WO2012131634A1

WO2012131634A1 - Intra-cardiac catheter anchor attachment

Info

Publication number: WO2012131634A1
Application number: PCT/IB2012/051556
Authority: WO
Inventors: Heather B. KNOWLES
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2011-03-30
Filing date: 2012-03-30
Publication date: 2012-10-04

Abstract

A cable (138, 140, 141, 142) is terminated to a structure internal to an elongated catheter housing (124) to prevent the cable from being pulled out, as when pulled in steering the catheter. The structure may be an ultrasound transducer assembly (102). The catheter may be an intracardiac echocardiography (ICE) catheter. The cable is terminated at a connection made by soldering, looping and tying, gluing, etc. By way of example, the structure, as dimensioned, in cross-section (145), and configured, would not, if pulled, fit into the pull cable passageway. This creates a secure,physical tie in that it does not rely, for its strength, on the surface adhesion afforded by polymer that has been melted onto the cable as a counter to the shear force applied when the cable is pulled.

Description

INTRA-CARDIAC CATHETER ANCHOR ATTACHMENT

FIELD OF THE INVENTION

The present invention is directed to anchoring a cable in a catheter so as to resist being pulled out and, more particularly, to anchoring where the cable terminates.

BACKGROUND OF THE INVENTION

Intracardiac echocardiography (ICE) is becoming an important tool for diagnosis and treatment of many cardiac abnormalities such as endocarditis, atrial septal defects (ASD), patent foramen ovale (PFO), ventricular septal defects (VSD), left atrial appendage occlusion and the treatment of atrial fibrillation.

A catheter, such an ICE catheter, is often steered by means of one or more pull cables. The pull cables run the full length of the catheter between the catheter handle and the interventional part of the catheter. The interventional part is inserted into a blood vessel of the patient under treatment or being examined and fed toward the heart. The technician uses the catheter handle to manipulate the pull cables, thereby steering a part of the catheter distal from the bending neck. At the bending neck, the housing is more flexible to allow the bending, and the placement of pull cable guide holes determines the direction in which the catheter is steered when the cable is pulled. The distal part contains imaging apparatus and may further have, for example, angioplasty or ablation capability.

The problem of keeping the cables from being pulled loose is addressed in a number of ways. One method is to loop the cable around inside the catheter material. Another method terminates stranded cables into the catheter bulk material during the radiofrequency (RF) bonding which forms the catheter housing.

SUMMARY OF THE INVENTION

The present inventor has observed that the above-cited pull cable termination methods have shortcomings. Although looping the cable within the bulk material improves strength, because it does not allow for pull out, it increases bulk because the diameter of the wire must now be added to the wall thickness.

The second method, of terminating the cable in the catheter bulk material, requires melting the catheter material with the sensor in place, and relies on surface area to provide strength, making a thick section necessary.

Both methods require a stiff material to be present in order to attach firmly enough to it to provide strength, distal to the bending neck.

The present inventor has found the need for the additional stiff area, commonly called an anchor, to be disadvantageous, since this region beyond the bending neck ideally bends.

The catheter proposed herein below does not require the additional stiff area. The reduced bend radius facilitates navigation to the region of interest.

Nor is a loop of wire needed. With thinner catheter walls, less bulk material is required for the housing. In addition, eliminating the loop decreases the length of wire needed by about 60%. Also, catheter diameter can be kept short which further facilitates navigation or, alternatively, for the same diameter, the present catheter has more internal space for imaging and treatment devices.

Both features, a reduced anchor area and lack of need for a looped wire, simplify manufacture.

The present methodology creates a secure, physical tie in that it does not rely, for its strength, on the surface adhesion afforded by polymer that has been melted onto the cable as a counter to the shear force applied when the cable is pulled.

In accordance with an aspect of the present invention, a catheter includes an elongated housing, a structure radially internal to the housing, and a cable terminating at the structure to resist being pulled out.

According to a further aspect, the terminating physically secures the cable directly to the structure.

In another aspect, the structure as dimensioned, in cross-section, and configured would not, if pulled, fit into an orifice for the cable. In an additional aspect, the cable is disposed longitudinally along the housing and turns inward to attach to the structure.

As a sub-aspect, the attachment is relied upon for steering.

