Patent Description:
Balloon dilatation (angioplasty) is a common medical procedure mainly directed at revascularization of stenotic vessels by inserting a catheter having a dilatation balloon through the vascular system. The balloon is inflated inside a stenosed region in a blood vessel in order to apply radial pressure to the inner wall of the vessel and widen the stenosed region to enable better blood flow.

In many cases, the balloon dilatation procedure is immediately followed by a stenting procedure where a stent is placed to maintain vessel patency following the angioplasty. Failure of the angioplasty balloon to properly widen the stenotic vessel, however, may result in improper positioning of the stent in the blood vessel. If a drug-eluting stent is used, its effectiveness may be impaired by such improper positioning and the resulting restenosis rate may be higher. This is a result of several factors, including the presence of gaps between the stent and the vessel wall, calcified areas that were not treated properly by the balloon, and others.

Conventional balloon angioplasty suffers from a number of other shortcomings as well. In some cases the balloon dilatation procedure causes damage to the blood vessel due to aggressive balloon inflation that may stretch the diseased vessel beyond its elastic limits. Such over inflation may damage the vessel wall and lead to restenosis of the section that was stretched by the balloon. In other cases, slippage of the balloon during the dilatation procedure may occur. This may result in injury to the vessel wall surrounding the treated lesion. One procedure in which slippage is likely to happen is during treatment of in-stent restenosis, which at present is difficult to treat by angioplasty balloons. Fibrotic lesions are also hard to treat with conventional balloons, and elastic recoil is usually observed after treatment of these lesions. Many long lesions have fibrotic sections that are difficult to treat using angioplasty balloons.

An additional problem associated with balloon angioplasty treatment has been the "watermelon seed effect. " Angioplasty is carried out at very high pressures, typically up to twenty atmospheres (<NUM>,<NUM> kPa) or higher, and the radially outward pressure of the balloon can cause axial displacement of the balloon in a manner similar to squeezing a watermelon seed with the fingers. Such axial displacement, of course, reduces the effectiveness of balloon dilatation. Another problem with conventional angioplasty balloon design has been deflation of the balloon. Even after the inflation medium is removed from a balloon, the deflated configuration will have a width greater than the original folded configuration which was introduced to the vasculature. Such an increase in profile can make removal of the balloon difficult.

Atherectomy/Thrombectomy devices intended to remove plaque/thrombus material may also include a structure that expands in a lesion while the plaque/thrombus removal mechanism is within this structure. The removed material is either being stacked in the catheter or sucked out thru the catheter. When the procedure is done, the expandable structure is collapsed and the catheter removed. Foreign object removal devices usually include a basket structure that needs to be expanded to collect the object and then collapse for retrieval. Distal protection devices usually include a basket structure that support a mesh that needs to be expanded distal to the treated lesion to collect the loose objects and then collapse for retrieval.

These devices usually include an elastic metallic material that needs to be expanded in the vascular system to fulfill its task and afterwards collapse to a small diameter to facilitate retrieval. The transition between the collapsed (closed) configuration to the expanded (open) configuration can be done in two ways: the structure can be at a normally closed (collapsed) configuration in which force is applied to cause the structure to expand. In this case, the elastic recoil of the structure will cause it to collapse back to closed configuration when the expanding force ceases. The structure may also be at a normally open (expanded) configuration in which a constraining element is forced over it to hold it down for the collapsed configuration (for example a constraining tube). When this constraining element is removed the structure is free to expand to the expanded (open) configuration. The structure material may also be non-elastic. In this case, the structure will need to be forced to transit between both collapsed and expanded configurations.

According to its abstract, <CIT>, relates to treating valve stenosis and describes a valvuloplasty catheter that comprises a balloon or other expansible shell which carries a plurality of scoring elements, typically formed in an elastic, self-closing metal cage. The expansible shell and scoring elements are positioned inside an aortic or other cardiac valve, and the shell expanded to engage the scoring elements against stenotic material which covers the valve leaflets and valve annulus. The scoring elements uniformly distributed force to break up the stenotic material, and the cage further contributes to rapid balloon deflation allowing shortening of the treatment time.

