Drug Infusion Catheter and Method

The field of this invention relates to blood vessel treatment by drug infusion and other techniques using catheters.

For treatment of various diseases in the body, catheters and cannulas are widely used. Using cannulas, a drug can be injected into the tissue whereby the drug is placed in the tissue to be absorbed by diffusion into the tissue cells and subsequently distributed throughout the body using blood as a carrier. Often it is necessary to infuse a drug or substance into the vascular system of the body to treat a specific area of the vascular system. For example, after balloon angioplasty, certain drugs are infused to reduce the risk of re-stenosis of the lesion. These drugs are placed around the lesion to be absorbed by diffusion to the tissue around the lesion. Due to the constant flow of blood in the vessel, the drug infused often gets washed away and only a small amount of the drug is absorbed by the tissue.

In the past, many inventors have tried to solve this problem by providing different solutions. One such method is to use two balloons to occlude the vessel on either side of the lesion (the area of interest) and provide a pool of the drug at the lesion to be absorbed by the tissue by diffusion. This method has the drawback that during balloon inflation, the blood supply is stopped and causes ischemic manifestation to the organ that is supplied by the blood vessel that is to be treated.

Several other devices have also been developed where the drug is infused under pressure to the issue, using balloons.

In another invention, the balloon has small microscopic holes and the balloon is inflated using the drug. The drug is then injected to the tissue through the holes after inflating the balloon.

Others include double-wall balloon where the inner balloon is inflated using an inflation medium while the drug is infused through microscopic holes that are in between in the outer and inner balloon walls.

Various such devices are described in the article by Dr. Steve Bailey in THE JOURNAL OF SEMINARS IN INTERVENTION CARDIOLOGY--LOCAL DRUG DELIVERY, Vol. 1, Issue 1, March 1996, pp. 17-23; by Christine Enger on pp. 27-33; by Mun Hong, pp. 34-35; by Aaron Kaplan, pp. 36-38; by Edoardo Camerzind, pp. 39-40; and by Peter Barath, p. 43.

In most or all of the above cases, a balloon is involved in the delivery of the drug. As a balloon is used as the tool, it invariably causes the occlusion of the artery, which causes ischemic conditions in the organ that is supplied by the blood vessel. This means that the balloon must be deflated quickly after inflation to cause injection of the drug. In all these instances, the drug absorption takes place by diffusion, which is a very slow process.

Another method developed is the needle catheter. The needle catheter is a device having four needles that can be advanced through a tube to protrude outwards to inject the drug into the wall of the blood vessel. These catheters are often bulky and, due to the fact that the needles are metal and stiff, cause damage to the blood vessel wall during the procedure.

A method and apparatus of delivery of a drug (or substance) is disclosed which involves (1) injecting a drug into the tissue of the blood vessel; (2) maintaining the delivery system as symmetrical as possible in tortuous blood vessels, and (3) providing a preferably constant flow of blood during the drug treatment.

FIG. 1 is a schematic depiction of the drug infusion apparatus showing a microtubular brush which can be retracted into a sleeve for advancement and retrieval.

FIG. 2 is a sectional view along lines 2--2 of FIG. 1.

FIG. 3 is a detail of the distal end of the apparatus shown in FIG. 1.

FIG. 4 shows the drug infusion catheter retracted into the sheath.

FIG. 5 shows the drug infusion catheter advanced into the blood vessel.

FIG. 6 shows the sheath having a protective cover to protect the patient from radiation.

FIG. 7 shows the drug infusion catheter having a radiation source mounted at the center of the brush apparatus.

FIG. 8 shows a cross-section of alternate design instead of bristles.

FIG. 9 shows an alternate design using rib structure instead of bristles.

The objective of this invention to provide a method of delivery of the drug (or substance) by (1) injecting it into the tissue of the blood vessel; (2) to maintain the system as symmetrical as possible in tortuous blood vessels, and (3) to provide the constant flow of blood during the drug treatment.

This is achieved by a device similar to the one in FIG. 1. The device (catheter) is made from two coaxial tubes, 1 and 2. In the proximal end, the tubes are connected to a plastic adapter 3. The catheter can be advanced to the vascular system over a guidewire 4. At the very distal end, the coaxial tube is fitted with a molded plastic brush-like apparatus 5. The plastic brush-like apparatus has bristles that are hollow. The proximal end of the brush apparatus is attached to the end 6 of the coaxial tube 2, and the distal end of the brush apparatus 5 is attached to the coaxial tube 1 at end 7. A drug or substance can be injected from a side port 8 in the proximal adapter 3. Injection can be high pressure up to 600-700 psi. Depending on the size of the passage in the bristle and the backpressure applied, the drug will be injected at a high velocity, and at a velocity high enough, the drug will be injected to the tissue wall. Once the drug is injected to the tissue wall, it will be transported by diffusion.

