FIELD OF THE INVENTION

This invention relates to an inflatable distender that may be inserted generally axially into a blood vessel, a bronchus, an oesophagus, gut or any other fluid, air or solid-transporting hollow organ of a patient in order to support and expand the organ walls, for example whilst, or as part of, a medical procedure being carried out.

The procedure may be carried out for a variety of different purposes such as transcatheter heart valve deployment, valvuloplasty, endovascular prosthesis delivery, and other procedures during which, for instance, some blood or air flow past the relevant site is to be maintained.

The invention also relates to a catheter that carries such an inflatable distender.

BACKGROUND TO THE INVENTION

Prior art devices of which applicant is aware include a mechanical stent placement device that forms the subject matter of published international patent application WO2010041 125. That device utilizes a plurality of elongate wings, each of which has a length consistent with the length of a stent to be deployed with the wings being arranged circumferentially about a central body and wherein the device is operable through a catheter. The wings are movable between a radially withdrawn delivery position and expanded positions in which they are displaced radially outwards of the body. A flow path is defined internally of the wings in the expanded positions thereof. The device supports an inflatable annular balloon over the wings that with the balloon being employed to cause radial expansion of a stent or other element carried by it or simply for the purpose of dilating a blood vessel for any appropriate purpose. That published patent application also provides an analysis of prior art known at that stage to those applicants as well as a description of general principles of placement of a stent and many of which are common to other intra vascular procedures. The content of that published application is incorporated herein by reference.

Prior US patent publication US5759172, on the other hand, describes an inflatable catheter device in which a balloon member has a number of relatively stiff sections extending on a small diameter in a longitudinal direction of the basic body of the balloon member and relatively pliable sections extending in between them. The relatively pliable sections are inflatable to form, in cross-section, lobes in an expanded state of the balloon member so that the flow of blood past the balloon may take place between the lobes in the regions corresponding to the relatively stiff sections of the balloon member.

Prior US patent publication US5797948 describes a catheter in which an inflatable catheter device has an inflatable inner balloon and an inflatable outer balloon in which the inner balloon when inflated serves to centre the catheter in the blood vessel.

US patent publication US6190356 describes an inflatable balloon device in which inflatable balloons follow a long pitch spiral with the flow of blood past the balloon taking place in spiral gaps between the inflated helical balloon elements. However, such a device does not and cannot provide for the passage of surgical equipment past the inflatable balloon device. US patent publication US 7,766,871 describes a rather similar device in the form of a balloon catheter system comprising one or more conduits to which is attached a compliant balloon having a non-helical shape in its deflated state and wherein said balloon is constructed such that it is capable of adopting a relatively long pitch spiral or helical configuration upon inflation. Blood flow past the balloon or balloons may take place through a spiral path that is formed between successive convolutions of balloon. A rather complicated formula is set out for calculating the geometry of the relatively long pitch spiral.

There is a need for an inflatable distender that is suitable for use in surgical applications in which, for instance, blood or air flow past the expanded balloon within the relevant blood vessel or other organ is to be maintained during a procedure or other medical treatment and wherein passage of surgical apparatus past the distended site may be required.