According to its abstract, <CIT> relates to a cutting balloon assembly and describes a method for fabrication of a cutting balloon assembly that includes providing a predetermined number of filaments having predetermined properties, diameter and length and fabricating a scoring mesh on a weaving jig having a plurality of pins disposed circumferentially about the jig's surface. The fabrication of the scoring mesh includes placing the filaments between the pins and interlacing the filaments to form a scoring mesh by interweaving and intertwining at least a part of filament to form one or more permanent links with neighboring filaments. The fabrication of the scoring mesh also includes forming distal and proximal filament loops that protrude from the mesh distal and proximal ends, respectfully. The scoring mesh is mounted on an expandable balloon mounted on a distal end of a delivery catheter.

<CIT> discloses an angioplasty balloon including a non-deployable stent to prevent or reduce the potential slippage of the inflated balloon with respect to the vessel wall being treated, the non-deployable stent is secured to the balloon or angioplasty balloon catheter. The non-deployable stent is made of a Nitinol structure that comprises a laser cut hypo tube which expands upon inflation of the balloon, but collapses upon deflation of the balloon because of the super-elastic properties of the Nitinol material, rather than remains expanded in the deployed condition, as would stents in general. The non-deployable stent has a proximal end, a distal end, and at least three radially-spaced struts, each strut extending longitudinally and connecting the proximal end to the distal end and having one or more bends that allow expansion of the strut to accommodate the inflation of the balloon. The stent is made of a material so that the stent collapses upon deflation of the balloon. At the longitudinal center of the hypo tube, a U-shaped circumferential connector joins each strut to its adjacent strut.

<CIT> discloses an angioplasty catheter comprising a catheter body having a balloon at its distal end. A helical cage structure which floats over the balloon is carried over the shell and scores a stenosed region in a blood vessel when the balloon is inflated therein. The catheter has an attachment structure disposed between the catheter body and the balloon to accommodate foreshortening and rotation of the external structure as the balloon is expanded.

One problem associated with conventional angioplasty expansion systems is that the transition between the collapsed and expanded configurations involves significant rotational and axial reaction forces. These reaction forces are applied by the structure on the catheter as a result of the force applied by the catheter to expand or close the structure. Axial reaction forces are created due the foreshortening of the structure during expansion. Rotational reaction forces (torques) are created when a non-longitudinal element is forced to expand/collapse. Since the catheters are usually less stiff than the structure, these reaction forces may cause the structure to not expand or collapse properly, or cause undesired deformation to the catheter itself.

For these reasons, it would be desirable to provide improved cutting or scoring balloon designs and methods for their use. In particular, it would be desirable to provide cutting or scoring balloons which are highly flexible over the length of the balloon structure, which readily permit deflation and facilitate removal from the vasculature, and which are effective in treating all forms of vascular stenoses, including but not limited to treatment of highly calcified plaque regions of diseased arteries, treatment of small vessels and/or vessel bifurcations that will not be stented, treatment of ostial lesions, and treatment of in-stent restenosis (ISR). Moreover, it would be desirable if such balloon structures and methods for their use could provide for improved anchoring of the balloon during dilatation of the stenosed region.

It would further be desirable to minimize the reaction forces applied by the external structure to the catheter, and at the same time be able to control the expansion of the expandable structure. It would also be desirable to adjust the compliance and improve the shape stability of the system in a predictable way without changing the materials or geometry of the expandable structure. At least some of these objectives will be met with the inventions described hereinafter.

The object of the present invention is solved by the subject-matter of the independent claim <NUM>; further embodiments are incorporated in the dependent claims. The present invention provides improved apparatus for the dilatation of stenosed regions in the vasculature. The stenosed regions will often include areas of fibrotic, calcified, or otherwise hardened plaque or other stenotic material of the type which can be difficult to dilatate using conventional angioplasty balloons. The apparatus will often find their greatest use in treatment of the arterial vasculature, including but not limited to the coronary arterial vasculature, but may also find use in treatment of the venous and/or peripheral vasculature, treatment of small vessels and/or vessel bifurcations that will not be stented, treatment of ostial lesions, and treatment of ISR.

In an example, provided for explanation, a method, not forming part of the present invention, of dilating a stenosed region in a blood vessel is disclosed. The method includes introducing a helical scoring structure having a distal end and a proximal end carried over a balloon, wherein the helical scoring structure comprises a plurality of helical elements that longitudinally extend from the distal end to the proximal end, and a plurality of stabilizing struts spaced along the length of the helical scoring structure and coupled to at least two adjacent helical elements, expanding the balloon to dilate the helical scoring structure within the stenosed region within the blood vessel, wherein the proximal end of the helical scoring structure, which is free to move axially, moves distally and the scoring structure shortens to accommodate such distal movement of the helical scoring structure as the balloon is expanded; holding the expanded helical scoring structure in place to disrupt the stenoses; and deflating the balloon causing the helical structure to collapse. The stabilizing struts enhance the ability of the scoring structure to maintain its desired shape.

