Abstract:
Deflection actuators configured to provide variable mechanical advantage and to optionally maintain a desired state of deflection are disclosed. Each deflection actuator may comprise a plurality of planar components, at least one of which is adapted to move relative to at least one other component. The planar components may comprise a channeled platform and a pivotable base mounted adjacent to the channeled platform. The platform may comprise a slider trough to slidably retain a slider. The base may have a cam arm pivotally connected to it and adapted to push a slider in its trough, whereby pivoting of the pivotable base relative to the channeled platform produces linear motion by the slider in its slider trough. The deflection actuator may also comprise a friction-lock knob, a knob receiver, and a pivot hub to selectably produce friction between various components to hold a catheter shaft in a desired state of deflection.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application No. 61/926,814, filed 13 Jan. 2014, which is hereby incorporated by reference as though fully set forth herein. 
     
    
     BACKGROUND 
       [0002]    a. Field 
         [0003]    The instant disclosure relates to handles and actuators for steerable medical devices. In one particular form, this disclosure relates to a catheter actuator that includes one or more cam arms that provide mechanical advantage when tensioning one or more tension members. 
         [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 the 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 tension member 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 tension member. 
         [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 OF THE DISCLOSURE 
       [0010]    In one embodiment, a deflection actuator comprises (i) a channeled platform adapted to be fixedly mounted to a catheter handle housing, wherein the channeled platform comprises a first slider trough; (ii) a pivotable base mounted adjacent to the channeled platform and adapted to pivot relative to the channeled platform; (iii) a first slider slidably mounted in the first slider trough; and (iv) a first cam arm pivotally connected to the pivotable base and adapted to push the first slider in the first slider trough, whereby pivotable motion of the pivotable base relative to the channeled platform produces linear motion by the first slider in the first slider trough. The deflection actuator may further comprise a pivot hub rotatably mounted in a hole through the channeled platform, wherein the pivot hub comprises a first keyed section keyed to the pivotable base such that the pivot hub and the pivotable base rotate together. 
         [0011]    In another embodiment, a deflection actuator comprises the following: (a) a pivot hub comprising an end surface, an upper keyed surface, an intermediate bearing surface, a lower keyed surface, and a screw-member-receiving hole oriented along a pivot hub longitudinal axis; (b) a cover disk comprising a cover disk central hole mounted on the upper keyed surface of the pivot hub, whereby the pivot hub is adapted to rotate with the cover disk; (c) a pivotable base comprising a pivotable base central hole mounted on the lower keyed surface of the pivot hub, whereby the pivot hub is adapted to rotate with the pivotable base; (d) a channeled platform adapted to be fixedly mounted to a catheter handle housing, the channeled platform comprising (i) a first slider trough and (ii) a channeled platform central hole pivotably mounted on the intermediate bearing surface of the pivot hub, whereby the pivot hub is adapted to freely rotate in the channeled platform central hole; (e) a knob receiver mounted above the end surface of the pivot hub; (f) a friction-lock knob mounted on the knob receiver; (g) a first slider comprising a proximal end and a distal end, the first slider slidably mounted in the first slider trough; and (h) a first cam arm comprising a proximal end and a distal end, wherein the distal end of the first cam arm is pivotally connected to the pivotable base, wherein the proximal end of the first cam arm is adapted to push the distal end of the first slider in the first slider trough, whereby pivotable motion of the pivotable base relative to the channeled platform produces linear movement of the first slider in the first slider trough. The embodiment may include multiple cam arm and multiple sliders, and a tension member anchor may be mounted to each of the sliders. 
         [0012]    In yet another embodiment, a catheter handle comprises a deflection actuator pivotably mounted in a handle housing. The deflection actuator may comprise (a) a channeled platform fixedly mounted in the handle housing, the channeled platform comprising a first planar surface, a second planar surface, a first slider trough, and a second slider trough; (b) a pivotable base rotatably mounted in the handle housing against the first planar surface of the channeled platform, wherein the pivotable base is adapted to pivot relative to the channeled platform; (c) a cover disk rotatably mounted in the handle housing against the second planar surface of the channeled platform; (d) a pivot hub extending through the cover disk, the channeled platform, and the pivotable base; (e) a knob receiver comprising a threaded member mounted along a longitudinally-extending knob receiver pivot axis, wherein the threaded member is also threaded into a blind hole extending along a longitudinally-extending pivot hub pivot axis; (f) a friction-lock knob fixedly mounted to the knob receiver to rotate therewith; and (g) a first thumb boss, a second thumb boss, and a crossmember extending between and connecting the two thumb bosses, wherein the crossmember is affixed to the pivotable base. Further, the pivot hub, in one embodiment, may comprise (i) a first keyed surface keyed to a hole through the pivotable base; (ii) a second keyed surface keyed to a hole through the cover disk; and (iii) a bearing surface mounted in a hole through the channeled platform; (iv). The catheter handle may further comprise a first slider slidably mounted in the first slider trough, a second slider slidably mounted in the second slider trough; a first cam arm pivotally connected to the pivotable base and adapted to push the first slider in the first slider trough, whereby pivotable motion of the pivotable base relative to the channeled platform produces linear movement of the first slider in the first slider trough; and a second cam arm pivotally connected to the pivotable base and adapted to push the second slider in the second slider trough, whereby pivotable motion of the pivotable base relative to the channeled platform produces linear movement of the second slider in the second slider trough. 