The bristle apparatus 5 can be made in different diameters, such as 2.0 mm, 2.5 mm, 4.0 mm, so as to fit the blood vessel under treatment. The bristle apparatus can be provided with 4, 8, or 12 bristles in a given row, as shown in FIG. 2. Along the length of the bristle apparatus, 10-20 rows of bristles can also be provided. The number of rows and number of hollow bristles in a row are for example only. Each row is in a particular transverse plane; however, a spiral distribution pattern or a random pattern of individual bristles can also be used. The bristles are preferably made from soft plastics so that when the catheter is advanced out of sheath 10, as shown by comparing FIGS. 4 and 5, the tips of the bristles do not damage the artery wall. For this purpose, nylon, polyethylene, high-density polyethylene (HDPE), polyurethane, silicone, polyvinyl chloride (PVC), or acrylonitrile butadiene styrene (ABS) are suitable polymer materials. The bristle structure can be a flexible tube that is bent under a sheath or a multi-component tube with telescoping segments that extends radially upon fluid pressure applied thereto.

Inasmuch as there is no balloon involved in this design, blood would continue to flow without hindrance distal to the area treated and would not cause any problems of ischemia, which is caused when the flow of blood is restricted by the use of a balloon device. Since the bristles are soft, they will not cause mechanical damage to the blood vessel wall as is the case with balloons having needle structures or catheters with rigid metallic needles.

The bristles 5 in the present invention are tapered to a point, providing flexibility as well as a point that will help to "fix" the tip of the needle to the inner surface of the blood vessel during drug infusion.

FIG. 4 shows a sheath 10 in which the catheter assembly 11 is kept while it is advanced into the vascular system to prevent any damage. The catheter assembly 11 can be advanced over the guidewire 4 into the lesion location for injection of the drugs. After injection of the drugs, the catheter 11 can be retracted into the sheath 10 by moving the sheath 10 forward while holding the catheter 11, and the entire assembly 11 can be withdrawn from the vascular system without damage to the inner lining of the blood vessel.

In an alternate design, instead of separate and discrete bristles, rows of ribs 14, 4-10 in number, can be provided extending radially in general alignment such as along the length of the catheter as shown in FIG. 9 or a spiral pattern. The ribs 14 are spaced apart to allow blood or other fluid to flow through the vessel without significant restriction as drugs are delivered to the vessel wall through insert tubes 17. These ribs have small diameter channels 15 molded in so that the drug can be infused from the annular space between the two tubes to the blood vessel wall. Just as in the previous disclosure, these ribs are made of very soft plastic or rubber material to prevent trauma to the inner lining of the blood vessel. They are retained in a flexed position by a removable retaining sleeve. When the sleeve is retracted, the resiliency of the ribs aids in their expansion. Alternatively, the ribs 14 can be sufficiently flexible so that they don't need to be retained but they expand radially as passages 15 are pressurized. The concentric wall of the structure is made thin enough so that when the catheter is pressurized, the tube assembly would expand about 1-5 mm, enabling the ribs or bristles to touch the inner wall of the blood vessel. Without the pressure the ribs/bristles are somewhat restricted. At the end of the bristles/ribs, sharp metal tube(s) 17 can be molded in place to enhance the puncturing of the blood vessel in order to deliver the drug more effectively. The present design also allows blood to flow without hindrance during the drug infusion, thus maintaining proper functions of the organ diffused.

Another use for the present invention is to treat the lesion with radiation. In most instances, gamma or beta radiation is used to treat lesions to reduce the growth of cells (neointima) after balloon angioplasty. An apparatus, as in FIGS. 6 and 7, describes a means of providing radiation to a lesion. In this instance, the bristles 12 can be either hollow or solid. They are preferably bent at the end to produce a smooth surface and a footing. The radiation material is wound or placed on the inner tube. Preferably, a coil spring of thickness 0.004-0.006" can be used. The material of construction of the radiation material can be any material that absorbs radiation and emits radiation. A certain degree of radiopathy is preferred so that the radiation source is visible under fluoroscopy. When the radiation source is made into a flexible spring, the trackability of the catheter through the vascular system is enhanced. In this case also, the catheter is advanced to the lesion in the vascular system in a sheath. After placing the sheath proximal to the lesion, the catheter is advanced to expose the lesion to radiation. Once the radiation is completed, the catheter is pulled back into the sheath under the protective cover 13. The protective cover stops any radiation from affecting other parts of the body or the health professionals using radiation systems.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.