MXPA99008470A - Rotatable control mechanism for steerable catheter - Google Patents

Abstract

A steerable catheter control mechanism comprises a rotatable driver and a deflection device responsive to the driver to selectively secure a pair of control wires. The control wires are positioned such that rotation of the driver reduces the effective deflection device radius while loading a selected wire in tension, thereby maintaining a relatively constant torque acting on the driver and minimizing operator fatigue. The deflection device is also responsive to the driver to selectively place one of the control wires in tension while maintaining the other wire in a static state thereby minimizing control wire fatigue.

Description

ROTATING CONTROL MECHANISM FOR DIRECTED CATHETER Field of the Invention The invention relates to the field of steerable catheters and, more particularly, to a rotary control mechanism for use with the steerable catheter to minimize fatigue of the control wire. BACKGROUND OF THE INVENTION Physicians commonly have more frequent access to the interior of the human body to perform tissue diagnostics or impaired surgical procedures. As an indispensable tool for such procedures, catheters conveniently provide a means of access without the invasive trauma frequently associated with, for example, open-heart surgery. Inserted into the vasculature of the body, said catheters must be able to be precisely controlled in their position, as examples are the ablation electrodes or probes for imaging nearby specific tissues of interest. To allow for accurate manipulation of the catheter within a vasculature, those skilled in the art have implemented control wire mechanisms that selectively "direct" the distal tip of the catheter while the operator inserts the device into the body. Such mechanisms typically include a pair of control wires with distal ends employed at specific locations to the distal tip of the catheter body corresponding to a predetermined deflection movement. The proximal ends of the wires are mounted to a rotary actuator that responds to the operator to place one of the wires in tension, pulling the end of the catheter for deflection in a first direction, while simultaneously compressing, or flexing the other wire. An example of such catheter configuration incorporating said control mechanism can be found in USP No. 5,383,852, assigned to the assignee of the present invention. While such devices generally provide a relatively high degree of directional deflection for the catheter tip, for a relatively short time, the repetitive tension and bending of the control wires can cause fatigue of the control wire. As a result, the operable life of the device can be substantially shortened. To address the problem of wire fatigue in a steerable catheter, a proposal, by Thompson (USP No. 5, 358,478), discloses a rotating cam formed with a first cam surface of a first radius on the right side of a steer wheel. asymmetric cam The left side of the cam wheel is formed with a second cam surface of a different second radius. The rotating cam includes threaded holes for threading threaded seals. The proximal ends of the first and second steerable cables pass through central openings formed in the respective seals and are joined to the respective steerable wire terminals. During operation, by driving the rotary cam to the left, the second steerable wire detent is brought against the left terminal block and the cam surface. This movement tightens the second steerable cable to deflect the catheter tip to the left, while the first steerable cable remains relaxed. Likewise, the drive of the rotating cam to the right places the first steerable cable in tension while the second steerable cable remains relaxed. While this device works well for its intended purposes, operators may experience fatigue when handling the catheter for a long time. This can occur because the radius of the cam wheel with respect to the loaded control wire increases as the load increases. The additional load causes greater torque in the actuator, contributing to the fatigue of the operator within a relatively short time. A second proposal to direct control wire fatigue, by Lundquist (USP No. 5,395,327), describes independently tensioning a first steerable cable while simultaneously maintaining a second steerable cable at rest. The device includes two separate cam wheels arranged in line along the body of the catheter and attached to the respective steerable cables. The cam wheels are attached independently to the operator's knobs separately. During use, the operator rotates the wheel to place the wire in tension and consequently, flex the tip of the catheter. To perform the deflection in another direction, the operator operates the other knob. As the load on each wheel increases the tension of the respective cables, the torque on the respective knobs increases correspondingly. As a result, operator fatigue may occur within a relatively short time. In addition, due to the arrangement of double knobs, the operation of the device is somewhat more complex than a unit knob configuration. Therefore, there is a need for an improved steerable catheter control mechanism that minimizes control wire fatigue. In addition, there is a need for a control mechanism capable of minimizing operator fatigue. The control mechanism of the present invention meets these needs. COMPENDIUM OF THE INVENTION The control mechanism of the present invention provides the ability to selectively place a control wire under tension while simultaneously maintaining the other wire in a static state. By maintaining the static state, the fatigue of the control wire due to repetitive bending is substantially reduced to the minimum. In addition, the present invention also minimizes operator fatigue by maintaining the torque on the actuator at a constant level during the increased loading of the control wire. To realize the advantages identified above, the control mechanism of the present invention, according to one embodiment, manipulates a pair of control wires having respective distal portions employed, to the distal end of a steerable catheter. More specifically, the control mechanism includes a rotary impeller about a central axis and a deflection device coupled to the impeller to selectively secure the proximal ends of the control wire. The deflection device is formed with an eccentric deflection surface for tangentially coupling the control wires and includes a reducible radius in response to rotation of the impeller from a predetermined neutral position. The deflection device is operative, as the impeller rotates in a selected radial direction, to place one of the selected wires in tension as the radius decreases and correspondingly reduces the torque acting on the impeller, thereby reducing the minimum operator fatigue. Other aspects and advantages of the present invention will become apparent from the following detailed description when read together with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view of a steerable catheter that implements a rotary control mechanism according to an embodiment of the present invention; FIGURE 2 is a partial cross-sectional view along line 2-2 of Figure 1; FIGURE 3 is a developed perspective view of a rotary control mechanism according to one embodiment of the invention; FIGURE is a diagrammatic illustration of the control mechanism in a neutral position; FIGURES 5-6 are diagrammatic illustrations showing the rotational activation of the control mechanism; and FIGS. 7-9 are diagrammatic illustrations showing the movement of distal deflection of the distal end of the catheter corresponding to the activation of the control mechanism shown in Figures 4-6. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Catheters for medical practitioners or operators are an indispensable tool to conveniently access the interior of the human body without the level of trauma commonly associated with more invasive surgical techniques. As shown by the example of Figure 1, a steerable catheter according to an embodiment of the present invention, and generally designated 12, includes an elongated hollow handle 14. The inside of the handle defines a compartment 15 for housing a control mechanism according to the present invention and generally designated 30. Referring now to Figure 1, a narrow flexible arrow 16 projects longitudinally from one end of the handle for intravascular insertion. The arrow is normally formed of a polyurethane material of a predetermined stiffness and includes one or more longitudinally extending lumens (not shown) for running two or more control or steering wires 18 and 20 (Figures 7-9) through thereof. To accurately address the distal end of the catheter 16 during intravascular insertion the control wires 18 and 20 run longitudinally through the lumen of the catheter shaft and are mounted respectively to the specific distal points on the shaft so that the tension in a selected wire deflects the arrow in a predictable direction. The proximal ends of the control wires usually end in the respective pins 22 and 24 (Figure 3) to anchor the control mechanism 30 within the compartment 15. Referring now to Figures 2 and 3, the control mechanism of the present invention 30 incorporates a rotary impeller 32, and a deflection device 60 having a reducible radius in response to activation of the impeller and capable of selectively placing one of the two control wires in tension while keeping the other wire in a static state .

