The present invention relates to a balloon catheter, and in particular, to a balloon catheter for guiding a piercing tool to a side wall of a vessel in a human or animal subject, and the invention also relates to a 5 method for remotely guiding a piercing tool into engagement with the side wall of a vessel in a human or animal subject.

Unblocking of vessels in a human or animal subject, for example, unblocking an occluded blood vessel in the cardiovascular system, in general, requires guiding a boring tool into engagement with the occlusion in

I o the blood vessel and then urging the boring tool through the occlusion in order to form a channel

therethrough. Once the channel has been formed, the diameter of the channel can be increased by inflating a balloon of a balloon catheter within the channel. In general, occlusions formed in blood vessels of the cardiovascular system are formed by a relatively hard plaque material, which can be relatively difficult to bore through, particularly if the occlusion extends a reasonable distance within the vessel. In

15 such cases, it has been found desirable to open a channel through the subintimal space between an inner layer and an outer layer of the wall of the blood vessel, so that the newly formed channel within the subintimal space in the wall of the blood vessel bypasses the occlusion. However, this procedure requires piercing the inner layer of the wall of the blood vessel in order to gain access to the subintimal space to open the channel in the subintimal space. This procedure is relatively difficult to carry out, since it is 0 difficult, if not impossible, to remotely direct a piercing tool sidewardly into the inner layer of the wall of the blood vessel at a suitable location spaced apart from the occlusion.

There is therefore a need for a balloon catheter for guiding a piercing tool to a side wall of a vessel in a human or animal subject which addresses this problem.

5

The present invention is directed towards providing such a balloon catheter, and the invention also directed towards a method for remotely guiding a piercing tool into engagement with the side wall of a vessel in a human or animal subject. 0 According to the invention there is provided a balloon catheter comprising an elongated catheter

extending between a proximal end and a distal end, a balloon located on the catheter adjacent the distal end thereof with the catheter extending through the balloon, and the balloon defining with the catheter a hollow interior region, the balloon being configured for anchoring the balloon catheter in a vessel, the catheter being branched within the hollow interior region of the balloon at a branching location, and comprising a primary limb extending distally from the catheter adjacent the branching location and terminating in a distal end defining the distal end of the catheter, and a secondary limb extending from the branching location and diverging distally from the primary limb and terminating adjacent a side wall of the balloon and extending therethrough, a first bore extending through the catheter and through the primary limb from the proximal end of the catheter to the distal end of the primary limb for accommodating a guide wire therethrough for guiding the balloon catheter to a site in the vessel, and a second bore extending through the catheter and the secondary limb from the proximal end of the catheter to the distal end of the secondary limb for accommodating a piercing tool therethrough.

In one aspect of the invention the secondary limb approaches the side wall of the balloon with the central axis of the second bore at an angle to the side wall of the balloon in the range of 10° to 90° when the balloon is in inflated.

In another aspect of the invention the secondary limb approaches the side wall of the balloon with the central axis of the second bore at an angle to the side wall of the balloon in the range of 15° to 80° when the balloon is inflated, and preferably at an angle in the range of 20° to 70°, and advantageously, at an angle in the range of 30° to 60°, and ideally, at an angle of approximately 45° when the balloon is inflated.

In one aspect of the invention the second bore is threaded internally with an internal screw thread for engaging an external screw thread on one of a piercing tool and a carrier element carrying the piercing tool for urging the piercing tool through the distal end of the second bore into engagement with the side wall of the vessel by rotating the one of the piercing tool and the carrier element of the piercing tool in the second bore when the balloon is inflated and anchoring the balloon catheter in the vessel.

In one aspect of the invention the internal screw thread in the second bore is located adjacent a portion of the second bore which is adjacent the balloon, and preferably, which is adjacent a proximal end of the balloon.

In another aspect of the invention the secondary limb of the catheter extends through the side wall of the balloon and terminates in the side wall substantially flush with the external surface of the side wall: In another aspect of the invention the hollow interior region defined by the balloon and the catheter comprises an annular hollow interior region.

Preferably, the catheter extends centrally and axially in the balloon. Advantageously, the primary limb of 5 the catheter extends axially to the proximal end of the balloon. Ideally, the primary limb of the catheter extends centrally in the balloon, and preferably, the primary limb of the catheter extends through the distal end of the balloon with the first bore terminating externally of the balloon.