SUMMARY OF THE INVENTION

In accordance with a first aspect of this invention there is provided an inflatable distender comprising at least one inflatable support tube and wherein the inflatable distender has a collapsed condition in which the at least one inflatable support tube is collapsed to enable introduction and removal of the distender to and from an operative site in a vessel or other hollow organ of a patient and an inflated operative condition in which it assumes the form of an elongated tube extending in a generally spiral path along the length of the distender, the inflatable distender being characterised in that the at least one inflatable support tube in the inflated operative condition defines a self supporting spiral configuration of generally annular shape in cross-section with an inner diameter of the annular shape being equal to at least one diameter of the inflatable support tube so as to define a generally straight tubular flow passage through the distender between a proximal end and a distal end thereof. Further features of the invention provide for the inner diameter of the annular shape to be equal to from one to forty times the diameter of the inflatable support tube, preferably from two to twenty, and most preferably from three to thirteen times the diameter of the inflatable support tube; for the inflatable support tube to be in the form of a small diameter elongated tube capable of resisting pressures sufficient to provide adequate support to a distended vessel or other hollow organ of a patient during the conduct of a procedure, such pressures depending on the diameter of the inflatable support tube and being generally from about 5 bar up to about 30 bar or more so that it creates a suitably rigid structure; for the diameter of the tube forming the inflatable support tube to be, by way of non-limiting example, of the order of 0.8 to 4.0 millimetres with successive convolutions of the spiral in close proximity to each other, typically located at a helical pitch ranging from that corresponding to successive convolutions of the spiral touching each other or even being attached to each other to from a few millimetres to about 40 millimetres; and for the outer diameter of the annular shape of the inflated support tube to be selected according to the purpose to be served and generally from about 4 to about 30 mm, depending on the application and size of patient to be treated. Still further features of the invention provide for the at least one inflatable support tube to be associated with the inside of an outer inflatable balloon that also has a collapsed condition and an inflated condition and that can typically be inflated independently of the at least one inflatable support tube; for the outer inflatable balloon to be suitable for inflation at a pressure of up to about 5 bar, and possibly somewhat more, depending on the purpose being served; for the outer balloon to have a maximum outer diameter in the inflated condition of up to about 40 millimetres and typically between 18 and 30 millimetres; and for the at least one inflatable support tube to be attached to the inner surface of the outer inflatable balloon by any suitable means, including glue, ultrasonic welding, thermal bonding and other suitable attachment procedures. The at least one inflatable support tube may be a single or a multi-start tube wound from a proximal end to a distal end of the distender so as to form a single layer. Alternatively, the at least one inflatable support tube may be wound in more than one layer from the proximal end to the distal end and optionally back, with the helical pitch of different layers being either the same, in which case successive convolutions of various layers may be parallel, or with the helical pitch of different layers being different so that the convolutions of different layers cross each other at particular positions. Where there are more than one inflatable support tube they may be attached to each other by any suitable means, including glue, ultrasonic welding, thermal bonding and other suitable attachment procedures.

Furthermore, the diameter of any one or other inflatable support tube may itself vary along its length as can the inner diameter and pitch of the helical annular shape. A variable diameter of an inflatable support tube or the pitch of the helix or the diameter of the annular shape that the tubular flow passage through it follows may be particularly designed for dedicated applications in dilating particular vessels or other tubular or hollow organs. In all instances in which there are more than one inflatable support tube they may be arranged to be separately or jointly inflated.

In accordance with a second aspect of the invention there is provided a catheter having a catheter tube fitted at a distal end thereof with an inflatable distender as defined above and having at least one connection point at a proximal end thereof whereby inflating fluid can be conveyed to the inflatable distender by way of a lumen associated with the catheter tube.

In accordance with a third aspect of the invention there is provided a method of manufacturing an inflatable support tube for inclusion in an inflatable distender as defined above, the method comprising the steps of selecting a suitable heat shrink polymer tube wherein the diameter of the heat shrink polymer tube in an expanded condition is at least the desired final diameter of the inflatable support tube; introducing a removable and flexible or deformable support medium into the polymer tube, winding the combined heat shrink polymer tube and support medium around a forming tool in a generally helical path wherein the forming tool has a diameter required for producing the final helical inflatable support tube; heating the heat shrink polymer tube and support medium in a suitable heating environment to cause the heat shrink polymer tube to shrink or stretch to cause the polymer tube to conform to the helical shape; allowing the formed heat shrink polymer tube to cool with the support medium therein; and removing the support medium from the formed heat shrink polymer material to release an inflatable support tube.

In a first variation of the method defined above the support medium is an elongate flexible mandrel element that is threaded through the heat shrink tube with a suitable release surface being presented between the mandrel element and the heat shrink polymer tube.

Further features of the first variation of the method provide for the mandrel element to be made of a material that automatically provides a release characteristic between itself and the heat shrink polymer tube, conveniently a suitable silicone material; for the mandrel element to be in the form of an extruded tube; and for removal of the mandrel element to be facilitated by straightening the helical inflatable support tube and typically stretching the mandrel element to reduce its diameter, and/or in the instance that the mandrel element is a tube, by reducing the diameter of the silicone mandrel either in consequence of it having been pre-inflated in which instance it can be deflated, or by applying a negative pressure to the inside of the mandrel tube.

In a second variation of the method defined above, the support medium is a mass of loose elements or beads in which instance the heat shrink polymer tube itself with the beads inside it can be wound around a forming tool to the required helical configuration; heated and the cooled and, once the formed heat shrink polymer material has set in its helical condition, the loose elements or beads can be removed from the tube.