The helical scoring structure means that the structure will be able to score or cut stenotic material within a treated blood vessel along lines which are generally in a non-axial direction. For example, the scoring lines may be helical, serpentine, zig-zag, or may combine some axial components together with such non-axial components. Usually, the non-axial scoring pattern which is imparted will include scoring segments which, when taken in total, circumscribe at least a majority of and usually the entire inside wall of the blood vessel up to one time, preferably more than one time, usually more than two times, often at least three times, more often at least four, five, six, or more times. It is believed that the resulting scoring patterns which circumscribe the inner wall of the vessel will provide improved results during subsequent balloon dilatation.

Usually the scoring structure will comprise at least one continuous, i.e., non-broken, scoring element having a length of at least <NUM>, more usually at least <NUM>, often at least <NUM>, usually at least <NUM>, and sometimes at least <NUM> or more. Alternatively, the scoring structure may comprise a plurality of much smaller segments which may be arranged in a helical or other pattern over the balloon, typically having a length in the range from <NUM> to <NUM>, often being <NUM> or less, sometimes being <NUM> or less. Additionally, the scoring structure elements may be adjoined to one another with one or more stabilizing struts. Rather than to extend along the entire length of the scoring structure, the stabilizing struts are configured to couple one scoring element with an adjacent scoring element.

In order to promote scoring of the blood vessel wall when the underlying expandable shell is expanded, the scoring structure will usually have a vessel contact area which is <NUM>% or less of the area of the expandable shell, usually being below <NUM>%, and often being in the range from <NUM>% to <NUM>% of the area of the expandable shell. The use of a shell having such a relatively small contact area increases the amount of force applied to the vascular wall through the structure by expansion of the underlying expandable shell. The scoring structure can have a variety of particular configurations, often being in the form of a wire or slotted tube having a circular, square, or other cross-sectional geometry. Preferably, the components of the scoring structure will comprise a scoring edge, either in the form of a honed blade, a square shoulder, or the like. A presently preferred scoring edge is electropolished and relatively small.

In a preferred embodiment, the scoring structure may be formed as a separate expandable cage which is positioned over the expandable shell of the catheter. The cage will usually have a collar or other attachment structure at each end for placement on the catheter body on either side of the expandable shell. A collar may be a simple tube, and other attachment structures will usually be crimpable or otherwise mechanically attachable to the catheter body, such as a serpentine or other ring structure. The attachment structures on the cage may be attached at both ends to the catheter body, but will more usually be attached at only a single end with the other end being allowed to float freely. Such freedom allows the scoring structure to shorten as the structure is expanded on the expandable shell. In certain embodiments, both ends of the scoring structure will be fixed to the catheter body, but at least one of the attachment structures will have a spring or other compliant attachment component which provides an axial extension as the center of the scoring structure foreshortens.

In many cases, since the scoring elements are non-axial, there are torques induced during the expansion of the balloon and the shortening of the scoring structure. These torques may be high, and if one end of the scoring structure is constrained from rotation, the scoring element will not expand properly. The final expanded configuration of the scoring element is achieved via shortening and rotation.

In a preferred embodiment, both sides of the scoring element are fixed to the catheter, but at least one side will have a compliant structure which will provide axial tension and at the same time will allow the scoring element to rotate to its final configuration.

In some cases both ends of the scoring element are fixed and the shortening is achieved by deformation of the wire. For example, the wire can have a secondary structure which permits elongation (e.g., it may be a coiled filament) or can be formed from a material which permits elongation, e.g., nitinol. The scoring element can be attached in both ends, in a way that will allow rotation. In the case were the torques are low (depending on the design of the scoring element) there is no need for rotation and the torque can be absorbed either be the scoring element or by the catheter.

In all cases, the scoring structure is preferably composed of an elastic material, more preferably a super elastic material, such as nitinol. The scoring structure is thus elastically expanded over the expandable shell, typically an inflatable balloon similar to a conventional angioplasty balloon. Upon deflation, the scoring structure will elastically close to its original non-expanded configuration, thus helping to close and contain the balloon or other expandable shell.

