FIELD OF THE INVENTION

This invention relates to medical balloon for high pressure angioplasty.

BACKGROUND OF THE INVENTION

High pressure balloon catheters are used in vascular angioplasty to break open heavily calcified or highly stenotic lesions, including coronary, peripheral, neurovascular and structural heart applications. One example is the use of high pressure balloons for vascular access to arteriovenous shunts used in kidney dialysis, where patients will need repeated access to the shunts. These shunts become highly stenotic over time and require high pressure balloons to open. Other applications include peripheral angioplasty balloons to break open highly calcified vascular lesions, valvuloplasty to break open calcified heart valves in preparation for valve repair/replacement, and high pressure non-compliant balloons used in coronary angioplasty and for coronary stent placement.

A known medical balloon forming process involves blowing a thin film of polymer material (or multiple layers of different polymers) into the shape of a balloon in a thermal forming process. This process has reached the limit because of the design trade-off between low profile and high strength. The state of the art for high pressure balloons involves braiding a textile material over a film blown balloon. However, the balloons are still prone to bursting at high pressure, potentially resulting in the loss of balloon material within the venous system of the patient.

SUMMARY OF THE INVENTION

In accordance with a first embodiment of the present invention there is provided a medical balloon comprising a woven textile tube coated on at least its outer surface with a polymer material to seal the tube and thereby define an inflatable balloon. The textile tube may be coated with said polymer material on both its inner and outer surfaces.

In a preferred embodiment the textile tube has a longitudinal axis and comprises a plurality of yarn filaments aligned with said longitudinal axis and a plurality of yarn filaments arranged circumferentially around the tube perpendicular to said longitudinal axis.

The textile tube may be formed from multi-filament yarns, mono-filament yarns or a mixture of multi-filament and mono-filament yarns.

The yarns forming the textile tube may range from 5 to 500 denier.

The yarns forming said textile tube may comprise one or more of regenerated silk viscose, nylon, PET, UHMWPE, LCP (liquid crystal polymer), polyurethane, polypropylene, HDPE, pebax, polyester, Rayon, polytetrafluoroethylene (PTFE), polyamide, carbon, glass fibre, cotton, collagen, calcium alginate, bio-absorbable (e.g. Polyglycolic acid (PGA), 100% PGA, Polyglycolic acid-co-poly-L-lactic acid (PGA/PLLA), Poly-L-lactic acid (PLLA), 100% PLLA.

The yarns forming the textile tube range from 0.025mm to 3.0mm in diameter.

At least some of the yarns forming the textile tube are ring spun.

At least some of the yarns forming the textile tube are twisted.

The yarns may comprise a mixture of two or more different materials.

The polymer material coating the textile tube may comprise polyurethane.

According to a further aspect of the present invention there is provided a method of making a medical balloon comprising forming a woven textile tube and coating at least the outer surface of the textile tube with a polymer material to seal the tube and thereby define an inflatable balloon. The method may comprise coating both the inner and outer surfaces of the textile tube with said polymer material.

In a preferred embodiment the method comprises the steps of coating an outer surface of the textile tube with a polymer material, everting the tube and coating the inner surface (now the outer surface) with a polymer material.

In one embodiment the inner and outer surfaces of the textile tube may be coated with said polymer material by a dispersion process.

In an alternative embodiment at least the outer surface of the textile tube is coated with said polymer material by dipping the textile tube in said polymer material in liquid form.

The method may comprise the step of heating the textile tube in order to effect reflow of at least some yarns forming the textile tube.

The textile tube may be located on a mandrel during coating with said polymer material.

The method may comprise the step of heating the mandrel in order to effect reflow of at least some yarns forming the textile tube.

BRIEF DESCRIPTION OF THE DRAWINGS

A medical balloon and its method of manufacture in accordance with embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which :-

Figure 1 illustrates a textile tube forming part of a medical balloon in accordance with an embodiment of the present invention; Figure 2 illustrates the textile tube from Figure 1 being spray coated with a polymer layer using a dispersion coating machine to seal the outer surface of the textile tube;

Figure 3 illustrates the textile tube of Figure 1 whose outer surface has been completely coated in polymer material;

Figure 4 illustrates the action of completely everting the coated textile balloon in order to expose the uncoated inner surface to the outside. The inner surface, now facing outwards would again be coated as per Figure 2; and

Fig 5 illustrates an alternative method of application of a polymer material to seal the outer surface of the textile tube.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention takes an entirely new approach by weaving a seamless textile tube in the shape of a balloon using high strength polymer yarns in a low profile configuration. The textile is subsequently sealed by applying a polymer material using a solution dispersion or dip coating method.

