Abstract:
A catheter includes a handle that advantageously limits the amount of torque that can be imparted to the body of the catheter. This advantageously reduces the likelihood of catheter failure, damage to tissue, or damage to medical devices introduced into the vasculature via the catheter. The catheter handle includes a grip portion that the practitioner manipulates in order to impart a torque and a torque transmitting portion operably coupled thereto that transmits the torque to the catheter body. A torque limiting mechanism decouples the torque transmitting portion from the grip portion, the body, and/or any pull wires when the torque imparted to the grip portion exceeds a torque threshold, thereby preventing excessive torques from being transmitted to the catheter body and/or pull wires. A practitioner may be able to adjust the torque threshold and may be able to disable the torque limiting mechanism.

Description:
BACKGROUND OF THE INVENTION 
     a. Field of the Invention 
     The instant disclosure relates generally to catheters for use in the human body. More specifically, the disclosure relates to a catheter handle that reduces the risk of the failure of such catheters when subjected to torques. 
     b. Background Art 
     Catheters are used for an ever growing number of medical procedures. To name just a few examples, catheters are used for diagnostic, therapeutic, and ablative procedures. Typically, the physician manipulates the catheter through the patient&#39;s vasculature to the intended site, such as a site within the patient&#39;s heart. The catheter typically carries one or more electrodes or other diagnostic or therapeutic devices, which can be used for ablation, diagnosis, cardiac mapping, or the like. 
     Since the path a catheter must navigate within a patient is often long and tortuous, steering forces must be transmitted over relatively great distances. It is known, however, to utilize one or more pull wires, which are typically offset from the central longitudinal axis of the catheter and which can be attached to one or more pull rings proximate the distal end of the catheter shaft, to manipulate the distal end of the catheter. Often, these pull wires are embedded into the wall of the catheter (as opposed to, for example, routed through a lumen within the interior of the catheter). 
     It is also desirable for the catheter to transmit a torque applied at the proximal end to the distal end. It has been discovered, however, that the amount of torque that can be applied to a catheter is limited, particularly where the pull wires are embedded in the catheter wall. For example, if the catheter shaft has a strong bend in it and is also deflected (e.g., one or more of the embedded pull wires is under tension), it will be difficult to impart a torque to the catheter shaft. If an operator applies additional torque to the catheter handle in an effort to overcome this “lockup” in the shaft, there is a risk of catheter failure. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore an object of the present disclosure to provide a catheter handle that limits the amount of torque that can be applied to the catheter shaft or body. 
     It is another object of the present disclosure to provide a catheter handle that has an adjustable threshold for the amount of torque that can be applied to the catheter shaft or body. 
     According to a first aspect of the present disclosure, a catheter includes: a catheter body having a proximal end; and a handle coupled to the proximal end of the catheter body such that a torque imparted to the handle can be transmitted to the catheter body. The handle includes: a grip portion adapted to be gripped in order to impart a torque; a torque transmitting portion operably coupled to the grip portion in order to transmit the torque imparted to the grip portion to the catheter body; and a torque limiting mechanism operable to decouple the torque transmitting portion and the grip portion when the torque imparted to the grip portion exceeds a torque threshold, such that torques in excess of the torque threshold are not transmitted to the catheter body. 
     In some embodiments, the torque limiting mechanism includes: a first torque transfer mating structure on the grip portion; and a second torque transfer mating structure that is complementary to the first torque transfer mating structure on the torque transmitting portion. When the torque imparted to the grip portion is less than the torque threshold, the first and second torque transfer mating structures remain engaged such that the torque imparted is transmitted to the catheter body. Conversely, when the torque imparted to the grip portion exceeds the torque threshold, the first and second torque transfer mating structures disengage such that the grip portion rotates relative to the torque transmitting portion, thereby preventing the torque imparted from being transmitted to the catheter body. The first and second torque transfer mating structures can be complementary ridged surfaces. 
     It is contemplated that the grip portion can include a longitudinally-extending bore, such that the torque transmitting portion can be disposed substantially concentrically with the grip portion within the longitudinally-extending bore thereof. 