In some cases the scoring element will be a combination of more than one material. In one case the scoring element can be made from nitinol and parts of it can be made from stainless steel. In other cases the scoring element can be made of stainless steel or nitinol and part of it can be made from polymer to allow high deformations.

In other preferred embodiments, the assembly of the shell and the scoring structure will be sufficiently flexible to permit passage through tortuous regions of the vasculature, e.g., being capable of bending at radius of <NUM> or below when advanced through <NUM>°, <NUM>°, or higher bends in the coronary vasculature. Usually, the scoring structure will comprise one or more scoring elements, wherein less than <NUM>% of the cumulative length of the scoring element is aligned axially on the shell when expanded, preferably being less than <NUM>% of the cumulative length, and more preferably being less than <NUM>% of the cumulative length. In other instances, the scoring structure may comprise one or more scoring elements, wherein the cumulative length of the scoring element includes a non-axial component of at least <NUM>, preferably at least <NUM>, and more preferably <NUM>. Preferably, at least some of the scoring elements will have scoring edges which are oriented radially outwardly along at least a major portion of their lengths at all times during inflation and deflation and while inflated. By "radially outward," it is meant that an edge or shoulder of the element will be oriented to score the stenotic material or the interior wall of the treated vessel, particularly as the shell is being inflated.

The scoring elements will usually, but not necessarily, have a scoring edge formed over at least a portion of their lengths. A "scoring edge" may comprise a rounded or square such as found on a wire. The scoring elements will concentrate the radially outward force of the balloon to cause scoring or other disruption of the plaque or other stenotic material being treated.

In an embodiment of the present invention, the scoring catheter comprises a catheter body and a radially expandable shell, generally as set forth above. The scoring catheter includes a helical scoring structure having a distal end and a proximal end carried over a balloon, wherein the helical scoring structure is configured to radially expand in response to balloon inflation and further comprises a plurality of helical elements that longitudinally extend from the distal end to the proximal end, and a plurality of stabilizing struts spaced along the length of the helical scoring structure and coupled to at least two adjacent helical elements, and a catheter body configured to carry the helical scoring structure at a distal end.

In the present invention, an expansible scoring cage, as defined in claim <NUM>, adapted to be carried over a balloon of a balloon catheter is disclosed. The expansible scoring cage includes an assembly having a plurality of helical scoring elements, wherein said assembly is normally in a radially collapsed configuration and expansible over a balloon to a radially expanded configuration, wherein the assembly returns to its radially collapsed configuration when the balloon is deflated; further wherein the plurality of helical scoring elements are coupled to each other via a plurality of stabilizing struts along the longitudinal length of the helical scoring elements.

An elongated scoring structure is carried over the shell, and the assembly of the shell and the scoring structure will be highly flexible to facilitate introduction over a guide wire, preferably being sufficiently flexible when unexpanded so that it can be bent at an angle of at least <NUM>°, preferably <NUM>°, at a radius of <NUM> without kinking or otherwise being damaged. Such flexibility can be determined, for example, by providing a solid cylinder having a radius of <NUM> and conforming the assembly of the scoring structure and expandable shell over the cylinder. Alternatively, the assembly can be advanced over a guide wire or similar element having a <NUM>° one centimeter radius bend. In either case, if the assembly bends without kinking or other damage, it meets the requirement described above. Other specific features in this further embodiment of the catheters of the present invention are as described above in connection with the prior embodiments.

In an embodiment the scoring cage comprises an assembly of one or more elongate elastic scoring elements arranged in a non-axial pattern. As defined above, the non-axial pattern may comprise both axial and non-axial segments. The assembly is normally in a radially collapsed configuration and is expandable over a balloon to a radially expanded configuration. After the balloon is deflated, the assembly returns to a radially collapsed configuration, preferably being assisted by the elastic nature of the scoring cage and a series of stabilizing struts. Advantageously, the scoring cage with stabilizing struts will enhance uniform expansion of the underlying balloon or other expandable shell and will inhibit "dog boning" where an angioplasty balloon tends to over inflate at each end, increasing the risk of vessel dissection. The scoring elements will be adapted to score hardened stenotic material, such as plaque or fibrotic material, when expanded by the balloon in a blood vessel lumen. The scoring cage may be adapted to mount over the balloon with either or both ends affixed to the balloon, generally as described above in connection with prior embodiments. Preferred geometries for the scoring elements include those which circumscribe the balloon, those which are arranged helically over the balloon, those which are arranged in a serpentine pattern over balloon and the like.