In a further aspect of the invention the balloon catheter comprises a monitoring means for monitoring the l o advance of the piercing tool as the piercing tool is advanced in the second bore. Preferably, the

monitoring means comprises a means for monitoring the distance the carrier element of the piercing tool is urged into the second bore adjacent the proximal end of the catheter. Advantageously, the monitoring means comprises a means for monitoring the angular rotation of the tool carrier.

15 In another aspect of the invention the second bore is configured for guiding a piercing tool into

engagement with an inner layer of a side wall of a blood vessel of a human or animal subject for piercing the inner layer of the side wall to gain access to the subintimal space in the side wall of the blood vessel.

Advantageously, the second bore is configured for guiding a piercing tool into engagement with an inner 20 layer of a side wall of a blood vessel of the cardiovascular system of a human or animal subject for

piercing the inner layer of the side wall to gain access to the subintimal space in the side wall of the blood vessel.

The invention also provides a balloon catheter according to the invention and a piercing tool located in the 5 second bore of the balloon catheter.

Preferably, the piercing tool is secured to a carrier element adjacent a distal end of the carrier element, and advantageously, the carrier element is located in the second bore of the balloon catheter. 0 Additionally, the invention provides a method for remotely guiding a piercing tool into engagement with the side wall of a vessel in a human or animal subject, the method comprising providing a balloon catheter comprising an elongated catheter extending between a proximal end and a distal end, a balloon located on the catheter adjacent the distal end thereof with the catheter extending through the balloon and the balloon defining with the catheter a hollow interior region, the balloon being configured for anchoring the balloon catheter in the vessel, the catheter being branched at a branching location within the hollow interior region of the balloon, and comprising a primary limb extending distally from the catheter adjacent 5 the branching location and terminating in a distal end defining the distal end of the catheter, and a

secondary limb extending from the branching location and diverting distally from the primary, limb and terminating adjacent a side wall of the balloon and extending therethrough, a first bore extending through the catheter and through the primary limb from the proximal end of the catheter to the distal end of the primary limb, and a second bore extending through the catheter and the secondary limb from the proximal l o end of the catheter to the distal end of the secondary limb, urging the balloon catheter to the vessel and locating the balloon in the vessel adjacent a site in which the piercing tool is to be guided to the side wall of the vessel, inflating the balloon in the vessel for anchoring the balloon in the vessel with the distal end of the second bore aligned with the site, urging a piercing tool through the distal end of the second bore into engagement with the side wall of the vessel, and urging the piercing tool to pierce an opening through

15 an inner layer of the side wall of the vessel.

In one aspect of the invention the balloon in the vessel is initially inflated to an extent to permit orienting of the balloon in the vessel, and the balloon is oriented in the vessel until the second bore is located adjacent the site at which the piercing tool is to be guided into the side wall of the vessel prior to further 0 inflating of the balloon for anchoring the balloon in the vessel.

Preferably, the balloon catheter is urged through the vascular system of the human or animal subject to the vessel. 5 Advantageously, the balloon catheter is urged to a vessel in the cardiovascular system of the human or animal subject.

In one aspect of the invention the piercing tool is urged into engagement with the side wall of the vessel through the distal end of the second bore at an angle to the side wall of the vessel in the range of 10° to 0 90° when the balloon is in inflated.

In another aspect of the invention the piercing tool is urged into engagement with the side wall of the vessel through the distal end of the second bore at an angle to the side wall of the vessel in the range of 15° to 80° when the balloon is inflated.

In a further aspect of the invention the piercing tool is urged into engagement with the side wall of the vessel through the distal end of the second bore at an angle to the side wall of the vessel in the range of 20° to 70° when the balloon is inflated.

Preferably, the piercing tool is urged into engagement with the side wall of the vessel through the distal end of the second bore at an angle to the side wall of the vessel in the range of 30° to 60° when the balloon is inflated.

Advantageously, the piercing tool is urged into engagement with the side wall of the vessel through the distal end of the second bore at an angle to the side wall of the vessel of approximately 45° when the balloon is inflated.

In another aspect of the invention the piercing tool is secured to a carrier element adjacent a distal end of the carrier element.