     Optionally, the handle also includes a torque threshold adjustment structure. For example, a chuck, such as a collet positioned around the grip portion of the handle, can be provided to allow a practitioner to adjust the torque threshold. 
     It is contemplated that the torque limiting mechanism can be disengaged by the practitioner such that all torques imparted to the grip portion are transmitted to the catheter body. For example, the torque limiting mechanism can be disengaged by sliding the grip portion relative to the torque transmitting portion. 
     In another aspect of the disclosure, a catheter includes: a catheter body having a proximal end; and a handle coupled to the proximal end of the catheter body such that a torque imparted to the handle can be transmitted to the catheter body. The handle includes: a grip portion adapted to be gripped in order to impart a torque; a torque transmitting portion operably coupled to the grip portion and the catheter body in order to transmit the torque imparted to the grip portion to the catheter body; and a torque limiting mechanism operable to decouple the torque transmitting portion from at least one of the grip portion and the catheter body when the torque imparted to the grip portion exceeds a torque threshold so that torques in excess of the torque threshold are not transmitted to the catheter body. Thus, in some embodiments, the torque limiting mechanism decouples the torque transmitting portion and the grip portion when the torque imparted to the grip portion exceeds the torque threshold. 
     Optionally, the grip portion can be movable relative to the torque transmitting portion between a first position and a second position. When the grip portion is in the first position, the torque limiting mechanism is engaged such that torques in excess of the torque threshold are not transmitted to the catheter body, and, when the grip portion is in the second position, the torque limiting mechanism is disengaged such that all torques imparted to the grip portion are transmitted to the catheter body. 
     A collet can also be positioned around the grip portion of the handle such that tightening the collet increases the torque threshold and loosening the collet decreases the torque threshold. 
     The ordinary artisan will appreciate that a steerable catheter, such as a steerable introducer catheter, generally includes at least one pull wire extending from the handle through the catheter body. Thus, it is also within the spirit and scope of the present disclosure for the torque limiting mechanism to operate to prevent torques in excess of the torque threshold from being transmitted to the at least one pull wire. This advantageously reduces the likelihood of pull wire breakage. 
     In still another aspect of the present disclosure, a catheter includes: a catheter body having a proximal end; and a catheter handle coupled to the proximal end of the catheter body. The catheter handle includes torque transmitting means for enabling torques below a torque threshold to be transmitted to the catheter body and for preventing torques above a torque threshold from being transmitted to the catheter body. Optionally, the catheter also includes means for adjusting the torque threshold and/or means for disengaging the torque transmitting means such that all torques are transmitted to the catheter body. 
     An advantage of the present disclosure is that it reduces the likelihood of catheter shaft failure by limiting the amount of torque that can be applied to the catheter shaft. 
     Another advantage of the present disclosure is that it provides for a variable threshold for the amount of torque that can be applied to the catheter or shaft body. 
     Still another advantage of the present disclosure is that it allows a user to elect to disable or disengage the torque-limiting feature. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of a catheter including a handle according to the present disclosure. 
         FIG. 2  illustrates a perspective view of a section of a steerable catheter, cut away to show details. 
         FIG. 3  is a schematic perspective illustration of a catheter handle according to an embodiment of the present disclosure. 
         FIG. 4  is an end view of the catheter handle depicted in  FIG. 3 . 
         FIG. 5  illustrates a handle according to the present disclosure including a collet to adjust the torque threshold. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present disclosure provides a catheter handle that advantageously limits the amount of torque that can be imparted to the shaft (or “body”) of the catheter, thereby reducing the likelihood of failure of the catheter body. For purposes of illustration, the disclosure will be described in connection with a steerable introducer catheter, such as the Agilis™ and Agilis™ NxT Steerable Introducer Catheters of St. Jude Medical, Atrial Fibrillation Division, Inc. It should be understood, however, that the principles disclosed herein could also be practiced to good advantage in other contexts, and are particularly advantageous in connection with catheters and other medical devices that include pull wires embedded in the catheter walls. 
