| 摘要 |
Improved catheters are provided. In one aspect, the catheters have a tapered, atraumatic distal tip (24). In one embodiment, the outer surface (36) of the distal portion of the catheter has a generally non-cylindrical and substantially triangular cross-sectional configuration. The inner surface cross-sectional configuration of the distal portion of the catheter may match the outer surface, or it may have a cylindrical or oval configuration (28). The terminal orthogonal surface of the distal catheter tip (24) is chamfered or rounded or contoured. In another aspect, catheters having selectively insertable, or selectively activatable and releasable, stiffening mechanisms are provided. Such catheters may be inserted, navigated and withdrawn from a subject in a relaxed, flexible condition, and stiffening mechanisms are deployed to prevent the catheter from shifting during placement or operation of an accessory device or tool through the catheter.
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