Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2001-05-04
2003-11-18
Mendez, Manuel (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C600S585000
Reexamination Certificate
active
06648875
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to a steerable catheter, and more particularly to a catheter handle having a steering controller for applying tension to a tendon to steer the catheter and a system for maintaining tension on the steering tendon when it is not tensioned by the steering controller.
In many medical procedures, it is necessary to place a catheter at a particular location within the patient's body. Precise placement of the catheter is more easily accomplished when a steerable catheter is used. Such catheters are typically flexible at the distal end, and the profile at the distal end is deflectable.
Changing the profile of the distal-end region of a steerable catheter typically involves the use of a steering tendon that is housed within the catheter shaft. The steering tendon is usually a wire that has its distal end attached to the distal-end region of the catheter shaft. The proximal end of the catheter shaft attaches to a handle. The proximal end of the steering tendon exits through the proximal end of the catheter shaft and attaches to a steering controller within the handle.
The profile of the distal-end region of the catheter shaft can be deflected from its non-steered configuration by manipulating the steering controller from a neutral position so that the steering tendon is axially displaced in the proximal direction. Axially displacing the steering tendon in the proximal direction places the steering tendon in tension which is reacted by offset and opposing compressive forces within the catheter shaft. These opposing tensile and compressive forces create a bending moment that acts upon the distal-end region of the catheter shaft, preferentially on the side where the steering tendon is attached, thereby deflecting the distal-end region. If the steering controller is released, the distal-end region of the catheter shaft typically springs back to its natural state due to the structure of the catheter shaft, thus moving the steering tendon and the steering controller back to their neutral positions.
It is often necessary to maintain the force exerted on the steering tendon during the course of a medical procedure so as to retain the deflected profile of the distal-end region of the catheter. In some of the existing steerable catheters, maintaining the force exerted on the steering tendon requires the operator to manually hold the steering controller in place. However, it is often difficult for the operator to maintain a constant amount of force on the steering tendon for an extended period of time or while further manipulating the handle.
In other existing steerable catheters, an additional knob attached to the steering controller is used to lock the displacement of the steering tendon at its present position. This knob is used to tighten the steering controller against a friction plate within the handle housing until the resulting friction is sufficient to prevent the steering controller from moving from its present position. Typically, the operator must turn this knob with one hand while the other hand is used to maintain the preferred position of the steering controller relative to the handle housing. Thus, locking the steering controller in other steerable catheters is a two-handed operation.
Steerable catheters that utilize steering tendons can have either single or multiple steering tendons. During the use of a multiple-tendon steerable catheter, manipulation of the steering controller results in the application of tension to one steering tendon, while no force is deliberately applied to any other tendon. Tendon wires in steerable catheters are typically small in diameter in order to conserve catheter lumen space. Tendon wires are usually made of a wire material possessing a high modulus of elasticity and high yield strength so that they exhibit minimal elastic stretch and will not permanently deform under ordinary tensile loads. However, because of their relatively small diameters, catheter tendon wires can be easily bent and are prone to buckling when subjected to axial compressive forces.
The majority of a tendon wire's length is typically protected from bending by virtue of the inherent rigidity of the surrounding catheter shaft. Further, buckling of a tendon wire within the catheter shaft is unlikely because the tendon wire is typically supported by a dedicated tendon sheath or lumen, or at least by the wall of the main catheter lumen. However, within a catheter's handle, a tendon wire typically has an unsupported span between the proximal end of the catheter shaft and the steering linkage to which the tendon is attached. When subjected to repeated steering, this span may be susceptible to kinking, which can adversely affect the catheter's steering performance.
In some existing catheters, the proximal ends of all steering tendons are rigidly affixed to their respective linkage points. As a result, when tension is applied to only one tendon, the other tendons may be forced to bow or kink in response to the catheter shaft's unavoidable length change. Other steerable catheters attempt to avoid that problem by routing each steering tendon through a hollow stop within the handle's steering linkage system and affixing a terminal to the proximal end of each steering tendon. In that configuration (see
FIG. 1
a
), all terminals typically butt against their respective stop when the catheter is in its neutral (non-steered) position. When tension is applied to only one steering tendon to steer the catheter (see
FIG. 1
b
), the extraneous length in all other tendons can pass through their respective hollow stop. However, a corresponding gap between the hollow stop and the terminal then exists, resulting in a relaxed steering tendon that may be subject to bowing or kinking (see
FIG. 1
c
).
Hence, those skilled in the art have identified a need for an improved steering system for steering a catheter, and one that reduces or minimizes the slack in steering tendons. The present invention fulfills these needs and others.
SUMMARY OF THE INVENTION
Briefly, and in general terms, the present invention is directed to a system in which a steering controller includes a device to maintain the steering tendon in tension when it is not tensioned by the steering controller.
In a first aspect, the invention relates to a system for applying tension to a steering tendon. The tendon has a distal end that is attached to the distal-end region of a catheter shaft and a proximal end that exits the proximal end of the shaft. The system also includes a movable steering controller and means for coupling the tendon to the steering controller. Through the coupling means, movement of the controller in a first direction relative a neutral position increases tension on the tendon and movement of the controller in a second direction relative the neutral position, and opposite the first direction, maintains tension on the tendon.
In a detailed aspect of the invention, the coupling means includes a stop that is disposed at the controller and has the proximal end of the tendon passing therethrough and terminating at a point that is a distance from the stop, and a spring device that has a distal end at the stop and a proximal end attached to the tendon at a location proximal to the stop. In a more detailed aspect, the spring device is in a fully compressed state when the steering controller is in the neutral position and when the steering controller is moved in the first direction. In a further aspect, the spring device is in a partially compressed state when the steering controller is in the neutral position, and the compression increases when the steering controller is moved in the first direction. In another detailed aspect, the spring device extends in length, yet remains in compression, when the steering controller is moved in the second direction. In another detailed aspect, the spring device includes a wire coil that surrounds the tendon between the stop and the proximal end of the tendon. In yet another detailed aspect, the cathete
Hayzelden Robert C.
Simpson John A.
Cardiac Pacemakers Inc.
Fulwider Patton Lee & Utecht LLP
Han Mark K
Mendez Manuel
LandOfFree
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