This application claims priority from United States application number 61/216,505, the whole contents of which are hereby incorporated by reference.

The present invention relates to a catheter for the opening of obstructions in bodily vessels. The invention has particular, although not exclusive relevance to the in-vivo opening of total occlusions in the coronary vasculature.

Blood vessels, and in particular arteries, are susceptible to occlusion by sclerotic plaques, emboli, and foreign bodies. Once a blood vessel is partially occluded, laminar blood flow is disrupted and lipid deposition and total occlusion can ensue. Over time, a tough fibrous cap may form over the lipids of a total occlusion to form a Chronic Total Occlusion (CTO).

CTOs in the coronary arteries prevent the direct supply of oxygenated blood to downstream myocardium thereby reducing cardiac function. In the absence of a sufficient supply of oxygenated blood, cardiomyocites may become necrotic or go into a hibernating state in which they remain alive by drawing a reduced blood supply from collateral vessels, but do not contract normally.

Revascularisation, either by Coronary Artery Bypass Graft (CABG) or by opening up a passage through the CTO, can return hibernating cardiomyocytes to their normal contractile state thereby improving cardiac function.

In order to open the tough fibrous cap of a CTO, a cutting device is typically employed to cut a small passage through the CTO before a series of dilation balloons of increasing diameter are inserted into the passage to progressively widen it. This process is long and labourious as, for each time that a larger balloon is to be employed, the previous balloon must be retracted over a wire guide and the next balloon advanced thereover.

According to one aspect, the present invention provides a catheter for the opening of an obstruction in a body vessel. The catheter's distal portion has a rotatable boring element that is arranged so that, when it is rotated against an obstruction, it draws itself distally into the obstruction. The catheter's distal portion also has an expandable dilation member that is coupled to the boring element so that advancement of the rotatable boring element into the obstruction also draws the expandable dilation member to the obstruction.

Advantageously, by having both a boring element and a dilation member on the same catheter, after an initial passage in an obstruction has been made by the boring element, the passage may be dilated by the dilation member without the need separately to retract the boring element over the wire guide and introduce the dilation member thereover - thereby reducing the time required to open the obstruction.

Furthermore, as the dilation member is coupled to the boring member so as to be drawn into the obstruction, there is no need separately to advance the dilation member into the obstruction; this further simplifies the process of opening an obstruction.

According to one aspect, the present invention provides a method of opening of an obstruction in a body vessel. An obstruction opening catheter is positioned in a vessel adjacent to an obstruction. A rotatable boring element of the catheter is then rotated so as to bore a passage into the obstruction and to draw itself into the passage and to draw a dilation member of the catheter towards or into the passage. The dilation member is then expanded so as to dilate the passage.

In one embodiment, the catheter is positioned in the vessel using a wire guide and, before the rotatable boring element is bored into the obstruction, the wire guide is used to puncture or indent the obstruction thereby providing a pilot hole or indent for the boring element.

These and various other aspects of the invention will become apparent from the following detailed description which is given by way of example only and which is described with reference to the accompanying Figures in which:

Figure 1 shows a perspective view of an occlusion opening catheter arranged in an expanded configuration;

Figure 2 shows the catheter of Figure 1 arranged in an unexpanded configuration; Figure 3 shows a longitudinal cross-section of the catheter of Figure 1 arranged in the unexpanded configuration;

Figure 4 shows a longitudinal cross-section of the catheter of Figure 1 arranged in the unexpanded configuration and positioned in a blood vessel adjacent to a CTO;

Figure 5 shows a transverse cross-section through the blood vessel of Figure 4;

Figure 6 shows a longitudinal cross-section of the catheter of Figure 1 arranged in the unexpanded configuration and positioned in a blood vessel and partially within a CTO;

Figure 7 shows a transverse cross-section through the catheter and blood vessel of Figure 6;

Figure 8 shows a longitudinal cross-section of the catheter of Figure 1 arranged in the unexpanded configuration and positioned in a blood vessel and within a CTO;

Figure 9 shows a transverse cross-section through the catheter and blood vessel of Figure 8;

Figure 10 shows a longitudinal cross-section of the catheter of Figure 1 arranged in the expanded configuration and positioned in a blood vessel and within a CTO;

Figure 11 shows a transverse cross-section through the catheter and blood vessel of Figure 10; and

Figures 12, 13, and 14 show transverse cross-sections through alternative embodiments of the catheter.

