Elongated medical instruments are widely used in modern medical procedures for surgery, drug delivery, imaging, and other functions at remote and/or relatively inaccessible locations in a patient's body.

Some examples of such instruments are catheters, endoscopes, remote biopsy tools, laproscopic instrumentation and the like. The operative portion of the instrument is typically at its distal tip or end portion. Proper use of such an instrument depends on the ability to properly orient the distal tip or end portion during the medical procedure.

Some instruments are relatively rigid and can be positioned and oriented by manipulating the proximal end of the instrument, which proximal end is not inserted into the patient's body. However, such relatively inflexible instruments generally cannot be used in procedures that require the instrument to pass along complex routes such as through circulatory system vessels.

The tips of flexible instruments can be difficult to properly position and orient by manipulating the proximal end of the instrument.

Accordingly, flexible instruments are sometimes provided with steering mechanisms. These steering mechanisms generally use a pair of pull wires connected to the tip of the catheter. When one of the wires is tensioned, the resulting differential force deflects the catheter tip laterally. Although widely used, pull wire steering mechanisms use fairly complicated tensioning devices at the handle of the catheter, which can add complexity and expense to pull wire systems.

It is therefore an object of the present invention to provide improved structures and methods for controlling steering movements of the distal portions of elongated medical instruments.

Summary of the Invention This and other objects of the invention are accomplished in accordance with the principles of the present invention by providing an elongated medical instrument which includes two elongated structures that are constrained to remain substantially parallel to one another but that are longitudinally movable relative to one another. A first of these elongated structures has a relatively stiff medial portion and a relatively flexible distal portion. The second elongated structure has a resilient distal portion which is resiliently biased into an alignment different from the alignment of the medial portion of the first elongated structure. When the distal portion of the second structure is adjacent the medial portion of the first structure, the stiffness of the medial portion forces the second structure to substantially conform to the

alignment of the medial portion. But when the distal portion of the second structure is pushed distally beyond the medial portion and into adjacency with the distal portion of the first structure, the relatively flexible distal portion of the first structure substantially conforms to the alignment of the distal portion of the second structure. For example, the medial portion of the first structure may be substantially straight and the distal portion of the second structure may be resiliently biased to curve (e.g., into an arc of a circle). Depending on how much of the distal portion of the second structure is adjacent the distal portion of the first structure, the distal portion of the first structure can be made to deflect more or less.

An illustrative embodiment of the invention is an instrument including a tubular structure (the first elongated structure mentioned above) in which the angular orientation of the distal portion of tubular structure is controlled by adjusting the axial position of a wire (the second elongated structure mentioned above) within the tubular structure. The distal portion of the wire is curved. The proximal portion of the wire protrudes from the instrument and may be manipulated by a physician. Near the distal end of the instrument, the tubular structure has a medial, stiffened, straight portion. When the curved portion of the wire is retracted into the stiffened portion of the tubular structure, the distal portion of the instrument tends to assume a straight, undeflected orientation. When the curved distal portion of the wire is advanced beyond the distal edge of the stiffened portion, the wire can begin to resume its curvature, and it therefore begins to deflect the

distal portion of the instrument. The physician can remove the wire from the instrument to customize the curvature of the wire. The rotational orientation of the distal portion of the instrument can be controlled by rotating the wire about its longitudinal axis relative to the tubular structure.

One of the advantages of this invention is that it allows the orientation of the catheter tip to be controlled without using potentially highly stressed pull wires.

Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.

Brief Description of the Drawinas FIG. 1 is a simplified perspective view of an illustrative steerable medical instrument constructed in accordance with the invention in which the distal portion is in an undeflected position.

FIG. 2 is another simplified perspective view of the steerable instrument of FIG. 1 in which the distal portion is in a deflected position.

FIG. 3 is a simplified perspective view of just the distal portion of an illustrative steerable medical instrument in accordance with the invention having fiber optics and a snare.

Detailed Description of the Preferred Embodiments An illustrative steerable medical instrument 10 in accordance with the present invention is shown in FIG. 1. Member 12 of instrument 10 is preferably an elongated member suitable for longitudinal insertion into the body of a patient during a medical procedure.

Wire 14 reciprocates within lumen 15 (partly shown in FIG. 2) in member 12. Wire 14 is inserted into lumen 15 through proximal opening 18. Lumen 15 is preferably closed at distal end 20, but it may instead be open if desired.

Stiffening member 22 may be formed using a tube, braided cage, rib-type structure, or any other suitable structure for stiffening member 12.

Stiffening member 22 may be formed of metal, plastic, or any other sufficiently stiff material. Preferably, stiffening member 22 is a tubular stiffening cage formed from a stainless steel braid with a polyimide covering. Stiffening member 22 is approximately two inches (5 cm) long and is preferably located a comparable axial distance from distal end 24 of member 12. These structures, materials, and dimensions are only illustrative and any other suitable combination of structures, materials, and dimensions may be used.

