This invention relates generally to the field of catheters and, more particularly, to a catheter sheath for a catheter assembly and to a catheter assembly including the catheter sheath.
In the field of heat treatment of tissue, it is desirable if the device heating the tissue is in contact only with the tissue being treated and that contact with surrounding tissue or bodily fluids is minimised. This reduces the power required to heat the tissue and also minimises unnecessary damage to other tissue, structures or fluid.
In addition, it is often necessary to overcome tissue irregularities at a site in a patient's body being heat treated. An example where a site in a patient's body is subjected to heat treatment is in the treatment of heart arrhythmias where tissue is ablated in an effort to cure the arrhythmia. The tissue is ablated to create a lesion to block the electrical impulses causing the arrhythmia. To ensure that a lesion of adequate depth is formed, it is desirable that the ablating electrode make good contact with the tissue. Other examples of the use of heat treatment at a site in a patient's body include treatment of Parkinson's disease, tumour ablation, endometriosis and pain management.
Still further, in the treatment of arrhythmias, it may be necessary to ablate over a reasonably wide area in an attempt to cure the arrhythmia. It would be beneficial to be able to obtain such larger ablated areas with minimum manipulation of the catheter when in position at the site to be treated.
There is therefore a need for a catheter sheath and a catheter assembly which meets these needs. Such a catheter sheath and catheter assembly could also be useful in other applications, for example, pacing, sensing or defibrillation.
According to a first aspect of the invention, there is provided a catheter sheath which includes
an elongate element defining a primary lumen and a plurality of secondary lumens arranged in spaced relationship about the primary lumen;
a plurality of discrete members defined by the elongate element, the discrete members being displaceable between a first position extending parallel to a longitudinal axis of the elongate element and a second position in which the discrete members extend transversely to the longitudinal axis of the elongate element;
at least one electrode carried by at least one of the discrete members; and
electrical conductors for the at least one electrode arranged in the primary lumen, the primary lumen being shaped to accommodate the conductors.
An inner surface of a wall of the elongate element defining the primary lumen may be recessed to define at least one axially extending channel in which the conductors are receivable. Preferably, each discrete member carries at least one electrode and a plurality of circumferentially spaced channels may be defined in the inner surface of the wall of the elongate element, each discrete member having a channel associated with it.
The at least one electrode of each discrete member may be arranged on an operatively inner surface of its associated discrete member. By “operatively inner surface” means that surface of the discrete member which, when it is in its first position, faces an opposed discrete member.
The discrete members may be defined by the elongate element. More particularly, the discrete members may be defined by longitudinally extending slits at least at the distal end of the elongate element. The catheter sheath may include a sleeve with the elongate element being mounted on a distal end of the sleeve. In an embodiment, the slits may extend the full length of the elongate element. The discrete members may be retained in position relative to each other by being attached to the distal end of the sleeve. It will be appreciated that the discrete members could be attached within the distal end of the sleeve or to an external surface of the distal end of the sleeve.
A control element, in the form of a pull wire, may be received in each secondary lumen, each control element being connected to one of the discrete members and the control element controlling movement of its associated discrete member at least from its first position to its second position.
The catheter sheath may include an urging means associated with each discrete member for urging the discrete member from its second position to its first position. Each urging means may be a resiliently flexible component having at least a portion inwardly of a centre plane, or plane of bending, of its associated discrete member. Thus, each flexible component may be attached to an inner surface of the discrete member, i.e. in the primary lumen or, instead, each flexible component may be arranged in the secondary lumen of its associated discrete member inwardly of the control element.
According to a second aspect of the invention, there is provided a catheter assembly which includes
a handle having a proximal end and a distal end;
a catheter sheath as described above attached to a distal end of the handle; and
a control mechanism carried by the handle, the control elements of the catheter sheath being connected to the control mechanism.
The assembly may include a stylet received in the primary lumen of the elongate element of the catheter sheath. Preferably, the stylet is a steerable stylet for effecting steering of the catheter sheath, in use.
