Abstract:
Catheter shaft handles and deflection actuators are disclosed. The actuators include at least one pull wire guide wall and a means for anchoring the proximal portion of a pull wire or of a fiber attached to a pull wire. Each actuator is pivotable relative to the catheter handle housing, and may comprise at least one boss for pivoting the actuator relative to the catheter handle housing. The actuators transfer rotational motion based upon user input on a boss into longitudinal motion of a pull wire. The actuators may include a tensioning mechanism comprising a tension adjustment pin and a pin block, wherein the tension adjustment pin is rotatably attached to the pin block to enable adjustment of tension in a pull wire (e.g., during assembly of the catheter handle).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application No. 61/820,613, filed 7 May 2013, which is hereby incorporated by reference as though fully set forth herein. 
     
    
     BACKGROUND 
       [0002]    a. Field 
         [0003]    The instant disclosure relates to steering mechanism or actuators for steerable medical devices. In particular, the instant disclosure relates to actuators in steerable medical devices employing one or more pull wires to deflect a portion of such medical devices in at least one direction and, preferably, in at least two directions. 
         [0004]    b. Background Art 
         [0005]    Electrophysiology catheters are used in a variety of diagnostic, therapeutic, and/or mapping and ablative procedures to diagnose and/or correct conditions such as atrial arrhythmias, including for example, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter. Arrhythmias can create a variety of conditions including irregular heart rates, loss of synchronous atrioventricular contractions, and stasis of blood flow in a chamber of a heart, which can lead to a variety of symptomatic and asymptomatic ailments and even death. 
         [0006]    Typically, a catheter is deployed and manipulated through a patient&#39;s vasculature to the intended site, for example, a site within a patient&#39;s heart. The catheter typically carries one or more electrodes that can be used for cardiac mapping or diagnosis, ablation, and/or other therapy delivery modes, or both, for example. Once at the intended site, treatment can include, for example, radio frequency (RF) ablation, cryoablation, laser ablation, chemical ablation, high-intensity focused ultrasound-based ablation, microwave ablation, and/or other ablation treatments. The catheter imparts ablative energy to cardiac tissue to create one or more lesions in the cardiac tissue. These lesions disrupt undesirable cardiac activation pathways and thereby limit, corral, or prevent errant conduction signals that can form the basis for arrhythmias. 
         [0007]    To position a catheter within the body at a desired site, some type of navigation must be used, such as using mechanical steering features incorporated into the catheter (or an introducer sheath). In some examples, medical personnel may manually manipulate and/or operate the catheter using the mechanical steering features. 
         [0008]    In order to facilitate the advancement of catheters through a patient&#39;s vasculature, the simultaneous application of torque at the proximal end of the catheter and the ability to selectively deflect the distal tip of the catheter in a desired direction can permit medical personnel to adjust the direction of advancement of the distal end of the catheter and to selectively position the distal portion of the catheter during an electrophysiological procedure. The proximal end of the catheter can be manipulated to guide the catheter through a patient&#39;s vasculature. The distal tip can be deflected by a pull wire attached at the distal end of the catheter and extending proximally to an actuator in a control handle that controls the application of tension on the pull wire. 
         [0009]    The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope. 
       BRIEF SUMMARY 
       [0010]    The present invention generally relates to steering actuators for deflectable medical instruments, including catheters. Representative embodiments include steerable catheters having pull wires or pull strings or tensioning members extending from a deflectable section to an actuator. The deflectable section may comprise, for example, part of a catheter shaft and may be located at or near a distal end of that catheter shaft, although the disclosure is equally applicable to devices having shaft deflection areas at any point(s) along the shaft. The actuator may be located at or near the proximal end of the catheter, typically within or on some type of handle. 
         [0011]    In an embodiment, a steering actuator comprises (a) an inner actuator adapted to be rotatably mounted within a catheter handle housing, and (b) an outer actuator attached to the inner actuator. The inner actuator may comprise, for example, a base plate; at least one pull wire guide wall attached to the base plate and configured to pressingly engage a pull wire during at least a portion of the rotation of the inner actuator; and at least one tuner mechanism comprising a tuning pin and a pin block, wherein the tuning pin is rotatably attached to the pin block to enable initial adjustment of tension in the pull wire. The outer actuator may comprise at least one boss (e.g., a protuberance or thumb boss against with a user applies pressure). 
