FIELD OF THE INVENTION
The present invention relates to a medical device apparatus and method for infusion therapy. More particularly, the present invention relates to a coaxial infusion catheter device and method for use in dissolving blood clots.
BACKGROUND OF THE INVENTION
Thrombosis, or blood clot formation, is the most common cause of hemodialysis access graft failure. Graft thrombosis usually results from venous flow obstruction, or stenosis. The location of the stenosis is most commonly found at the graft-vein anastomosis. A narrowing at this area causes a slow down or obstruction of blood flow resulting in the formation of the thrombus within the graft. Venous stenosis is present in over eighty-five percent of clotted grafts. The underlying venous anastamotic stenosis must be corrected in order to avoid recurrence of the thrombus. The venous stenosis is usually treated with balloon angioplasty after the graft has been cleared of the thrombus.
Treatment options for thrombosed grafts include surgical thrombectomy, graft replacement, or percutaneous endovascular thrombolysis. Percutaneous thrombolysis is the least invasive treatment option and has rapidly become the preferred method of treatment at most institutions. It can be accomplished using mechanical thrombectomy devices that macerate the clot or by using a thrombolytic agent to dissolve the clot. Mechanical thrombectomy devices are expensive and often require capital investment. Thrombolytic agents provide a less expensive treatment option.
Tissue plasminogen activators, also known as TPA, are one of the most commonly used thrombolytic agents for clearing dialysis grafts. The drug is introduced into the clotted graft via an infusion catheter or a needle. TPA has a high affinity and specificity for fibrin, a major component of blood clots. It acts upon the clot by binding to the surface and dissolving it by an enzymatic reaction. Time until clot dissolution is dependent on the length and size of the clot, the amount of drug delivered, and method used for drug delivery.
With the “lyse and wait” technique of thrombolysis, TPA or other thrombolytic agent such as urokinase or retaplase is delivered to the graft by a small gauge needle or an infusion catheter. Manual compression is applied to the graft anastomoses during drug administration to ensure targeted drug delivery is restricted to the graft. The procedure is performed without the aid of fluoroscopic guidance. The therapeutic action of the lytic agent typically takes at least one hour depending on the effective distribution of the lytic agent. After clot dissolution, the patient typically is brought into the angiographic suite for fluoroscopic imaging of the graft to identify and visualize residual venous stenosis. Angioplasty of the stenosed segment can then be performed.
SUMMARY OF THE INVENTION
The “lyse and wait” technique of graft clearance has several advantages over other treatment options. With “lyse and wait”, the overall procedure time is shortened, the AngioSuite time is minimized, the costs associated with expensive mechanical thrombolysis devices is eliminated and the success rate for clearance is relatively high. Despite these advantages, the traditional “lyse and wait” technique has several potential problems which prevent these advantages from being widely accepted in practice.
When a needle, catheter, or other end hole device is used, non-uniform distribution of the lytic agent across the clot occurs. Therapeutic drug delivery using an end hole device results in concentrated lytic action at the location in the graft where the tip is positioned and insufficient lytic action at locations distant from the tip. This non-uniform drug delivery can result in incomplete thrombus resolution, reduced flow rates, and potential clot migration downstream. In addition, the non-uniform drug delivery results in a longer clot dissolution time period, potentially several hours in duration. Accordingly, there exists a need to provide a uniform distribution of the lytic agent across the entire clot without the use of fluoroscopy.
Furthermore, when an end hole infusion catheter is used as the drug delivery device, the drug must be slowly infused to prevent concentrated jet action through the end hole. Not only does this jet action concentrate the lytic agent in a single location, but it also may cause clot fragmentation and subsequent migration. To avoid high pressure localized delivery and the potential complications, the drug is delivered using a slow infusion method which typically takes three to five minutes with adequate clot dissolution taking up to several hours. Accordingly, there exists a need for an infusion catheter assembly which can a deliver lytic agent quickly and uniformly across the clot without causing a potentially harmful jet action.
To retain the lysing agent within the graft when an end hole catheter or needle is used, the ends of the graft are radially compressed during the injection period. The infusion of the lytic agent through an end hole catheter or angiocath needle is administered slowly over a 3-5 minute period. Compression is required during this infusion time period to ensure that the concentrated drug bolus remains within the graft. Without compression, distribution of the drug to non-targeted areas outside the graft is possible. Providing a infusion catheter device which does not require manual compression during drug injection would allow physicians to quickly and efficiently administer the drug without the assistance of additional medical personnel.
To overcome the non-uniform distribution of the lytic agent, a standard infusion catheter is sometimes used. The catheter is designed with either side holes or slits located along a specified segment of the catheter shaft. The drug exits these side holes equally along the entire length of the clot. Injections using a side hole catheter can be accomplished in one bolus action in three to five seconds rather than over a five-minute period as with an end-hole catheter. Typical drug dwell time within the graft is much less than with an end hole catheter due to uniform and more complete distribution of lytic agent.
