GB2370779A

GB2370779A - Endoluminal centring catheter

Info

Publication number: GB2370779A
Application number: GB0123393A
Authority: GB
Inventors: Jocelyn Asher Simon Brookes
Original assignee: Branch Metro Ltd
Current assignee: Branch Metro Ltd
Priority date: 2000-09-28
Filing date: 2001-09-28
Publication date: 2002-07-10
Also published as: AU2001290138A1; WO2002026323A1; GB0023814D0; GB0123393D0

Abstract

An endoluminal centring catheter 1 comprises an outer layer of silicone 2 covering a core 3 which has spaced perforations 5 each of which connects with a longitudinal duct through which a pressurised fluid may be introduced. The outer layer 2 is bonded to the core 3 except at the areas around the perforations 5. In these areas a thin layer of easily releasable material is interposed which prevents the layer 2 from bonding to the core 3. When a pressurised fluid is introduced into the ducts there is a localised blister-like distension of the outer layer 2 in the zone around the aperture 5.

Description

-- 2370779

TITLE Endoluminal Centring Catheter 5 This invention relates to an endoluminal centring catheter.

Atherosclerotic cardiovascular disease causes the majority of deaths in North America and Europe, through heart attacks (Ml - myocardial infarction) and strokes (CVA - cerebro-vascular accidents). Furthermore, it causes a very significant morbidity within these populations through angina, non-fatal strokes 10 and peripheral vascular disease, including renal hypertension and renal failure and peripheral vascular disease which includes also intermittent claudication, rest pain, ulceration and gangrene.

Atherosclerotic plaques cause stenosis(es) of the arterial lumen, proceeding towards complete vessel obstruction, often hastened by formation 15 of an occlusive thrombosis. What prompts atherogenesis remains uncertain, although accelerative risk factors include cigarette smoking, diabetes, hypertension, hypercholesterolaemia and a positive family history of the disease. Therapeutic options for presenting patients include conservative so treatments which include increasing exercise and limitation of risk factors, and interventional procedures ranging from balloon dilation (angioplasty) to arterial bypass graft surgery, albeit in the coronary or peripheral circulation.

Interventional treatments however, are not without complications which may be of a biological and/or iatrogenic nature. In particular, with both angioplasty and 25 bypass graft surgery, secondary smooth muscle cell neointimal hyperplasia

(SMC-NIH) may prompt a re-stenosis of those very vessels recently treated. In many cases, this phenomenon can cause a progressive therapeutic failure such that for example, at two years out from initial femoro- popliteal arterial bypass grafting, greater than 35% of grafts placed have themselves occluded. Earlier, 5 although ongoing, attempts to salvage such situations centred upon re-

angioplasty or insertion of metallic stents (uncovered or covered) to mechanically hold open re-stenosing vessels. More recently however, attention has been more focused upon direct prevention of SMC-NIH utilising various approaches, often undertaken as a simultaneous adjunct to the primary o interventional procedure being either angioplasty or surgery. Examples include the use of gene therapeutics such as vascular endothelial growth factor -

VEGF, direct cell toxins such as Taxol(D, or photo-dynamic therapy (PDT using laser light to activate locally, circulating cell toxins. An alternative approach to the direct prevention of SMC-NIH is local radiotherapy- brachytherapy.

15 With brachytherapy, endoluminal irradiation to the inner surface of the recently treated vessel wall, from a gamma or beta source, often from an iridium wire for example, is given immediately following angioplasty to prevent subsequent smooth muscle cell growth. Theoretical and observed complications include in particular, eccentric radiation dosing to the vessel wall 20 causing local, trans-mural cell death, with a potential for arterial wall rupture, later aneurysm formation, or stenosis due to fibrosis. In an attempt to prevent this and to better standardise the exposure of the vessel wall to the irradiation, means to keep the radioactive wire source centred within the vessel lumen, over the entire length of vessel to be treated, have been proposed. Such a 25 measure becomes even more relevant as the diameter of the vessel lumen

decreases, for example in the coronary circulation. Development of these centring catheters is new and of importance also, is the attention that must be paid to the actual means of construction of such a device, so as to minimise potential complications deriving from the use of the device itself, such as further 5 extensive trauma to the intima of the artery that has just been angioplastied, with for example, deflation and withdrawal of the balloon system itself. The following is a brief description of how such a centring catheter would be used.