         [0012]    In another embodiment, a steering actuator comprises (a) an inner actuator rotatably mounted within a catheter handle housing, and (b) a user-manipulatable actuator attached to the inner actuator to facilitate user rotation of the inner actuator. In this environment, the inner actuator may comprise, for example, at least one pull wire guide wall, each pull wire guide wall contoured against a respective pull wire to change the tension of the respective pull wire in response to rotation of the inner actuator; and at least one tension mechanism, each tension mechanism comprising a respective tension adjustment pin and a pin block to enable initial tension adjustment of the respective pull wire. 
         [0013]    In yet another embodiment, a control handle comprises the following: (a) a handle housing; (b) a first curved, pull-wire-deflection surface mounted to the housing; and (c) a steering actuator at least partially sandwiched within the handle housing and configured to apply tension to a first pull wire. The steering actuator may comprise, for example, the following: (i) a first actuator component pivotably mounted within the handle housing, and (ii) a second actuator component attached to the first actuator component, the second actuator component comprising at least one boss. The first actuator component may further comprise a first pull wire guide wall configured to affect a pull wire path length traveled by the first pull wire or fiber during actuation of the steering actuator; and a first pull wire or fiber anchor. It should be noted that, in various embodiments, the first actuator component and the second actuator component comprise a unitary component. It should also be noted that, in various embodiments, an automatic or manual lock may be present and operable to releasably hold tension applied to one or more pull wires by the steering actuator. The first pull wire guide wall may comprise, for example, an arc wall section, a C-shaped wall, a U-shaped wall, a flattened-semicircular-shaped wall, a semicircular-shaped wall, or a horseshoe-shaped wall. 
         [0014]    In another embodiment, a catheter comprises a longitudinally-extending catheter shaft comprising a proximal end portion and a distal deflectable section; a handle attached to the proximal end portion of the catheter shaft, the handle including a handle housing; a first pull wire extending along the catheter shaft and comprising a distal end portion attached to the distal deflectable section of the catheter shaft, and a proximal end portion; and a steering actuator comprising an inner actuator pivotally mounted within the handle housing and comprising a first guide wall and a first pull wire anchor point, wherein the first pull wire is attached to the first pull wire anchor point, and wherein the first guide wall is configured to affect a pull-wire-path length traveled by the first pull wire during actuation of the steering actuator whereby the steering actuator is operable to tension the first pull wire to thereby deflect the distal deflectable section of the catheter shaft. 
         [0015]    The foregoing and other aspects, features, details, utilities, and advantages of the present invention will be apparent from reading the following description and claims, and from reviewing the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is an isometric view of a catheter handle having a steering actuator for deflecting a catheter shaft. 
           [0017]      FIG. 2  is an isometric view of the catheter handle and actuator depicted in  FIG. 1 , but with the upper handle housing exploded away from the handle to reveal internal components of the steering actuator. 
           [0018]      FIG. 3  is similar to  FIGS. 1 and 2 , but depicts several components exploded above and below the upper and lower handle housings to reveal details about the inner workings of the steering actuator. 
           [0019]      FIG. 4  is an enlarged view of the circled portion labeled AA in  FIG. 2 . 
           [0020]      FIG. 5  is similar to  FIG. 4 , but depicts various components of the steering actuator spread apart to make it easier to see some aspects of the construction. 
           [0021]      FIG. 6  is an isometric view looking at the underside of the outer knob of the actuator, depicting the splines or teeth of the internal gear comprising part of the outer knob. 
           [0022]      FIG. 7  is similar to  FIG. 1 , but depicts another catheter handle, including an alternative steering actuator for deflecting a catheter shaft. 
           [0023]      FIG. 8  is a fragmentary, isometric view of the catheter handle and steering actuator depicted in  FIG. 7 , but with the upper handle housing removed to reveal several components of the steering actuator. 