       FIG. 1  is a perspective view of an exemplary steerable catheter  10 . Catheter  10  includes an elongate catheter body  12  having a proximal end  14  and a handle  16  coupled to proximal end  14  of catheter body  12 . Handle  16  is coupled such that a torque imparted to handle  16  can be transmitted to catheter body  12 . 
     Catheter  10  can also include a hub  18  operably connected to an inner lumen within handle  16  for insertion or delivery of catheter assemblies, fluids, or any other devices known to those of ordinary skill in the art. Optionally, catheter  10  further includes a valve  20  operably connected to hub  18 , such as via suitable tubing  22 . 
       FIG. 2  is a perspective view of one embodiment of catheter body  12  such as can be employed in connection with the present disclosure. The details of construction of catheter body  12  will be generally familiar to those of ordinary skill in the art and therefore need not be described in detail herein. Briefly, however,  FIG. 2  depicts a multi-layer construction including an inner layer  24  defining a central lumen  26  and an outer layer  28  including a wire reinforcing layer  30 . Also depicted are a pull ring  32  including a flow hole  34  to facilitate bonding of pull ring  32  into catheter body  12 . Two pull wires  36  are coupled to pull ring  32  in order to deflect catheter body  12  as generally known in the art. Though pull wires  36  are depicted as encased in so-called “spaghetti tubes”  38 , it should be understood that they could alternatively be embedded directly in either inner layer  24  or outer layer  28  (that is, spaghetti tubes  38  could be omitted without altering the principles of the disclosure as described herein). 
     Additional aspects of the present disclosure will now be described with reference to  FIGS. 3 through 5 .  FIG. 3  is a schematic perspective illustration of handle  16  according to one embodiment.  FIG. 4  is a schematic end view of handle  16  according to the same embodiment of the present disclosure. 
     One of ordinary skill in the art will be generally familiar with conventional handle design for steerable catheters, including the use of various actuators and mechanisms to effect deflection of the distal end of catheter body  12 . Accordingly, handle  16  will only be described herein to the extent necessary to understand the present disclosure. 
     As seen in  FIGS. 3 and 4 , handle  16  generally includes two components: a grip portion  40  and a torque transmitting portion  42 . Grip portion  40  is adapted to be gripped (e.g., manually by a user or within a robotic control system) in order to impart a torque to handle  16 . Torque transmitting portion  42  is operably coupled to both grip portion  40  and catheter body  12  such that a torque imparted to grip portion  40  can be transmitted through torque transmitting portion  42  to catheter body  12 . 
     As shown in  FIGS. 3 and 4 , in some embodiments, grip portion  40  includes a longitudinally-extending bore within which torque transmitting portion  42  is disposed. Typically, grip portion  40  and torque transmitting portion  42  are substantially concentric—that is, their central longitudinal axes are generally coincident. 
     Handle  16  further includes a torque limiting mechanism. The torque limiting mechanism operates to decouple torque transmitting portion  42  from grip portion  40  and/or catheter body  12  when the torque imparted to grip portion  40  exceeds a torque threshold. Advantageously, therefore, the torque limiting mechanism prevents torques that might cause catheter body  12  to fail from being transmitted to catheter body  12 . 
       FIGS. 3 and 4  depict one embodiment of a torque limiting mechanism according to the present disclosure. As illustrated in  FIGS. 3 and 4 , grip portion  40  includes a first torque transfer mating structure  44  and torque transmitting portion  42  includes a second torque transfer mating structure  46 . First and second torque transfer mating structures  44 ,  46  are typically complementary to each other. That is, convex shapes in one of the structures mate with concave shapes in the other and vice-versa. In the embodiment shown in  FIGS. 3 and 4 , first and second torque transfer mating structures  44 ,  46  are ridged surfaces, such as oval-shaped, geartooth-like, or sawtooth-like surfaces. 
     It should be understood, of course, that other configurations of torque transfer mating structures  44 ,  46  are contemplated. For example, a clutch mechanism, such as that employed in a click-type torque wrench, could also be used. 
