DEVICE AND METHOD FOR ALTERING BLOOD FLOW CHARACTERISTICS IN A VESSEL

Abstract

A device (15, 50, 55, 60, 100, 200) for altering blood flow characteristics in a vessel (20), the device (15, 50, 55, 60, 100, 200) comprising: a cuff (10) configured to be surgically positioned around a portion of the vessel (20); a first pad (40) located on an internal wall of the cuff (10), wherein the pad (40): locally reduces a cross-sectional area of a passageway (25) extending through the cuff (10) and/or defines a passageway (25) within the cuff (10) which is non-linear.

Claims

1. A device for altering blood flow characteristics in a vessel, the device comprising: a cuff configured to be surgically positioned around a portion of the vessel; a first abutment formation located on an internal wall of the cuff, wherein the abutment formation: locally reduces a cross-sectional area of a passageway extending through the cuff and/or defines a passageway within the cuff which is non-linear.

2. The device of claim 1, wherein the passageway is curved about one or more axes which extend generally perpendicular to the direction of blood flow.

3. The device of claim 1 or 2, wherein the first abutment formation is defined by a first pad.

4. The device of claim 3, further comprising a second pad and a third pad, wherein the three pads a longitudinally separated within the cuff, and spaced around the circumference of the cuff.

5. The device of claim 4, wherein the three pads are evenly spaced circumferentially at about 120 degrees relative to each adjacent pad.

6. The device of claim 3 further comprising a second pad diametrically opposed relative to the first pad, and in axial alignment with the first pad, defining a first pair of pads.

7. The device of claim 6, further comprising a second pair of pads which are also diametrically opposed and axially aligned.

8. The device of claim 7, wherein the first pair of pads is longitudinally spaced relative to the second pair of pads to define an expansion chamber within the cuff.

9. The device of claim 7 further comprising a third pair of pads which are also diametrically opposed and axially aligned.

10. The device of claim 9, wherein the first pair of pads is located adjacent to a proximal end of the device and the second pair of pads is located adjacent to a distal end of the device, the first and second pairs of pads being in circumferential alignment.

11. The device of claim 9, wherein the third pair of pads is located between the first pair of pads and the second pair of pads, further wherein the third pair of pads is circumferentially offset by about 90 degrees.

12. The device of any one of claims 3 to 11, wherein the pads are gel filled.

13. The device of any one of the preceding claims, wherein the cuff is defined by a generally tubular body.

14. The device of claim 13, wherein the cuff includes a longitudinally extending seam which permits the cuff to be placed around the vessel.

15. The device of claim 14, wherein the seam is defined by first and second longitudinally extending arms which are selectively securable to each other.

16. The device of any one of the preceding claims, wherein the cuff is defined by an elastically deformable helical body which is coated in a compliant layer.

17. The device of claim 16, wherein the elastically deformable helical body is fabricated from Nitinol? and the compliant layer is fabricated from silicone.

18. The device of any one of claim 16 or 17, wherein a radially internal surface of the compliant layer is curved, such that a cross sectional area of the compliant layer is generally D shaped when sectioned through a plane which is parallel with and passes through a longitudinal axis of the helical body.

19. The device of any one of claims 16 to 18, wherein a radially internal surface of the compliant layer includes at least one inwardly extending projection.

20. A method of altering blood flow characteristics within a vessel, the method including the steps of: surgically positioning a cuff around a portion of the vessel, and locally altering blood flow characteristics in the vessel with one or more abutment formation located within the cuff, the abutment formation: reducing a cross-sectional area of a passageway extending through the vessel and/or deforming the vessel to define a region which is curved about one or more axes which extend generally perpendicular to the direction of blood flow.

21. A device for altering blood flow characteristics in a vessel, the device comprising: a helical cuff configured to be surgically positioned around a portion of the vessel, a first abutment formation defined by an internal wall of the helical cuff, and a central spine located within the helical cuff, wherein the abutment formation: locally reduces a cross-sectional area of a passageway extending through the cuff and/or changes a cross-sectional shape of the passageway extending through the cuff and/or defines a passageway within the cuff which is non-linear.

22. The device of claim 21, wherein a cable is located adjacent to the central spine, the cable extends between proximal and distal ends of the device, the cable length being selectively adjustable to change the shape of the helix, such that shortening the cable reduces a pitch of the helix and increases a diameter of the helix.

23. The device of claim 21, wherein a cross sectional area of the passageway varies along the length of the device between proximal and distal ends.