With wire 14 inserted in member 12, the portion 26 of instrument 10 between medial stiffening member 22 and proximal end 28 of instrument 10 is preferably flexible enough to allow portion 26 to flex during insertion through narrow and twisted body organ structures such as blood vessels. On the other hand, portion 26 is preferably stiff enough to allow instrument 10 to be advanced into various organ structures by the physician.

If desired, portion 26 may be more inflexible than is suggested above, which may be appropriate for procedures that do not require portion 26 to flex to accommodate insertion into twisting passages.

Regardless of the flexibility of proximal portion 26, the distal portion 30 of member 12 between stiffening member 22 and distal end 24 is preferably

stiff enough to assume the straight, undeflected alignment shown in FIG. 1 when wire 14 is withdrawn from within portion 30.

Distal portion 32 of wire 14 has a predefined curved shape when not confined by stiffening member 22.

The position of wire 14 within member 12 may be controlled by the physician by manipulating wire positioning member 36. When distal wire portion 32 is pushed beyond edge 34 of stiffening member 22, distal wire portion 32 begins to assume its natural curved shape and deflects distal member portion 30, as shown in FIG. 2.

The extent of the lateral or angular deflection of distal member portion 30 can be adjusted by controlling the length of distal wire portion 32 that extends beyond edge 34. The lateral or angular deflection of distal member portion 30 is greatest when all of distal wire portion 32 extends beyond edge 34.

When distal wire portion 32 is fully retracted, distal wire portion 32 is confined by stiffening member 22 and there is no lateral deflection of distal member portion 30. When a fraction of distal wire portion 32 extends beyond edge 34, the lateral deflection of distal member portion 30 is less than the lateral deflection when distal wire portion 32 is fully extended but greater than the lateral deflection when distal wire portion 32 is fully retracted.

Wire 14 is preferably constructed from highly elastic nitinol or stainless steel and has a diameter approximately in the range of 0.019 to 0.040 inches.

Wires 14 of this construction generally have sufficient torsional stiffness to reliably transfer torque from wire positioning member 36 to distal wire portion 32.

Thus the physician can also rotate wire positioning

member 36 and thereby wire 14 relative to member 12 to change the direction of lateral deflection of distal portion 30 produced by wire 14. The physician can therefore adjust both the amount of lateral deflection and the rotational orientation of that deflection by controlling the axial and rotational movement of wire 14.

If desired, the physician can withdraw wire 14 from member 12 entirely to customize the curvature of distal wire portion 32. For example, if the physician wishes to increase the maximum angular deflection of distal member portion 30, the physician can increase the curvature of wire 14 (e.g., by manually curling distal wire portion 32). The physician may also customize the curvature of distal wire portion 32 by selecting a replacement wire 14 with a different natural curvature at its tip. After customizing the curvature of wire 14, the physician inserts wire 14 into member 12.

The lateral and rotational control features of instrument 10 can be used in a variety of medical applications. For example, instrument 10 can be an imaging or illuminating device, a surgical instrument, a drug delivery instrument, a catheter (e.g., for balloon angioplasty and/or stent delivery), a device for irrigating and/or draining a patient, or a combination device including the features of two or more of these or any other suitable instruments.

Goldsteen et al. U.S. patent application No.

08/745,618, filed November 7, 1996, and Sullivan et al.

U.S. patent application No. 08/844,992, filed April 23, 1997, show intralumenal bypass procedures which can be performed in part with the aid of instruments of the type shown herein. These references are hereby

incorporated by reference herein in their entirety.

One or more lumens such as lumens 38 and 40 may be included in member 12 to provide passageways for the performance of various functions by instrument 10. For example, lumen 38 may contain fiber optics for imaging, and lumen 40 may house an axially reciprocable snare.

(Although the interior portions of lumens 38 and 40 and wire lumen 15 are only partly shown in FIG. 2 to avoid over-complicating the drawings, lumens 15, 38, and 40 extend axially though the entire length of member 12.) Other suitable instrument configurations may involve the use of angioplasty balloons, fiber optics for illumination or laser ablation, cutting and biopsy tools, anchoring wires, and irrigation or drainage ports.

An illustrative instrument tip 38 having snare 40, fiber optics port 42, fiber optics 44, and sealed wire lumen opening 46 is shown in FIG. 3. If instrument tip 38 is used for optical imaging, port 42 may have integral imaging capabilities. Snare 40 may be axially reciprocated in and out of its associated lumen 48 and may be provided within a coaxial separately reciprocable sheath 50, as described in Bachinski et al. U.S. patent application No. 08/844,910, filed April 23, 1997, which is hereby incorporated by reference herein in its entirety.

It will be understood that the foregoing is only illustrative of the principles of the invention, and that various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.