SUB-MICROCATHETER

Abstract: The present invention includes a sub-microcatheter that comprises a unitary, hollow, flexible main body having a distal end and a proximal end. A mandril is positionable within the sub-microcatheter main body at the proximal end. The mandril is moveable throughout the hollow main body.

Description: SUB-MICROCATHETER Background of the Invention The present invention relates to a sub-microcatheter and to a method for treating a blockage in a vessel caused by a thrombus. In an acute stroke, a blockage is formed within a vessel by a thrombus or a clot. In treating acute stroke, an objective is to remove the blockage caused by the thrombus as quickly as possible. In numerous clinical studies, it has been shown that if the blockage can be removed within the first six hours after a stroke, the chance for patient recovery with little or no permanent neurologic deficit is significantly improved. Many practitioners believe that a window of opportunity is limited to the first three hours following blockage. The thrombus is comprised of various blood components that can be dissolved or lysed with drugs. In conventional stroke therapy, these lytic drugs are given by systemic intravenous (IV) administration. Consequently, a drug is infused throughout the entire circulatory system. A more aggressive treatment is to deliver the lytic drugs directly to the thrombus utilizing a catheter. The catheter is positioned adjacent to the thrombus and the drug is infused directly onto the thrombus. The benefit is that the drug, in a much higher concentration, reaches the thrombus for improved effectiveness. One type of drug delivery system utilizes a microcatheter. Microcatheters that are intended for insertion into the vasculature of the brain rely upon the flexibility of polymeric material from which the microcatheters are fabricated for the characteristics of trackability and pushability. Trackability as used herein refers to a characteristic of a microcatheter to "track over" a guidewire to an intended treatment location. Microcatheters must exhibit superior trackability to traverse the tortuous anatomy in the brain. Pushability as defined herein refers to a characteristic of a microcatheter to transmit an axial pushing force from a proximal end of the catheter, which is the operator end, to a distal end of the microcatheter, the end of the catheter in the patient. Physicians expect that they can push the microcatheter effortlessly within the anatomy of a living being. Microcatheters are typically designed to enhance these characteristics with a particular polymer selection for the catheter body or a catheter shaft. Polymers may be blended or coextruded to provide a proper mix of flexibility and rigidity. A microcatheter shaft may vary in flexibility over its length, being more flexible and less rigid at a distal end of the microcatheter and less flexible .and more rigid at the proximal end of the micro catheter. This result may also be accomplished by varying the microcatheter shaft diameter and wall thickness. The Engelson patent, U.S. No. 4,739,768, issuing April 26, 1988, and Re- examination Certificate No. B14739768, issuing June 16, 1993, describes a catheter used in conjunction with a guidewire for treating a target tissue. The catheter includes an elongate tubular member with a proximal end and a distal end, the tubular member defining an inner lumen. The tubular member has a stiff proximal segment making up about 70% to 95% of the total length of the tubular member as well as a flexible distal segment that makes up the remaining 5% to 30% of the length of the tubular member. The proximal segment defines inner and outer coaxial tubes. A Samson et al. patent, U.S. No. 5,462,523, issuing October 31, 1995, describes a catheter for delivering drugs to regions of a human body accessible through systems of passage ways, such as blood vessels. The catheter includes a guidewire and a tubular elongate body. The elongate body includes a distal segment that is flexible thereby rendering the catheter trackable along the guidewire. The main body further includes a profusion tip with an opening permitting a perfusion of drugs at a particular site. The tip is made up of an inner stiffener which is somewhat porous and an outer profuser layer which controls fluid flow to a relatively low rate. Summary of the Invention The sub-microcatheter of the present invention includes a unitary, flexible main body defining a lumen having a distal end and a proximal end. A mandril is positionable within the sub-microcatheter and imparts to the main body flexibility and rigidity that is effective for optimizing trackability and steerability of the sub-microcatheter within vessels of a living being. The present invention also includes a method for delivering thrombolytic drugs to a thrombus. The method includes providing a sub-microcatheter that includes a unitary, flexible main body defining a lumen and having a distal end and a proximal end and a mandril positionable within the lumen and moveable throughout the lumen of the main body. The method also includes a step of transporting the sub-microcatheter to a thrombus site within a microcatheter and moving the