In a third variation of the method defined above the support medium may be a fluid such as air, water or any other suitable aqueous or organic fluid or molten material and the heat shrink polymer tube can be wound around the forming tool prior to heating and then cooling the heat shrink polymer tube and releasing the fluid therefrom.

Of course, it is also possible to use a combination of a mass of loose elements or beads and a fluid. Inflatable support tubes may be manufactured from any suitable material, such as polyethylene terephthalate (PET) or other suitable material. If the inflatable support tubes are manufactured using heat shrink materials by a procedure that is defined above, suitable materials may be selected from polyethylene terephthalate (PET) in particular, polyolefin, polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA), ethylene tetrafluoroethylene (ETFE), polyester, polyether ether ketone (PEEK), polyvinyl chloride (PVC) or even combination materials. Inflatable support tubes manufactured using other techniques may be made of materials, selected from silicones, latex, Kraton, thermoplastic elastomers such as styrene-ethylene/butylene-styrene block copolymers (SEBS), (SEBS)-based thermoplastic elastomers, polysiloxane modified SEBS and families of SEBS, PVC, cross-linked polyolefins such as polyethylene, and many different polyurethanes. Preferred materials are those known as semi- compliant or non-compliant (inelastic) materials which include polyamides (e.g. nylons), thermoplastic polyamides, polyesters, polyphenylene sulphides and PET. PET is especially interesting due to its capacity for easy production of very thin-walled inflatable support tubes. Nylons are also interesting due to their ability to be bonded easily using thermal bonding processes.

In order that the invention may be more fully understood various embodiments of the different aspects of the invention will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:-

Figure 1 is an isometric view of a catheter fitted with one embodiment of inflatable distender according to the invention collapsed condition;

Figure 2 is an isometric view of a catheter as illustrated in Figure 1 with the inflatable distender according to the invention in the inflated condition;

Figure 3 is a schematic elevation showing the catheter with the inflatable distender in a collapsed condition in a vessel in a patient;

Figure 4 is schematic elevation similar to Figure 3 but showing the inflatable distender in an inflated condition;

Figure 5 is a schematic end view of an inflatable distender in a collapsed condition illustrating broadly a folded nature thereof; Figure 6 is an isometric view of an end of a folded inflatable distender;

Figure 7 is an end view of the inflatable distender in the inflated condition clearly showing the annular shape of the inflated distender;

Figure 8 is an end view similar to Figure 5 but of an inflatable distender that has an outer inflatable balloon fitted to the inflatable distender;

Figure 9 is a schematic sectional elevation of an embodiment of the invention having an inflatable balloon fitted to the outside of the inflatable distender in the inflated condition ;

Figure 1 0 is a schematic end view of the inflated distender illustrated in Figure 9;

Figure 1 1 is an isometric view thereof in the inflated condition ;

Figure 1 2 is the same as Figure 9 but showing one variation thereof;

Figure 1 3 is a schematic elevation of a three start inflatable support tube in the inflated condition ;

Figure 14 is a schematic sectional elevation of the three start inflatable support tube illustrated in Figure 1 3;

Figures 1 5 to 21 each illustrate in schematic sectional elevation a different embodiment of inflatable support tube according to the invention ; Figure 22 is illustrative of the first variation of a method of manufacture according to the invention; and,

Figure 23 is illustrative of a second variation of method of manufacture according to the invention.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

Referring firstly to Figures 1 to 7 of the drawings, an inflatable distender comprises, in this instance, a three start inflatable support tube in which each separate tube (1 ) has its proximal end (2) connected by means of an individual supply tube (3) to a common lumen within a catheter tube (4) with the distal end (5) of the inflatable support tubes being closed off. The inflatable distender has a collapsed condition that is illustrated in Figures 1 and 3 in which the inflatable support tubes are collapsed and folded either systematically or randomly to enable introduction and removal of the distender to and from an operative site in a vessel (6) (see Figure 3) or other hollow organ of a patient. The inflatable distender also has an inflated operative condition in which it assumes the form of an elongated tube extending in a generally spiral or helical path along the length of the distender, as illustrated in Figures 2 and 4.