Figure 1 shows a perspective view of a flexible catheter 10 having an obstruction opening section 12 and a delivery and removal section 14. The obstruction opening section 12 comprises: an engagement member 16, which is in this case tapered, having a helical thread 18 disposed thereabout so as to form a boring element for - A -

engagement with a CTO; a flexible torque member 20, in this case a tube extending to the proximal end of the catheter, for rotating the engagement member 16 about its longitudinal axis; and a dilation member 22 fixedly coupled to the torque member 20 for dilating a passage in the CTO. In Figure 1 the dilation member 22 is shown in an 5 expanded configuration in which its diameter is greater than that of the torque member 20. The delivery and removal section 14 comprises: a flexible delivery sheath 24 having an internal diameter that is large enough for the obstruction opening section 12 to be introduced and retracted therethrough when the dilation member 22 is in an unexpanded configuration; and a fitting 26 for coupling the 10 catheter 10 to control devices (not shown).

Figure 2 shows a perspective view of the flexible catheter 10 of Figure 1 , this time with the dilation member 22 in the unexpanded configuration. In this case, the dilation member is a winged balloon and its wings 23 are folded about itself so that, in the unexpanded configuration, the diameter of the dilation member 22 is 15 substantially the same as that of the torque member 20.

Figure 3 shows a longitudinal cross-section of the obstruction opening section 12 of the flexible catheter 10 of Figure 1 with the dilation member 22 in the unexpanded configuration. The engagement member 16 tapers in the proximal-distal direction (as indicated by arrow P-D of Figure 3) so as to have a very small cross-sectional area at

20 the distal end of the obstruction opening section 12. Having a small cross-sectional area at its distal end enables the engagement member 16 to concentrate any distal direction pushing force onto a small area of CTO thereby helping the obstruction opening section 12 to tap into CTOs. As can be seen, in this embodiment dilation member 22 is recessed in torque member 20 so that, in the unexpanded

25 configuration, the diameter of the dilation member 22 is substantially the same as that of the torque member 20. Obstruction opening section 12 further comprises a tube 29 located within the torque member 20 so as to define by its exterior surface, along with the interior surface of the torque member 20, an inflation lumen 30 for supplying a fluid to the winged balloon for inflation. The interior surface of the tube

30 29 defines a wire guide lumen 28 for a wire guide. In operation, to access a coronary artery having a CTO to be opened, a percutaneous incision is made in the patient, for example to access the femoral artery. A wire guide is then introduced via the incision into the patient's arterial system and navigated, under the guidance of an imaging system, via the aorta to the relevant coronary ostium and thence to the site of the CTO. Suitable imaging systems include, for example, contrast enhanced X-ray, ultrasound, magnetic resonance imaging or combinations thereof. The flexible catheter 10 with the obstruction opening section 12 retracted within the flexible delivery sheath 24 is then introduced over the wire guide and navigated towards the site of the CTO before the obstruction opening section 12 is advanced so as to project from the flexible delivery sheath 24.

Figure 4 shows a longitudinal cross-section of the obstruction opening section 12 positioned within a coronary artery 32 and adjacent to a CTO 34 with the dilation member 22 in the unexpanded configuration. As can be seen, a wire guide 36 has been navigated to abut the CTO 34 and the obstruction opening section 12 has been advanced along the wire guide 36 to be adjacent to the CTO 34. Figure 5 shows a cross-section along line A-A of Figure 4 in which the CTO 34 totally occludes the coronary artery 32.

Once the obstruction opening section 12 is located as shown in Figure 4, the wire guide 36 is partially withdrawn within the wire guide lumen 28 so that its distal tip is proximally set back from the obstruction opening section's distal end. This ensures that the distal tip of the wire guide 36 does not interfere with the opening of the CTO

34. The torque member 20 is then advanced and rotated so that the helical thread

18 taps into the CTO 34. Figure 6 shows the obstruction opening section 12 partially tapped into the CTO 34 and Figure 7 shows a cross-section along line B-B of Figure

6 in which the CTO 34 has been entered by the engagement member 16.

Further rotation of the torque member 20 then draws the helical thread 18 along with the engagement member 16 and the dilation member 22 into the CTO 34 until the dilation member 22 is adjacent to the CTO 34 - as shown in Figure 8. Figure 9, which is a cross-section along line C-C of Figure 8, shows the dilation member 22 radially surrounded by the CTO 34 and illustrates the winged form of the balloon dilation member 22. As it is easier for an operator to control the amount of torque that they apply than the amount of linear force, the use of the helical thread 18 to convert torque supplied by the operator into linear advancement of the obstruction opening section 12 into the CTO 34 provides the operator with an improved degree of control over the opening of the CTO 34. The use of torque to advance the obstruction opening section 12 into the CTO 34 also reduces the chances of parts of the CTO 34 becoming dislodged during the opening process due to the operator jabbing the catheter into the CTO 34 - thereby reducing the risk of emboli.