           [0024]      FIG. 9  is a top view of a catheter handle including a steering actuator for deflecting a catheter shaft. 
           [0025]      FIG. 10  is a longitudinal cross-sectional view taken along line  10 - 10  of  FIG. 9 . 
           [0026]      FIG. 11  is an enlarged view of the circled portion labeled BB in  FIG. 10 . 
           [0027]      FIG. 12  is a cross-sectional view taken through the center of the steering actuator, along line  12 - 12  of  FIG. 9 . 
           [0028]      FIG. 13  is a fragmentary, isometric view of a portion of the left side and top of the catheter handle and actuator depicted in  FIGS. 7-12  with the front portion of the upper handle housing removed to reveal various internal components. 
           [0029]      FIG. 14  is a fragmentary, isometric view of a catheter handle and steering actuator comprising an alternative, forward-facing guide wall. 
           [0030]      FIGS. 15-17  schematically depict a portion of another embodiment of a steering actuator comprising an alternative, rearward-facing guide wall. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0031]    Referring now to the figures, in which like reference numbers refer to the same or similar features in the various views,  FIG. 1  is an isometric view of a catheter handle  10  comprising a steering actuator  12  for deflecting a catheter shaft  14 . In  FIG. 1 , only a short section of catheter shaft is depicted distal of a strain relief  16 , and the deflectable section or tip of the catheter shaft is not shown. As shown in this figure, the handle comprises an upper handle housing  18  and a lower handle housing  20 . A steering actuator  12  is pivotally sandwiched between the upper and lower handle housings, and includes an outer actuator  22  and an outer knob  24 . The outer actuator  22  defines a first boss  26  and a second boss  28  that a user (e.g., an electrophysiologist or other clinician) uses to effect deflection of the catheter shaft. 
         [0032]      FIG. 2  also depicts the representative catheter handle  10  and steering actuator  12  shown in  FIG. 1 , but with the upper handle housing exploded away from the rest of the handle, revealing several components of the actuator. As shown in this figure, the proximal end of the catheter shaft  14  is supported by a strain relief  16 . Pull wires  30 ,  32  (both more clearly visible in  FIG. 3 ), which extend from the handle down the catheter shaft to an anchor point (not shown) in a deflectable section (not shown) of the catheter, enter the handle from its distal end. In this embodiment, each pull wire is then attached by a connecting member, such as a crimp  34 , to a fiber  36  that extends from the crimp to an anchor point  38  (e.g., a tensioning mechanism, embodiments of which are described more fully below). The fiber comprises a durable material that is selected to handle the circuitous path (and concomitant stresses) that the fiber follows from the crimp  34  to the anchor point  38 . As will be discussed further below, each fiber passes over a roller  40  (or pull-wire-deflection surface), then passes around a wall section (or guide wall or pull wire guide wall)  42  before reaching one of the anchor points  38 . In the embodiment shown in  FIG. 2 , the first and second wall sections (or guide walls)  42 ,  44  comprise arc wall sections or “wing wall” sections. These wall sections increase the length of the path traversed by the fiber (or a pull wire) after passing the roller on its way to the mounting point of the proximal portion of the fiber. 
         [0033]      FIG. 3  is an exploded, isometric view of the embodiment of the representative catheter handle and steering actuator shown in  FIGS. 1 and 2 . As may be seen toward the bottom of  FIG. 3 , the outer actuator  22  comprises a mounting mechanism, which is depicted as a pair of mounting posts  46 ,  48  in the illustrated embodiment. When the actuator is assembled with the catheter housing, these mounting posts pass through arcuate post slots  50 ,  52  in the lower handle housing  20 , and then ride in lateral screw pillars  54 ,  56  (shown more clearly in  FIGS. 4 and 5 ) that extend upwardly from a base plate  58  comprising part of the rotating inner actuator  60 . The outer actuator  22  is attached to the inner actuator  60  by two mounting screws  62 ,  64 . In particular, the shafts of the two mounting screws pass through a hole in the center of each lateral screw pillar and are threaded into a respective one of the mounting posts, which may or may not be internally threaded. The heads of the mounting screws, once the screws are installed, rest in a screw seat formed in the top surface of each lateral screw pillar. 