         [0013]    The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The foregoing and other aspects, features, details, utilities, and advantages of the present disclosure will be apparent from reading the following description and claims, and from reviewing the accompanying drawings. The description that follows more particularly exemplifies one or more illustrative embodiments. In several places throughout this disclosure, guidance is provided through examples, which can be used in various combinations. The recited examples are representative and should not be interpreted as exclusive or exhaustive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is an isometric view of the top and right or starboard side of a catheter handle having a deflection actuator according to one embodiment of the present disclosure, with various parts of the catheter removed for clarity. 
           [0015]      FIG. 2  is an isometric view of the catheter handle depicted in  FIG. 1 , with the upper handle housing and select other components removed to reveal the deflection actuator in a slightly-actuated configuration. 
           [0016]      FIG. 3  is a fragmentary, isometric view of the catheter handle depicted in  FIGS. 1 and 2 , with the deflection actuator in the same, slightly-actuated configuration shown in  FIGS. 1 and 2 , but with additional components removed to reveal certain additional aspects of the deflection actuator. 
           [0017]      FIG. 4  is similar to  FIG. 3 , but depicts the deflection actuator in a near-fully-actuated configuration. 
           [0018]      FIG. 5  is most similar to  FIG. 3 , but shows the friction-lock knob removed, and both sliders and tension member anchors in place. 
           [0019]      FIG. 6  is an enlarged, fragmentary, isometric view of the deflection actuator depicted in  FIG. 5  in a slightly different orientation making clear, for example, the clearance between the tension member anchors. 
           [0020]      FIG. 7  is a top or plan view of the deflection actuator mounted in the lower handle housing with the friction-lock knob and the knob receiver removed and with the deflection actuator fully actuated in a first direction. 
           [0021]      FIG. 8  is an enlarged, fragmentary side view of the proximal end of a cam arm pushing on the distal end of a slider, revealing a slider ledge or overhang that accommodates the roller that is rotatably mounted below the lower surface of the cam arm. 
           [0022]      FIG. 9  is an isometric view of the deflection actuator mounted in the lower handle housing and in the orientation also depicted in  FIG. 7 . 
           [0023]      FIG. 10  is an enlarged, fragmentary, isometric view of the deflection actuator in the configuration also shown in  FIGS. 7 and 9 , but with the sliders removed. 
           [0024]      FIG. 11  is an enlarged view showing the underside of the friction-lock knob. 
           [0025]      FIG. 12  is an enlarged, fragmentary view of a pivot hub. 
           [0026]      FIG. 13  is a fragmentary, isometric, cross-sectional view taken in the direction of line  13 - 13  of  FIG. 1  with some components removed, revealing the inner workings of the friction lock. 
           [0027]      FIG. 14  is similar to  FIG. 13 , but depicts the actuator removed from both the upper handle housing and the lower handle housing. 
           [0028]      FIG. 15  is a fragmentary view taken in the direction of line  15 - 15  of  FIG. 2 , depicting various components of the deflection actuator according to an embodiment. 
           [0029]      FIG. 16  is a greatly enlarged, fragmentary, isometric view of select components of a deflection actuator in roughly the same configuration shown in  FIG. 4 . 
           [0030]      FIGS. 17-19  schematically depict components of a deflection actuator moving from a neutral position shown in  FIG. 17  to a fully-actuated configuration shown in  FIG. 19 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0031]      FIG. 1  is an isometric view of a catheter handle  10  that includes a pivotable deflection actuator  12  (shown to better advantage in  FIG. 2 ) according to an embodiment of the present invention. For simplicity,  FIG. 1  does not depict a full catheter, which would include a catheter shaft, electrical connections, and other components that are not shown in this figure. In this embodiment, the catheter handle  10  comprises an upper handle housing  14  and a lower handle housing  16 , each of which extends from a proximal end  18  of the catheter handle  10  to a distal end  20  of the catheter handle  10 . A friction-lock knob  22  comprising a plurality of knob knurls  24  is rotatably mounted above the upper handle housing  14 . As will be discussed further below, the friction-lock knob, in this embodiment, includes a pair of knob limit pins  26 ,  28  (shown in, for example,  FIGS. 11 and 15 ) that extend into or through arcuate slots (not shown, but discussed further below with regard to  FIG. 11 ) through the upper handle housing  14  in order to limit how far a user may rotate the friction-lock knob  22  clockwise or counterclockwise. 