In one aspect of the invention the second bore is threaded internally with an internal screw thread for engaging an external screw thread on one of the piercing tool and the carrier element, and the piercing tool is urged through the distal end of the second bore into engagement with the side wall of the vessel by rotating the one of the piercing tool and the carrier element in the second bore.

Preferably, the internal screw thread in the second bore is located adjacent a portion of the second bore which is adjacent the balloon. Advantageously, the internal screw thread in the second bore is located adjacent a proximal end of the balloon.

Advantageously, the secondary limb of the catheter extends through the side wall of the balloon and terminates in the side wall substantially flush with the external surface of the side wall.

In one aspect of the invention the hollow interior region defined by the balloon and the catheter comprises an annular hollow interior region. Preferably, the catheter extends centrally and axially in the balloon.

Advantageously, the primary limb of the catheter extends axially through the balloon to the proximal end thereof.

Preferably, the primary limb of the catheter extends centrally in the balloon.

Advantageously, the primary limb of the catheter extends through the distal end of the balloon with the first bore terminating externally of the balloon.

In one aspect of the invention the balloon catheter comprises a monitoring means for monitoring the advance of the piercing tool as the piercing tool is advanced in the second bore.

Preferably, the monitoring means comprises a means for monitoring the distance the carrier element of the piercing tool is urged into the second bore adjacent the proximal end of the catheter.

Advantageously, the monitoring means comprises a means for monitoring the angular rotation of the one of the carrier element and the piercing tool. Preferably, the second bore is configured for guiding the piercing tool into engagement with an inner layer of a side wall of a blood vessel of a human or animal subject for piercing the inner layer of the side wall to gain access to the subintimal space in the side wall of the blood vessel.

Advantageously, the second bore is configured for guiding the piercing tool into engagement with an inner layer of a side wall of a blood vessel of the cardiovascular system of a human or animal subject for piercing the inner layer of the side wall to gain access to the subintimal space in the side wall of the blood vessel.

The advantages of the invention are many, a particularly important advantage of the invention is that it permits relatively accurate piercing of the inner layer of the wall of a vessel while at the same time avoiding piercing an outer layer of the side wall of the vessel. This is a particularly important advantage when it is desired to form a channel through the subintimal layer of the side wall of a blood vessel between the inner layer and the outer layer in order to bypass an occlusion in the vessel. A further advantage of the invention is that the piercing tool is directed distally into the inner layer at an angle generally less than 90 ^° to the side wall of the vessel, and by appropriately setting the angle at which the secondary limb distally approaches the side wall of the balloon, the angle at which the boring tool is directed into the inner layer of the side wall of the vessel can be set within the range of 15' to 80 ^° , 20 ^' to 70 ^' , 30 ^° to 60 ^° , and ideally at an angle of 45 ^° to the side wall of the vessel.

By providing internal screw threads in the second bore which are co-operable with corresponding external screw threads on the one of the carrier element and the piercing tool, the distance travelled by the piercing tool from the distal end of the second bore can be accurately determined by monitoring the angular rotation of the carrier element, or alternatively by monitoring the distance the carrier element is urged into the second bore adjacent the proximal end of the catheter.

The invention will be more clearly understood from the following description of a preferred embodiment thereof, which is given by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a cross-sectional side elevational view of a balloon catheter according to the invention,

Fig. 2 is a cross-sectional side elevational view of a portion of the balloon catheter of Fig. 1 in use,

Fig. 3 is a cross-sectional side elevational view of a detail of the balloon catheter of Fig. 1 in use, Fig. 4 is a side elevational view of a portion of the balloon catheter of Fig. 1 , and

Fig. 5 is a front end elevational view of the portion of Fig. 4 of the balloon catheter of Fig. 1.