         [0034]    Still looking at  FIG. 3 , a central hex-head screw  66  may be used to assemble the steering actuator to the handle housings. The head of this hex-head screw is retained in a head base  68  comprising part of the lower handle housing. A Belleville washer (or conical spring washer)  70  is then slid onto the shaft of the hex-head screw. The Belleville washer applies a preload to the actuator mechanism. A washer  72  (e.g., a washer made from Delrin® or another plastic material) is then placed on top of the Belleville washer, before the hex-head screw passes through a central screw pillar  74 . Once the shaft of the hex-head screw passes through the central screw pillar, a PEEK washer  76  is placed on the shaft of the hex-head screw before the shaft of the screw is passed through a hole through the upper handle housing  18 . 
         [0035]    Once the shaft of the hex-head screw passes through the hole through the upper handle housing, an outer washer  78  (e.g., a stainless steel washer) is slid over the shaft of the hex-head screw. This outer washer, which may ride in a recess on the top surface of the upper handle housing, reduces friction between the inner knob and the upper handle housing. The shaft of the hex-head screw is next threaded into a threaded insert  80  which is press-fit into an inner knob  82  shown to good advantage in  FIG. 3 . The inner knob comprises a spur gear  84  on a base  86 . The gears or splines on the spur gear of the inner knob are arranged to mesh with internal teeth or splines (see  FIG. 6 ) on the inner surface of the outer knob. 
         [0036]    As shown to good advantage in  FIG. 3 , during assembly of the catheter handle and the steering actuator, two rollers  40  are slid onto roller pins  88  and held in place by a roller retention cap or cover  90 . As also shown to good advantage in  FIG. 3 , the two pull wires  30 ,  32  that are extending from a distal anchor point (not shown) at the distal end of the catheter shaft, are attached (e.g., by the crimps shown in  FIG. 3 ) to fibers that complete the route from the crimps to the anchor point  38  on the steering actuator. In one embodiment, the crimps  34  are implemented using titanium crimp sleeves, although any manner of coupling the pull wires  30 ,  32  to the fibers  36  may be utilized. 
         [0037]    Referring next to  FIGS. 4 and 5 , further details of a representative inner actuator and the various components that it supports will be described.  FIG. 4  is a fragmentary, isometric view of the portion of the catheter handle and steering actuator in dashed circle AA in  FIG. 2 . Starting at the upper right portion of this figure, it is possible to see two crimps (each labeled  34 ) that connect the first and second pull wires  30 ,  32  to the fibers (each labeled  36 ), respectively. Each fiber then extends around a respective roller  40  before passing around a wall section  42 ,  44  and then to an anchor point  38 . 
         [0038]    In this embodiment, each anchor point comprises a pull wire tensioning or tension mechanism (e.g., a pull wire “tuner mechanism” or a pull wire termination) that, in one embodiment, includes a tension adjustment pin  92  (e.g., a “tuning pin”) and a pin block  94 . As shown in  FIGS. 4 and 5 , each tension adjustment pin may be rotated into its respective pin block. The tension adjustment pins and pin blocks may include screw threads. That is, both the tension adjustment pin and the pin block comprising a tensioning mechanism may be threaded, or either the tension adjustment pin or the pin block comprising a tensioning mechanism may be threaded, or neither the tension adjustment pin nor the pin block comprising a tensioning mechanism may be threaded. 
         [0039]    In the embodiment depicted in  FIGS. 4 and 5 , the pin blocks each comprise a slotted pillar. In particular, each pin block comprises a hollow cylinder with a slot or cut through opposing locations of the cylinder wall, the cut also passing through the center of the pillar. As may be seen to good advantage in  FIG. 5 , each tension adjustment pin comprises a fiber channel or hole  96 . Each fiber is connected to the tensioning mechanism by inserting a proximal portion of the fiber into the corresponding hole or channel in the tuner pin, and then rotating the tuner pin in the pin block, which traps the fiber between the outer surface of the tuner pin and the inner surface of the pin block. The slots in the cylindrical walls of the pin blocks allow the walls to flex slightly as the fiber is wound onto a respective tuner pin. This allows the fibers, and thus the pull wires, to be preloaded with a desired tension. This system simplifies manufacturing by allowing for less precise initial trimming of the fibers (or pull wires) since adjustments can be made via the tensioning mechanisms. The tensioning mechanisms allow for easy termination of the fiber ends and permit precise preloading of desired tension on the pull wires. 