         [0032]    The deflection actuator  12  also includes a first thumb boss  30 , a second thumb boss  32 , and a crossmember  34  extending between and connecting the two thumb bosses. Each thumb boss may include a plurality of grooves or a plurality of raised ridges or knob knurls  36 , as shown in  FIG. 1 , to facilitate positive interaction between a user&#39;s hands and the bosses. In  FIG. 1 , the deflection actuator  12  is shown in a neutral or nearly neutral orientation, where the first and second thumb bosses symmetrically straddle a longitudinal axis  38  of the catheter handle  10 . 
         [0033]      FIG. 2  is similar to  FIG. 1  and is an isometric view of the deflection actuator  12  mounted in the lower handle housing  16 . In this figure, the upper handle housing  14  has been removed to reveal a number of components of the deflection actuator  12 . For example, the actuator according to this embodiment may include a cover disk  40  that may be located under the upper handle housing  14  in the fully-assembled handle. A first cam arm  42  may be seen in  FIG. 2 . In particular, the first cam arm  42  is shown with its proximal end (also known as an arcuate pushing end  108 , which is labeled in  FIG. 6 ) pressing against a distal end (also known as a slider pushed end  110 , which is labeled in  FIG. 6 ) of a first slider  44  that is longitudinally slidably mounted in a first slider trough or slider guide channel  46 . The first slider trough and a second slider trough  48  are formed in a channeled platform  50  comprising part of the deflection actuator  12 . For instance, the first slider trough  46  is formed by a starboard wall  52 , a central wall  54 , and a lower wall  56 . Similarly, the second slider trough  48  is formed by a port wall  58 , the central wall  54 , and the lower wall  56 . In  FIG. 2 , no second slider is present, but a second slider  60  is shown in, for example,  FIGS. 5 and 6  (a second slider may be present if bidirectional deflection is desired). 
         [0034]    A first tension member clamp or anchor  62  is shown affixed to a proximal end of the first slider  44 . The first tension member anchor includes a screw hole  64  to accommodate a screw or other fixation member (not shown). As will be described further below, when a screw is tightened in the screw hole  64 , the first tension member anchor  62  pinches or traps a first tension member (or pullwire or puller wire)  66  against a portion of the first slider  44  (see also  FIG. 15 ). Then, when the deflection actuator  12  is actuated to move the first slider  44 , the first slider also simultaneously moves or pulls the first tension member  66 . Each tension member may be metallic (e.g., stainless steel) or non-metallic (e.g., Kevlar or some other natural or manmade material). It is also possible to see a tension member separation wall  68  in  FIG. 2 . In this embodiment, the tension member separation wall  68  comprises part of the lower handle housing  16 . 
         [0035]      FIG. 3  is a view similar to  FIG. 2 , but with the cover disk  40  removed to reveal a second cam arm  70 . With the cover disk removed, it is also possible to see that the distal end of the first cam arm is pivotably mounted to a first pin block  72  by a first pivot pin  74 . Similarly, a distal end of the second cam arm  70  is pivotably attached to a second pin block  76  by a second pivot pin  78 . The first pin block  72  is attached to (or comprises an integral part of) a pivotable base  80  that rotates relative to the channeled platform  50 . In particular, the first pin block  72  rides in a first pin block channel  82  (labeled in  FIG. 4 ) formed in the channeled platform  50 , and the second pin block  72  rides in a second pin block channel  82  (labeled in  FIG. 4 ) that is also formed in the channeled platform  50 . As will be discussed further below, the proximal end of each cam arm  42 ,  70  may have a roller  86  rotatably mounted to it. In  FIG. 3 , a second roller  86  is visible. These rollers  86  which may be present on the proximal ends of the cam arms are described further below while discussing figures in which these rollers are more clearly visible (see, for example, a discussion of  FIGS. 8 ,  10 , and  16 ). 
         [0036]      FIG. 4  is similar to  FIG. 3 , but shows the deflection actuator  12  in a more fully deflected configuration. In particular, comparing  FIG. 4  to  FIG. 3 , it is possible to see that the first thumb boss  30  is in a more proximal position in  FIG. 4  than it is in  FIG. 3  (the deflection actuator has been rotated slightly clockwise in  FIG. 4  relative to its position in  FIG. 3 ). This in turn causes the first cam arm  42  to be shifted proximally compared to its position in  FIG. 3 , which would pull the first tension member  66  closer to the proximal end  18  of the lower handle housing  16 . 