24. The device of claim 21, wherein a cross-section of the helical cuff varies along the length of the device between proximal and distal ends.

25. The device of any one of claims 21 to 24, further comprising one or more sensors located on the helical cuff for obtaining data relating to blood flow characteristics within the vessel and/or vessel characteristics.

26. The device of claim 25, wherein the sensors include one or more of electrodes, pressure sensors and ultrasonic emitters.

27. The device of claim 25 or 26, wherein the sensor(s) is located on a radially internal portion of the helical cuff, positionable in direct abutment with the vessel.

28. The device of any one of claims 25 to 27, wherein the sensors are configured to wirelessly communicate with a computer or other such device to transmit information concerning measured blood flow characteristics and/or vessel characteristics.

29. The device of claim 21, wherein a cross sectional shape of the passageway varies along the length of the device between proximal and distal ends.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] A preferred embodiment of the invention will now be described by way of specific example with reference to the accompanying drawings, in which:

[0060] FIG. 1 is a schematic diagram of a human heart;

[0061] FIG. 2 is a schematic view of a device for modifying blood flow characteristics according to a first embodiment of the invention;

[0062] FIG. 3 is a further schematic view of the device of FIG. 2;

[0063] FIG. 4 depicts a device for modifying blood flow characteristics according to a second embodiment of the invention;

[0064] FIG. 5 depicts a device for modifying blood flow characteristics according to a third embodiment of the invention;

[0065] FIG. 6 depicts a device for modifying blood flow characteristics according to a fourth embodiment of the invention;

[0066] FIG. 7 is side view of a device for modifying blood flow characteristics according to a fifth embodiment when deployed;

[0067] FIG. 8 is a perspective view of the device of FIG. 7;

[0068] FIG. 9 is a further side view of the device for modifying blood flow characteristics according to FIG. 7;

[0069] FIG. 10 is a cross-sectional side view of a portion of the device of FIG. 7;

[0070] FIG. 11 is a cross-sectional side view of a portion of the device of FIG. 7 when deployed;

[0071] FIG. 12 is a front view of a device according to a sixth embodiment;

[0072] FIG. 13 is top view of the device of FIG. 12;

[0073] FIG. 14 is an end view of a device of FIGS. 12 and 13;

[0074] FIG. 15 is a partial detail of the end view of FIG. 14; and

[0075] FIG. 16 is a perspective view of the device of FIGS. 12 to 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0076] There are disclosed herein several embodiments of devices 15, 50, 55, 60, 100, 200 for altering blood flow characteristics in the form of an external cuff or band 10 which is surgically placed around the external wall of a blood vessel 20, preferably the carotid artery, including the common carotid artery or the internal carotid artery. The cuff 10 deforms the arterial wall and as a result alters the blood flow characteristics within a passage 9 of the vessel 20, by changing the geometry of the vessel 20 such that along the length of the cuff 10, the vessel 20 wall profile is altered. The change in vessel 20 structure may result in a change of cross-sectional shape, and/or cross-sectional area and/or vessel curvature or bending about an axis which extends generally perpendicular to the direction of flow (i.e. the vessel is locally made non-linear).

[0077] The device 15, 50, 55, 60, 100, 200 is preferably placed around the outside of the common carotid artery. Its intended function is to modify the dynamics of transmission of arterial blood pressure to the cerebral microvasculature and to absorb excess energy from the arterial pulse.

[0078] Each embodiment of the device 15, 50, 55, 60, 100, 200 includes a member which is placed around the vessel during a surgical procedure.

[0079] In each embodiment described herein, the device 15, 50, 55, 60, 100, 200: [0080] locally reduces or changes the shape of a cross-sectional area of a vessel 20; and/or deforms the vessel 20 extending through the passageway 25 which is non-linear and typically curved or bent about one or more axes which extend generally perpendicular to the direction of blood flow (i.e. the vessel is made locally non-linear).

First Embodiment

[0081] In the first embodiment, depicted in FIGS. 2 and 3, the device 15 includes a cuff 10 which forces a portion of the vessel 20 to adopt a bent or curved profile, having curvature about one or more axes which extend generally perpendicular to the direction of blood flow (i.e. the vessel 20 becomes locally non-linear). As depicted, the cuff 10 includes an outer scaffold 30 fabricated from a suitable biocompatible material such as stainless steel or Nitinol. The scaffold 30 may be formed as two halves and located around the vessel and attached to each other. Alternatively, the scaffold may be fabricated as a single component which is sufficiently compliant to allow it to be wrapped around the vessel, prior to subsequent attachment of the two opposing sides to define a generally tubular cuff 10.