Where more than one inflatable tube is used to construct the inflatable distender it should be noted that the tube will be shorter which may facilitate manufacturing. As there is more than one inflation port (one for each start of the inflatable tube arrangement), faster inflation and deflation times result because smaller volumes of inflation medium are required to travel into and out of each of the inflatable tubes. The multiple-start construction also provides a factor of safety should one of the inflatable tubes become damaged during inflation or develop a kink that inhibits its inflation. As will be apparent from the drawings, the inflatable support tubes in the inflated operative condition define a self supporting spiral configuration of generally annular shape in cross-section with an inner diameter of the annular shape being equal, in this instance, to from three to four diameters of the inflated inflatable support tube. This arrangement defines a generally straight tubular flow passage (7) (see especially Figure 7) through the distender between a proximal end (8) and a distal end (9) thereof.

The inflatable support tubes are thus in the form of small diameter elongated tubes capable of resisting pressures sufficient to provide adequate support to a distended vessel or other tubular or hollow organ of a patient during the conduct of a procedure. The relevant pressures depend on the diameter of the tube and are generally from about 5 bar up to about 25 bar so that the inflated tube or tubes create a suitably rigid structure. In this instance the diameter of the tube forming the inflatable support tube may be of the order of 0.8 to 4 millimetres with successive convolutions of the spiral touching each other and preferably being attached together.

The outer diameter of the spiral support tube in the inflated condition is within the range of from about 6 to 30 mm, depending on the application and size of patient to be treated.

The support tube may be made of a variety of different materials as will be quite apparent from the foregoing as well as from what follows as regards the manufacture of the inflatable support tube. As a general rule the inflatable support tube will have a rather thin wall that could be of the order of 10 to 50μιτι, preferably from about 12μιη to 40μιτι, in the instance that a suitable heat shrink material is employed such as a suitable grade of heat shrink polyethylene terephthalate (PET). In one specific instance, the geometry of the helical support tube provided an overall internal diameter of 12.4mm; an overall outer diameter of 19mm with a helical support tube diameter of 3.3mm. When in the collapsed condition, and as shown especially in Figures 5 and 6, the collapsed inflatable support tube may be folded in numerous different ways such as in a type of pleated arrangement in which successive portions of the collapsed helical tube can be overlapped somewhat in the general manner illustrated in the Figures 5, 6 and 8 of the drawings. Numerous other formal or informal folding arrangements are possible so that the folded inflatable support tube assembly may adopt an overall diameter that enables it to be introduced into the necessary vessel or other tubular or hollow organ.

Turning now more particularly to Figures 8 to 1 1 of the drawings, the inflatable support tube is capable of resisting reasonably high pressures that are sufficient to provide adequate support to the inside of an outer inflatable balloon (1 1 ). It is envisaged that such pressures, depending on the diameter of the inflatable support tube itself and the outer diameter of the inflated helical support tube, could be of the order of about 16 to 25 bar. The inner support tube thus, in the inflated condition, creates a suitably rigid tubular structure that can serve as a core which is able to support the inside of the outer inflatable balloon.

The inner support tube will preferably be secured to the inside surface of the outer inflatable balloon and this may be achieved in any suitable way such as by means of glue, ultrasonic welding, thermal bonding or any other suitable technique.

The wall thicknesses of the annular balloon may, for example, be about 50μιτι when the wall thickness of the helical support tube is 12μιη to 40μιτι. Of course, it may be possible to use thinner wall thicknesses depending on the properties of the particular material from which the annular balloon and helical support tube are made.

In the instance that is illustrated in Figure 9 of the drawings, the diameter of a single start support tube may be about 0.8 millimetres with an outer diameter of the helix of about 13.6 millimetres. Successive convolutions of the helical support tube are relatively close together and in the embodiment of the invention illustrated in Figures 9 to 1 1 of the drawings with the pitch of the helix being about 2.6 millimetres.

In the instance of the embodiment illustrated in Figure 12, successive convolutions are further apart and are spaced at a pitch of about 5.2 millimetres. Clearly, the outer inflatable balloon also has a collapsed condition and an inflated condition and the outer inflatable balloon can typically be inflated independently of the inflatable support tube. In the collapsed condition the outer inflatable balloon can also be formally or informally folded or loosely pleated as is illustrated generally in Figure 8.

The inflation pressure is typically considerably less than the inflation pressure of the inflatable helical tube and the inflation pressure may range up to about 5 bar or higher. The outer balloon may have a maximum outer diameter in the inflated condition of up to about 40 millimetres and typically between 18 and 30 millimetres.