The handle may include a steering control mechanism to which the stylet is connected for effecting steering of the stylet.
A distal end of the stylet may carry an end electrode. In an embodiment, the end electrode may be a dome electrode.
The end electrode may be arranged to lie substantially in the same plane as the at least one electrode of the at least one discrete member when that discrete member is in its second position. For this purpose, the stylet and the catheter sheath may be axially displaceable with respect to each other so that, when the discrete members of the elongate element of the catheter sheath are in their second position, the end electrode can be brought into substantially the same plane as the at least one electrode of the at least one discrete element.
In another embodiment, the end electrode may be a needle electrode.
The control mechanism may include a plurality of control members, each control member being connected to one of the control elements of the catheter sheath so that movement of each discrete member can be effected independently of the remaining discrete members. Each control member may be in the form of a slide which is slidable axially in the handle. The control mechanism may include a connector, in the form of a collar, for interconnecting the control members to effect simultaneous control of the discrete members of the catheter sheath.
In the drawings, reference numeral 10 generally designates an embodiment of a catheter sheath. The catheter sheath 10 comprises an elongate element 12. The catheter sheath 10 further includes a plurality of discrete members, or petals, 14 defined by, and arranged at a distal end of, the elongate element 12. The petals 14 are formed by slits 16 cut in the distal end of the elongate element 12.
In another embodiment, the slits 16 could extend the full length of the elongate element 12, with the elongate element 12 then being supported by a sleeve (not shown). The elongate element 12 could be attached to an inner surface or an outer surface of the sleeve to be supported by the sleeve.
The elongate element 12 is in the form of a tube and defines a central lumen 18. The central lumen 18 is a primary lumen and is surrounded by a plurality of secondary lumens 20. Each petal 14 has a secondary lumen 20 associated with it.
As shown most clearly in
Each electrode 22 has a group of conductors associated with it. As illustrated most clearly in
Spaced channels, or recesses, 26 (
The catheter sheath 10 includes a control element in the form of a pull wire 28 (
The catheter sheath 10 is of a plastics material. The plastics material may be a medical grade plastics material such as that sold under the trade name PEBAX or it may be an elastomeric material such as a suitable silicone composition. In the latter case, in the event that the material is too flexible to allow the petals 14 to adopt their first position after they have been in their second position, the catheter sheath 10 includes an urging means in the form of a strip 32 (
In the embodiment illustrated in
The embodiment of the catheter sheath 10 shown in
In
The catheter assembly 40 includes a control mechanism 50 for controlling displacement of the petals 14 of the elongate element 12 of the catheter sheath 10 between the first position as shown in
To facilitate simultaneous movement of the petals 14 from their first, closed position to their second, open position, the control mechanism 50 includes a connector in the form of a collar 54 receivable over the slides 52 as shown in
The pull wire 28 of each petal 14 is connected to its associated slide 52 as shown in greater detail in
In order to effect steering of the catheter sheath 10, the catheter assembly 40 includes a stylet 56 (
The stylet 56 supports an end electrode 64 on its distal end. In the illustrated embodiment, the end electrode 64 is a dome electrode and is supplied with energy via the conductive actuator 60. The electrode 64 is mounted on the distal end of the tubular member 58 via a force absorbing element in the form of a bellows-like member 66.
In other embodiments (not illustrated), the end electrode 64 could be a needle electrode for effecting transmural ablation of tissue at a site in a patient's body.