sub-microcatheter-mandril as a unit within the microcatheter and placing adjacent the thrombus. The sub-microcatheter-mandril unit is then moved so that the sub-microcatheter is within the thrombus. The mandril is then removed from the sub-microcatheter in order to infuse drugs into the thrombus through the sub-microcatheter and through the micro-catheter. The present invention additionally includes a method for improving steerability and trackability of a sub-microcatheter. This method includes providing a sub-microcatheter that comprises a unitary, flexible main body that defines a lumen, the main body having a distal end and a proximal end. A mandril is positioned within the lumen of the main body at the proximal end and extends to the distal end. The mandril is moveable within the lumen in order to optimize pushability and trackability so as to advance the sub-microcatheter and the microcatheter to a treatment site. The present invention additionally includes a method for altering the flexibility of the sub-microcatheter by changing the diameter and flexibility of a mandril moveable within a lumen of the sub-microcatheter. As a consequence, sub-microcatheter flexibility is greater at the distal end for traversing tortuous blood vessels and is more rigid at the proximal end for operator control. Once the sub-microcatheter is properly positioned, the mandril is removable from the sub-microcatheter in order to allow for infusion of lytic drugs. Brief Description of the Drawings Figure 1 is a side view of one embodiment of the sub-microcatheter of the present invention. Figure 2 is a side view of the sub-microcatheter of the present invention positioned within a thrombus. Figure 3 is a side view of a mandril that is positionable within the sub- microcatheter. Figure 4a is a schematic view of a microcatheter position with respect to a thrombus. Figure 4b is a schematic view of the position of the sub-microcatheter with respect to a thrombus and the microcatheter. Detailed Description of Preferred Embodiments The sub-microcatheter of the present invention illustrated generally at 10 in Fig. 1 includes a flexible main body 12 defining a lumen 33 with a distal end 14 and a plurality of ports 18a, b, and c, positioned proximally to the distal end 14, the main body 12 further terminating in a proximal end 20 opposing the distal end 14. The sub-microcatheter 10 encloses a mandril 22 within the lumen 33. The mandril 22 shown in Fig. 3 includes a shaft 24 and a taper section 26 extending distally from the shaft 24. The sub-microcatheter main body 12 further includes marker bands 29 a and b, positioned adjacent each of the ports 18a and c. The marker bands 29a and b enable an individual, such as a physician, positioning the sub-microcatheter 10 to precisely position the main body 12 within a thrombus such as is shown in Fig. 4b. The position of the mandril 22 within the lumen 33 of the flexible main body 12 of the sub-microcatheter 10 permits the sub-microcatheter main body 12 to be constructed utilizing a single extrusion of a polymer. In one embodiment, the polymer is a high density polyethylene. In other embodiments, the sub- microcatheter main body 12 is made of a material such as polypropylene, ethylene vinyl acetate (EVA), nylon or polyimide. With these materials of construction, the main body 12 has a uniform flexibility and rigidity throughout its entire length. In a preferred embodiment, the main body 12 is extruded so that the diameter and wall thickness as well as the polymeric material of construction render the main body 12 highly flexible with very little rigidity. The mandril 22 which is preferably made of a metallic material such as Nitinol, super elastic Nitinol, stainless steel, or a cobalt chromium alloy such as Elgiloy manufactured by Elgiloy Corp. of Elgin, Illinois, imparts a reversible and variable rigidity and flexibility to the main body 12 of the sub-microcatheter 10. One typical composition of Elgiloy includes 40% cobalt, 20% chromium, 15% nickel, 7% molybdenum, 2% manganese, 0.15% carbon, 0.04% beryllium with the remaining weight percent being iron. Further information on Elgiloy is described in U. S. Patent No. 2,524,661, which is incorporated herein by reference. The mandril 22 also imparts to the main body 12 the variable flexibility and rigidity required to advance the sub-microcatheter 10 through a microcatheter and a blood vessel. In particular, the flexibility and rigidity optimizes steerability and pushability of the sub-microcatheter 10 through an anatomy of a living being. Once the sub-microcatheter 10 is in a proper treatment site position, within a thrombus such as is illustrated schematically in Figs. 2 and 4b, the mandril 22 is removed, leaving the highly flexible sub-microcatheter main body positioned within an artery or vein. Once positioned within the artery or vein, lytic drugs are delivered through the ports 18a-c. The lytic drugs act to disperse and dissolve a thrombus or blood clot. The sub-microcatheter 10 is also usable in a selective angiography procedure. The sub-microcatheter 10 of the present invention fits within a conventional microcatheter 50 as shown in Figure 2 and 4b. The microcatheter 50 provides to a physician