         [0040]    As also may be seen to good advantage in  FIG. 4 , the roller retention cap  90  includes a guide wall  98  that extends downwardly (as depicted in  FIG. 4 ) to keep the fibers at a desired trajectory toward the first and second guide wall sections. As may also be seen to good advantage in  FIG. 4 , each roller pin  88  has a cross-sectional area in the shape of a cross, for example, rather than a circle. This cross-sectional shape for the roller pins helps reduce friction between the outer surface of the roller pins and the inner surface of the rollers. It should be noted that each roller may be replaced with a fixed cylinder that does not rotate on a roller pin, or by an arcuate guiding surface configured to guide one of the fibers on the desired trajectory toward its respective wall sections. It should also be kept in mind that each of the pull wires could traverse the entire course from its anchor point at the distal end of the catheter to its anchor point in the handle (e.g., at one of the tensioning mechanisms shown to best advantage in  FIGS. 4 and 5 ). 
         [0041]    As may also be seen in  FIGS. 2-5 , the inner actuator may include a rear wall section  100 . The rear wall section shown in these four figures is an arcuate wall. This wall section may, for example, provide some structural integrity to the inner actuator. 
         [0042]      FIG. 6  is an isometric view showing the underside of a representative outer knob  24 . As may be clearly seen in this figure (and in  FIGS. 1-3 ), the outer surface of the outer knob may comprise ridges  102  to facilitate grasping of the outer knob during use of the catheter comprising a steering actuator. The outer knob also includes on its interior an internal gear  104 , comprising splines or teeth  106  configured to mesh with the splines or teeth on the outer surface of the inner knob  82  shown in  FIG. 3 .  FIG. 6  also clearly depicts two limit posts  108  extending downwardly past a lower surface  110  of the outer knob. These limit posts are designed to ride in travel confinement channels  112  shown to good advantage in  FIG. 3  and permit the outer knob, in this embodiment, to be twisted or turned up to 90 degrees. 
         [0043]    During assembly of the catheter handle housing and steering actuator, the inner knob  82  may be tightened onto the hex-head screw  66  in order to create a desired amount of preloading (internal friction) in the handle. This preloading makes it possible for the deflected catheter to maintain (or nearly maintain) a deflected configuration without the user having to maintain force (or as much force) on the bosses. Once a desired amount of preloading is set, the outer knob is attached over the inner knob with each limit post centered longitudinally and laterally in its respective travel confinement channel. Being able to put the outer knob in multiple positions on the inner knob enables the described calibration of the actuator. 
         [0044]    With the limit posts  108  riding in their travel confinement channels  112 , the device may be ‘locked’ while limiting the locking force that an operator can apply, preventing that locking force from going higher than needed to keep the actuator in place. Without the limit posts, the operator could keep turning the outer knob, possibly inadvertently over-rotating the outer knob and thereby putting excessive tension on the actuator mechanism and pull wires. Another way to implement the “stop” feature is to provide a hole in the outer knob, and then, when the outer knob is in the right place, snap a pin through the hole. 
         [0045]    When the outer knob  24  is turned during use of the catheter, that turns the inner knob  82 , which lifts the hex-head screw  66  without rotating the screw itself. That, in turn, compresses or pinches the inner actuator between the Dekin® washer  72  and the PEEK washer  76 , generating friction to stop the inner actuator from moving, which, for example, holds the distal end of a catheter shaft in a deflected configuration. 