Referring now to Figures 2 and 3, the impeller 32 comprises a circular butterfly wheel 34 centrally formed with a cylindrical spindle 38 projecting axially from an internal flange 40 of the butterfly wheel. The spindle includes an axial through hole formed centrally to receive a threaded fastener 48 which rotatably assembles the impeller to a threaded hole formed in the compartment 15. An annular channel 50 formed externally on the spindle provides a radial groove for fixing a spindle retainer 52. An axially projecting driving bolt 42 is disposed at a predetermined radial distance from the spindle 38 and provides an important aspect selectively actuated the deflection device 60 to produce tension in one of the wires in accordance with the directional rotation of the butterfly wheel. For maximum control, the butterfly wheel 34 is formed with a finely sawn outer periphery 44. Additionally, to conveniently fix the control mechanism 30 in a neutral position, a thick locating groove 46 is configured in the wheel to open vertically and presents an identifiable brand as "neutral". The deflection device 60 comprises a pair of independently actuable eccentric pulleys 62 and 64, respectively formed with axial openings 66 and 68 for receiving the spindle 38 in coaxial reaction. The pulleys are formed as a mirrorless pair of images, with respective eccentric deflection surfaces 70 and 72 respectively defining a variable radius in relation to the center of the spindle, which defines a central axis. At the periphery of the deflection surface the respective grooves 74 and 76 are formed to tangentially couple and wind the respective control wires 18 and 20 during operation. A particularly advantageous aspect of the present invention involves the orientation of the deflection surfaces 70 and 72 with respect to the control wires so that the actuation of a selected pulley reduces the radius between the coupling point with the control wire and the control wire. central axis. Reducing the radius by approximately half, the inventor has discovered that the torque acting on the thumbwheel can be kept substantially constant under proportionally increasing stress loads on the selected pulley, thereby correspondingly lowering the operator's fatigue. The pulleys 62 and 64 are further formed with the respective actuator ears 78 and 80 raised radially outwardly from the respective rear portions of the pulley. The respective ears are deflected in a mirror relationship, when assembled to the butterfly wheel, to be mounted on the drive pin and effect selective activation of a respective pulley in response to the directional advance of the drive pin. The axial openings 82 and 84 formed close to the ears serve to radially anchor the respective control wire bolts 22 and 24.