In a different aspect, the structure is disposed at a distal tip of the housing.

In a sub-aspect of the above, the structure is encased in a block of material.

As a further sub-aspect of the above, the block of material and the structure internally fill the tip.

In an associated sub-aspect, the material is acoustic material.

In a yet one more associated aspect, the block is integral with the catheter such that a bond between the block and the catheter keeps the cable, when pulled at a proximal end, in tension.

In one variation, the structure includes a transducer assembly, and the cable terminates at the assembly.

In a sub-aspect, the assembly includes a printed circuit board (PCB), and the cable terminates at the PCB.

In an additional sub-aspect, the PCB includes a flexible circuit, and the cable terminates at the flexible circuit.

As an alternative or supplementary sub-aspect, the assembly has a support platform for a transducer, and the cable terminates at the platform.

As a yet further sub-aspect, the platform includes a heat sink, and the cable terminates at the heat sink.

In a related aspect, the cable terminates at the structure in a soldered connection.

In a similar, alternative aspect, the cable terminates at the structure in a looped and tied connection.

In one more aspect, the catheter is configured for insertion into a blood vessel.

In yet one further aspect, the cable is configured for steering the catheter.

In a yet additional aspect, the cable extends to a proximal end of the housing. Details of the novel, catheter pull cable termination technology are set forth further below, with the aid of the following drawings, which are not drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exemplary schematic diagram of a catheter whose pull cables are terminated to a side-facing transducer assembly;

FIG. 2 is an exemplary schematic diagram of a catheter whose pull cables are terminated to a front-facing transducer assembly; and

FIG. 3 is a flow chart on one way of making the catheters of FIGs. 1 and 2.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 depicts, by way of illustrative and non-limitative example, a cross-section of a catheter 100 with a side-facing transducer assembly 102. The catheter 100 can be inserted into a blood vessel 103. The catheter 100 is designed for circumferential rotation for imaging. This can be done manually or by a mechanism, and for the whole catheter 100 as in the present embodiment, the assembly 102 or the transducer in the assembly.

The transducer assembly 102 includes a piezoelectric transducer (PZT and associated matching layers) 104, and, in front, an acoustic window 106. Further included are a support platform 108 and a pair of flexible circuits 1 10, 112. The support platform 108 incorporates a semiconductor chip 1 14, interfaced to the PZT 104 by an interconnect layer 116. The support platform 108 also includes a backing layer 1 18. Further making up the transducer assembly 102 are conductors 120, 122 between pads (not shown) on the chip 114 and the respective flexible circuits 110, 112.

The catheter 100 has a housing 124 that, along with the acoustic window 106, covers a distal tip 126 of the catheter. The interventional portion of the housing 124 extends, as shown by the broken line 128, longitudinally back past a bending neck 130 and ends near a handle at a proximal end 132 of the catheter 100. Longitudinal orifices or lumens 134, 136 of the catheter 100 serve as passageways for included cables, wires or cords 138, 140 that can be pulled in the direction of the down arrows shown in FIG. 1. The pull cables 138, 140 are terminated to opposite sides of the transducer assembly 102, only the termination of the front pull cable 138 being visible in FIG. 1. Left and right pull cables 141, 142 without lumens are terminated to respective opposite sides on the back of the flexible circuit 1 10. Here too, only the termination of the left pull cable 141 is shown in FIG. 1. Alternatively, lumens can be provided for none or all of the four pull cables 138, 140, 141, 142. At the bending neck 130, all four pull cables 138, 140, 141, 142 pass through respective pull cable guide holes (not shown). The guide holes may run longitudinally and be disposed in the catheter bulk, or internal lumens attached to the catheter walls, at 90° circumferential intervals. The distal ends of the front and left pull cables 138, 141 are visible in FIG. 1 and terminate at respective attachment locations 143, 144. The pull cables 138, 140, 141 , 142 can be made of metal, or a strong polymer like nylon or ultra-high molecular weight polyethylene (UHMWPE). The housing 124 may be formed of a nylon resin which serves as an acoustic material, such as polyether block amide. An example of the latter is PEBAX™ (sold by Elf Autochem™). A relatively soft form of PEBAX™, e.g., grade 2533, can form the housing portion at the distal tip 126, including the acoustic window 106. A protective layer may be disposed in front and/or in back of the acoustic window to protect the window from chemical exposure, as in the case in which the catheter is reusable and therefore cleansed between uses. Example of window configurations are provided in United States Patent

Publication 2005/0165312 to Knowles et al. and U.S. Patent No. 7,194,919 to Shkarlet et al. which are incorporated herein by reference in their entirety. The same material can be used for the remaining part of the catheter 200 distal from the bending neck 130.