         [0037]    In  FIG. 5 , the deflection actuator  12  has returned to a near-neutral configuration, similar to what is shown in  FIG. 3 . In  FIG. 5 , however, the friction-lock knob  22  has been removed, revealing a knob receiver  88 . The knob receiver comprises a knob support ring  90  and a splined, knob-mounting shaft  92 . The knob support ring is mounted above a lower body  94  of the knob receiver  88 . In this figure, it is also possible to see slightly more of a pivot hub  96  on which the knob receiver  88  is mounted. In particular, in  FIG. 5 , it is possible to see a upper keyed section  98  and an intermediate bearing surface  100 , both comprising part of the pivot hub  96 .  FIG. 12  is an isometric and enlarged view of this pivot hub  96 , which will be described further below in connection with the discussion of  FIG. 12 . Referring back to  FIG. 5 , with the upper handle housing  14 , the cover disk  40 , and the friction-lock knob  22  removed, it is also possible to see a first tension member port  102  and a second tension member port  104  formed through the distal portion of the channeled platform  50 .  FIG. 5  also shows both a first slider  44  mounted in a first slider trough  46  and a second slider  60  mounted in a second slider trough  48 . These troughs  46 ,  48  are shown to best advantage in  FIG. 10 . The first tension member anchor  62  is shown mounted on the proximal end of the first slider  44 , and a second tension member anchor  106  as shown mounted on the proximal end of the second slider  60 . 
         [0038]      FIG. 6  is an enlarged, fragmentary, isometric view of the actuator  12  in the configuration also depicted in  FIG. 5 . However, the viewing angle selected for  FIG. 6  better shows the clearance between the first tension member anchor  62  and the second tension member anchor  106 , which allows the tension member anchors to move past each other as the deflection actuator is actuated. As shown to good advantage in  FIG. 6 , the proximal end of the first cam arm  42  includes a first arcuate pushing end  108  adapted to push against a first slider pushed end  110 . Similarly the proximal end of the second cam arm  70  also includes a second arcuate pushing end  112  adapted to push against a second slider push end  114 .  FIG. 6  also clearly shows a first stop wall  116  and a second stop wall  118 , both comprising part of the channeled platform  50 . These stop walls may be used to help prevent possible over rotation of the deflection actuator. In particular, the first stop wall  116  may, for example, impact a distal side  120  of the first cam arm  42  when the deflection actuator is fully actuated in a first direction (for example, counterclockwise in  FIG. 6 ); and the second stop wall  118  may impact a distal side  122  of the second cam arm  70  when the deflection actuator  12  is fully actuated in the opposite direction (for example, clockwise in  FIG. 6 ). 
         [0039]      FIG. 7  is a top or plan view, depicting components of the deflection actuator  12  mounted in the lower handle housing  16 , and with the deflection actuator fully actuated in a first direction. In this configuration, the first cam arm  42  is displaced as far as possible toward the proximal end  18  of the lower handle housing  16 . Simultaneously, the second cam arm  70  is displaced as far as possible, forward toward the distal end  20  of the lower handle housing. The first roller  86  and the second roller  86  are both visible in this figure. As will be discussed further below, these rollers may ride against the walls comprising one of the slider troughs  46 ,  48  while the associated cam arms  42 ,  70  press against their respective slider  44 ,  60 . 
         [0040]      FIG. 8 , which is an enlarged, fragmentary view of a proximal portion of the first cam arm  42  and the distal portion of the first slider  44 , shows the first roller  86  mounted on a roller pin  124  projecting downwardly from a lower surface of the first cam arm  42 . As shown in  FIG. 8 , the distal end of the first slider may include a first slider ledge or overhang  126  to accommodate the roller  86 . 
         [0041]      FIG. 9  is an isometric view of the components depicted in  FIG. 7  looking downward and at the left or port side of the lower handle housing  16  and various components of the deflection actuator  12 . In this figure, the first cam arm  42  is shown riding in the first guide trough  46  between the central wall  54  and the starboard wall  52 . The second slider  60  (not shown in  FIG. 9 ) would similarly ride in the second guide trough  48  between the port wall  58  and the central wall  54 . As discussed above in connection with  FIG. 7 , this orientation of the deflection actuator places the first cam arm  42  in its maximum proximal position, and the second cam arm  70  in its maximum distal position. 
         [0042]      FIG. 10  is an enlarged, fragmentary, isometric view of the deflection actuator components in the state of deflection that is also depicted in  FIGS. 7 and 9 . In  FIG. 10 , however, it is easier to see the first roller  86  riding in the first guide trough  46  between the starboard wall  52  and the central wall  54 ; and the second roller  86  riding in the second guide trough  48  between the port wall  58  and the central wall  54 .  FIG. 10  also clearly shows the distal side  122  of the second cam arm  70  impacting the second stop wall  118  when the actuator is in this fully-deflected configuration (i.e., rotated fully clockwise as depicted in  FIG. 10 ). As the pivotable base  80  is rotated fully clockwise below the channeled platform  50  by the user putting a proximal force on the first thumb boss  30  and/or a distal force on the second thumb boss  32 , the distal end of the first cam arm  42  travels clockwise in an arcuate path to the location depicted in  FIG. 10 , while the distal end of the second cam arm  70  travels distally in an arcuate path while the second pin block  76  (shown in, for example,  FIGS. 3 and 5 ) rides in the second pin block channel  84  adjacent to or against an arcuate surface of the channeled platform  50 . As also clearly shown in  FIG. 10 , the rollers  86  project more rearwardly or proximally than the proximal ends of each cam arm. This relationship is also shown in the fragmentary view depicted in  FIG. 8 . 