     Torque transfer mating structures  44 ,  46  are configured such that, below a torque threshold, torque transfer mating structures  44 ,  46  remain engaged such that, when a torque is imparted to grip portion  40 , the torque is transferred through torque transfer mating structures  44 ,  46  to torque transmitting portion  42 , and in turn to catheter body  12 . Torque transfer mating structures  44 ,  46  are further configured such that, if the torque imparted to grip portion  40  exceeds the torque threshold, torque transfer mating structures  44 ,  46  disengage, such that grip portion  40  “slips” relative to torque transmitting portion  42 , thereby preventing these larger, potentially damaging torques from being transmitted through torque transmitting portion  42  to catheter body  12 . 
     It should be understood that the torques imparted to grip portion  40  are also generally imparted to pull wires  36 . Thus, it can also be desirable to decouple grip portion  40  from pull wires  36  above a torque threshold to avoid, for example, breaking pull wires  36  via the application of excessive torques. 
     One of ordinary skill in the art will appreciate how to design torque transfer structures  44 ,  46  for a particular torque threshold (e.g., by applying principles of machine design, torque transfer structures  44 ,  46  can be designed to “slip” at a particular torque). For example, one could determine the torque at which catheter body  12  is likely to fail, select an appropriate safety factor, calculate the resultant torque threshold, and then apply design principles to configure torque transfer structures  44 ,  46  to “slip” at this calculated torque threshold. 
     It is also contemplated that handle  16  can further include a torque threshold adjustment structure that permits the torque threshold to be adjusted by a user of catheter  10 . For example, as shown in  FIG. 5 , a collet  48  can be positioned around grip portion  40 , such as near the proximal end of handle  16 . As one of ordinary skill in the art will appreciate from this disclosure, tightening collet  48  will increase the torque threshold (e.g., make it harder for grip portion  40  to slip relative to torque transmitting portion  42 ), while loosening collet  48  will decrease the torque threshold (e.g., make it easier for grip portion  40  to slip relative to torque transmitting portion  42 ). To facilitate this action, grip portion  40  can include slots  50  to allow grip portion  40  to change dimensions as collet  48  is tightened and loosened. 
     It can also be desirable in certain applications of catheter  10  to enable the user to disable the torque limiting features of handle  16 . Accordingly, in some embodiments of the disclosure, grip portion  40  can be movable (for example, slideable along arrow A in  FIG. 3 ) relative to torque transmitting portion  42  between a first position and a second position. In the first position, the torque limiting mechanism is engaged, for example as shown in  FIGS. 3 and 4 . In the second position, the torque limiting mechanism is disengaged, such that all torques imparted to grip portion  40 , regardless of magnitude, are transmitted to catheter body  12 . 
     This can be accomplished, for example, by tapering the ridged surfaces shown in  FIGS. 3 and 4  appropriately. Such a configuration also offers another method of varying the torque threshold. That is, when grip portion  40  is in the first position, the torque threshold is at its minimum, and, as the user slides grip portion  40  towards the second position, the torque threshold increases until it reaches its maximum when grip portion  40  reaches the second position. Of course, one can also effectively disable the torque limiting features of handle  16  by further tightening collet  48 , shown in  FIG. 5 , to such a degree that the torque threshold is above any torque that might be imparted to grip portion  40 . 
     Although several embodiments of this disclosure 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. For example although the disclosure has been described as having torque transmitting portion  42  disposed within grip portion  40 , such that torque transfer mating structures  44 ,  46  are disposed on the inner and outer surfaces thereof, it is contemplated that grip portion  40  and torque transmitting portion  42  could be arranged abutting each other, with torque transfer mating structures  44 ,  46  on the abutting end faces thereof. 
     It should also be understood that an additional advantage of the present disclosure is that, by limiting the force applied to soft tissue adjacent catheter  10 , the risk of tissue injury (e.g., puncture) can be reduced. 
     Similarly, steerable introducer catheters are often used to introduce medical devices with sensitive and/or delicate components, such as the piezoelectric crystals used in intracardiac echocardiography (“ICE”) catheters. Excessive torques applied to the introduce catheter can damage such devices; the present disclosure addresses this concern as well. 
     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 disclosure. Joinder references (e.g., 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 relation 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.