Torqueable and deflectable medical device shaft

A medical device shaft for connection with a handle and for insertion within a body includes an elongated, deflectable shaft having a proximal shaft portion, an intermediate shaft portion, and a distal shaft portion. The elongated, deflectable shaft includes a transition in stiffness from the proximal shaft portion to the distal shaft portion. In a preferred implementation, the shaft includes a plurality of slits that extend perpendicular to a longitudinal axis of the shaft. Varying at least one of the number of slits, the location of slits, the frequency of slits, the orientation of the slits, the size of the slits, and the depth of the slits varies the transition of stiffness.

FIELD OF THE INVENTION

The present invention relates, in general, to deflectable medical device shafts, and, in particular, to deflectable catheter shafts.

BACKGROUND OF THE INVENTION

In order to facilitate the advancement of catheters through body lumens such as an artery, deflectable catheters have been developed. The simultaneous application of torque at the proximal portion of the catheter and the ability to selectively deflect the distal tip of the catheter in a desired direction permits the physician to adjust the direction of advancement of the distal portion of the catheter, as well as to position the distal portion of the catheter during, for example, delivery of an occlusive implant.

A physician may manipulate the proximal portion of the catheter to guide the catheter through the vasculature. The deflection of the distal tip is typically provided by one or more steering wires that are attached at the distal portion of the catheter and extend to a control handle that controls the application of tension in the steering wires. In order to maneuver around turns and bends in the vasculature, the physician observes the catheter fluoroscopically, and selectively deflects the tip and rotates the proximal portion of the catheter shaft.

It is critically important to have sufficient flexibility in the distal portion of the catheter shaft so that when the catheter is advanced through a blood vessel, the catheter may follow the inherent curvature of the vessel without puncturing the vessel wall. However, it is also important to maintain stiffness in the proximal portion of the catheter shaft to allow the distal portion of the catheter to be manipulated by the physician. Therefore, there exists a need for a catheter shaft having a flexible, atraumatic distal portion while maintaining a sufficiently stiff proximal portion.

SUMMARY OF THE INVENTION

An aspect of the invention involves a medical device shaft for connection with a handle and for insertion within a body. The medical device shaft includes an elongated, deflectable shaft having a proximal shaft portion, an intermediate shaft portion, and a distal shaft portion. The elongated, deflectable shaft includes a transition in stiffness from the proximal shaft portion to the distal shaft portion. In a preferred implementation, the shaft includes a plurality of slits that extend perpendicular to a longitudinal axis of the shaft. Varying at least one of the number of slits, the location of slits, the frequency of slits, the orientation of the slits, the size of the slits, and the depth of the slits varies the transition of stiffness.

Other features and advantages of the invention will be evident from reading the following detailed description, which is intended to illustrate, but not limit, the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference toFIG. 1, a catheter10including a torqueable and deflectable shaft or body20constructed in accordance with an embodiment of the present invention will now be described. The catheter10will first be generally described before describing the torqueable and deflectable shaft or body20. The catheter shaft20will be described as being used within the vascular system of a patient; however, the catheter shaft20may be used within other lumens, passages, ducts, tracts, openings, etc. in the body other than blood vessels. Further, the shaft20may be a torqueable and deflectable shaft or body of a medical device other than a catheter.

The catheter body20includes an operative distal tip portion50. The catheter10further includes a catheter handle60with a steering knob70to control the distal tip portion50of the catheter body20when guiding the distal tip portion50through the vascular system of the body. The steering knob70is attached to steering wires that extend through an interior lumen of the catheter body20. The steering wires terminate and are anchored near the distal tip portion50so that rotation of the steering knob70causes deflection and bending of the shaft20near the distal portion50as shown.