         [0043]      FIG. 11  is an enlarged, isometric view looking toward a lower surface  128  of one possible embodiment of the friction-lock knob  22 . As previously mentioned, this knob may comprise a plurality of knob knurls  24  to make it easier for an electrophysiologist, physician, or other user to rotate the friction-lock knob  22 , even if wearing a surgical glove. As also mentioned above, the knob may comprise a pair of knob limit pins  26 ,  28  protruding from its lower surface  128 . These limit pins are configured to ride in arcuate or C-shaped channels (not shown) formed into or through the upper handle housing  44 . Similar C-shaped channels may be seen in, for example, co-owned U.S. provisional patent application No. 61/820,613, filed on 7 May 2013, and titled, “Handle for Deflectable Catheter,” which is hereby incorporated by reference as though fully set forth herein. The C-shaped channels that would be formed in or through the upper handle housing would each accommodate one of these knob limit pins  26 ,  28 . When the friction-lock knob  22  is rotated to the maximum extent in either direction, one or both of the knob limit pins may impact a longitudinal end of one of these C-shaped channels. 
         [0044]    Continuing to look at  FIG. 11 , in the depicted embodiment of the friction-lock knob  22 , an annular seat  130  is formed in the underside of the knob. This annular seat is configured to receive the knob support ring  90  comprising part of the knob receiver  88 , which is shown in, for example,  FIGS. 5 ,  6 ,  13 , and  14 . A splined pocket  132  may also be formed in the underside of the friction-lock knob. This splined pocket  132  is configured to accommodate the splined, knob-mounting shaft  92  that is visible in, for example,  FIGS. 5 and 6 . The splined pattern depicted in  FIGS. 5 and 6  on the splined, knob-mounting shaft  92  is slightly different from the splined pattern depicted in  FIG. 11  in the splined pocket  132 . A variety of different splined patterns may be used as long as the splined pocket is keyed to the splined, knob-mounting shaft such that rotation of the knob  22  rotates the splined receiver  88 . 
         [0045]      FIG. 12  depicts an enlarged, isometric view of one embodiment of the pivot hub  96 . In this embodiment, the pivot hub includes an upper keyed section  98  extending longitudinally downward from the perimeter of a top or end surface  134  of the pivot hub. The outer surface of the pivot hub  96  may also define an intermediate bearing surface  100  and a lower keyed section  136 . The pivot hub depicted in  FIG. 12  also includes an annular ledge or ‘lifting ledge’  138  positioned above a lower disk  140 . Finally, in this embodiment, the pivot hub  96  may also include a pivot shaft  142 . Each of these parts of the pivot hub will be described further below in connection with the description of  FIGS. 13 and 14 . 
         [0046]      FIG. 13  is an enlarged, fragmentary, cross-sectional view taken along line  13 - 13  in  FIG. 1 , effectively cutting the catheter handle  10  and deflection actuator  12  in half laterally. In this figure, some components have been removed for clarity and easier comprehension. For example, when the handle is fully assembled, the pivotable base  80  would be connected to the crossmember  34  such that when a user displaces the thumb bosses  30 ,  32 , the crossmember  34  would, in turn, rotate the pivotable base  80  since screws or pins would attach the crossmember to the pivotable base. Screws (not shown) could, for example, be mounted in the depicted channels  144  through the pivotable base  80  and threaded into blind holes  146  formed in the crossmember  34 . Such mounting screws have not been shown in  FIGS. 13 and 14  for clarity. 
         [0047]    Working from top to bottom in  FIG. 13 , it is possible to see the friction-lock knob  22  mounted on top of the knob receiver  88 . In particular, the knob-mounting shaft  92  is mounted in the splined pocket  132  (labeled in, for example,  FIGS. 11 and 14 ) comprising part of the friction-lock knob  22 . The knob may be, for example, press-fit or adhered onto the knob receiver  88  during assembly. As shown in this figure, once the friction-lock knob is assembled with the knob receiver, the knob support ring  90  rides in the annular seat  130  (labeled in  FIG. 11 ). The lower surface  128  of the friction-lock knob and the lower surface of the knob support ring  90  are shown riding on the upper surface of the upper handle housing  14  in  FIG. 13 . Also, the lower body  94  of the knob receiver  88  is shown projecting through a hole through the upper handle housing  14 , and a lower surface (i.e., a downwardly-pressing surface)  146  of the knob receiver  88  is shown pivotably riding on the top surface of the cover disk  40 . 