Inflation fluid, for example saline solution, is then supplied under pressure via the inflation lumen 30 to the dilation member 22 so as to expand it and enlarge the passageway in the CTO 34 that the dilation member 22 occupies. Figure 10 shows the dilation member 22 in the expanded configuration having dilated the CTO 34 and Figure 11 shows a cross-section along line D-D of Figure 10.

If the length of the CTO 34 is greater than that of the dilation member 22, then the CTO 34 may need to be opened in several stages with the obstruction opening section 12 being successively screwed into the CTO 34 and the dilation member 22 expanded multiple times. Alternatively, the obstruction opening section 12 may be screwed all the way through the CTO 34 before the dilation member 22 is repeatedly expanded and retracted.

Once a passageway has been opened across the CTO 34, the wire guide 36 is advanced through the guide wire lumen 28 until it straddles the CTO 34 and the obstruction opening section 12 is withdrawn from the patient. Subsequently, dilation balloons (not shown) having a larger unexpanded diameter than the dilation member 22 may be introduced over the wire guide 36 to further enlarge the passage in the CTO 34 and/or cutting catheters (not shown) may be introduced over the wire guide 36 to cut away sections of the CTO 34. Alternatively or additionally, a stent (not shown) may be introduced over the wire guide 36 and deployed in the passageway to prevent restenosis.

A person skilled in the art will appreciate that although the above describes the opening of CTOs in the coronary vasculature, the device and methods described herein may instead be employed for opening partial occlusions and/or may be used in other bodily vessels, for example the opening of atheromatous occlusions in the arms or legs of subjects having peripheral artery occlusive disease.

As an alternative to the above description in which the wire guide 36 is partially withdrawn prior to advancing the obstruction opening section 12 into the CTO 34, the step of partially withdrawing the wire guide 36 may be omitted. Advantageously, such an approach reduces the total operation time as the wire guide 36 neither needs to be partially withdrawn prior to opening the CTO 34, nor advanced thereafter. In such cases, if the proximal end of the wire guide 36 is held in place so as to prevent accidental advancement or withdrawal of the wire guide 36 during opening of the CTO 34, then rotation of the torque member 20 may cause the wire guide 36 to twist and this may impede further rotation of the torque member 20. Accordingly, the wire guide lumen 28 may be arranged so as to reduce twisting of any wire guide 36 located therein, for example the wire guide lumen 36 may be arranged so that its long axis is coaxial with the long axis of the flexible catheter 10.

As one possibility, prior to advancing the obstruction opening section 12 into the CTO 34, the wire guide 36 may be completely withdrawn from the patient. If such an approach is employed then the wire guide lumen 28 need not be arranged to prevent twisting of the wire guide 36.

If the wire guide 36 is withdrawn from the patient prior to advancing the obstruction opening section 12 into the CTO 34, then the wire guide lumen 28 may be employed to deliver contrast agent to the site of the CTO 34 to enable an operator to better visualise the opening of the CTO 34 via an imaging system, for example X-ray, ultrasound, or magnetic resonance imaging. This may help the operator to determine whether the CTO 34 has been fully opened or not and may help avoid screwing into a vessel wall. As another possibility, the flexible catheter 10 further comprises a separate contrast agent lumen (not shown) for the delivery of contrast agent to the distal end of the flexible catheter 10.

The wire guide 36 may have a hardened tip, or be made of a hardened material so as to enable an operator to punch an initial pilot hole or indent into the CTO 34 prior to advancing the obstruction opening section 12 into the CTO 34. Preferably, the wire guide 36 is made of NiTi and has a platinum tip.

Although the above describes a dilation member 22 that is a winged balloon set in a recess of the torque member 20, the torque member 20 may have no recess and the dilation member 22 may simply be mounted on an exterior surface of a tube-like torque member 22. Also, the dilation member 22 may be any device that is remotely operable to have its diameter changed, for example a cantilevered or sprung mechanical cage or a thermoelectrically expandable sleeve. Also, although the use of a winged balloon (or other arrangements of balloons formed of non-distensible material) for the dilation member 22 is preferable, other balloons, for example distensible balloons, may be employed. If a winged balloon is employed as the dilation member 22, when in the unexpanded configuration, the wings 23 of the balloon are preferably arranged to wrap about the torque member 20 in a direction so that the screwing action of the helical thread 18 being advanced into a CTO 34 acts to push the wings 23 against the torque member 20. Preferably, when in the unexpanded configuration, the dilation member 20 has a small diameter, for example 1mm; when in the expanded configuration, the dilation member 22 will have a much larger diameter, for example between 1.5 and 50mm.