The operative distal tip portion50may take any known construction in the art. For example, but not by way of limitation, the operative distal tip portion50may include an implantable and detachable occlusion device, a probe assembly, an expandable basket assembly, an expandable balloon or body, one or more electrodes for sensing, pacing, and/or ablating, one or more markers for identifying the distal tip portion, an imaging device, and any combination of the above. In the embodiment of the operative distal tip portion shown, two ring electrodes100,110are disposed along the length of the distal tip portion50to provide radio frequency energy for ablation and/or sensing of electrical activity in body tissue. In addition, a radiopaque marker band120is secured to the distal tip portion50to facilitate visualization of the distal tip portion50inside the body using fluoroscopy.

FIGS. 2A and 2Brelate to illustrate the body or shaft20ofFIG. 1in more detail. The shaft20includes a proximal shaft portion140, an intermediate shaft portion145, and a distal shaft portion150. The shaft increases in flexibility from the proximal shaft portion140to the distal shaft portion150. The distal shaft portion150includes the distal tip portion50and is comprised of a ribbon braid170of counter-wound double Nitinol wires embedded in a layer of hydrophobic polymer180to prevent the braiding170from being exposed. The polymer layer180may be covered with a hydrophilic coating. This construction allows the distal shaft portion150to be flexible or bendable in a lateral direction to facilitate steering of the shaft20, but has enough torsional strength to allow torque to be efficiently transmitted by the user from the handle to the distal shaft portion150without give in the shaft150.

The ribbon braid170is preferably made from Nitinol in order to create a shaft that minimizes kinking, transmits a high amount of torque, and retains its shape after being bent. Importantly, a Nitinol braid170allows increased flexibility in the distal tip portion50, but keeps the interior lumen from collapsing by inhibiting kinking. Additionally, because Nitinol is a memory metal, a user may easily maintain the distal tip portion50in a desired shaped throughout a surgical procedure. In other embodiments, the braid170may be made of different materials such as metal alloys (e.g., stainless steel, carbon fiber).

The proximal shaft portion140and intermediate shaft portion145are preferably made of a substantially hollow Nitinol tubing182coated with the hydrophobic polymer layer180. The polymer layer180may be covered with a hydrophilic coating. The Nitinol tubing182is designed to transmit torque to provide a substantially one-to-one correspondence between rotation of the proximal shaft portion140and distal shaft portion150. The Nitinol tube182provides the shaft150with sufficient flexibility for advancing the shaft150through a tortuous lumen path and sufficient torsional strength to efficiently transmit torque from the handle60to the distal shaft150. The tube182is also preferably made of Nitinol to minimize kinking and because Nitinol is a memory metal that retains its shape after being bent. In other embodiments, the tube182may be a made of a material other than Nitinol such as, but not by way of limitation, carbon fiber or a metal alloy such as stainless steel.

The shaft20increases in flexibility from a proximal junction184, where the shaft20meets a luer attachment185, to a distal junction186, where the Nitinol tube182attaches to the Nitinol braid170of the distal shaft portion150. The increase in flexibility is created by making a plurality of slits or cuts188along the hollow tube182. These slits188extend perpendicular to a longitudinal axis of the shaft20. An increase in flexibility in the shaft20from the proximal junction184to the distal junction186may be achieved by increasing the depth of the slits188as one progresses from the proximal junction184to the distal junction186and/or by increasing the number of slits188per unit length of tube182as one progresses from the proximal junction184to the distal junction186. As best seen inFIG. 2A, the number of slits188per length of tube increases gradually from the proximal shaft portion140to the distal junction186. Additionally, the slits188become increasingly deeper toward the distal junction186. As a result, a transition in stiffness is formed, whereby the shaft20becomes progressively more flexible from proximal shaft portion140to distal shaft portion150. The number of slits188, location of slits188, frequency of slits188, orientation of the slits188, size of the slits188, and/or depth of the slits188may be varied to vary the transition of stiffness according to the desired application of the shaft20.

While preferred embodiments and methods have been shown and described, it will be apparent to one of ordinary skill in the art that numerous alterations may be made without departing from the spirit or scope of the invention. Therefore, the invention is not limited except in accordance with the following claims.