         [0048]    The pivot hub  96  is also visible in  FIG. 13  in cross section. As shown, the top surface  134  (labeled in  FIG. 12 ) of the pivot hub is displaced/offset from the knob receiver for reasons that are apparent from the below discussion. A threaded member (not shown) would be mounted in a central hole  148  in the knob receiver  88  and thread into a central hole (or blind hole)  150  in the pivot hub  96 . Since, as previously discussed, rotation of the friction-lock knob  22  rotates the knob receiver  88 , this would, in turn, also rotate the threaded member fixedly mounted in the hole  148  in the knob receiver, thereby threading the threaded member into the blind hole  150  of the pivot hub  96 . As already noted, the downwardly-pressing surface  146  of the knob receiver presses on an upper surface of the cover disk  40 . The cover disk, in turn, rides on an upper surface of the channeled platform  50 . The channeled platform, in turn, rides on an upper surface of the pivotable base  80 . In the embodiment depicted in  FIG. 13 , the pivotable base includes portions that project through the slots in the lower handle housing  16 . The upper keyed section  98  of the pivot hub  96  is keyed to the hole through the center of the cover disk  40 . Thus, the pivot hub does not rotate relative to the cover disk. Similarly, the lower keyed section  136  of the pivot hub  96  is keyed to the pivotable base  80 . As a result, the pivot hub  96 , the cover disk  40 , the pivotable base  80 , and the cross member  34  and thumb bosses  30 ,  32 , all rotate together. 
         [0049]    During operation of the deflection actuator  12 , the user would rotate the deflection actuator by applying pressure to one or both of the thumb bosses  30 ,  32 . Once the actuator was rotated a desired amount, the user could rotate the friction-lock knob  22  to hold the actuator in that rotated configuration, which would maintain, for example, a desired deflection of the distal end of the catheter shaft (not shown). For example, when the friction-lock knob  22  is rotated clockwise, that would rotate the knob receiver clockwise, which, in turn, would rotate the threaded member (not shown) that is fixedly mounted in the central hole  148  of the knob receiver  88  clockwise. Rotation of the threaded member in the blind hole  150  in the center of the pivot hub  96  would pull or lift the pivot hub upwardly toward the knob receiver  88  and the friction-lock knob  22 . As the pivot hub is lifted, the lifting ledge  138  is lifted upwardly against the lower surface of the pivotable base  80 , which, in turn, would lift upwardly on the lower surface of the channeled platform  50 , which, in turn, would lift upwardly on the lower surface of the cover disk  40 . As a result, the cover disk  40 , the channeled platform  50 , and the pivotable base  80  get pinched or clamped together between the upwardly-moving lifting ledge  138  (which lifts upwardly on the lower surface of the pivotable base  80 ) and the downwardly-pressing surface  146  of the knob receiver  80  (which presses downwardly on the upper surface of the cover disk  40 ). Once sufficient friction is achieved, the deflection actuator is held in a desired state of deflection, even if the physician or other user completely removes his or her hands from the catheter. Similarly, when the physician or other user applies rotational pressure to the thumb bosses  30 ,  32 , that rotates the pivotable base  80 , which, as noted above, is keyed to the lower keyed section  136  of the pivot hub  96 . 
         [0050]      FIG. 14  is similar to  FIG. 13 . However, in  FIG. 14 , both the upper handle housing  14  and the lower handle housing  16  have been removed. This figure, therefore, shows most components of an embodiment of the deflection actuator  12 , separated from the handle housings. As clearly shown in this figure when considered in view of  FIG. 12 , the intermediate bearing surface  100  of the pivot hub  96  slippingly rides in a hole through the channeled platform  50 . Thus, the pivot hub is able to rotate relative to the channeled platform. In contrast, and as also visible in  FIG. 14  and as discussed above in connection with  FIG. 13 , the cover disk  40  rides on the upper keyed section  98  of the pivot hub  96 . Thus, the cover disk  40  rotates with the pivot hub  96 . Similarly, the pivotable base  80  is keyed to the lower keyed section  136  of the pivot hub  96  and, therefore, also pivots with the pivot hub. As a result, and as already noted above, when the thumb bosses  30 ,  32  and crossmember  34  are rotated in either direction by the user of the catheter, the pivotable base  80 , the pivot hub  96 , and the cover disk  40  rotate together. This, in turn, results in the knob receiver  88  and knob  22  also possibly rotating with the cover disk, the pivot hub, the pivotable base, and the crossmember and thumb bosses. As a result, the amount of ‘locking friction’ present in the friction lock may not change while the physician or other user manipulates the distal end of a catheter by actuating the deflection actuator via varying pressure on one or both of the thumb bosses. If the knob receiver  88  and the knob  22  do not rotate when the thumb bosses  30 ,  32  and crossmember  34  are pivoted (for example, if there is insufficient friction between the top surface of the cover disk  40  and the downwardly-pressing surface  146 ), the blind hole  50  can merely thread onto (and off of) the threaded member (not shown) fixedly mounted in the hole  148  through the knob receiver  88 . 