The assembly of the control mechanism 30, comprises direct techniques well known to those skilled in the art and begins by first mounting the spindle to the butterfly wheel 34. With the arrow of the catheter positioned in a substantially straight orientation, the control wire bolts respective 22 and 24 are inserted into the openings formed complementarily 82 and 84 on the respective pulleys. The spindle can then be inserted coaxially to the respective pulleys with the drive bolt 42 placed in the middle between the two symmetrically deviated ears 78 and 80. To maintain axial alignment, the spindle detent 52 nests securely within the annular channel 50 and includes a radially projecting flange 88 to minimize relative axial movement between the pulleys. Once the sub-assembly of the control mechanism is completed, the manufacturer can then proceed to install the subassembly in a suitable housing or handle as is well known in the art. Usually, the control mechanism will be installed so that the butterfly wheel projects out from the handle to effect an unobstructed operator access. After installation, the control mechanism is calibrated with respect to the catheter shaft so that the "neutral" position indicator 46 corresponds to the shaft that is in a relaxed state with the respective control wires in a static state. A portion of the calibration includes orienting the respective pulleys so that the point of contact with the respective wires, as shown in Figure 4, form a radius "R" with respect to the central axis. During operation, the catheter assembly 12 will normally be graduated to the relaxed or calibrated neutral configuration, as shown in Figures 4 and 7. The visual confirmation of the neutral state can be returned simply by reference to the position of the formed slot 46 , normally a vertical opening. The catheter can then be inserted into the vasculature of interest. Once inserted into the body, manipulation of the distal tip of the catheter can be effected by turning the thumbwheel in a direction corresponding to the desired deflection direction. Referring now to FIG. 5, the clockwise rotation of the wheel radially displaces the drive bolt 42 to engage the upper ear 78 of the pulley 62 and effect activation in the rotation of the direction of rotation. butterfly wheel. The rotation of the pulley causes a winding action on the anchored lower wire 18 and orientates the deflection surface 70 in tangential coupling with the wire to place it in tension. The action of the deflection surface effectively pulls on the wire to correspondingly deflect the distal tip of the catheter shaft 16, as shown in FIG. 8. In operation, the activation of the butterfly wheel produces a lever of a corresponding magnitude. to the radius of the pulley between the coupling point with the tensioned wire and the central axis. The length of the lever arm or radius, contributes to the torque experienced by the operator in the activation of the butterfly wheel. Although the continuous rotation of the pulley has increased the load of tension on the wire, because the radius of the pulley decreases to a radius "r" (Figure 5) with continuous rotation, the torque experienced in the butterfly wheel which results from the combined effects of the additional voltage and the reduced radius remains substantially constant. Therefore, for a time, the operator fatigue of varying levels of torque is substantially reduced. While the activation of the selected pulley of the butterfly wheel subjects the lower wire 18 to a tension force, the upper wire 20, being anchored to the unaltered pulley 64, remains in a static state. The independent relationship between the two pulleys and the unidirectional play between the respective driving ears and the driving bolt preserves the static nature of the other pulley and consequently, the wire. This aspect virtually eliminates the compression or bending of the non-selected wire. and substantially inhibits premature wire fatigue due to said bending. To manipulate the tip of the catheter in another direction, the operator only rotates the butterfly wheel backward so that the guide pin retracts from the upper pulley ear 78. During retraction, the tension accumulated in the wire serves as a drive means to return the pulley 62 back to its calibrated neutral state or static state. The continuous backward rotation of the throttle wheel then directs the drive bolt 42 in contact with the ear of the lower pulley 80 to drive the other pulley 64. Figures 6 and 9 illustrate this activity, with results similar to those discussed before. While the control mechanism of the present invention have been described as a single manipulation device for the catheter shaft, it will be understood that one or more control mechanisms may be implemented to complement the invention. For example, the capabilities of the present invention can be supplemented by a slidable control mechanism (not shown) disposed proximate to the butterfly wheel to effect a steerable control on the additional control wires with a path through the arrow and anchored to the distal end of the arrow. A suitable slidable control mechanism is described in co-pending application of the applicant S / N 08 / 818,352, assigned to the assignee of the present invention and incorporated herein by reference. Those skilled in the art will appreciate that many benefits and advantages given by the control mechanism of the present invention. Of significant importance are the reducible spokes of the respective deflection surfaces of the pulley which provide a relatively constant torque on the thumbwheel even with increases in the tension load of the selected wire. By maintaining a constant level of torque, operator fatigue is minimized significantly. In addition to minimizing operator fatigue, the present invention also significantly reduces premature wire fatigue due to compression or bending of unloaded wire during operation. This aspect is realized by implementing rotating pulleys independently that respond to the directional displacement of the butterfly wheel. While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. .