In general, an endoluminal vascular catheter is a flexible tube, of varying diameter and/or length, which can be placed into blood vessels to serve as a 10 conduit for the introduction of extraction of fluids, substances or devices being

commonly wires. With and/or without externally attached parts or devices, the catheter allows manipulation of internal parts of the body, without direct surgical exposure. A balloon catheter is a catheter with a circumferential, inflatable balloon 15 cuff or cuffs attached, which can be expanded forcibly in an area of a blood vessel narrowing, so as to increase the luminal diameter resulting in for instance, an increased blood flow within the vessel. Inflation of the balloon cuff results in the suspension of the internal catheter shaft towards the mid-line of the vessel lumen overall, assuming a symmetrical inflation of the balloon. This to effect becomes the primary objective in the production of a centring catheter, whose use would be in delivering local radiotherapy (brachytherapy) to the vessel wall lining in particular, following recent, conventional angioplasty. With brachytherapy, beta or gamma irradiation as example is emitted from a radioactive wire located within the catheter shaft, circumferentially delivering an 25 equal dose to all parts around the circumference of the inner vessel wall. Such

an even dosing can only be achieved if the catheter shaft containing the radiation source is itself positioned centrally within the vessel lumen and over the full length of the vessel to receive treatment. Contact with the vessel wall lining from the irradiation source is potentially very damaging and ideally, 5 should be kept to an absolute minimum.

With known balloon cuffs, which are inflated over a significant length in order to centre the catheter, damage can be caused to the intima of the vessel over a considerable length. In addition these known devices may not retract fully after use and thus leave a shouldered surface and thereby increase contact with and hence, potential damage to the vessel lining on insertion and removal of the whole centring catheter device.

One of the objects of this invention is to reduce the area of contact between the vessel wall and the known inflatable cuff centring means whilst still providing adequate centring. Another object is to achieve an improved degree 15 of by-pass fluid flow, for example blood flow. Yet a further object is to provide for rapid inflation and deflation of the centring means. Yet a further object is to avoid shouldering when the centring means is deflated.

According to this invention there is provided an endoluminal centring catheter consisting of a layer or layers of a bonded elastic silicone having so interconnected, unbended areas, which form extensible protuberances when a pressurised fluid medium is introduced beneath the said bonded silicone layer or layers.

According to this invention there is also provided an endoluminal centring catheter consisting of a layer or layers of a bonded elastic silicone having sub 25 surface interconnected, unhanded areas between at least two said layers which

form extensible protuberances when a pressurized fluid medium is introduced between the silicone layer or layers in the zone of the unbended areas.

An endoluminal centring catheter is also provided, according to this invention, wherein the catheter has a core with a central passageway, the wall 5 of the core defining said passageway including a plurality of longitudinally extending ducts, the outer surface of the core being overlaid with an extensible layer bonded thereto, discrete areas each including a bond inhibiting layer located around an aperture in the core wall communication with a duct, the application of pressure fluid to a duct causing distension of the extensible layer 10 where not bonded to the core by means of fluid passing through said aperture thereby producing blistering of the outer layer.

In particular, and according to one preferred form of the present invention, multiple, balloon-like protuberances, preferably part spherical, replace the annular cuffs of the prior art and are formed at zones along a

15 selected length of catheter shaft, by application of a layer or layers of elastic silicone, which is especially hydrophobic and hence particularly slippery and atraumatic within the vessel. This layer is applied to substantially the whole surface of the underlying catheter shaft, leaving a plurality of circumferential areas more particularly discrete zones or areas unbended. When pressurized go gas or fluid is introduced beneath this silicone layer, the silicone blisters-up into a balloon whose size relates to the unhanded area. Several such unhanded areas are connected by a separate channel which runs the length of the catheter shaft, leading ultimately, to a connector near the catheter hub. The catheter shaft itself may or may not have a further entirely separate channel 25 through which a wire may be passed or fluids, introduced or extracted.

Introducing pressurised gas or liquid into this aforementioned channel, results in the simultaneous expansion of the string of blistering balloons distally along the catheter shaft. This is undertaken at the lowest pressure sufficient to prompt centring of the catheter shaft and hence, to minimise the damage to the 5 intima of the vessel. Withdrawal of the pressurised gas or liquid allows the complete elastic retraction of the silicone balloons, which resume their pre-

expanded, fiat form as part of the silicone layer, leaving no residual material proud of the whole of the smooth outer surface of the centring catheter device.

