Catheter shaft and method of manufacture

#The instant invention relates to catheters that are used in the human body. In particular, the instant invention relates to a catheter assembly using multiple polymeric sections incorporating varying materials along its longitudinal axes to improve manufacturability of catheter shafts.

#Catheters are used for an ever-growing number of procedures. For example, catheters are used for diagnostic, therapeutic, and ablative procedures, to name just a few examples. Typically, the catheter is manipulated through the patient's vasculature and to the intended site, for example, a site within the patient's heart. The catheter typically carries one or more electrodes, which may be used for ablation, diagnosis, or the like.

#Since the path through the patient's vasculature to the intended site is often long and tortuous, steering forces typically must be transmitted over relatively great distances. Accordingly, it is desirable for a catheter to have sufficient axial (e.g., column) strength to be pushed through the patient's vasculature via a force applied at its proximal end (“pushability”). It is also desirable for a catheter to transmit a torque applied at the proximal end to the distal end (“torqueability”). Pushability and torqueability (collectively, “maneuverability”) permit a physician to manipulate a catheter to an intended site and then properly orient the catheter. It is also desirable for a catheter to have sufficient flexibility to substantially conform to the patient's vasculature and yet resist kinking as it does so. Kinking is often the result of a localized failure of the material of the catheter when localized stresses exceed the yield strength of the material.

#FIG. 1 is a longitudinal cross-sectional view of a reinforced catheter shaft according to an embodiment of the present invention.

#FIG. 2 is a similar longitudinal cross-sectional view of a reinforced catheter shaft which has had the outer layers of material removed from a distal end of the catheter shaft.

#FIG. 2A shows a variation of the embodiment of FIG. 2, in which inner layers of material have also been removed from the distal end of the catheter shaft.

#The present invention provides a catheter suitable for use in the human vasculature for known medical procedures, such as cardiac mapping and ablation. Catheters utilizing catheter shafts according to the present invention advantageously exhibit improved maneuverability, flexibility, and kink resistance. For purposes of this description, the invention will be described in connection with an elongate electrophysiology catheter. It is contemplated, however, that the described features and methods may be incorporated into any number of catheters as would be appreciated by one of ordinary skill in the art. Examples of catheters particularly appropriate to the present invention include, but are not limited to, fixed curve catheters, conformable catheters, bi-directional catheters, steerable catheters, introducer catheters, diagnostic catheters, and ablation catheters, both irrigated and non-irrigated.

#Many electrophysiology catheters such as those listed above are introduced into the vasculature in a similar manner at convenient points on the body (such as a femoral artery). Once introduced, if the ultimate target of the catheter is an organ such as the heart, the path followed to arrive at the final target tissue may be very similar regardless of what the working end of the catheter is ultimately intended to accomplish. Thus, the mechanical properties of the main shaft of a catheter navigating through the tortuous paths of the vasculature are usually similar regardless of the particular type of device being directed to the site. For instance, the main shaft of the catheter is typically soft and flexible enough to be easily manipulated along its length in a manner that allows it to twist and turn through many branches of the vascular system. At the same time, the main shaft should not be so soft that it becomes susceptible to kinking while it is being pushed at its proximal end. It should also have sufficient hardness to resist kinking when it comes into contact with an obstruction, such as a vessel wall.

#To improve maneuverability, flexibility, and kink resistance, many catheters utilize one or more reinforcing layers in their construction. For example, the guiding catheter disclosed in U.S. Pat. No. 4,817,613 to Jaraczewski et al. (“Jaraczewski”) includes a pair of braided torque transmitting layers sandwiched between a flexible tubular member and a flexible plastic casing applied as a viscous material and subsequently cured. Jaraczewski also teaches, however, that to a certain degree, flexibility comes at the expense of torqueability. Further, depending on the thickness of the torque transfer layers, they may increase the wall thickness, thereby either increasing the overall diameter of the catheter for a given bore size or decreasing the bore size for a given overall diameter.