Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-08-31
2001-03-20
Kennedy, Sharon (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
Reexamination Certificate
active
06203534
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a catheter shaft with a water-resistant protective covering.
BACKGROUND OF THE INVENTION
Typically, catheters are made of biocompatible plastics such as polyurethane and thermoplastic elastomer resins, such as Pebax®. However, when a catheter made from such a material is used during a surgical procedure, the catheter is kept in the body for periods lasting from one to eight hours. During this time, the plastic of the catheter absorbs body fluids and becomes softer over time. Experiments with typical polyurethane and Pebax shafts soaked in body-temperature distilled water confirm this conclusion. For example, it takes almost twice as much force to bend a dry Pebax® catheter over an angle of 60° compared to a Pebax® catheter soaking for an hour. Further, it takes more than twice as much force to bend a dry polyurethane catheter over an angle of 60° compared to a polyurethane catheter soaking for an hour. As a result, it becomes difficult for a physician to manipulate the catheter over the course of the procedure because the mechanical properties of the catheter change, with the catheter becoming harder to push, pull and turn. For example, a catheter that absorbs moisture looses its “pushability”, i.e., tends to perform like a wet noodle, becoming more difficult to push through the body. Additionally, in the case of catheters having a deflectable distal end, as the catheter shaft absorbs moisture, the deflectable distal end responds differently to the same movement of the handle over time. Further, the ability of the distal end to hold the deflection decreases, and it is more difficult to hold against the tissue. Accordingly, a need exists for a catheter that overcomes these disadvantages.
In an attempt to address some of these disadvantages, U.S. Pat. No. 5,545,151 (the '151 patent) discloses a catheter shaft formed from an inner layer of a particular blend of polyester and polyurethane, an outer layer formed from a different blend of polyester and polyurethane, and a reinforcing means therebetween. The '151 patent states that polyester-polyurethane blends are found not to absorb moisture and, hence, will not change in dimension when immersed in saline, body fluids and/or contrast media. However, a catheter shaft formed from a polyester-polyurethane blend has a particular feel and maneuverability that is different, for example, from a catheter shaft formed from polyurethane or Pebax. Physicians develop strong preferences for catheter shafts having a particular feel and mechanical properties, and are often reluctant to use a catheter having a different feel. Accordingly, a need exists for a way to modify a preexisting catheter shaft to reduce its ability to absorb moisture, while at the same time substantially retaining the mechanical properties and feel of the catheter.
SUMMARY OF THE INVENTION
The present invention is directed to a catheter having a shaft with a water-resistant protective covering along its length. The covering protects the catheter shaft, i.e., catheter body and tip section, from the elements of in vivo conditions, i.e., blood and other body fluids, and reduces softening of the catheter over time. The covering also adds a lubricious surface to increase the mobility of the catheter. However, the protective covering does not substantially affect the mechanical properties of the catheter. The protective covering is useful for any catheter or similar medical device, including, but not limited to, electrophysiology catheters and cardiology catheters.
In one embodiment, the invention is directed to a catheter having a shaft comprising a flexible plastic tubing having a least one lumen therethrough. The flexible plastic tubing is provided with a covering over at least about 50% of the shaft. The covering has a thickness less than about 0.004 inch and is formed of a material having a water vapor transmission rate of less than about 9.0 g-mil/100 in
2
-24 hr as determined by ASTM Test Method E 96 at about 90% relative humidity and about 37° C.
In another embodiment, the invention is directed to a catheter comprising a shaft and a handle. The shaft comprises a catheter body and a catheter tip section. The catheter body comprises a first flexible plastic tubing having proximal and distal ends. The catheter tip section comprises a second flexible plastic tubing mounted at the distal end of the catheter body. The second flexible tubing is more flexible than the first flexible plastic tubing. The shaft further comprises a protective covering over at least 50% of the shaft. The covering is formed of a material having a water vapor transmission rate of less than about 9.0 g-mil/100 in
2
-24 hr at about 90% relative humidity and about 37° C. The handle is connected to the proximal end of the catheter body. In a particularly preferred aspect of this embodiment, the covering comprises polyester (PET) having a water vapor transmission rate of less than about 2.0 g-mil/100 in
2
-24 hr at about 90% relative humidity and about 37° C., and the covering has a thickness of less than 0.0005 inch.
The invention is also directed to a catheter comprising a catheter shaft and a protective coating over at least 50% of the catheter shaft. The catheter shaft comprises a flexible plastic tubing made of a first material having a least one lumen therethrough. The protective coating is made of a second material having a lower water vapor transmission rate than the first material.
In another embodiment, the invention is directed to a catheter comprising a shaft and a handle. The shaft comprises a catheter body and tip section. The catheter body, which has at least one lumen extending therethrough, comprises an outer wall formed of a flexible plastic, an inner wall formed of a flexible plastic, and a reinforcement member between the outer wall and the inner wall. The catheter tip section, which is mounted on the distal end of the catheter body and has at least one lumen extending therethrough, comprises an outer wall formed of a flexible plastic, an inner core formed of a flexible plastic, and a reinforcement member between the outer wall and the inner core. The tip section is more flexible than the catheter body. The shaft further comprises a protective covering over at least 50% of its length. The covering is formed of a material having a water vapor transmission rate of less than about 9.0 g-mil/100 in
2
-24 hr at about 90% relative humidity and about 37° C.
In still another embodiment, the invention is directed to a catheter having a shaft comprising a flexible plastic tubing having a least one lumen therethrough. The flexible plastic tubing is provided with a covering over at least about 90% of the shaft. The covering is formed of a material having a water vapor transmission rate of less than about 9.0 g-mil/100 in
2
-24 hr at about 90% relative humidity and about 37° C. The percent difference in the bending stiffness of the catheter when provided with the covering compared to the same catheter without a covering is less than about 5% when the catheter is bent at an angle of about 60°.
In yet another embodiment, the invention is directed to a catheter comprising a catheter body and a basket electrode array mounted at the distal end of the catheter body. The catheter body has at least one lumen extending therethrough. The basket electrode array comprises a plurality of flexible arms connected at their proximal and distal ends. Each arm comprises a plastic material carrying at least one electrode. The plastic material of each arm is provided with a protective covering over its length. The protective covering has a water vapor transmission rate of less than about 9.0 g-mil/100 in
2
-24 hr at about 90% relative humidity and about 37° C.
In yet another embodiment, the invention is directed to a catheter having a shaft comprising a flexible plastic tubing having a least one lumen therethrough. The flexible plastic tubing is provided with a covering over at least about 90% of the catheter shaft. The covering is formed of a material
Biosense Webster Inc.
Christie Parker & Hale LLP
Kennedy Sharon
LandOfFree
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