[0082] Abutment formations in the form of pads or buffers 40 are located on the radial inner wall of the cuff 10. The pads 40 are preferably gel pads 40 and may be defined by a single gel pad 40, or a plurality of independent gel pads 40. In the embodiment shown in FIGS. 2 and 3, the gel pads 40 cause the deformation of the vessel 20, forcing the vessel 20 to adopt a curving profile, within the wall of the scaffold 30 which is generally locally cylindrical. The curvature of the deformed vessel 20 as depicted schematically in FIG. 1 has a central concave region and adjacent convex regions, such that the blood flow path is significantly diverged away from linear.

[0083] The pads 40 are not limited to gel pads, and may be fabricated from other material such as polymers of varying hardness or gas filled cushions.

[0084] The gel pads 40 serve two purposes. Firstly, the gel pads 40 define the desired deformation in the wall of the blood vessel 20. Secondly, the gel pads 40 dampen the energy carried by the blood flow when the blood flow comes into contact with the wall of the vessel 20, as the outer wall of the vessel 20 is in direct abutment with the gel pads 40.

[0085] Due to the deformation of the vessel 20, the blood flow is forced to adopt a non-linear path within the cuff 10. Accordingly, the pressure wave, which travels axially within a vessel 20, contacts the wall of the vessel 20, which in turn is supported against the gel pad 40. The gel pad 40 absorbs some of the energy carried by the blood flow.

[0086] Furthermore, the deformation of the vessel 20 results in the reflected portion of the pressure wave being non-axial relative to the vessel 20. This typically results in the reflected wave coming into contact with the wall of the vessel 20 at several other locations, which may also reduce the energy intensity carried by the pressure wave downstream of the cuff 10.

[0087] In the first embodiment of FIGS. 2 and 3, the gel pad 40 and the cuff 10 are arranged to introduce curvature into the vessel 20, while maintaining a generally circular cross-sectional area in the vessel 20, such that the vessel 20 generally maintains native diameter. In an alternative embodiment, in addition to introducing curvature in the vessel 20, the cuff 10 may also alter the cross-sectional area or shape of the vessel 20. For example, the vessel along its length can be partially flattened into an oval or elliptical cross-section, which has a cross-sectional area which is less than the native cross-sectional area of the vessel 20. The modified cross-section of the vessel 20 may be any shape, but typically the overall cross-section is flattened and widened.

[0088] Such partial flattening of the vessel 20 may desirably increase the ability of the vessel to become curved, due to the ribbon-like cross-sectional profile (once flattened) being more readily deformed.

[0089] The diameter (and length) of the passageway 25 passing through the tubular scaffold 30 relative to the native outer diameter of the vessel 20 defines the amount of curvature of the vessel which may be introduced by a given cuff 10.

Second Embodiment

[0090] A second embodiment of the device 50 is depicted in FIG. 4. In this embodiment, there are three gel pads 40, arranged around the circumference of the cuff 10. Each of the gel pads 40 is approximately evenly spaced longitudinally. Circumferentially the gel pads 40 are offset at approximately 120 degrees relative to each adjacent gel pad 40. The radial spacing of the gel pads 40 forces the blood flow to follow a more circuitous (non-linear) path. Furthermore, this arrangement promotes several points of contact where the axial pressure wave carried by the blood flow is forced to contact the vessel 20 wall at a location which is supported by one of the gel pads 40.

[0091] Due to the presence of the three gel pads 40, when looking axially though the vessel 20, there is a limited cross-sectional area within the vessel 20 which is unaffected by any one of the gel pads 40. In some arrangement, it may be the case that there is no direct line of site through the vessel 20 due to the level of deformation provided by the gel pads 40. However, because the gel pads 40 are axially spaced, each gel pad 40 only partially restricts or changes the shape of the local cross-sectional area of the vessel 20. Accordingly, the volumetric blood flow through the device 50 is not significantly affected, as the local cross-sectional area of the vessel 20 is not changed significantly relative to the natural cross-sectional area of the vessel 20 at any location. As such, the device 50 is able to deflect and/or absorb some of the energy carried by the pressure wave without significantly obstructing the volumetric blood flow rate.

[0092] As shown in FIG. 4, the scaffold is defined by a tube which is placed around the vessel and has a longitudinal split defining two arms 35. The arms 35 may be secured to each other with welding, stitching, gluing, stapling, corresponding male and female engagement formations or some other means which permits the arms 35 to be attached to each other quickly during surgery. It will be appreciated that in an embodiment in which the scaffold is made from a metallic material such as nitinol, the engagement may not be necessary.