In all instances in which there are more than one inflatable support tube they may be arranged to be separately inflated or simultaneously inflated. As indicated above, and with reference to Figure 22 of the drawings, a method of manufacturing an inflatable support tube for inclusion in an inflatable distender as described above may include the steps of selecting a suitable expanded heat shrink polymer tube (1 3) wherein the expanded diameter of the heat shrink polymer tube is greater than the desired final diameter of the inflatable support tube; and threading an elongate flexible mandrel element (14) through the heat shrink tube. In the instance that the mandrel element is made of a suitable silicone, typically no release agent needs to be applied as the silicone surface automatically forms a suitable release surface. The mandrel element and heat shrink tubing thereon are then wound around a forming tool (1 5) having the required diameter and also possibly a suitable guide groove (not shown) for producing the final inflatable support tube. A guide groove is particularly helpful if the pitch of the helix provides a space between successive convolutions of the inflatable support tube.

The combination is then heated, typically in an oven, so that the heat shrink polymer tube shrinks into contact with the mandrel element. The combination is then allowed to cool so that the heat shrink polymer can set in its final position after which the mandrel element is removed from the formed heat shrink polymer material to release an inflatable support tube. Removal of the mandrel element may be facilitated by straightening the helical inflatable support tube and stretching the mandrel to reduce its diameter.

In the instance that the mandrel element is a tube, the diameter of the silicone mandrel may be reduced in consequence of it having been pre- inflated in which instance it is deflated, or by applying a negative pressure to the inside of the mandrel tube to cause it to contract radially.

Alternatively, and with reference to Figure 23 of the drawings, the support medium may be a mass of loose elements or beads (1 7) in which instance the heat shrink polymer tube (1 8) itself, with the beads in it, can be wound around a forming tool to the required helical configuration. The assembly is then heated and the heat shrink polymer tube material can shrink or even stretch as may be necessary so that the tube adopts the helical configuration. Once the formed heat shrink polymer material has cooled and set in its final helical condition, the loose elements or beads can be removed from the tube.

An exactly analogous procedure can be used to implement the third variation of the method according to the invention in which the support medium is a suitable fluid that could be either gaseous or liquid. It will be understood that the construction of the inflatable distender described above may be of any suitable materials that are proven to be appropriate for the purpose and it is envisaged that plastic materials such as polyethylene terephthalate (PET) should be particularly suitable. Many variations are possible which fall within the scope of this invention, some of which are illustrated in Figures 15 to 21 of the accompanying drawings.

As shown in Figure 15, the inflatable support tube assembly may be constructed using two or more layers (21 , 22) of inflatable support tubes for which the helix axes are coincident. Each layer may have a fine pitch or a course pitch. The inflatable tubes in each layer may be of the same or different diameters. They may have the same or different pitches. Such a compound inflatable support tube assembly device may be used to perform staged inflations of the natural body lumen, such as by first inflating the inner inflatable tube, and then an outer inflatable tube. A clinician is therefore able to inflate body vessels or valves in a gradual and progressive manner. Inflating such a support tube assembly allows the inner support tube to inflate and unfold to its helical shape and provide support for the outer inflatable support tube. The concept may similarly be used to deflate in stages. In yet another variation of an inflatable distender an inflatable tube wound spirally (in one or more layers) to form a cylindrical structure when inflated may be attached in relevant zones thereof either to itself or to a support sleeve such as that indicated by numeral (23) in Figure 1 5 so as to prevent the spirally wound tube from elongating or otherwise unravelling when inflated.

The support tubes may further be assembled in such a way that each alternate layer of inflatable support tube spirals in opposite directions, where the inner support tube is constructed as a right-hand helix, while the outer support tube is constructed as a left-hand helix. The device may be further altered such that the pitches of each helix layer are the same, or in multiples of the pitch, such that the support tubes may be bonded together at points at which the helices touch. This allows for a strong support structure once inflated, with very few bonding sites. Inflatable support tubes may be bonded together using thermal or adhesive bonding. Designs that reduce the amount of bonding sites may reduce stiffness and may reduce the outer diameter of the device when in its folded condition. It should be noted that such an inflatable support tube arrangement may offer an additional helix-shaped flow lumen around the outside of the support tubes for additional perfusion. In one variation an elongated inner tube is wound in more than one overlapping layer from the proximal end to the distal end and back, with the helical pitch of overlapping layers being either the same, in which case convolutions of various layers are parallel, or with the helical pitch of overlapping layers being different so that the convolutions of different layers cross each other at different positions.