Somewhat harder PEBAX™, of grade 3533 for example, can be utilized proximal to the bending neck 130.

The terminating of the distal ends of the cables 138, 140, 141, 142 to respective internal structures 1 14, 1 10 physically secures the cables to the structures. As seen from FIG. 1, the structure 114 as dimensioned, in cross-section 145 (in the plane of the drawing sheet and adjacent to the lumen 134), and configured, if pulled, would not fit into the lumen. In this respect and by way of example, a sufficiently large block of rigid plastic, e.g., polystyrene or polycarbonate, may alternatively serve as the structure. To physically secure the cables 138, 140, 141, 142 to the internal structure 114, 1 10, they could, for instance, be looped through a hole in the structure and tied, soldered, glued, or looped around the structure and further fastened as by a tie. The feature of cables 138, 140, 141 , 142 turning inward at the attachment point, as best seen in the front cable 138, creates additional resistance owing to the change in direction.

The attachments of the cables 138, 140, 141 , 142 to the respective structures 1 14,

1 10 are relied upon for steering. In particular, a block 150 of material, which includes the portion of the housing 124 at the distal tip 126, encases the transducer assembly. That portion is integral with the rest of the housing such that a bond 152 between the portion and the rest of the housing keeps the cable 138, 140, 141 , 142, when pulled at the proximal end 132, in tension. The block 150 of material, along with the transducer assembly 102, internally fill the distal tip 126. Merely one or two of the pull cables 138, 140, 141 , 142 may be implemented or any larger number of pull cables. Termination can occur to any part(s) of the internal structure, since it is the configuration of the pull cable guide hole(s) that determines steering directionality in response to pulling the cables 138, 140, 141, 142. Nevertheless, for purposes of attachment strength and to more closely match the lumen opening position, separate attachment locations are preferable. In an alternative configuration, the chip 1 14 could be omitted, with connection being made instead to the interconnect layer 116, and cable attachment being made, for example, to the backing layer 118.

An example of a catheter 254 with a forward- facing transducer assembly 256 is provided, in cross-section, in FIG. 2. The transducer assembly 256, encased in a block 258 of material at a distal tip 260 of the housing 262, includes an acoustic window 264, a PZT 266 and a support platform 268. The latter is made up of printed circuit board (PCB) 270, a backing layer 272, and a heat sink 274. Other possible catheter

configurations could be constructed from components shown in FIGs. 1 and 2, and other components, in any known and suitable combination.

As shown in FIG. 2, pull cables 276, 278, in corresponding lumens 280, 282, run alongside the housing 262, which includes an additional, annular, inner part 283 of the same composition or mouldable resin for example. The lumens 280, 282, as indicated by the broken lines to the internal structure, may be fastened to any one (or more) of the PCB 270, backing layer 272 and heat sink 274 by respective terminations 286-296.

Illustratively, the termination 286 to the PCB 270 consists of a loop of the cable 278 through a hole in the PCB, the loop being tied, i.e., a looped and tied connection. The termination 290 to the heat sink 274 is accomplished by a soldered connection. A bond 298 joins the distal tip 260 of the catheter 254 to the rest of the catheter.

Although the lumens 134, 136, 280, 282 are shown in FIGs. 1 and 2 as radially internal to the housing 124, 262, they may be embedded within the housing bulk material. The pull cable termination proposed herein can alternatively be to other internal structures, such as, for example, to an annular fiber optic cable surrounding a capacitive machined ultrasound transducer (CMUT) array in a photoacoustic device. Attachment can be made with epoxy for example. Or termination, by an adhesion or otherwise, can be made to a support platform of a navigation sensor, as another example.