Third Embodiment

[0093] A third embodiment of the device 55 is depicted in FIG. 5. The third embodiment is functionally similar to the second embodiment described above. However, there are three pairs of gel pads 40. The first pair of gel pads 42 are arranged diametrically opposite each other at a first (proximal) end 52 of the device 55. A second pair of gel pads 46 is arranged diametrically opposite each other, generally at a second (distal) end 56 of the device 55.

[0094] A third pair of gel pads 44 are arrange adjacent to the first pair, at a longitudinally central region 54 of the device 55. The third pair of gel pads 44 is circumferentially offset relative to the first and second pairs of gel pads 42, 46 by about 90 degrees.

[0095] Each pair of gel pads 42, 44, 46 locally flattens the vessel 20, such that the vessel 20 locally adopts an oval or elliptical profile, or at least a non-circular profile. In this way, at the junction between each pair of gel pads 42, 44, 46, the pressure waves contact with a step like change in vessel 20 geometry.

[0096] Similar to the second embodiment described above, when looking axially though the vessel 20, there is a limited cross-sectional area within the vessel 20 which is unaffected by any one of the gel pads 40, and located in the radial centre of the vessel 20.

Fourth Embodiment

[0097] A fourth embodiment of the device 60 is depicted in FIG. 6. The fourth embodiment is similar to the third embodiment described above but the central pair of gel pads are omitted. As such, in the fourth embodiment, there is a first pair of gel pads 62 located at a first end 64 of the device 60, and a second pair of gel pads 66 located at an opposing second end 68 of the device 60.

[0098] In the fourth embodiment, the space between the sets of gel pads 62, 66 defines an expansion chamber 70, located in a longitudinally central region of the device 60. The expansion chamber 70 permits the vessel 20 to locally expand or balloon, which may result in remodelling of the vessel geometry and which may reduce pressure within the vessel 20. The expansion of the portion of the vessel 20 located within the region of the expansion chamber 70 may occur permanently within the device 60, or as a result of changes in blood pressure within the vessel.

[0099] In a variation of the fourth embodiment, not shown in the drawings, the gel pads 62, 66 may be circumferentially angularly offset relative to each other by about 90 degrees, and with the expansion chamber 70 located in between.

[0100] Whilst the pads described in each embodiment have been described as separately formed components, it will be appreciated that the pads may be integrally formed with the cuff 10.

Fifth Embodiment

[0101] A fifth embodiment of the device 100 is depicted in FIGS. 7 to 11. The device 100 has a generally helical body or cuff 110, and in a similar manner to the earlier described embodiments, the device 100 is intended to be externally placed around the outside of the common carotid artery or the internal carotid artery.

[0102] The device 100 has a helical profile, so that it can be placed around the vessel 20 with minimal disturbance during a surgical procedure, with the elasticity of the device 100 permitting the vessel 20 to be seated radially within the central passageway 25 extending longitudinally through the helix of the device 100.

[0103] The device 100 includes a central spine 120 fabricated from an elastically deformable material such as medical grade Nitinol? or another suitable metal, metal alloy or polymer. The spine 120 is sheathed in a covering of silicone 130 or another suitable polymer. The silicone 130 is compliant, and reduces the risk of any damage to the external wall of the vessel 20. Whilst the device is depicted with the covering of silicone 130, it could alternatively be fabricated without the covering 130 such that the spine 120 defines the external surface for abutment with the vessel 20.

[0104] The device 100 is a single piece device with no articulated parts, constructed in the form of an open spiral helix with a total length of preferably about 45 mm, but may be provided in different lengths, in the range of 20-55 mm for the common carotid artery but may be longer or shorter in other vessels 20.

[0105] As depicted in FIG. 7, the device 100 is designed to fit around the outside of the common carotid artery or internal carotid artery, and deflects the artery (smoothly and continuously) along the length of the artery segment. For example, an 8 mm diameter common carotid artery would be deflected approximately 6 degrees from its long axis a number of times as it passes through the device 100. The artery 20 resumes its native path on exiting the device 100. The internal helix diameter of the device 100 defining the central passageway 25 is chosen to be less than the local artery external diameter in order to suitably deflect the artery. However, since the device 100 deforms the artery only at points of contact, that is, along the helix, it does not substantially alter the cross-sectional area nor the shape of the artery, because at no point does the device completely encircle the artery. If the pitch is small enough, the device 100 can reduce the diameter of the artery. In that case it can deflect as well as reduce the cross-sectional area of the artery. The pitch of the device 100 may be constant or variable. If the helix pitch is sufficiently fine, the device 100 may behave like a continuous tube, with minimal or no clearance between adjacent crests of the helix.