Referring to the drawings, there is illustrated a balloon catheter according to the invention, indicated generally by the reference numeral 1, for remotely guiding a piercing tool 3 into engagement with a side wall 4 of a vessel in a human or animal subject, in this embodiment of the invention a blood vessel 5, in, for example, an artery of the cardiovascular system. Before describing the balloon catheter 1 , the blood vessel 5 will first be described. In this case the blood vessel 5 is blocked by a total occlusion 6, see Fig. 2, which comprises a relatively hard plaque material. The side wall 4 of the vessel 5 comprises an inner layer 7 and an outer layer 8 with a subintimal space 9 therebetween. In order to allow blood to flow through the vessel 5 from a proximal side 10 of the occlusion 6 to a distal side 11 thereof, it is desired to form a channel 12 extending through the subintimal space 9 of the side wall 4 of the vessel 5 to bypass the occlusion 6. This requires piercing an opening 13 through the inner layer 7 of the side wall 4 into the subintimal space 9 to allow a guide wire or other suitable tool to be urged into and through the subintimal space 9 of the side wall 4 to form the channel 12 through the subintimal space 9 between the inner and outer layers 7 and 8 bypassing the occlusion 6.

Turning now to the balloon catheter 1, the balloon catheter 1 comprises an elongated catheter 14 extending between a proximal end 15 and a distal end 16. A balloon 18, which when inflated is substantially cylindrical, extends between a proximal end 19 and a distal end 20, and is located on the catheter 14 adjacent the distal end 16 thereof with the catheter 14 extending centrally and axially through the balloon 18 and defining with the balloon 18 an annular hollow interior region 22.

The catheter 14 is branched at a branching location 24 within the hollow interior region 22 of the balloon 18 into a primary limb 25 and a secondary limb 26. The primary limb 25 extends centrally and axially distally from the branching location 24 and through the distal end 20 of the balloon 18 and terminates externally of the distal end 20 of the balloon 18 to define the distal end 16 of the catheter 14. The secondary limb 26 extends from the branching location 24 and diverges distally from the primary limb 25, and terminates at a distal end 28 adjacent a side wall 29 of the balloon 18. The distal end 28 of the secondary limb 26 extends through the side wall 29 of the balloon 18, and terminates substantially flush with the outer surface of the side wall 29 of the balloon 18.

A first bore 30 extends through the catheter 14 and the primary limb 25 from the proximal end 15 of the catheter 14 to the distal end 16 of the primary limb 25 for accommodating a guide wire 32 for remotely guiding the balloon catheter 1, and in turn the balloon 18 into the vessel 5. The guiding of a balloon catheter into a vessel over a guide wire will be well known to those skilled in the art.

A second bore 34 extends through the catheter 14 and the secondary limb 26 from the proximal end 15 of the catheter 14 to the distal end 28 of the secondary limb 26 for accommodating the piercing tool 3 therethrough and for directing and guiding the piercing tool 3 to the site at the side wall 4, at which it is desired to urge the piercing tool into and through the inner layer 7 of the side wall 4 of the vessel 5 to form the opening 13 in the inner layer 7. A carrier element 35 for carrying the piercing tool 3 extends between a proximal end 36 and a distal end 37 to which the piercing tool 3 is secured. The carrier element 35 extends through the second bore 34 and exits the second bore 34 adjacent the proximal end 15 of the catheter 14 so that the proximal end 37 of the carrier element may be operated as will be described below for urging the piercing tool 3 through the inner layer 7 of the side wall 4. The piercing tool 3 extends between a proximal end 39 and a distal end 40 which terminates in a piercing point 42 for piercing through the inner layer 7 of the side wall 4 of the vessel 5 in order to form the opening 13 through the inner layer 7 into the subintimal space 9. The proximal end 39 of the piercing tool 3 is secured to the distal end 37 of the carrier element 35.