In yet another example, a method, not forming part of the present invention, for dilatating a stenosed region in a blood vessel comprises radially expanding a shell which carries a scoring structure. The scoring structure scores and dilates the stenosed region and includes one or more non-axial scoring elements arranged to impart a circumscribing score pattern about the inner wall of the blood vessel as the shell is expanded. The stenosed region is typically characterized by the presence of calcified plaque, fibrotic plaque, or other hardened stenotic material which is preferably scored prior to dilatation. Preferably, the scoring structure will not be moved in an axial direction while engaged against the stenosed region, and the scoring structure may optionally be free from axially scoring elements.

In an embodiment of the present invention, an angioplasty catheter comprises a catheter body and a radially expandable shell near the distal end of the catheter body. An external structure, such as a scoring structure or cutting structure, is carried over but unattached to the shell. The catheter further comprises an attachment structure having a proximal end and a distal end attached to the scoring structure, wherein the attachment structure is sufficiently sized and compliant to accommodate reaction forces or geometrical changes produced by the scoring structure as it is expanded by the shell. Generally, at least a portion of said scoring structure is arranged helically over the shell. However, the scoring structure may comprise numerous different configurations as described above.

In one embodiment of the present invention, the proximal end of the attachment structure is fixed to the catheter body and the distal end of the attachment structure is secured to the proximal end of the scoring structure. In all cases, the attachment structure is capable of axially and rotationally extending to accommodate foreshortening of the scoring structure as the shell is expanded.

It is understood that other embodiments of the specific teachings herein will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described only several embodiments of the teachings by way of illustration. As will be realized, the subject matter of the teachings herein is capable of other and different embodiments and its several details are capable of modification in various other respects, all without departing from the scope of these teachings.

In the following description, various aspects of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details presented herein. Furthermore, well-known features may be omitted or simplified in order not to obscure the present invention.

Embodiments of the present invention relate to a device for revascularization of stenotic vessels and specifically to a balloon catheter having external scoring elements. The dilatation device comprises a conventional dilatation balloon such as a polymeric balloon and a helical scoring structure. Alternatively, other scoring configurations may be mounted on the balloon catheter without departing from the teachings disclosed herein.

Reference is now made to <FIG>, <FIG>, which are schematic illustrations of a dilatation device <NUM> in accordance with embodiments described herein. The dilatation device <NUM> includes a dilatation balloon <NUM>, which may be any conventional angioplasty balloon such as commonly used by interventional cardiologists or radiologists, and a helical assembly <NUM> mounted over or attached to the dilatation balloon <NUM>. The helical assembly <NUM> also includes at least one stabilizing strut <NUM> that couples one longitudinal strut to an adjacent longitudinal strut, as depicted in <FIG>. Preferably, the helical assembly <NUM> will incorporate a series of stabilizing struts that extend about the longitudinal length of the helical assembly <NUM>. For added stability, the stabilizing struts <NUM> may be spaced evenly or unevenly along the longitudinal axis of the helical assembly <NUM>. Helical unit <NUM> may be attached at <NUM> and <NUM> to the catheter shaft proximate to proximal and distal ends of the balloon <NUM> by collar- like attachments <NUM> and <NUM> (See <FIG>).

The stabilizing struts <NUM> may additionally provide for the long scoring elements of the helical assembly <NUM> to deploy in an evenly spaced manner during balloon inflation to various pressures. The stabilizing struts <NUM> may also minimize the possibility that the scoring element struts or wires will bunch together during device operation, and, still further, assist with keeping the scoring elements from lifting from the balloon surface at its deflated state, thereby facilitating device pull back. In other words, as will be appreciated by one of ordinary skill, the incorporation of stabilizing struts <NUM> may create a stable support structure between the otherwise independently floating struts (See <FIG>). The stabilizing strut(s) <NUM> may have at least one bend along its path extending from one scoring element to an adjacent scoring element - or the same scoring element in the single wire embodiment. The at least one bend, preferably at least two, would facilitate maintaining the narrow profile of the collapsed helical structure for unobstructed removal of the catheter from the body lumen post-treatment. Moreover, the points at which the stabilizing strut <NUM> meets the two adjacent helical elements may be typically offset along the longitudinal axis to accommodate the expanded and collapsed configurations without having any helical scoring elements or stabilizing struts detach or otherwise stray from the scoring structure's profile.