[0106] As depicted in FIG. 10, the central helical spine 120 is fabricated from a wound plate section of Nitinol?, such that the spine 120 is wound about the longitudinal helix axis As such, the spine 120 is resiliently deformable, and can be unwound to wrap around the vessel 20 before springing back to the native diameter of the device 100. The helical spine 120 is preferably preformed in a self supporting helix and fabricated for example in a heat-set process.

[0107] Referring to FIG. 10, the cross-sectional shape of the silicone covering 130 is generally contoured, such that the profile is an obround, ellipse, oval or another such formation. This creates gradual deformation of the vessel 20, and reduces the risk of damage to the vessel 20. This also assists to create a gradual transition within the vessel 20 from the region of native diameter to the region which is deformed by the device 100.

[0108] In one embodiment depicted in FIG. 11, the radially outer surface of the silicone 130 may be defined by a portion of a cylinder or tube, such that the radially outer surface is locally parallel with a longitudinal axis of the device 100. In contrast, the radially internal surface of the silicone 130 is curved, such that the cross-sectional area of the silicone 130 is generally D shaped when sectioned through a plane which is parallel with and passes through a longitudinal axis of the helix.

[0109] The device 100 is intended to locally alter the vessel by changing its shape and/or diameter and/or flow direction. For example, the device 100 may reduce the native cross-sectional area of the vessel by between about 5% and 30% and preferably by between about 10% and 20% and most preferably about 15%. However, the reduction in cross-sectional area may be higher, and up to 50%. In order to accommodate vessels of different cross-sectional area, the device 100 is fabricated in different helix diameters, and the device 100 having the most suitable dimensions is chosen before the surgical procedure to achieve an optimal fit to the patient's vessel geometry, and the intended restriction in cross-sectional area. It is envisaged that the device 100 may be supplied in about 12 different sizes, and the preferred size may be determined by imaging the vessel 20 prior to surgery. Another means of reducing the passageway 25 in the device 100 is by changing the silicone covering 130 to a thicker or thinner version on the inside of the device. Also, by placing a cable at one end and pulling from the other end, the device may be shortened and inner diameter increased. For this purpose, the nitinol spine may be a hollow tube. The cable may be shortened or lengthened by rotating a screw on one end of the device as described in the sixth embodiment below.

[0110] In the embodiment depicted in FIGS. 7 to 9, the length of the device 100 is equal to a multiple of approximately 1.5? the pitch. It will be appreciated that the length of the device 100 may be some other multiple of the pitch, for example between about 1 and 2? pitch. In more extreme cases the coil can be up to 30? the pitch or more. Alternatively, the device 100 may be provided in a fixed length, not related to pitch.

[0111] Referring to FIG. 9, inwardly extending projections 140 may be formed on the internal wall of the silicone covering 130. The projections 140 assist to further locally deform the vessel 20. The projections 140 may be intermittently spaced along the length of the helix and are each directed radially inwardly.

[0112] It will be appreciated that the ratio of the cross-sectional area of the Nitinol? spine 120 relative to the silicone 130 may vary beyond the embodiment depicted in the drawings. For example, by providing the Nitinol? in a thicker cross-sectional area, the stiffness of the device 100 may be increased. It will be appreciated that the nitinol may vary in cross-section along the length, so the ends are stiff and middle is soft for instance.

[0113] The helix device 100 of the fifth embodiment operates in a similar manner to the earlier described embodiment of FIG. 4. As shown in that drawing, the pads 40 are arranged in a formation which is functionally similar to the helix of the fifth embodiment. Similarly, the silicone of the fifth embodiment which is located on the internal surface of the helix provides cushioning against the external wall of the vessel, in a similar manner to the pads 40 of the first to fourth embodiments.

Sixth Embodiment

[0114] A sixth embodiment of the device 200 is depicted in FIGS. 12 to 16, being a variation on the fifth embodiment 100. The device 200 has a generally helical body or cuff 210, and in a similar manner to the earlier described embodiments, the device 200 is intended to be externally placed around the outside of the common carotid artery or the internal carotid artery (or another suitable vessel).

[0115] The radially inner wall of the cuff 210 may be smooth or textured.