Removal of the catheter will now be as atraumatic as is possible with no 10 shouldering at the interface between the retracted balloon and the catheter shaft, as would be seen with a conventional balloon catheter system. The concept of a long string of blistering silicone balloons allows for more accurate centring of the catheter shaft along the whole length of inner vessel lumen to be treated, with each small, spherical balloon creating less localised inner vessel 15 wall trauma than a single, large balloon.

In another preferred embodiment of the catheter, especially for use in small diameter vessels as for example, in the coronary circulation, there is a desire to preserve blood flow to continue to the end organ whilst the device to centre the brachytherapy-giving catheter is functional. In this case, and so according to a preferred embodiment the catheter is designed to allow blood to flow around the outside of the device. Here, the blisters of silicone described previously, would not take on an annular or spherical form but rather, a hemispherical form, placed intermittently at 90 degrees from the previous hemisphere, around the circumference of the catheter shaft. Alternatively, the 25 blisters could take on an elongate fin type appearance or be formed as a

continuous spiral, again placed at intervals around the circumference of the catheter shaft. In each case, the pattern of hemispherical or finlike blisters would be such that, whilst the shaft of the catheter would still be centred within the lumen of the vessel, blood would remain able to flow around the outside of 5 the catheter in between said blisters and hence, supply the end organ continually. Other patterns of blisters may be possible.

This invention is now further described and illustrated with reference to the drawings showing embodiments by way of examples. In the drawings, which are to be taken in conjunction with the foregoing description:

Fig. 1 shows the distal end of a catheter diagrammatically with discrete zones forming extensible protuberances and in a distended condition; Fig. 2 shows the catheter of Fig. 1 in transverse cross-section, on line X-X, with the zones and protuberances in an non 15 extended condition; Fig. 3 shows the catheter of Fig. 1 in transverse cross-section, again on line XX, with the zones in an extended condition forming the protuberances; Fig. 4 shows the catheter of Fig. 2 in longitudinal cross-section SO on the line Y-Y with the zones and protuberances in an non-extended condition; Figs. 5 and 6 show a further embodiment, Fig. 6 being an end view looking in the direction A, with a different configuration of protuberances; and 25 Figs. 7 and 8 show a further embodiment, Fig. 8 being an end view

looking in the direction B. with a different configuration of protuberances. In the drawings and with reference to Figs. 1 to 4, only the end of the 5 catheter as shown and is referenced generally as 1. This comprises a semi rigid assembly formed from a plurality of layers of a silicone material. The outer layer of material 2 is continuous but beneath this layer the material forming the core of the catheter 3, which may comprises one or more individual inner layers, includes spaced perforations 5 each of which connects with a duct 6 o through which a pressurised fluid may be introduced. The construction shown here has three ducts 6 and each duct has respective apertures 5 spaced out along the length.

It will be seen that there are three longitudinally extending lines of perforations radially spaced at 120 degrees with the perforations 5 of each line 15 being longitudinally offset. This is seen more clearly in Fig. 1.

The outer layer 2 is bonded to the core 3 at the peripheral interface 4 except at the area around the perforations 5. At this area a thin layer or strip of easily releasable material 7 is interposed. This layer 7 prevents the layer 2 from bonding to the core 3.

so With this arrangement when a pressurised fluid, gas or liquid, is introduced into ducts 6 there is a localised distension of the outer layer 2 in the zone around the aperture 5 which causes the outer layer to expand in the manner of a blister to take the form as shown by 8. It will be understood that the outer layer is bonded to the immediate lower layer except in the discrete 25 zones immediately surrounding the apertures and as defined by the areas 7.

Fig. 1 shows the three lines of blisters 8 each associated with a duct 3.

In the further Figs. 5 and 6 and Figs. 7 and 8, the general arrangement is the same but the configuration of the unbended areas of the outer layer 2, where not bonded to the next inner layer core 3, is different. In the further 5 Figures like references identify like parts.

Fig. 1 shows an arrangement of small, near spherical blisters 8. Fig. 5 and Fig. 6 show an arrangement with three or four parallel linear lines of spikes or spines 8a and Fig. 7 and Fig. 8 show a further arrangement with linearly aligned spaced fins 8b. It will be clear that the number of lines of protuberances may to be easily varied, three being preferred to achieve centring with greater blood flow area available but four being equally advantages and as shown in the drawings. This invention is not limited to the number or the configuration of the protuberances produced.

