area of the endovascular device  320 , as seen in  FIG. 6A . Alternative embodiments may incorporate a helical arrangement similar to that illustrated in  FIGS. 6-6A , along with different support structures, for example S-type, 8-type, and E-type support structures. 
       FIGS. 7-7A  illustrate another endovascular device  400  including a guidewire  410  and a vascular force reduction system  420  having a star-shaped arrangement of support structures  430  and rotating assemblies  432 , each rotating assembly  432  including a rotating element  440  and optionally a band  442 . An outermost surface of the rotating element  440  or band  442  may form a vessel contact surface  444 , which may have traction elements  446 . The support structures  430  and rotating assemblies  432  project radially outward from the guidewire  410 , each support structure  430  including an axle  450  that supports the rotating assembly  432 . As shown, each support structure  430  may include a continuous segment of material, although each segment may alternatively include two or more joined elements. A group  460  of support structures  430  may reside at a common position along the length of the guidewire  410 , and multiple groups  460  may exist along the guidewire  410 . Each group  460  may include a plurality of rotating assemblies  432  spaced approximately equally about the circumference of the guidewire  410 . Such a group may include at least three rotating assemblies  432  (e.g., with  120  degree radial spacing), although it may be desirable to use a greater number of rotating assemblies  432  (e.g., six rotating assemblies with  60  degree radial spacing). The vascular force reduction system  420  suspends the guidewire  410  within a core protective zone  470  occupying a region extending along the guidewire  410  for the length of the vascular force reduction system  420 , with a cross sectional area approximating a triangle or tri-oval circumscribing the frontal area of the endovascular device  400 . 
     Although the foregoing embodiments describe aspects of the invention in the context of a guidewire, the invention is also applicable to other endovascular devices, e.g., catheters, introducers, sheaths, and other similar devices that may directly contact a vessel wall. As with guidewire embodiments, a vascular force reduction system incorporated into a catheter, introducer, sheath, and similar device may be positioned near the proximal end of the device, and may extend distally along a portion of or the entire length of the device. Additionally, in some embodiments, each support structure may be formed integrally to the endovascular device, or formed separately and adjoined thereto. A vascular force reduction system may optionally include one or more bands as described above, for example to enhance vessel wall traction and reduce pressure exerted upon the vessel wall. 
       FIG. 8  shows yet another endovascular device  480  including a catheter  490  and a vascular force reduction system  500  utilizing aperture-type support structures  510 , wherein a rotating assembly  512  (including a rotating element  520  and a band  522 ) resides within an aperture  530  extending through a catheter wall  540 . An axle  550  may bifurcate each aperture  530  at an orientation that is approximately perpendicular to an elongate section of the catheter  490 . The axle  550  may be formed separately and fixed within the aperture  530 , or formed integrally to the aperture  530 . Integrally-formed axles  550  may include a plurality of sub-axles that project circumferentially inward from the perimeter of the aperture  530 . The axle  550  supports the rotating element  520  within the aperture  530  so that it may rotate in substantially the proximal and distal directions. In such a configuration, a portion of each rotating element  520  projects radially outward from the aperture  530 , and a portion projects radially inward into a lumen  560  of the catheter. To preserve the ability to insert one or more other medical devices through the catheter lumen  560 , it may be advantageous to size the rotating elements  520  and otherwise configure the vascular force reduction system  500  to preserve a passageway within the catheter lumen  560 . For example, it may be advantageous if the vascular force reduction system projects into the catheter lumen  560  by a relatively small amount. The band  522  connects the plurality of rotating elements  520  to form a relatively large vessel contact surface  524 , and may have traction elements  580  such as synthetic setae. Each aperture  530  guards the rotating element  520  residing within it, so as to protect the rotating element  520  from fouling. In such an embodiment, each rotating element  520  may have a very small diameter, e.g., between approximately 0.1 mm to approximately 5 mm. Also, such an embodiment may advantageously present a smaller cross section because each rotating element  520  is partially recessed within the catheter lumen  560 . 
       FIGS. 9-9A  illustrate another endovascular device  590  including a vascular force reduction system  600  with star-shaped groups  602  of rotating assemblies  612  (including rotating elements  620  and bands  622 ) positioned along a catheter  630 . Like the embodiment of  FIG. 8 , a plurality of support structures  610  each includes an aperture  640  extending through a catheter wall  650 , with an axle  660  that may bifurcate the aperture  640  at an orientation that is approximately perpendicular to a longitudinal section of the catheter  630 , and each rotating element  620  may project radially outward through the aperture  640 . Each group  602  of rotating assemblies  612  may reside at approximately a common position along the elongate section of the catheter  630 , and more than one group  602  may exist along the catheter  630 . Within each group  602 , the rotational plane of each rotating assembly  612  differs from adjacent rotating assemblies  612 . When viewed along the catheter as in  FIG. 9A , it can be seen that each group  602  of rotating assemblies  612  may include individual rotating elements  620  spaced approximately equally about the circumference of the catheter  630 . Such an arrangement may include at least three rotating elements  620  (e.g., with 120 degree radial spacing), although it may be desirable to use a greater number of rotating elements  620  (e.g., six rotating elements with 60 degree radial spacing). The elongate bands  622  may connect a plurality of rotating elements  620 . In operation, each elongate band  622  may reduce vessel trauma by distributing forces over a relative large vessel contact surface  670 . In this embodiment, each band  622  connects a plurality of rotating elements  620 , although in other embodiments each band may completely or partially surround a single rotating element, or the rotating element may be un-banded. The vascular force reduction system  600  suspends the catheter  630  within a core protective zone  680  occupying a region extending along the catheter  630  for the length of the vascular force reduction system  600 , with a cross sectional area approximating a triangle, a tri-oval, or a circle that circumscribes the rotating assemblies  612  when viewed from the front, as in  FIG. 9A . Additional pluralities of rotating assemblies  612  may be positioned along the catheter  630  to extend the core protective zone  680 . 