         [0046]      FIG. 7  depicts an alternative embodiment of a catheter handle  10 ′ and steering actuator  12 ′ for deflecting a catheter shaft. This embodiment again includes an upper handle housing  18 ′, a lower handle housing  20 ′, an outer knob  24 ′, and a strain relief  16 . The actuator according to this embodiment is different from the actuator discussed above, and includes an upper actuator  120  and a lower actuator  122 . It also includes a first boss  26 ′ and a second boss  28 ′. 
         [0047]      FIG. 8  is a fragmentary, isometric view of the catheter handle and steering actuator depicted in  FIG. 7 , with the upper handle housing removed and with the upper actuator  120  removed to reveal details about the steering actuator. As oriented in  FIG. 8 , the steering wires enter the handle from the left side of the figure. The distal ends (not shown) of the pull wires would be anchored to a deflectable catheter shaft section at or near a distal end of the catheter. The proximal end of each pull wire, as depicted in  FIG. 8 , is attached to a corresponding fiber  36 ′ via a crimp  34 ′. In all of the disclosed embodiments, alternative techniques could be used to attach each pull wire to its respective fiber, or each pull wire could extend the entire length from its distal anchor point (not shown) to its proximal anchor point. 
         [0048]    The steering actuator depicted in  FIG. 8  is similar to the actuator described above. However, in this embodiment, a single, C-shaped or U-shaped (or flattened-semicircular-shaped or horseshoe-shaped) guide wall  114  is present. The shape of the guide wall  114  may be any shape that enables the fiber/pull wire to be taken up or let out upon manipulation of the actuator (e.g., rotation of the inner actuator in this embodiment), For example, the front wall of the illustrated U-shaped guide wall  114  could be removed in whole or in part, while the side portions of the guide wall  114  are used to further tension or relax their respective pull wires when the actuator is rotated one way or the other. The shape of the guide wall  114  allows the fiber (or pull wire if no fiber is used) to follow a fairly straight path. This helps reduce bending of the fiber (or pull wire). When the actuator is rotated in the handle housing during use of the catheter, the fiber starts wrapping at the outer radius, and not at the flattened sides. Thus, the travel gain is on the outside radius of the guide wall. The outer radius of the guide wall is at the same radial distance as if the guide wall were semicircular. 
         [0049]    In the steering actuator depicted in  FIG. 8 , each of the fibers passes a rotatable roller or fixed roller or curved surface (not visible in  FIG. 8 , but located under the retention cap  90 ′), then passes by the guide wall  114  before angling toward an anchor point comprising an alternative tensioning mechanism  38 ′. In this embodiment, the tensioning mechanisms again comprise a pair of tension adjustment pins  92 ′ mounted in pin blocks  94 ′. In this embodiment, however, each pin block only has a single slot, whereas each pin block depicted in, for example,  FIGS. 4 and 5 , included a pair of slots. The pin blocks again comprise an integral part of, or are mounted on, a rotating lower actuator  122 . Preferably, each tuner pin  92 ′ again includes a fiber hole to facilitate attaching the fiber to the tuner pin prior to “tuning” (i.e., tensioning) the pull wire. 
         [0050]      FIG. 9  is a top view of a catheter handle  10 ″ and steering actuator similar to the catheter handle  10 ′ and steering actuator depicted in  FIGS. 7 and 8 , but shows a slightly different configuration for the outer knob  24 ″ and for the top surface of the upper handle housing  18 ″. In particular, in the configuration depicted in  FIG. 9 , the ridges  102 ′ around the circumference of the outer knob extend further onto the top surface of the outer knob, and the outer surface of the upper handle housing includes a plurality of lateral ridges  116  to enhance the gripability of the handle. 
         [0051]    Looking next at  FIGS. 10-12 , additional aspects of the steering actuator also depicted in  FIGS. 7-9  will be described.  FIG. 10  is a cross-sectional view taken along line  10 - 10  of  FIG. 9  and  FIG. 11  is an enlarged view of the region in dashed circle BB of  FIG. 10 . A coil stop  118  may be seen in  FIG. 10  (see also  FIG. 13 ). In particular, the pull wires may be surrounded by coils (not shown) in at least a portion of the catheter shaft. The proximal end of the coils rests against the distal side of the coil stop, and the pull wires extend from the coil stop proximally into the handle without being surrounded by the coils. 