An inflatable distender according to the invention could be used for specific applications such as opening obstructions in blood vessels or blood valves or in deploying transcatheter-type valves. Figure 16 illustrates an inflatable support tube arrangement in which three tubes are wound in a helix with two (31 ) being located in an outer layer and one (32) being led in an inner layer so that the three tubes are located at the apexes of an equilateral triangle that points inwards towards the axis (33) of the distender.

Figure 17 illustrates an inflatable support tube arrangement in which three tubes are arranged similarly to that shown in Figure 16 but with one tube (34) on the outside of the other two tubes (35).

Figure 18 illustrates an inflatable support tube arrangement in which there is an inner layer having two starts (36) and an outer layer having two starts (37). The general helical shape may thus be constructed as clusters of smaller diameter support tubes, such as in the multiple inflatable support tube arrangement concepts described above. In this manner, three or four support tubes may have smaller diameters than the single large diameter inflatable support tube that they replace. This means that they can carry increased pressure (in inverse proportion to the diameter reduced through Laplace's Law), or the wall thickness of the smaller support tubes may be reduced while carrying the same pressure as a larger support tube, or a combination of these two benefits may be used. Thinner support tubes may allow improved reduction of device diameter in the folded condition. The clustered support tube concept also has the advantage that support tubes may be inflated separately if desired, to facilitate more rapid inflation and deflation.

Figure 19 illustrates a single inflatable support tube (38) that tapers along its length to form of an elongate truncated conical shape. Figure 20 illustrates a single inflatable support tube (39) that tapers from the proximal and distal ends (41 , 42) to a central region (43) of smaller diameter. In this instance the inflatable support tube also decreases in its own diameter from the two ends towards the central region.

Figure 21 illustrates a single rather short truncated conical shape of inflatable tube (44).

The latter structures may be beneficial if the inflatable support tube is to be used to inflate a conduit or lumen that is approximately cone shaped or hourglass-shaped, or where cone-shaped or hour-glass-shaped inflation may be beneficial. The inflatable support tube may of course be constructed from an inflatable support tube with a fine pitch or with a course pitch. Figure 21 shows a spiral helical balloon with a pitch smaller than the diameter of the balloon. Such a structure is radially strong, and may be beneficial where support is more important than the flow lumen diameter.

As regards incorporating an inflatable support tube as described above into a delivery catheter to facilitate transcatheter valvuloplasty or replacement valve deployment, those skilled in the art will recognise that this may be done in many different ways. Multiple lumens that may, but need not, be coaxial, may be constructed according to designs that are commonly known as over- the-wire or rapid-exchange designs. Figures 1 and 2 show one such embodiment.

The catheter incorporates at one end a fitting (51 ) containing at least two luer port fittings (52). One of the ports contains a lumen for travelling over a guidewire, with the lumen passing from the luer port through to the other end of the catheter. The other luer port or ports, to which inflation devices or syringes may be attached, allow inflation of the inflatable support tube or tubes that make up the device of the invention. In the illustrated embodiment, the inflation port, enters the side of a manifold and allows a three-start inflatable support tube to be inflated from one inflation luer. This could also be achieved by providing separate inflation tubes, one for each start of the multi-start inflatable support tube. The luer connector may be attached to a multi-lumen tube, which may most easily be extruded tubing of an appropriate medical grade polymer that is able to bend and flex for delivery through the vessels of the body.

The tube may have four circular lumens, one for the guidewire, as described, and one for each of three starts of the helical inflatable support tube. Although the lumen for the guidewire is most suitably circular, the other three lumens may be formed from many different shapes, including a crescent shape, which is an efficient means of optimising lumen area while reducing total cross-sectional area of the flexible multi-lumen tube. The inflation lumens are continuous with the tubes that inflate the inflatable support tube, and have a diameter that is smaller than the diameter of the helical inflatable support tube itself.

The ends of the inflatable support tube furthest from the luer ports must be sealed such that an inflation medium does not exit the catheter and inflatable support tube. This end of the inflatable support tube may be constructed by extending the inflatable support tube to reach the central guidewire tube, or these tubes may be absent. The illustrated embodiment shows a version that incorporates these inflatable support tube extensions, as it may aid in maintaining the position of the inflatable support tube on the catheter during delivery and deployment. The furthest end of the catheter incorporates a tip (54) to allow smooth delivery over a diseased valve to be treated.

Numerous variations may be made to be embodiments of the invention described above without departing from the scope hereof.