Claims (23)

1. A control mechanism for manipulating a pair of control wires to have respective distal portions anchored to the distal end of a steerable catheter corresponding to predetermined directional deflections of said catheter, said control mechanism includes: a rotary impeller about a central axis; and a deflection device coupled to said impeller for selectively securing said proximal ends of the control wire and which is formed with an eccentric deflection surface for tangentially coupling said control wires, said surface having a reducible radius in response to the rotary impeller from a predetermined neutral position, said operative device, as said device rotates in a selected radial direction, to place one of the wires in selected tension of said radius reduces and, correspondingly, decreases the action of the torque on said impeller where it reduces to the minimum operator fatigue.

2. A control mechanism according to claim 1, wherein: said surface is formed such that said rotation of said impeller decreases, proportionally, the radius to said tension to maintain a constant torque in the impeller.

3. A control mechanism according to claim 1, wherein: the controller comprises a manually controllable actuator; and said deflection device comprises at least one eccentric element that responds to the rotary movement of said actuator.

4. A control mechanism according to claim 3, wherein: the actuator comprises a circular butterfly wheel.

5. A control mechanism according to claim 3, wherein: at least one eccentric member comprises at least one eccentric cam pulley.

A control mechanism according to claim 1, wherein: the deflection device comprises a pair of independent rotating camshaft pulleys arranged coaxially on the central axis of the impeller and responsively responsive to the rotation of the impeller to place one of the wires in tension selected.

A control mechanism according to claim 6, wherein the butterfly wheel includes a shaped fastener disposed radially outwardly from the central axis; and the pulleys include. respective shaped ears projecting radially outwardly to selectively couple said bolt as the butterfly wheel rotates in a selected direction thereby placing one of said selected wires in tension.

8. A control mechanism according to claim 1, wherein: the deflection device is formed with at least one fastener for selectively securing the control wires.

9. A control mechanism according to claim 8, wherein: the fasteners comprise unidirectional detents, when the device rotates, to pull one of the wires at selected tension while simultaneously maintaining the other wire in a static state.

10. A control mechanism for manipulating a pair of control wires having the respective distal portions anchored to the distal end of the steerable catheter corresponding to predetermined directional deflections of said catheter, the control mechanism includes: a rotary impeller about the central axis; and a deflection device coupled to said impeller and comprising a pair of independent rotary pulleys arranged coaxially on the central axis, the pulleys respond selectively to a directional rotation of the impeller, since the impeller rotates in a selected radial direction, to place one of the wires selected in tension while the other of the pulleys matures the other of the wires in a static state so it minimizes the fatigue of the control wire.