A portion 43 of the second bore 34 is internally threaded with internal screw threads 44 adjacent the proximal end 19 of the balloon 18. A portion 44 of the carrier element 35 is provided with external screw threads 46 which are co-operable with the internal screw threads 44 in the second bore 34, so that by rotating the carrier element 35 in the second bore 34 in the appropriate direction, the carrier element 35 and in turn the piercing tool 3 is advanced through the distal end 28 of the second bore 34 into engagement with the inner layer 7 of the side wall 4. In this embodiment of the invention the spacing between the internal screw threads 44 and the distal end 28 of the second bore 34, and the spacing between the external screw threads 46 on the carrier element 35 and the piercing point 42 of the piercing tool 3 are set so that when the external screw threads 46 are about to engage the proximal end 48 of the internal screw threads 44, the piercing point 42 of the piercing tool 3 is substantially flush with the distal end 28 of the secondary limb 26. Accordingly, by monitoring the angular rotation through which the carrier element 35 is rotated once engagement commences of the external screw threads 46 with the internal screw threads 44 adjacent the proximal end 48 of the internal screw threads 44, the distance the piercing point 42 of the piercing tool 3 is advanced outwardly through the distal end 28 of the second bore 34 can be readily determined, knowing the pitch of the internal and external screw threads 44 and 46. The positioning of the branching location 24 of the catheter 14 within the balloon 18, and the positioning of the location in the side wall 29 of the balloon 18 through which the secondary limb 26 extends through the side wall 29 are set so that the secondary limb 26 approaches the side wall 29 of the balloon 18 distally at an angle, such that a centre-line 49 of the second bore 34 extends at an angle a to the side wall 29 of the balloon 18, which in this embodiment of the invention is approximately 45 ^° . Thus, when the balloon 18 is inflated and anchored in the vessel 5, the piercing tool 3 is urged into the inner layer 7 of the side wall 4 at a similar angle of approximately 45 ^° . However, it will be readily appreciated that by altering the configuration of the secondary limb 26 within the hollow interior region 22 of the balloon 18, the angle a of the centre-line 49 of the second bore 34 relative to the side wall 29 of the balloon 18 may be varied, and typically, would lie in the range of 30 ^° to 60 ^° , although in some cases, the angle a could be up to 90 ^° .

Referring now to Figs. 4 and 5, a monitoring means for monitoring the advance of the piercing point 42 of the piercing tool 3 outwardly from the distal end 28 of the second bore 34 comprises a monitoring device 50. The monitoring device 50 comprises a housing 51 which is adapted for releasably clamping to the catheter 14 adjacent the proximal end 15 thereof. A pair of concentric rotary elements, namely, an inner rotary element 53 and an outer rotary element 54 are rotatably mounted in the housing 51. The inner rotary element 53 is adapted for releasably clamping onto the carrier element 35 adjacent the proximal end 36 thereof. The rotary elements 53 and 54 are configured so that for each 360 ^° rotation of the inner rotary element 53, the outer rotary element 54 is incremented by one increment. An outer gauge 55 located on the housing 51 and extending around the outer rotary element 54 is graduated to indicate the number of increments, each of which corresponds to one 360° turn of the inner rotary element 53, through which the inner rotary element 53 has rotated. Ideally, the graduations of the outer gauge 55 are marked to indicate the distance that the piercing point 42 of the piercing tool 3 has advanced from the distal end 28 of the second bore 34 for each 360° turn of the inner rotary element 53. An inner gauge 56 is provided on the outer rotary element 54 around the inner rotary element 53 which is graduated to indicate the distance the piercing point 42 of the piercing tool 3 has advanced from the distal end 28 of the second bore 34 as the inner rotary element 53 is rotated from 0° to 360°. Thus, the distance through which the piercing point 42 of the piercing tool 3 has advanced from the distal end 28 of the second bore 38 can be read directly from the outer and inner gauges 55 and 56.

Alternatively, the monitoring means may be provided by providing a plurality of graduations on the proximal end 36 of the carrier element 35, and each graduation would be marked to indicate the distance that the carrier element 35 is urged into the second bore 34 at the proximal end 15 of the catheter 14, which would correspond with the distance the piercing point 42 of the piercing tool 3 has been advanced from the distal end 28 of the second bore 34. A third bore (not shown) extends through the catheter 14 and through the primary limb 25 from the proximal end 15 of the catheter 14 for accommodating an inflating fluid for inflating the balloon 18. Radial bores (not shown) extending through the primary limb 25 communicate with the third bore for accommodating the inflating fluid from the third bore into the balloon 18. The third bore is sealed adjacent the distal end 16 of the primary limb 25 of the catheter 14.