According to an embodiment of the present invention a medical balloon for high pressure vascular angioplasty comprises a seamless textile fabric tube that has been knitted or woven into the shape of a three dimensional cylindrical balloon. The tube may have fibres/yarns running both axially around the circumference and longitudinally along the length thereof.

The outer and inner surfaces of the textile tube are coated with a polymer material to seal the tube, thus defining an inflatable balloon and allowing the resulting balloon to be inflated.

The resulting medical balloon offers resilient mechanical structure with excellent compliance when inflated to high pressures (i.e. 30 - 50 ATM). Coating/sealing the textile tube with a polymer material allows the balloon to be inflated as a monolithic structure. By comparison, prior art medical balloons incorporate an already formed / blown balloon where a yarn or textile is then placed over the balloon as a secondary process of offer structure / compliance when inflated.

The textile tube may comprise monofilament yarns, multifilament yarns (which may be heatset in a twisted condition or not) or a combination of both. The textile tube may be formed from ring spun yarns of regenerated silk, nylon/high tension nylon, PET/high tension PET, UHMWPE, LCP (liquid crystal polymer), polyurethane, polypropylene, HDPE, pebax, polyester, Rayon, polytetrafluoroethylene (PTFE), polyamide, carbon, glass fibre, cotton, collagen, calcium alginate, bio-absorbable (e.g. Polyglycolic acid (PGA), 100% PGA, Polyglycolic acid-co-poly-L-lactic acid (PGA/PLLA), Poly-L-lactic acid (PLLA), 100% PLLA.. Yarns can be a mixture of high tension and low melt temperature with the addition of weldable yarns to aid construction. The yarn forming the textile tube may range from 5 to 500 denier. The textile tube may also be formed from a combination of yarns of different materials and/or each yarn may be a combination of fibres of different materials. For example mixing PET with nylon fibres would enable bonding the balloon to other components, as nylon has a relatively low melt temperature compared with PET, which would provide additional strength.

The woven textile can include yarns of Nylon material, such as PA6 or PA12 yarns, to make the balloon compatible with downstream heat bonding processes during catheter assembly to facilitate bonding of the balloon to a catheter shaft.

As illustrated in Figures 1 to 4, in a first embodiment the medical balloon in accordance with the present invention may be made by firstly creating the woven textile tube 2 by a suitable weaving process. As shown in Figure 1 , the textile tube 2 comprises a longitudinal tubular body having narrowed end regions 4,6 adapted to fit over a catheter shaft and a reinforced central region 8 having a selected diameter to suit the application for which the balloon is intended to be used. In the embodiment illustrated in Figure 2, the outer surface of the textile tube is coated with a suitable polymer material 10, such as polyurethane, by a dispersion process such as spraying, to seal the tube 2. The tube may be placed over a mandrel during such process. Once the polymer material has dried/cured, the textile tube may be everted (turned inside out), as shown in Figure 4, and the inner surface 12 of the tube, now facing outwards, may be coated with the polymer material by repeating the dispersion process. Once the second coating layer has dried/cured, the resulting balloon may be everted once again to form the finished product.

In an alternative embodiment shown in Figure 5 a medical balloon in accordance with the present invention may be made by dip coating the woven textile tube 2 with a polymer material 10. The textile tube 2 may be mounted onto a shaped mandrel and gripped at one end before being dipped into and then withdrawn from a vessel 14 containing the polymer material 10. The textile tube 2 may then be everted as per Figure 4 to dip coat the inner surface of the tube in a further step.

The textile tube 2 may be subjected to a heating step in order to effect reflow of some or all of the yarns forming the textile tube 2, whereby the heat softens the yarns and causes adjacent and/or overlapping yarns to partially melt together in order to increase the integrity and strength of the textile tube 2 and thus ultimately the medical balloon. The heating step may for example be undertaken by heating the mandrel on which the textile tube 2 is mounted for coating with the polymer material 10. Depending on the material and characteristics of the various yarns forming the textile tube 2, the application of heat may result in some of the yarns partially melting and reflowing around other un-melted yarns.

The invention is not limited to the embodiment(s) described herein but can be amended or modified without departing from the scope of the present invention.