The tubular member 58 has, proximally of its distal end, a bend-enhancing region in the form of a longitudinally extending cut-away portion (not shown). The cut-away portion subtends an angle of approximately 270° to leave a longitudinally extending spine of material. The actuator 60 is mechanically fast with the distal end of the tubular member 58 so that, by relative axial displacement between the tubular member 58 and the actuator 60, bending of the tubular member and, accordingly, the catheter sheath 10 about the bend-enhancing region of the tubular member 58 is effected. Thus, although not illustrated, the actuator 60 has it proximal end fast with the handle 42. The tubular member 58 of the stylet 56 is connected to a steering control mechanism 68 (
In the illustrated embodiment, the end electrode 64 is fixedly positioned relative to the catheter sheath 10 and, when the petals 14 are in their closed position, they envelop the end electrode 64. When the petals 14 are displaced to their open position, the end electrode 64 lies substantially in the same plane as the electrodes 22 of the petals 14 as shown in
In another embodiment, the end electrode 64 is mounted distally of the petals 14 when they are in their closed position and the stylet 56 is displaceable relative to the electrode sheath 10 to bring the electrode 64 into the same plane as the electrode 22 of the petals 14 when the petals 14 are in their open position. Thus, the catheter assembly 40 includes a projection control mechanism 70 (
The cables forming the ribbon cable 24 are bundled together into an electrical cable 72 which passes through the handle 42 exiting at the proximal end 44 of the handle 42. In addition, the handle 42 accommodates an irrigation conduit 74 for the transmission of irrigation fluid through the primary lumen 18 to irrigate the site at the patient's body at which ablation is being effected.
The petals 14 are marked with radio opaque marker in order to be able to identify the petals 14. In the illustrated embodiment, the radio opaque markers are a different number of bands 76 (
The catheter assembly 40 is used in the heat treatment of a site in a patient's body. A particular application of the catheter assembly is ablation treatment in the treatment of heart arrhythmias. The catheter sheath 10, with the petals 14 in their closed position, is fed through the vasculature of the patient to the desired region in the heart at which the heart arrhythmias are to be treated. At the chosen site, the control mechanism 50 is operated to open the petals 14 so that they adopt their second position as shown, for example, in
The electrodes 22 are energised with out-of-phase energy as described in greater detail in the Assignee's co-pending International Patent Application No. PCT/AU03/01421 dated 28 Oct. 2003 and entitled “System for, and method of, heating a biological site in a patient's body”.
As described in that International Application, the energy supplied to any one electrode is 180° out of phase with the energy supplied to any other electrode. The sum of the energy is, however, still the same and, using this method, longer but shallower legions are formed resulting in less trauma at the treated site in the patient's body. In addition, the shape of the strip electrodes 22 promotes the formation of longer lesions at the site thereby reducing the time taken to complete an ablation procedure.
In the case where the end electrode 64 is a needle electrode, the catheter assembly 10 could be used in the treatment of ventricular tachycardia. To enable tissue to be treated, the needle electrode 72 is carried on the distal end of the stylet 56. Because penetration of the tissue is required, the bellows-like member 66 is omitted. With this arrangement, the needle electrode enters the tissue to be treated and is used in combination with one or more of the strip electrodes 22.
It is therefore an advantage of the invention that a catheter sheath 10 is provided which is able to be manipulated into a configuration where longer, shallower lesions can be formed thereby reducing time for completing an ablation procedure. The use of the petal-like arrangement at the distal end of the catheter sheath 10 enables a larger area of the site to be treated. Further, the use of the out-of-phase energy facilitates treatment of such a larger area. A further advantage is that, because the strip electrodes 22 are long and cover a larger area, reduced manipulation of the catheter sheath 10, while in the patient's body, is required.
As indicated above, the use of long strip electrodes 22 provides for shallow lesions to be formed at the site which reduces trauma but is also more effective in the treatment of heart arrhythmias.
It is yet a further advantage of the invention that the petals 14 are resiliently flexible, either as a result of the plastics material from which they are made or with the addition of the Nitinol strips 32. This promotes tissue-electrode contact and reduces the risk of inadequate contact as a result of surface irregularities.
It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.
The present application claims priority from U.S. Provisional Patent Application No. 60/995,791 filed on Sep. 28, 2007, the contents of which are incorporated herein by reference in their entirety.
Number | Date | Country | |
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60995791 | Sep 2007 | US |