In use, when it is desired to form a channel 12 through the subintimal space 9 between the inner and outer layers 7 and 8 of the side wall 4 of a blood vessel 5 to bypass an occlusion in the blood vessel 5, such as the occlusion 6, the guide wire 32 is initially urged into the arterial system of the subject, typically, into the femoral artery in the leg of the subject, and is urged through the arterial system into the vessel 5. This procedure will be well known to those skilled in the art. The balloon catheter 1 is then urged over the guide wire 32 until the balloon 18 is located in the vessel 5. The balloon 18 is then partly inflated with a suitable inflating fluid through the third bore (not shown), and the balloon 18 is manoeuvred in the vessel 5 until the distal end 28 of the second bore 34 of the secondary limb 26 is aligned with the site at which the piercing tool 3 is to pierce through the inner layer 7 to form the opening 13 therein. The balloon 18 is then fully inflated for anchoring the balloon 18 in the vessel 5 with the distal end 28 of the second bore 34 aligned with the site at which the piercing tool 3 is to be urged into engagement with the inner layer 7 of the side wall 4. If the carrier element 35 and the piercing tool 3 are not already located in the second bore 34, they are entered into the second bore 34 from the proximal end 15 of the catheter 14. The inner rotary element 53 of the monitoring device 50 is clamped onto the carrier element 35 adjacent the proximal end 36 thereof. The carrier element 35 is then further urged into the second bore until the external screw threads 46 have just engaged the internal threads 44, and the housing 51 of the monitoring device 50 is clamped onto the proximal end 15 of the catheter 14. At this stage the outer gauge 55 and the inner gauge 56 of the monitoring device 50 should be reading 0 distance having been travelled by the carrier element 35, and the piercing point 42 of the piercing tool 3 should coincide with the distal end 28 of the second bore 34.

In order to advance the piercing tool 3 into engagement with the inner layer 7 of the side wall 4, the inner rotary element 53 is rotated for urging the piercing point 42 of the piercing tool 3 into engagement with the inner layer 7 of the side wall 4. The distance that the piercing point 42 of the piercing tool 3 advances outwardly of the distal end 28 of the second bore 34, and in turn has advanced into the inner layer 7 of the side wall 4, is read from the inner gauge 56 and the outer gauge 55 as the inner rotary element 53 is being rotated. The inner rotary element 53 is rotated until the piercing point 42 of the piercing tool 3 has been advanced from the distal end 28 of the second bore 34 a suitable distance to form the opening 13 through the inner layer 7 of the side wall 4 into the subintimal space 9 of the side wall 4.

When the opening 13 has been formed through the inner layer 7 of the side wall 4 into the subintimal space 9, the housing 51 of the monitoring device 50 is disengaged from the proximal end 15 of the catheter 14, and the carrier element 35 and the piercing tool 3 are withdrawn through the second bore 28 from the catheter 14. A suitable tool for forming the channel 12 through the subintimal space 9 is then entered into the second bore 34 at the proximal end 15 thereof and is urged through the second bore 34 to extend through the distal end 28 thereof, and in turn through the opening 13 which has now been formed in the inner layer 7 of the side wall 4, and is urged through the subintimal space 9 to form the channel 12 through the subintimal space 9 in order to bypass the occlusion, such as the occlusion 8. When the channel 12 has been formed through the subinitimal space 9, the boring tool is withdrawn into the second bore 34 and the balloon 18 is deflated, and the balloon catheter 1 is then removed from the vessel through the arterial system of the subject through which it was urged into the vessel 5.

While the balloon catheter has been described as comprising a balloon of cylindrical shape, the balloon may be of any other suitable or desired shape.

While the monitoring means has been described as a specific monitoring device, any other suitable monitoring means for monitoring the distance the piercing point of the piercing tool has advanced from the distal end of the second bore, may be provided.

Additionally, while the internal screw threads have been described as being located in the second bore adjacent the proximal end of the balloon, the internal screw threads may be located in any suitable location in the second bore, and in certain cases, it is envisaged that the internal screw threads may be located closer to the distal end of the second bore, while in other cases, it is envisaged that the internal screw threads may be located at the proximal end of the second bore. Needless to say, the external screw threads on either the carrier element or the piercing tool will be appropriately located depending on the location of the internal screw threads in the second bore. Additionally, in certain cases, it is envisaged that the piercing tool itself may carry the external screw threads, and in which case, the internal screw threads would be located in the second bore adjacent the distal end thereof.

While the tool for forming the opening in the inner layer of the side wall of the vessel has been described as comprising a piercing tool, it is envisaged that any other suitable tool may be used. The tool may, for example, comprise a boring tool or any other suitable tool.