a guide catheter that facilitates advancement and placement of the sub-microcatheter 10. The sub-microcatheter of the present invention 10 is advanced to the treatment site after the microcatheter is advanced to a position adjacent to the treatment site as shown in Fig. 4a. The microcatheter is advanced along a guidewire in a conventional manner. The sub-microcatheter 10 does not require a separate guidewire for positioning. Advancement of the sub-microcatheter 10 and the mandril 22 is accomplished by moving the metallic mandril 22 to the distal end 14 of the sub-microcatheter 10. The sub-microcatheter' s distal tip 14 is sealed shut so that the mandril 22 can transmit push forces through the sub- microcatheter 10 which is advanced to a treatment site as a single unit through the microcatheter 50. In one embodiment, the mandrel includes a blunt tip which is radiopaque for fluoroscopic guidance. In one embodiment, the mandril 22 is coated with a lubricious agent such as a silicone oil, a hydrogel or other hydrophilic coating in order to render the mandril 22 easier to manipulate. Similarly, the sub-microcatheter 10 is also, in one embodiment, coated with a lubricious coating such as silicone oil, hydrogel, or other hydrophilic coating. The coating preferably covers a distal section of about 20 centimeters of the submicrocatheter where the catheter is reduced in diameter to a range of 0.014 inches to 0.016 inches. Microcatheters tend not to be very steerable. As a consequence, torque transmission from a proximal end to a distal end of the microcatheter is either severely limited or non-existent. This lack of steerability and torque ability limits the microcatheter' s ability to access abrupt turns or branch vessels. Current microcatheters require the assistance of a guidewire to steer the microcatheter into position. The sub-microcatheter 10 of the present invention overcomes this significant problem by placement of the mandril 22 within the sub-microcatheter thereby rendering the sub-microcatheter steerable and pushable. It is contemplated that the submicrocatheter may be steered by use of a steerable guidewire in the submicrocatheter lumen in place of the mandrel. The steerable guidewire has a diameter of about 0.010 inches to 0.012 inches. The distal 5 centimeters of a submicrocatheter embodiment with a mandrel in the lumen has a flexibility that is equivalent to a 0.014 inch steerable guidewire. The sub-microcatheter 10 of the present invention is inserted after the conventional microcatheter accesses the artery and is positioned adjacent to the thrombus. The sub-microcatheter 10 is supported by the conventional microcatheter while the thrombus is being penetrated. After the submicrocatheter 10 is safely positioned within the thrombus, the mandril 22 is removed and infusion of drugs is begun as is shown in Fig. 2. As an adjunct to this treatment, lytic drugs may also be infused through the conventional microcatheter to provide for an increased volume of lytic drug at the thrombus. The mandril 22 extends beyond the proximal end of the submicrocatheter 10 so that the mandril 22 is gripable by a physician. The mandrel has a maximum diameter that is preferably about 0.012 inches, which is tapered over a distal length of 20 centimeters to 0.004 inches in diameter. One mandrel embodiment terminates in a blunt tip. For this embodiment, the blunt tip diameter is greater than the adjacent 0.004 inch tapered section and is preferably about 0.008 inches in diameter. Additionally, a Luer tapered fitting of the submicrocatheter 10 includes a pair of finger grip wings 25a and 25b as shown in Fig. 1 that enable a user, such as a physician to adequately grip the Luer tapered fitting and lock accessory devices such as hemostatic valves and infusion devices to the Luer tapered fitting. The lumen of the tapered fitting facilitates an effortless loading of the mandril 22 in the sub-microcatheter main body lumen. The mandril 22 is loaded and positioned within the lumen in a manner that permits the physician to rotate and torque the mandril 22 and to steer the distal tip 14 of the sub-microcatheter 10 without hindering pushability or steerability. Between the submicrocatheter and the mandrel is an annular space that is preferably about 0.002 inches to aid in pushability and also steerability by the mandrel. The submicrocatheter tip is steerable by rotating the mandrel within the catheter lumen. In particular, the mandrel is locked to the submicrocatheter at the proximal end with a Touhy-Borst fitting. The catheter assembly is rotated as a unit. The tip of the catheter is also deflected for steering by axially pushing on the mandrel against the closed distal tip. The holes 18a-c defined by the main body 12 are in one embodiment equally spaced around the main body 12 about 90° apart. The infusion holes 18 a-c are about 0.005 inches in diameter. The holes are smaller than the blunt tip of the mandrel in order to prevent the mandrel from exiting the submicrocatheter through the infusion hole. In one embodiment, marker bands are embedded in the catheter lumen adjacent to the infusion holes 18 a-c. The sub-microcatheter 10 is shaped so that the main body portion defining the