One process for making the catheters 100, 254 is shown in FIG. 3. The transducer assembly 102, 256 is made (step S310). The pull cables 138, 140, 141, 142, 276, 278 are attached firmly at respective terminations to resist detachment, i.e., being pulled out or loose (step S320). The assembly 102, 256, including the attachment points are, by RF bonding, encased in a block 150, 258 of material (step S330), to form the catheter distal tip 126, 260. The rest of the catheter housing 124, 262 is separately formed, with this portion of the housing 124, 262 surrounding corresponding lumens 134, 136, 280, 282 (step S340). Into their respective cross-sections, the internal structures, if pulled, would not fit. This is due to the shape of the cross-sections of the internal structures and to their relative inflexibility if they were to be pulled against the openings of the respective lumens 134, 136, 280, 282. Free ends ofthe cables 138, 140, 141 , 142, 276, 278 are inserted into their respective lumens 134, 136, 280, 282, if any (step S350), and drawn in to bring the separately formed housing portion in proximity of the block 150, 258 of material (step S360). A bond 152, 298 is then formed between the separately formed housing portion and the block 150, 258 of material, to complete the catheter 100, 254 (step S370).

A cable is terminated to a structure internal to an elongated catheter housing to prevent the cable from being pulled out, as when pulled in steering the catheter. The structure may be an ultrasound transducer assembly. The catheter may be an intracardiac echocardiography (ICE) catheter. The cable is terminated at a connection made by soldering, looping and tying, gluing, etc. By way of example, the structure, as dimensioned, in cross-section, and configured, would not, if pulled, fit into the pull cable passageway. This creates a secure, physical tie in that it does not rely, for its strength, on the surface adhesion afforded by polymer that has been melted onto the cable as a counter to the shear force applied when the cable is pulled. While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

For example, the pull cable termination might be applied to a camera within an intra-uterine or intra-cervical diagnostic catheter for animals or human beings. Also, the termination 144 of the left pull cable 141 , and the termination for right pull cable 142, to the flexible circuit 1 10 can be disposed, for instance, further down toward the proximal end of the flexible circuit.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. Any reference signs in the claims should not be construed as limiting the scope.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS What is claimed is:

1. A catheter (100) comprising:

an elongated housing (124);

a structure radially internal to said housing; and

a cable (138) terminating at said structure to resist being pulled out.

2. The catheter of claim 1 , said terminating physically securing said cable directly to said structure (S320).

3. The catheter of claim 1 , wherein said structure as dimensioned, in cross-section (145), and configured would not, if pulled, fit into an orifice for said cable.

4. The catheter of claim 1, said cable, disposed longitudinally along said housing, turning inward to attach (144) to said structure.

5. The catheter of claim 4, the attachment (143) being relied upon for steering.

6. The catheter of claim 1 , said structure being disposed at a distal tip (126) of said housing.

7. The catheter of claim 6, said structure being encased in a block (150) of material.

8. The catheter of claim 7, said block of material and said structure (102) internally filling said tip.

9. The catheter of claim 7, said material being acoustic material.

10. The catheter of claim 7, said block being integral with said catheter such that a bond (152) between said block and said catheter keeps said cable, when pulled at a proximal end, in tension.

11. The catheter of claim 1, said structure comprising a transducer assembly, said cable terminating at said assembly (S320).

12. The catheter of claim 11 , said assembly comprising a printed circuit board (PCB), said cable terminating at said PCB (1 14).

13. The catheter of claim 12, said PCB comprising a flexible circuit (110, 1 12), said cable terminating at said flexible circuit.

14. The catheter of claim 1 1, said assembly having a support platform (108) for a transducer, said cable terminating at said platform.

15. The catheter of claim 14, said platform comprising a heat sink (274), said cable terminating at said heat sink.

16. The catheter of claim 1, said cable terminating at said structure in a soldered connection (290).

17. The catheter of claim 1, said cable terminating at said structure in a looped and tied connection (286).

18. The catheter of claim 1 , configured for insertion into a blood vessel (103).

19. The catheter of claim 1, said cable (138, 140, 141 , 142) configured for steering said catheter.

20. The catheter of claim 1, said cable extending to a proximal end (132) of said housing.

21. A method for making a catheter having an elongated housing comprising:

disposing a cable for resistance to being pulled out, by terminating said cable at a structure radially internal to said housing (S320).