Catheters may be used to deliver diagnostic or therapeutic agents and devices to internal target sites that can be accessed through the circulatory or other system. There are a number of general approaches for placing catheters within vessels in the body to reach target sites that are difficult to access. In one technique, a torqueable guidewire is introduced into the vasculature and, using radiography to monitor its advance through the body's passageways, is rotated as necessary to allow the guidewire's bent guide tip to follow a chosen route (when a choice of pathways is found) and is advanced towards the target site. At chosen intervals during the guidewire's advancement, the catheter is slid along the guidewire until the distal end of the catheter approaches the distal end of the guidewire. This procedure is repeated until the distal end of the catheter is positioned at the target site. An example of this technique is described in U.S. Pat. No. 4,884,579. This is a widely accepted and respected method for approaching target sites in complicated areas of the vasculature. It, however, has the drawback of being somewhat time-consuming due to the necessity of rotating and advancing the guidewire and catheter through the vasculature.
A second technique for advancing a catheter to a target site is to use the blood flow as the motive force in placing the distal end of the catheter at the desired target site. Such methods often employ a highly flexible catheter having an inflatable, but pre-punctured balloon at its distal end. In use, the balloon is partially inflated, and carried by blood flow into the target site. During placement, the balloon is continually inflated to replenish fluid leaking from the balloon. This technique, too, has drawbacks including the fact that at least the distal portion of the catheter is so floppy that it cannot be pushed without buckling. Instead, the catheter must be advanced using injected fluid to inflate the balloon to propel the catheter to the target site. There is the additional risk of rupturing a vessel with a balloon that has been overinflated.
In order to address some of the above described problems, another approach has involved the use of flexible catheters having extremely flexible distal portions that can be directed to a target site using the blood flowing to that site as the motive force but without the use of balloons on the distal catheter tip. These flow-directed catheters have the advantage of being quite fast in that they are able to access remote portions of the body very quickly. They carry the obvious limitation that the catheter distal tip can only go where the blood flow is the highest. Furthermore, the catheters often are limited in the size of the "load" carried to the selected site. Said another way, balloon-less flow-directed catheters may be a marginal choice if a larger embolic coil or large diameter particle is to be delivered to the selected site.
In comparison to flow-directed catheters, over-the-wire catheters having variable stiffness (although quite strong and able to deliver embolic coils and large diameter particles through their large lumen) are comparatively quite slow in time of access. Friction with the interior of the guide catheter or the vessel path considerably slows the procedure time. The time needed to push the catheter over the guidewire is often lengthy simply because of friction with the guidewire. Over-the-wire catheters have advantages in that they can be directed to portions of the vasculature inaccessible to flow-directed catheters and they are compatible with a much broader selection of embolic devices. Lowering the resistance of the over-the-wire catheter to improve its interior or exterior lubricity and thereby, to allow improved access time to remote body sites, forms a further aspect of this invention.
This invention is, generically, a method for coating the interior of a catheter. These catheters typically have portions of differing flexibility and, so, are suitable for the delivery of diagnostic, therapeutic, or vaso-occlusive agents or devices to potentially remote portions of the vascular system or other systems of open lumen within the body. A thin coating of a lubricious polymer is applied at least to the interior of the catheter and optionally to the outside of the catheter. The preferred coating is quite slippery and is very durable.
This method of coating the interior of catheters with lubricious hydrophilic polymers involves the choice of specific uv-light transmissible polymeric tubing and desirably involves the use of particular method steps in which the lubricious polymeric precursors are carefully applied to the polymeric catheter substrates, any carrier solvent removed, and the precursors cured in situ by application of uv radiation to the exterior of the catheter.
There are a variety of prior art documents showing the use of hydrophilic polymeric coatings on the surfaces of catheter devices.
Typical of devices having such coatings are those described in U.S. Pat. No. 3,556,874 to Shepherd et al.; and U.S. Pat. No. 3,861,396 to Vaillancourt, et al.; and U.S. Pat. No. 4,417,892 to Meisch; and U.S. Pat. No. 4,876,126 to Takemura, et al.; and U.S. Pat. No. 4,898,591 to Jang, et al.; and U.S. Pat. No. 4,994,047 to Walker et al.; and U.S. Pat. No. 5,300,032 to Hibbs, et al. None of these patents show the use of ultraviolet light for the curing of hydrophilic coatings on the interior of vascular catheters or catheter sections. Most of these documents show the cross-linking of the hydracoat polymers with irradiation or heat or through the use of cross-linking agents mixed with a polymer precursor.
other devices made up of tubing having lubricious surface, not necessarily bonded in situ, are found in the following: U.S. Pat. No. 5,047,045 to Arney, et al.; to U.S. Pat. No. 5,201,724 to Hukins, et al.; to U.S. Pat. No. 5,281,203 to Ressemann and in U.S. Pat. No. 5,336,168 to Kaplan, et al.
An interesting medical device--a carbon dioxide indicator used as a section of an endotracheal tube is shown in U.S. Pat. No. 5,124,129 to Riccitelli, et al. That device is a tube having a pH-sensitive dye suspended in a hydrophilic polymer matrix placed on the inside of an indicator tube or connector. When the pH-sensitive dye changes color due to the presence of CO.sub.2 in moisture in exhaled air, the color change is visible from outside of the device due to the fact that the walls of the device are made of a transparent polymer. Ultraviolet light is used to cross-link the polymers in the color-bearing matrix and render the resulting polymer insoluble in water.
None of these references show the use of uv-transparent, polymeric, flexible tubing so to allow the curing of a hydrophilic or lubricious covering on the interior of that tubing.