[0116] The device 200 has a helical profile, so that it can be placed around the vessel 20 with minimal disturbance during a surgical procedure, with the elasticity of the device 200 permitting the vessel 20 to be seated radially within the central passageway 25 extending longitudinally through the helix.

[0117] The device 200 includes a central spine 220 fabricated from an elastically deformable material such as medical grade Nitinol?, stainless steel, or another suitable metal, metal alloy or polymer. The spine 220 is sheathed in a covering of silicone 230, or another biocompatible polymer. The silicone covering 230 is compliant, may contain and/or release a drug and reduces the risk of any damage to the external wall of the vessel 20.

[0118] Referring to FIG. 12 for example, a tensioning wire or cable 240 extends through the helix, adjacent to the central spine 220. In the preferred embodiment, the tensioning wire 240 is secured to the central spine 220 with a number of spaced anchoring points 250. The anchoring points 250 may be provided in various different forms, such as lugs 250 with eyelets to receive the wire 240. Similarly, the tensioning wire 240 may be passed through the centre of a hollow spine 220.

[0119] Referring to FIGS. 14 and 15, the cable 240 has an adjustment mechanism 260 located at one end of the device 200. The adjustment mechanism 260 may be in the form of an interacting thread and nut, a worm drive, a hose clamp type slotted screw, or some other mechanism which is configured to selectively mechanically shorten the length of the cable 240. By shortening the cable 240, because the cable is attached to the central spine 220 at each end, and intermittently with the anchoring points 250, shortening of the cable 240 results in the helix being reduced in length and increased in diameter. This has the effect of radially expanding the device 200 around the vessel.

[0120] The radial expansion or compression of the helix may be performed manually during installation, or alternatively, it may be performed remotely or mechanically in a post-operative procedure, as will be discussed below. For example, the cable 240 can be intermittently or occasionally adjusted, for example remotely or mechanically in a keyhole surgical procedure. Such adjustment can be performed to accommodate changes in the vessel, changes in the patient's blood flow characteristics or for any other purpose.

[0121] Referring to FIG. 12, the device 200 includes a radio component 280 and a copper coil winding 290, or other such antennae.

[0122] The radio component can receive signals, such as directing the helix to expand or contract in diameter.

[0123] Referring to FIG. 13, the device 200 also includes tabs 300 that contain sensors that oppose other relevant components located on the helix, such that measurements can be taken on diametrically opposing sides of the helix. One such component may be a mirror or reflector 320 for ultrasound purposes, or an LED receiver 330.

[0124] Various sensors or communication devices may be provided on the spine 220 or sheathed covering of silicone 230, such as platinum electrodes, 340, a pressure sensor 360, an ultrasonic emitter 380.

[0125] In the preferred embodiment, the electrodes 340 and the pressure sensor 360 extend radially inwardly through the surface of the silicone covering 230, such that the electrodes 340 and the pressure sensor 360 can be placed into direct contact with the wall of the blood vessel 20.

[0126] Referring to FIG. 15, the central spine 220 may be fabricated from a sandwiched nitinol helix 400.

[0127] The sensors and adjustment mechanism of the device 200 may be controlled by a printed circuit board (PCB), such as the doubled-up flex PCB 410 depicted in FIG. 15.

[0128] In each of the embodiments described herein, the cuff 10 is typically around 40-50 mm in length, although it may be longer or shorter.

[0129] The vessel 20 when treated with the device of each of the 1.sup.st to 4.sup.th embodiments described above may be reduced in diameter by about 3% to 30%, and preferably about 5% to 15% and most preferably about 10% by each pad.

[0130] In the embodiments of FIGS. 2 to 6, changing the internal diameter of the device 15, 50, 55, 60 may be achieved by changing the dimensions of the silicone covering 130. In the embodiments of FIGS. 7 to 16, changing the internal diameter of the helix may be achieved by changing the dimensions (in particular the thickness) of the silicone covering 120 or the dimensions of the spine 130.

[0131] In addition, changing the internal diameter can be achieved by a mechanism such as cable foreshortening, for example as described with respect to the sixth embodiment.

[0132] It will be appreciated that the cross-section of the silicone covering 130 may be constant between the proximal and distal ends. Alternatively, the cross-section of the silicon covering 130 may vary between the proximal and distal ends. Similarly, there may be variation of cross-section of the central spine 220, which is preferably fabricated from Nitinol.

[0133] Advantageously, when placed around a vessel 20 such as the carotid artery, the cuff 10 does not significantly affect the blood flow rate, as the auto-regulation of the blood flow assists in maintaining the natural volumetric blood flow rate.

[0134] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.