This invention pertains to catheters for injecting viscous fluid into the body, and particularly to catheters that deliver viscous embolization agents into the vasculature.
Catheters have been used for decades to infuse fluids into the blood stream. For the most part, the infused fluids disperse in the blood to effectuate treatment of the patient.
The assignee of the present invention is a developer of bio-compatible agents that are particularly useful for embolization of diseased (e.g. aneurysmal) sites in the vasculature of a patient. U.S. Pat. No. 5,851,508, issued Dec. 22, 1998, describes various embolization agents. The disclosure of this U.S. patent is incorporated herein by reference. These embolization agents are typically insoluble in blood and are highly viscous to enable delivery to a particular situs in the vasculature without dispersion.
Delivery catheters used for dispensing embolization agents have been made sturdy enough to deliver the embolization agents to various parts of the vascular system. However, such catheters are often too large in diameter to effectuate treatment in the distal most reaches of the vasculature.
The diagnosis and treatment of neurovasculature disease can be of the utmost importance because neurovasculature disease (e.g. aneurysmal disease) could devastate the patient. Unfortunately, the vessels of the distal reaches of the neurovasculature are tortuous, having diameters of 3 mm, or less, and having bends exceeding 90 degrees. Tortuous vessels are difficult to reach with full-sized delivery catheters.
The amount of pressure required to dispense a viscous fluid from a small diameter tube is much greater than the pressure required to dispense the same fluid through a larger diameter tube. Accordingly, the smaller the delivery catheter, the higher the pressure required to deliver the viscous fluid.
Pressure experienced by a viscous fluid delivery catheter is normally greatest at the proximal end. The pressure decrease towards the distal end, approaching zero at the distal most tip. In testing, standard luer fittings (e.g. ISO 594-1 standard luer fittings) may fail when supplied with pressures exceeding 500 psi. Typically, a leak between the luer fitting and the catheter denotes a failure. Further, standard syringes may fail when used for pressing highly viscous fluid through catheters having relatively small diameters.
What is desired is a viscous fluid delivery system that can deliver viscous fluids to the distal reaches of the vasculature, including the neurovasculature. What is also desired is a micro-catheter that can withstand high pressures to deliver viscous fluids.
A catheter for delivering viscous fluid into the vasculature of a patient includes a catheter body having a proximal end and a distal end, a reinforcing member surrounding at least a portion of the proximal end, and a compression fitting surrounding the reinforcing member for holding the proximal end of the catheter body.
The reinforcing member prevents radial compression and/or expansion of the proximal end of the catheter body, thus enabling the use of a compression fitting to hold the proximal end. The reinforcing member is tube-shaped and is either inserted within the proximal end, surrounds the proximal end, or both.
According to one aspect of the invention, the reinforcing member is integrated in the proximal end of the catheter body to resist radial deformation of the catheter body.
According to one aspect of the invention, the reinforcing member includes a tube that fully surrounds the proximal end. The tube is rigid, being fabricated from a tube of stainless steel less than 0.5xe2x80x3 long that bonds to the proximal end.
Preferably, the compression fitting threads into a luer fitting and thus connects the luer fitting and the proximal end in fluid communication to enable viscous fluid to be delivered via the luer fitting and through the distal end of the catheter.
A sheath covers the reinforcing member. The sheath is compressible to enable the compression fitting to squeeze the sheath and thereby grip the reinforcing tube. Preferably, the sheath is fabricated of like material as the proximal end of the catheter body and is preferably over-molded around the stainless steel tube of the reinforcing member. Accordingly, the sheath integrates the reinforcing member in the catheter body.
The catheter includes a luer fitting with threaded connectors. The compression fitting threadibly attaches the proximal end of the catheter body to the luer fitting.
According to one aspect of the invention, the compression fitting includes a locknut having a threaded outer surface and an inner surface. The inner surface defines an opening for circumscribing the reinforcing member. The outer surface of the locknut has threads. When the locknut threads into a luer fitting, for example, the inner surface presses against the proximal end and the reinforcing member of the proximal end of the catheter body. The reinforcing member thus prevents significant deformation such as a significant reduction of the inner diameter of the proximal end by the locknut.
The luer fitting includes a strain relief element that covers the compression fitting and a portion of the proximal end to inhibit radial deformation of the proximal end when a viscous fluid is delivered by the catheter. Preferably, the strain relief element attaches to the compression fitting.
Many ways of attaching the strain relief element to the catheter are possible. According to one aspect of the invention, the strain relief element attaches directly to the luer fitting. In a further aspect, the strain relief element attaches to both the luer fitting and to the compression fitting. According to another aspect of the invention, the strain relief element bonds to the compression fitting. According to another aspect of the invention, the strain relief element and the compression fitting press-fit. According to yet another aspect of the invention, the compression fitting has an annular recess that holds the strain relief element. According to still another aspect of the invention, the strain relief element bonds to both the compression fitting and to the proximal end of the catheter body.
The strain relief element tapers from the luer fitting towards the catheter body to eliminate the possibility of kinking the catheter body during normal use. The taper may assume any of a variety of configurations. Preferably, however, the taper extends between 1xe2x80x3-3xe2x80x3, and more preferably, the taper extends about 1.5xe2x80x3.
A system in accordance with the present invention includes the catheter and a high pressure device for delivering viscous fluid to the catheter. The high pressure device includes a syringe having a blunt needle. The needle includes a removable barb press-fit on the blunt needle. The barb is configured for piercing a vial holding viscous fluid to enable the syringe to draw the viscous fluid from the vial. The barb slides off of the needle when the needle is removed from the vial.
A method of filling a syringe with viscous fluid in accordance with the present invention includes providing a syringe having a needle and a vial of viscous fluid, press fitting a removable barb on the blunt needle, piercing the vial with the barb, drawing viscous fluid into the syringe from the vial, and removing the needle from the vial and thereby causing barb to slide off of the needle so that the barb remains in the vial. Another step in accordance with this method includes inserting the needle into a catheter and delivering the viscous fluid to the neurovasculature of a patient via the catheter.
The dimensions of the catheter body are preferably adapted for accessing the distal and tortuous reaches of the neurovasculature. Accordingly, the distal end has an outside diameter of 0.040xe2x80x3 or less to facilitate insertion of the catheter into tortuous regions of the vasculature. More preferably, the distal end has an outside diameter of less than 0.029xe2x80x3.
The distal end further includes a delivery lumen with lumen walls. The lumen walls being at least 0.0012xe2x80x3 thick to withstand pressures associated with the delivery of a viscous fluid. The proximal end of the catheter body being configured for attachment to a luer fitting and for withstanding pressures exceeding 2000 psi. Also, the syringe, the luer fitting and medial portions of the catheter body are also configured for withstanding pressures of 2000 psi or more.
The syringe attaches to the luer fitting with a syringe locknut. The syringe needle inserts into the syringe locknut and the syringe locknut to holds the needle when the syringe locknut threads into the luer fitting.
According to one aspect of the luer fitting, the luer fitting is bifurcated, having a three threaded portions to simultaneously receive and attach two syringes to two of the threaded portions, and to attach the compression fitting and the catheter body to the remaining threaded portion, respectively.