       FIGS. 10-10A  show another endovascular device  690  incorporating a vascular force reduction system  700  with a helical arrangement of aperture-type support structures  710  and rotating assemblies  712  (including rotating elements  720  and optional bands  722 ) positioned along a catheter  730 . Adjacent rotating assemblies  712  project through a wall of the catheter  730  at different radial angles (angle of protrusion) and at different positions along the catheter  730 , so as to form a helix of rotating assemblies  712 . Adjacent rotating assemblies  712  may have an angle of protrusion that differs by about fifteen to sixty degrees, and may be spaced apart by approximately 0.1 mm to approximately 10 mm, e.g., 4 mm. The vascular force reduction system  700  suspends the catheter  730  within a core protective zone  740 , where the rotating assemblies  712  are likely to make contact with the vessel wall. The core protective zone  740  occupies a region extending along the catheter  730  for the length of the vascular force reduction system  700  and has a cross sectional area that approximates a circle approximately circumscribing the radial outermost surface of the rotating assemblies  712 , as seen in  FIG. 10A . A similar helical arrangement may be incorporated into other embodiments utilizing different support structures, e.g., branch-type and recess-type support structures. Furthermore, it is possible to incorporate rotating assemblies  712  in a double- or multiple-helix formation (not shown). 
     It shall be understood that the present embodiments may be constructed in numerous configurations not illustrated herein. For example, in embodiments having a guidewire, the support structures may project from only one side of the guidewire, for example to reduce the frontal profile of the device. In such embodiments, the core protective zone may have a cross sectional area that more closely hews to the side of the rotating assemblies. Additionally or alternatively, embodiments may include U-shaped, V-shaped, trapezoid-shaped, or other polygonal-shaped support structures having legs forming internal bends that together create a window. In such embodiments, one of the legs may operate as an axle for a rotating element, especially if it protrudes from the guidewire at approximately ninety degrees. Thus, the rotating element may traverse the window as it revolves about the axle. Additionally or alternatively, the support structures may occupy the same plane or different planes. In such embodiments, a plurality of support structures may project from approximately the same side of the guidewire, and another plurality may project from another side (e.g., the opposite side), in order to create a core protective zone for the guidewire. 
     In operation, an operator may insert an endovascular device equipped with a vascular force reduction system into a patient&#39;s anatomy, e.g., subcutaneously via an incision. The physician may guide the device in the proximal direction, for example to a position proximal of an aneurysm. During such a procedure, the operator may roll the endovascular device over the vessel wall or plaque deposit. In particular, the vessel contact surface of the vascular force reduction system will roll over the vessel wall or deposit. Depending on the type of endovascular device, the physician may guide one or more additional endovascular devices over or within the vascular force reduction system-equipped device. For example, the physician may guide a catheter over a guidewire, and one or both of the catheter and guidewire may be equipped with a vascular force reduction system. The physician may ultimately remove the endovascular device equipped with the vascular force reduction system from the patient&#39;s vasculature, e.g., by withdrawing it in the distal direction. 
     The foregoing endovascular devices equipped with vascular force reduction systems may advantageously exert lower radial and shear forces on the vessel wall, reducing the risk of vessel damage during endovascular procedures. Similarly, by rolling over plaque deposits instead of sliding in an uncontrolled manner, endovascular devices incorporating a vascular force reduction system may exert lower radial and shear forces on plaque deposits, thereby reducing embolism risk. Furthermore, by reducing input forces, the vascular force reduction systems disclosed herein may enable devices to navigate tortuous anatomy that might otherwise be unnavigable with endovascular devices known in the art. Separately, because endovascular devices equipped with a vascular force reduction system may require lower input forces, those devices need not have the stiffness or rigidity that would otherwise be necessary; as a result, endovascular devices can be manufactured with reduced cross sectional areas, which further reduces trauma to the patient. Together, these advantages may enable a greater number of patients to qualify for endovascular procedures who might otherwise be ineligible, for example due to highly tortuous or occluded vasculature. 
     While various embodiments of the invention have been described, the invention is not to be restricted except in light of the attached claims and their equivalents. Moreover, the advantages described herein are not necessarily the only advantages of the invention and it is not necessarily expected that every embodiment of the invention will achieve all of the advantages described.