         [0051]    Once the desired amount of catheter deflection is achieved, the user, while holding the thumb bosses  30 ,  32  and crossmember  34  in place, rotates the friction-lock knob  22 . This rotation of the friction-lock knob, as previously discussed, turns the knob receiver  88  and the threaded member mounted in the hole  148  through the knob receiver. As that threaded member threads into the blind hole  150  in the pivot hub  96 , the pivot hub is lifted toward the friction-lock knob or pushed away from the friction-lock knob, depending upon which direction the user rotates the friction-lock knob. If the user is attempting to increase the friction, the cover disk  40 , the channeled platform  50 , and the pivotable disk  80  are pinched or clamped together until the distal end of the catheter shaft is held in the desired state of deflection. When the physician is ready to change the deflection of the catheter shaft, the friction-lock knob is rotated in the opposite direction, thereby relieving the friction between various components comprising the deflection actuator  12 . 
         [0052]      FIG. 15  is an enlarged, fragmentary view looking in the direction of line  15 - 15  in  FIG. 2 . At the top of  FIG. 15 , a portion of the friction-lock knob  22  may be seen. At least a portion of the two knob limit pins  26 ,  28  that are fully visible in  FIG. 11  may be seen in  FIG. 15  projecting downwardly from the lower surface  128  of the friction-lock knob. Since, in this figure, the knob is mounted on the knob receiver, it is also possible to see the lower body  94  of the knob receiver projecting upwardly toward the lower surface  128  of friction-lock knob  22  in  FIG. 15 . Moving further downward in  FIG. 15 , it is also possible to see the cover disc resting on top of the port wall  58 , the central wall  54 , and the starboard wall  52 , which comprise part of the channeled platform  50 . The second cam arm  70  is visible in the middle of the left-hand side of  FIG. 15 . Between the port wall  58  and the central wall  54  comprising part of the second slider trough  48 , it is possible to see a proximal end of the second cam arm  70  and a short section of the roller pin  124  projecting downwardly from the lower surface of the second cam arm. The second roller  86  is mounted on this second roller pin so as to roll between the port wall and the central wall. A portion of the first cam arm  42  is also visible. 
         [0053]    Toward the center of  FIG. 15  it is possible to see the first tension member anchor  62  mounted on the first slider  44 . As clearly shown in this figure, in this embodiment, there are longitudinally-extending tension member notches  152  formed along the lower inboard and outboard longitudinal edges of the first slider  44 . Only the inboard tension member notch is labeled in  FIG. 15  since the first tension member  66  is riding in the outboard tension member notch in this figure. Similar notches would be formed on the second slider  60  (not shown in this figure). In  FIG. 15 , the lower right-hand notch has the first tension member  66  riding in it. When the first tension member anchor  62  is attached to the first slider  44 , the first tension member gets pinched between the first tension member anchor and the tension member notch so that, when the first slider moves longitudinally in the catheter housing (e.g., parallel or substantially parallel to longitudinal axis  38  shown in  FIG. 1 ), the first tension member anchor ensures that longitudinal forces on the first slider get transferred to the first tension member. In  FIG. 15 , the pivotable base  80 , as shown below the channeled platform  50 , includes a pair of pin or screw towers defining screw channels  144  and projecting downwardly from a lower surface of the pivotable base  80 . These towers are configured to project or extend through the lower handle housing  16  and are configured to accommodate the pins or screws that mount the pivotable base  80  to the crossmember  34  as discussed above. Finally, the lower disc  140  and pivot shaft  142  of the pivot hub  96  may also be seen in the bottom central portion of  FIG. 15 . 
         [0054]      FIG. 16  is an enlarged, fragmentary, isometric view of an upper, central portion of the deflection actuator. In this figure, the deflection actuator is in a position that is similar to the position shown in  FIG. 4 . The lower body  94  of the knob receiver  88  is shown at the top center portion of  FIG. 16 . It is also possible to see the upper keyed section  98  and the bearing surface  100  of the pivot hub  96 . The bearing surface is shown passing through a central hole  154  through the channeled platform  50 . A portion of the second cam arm  70  is shown with its distal side  122  against the second stop wall  118  of the channeled platform  50 . The second roller  86  is pivotably mounted to the proximal end of the second cam arm  70 , and is shown rotatably riding in the second slider trough  48 . A fragment of the second pin block channel  84  is visible in the upper left portion of  FIG. 16 . The first cam arm  42  is shown in its most proximal position. The first arcuate pushing end  108  of the first cam arm  42  is shown pushing against the first slider pushed end  110 , near the lower left-hand corner of  FIG. 16 . The proximal side  156  of the first cam arm  42  is depicted nearly contacting a distal portion of the starboard wall  52 . The distal end of the first cam arm is shown pivotably mounted on a first pivot pin  74  to the first pin block  72 . Near the middle of the right-hand portion of  FIG. 16 , a fragment of the first pin block channel  82  may be seen. 