A method of producing the discrete zones 7 having the inflatable blisters 8 15 iS disclosed in outline in US 5762 996A and US 5795332A. In these publications inflatable annular cuffs are formed whereas in the method proposed to form a catheter of the present invention silicone material is applied or deposited in the discrete areas of the blisters and which material is unbended in these areas only.

to (Reference: "Catheter-based Radiotherapy for Peripheral Vascular Restenosis" Prabhakar Tripuraneni, Vascular Radiotherapy Monitor, Vol. 1, No 3 1999)

Claims

1. An endoluminal centring catheter consisting of a layer or layers of a bonded elastic silicone having interconnected, unbonded areas, which 5 form extensible protuberances when a pressurised fluid medium is introduced beneath the said bonded silicone layer or layers.

2. An endoluminal centring catheter consisting of a layer or layers of a bonded elastic silicone having sub-surface interconnected, unbonded 10 areas between at least two said layers which form extensible protuberances when a pressurised fluid medium is introduced between the silicone layer or layers in the zone of the unbonded areas.

3. An endoluminal centring catheter consisting of a layer or layers of a 15 bonded elastic silicone having sub-surface interconnected, unbonded areas between at least two said layers which form extensible protuberances when a pressurized fluid medium is introduced between the silicone layer or layers in the zone of the unbonded areas, said unbonded areas forming discrete localised zones in spaced relationship around and 20 along the periphery of the catheter surface.

4. An endoluminai centring catheter consisting of a layer or layers of a bonded elastic silicone having sub-surface interconnected, unbonded areas between at least two said layers which form extensible 25 protuberances when a pressurized fluid medium is introduced between the

silicone layer or layers in the zone of the unhanded areas, said unbended areas forming discrete localised zones around the periphery of the catheter surface, said zones forming an annular protuberance having a circumferentially varying radius.

5. An endoluminal centring catheter as claimed in Claim 1, wherein the

protuberances or blisters may be near spherical in form when inflated or may be hemispherical or part spherical or fin-like or of a spiral configuration.

6. An endoluminal centring catheter as claimed in Claim 1 or 2, wherein the protuberances may be adjacent or spaced or variably spaced along a length of a catheter shaft.

15

7. An endoluminai centring catheter as claimed in any preceding Claim, wherein the catheter has a core with a central passageway, the wall of the core defining said passageway including a plurality of longitudinally extending ducts, the outer surface of the core being overlaid with an extensible layer bonded thereto, discrete areas each including a bond so inhibiting layer located around an aperture in the core wall communication with a duct, the application of pressure fluid to a duct causing distension of the extensible layer where not bonded to the core by means of fluid passing through said aperture thereby producing blistering of the outer layer. 25

8. An endoluminal centring catheter as claimed in any preceding claim,

wherein a plurality of protuberances are provided, for example between one and one hundred, the protuberances preferably being the same or of differing or of variable diameter.

s

9. An endoluminal centring catheter as claimed in any preceding claim, wherein the protuberances retract to an initial state forming a smooth non shouldered catheter surface after removal of the pressurised fluid medium.

10. An endoluminal centring catheter as claimed in any preceding claim, 10 wherein the protuberances each have an annular configuration around the periphery of the catheter the protuberances being spaced apart along the length of the catheter.

11. An endoluminal centring catheter as claimed in any preceding claim, 15 wherein the protuberances comprise elongate ribs when extended, a plurality of such ribs being provided extending longitudinally along the catheter.

12. An endoluminal centring catheter as claimed in claim 8, wherein the ribs so extend in parallel alignment or extend with spiral progression and have equal spacing.

13. An endoluminal centring catheter as claimed in any preceding claim, wherein each protuberance is of blister form occupying a discrete area of us the catheter surface, a plurality of such blisters being located as a regular

spaced matrix on the catheter surface.

14. An endoluminal centring catheter as claimed in claim 10, wherein each blister is in the form of a discrete spine extending longitudinally with the s length thereof greater than the width.

15. An endoluminal centring catheter as claimed in any preceding claim, wherein the protuberances, when extended, allow the continued flow of fluid, for example blood, over the outside of the catheter.

16. An endoluminal centring catheter as claimed in any preceding claim, wherein the materials used may be coloured, opaque or transparent.

17. An endoluminal catheter as disclosed herein and used within another IS tubular structure such as the gut, biliary tree or ureter.

18. An endoluminal centring catheter substantially as described herein and exemplified with reference to the drawings.