Further, the compliance of the balloon and the scoring element(s) should be chosen to assure uniform expansion of the balloon substantially free from "dog-boning" as the combined structure expands within a lesion. If a compliant or a semi-compliant balloon is used and the compliance of the scoring element was not matched to comply with the properties of the balloon, the expansion of the balloon-scoring element system will not be uniform. This non-uniformity may impair the efficacy of the scoring catheter and, in some cases, may result in poor performance. For example, under given pressure, certain parts of the balloon <NUM> will be able to expand while other parts will be constrained by excessive resistance of the scoring elements.

The helical unit or assembly <NUM> is typically made of nitinol. Helical unit <NUM> may be made of other metals such stainless steel, cobalt-chromium alloy, titanium, and the like. Alternatively, helical unit <NUM> may be a polymeric helix, or made of another elastic material. Helical unit <NUM> may be attached at its proximal and distal ends to the catheter shaft proximate to the proximal end <NUM> and distal end <NUM> of dilatation balloon <NUM>. Alternatively, helical unit <NUM> may be attached to the catheter shaft proximate to the distal end and/or the proximal end of dilatation balloon <NUM> by collar-like attachment elements <NUM> and <NUM>. (See <FIG>). Still further, one or both collar- like attachments <NUM> and <NUM> may be free to slide on the catheter shaft. Spring or other compliant elements may be alternatively or additionally provided as part of the attachment elements to accommodate shortening of the helical unit <NUM> as it is expanded.

Dilatation device <NUM> is inserted into the vascular system, for example, using a conventional catheter procedure, to a region of stenotic material <NUM> of blood vessel <NUM>. (The term "stenotic" is used herein to refer to the vascular lesion, e.g., the narrowed portion of the vessel that the balloon is meant to open. ) At the stenotic area <NUM>, the dilatation balloon <NUM> is inflated, for example, by liquid flow into the balloon. Helical unit <NUM> widens on the inflated dilatation balloon <NUM>. On inflation, the dilatation balloon <NUM> together with the helical unit <NUM> is pressed against the walls of blood vessel <NUM> as shown in <FIG>.

Reference is now made to <FIG>, illustrating blood vessel <NUM> after the deflation of dilatation balloon <NUM>. Helical unit <NUM> narrows when deflating the dilatation balloon <NUM>, thus the dilatation device <NUM> is narrowed and may be readily retrieved from blood vessel <NUM>. The deflation profile of the balloon <NUM> is low and mainly circular. The stenotic material <NUM> in blood vessel <NUM> is pressed against blood vessel <NUM> walls to widen the available lumen and enhance blood flow. The pressing of helical unit <NUM> against the walls of blood vessel <NUM> causes scoring <NUM> in the stenotic area.

Helical unit <NUM> may be pushed outwardly by the inflation of the balloon <NUM>, and is stretched by the inflation of the balloon. When the balloon is deflated, helical unit <NUM> assists in the deflation by its elastic recoil. This active deflation is faster and also leads to a low profile of the deflated balloon. The balloon <NUM> is disposed within the helical unit <NUM>, which returns to its pre-inflated shape and forces the balloon to gain a low radial profile.

In another embodiment of the invention, dilatation device <NUM> may carry a stent. The stent can be crimped over the helical unit <NUM>. In this way, the helical unit <NUM> can push the stent against hard areas of the lesion, enabling proper positioning of the stent against the vessel wall, even in hard-calcified lesions without pre-dilation.

Reference is now made to <FIG>, illustrating the helical unit <NUM> in accordance with embodiments of the invention. Helical unit <NUM> is typically made of nitinol. Helical unit <NUM> includes but is not limited to three wires <NUM> that are attached to collars <NUM> and <NUM> at the proximal end and distal end, respectively. As depicted in connection with <FIG>, stabilizing struts <NUM> are coupled between adjacent scoring elements, in this embodiment, wires <NUM>. Alternatively, the scoring structure may comprise wires of other elements attached directly to the balloon material or close to the balloon ends.

Wires <NUM> are attached between collars <NUM> and <NUM>. The diameter of the wires is typically in the range of <NUM> to <NUM>. Alternatively, a cage (for example a metallic cage made of a slotted tube) can be used in several configurations that allow local stress concentrations. The size and shape of the cross section of the cage elements or the cross section of the wires can vary. The cross section can be a circle, rectangle, triangle, or other shape.