The torque member 20 is preferably flexible longitudinally but rotationally stiff with a torque ratio between its proximal and distal ends of or close to 1 :1 and may be made, for example, from stainless steel, NiTi or CuZnAI. The helical threads 18 may be made of the same or a similar material and may be affixed to the torque member 20, for example, by laser welding or by gluing. As another possibility, the torque member 20 may be made of polyimide, PEEK or another plastics material; in such cases, the helical threads 18 may be of the same material as the torque member 20 and may be integrally formed with the torque member 20, or may be formed on top of the torque member 20 by insert moulding. To provide the torque member 20 with a high torque ratio but with sufficient longitudinal flexibility in the distal region to provide for good navigability, the torque member may be thicker at its proximal end than at its distal end. The torque member may be provided with a handle or wheel (not shown) at its proximal end to provide an operator with a mechanical advantage when screwing the obstruction opening section 12 into a CTO 34.

As one possibility, instead of the obstruction opening section 12 having an engagement member 16 that is tapered as in the embodiment of Figures 1 to 11 , the distal end of the obstruction opening section 12 may simply be formed from the torque member 20 and may have a tubular form - as shown in Figure 12. Advantageously, such a configuration is easier to fabricate as it requires neither the formation of an engagement member that is tapered nor the fixing of helical threads onto such an engagement member. The embodiment of Figure 12 also differs from that of Figures 1 to 11 in that it has a dividing wall 39 to divide the interior lumen of the torque member 20 into an inflation lumen 38 and a wire guide lumen 40.

As one possibility, instead or as well as having an engagement member 16 that is tapered, the radial height of the helical thread 18 may vary in the proximal-distal direction as illustrated in Figure 13 which shows an obstruction opening section 12 as in Figure 12 but with the height of the helical thread 18 increasing as the helical thread 18 gets further away from the obstruction opening section's distal end. Advantageously, once such a thread has tapped into the CTO 34, continued rotation of the torque member 20 will advance portions of the helical thread 18 having a larger size into the CTO 34 thereby allowing the operator to exert greater force upon the CTO 34.

Although the above has described the helical thread 18 in terms of a single uninterrupted thread, it may comprise a multistart thread and/or may be interrupted along its length. Figure 14 shows an alternative embodiment in which the engagement member 16 is rotatable with respect to the dilation member 22. In this embodiment, dilation member 22 is held in a recess of a support member 42 having an inflation lumen 44, defined by the interior surface of the support member 42 and a dividing wall 41 , for supplying a fluid to the dilation member 22. The support member 42 further has a collar 46 for the retention of the engagement member 16. The engagement member 18 has a neck portion 48 about which the collar 46 of the support member 42 is positioned and a shoulder portion 50 to retain the collar 46 of the support member 42 on the neck portion 48. The engagement member 18 is free to rotate with respect to the support member 42. In this embodiment, instead of having an external torque member, torque is supplied to the engagement member 16 via the surround 52 of the wire guide lumen 28, which is also free to rotate with respect to the support member 42. In operation, when the engagement member 18 is advanced into a CTO 34, the shoulder portion 50 of the engagement member 18 bears onto collar 46 of the support member 42 and draws the support member 42, and thereby the dilation member 22, into the CTO 34. In this embodiment, the dilation member 22 is not subjected to rotational forces when it is advanced into the CTO 34 thereby reducing the stresses experienced by the dilation member 22 and possibly meaning that it may be made of a less rugged construction. The torque required to rotate the engagement member 16 may in certain arrangements be reduced if the dilation member 22 is not also required to rotate.

As one possibility, the obstruction opening section 12 may have no wire guide lumen and be independently navigable to the site of the CTO 34.

To facilitate visualisation of the obstruction opening section 12 during the opening of a CTO 34, one or more radiopaque markers may be provided on the obstruction opening section 12, for example between the dilation member 22 and the distal tip of the engagement member 16. As one possibility, one or more component parts of the obstruction opening section 12 may be fabricated from radiopaque materials, for example a plastics material mixed with a metallic material. In the embodiments shown in the Figures, the dilation member 22 is longitudinally set back from the helical threads 18. As another possibility, the dilation member 22 may abut the proximal end of the helical threads 18. If the dilation member 22 has substantially non-expandable shoulder portions (not shown) for coupling the dilation member 22 to the torque member 20 and these shoulder portions are arranged to lie on the torque member 20 to either side of the expandable portion of the dilation member 22 in the proximal-distal direction, then the dilation member 22 may be recessed in torque member 20 in an undercut recess so that its expandable portion abuts the helical threads 18. As another possibility, the engagement member 16 may initially be separate from the torque member 20 and, when the engagement member 16 is coupled to the torque member 20 during assembly, one or more portions of the dilation member 22, for example a shoulder portion, may be sandwiched between the torque member 20 and the engagement member 16 so that a portion of the dilation member 22 lies within the engagement member 16.

A person skilled in the art will appreciate that any of the above alternatives may be employed either alone or in combination.