11. A control mechanism according to the claim 10, wherein: the impeller comprises a manual control actuator; and the pulleys are sensitive to the directional rotation of the actuator.

12. A control mechanism according to the claim 11, wherein: the actuator comprises a circular butterfly wheel.

13. A control mechanism according to claim 10, wherein: the pulleys comprise cam pulleys.

A control mechanism according to claim 12, wherein: the butterfly wheel includes a formed pin disposed radially outwardly from the central axis; and the pulleys include respectively formed ears projecting radially outwardly to engage the pin as said actuator rotates in a selected direction thereby placing one of the wires in tension.

15. A control mechanism according to claim 12, wherein: the eccentric pulleys are each formed with an eccentric deflection surface for tangentially coupling said control wires, said surface having a reducible radius in response to the rotation of the actuator from a predetermined neutral position, the operating pulleys, as the impeller rotates in a selected radial direction away from the neutral position, to place one of the wires in selected tension as the radius is reduced and the torque action correspondingly decreases Torque acting on the impeller minimizing operator fatigue.

16. A control mechanism according to claim 15, wherein: the respective deflection surfaces are formed in such a way that the rotation of one of the selected cams proportionally decreases the radius of said tension to maintain a constant torque in the impeller

17. A steerable catheter for controllable manipulation through a vasculature, said catheter comprising: an arrow having a distal end; at least two control wires having portions respectively distal to said distal end of the arrow and corresponding to the predetermined directional deflections of the arrow; and a control mechanism on the arrow, said control mechanism includes: a rotary impeller about a central axis; and a deflection device coupled to the impeller for selectively securing said proximal ends of the control wire, the device comprises independently rotatable eccentric cam pulleys, arranged coaxially on the central shaft and selectively responsive to the rotation of the impeller, each pulley being formed with a deflection surface tangentially engaging the control wires, the surface has a reducible radius in response to the rotation of the impeller from a predetermined neutral position, said operative device, as the impeller rotates in a selected radial direction, one of the selected pulleys are placed on one of the selected tension wires, while the other of the pulleys keeps another of the cables in a static state and the continuous rotation of the actuator reduces said radius correspondingly decreasing the torque action on the driving.

18. A control method for minimizing fatigue of the steerable catheter, the catheter having a control mechanism that includes a rotary impeller about a central axis and a deflection device that is formed with an eccentric deflection surface having a radius reducible in response to rotation of the impeller from a predetermined neutral position, and a pair of control wires having distal portions anchored to the distal end of the catheter and selectively proximal portions secured to said deflection device, this method includes the steps of: coupling one of the control wires selected, tangentially with said deflection device in response to the rotation of the impeller; and reducing the radius through the continuous rotation of the impeller where the action of the torque of the actuator decreases and correspondingly reduce the fatigue of the operator.

19. A method according to claim 18, wherein: the reduction step includes reducing said effective radius proportionally to the tension in the application step to maintain a constant torque in the actuator.

20. A method according to claim 18, and further includes the step of: keeping the other of the control wires in a static state simultaneously with the application of the step to minimize wire fatigue.

21. A control method for minimizing fatigue of the control wire of the steerable catheter, said catheter having a control mechanism including an impeller and a pair of independent rotating pulleys arranged in a coaxial relationship with the impeller and including respective control wire fasteners to secure a pair of control wires having distal portions anchored to the distal end of the catheter and proximal portions selectively fastened to the respective pulleys, said pulleys respond selectively to the directional rotation of the impeller, said method includes the steps of applying tension in one of the control wires by rotation of the impeller to selectively rotate one of the pulleys, and keep the other of the control wires in a static state simultaneously with the application step to minimize wire fatigue.

22. A method according to claim 21, wherein each pulley is formed with an eccentric deflection surface having a reducible radius in response to rotation of the impeller from a predetermined neutral position, said method further including the step of: said radius through continuous rotation of the actuator where the torque action on the actuator decreases and correspondingly reduces operator fatigue.

23. A method according to claim 22, wherein: the reduction step includes reducing the effective radius proportionally to the tension in the application to maintain the constant torque on the actuator.