In alternative embodiments, the wires <NUM> may comprise short segments that are attached to the balloon <NUM>. In further alternative embodiments of the invention, the helical unit <NUM> may be glued, thermally bonded, fused, or mechanically attached at one or both ends to the dilatation balloon <NUM>. In yet another embodiment, a scoring structure may comprise wires that are attached to the dilatation balloon <NUM> in a helical configuration or other configuration. The wires may be thermally attached to the balloon <NUM>, glued, mechanically attached, or the like. In still another embodiment, a scoring structure comprises wire or cage elements that are not parallel to the longitudinal axis of the balloon <NUM> so that the combination of the scoring structure <NUM> and the balloon <NUM> remains flexible.

In additional embodiments, the combination of dilatation balloon <NUM> and scoring structure scores the lesion and provides better vessel preparation for drug eluting stents by allowing better positioning of the stent against the vessel wall and diffusion of the drug through the scores in the lesion. In these embodiments, the balloon can be used as a platform to carry drugs to the lesion where scoring of the lesion can enhance delivery of the drug to the vessel wall. The balloon may then be used for local drug delivery by embedding drug capsules, drug containing polymer, and the like, through the stenotic material and into the vessel wall.

The scoring structures may be attached directly to the balloons or other shells, in some cases being embedded in the balloon material, but will more usually be formed as separate cage structures which are positioned over the balloon and attached to the catheter through attachment elements on either side of the balloon. The expandable cages may be formed using conventional medical device fabrication techniques, such as those used for fabricating stents, such as laser cutting of hypotube and other tubular structures, EDM forming of hypotubes and tubes, welding of wires and other components and the like.

Typically, such expandable shell structures will comprise the attachment elements and an intermediate scoring section between the attachment elements. As illustrated in the embodiments above, the attachment elements may be simple cylindrical or tube structures which circumscribe the catheter body on either side of the balloon or other expandable shell. The simple tube structures may float over the catheter body, i.e., be unattached, or may be fixed to the catheter body. A number of alternative embodiments for the attachment elements will be described in connection with the embodiments below.

The intermediate scoring sections may also have a variety of configurations where at least some of the scoring elements will typically be disposed in a non-axial configuration, i.e., in a direction which is not parallel to the axial direction of the expandable cage. A preferred configuration for the intermediate scoring section comprises one or more helical elements, generally as illustrated in the prior embodiments. Other exemplary configurations are set forth in the embodiments described below.

Reference is now made to <FIG>, example not being part of the invention, that shows a scoring structure in the form of a single wire <NUM> wrapped around a dilatation balloon <NUM> in a helical configuration. Additionally, with respect to the single wire <NUM> embodiment, stabilizing struts <NUM> may be disposed either randomly or evenly throughout the entire length of the helical unit <NUM> for added stability in the expansion and collapse of the helical scoring unit. As depicted by the spaces in <FIG>, <FIG>, the helical assembly may be of any longitudinal length appropriate for the treatment site. The incorporation of stabilizing struts <NUM>, however, may be most beneficial on either a relatively long helical assembly, e.g., any scoring structure longer than <NUM>, or a relatively short helical assembly that is designed to accommodate a balloon having a large diameter. For example, long scoring elements may be preferable when used to specifically address long, diffuse lesions of the femoro-popliteal arteries where a <NUM>-<NUM> scoring structure may be desirable - leading to fewer inflations and reduced procedure times. Conversely, short scoring elements on a <NUM>-<NUM> catheter may be preferable when used to treat a lesion within a large diameter vessel, requiring a balloon having a diameter of between <NUM>-<NUM>. With the addition of stabilizing struts to the helical assembly, the design and manufacture of lengthy and/or large diameter catheters becomes feasible.

Although the illustrated structure of an elastic metal, helical structure <NUM> may be preferred as it effectively maintains equal circumferential spacing of the scoring elements <NUM> as the shell <NUM> is inflated or otherwise expanded, other helical designs may be employed, such as those having a plurality of helical scoring elements, as illustrated in <FIG>. In <FIG>, a cage <NUM> comprising six helical scoring elements <NUM>, and a series of stabilizing struts <NUM>, is disposed over an inflatable balloon <NUM>. The construction of the catheter which carries balloon <NUM> and cage <NUM> will generally be the same as that described with respect to the foregoing description. <FIG> also describes an expansible cage <NUM> having a plurality of helical scoring elements <NUM>, and a plurality of stabilizing struts <NUM>, where the principal difference is that cage <NUM> includes twelve scoring elements in contrast to six scoring elements of <FIG>.