         [0055]    Referring next to  FIGS. 17-19 , the mechanical advantage achieved by this embodiment of the deflection actuator is described next. For easier comprehension, each of these three figures schematically depicts only a limited number of the components comprising the deflection actuator  12 .  FIG. 17  depicts the actuator in a neutral configuration. In this configuration or state of catheter shaft deflection, the various components of the deflection actuator are symmetrically distributed on either side of the catheter handle&#39;s longitudinal axis  38 . For example, the first and second thumb bosses  30 ,  32  are symmetrically positioned across from each other, one in the 3 o&#39;clock position and the other in the 9 o&#39;clock position in this figure. 
         [0056]    The first cam arm  42  and the second cam arm  70  are both shown in each of  FIGS. 17-19 . Also shown in each of these figures is a first line  158  extending from the axis of rotation of the deflection actuator through the axis of rotation of the first pivot pin  74 . Similarly, a second line  160  is shown extending between the axis of rotation of the first pivot pin  76  and the axis of rotation of the roller pin  124  at the proximal end of the first cam arm. Angle α is defined between the first line  158  and the second line  160 . Comparing  FIG. 18  to  FIG. 17 , the actuator in  FIG. 18  has been rotated slightly clockwise from its position shown in  FIG. 17 . This clockwise rotation of the actuator drives the first pivot pin  74  in an arcuate path defined by the first pin block channel  82  (see also, for example,  FIG. 4 ). As the first cam arm  42  is driven proximally by this clockwise rotation of the actuator, the angle α is increasing. 
         [0057]    Looking now at  FIG. 19 , the actuator has been further rotated clockwise to a fully-actuated configuration. In this configuration, the first slider  40  has been driven or pushed proximally to its maximum amount, putting the maximum amount of proximal tension in the first tension member  66 . With the actuator in this configuration, the distal end of the catheter would be deflected the maximum amount to a first side. 
         [0058]    Continuing to look at  FIG. 17-19 , as the actuator moves from the neutral configuration depicted in  FIG. 17 , through the partially-actuated configuration depicted in  FIG. 18 , and into the fully-actuated configuration depicted in  FIG. 19 , the distal end of the catheter shaft (not shown) is being progressively deflected to a greater extent. Thus, the tension in the tension member  66  is increasing from the configuration shown in  FIG. 17  to the configuration shown in  FIG. 18 , and then to the configuration shown in  FIG. 19 . As may be seen, however, by looking at  FIG. 17-19 , as the tension in the tension member increases, so does the mechanical advantage provided by the deflection actuator. As a result, the thumb force felt by the user remains manageable and tailorable to a user&#39;s preference. By changing, for example, the size, shape, or diameter of the pivotable base  80 , the length and shape of the cam arms  42 ,  70 , and the location of each cam arm pivot pin  74 ,  78 , it is possible to control and tailor the force profile experienced by a user of the deflection actuator as the tension in the tension members increases or decreases during use of the catheter. 
         [0059]    Embodiments are described herein of various apparatuses, systems, and/or methods. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the embodiments may be practiced without such specific details. In other instances, well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described in the specification. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of all embodiments. 
         [0060]    Reference throughout the specification to “various embodiments,” “some embodiments,” “one embodiment,” or “an embodiment,” or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment(s) is included in at least one embodiment. Thus, appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” or “in an embodiment,” or the like, in places throughout the specification, are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features, structures, or characteristics of one or more other embodiments without limitation, provide that such combination is not illogical or non-functional. 
         [0061]    It will be appreciated that the terms “proximal” and “distal” may be used throughout the specification with reference to a clinician manipulating one end of an instrument used to treat a patient. The term “proximal” refers to the portion of the instrument closest to the clinician and the term “distal” refers to the portion located furthest from the clinician. It will be further appreciated that for conciseness and clarity, spatial or directional terms such as “vertical,” “horizontal,” “up,” “down,” “clockwise,” and “counterclockwise” may be used herein with respect to the illustrated embodiments. However, medical instruments may be used in many orientations and positions, and these terms are not intended to be limiting and absolute. 
         [0062]    Joinder references (e.g., affixed, attached, coupled, connected, and the like) are to be construed broadly and may 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 relation to each other. As used herein, joinder references may also include two components that are molded as a single or unitary piece. Changes in detail or structure may be made without departing from the spirit of the disclosure as defined in the appended claims.