         [0052]    In the assembled steering actuator, a number of friction points exist, by design, between the steering actuator and the upper and lower handle housings  18 ″,  20 ″. When the hex-head machine screw  66  is pulled upwardly by the inner knob  82  and its threaded insert, this creates an increasing amount of friction between, for example, the upper actuator  120  and the upper handle housing  18 ″ at, for example, the identified friction points  124 ,  126  and between, for example, the lower actuator  122  and the lower handle housing  20 ″ at, for example, the identified friction points  128 ,  130 . As previously discussed, the handle may be preloaded to a desired amount of internal friction (which helps keep the catheter in a deflected state after a user inputs a deflection force) by threading the inner knob onto the hex-head machine screw prior to placing the outer knob onto the inner knob. Once the desired amount of preloading has been achieved, the outer knob is mounted on the inner knob. The user then, as also previously discussed, is able to rotate the outer knob to create sufficient friction between the handle housing and the actuator to temporarily ‘lock’ the distal end of the catheter in a desired deflected configuration. 
         [0053]      FIG. 13  is a fragmentary, isometric view of a portion of the catheter handle and steering mechanism depicted in  FIGS. 7-12 , but with a portion of the upper handle housing removed to reveal components in the distal part of the handle. As may be clearly seen in  FIG. 13 , a separation wall  132  may extend longitudinally from adjacent to the coil stop to a location just distal to the steering actuator. The separation wall, if present, helps isolate the pull wires or their respective fibers to keep them from interfering with each other during operation of the steering actuator. The separation wall can also provide structural integrity to the handle. 
         [0054]      FIG. 14  is a fragmentary, isometric view of a catheter handle  10 ′″ and steering actuator  12 ″ according to another embodiment. In this embodiment, the guide wall  134  is a forward-facing guide wall (i.e., it curves or bows forward) that extends in a semicircle from approximately the nine o&#39;clock position on the left of  FIG. 14 , through the twelve o&#39;clock position, and to the three o&#39;clock position, as oriented in  FIG. 14 . Similar to what is depicted in the figures already described, the pull wires  30 ,  32  enter from the distal end of the handle (not shown in  FIG. 14 ). At the top of  FIG. 14 , a pull wire is shown entering a crimp connector  34 ″, which it will be joined to a fiber  36 ″. The fiber then extends proximally past a roller, around a portion of the semicircular guide wall, and then to a tensioning mechanism similar to one of the tensioning mechanisms described above. For simplicity,  FIG. 14  only depicts a single pull wire connected to a single fiber. If a single pull wire is used in the completed handle in any of the embodiments depicted and described herein, the catheter handle would be a unidirectional handle. Each of the configurations shown and described herein could be configured for bidirectional or unidirectional steering of the catheter shaft. 
         [0055]      FIGS. 15-17  depict yet another alternative configuration for the guide wall  136 . In these figures, the guide wall is rearward facing (i.e., it curves or bows rearward) and comprises a single, continuous arc of approximately 270 degrees, with a forward-facing gap between the ends of the wall. These figures also schematically depict a rotating actuator base, a central screw pillar, two lateral screw pillars, and an outer actuator. Also schematically shown in these figures are two tensioning mechanisms similar to those previously described. In  FIG. 15 , the actuator is shown in a neutral position. In  FIG. 16 , the actuator is shown in a slightly-deflected position. Finally, in  FIG. 17 , the actuator is shown in a fully-deflected configuration. 
         [0056]    Although embodiments of a steering actuator for a deflectable catheter have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this disclosure. All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader&#39;s understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the devices. Joinder references (e.g., affixed, attached, coupled, connected, and the like) are to be construed broadly and can include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relationship to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure can be made without departing from the spirit of the disclosure as defined in the appended claims. 
         [0057]    Any patent, publication, or other disclosure material that is said to be incorporated (in whole or in part) by reference herein is incorporated herein only to the extent that the incorporated materials does not conflict with existing definitions, statements, or other disclosure material expressly set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material expressly set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.