In other examples, the scoring structure can have a non-helical configuration. Any design of scoring structure that can accommodate an increase in the diameter of the balloon <NUM> upon inflation, and return to its configuration when the balloon is deflated, is an appropriate design. At least a portion of the scoring elements will not be parallel to the longitudinal axis of the balloon catheter to enhance flexibility and improve scoring.

Referring now to <FIG>, alternative attachment elements are shown on an embodiment of an expandable scoring cage <NUM> comprising three helical scoring elements <NUM>, supported by a plurality of stabilizing struts <NUM>, which make up the intermediate scoring section. A first attachment element <NUM> comprises a single serpentine ring, as best illustrated in <FIG> while a second attachment element <NUM> comprises a pair of tandem serpentine rings <NUM> and <NUM>, as best illustrated in <FIG>. The use of such serpentine attachment structures is beneficial since it permits crimping of either or both of the structures onto the catheter body in order to fix either or both ends of the structure thereto. Usually, the single serpentine attachment structure <NUM> will be affixed to the catheter body while the double serpentine structure will be left free to allow movement of that end of the scoring cage to accommodate radial expansion of the underlying balloon.

Referring now to <FIG>, a further alternative example of an attachment element useful in the scoring cages of the present invention is illustrated. Attachment element <NUM> includes a pair of serpentine rings <NUM> and <NUM>, generally as shown in <FIG>, in combination with a coil spring structure <NUM> located between said rings <NUM> and <NUM>. The coil spring structure <NUM> includes but is not limited to three nested coil springs <NUM>, each joining one of the bend structures <NUM> and <NUM> on the serpentine rings <NUM> and <NUM>, respectively. The spring like structure can take on many forms that allow for linear and rotational movement during expansion and retraction of the scoring cage. The structure of the spring structure and adjacent serpentine rings can be understood with reference to the rolled-out configuration shown in <FIG>.

The attachment structure <NUM> is advantageous since it permits a fixed attachment of the outermost ring <NUM> to the underlying catheter body while the inner ring <NUM> remains floating and expansion and contraction of the intermediate scoring section, comprising helical elements <NUM>, is accommodated by the coil spring structure <NUM>. Since the scoring cage is fixed to the catheter, any risk of loss or slippage from the balloon is reduced while sufficient compliance is provided to easily accommodate radial expansion of the intermediate scoring section. By attaching the structures <NUM> at at least one, and preferably both ends of the scoring cage, the risk of interference with a stent is reduced.

In some embodiments, collars, such as those shown in <FIG>, or attachment elements, such as those shown in <FIG>, may comprise a flexible material that allows the collar or attachment element to expand while being mounted over the balloon catheter and then be collapsed to the diameter of the catheter. The expandability of the collars and/or attachment elements may be achieved by a compliant memory material such as nitinol or a polymer, or by use of a flexible serpentine design as shown in <FIG>. Where collars are used, the collar may be shaped or have a slit down the circumference (not shown) so that the collar may be expanded during mounting over the balloon. Alternatively, the collar may be oversized to accommodate the balloon diameter mounting, and then crimped down to secure the secure the scoring structure to the catheter body.

The examples of <FIG> comprise a spring-like element <NUM> to accommodate axial shortening of the scoring structure upon radial expansion. It will be appreciated that other metal and non-metal axially extensible structures could also be used in such attachment structures. For example, elastic polymeric tubes could be attached at one end to the scoring structures and at another end to the catheter body (or to a ring, collar or other structure which in turn is fixed to the catheter body).

Claim 1:
An expansible scoring cage adapted to be carried over a balloon of a balloon angioplasty catheter, said cage comprising:
an assembly having a plurality of scoring elements arranged according to helical winding, said helical scoring elements, wherein the assembly is adapted to assume a radially collapsed configuration and adapted to expand to a radially expanded configuration, wherein the assembly is adapted to return to its radially collapsed configuration;
wherein the scoring cage has a distal end, a proximal end and wherein the plurality of helical scoring elements longitudinally extend from the distal end to the proximal end;
characterized in that the plurality of helical scoring elements are coupled via a plurality of struts comprising two bends in opposite directions, which struts connect two adjacent helical scoring elements at locations offset and spaced along the longitudinal axis of the expansible scoring cage to accommodate the radially expanded and the radially collapsed configurations, preventing any of the plurality of helical scoring elements or plurality of struts to detach or stray away from a profile of the expansible scoring cage upon axial and rotational reaction forces exerted to the expansible scoring cage during use.