Catheter

Details Catheter Catheter

1999-04-23

2001-08-07

Peffley, Michael (Department: 3739)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C606S023000, C600S585000

Reexamination Certificate

active

06270476

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH
Not applicable.
FIELD OF THE INVENTION
The present invention relates to medical devices and more particularly to devices for minimally invasive surgery. It particularly relates to catheters and catheter-like devices for contacting tissue at a distal region from an entry incision.
BACKGROUND OF THE INVENTION
Many different types of catheters are used for various diagnostic and therapeutic procedures. One type of catheter has an elongated flexible shaft with a steerable distal end for negotiating a path through the vascular network or other passageway in the body of a patient. These long and flexible catheters are well-suited for non-invasive procedures. Another type of catheter has a rigid shaft and is useful for invasive procedures where a more local opening or direct access to a treatment site is available.
While rigid catheters may be useful in some applications, they have certain limitations as well. For example, without a shape especially adapted for reaching a particular location in the body of a patient, the rigid nature of the catheter limits the area of tissue that can be reached and treated by the catheter. Even where a relatively large incision is provided, tissue areas that are not at least somewhat directly accessible cannot be reached. Although rigid catheters can include a curvable distal tip to facilitate their placement or their movement past obstructions, such a tip is relatively small and is not generally effective to compensate for the limited range of motion due to the shape of the catheter.
In one particular application, rigid catheters are used in the treatment of cardiac arrhythmias. Some invasive procedures for treating cardiac arrhythmias include positioning a rigid catheter with a deflectable distal tip through a local surgical opening against, or into, a chamber of the heart. Since the rigid catheter has a predetermined shape, one must select a catheter that has the most appropriate shape for positioning the distal tip of the catheter in contact with the treatment site in view given the particular anatomical pathway to be followed in the patient. It will be appreciated that a large inventory of rigid catheters may be required to accommodate the various treatment sites and patient anatomies. Further, for a patient having a relatively uncommon anatomic configuration and/or a difficult to reach treatment site, all rigid catheters of an existing set may well have less than optimal shapes for positioning the somewhat flexible treatment tip in suitable contact with their targeted site. This may impair the prospects of successfully carrying out the treatment procedure, especially when the treatment is one such as an ablation treatment that relies on good tissue contact and operates locally upon the contacted tissue. While a catheter having a customized shape might in theory be assembled or fabricated, in practice this would not be feasible during the procedure. Furthermore, for an ablation catheter which must bear against tissue at the remote region to ablate a lesion, the contour followed by the catheter in reaching the target site will in general further restrict the direction and magnitude of the movement and forces which may be applied or exerted on the tip itself to effect tissue contact and treatment.
It would, therefore, be desirable to provide a catheter which, while having sufficient rigidity to facilitate positioning of the catheter to a selected location within the body of a patient, is also better adapted to reach or treat the particular targeted anatomy of the patient.
BRIEF SUMMARY OF THE INVENTION
The present invention in one aspect provides an instrument having a semi-rigid, shapeable shaft that is deformable to a desired contour and yet retains its shape for positioning and operating a distal treatment segment. Although primarily shown and described as a cardiac ablation catheter, it is understood that the device has other applications as well.
In one embodiment, a catheter includes a handle having a proximal portion facilitating handling of the catheter and a distal portion coupled to a semi-rigid shapeable shaft. The shaft has a rigidity such that the shaft retains one shape until being influenced to a further shape by the application of moderate pressure on the shaft. A selectively deformable distal segment configured for ablating target tissue extends from the shaft. In an exemplary embodiment, the distal segment is deflectable by control through the shaft to deflect by an angle of more than 360 degrees, e.g., to form a loop.
In another embodiment, the distal ablation segment is adapted to removably receive a second shaft, called a shaft extension herein, which extends from its distal end. Preferably, the extension is one of a set of extensions having distinct lengths, shapes or gripping features, and which are removably attachable either before deployment of the catheter, or following deployment of the distal portion toward the target tissue region. The shaft extensions may attach by a snap plug, by a threaded junction or otherwise, to form a catheter having an active treatment segment located intermediately along the shaft. The extension fixes the distal end of the active segment, to provide a second shaft or handle so that by exerting physical force on both ends of the distal segment, the ablation segment is formed to a desired curvature, or forced into contact pressure against the target tissue which is to be treated. In a representative embodiment, the shaft extensions are provided in a range of lengths from under one inch long to several or more inches long. The shorter ones may be adapted to butt against or suture to tissue and provide a fixed point against which force is exerted for controlling the distal aspect of the ablation segment. The longer ones may be adapted for manual gripping and in this case are used to manipulate or pull the assembly around or through occluded regions of tissue, and to flex, tension or otherwise urge the distal segment into effective ablation contact against tissue to be treated.
In accordance yet another feature of the invention, a thermally insulating body is deployed over a partial circumferential aspect of the treatment segment to shield adjacent or occluding tissue. Cryogenic energy is thereby effectively applied selectively to the targeted tissue. In different embodiments, the insulating body may be a pad extending over the inner (or the outer) surface, as viewed in the sense of curvature of the distal segment, or the insulation may be a cylindrical sheath cut away on one side. Preferably the insulating body is deployable, by an axial or rotational movement along the shaft over the distal segment, to selectively insulate and prevent unwanted ablation effects at one side thereof. The invention also contemplates a thermally insulating member forming a retractable cylindrical sheath entirely surrounding the ablation segment, and effective to protect tissue as the catheter is inserted into a cardiac chamber. Thereafter the sheath is retracted to expose the tip, or to expose the entire segment, once it has been placed at the treatment site.
The catheter is well suited for surgical procedures such as forming linear ablation lesions of a surgically accessed site, especially a remote or occluded site such as the posterior cardiac wall. After examination of the patient, the catheter shaft is shaped to achieve a predetermined configuration based on the particular anatomy of the patient and the location of tissue to be ablated. The shaped catheter is inserted into the patient's body and moved to position the distal segment in contact with the intended tissue ablation site. The catheter is then actuated to treat tissue in contact with the distal segment.


REFERENCES:
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patent: 5109830 (1992-05-01), Cho
patent: 5281213 (1994-01-01), Milder et al.
patent: 5281215 (1994-01-01), Milder
patent: 5322064 (1994-06-01), Lundquist
patent: 5368049 (1994-11-01), R

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