holes 18a-c may be inserted directly into a thrombus 28 as shown in Figs. 2 and 4b. Once the main body 12 is inserted into the thrombus 28, drugs may be infused through the holes 18a-c. In one embodiment, the submicrocatheter 10 includes a pinhole 16 at the end of the submicrocatheter. In one embodiment, the main body 12 of the sub-microcatheter is made of a material such as high density polyethylene 12. The main body 12 has a wall thickness of about 0.002 inches. The submicrocatheter has a diameter, preferably, of about 0.018 inches or smaller. The lumen diameter defined by the main body is about 0.014 inches, minimum. It is understood, however, that the main body may be sized to have other dimensions. It is important that the diameter allows the sub-microcatheter 10 to easily navigate within a conventional microcatheter through a blood vessel. The main body 12 of the sub-microcatheter 10 is capable of safely penetrating the length of the thrombus creating a channel within the thrombus to infuse drug throughout the thrombus. This feature provides for greater surface contact of the drug with the thrombus and produces an open channel for blood flow that improves the effectiveness of the lytic process. Those skilled in the art will further appreciate that the present invention may be embodied in other specific forms without departing from the spirit or central attributes thereof. In that the foregoing description of the present invention discloses only exemplary embodiments thereof, it is to be understood that other variations are contemplated as being within the scope of the present invention. Accordingly, the present invention is not limited in the particular embodiments which have been described in detail therein. Rather, reference should be made to the appended claims as indicative of the scope and content of the present invention.

Claims: CLAIMS What is claimed is: 1. A sub-microcatheter, comprising: a unitary, flexible main body defining a lumen and having a distal end and a proximal end; and a mandril positionable in the sub-microcatheter main body at the proximal end and moveable along the lumen of the main body, the mandril imparting to the main body a flexibility and rigidity effective for optimizing trackability and steerability of the submicrocatheter within the vessel of a living being. 2. The sub-microcatheter of claim 1 wherein the distal end defines a pin hole. 3. The sub-microcatheter of claim 1 wherein the main body defines a plurality of ports positioned proximally to the distal end of the main body. 4. The sub-microcatheter of claim 1 wherein the mandril includes a tapered section. 5. The sub-microcatheter of claim 1 wherein the unitary, flexible main body is comprised of one or more of the materials polyethylene, polypropylene, ethylene vinyl acetate, nylon, or polyimide. 6. The sub-microcatheter of claim 1 wherein the mandril is comprised of one or more of Nitinol, super elastic Nitinol, stainless steel, or a cobalt chromium alloy. 7. The sub-microcatheter of claim 1 wherein the main body has a wall thickness of about 0.002 inches. 8. The sub-microcatheter of claim 1 wherein the main body has an inside diameter of about 0.014 inches, minimum. 9. The sub-microcatheter of claim 1 wherein the main body has an outside diameter within a range of about 0.018 to 0.028 inches. 10. A method for delivering thrombolytic drugs to a thrombus, comprising: providing a sub-microcatheter that comprises a unitary, flexible main body, defining a lumen, having a distal end and a proximal end and a mandril positionable in the sub-microcatheter at the proximal end and movable along the lumen of the main body, forming a unit; positioning the sub-microcatheter within a microcatheter placed adjacent the thrombus forming a second unit; moving the sub-microcatheter unit to a thrombus site so that the sub- microcatheter-microcatheter unit is proximal to the thrombus; advancing the sub-microcatheter within the microcatheter; positioning the sub-microcatheter within the thrombus; and removing the mandril in order to infuse drugs through the sub- microcatheter into the thrombus. 11. The method of claim 10 and further including infusing drugs through the microcatheter to provide an increased volume of lytic drug to the thrombus. 12. A method for improving steerability and trackability of a submicrocatheter, comprising: providing a sub-microcatheter that comprises a unitary, flexible main body defining a lumen having a distal end and a proximal end; positioning a mandril within the lumen of the main body of the sub- microcatheter at the proximal end; and moving the mandril within the main body in order to advance the submicrocatheter to a treatment site. 13. The method of claim 12 and further including positioning the submicrocatheter with the mandril within a microcatheter to form a sub- microcatheter-microcatheter unit. 14. The device of claim 1 wherein the sub-microcatheter is coated with a lubricious coating. 15. The sub-microcatheter of claim 1 wherein the mandril is coated with a lubricious coating.

Inventors: LEE JEFFREY A, LEE, JEFFREY, A.
Applicants: NEUROVASX INC, NEUROVASX, INC.
Application year: 1998
Main classification: A61M25
IPC codes: A61B17, A61M25