Although it provides uniform drug delivery, the infusion catheter technique requires the use of multiple components. In order to access the graft, a needle, guidewire and micropuncture sheath introducer with dilator are required. After the sheath/dilator is removed, an infusion catheter is inserted over the guidewire and into the graft. These additional components not only add to the cost of the device but also add time to the procedure.
In summary, there exists a need for a thrombolytic device that can be percutaneously placed in an outpatient procedural room setting without the use of fluoroscopic guidance. The insertion device should create a minimal puncture. In a preferred embodiment, the device should be able to go over a 0.018″ guidewire and provide uniform delivery of the thrombolytic agent without requiring manual compression of graft ends. The procedure should minimize catheter exchanges during a declotting procedure by using a micropuncture catheter as both an access device and an infusion device. The device should allow for the exchange to a 0.035″ guidewire and associated procedural components so as to eliminate the need for multiple dilation steps. In addition, the product should be simple to use and inexpensive to manufacture which further improves the business method aspects of the present invention.
Disclosed is an improved infusion catheter device and method for de-clotting procedures. Specifically, a medical device kit is disclosed comprised of components to access the graft, rapidly deliver the therapeutic agent in a uniform distribution pattern across the entire clot, or in a concentrated pattern, and to maintain graft access in preparation for stenosis treatment using angioplasty. By combining components needed for micro-access with a novel infusion catheter/dilator assembly, the procedure eliminates the need for exchange of catheters to accommodate the 0.035″ wire or other second guide wire which is larger than the first guide wire. By using a micropuncture catheter as both an access device and an infusion device, the present invention eliminates catheter exchanges during the graft-declotting portion of the procedure.
In a preferred embodiment, the system and apparatus is a kit comprised of a micropuncture needle and compatible guide wire and an infusion catheter/dilator assembly.
Initial access to the graft may be established using standard Seldinger technique. A small-gauge standard micropuncture needle, typically 21-gauge, is inserted into the graft. An 0.018″ guidewire is then inserted into the graft through the needle lumen and the needle is removed. The infusion catheter/dilator assembly is inserted into the graft over the guidewire. The size and configuration of the catheter/dilator assembly are designed for easy insertion over an 0.018″ guidewire without the need for a micro-access sheath/dilator component to pre-dilate the tract. Typically in the present invention the outer diameter of the catheter/dilator assembly is 5 French approximately 0.067 inches and the outer diameter of the internal dilator is 3 French approximately 0.040 inches.
Once the device is positioned within the graft, the lytic agent is infused into the outer catheter using a standard syringe. The drug is preferably delivered through a side port in the catheter in a single bolus. Under low, steady pressure, the fluid advances into the annular space formed between the dilator and catheter. Occlusion of the catheter end hole by the dilator causes the drug to exit from the slits in the wall of the catheter into the clot mass. The drug will not exit from the end hole of the catheter because it is completely occluded by the dilator.
Only a small amount of drug is required because of the efficient delivery distribution. In addition, there is no need to reposition the catheter to ensure drug application to all segments of the clot. Because the side slits are used for drug delivery rather than the catheter end hole, drug delivery is rapid and uniform with no end hole “jet action”. Accordingly, there is no need to apply manual compression to the graft anastomoses during drug delivery to ensure uniform and localized drug distribution.
The present invention includes marking bands that show the position and length of the infusion section or region with the slits or small openings for distributing the lysing agent. These slits allow drug injection at a much faster rate. Typically, 5-10 cc of lytic agent can be delivered to the clot within 3-5 seconds. Because of the rapid and efficient distribution of the lytic agent, time to clot dissolution is decreased. Typically, only 20 to 45 minutes is necessary to declot the graft. Therefore, the efficiency and capacity of the whole clinic is improved because more patients can be treated in a shorter period of time within the outpatient area. Procedural time requiring use of the more expensive angio and/or fluoroscopy suites is limited to the angioplasty procedure.
Once the drug is delivered, the dilator is removed and the catheter is capped off using a standard closed connector type component. When ready for the angioplasty procedure, an 0.035″ guidewire or other suitable device can be inserted into the graft through the lumen of the infusion catheter component. An additional catheter exchange is not required because the infusion catheter component will accommodate the larger guidewire size. The infusion catheter component can then be removed leaving the 0.035″ guidewire in place to maintain site access. Angioplasty can then be performed using the already placed guidewire. Re-establishing access to the graft and use of a separate dilator is not required.
RELATED PRIOR ART
Micro access sets have been available for years and are considered public domain material. Thrombolysis as a therapy for vascular graft clearance has been taught since the late-1970s. Several infusion catheter designs have been patented. These designs focus on the uniform distribution of the therapeutic agent across the entire clot surface.
U.S. Pat. No. 5,425,723, Wang covers an infusion catheter with an infusion segment at its distal end. The device includes an inner and outer tubular body. The inner tubular body is spaced apart from the outer tube to provide an annular passageway for the delivery of fluid. The design provides for a uniform average flow rate of therapeutic fluid along the length of the infusion segment by the positioning of fluid exit holes on both the inner and outer tubes.
Fluid is introduced to the central lumen of the inner catheter. The therapeutic fluid flows distally and also out the inner catheter exit holes into the annular space between the inner and outer catheter. From the annular space, the fluid flows through the outer catheter exit holes and into the vessel. This indirect flow path counterbalances the decreasing pressure gradient at the distal segment of the catheter, providing a more even drug delivery.
Although an annular space exists for fluid flow between the inner and outer catheter components, the device disclosed by Wang differs significantly from the device of the present invention. The Wang catheter design requires the introduction of fluid into the inner catheter lumen and the fluid only indirectly flows into the annular space. In addition, the inner catheter does not perform a dilation function nor does it occlude the end hole of the outer catheter. The inner catheter cannot be removed to allow the introduction of a larger guidewire.
U.S. Pat. 5,800,408 Strauss, et al., covers an improvement on the Wang '723 concept of an infusion catheter. Like Wang's patent, the device includes an inner and outer tubular body with annular passageway between the two for fluid delivery. Instead of having a series of equally spaced exit holes on the inner catheter, Strauss et al., provides a distal and proximal set of exit holes on the inner catheter. This configuration forces fluid to flow distally in the annular space from the proximal holes and proximally from the distal holes. This flow configuration provides enhanced uniform distribution patterns. Strauss et al., also discloses a proximal hub mechanism for adjusting the flow path from one lumen to another.
Again, the concept outlined in the patent differs significantly from the concept of the present invention. The flow path adjustment mechanism can be used to divert flow completely to the annular passageway between the two catheter tubes. Strauss et al., teaches this flow pattern as a way of concentrating fluid delivery proximally rather than for achieving equal flow distribution. Like the Wang disclosure, the inner catheter does not perform a dilation function nor does it occlude the end hole of the outer catheter. The inner catheter cannot be removed to allow the introduction of a larger guidewire.
U.S. Pat. No. 5,250,034 Appling, et al., covers a single lumen infusion catheter for introducing therapeutic agents into the body. The distal segment of the catheter includes pressure responsive valves that provide for uniform fluid distribution. Appling et al., teaches the use of this catheter design for high-pressure injection at relatively high velocities. An occluding ball wire occludes the catheter end hole.
While the patent does include the concept of pressure responsive slits for uniform drug delivery, it uses an occluding ball and does not disclose the use of dilator insertion technique. In addition, Appling does not teach the combination of a micro-puncture access set with an infusion catheter specifically for use in outpatient pre-angioplasty graft de-clotting procedures.
U.S. Pat. No. 5,021,044, Sharkawy covers a multi-lumen catheter for delivery of thrombolytic agents to a blood vessel. The catheter has a first inner lumen for receiving a guidewire, and at least one additional lumen for the delivery of drugs. The coaxial catheter design includes an annular space for the fluid path between the inner and outer catheter tubes. A side-arm port is used to direct drug delivery into the catheter through the annular space between the two catheter tubes. Flow passageways are provided on the distal portion of the outer catheter. These passageways increase in cross-sectional area in a distal direction. The difference in cross-sectional areas provides for uniform fluid delivery.
Although Sharkawy teaches a coaxial catheter to direct the drug flow uniformly through side holes in the catheter, the claims focus on maintaining a desired flow pattern to the target site through the use of non-uniform side holes. He does not teach using the inner catheter for dilation nor does he disclose use of the inner catheter to provide an end hole occluding function. The inner catheter cannot be removed to accommodate introduction of a larger guidewire. There is no discussion of micro access or of specific teachings for dialysis graft de-clotting.
U.S. Pat. No. 6,245,045 Stratienko covers a vascular interventional device for introduction over a guidewire with an end hole and side holes for fluid infusion. The catheter hub is designed to accept another device through its lumen (a dilator) and to accept fluid through a side port. The device includes a dilator for insertion into the device which is dimensioned such that it will fit over a guidewire and within the lumen of the catheter.
There are several key differences between this patent and the present invention. The dilator and sheath components of the '045 invention fit snugly together. This fit does not provide sufficient annular space between the components for infusion of fluid. The coaxial lumen is simply too small for infusions. Before a fluid can be introduced, the dilator must be withdrawn from the sheath and another interventional device inserted. In addition, Stratienko's device includes a standard hemostasis sheath. Hemostasis sheaths are intended to accommodate large interventional devices. The micropuncture set design of the present invention on the other hand is intended to minimize the access puncture size. The micro access components, unlike the hemostasis sheath, allow access with minimal trauma and provide a gradual transition path for larger devices.