Method and Apparatus for Removal of Plaque From Blood Vessels

At the present time it is known that the accumulation of plaque in blood vessels may, under certain circumstances, present a health hazard to patients. For example, the accumulation of plaque may result in lowering the blood pressure to peripheral regions of the body. Additionally, accumulation of plaque in blood vessels associated with the heart may result in increased strain on the heart muscles and may eventually lead to heart failure either due to such strain or to further closure of the blood vessel by the plaque.

It is possible, in many cases, to remove the plaque by an operation in which the blood vessel in which the plaque is accumulated is partially removed by the surgeon. Such operations, particularly when the blood vessels are associated with the heart, may be both costly and present a health risk, especially if the patient is elderly or otherwise in ill health.

It is an objective of the present invention to provide a device and method for the removal of plaque accumulation in blood vessels without the necessity of operating on the patient by removal of the blood vessel.

It is a further objective of the present invention that the method and device present relatively less of a hazard to the health of the patient as compared with present operating procedures.

It is a further objective of the present invention that the method and device may be used a repeated number of times without presenting an additional health hazard to the patient.

It is a feature of the present invention to provide a device and method for dissolving the plaque which may accumulate in the blood vessels of the patient. The plaque is removed by means of heat which is produced from a high-energy laser source, preferably a gas laser operating in the 20-50 watt range. The heat energy from the laser beam is conducted to the plaque by means of a flexible elongated tube. The internal surface of the tube is highly reflective and is preferably a mirror surface of deposited aluminum or silver. The reflective surface is formed as an internal surface of a flexible plastic resin tube. The tube is prevented from kinking by an elongated helical spring wound about its external surface. Preferably the spring, in turn, is covered by a coating of a suitable plastic resin. In one embodiment the internal mirror surface is formed by winding an elongated flat ribbon (tape) about a mandrel with the inside surface of the tape being the mirror surface. The tape is a flexible plastic resin film. An elongated helical spring is wound about the tape and covered by a liquid plastic resin which, after it dries, forms a unified tubular structure.

In another embodiment the mirror surface is formed by a tape which is overlapped with its overlapping edges being parallel to the axis of the tube. As in the prior embodiment, the mirrored material is covered with a spring which, in turn, is covered with a suitable plastic resin.

The elongated tube is inserted through a vein or artery during the operative procedure until it reaches the plaque accumulation. The plaque accumulation may be seen, using X-ray technology, as it is absorbent to dye. When the tube, which is also easily seen in an X-ray, is positioned next to the plaque, the gas laser is fired. The heat from the gas laser is conducted along the length of the tube and reacts with the plaque, causing its disintegration.

Other objectives and features of the present invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a block schematic diagram illustrating the system of the present invention;

FIG. 2 is a perspective view illustrating the construction of the first embodiment of the present invention, in which a tape is wound about a mandrel;

FIG. 3 is a cross-sectional view taken along the line A--A of FIG. 2 and is enlarged to show the various layers of the tube after construction;

FIG. 4 is a perspective view showing the second embodiment of the present invention;

FIG. 5 is an enlarged cross-sectional view taken along the lines B--B of FIG. 3; and

FIG. 6 is a perspective view, and FIG. 6B is a front view, illustrating the third embodiment of the present invention, without its outer covering.

As shown in FIG. 1, the present invention seeks to disintegrate plaque, which has accumulated in a blood vessel, using heat. The heat is supplied from a suitable laser 10 (light amplification by stimulated emission of radiation). Preferably the laser 10 is a gas laser whose output is in the range of 20-50 watts of power. A suitable laser device would operate in the infrared radiation band (10.sup.14 to 10.sup.12 Hz). The laser 10 is provided with a suitable control 11 so that its on-off time may be accurately controlled by the surgeon during the operation. The laser 10 produces a coherent beam of light which is conducted by the tube 12 to the tube 13. The tube 12 and 13 may be of the same material, size and construction, the only difference being that the tube 13 is sterile as it is intended to be used in blood vessels of the patient.

During the operation the tube 13 is inserted through the blood vessel of the patient, for example, through the femoral vein and iliac vein, to the point of accumulation of the plaque which may be visualized by means of X-ray. When the end 15 of the tube 13 has reached the plaque, the laser is turned on until the plaque is disintegrated.

The tube 13 to which the present invention is particularly directed is a hollow tubular member having an internal light reflective surface, and is preferably round, in cross-section, in external and internal diameters. The light reflective surface is preferably formed by vacuum deposition (vacuum sputter) of a suitable material, preferably aluminum or silver, on a plastic resin film which is preferably in the form of a tape. The tape may be polytetrafluoroethylene (Teflon, TM of DuPont) or polyethylene. The tape, one side of which after such vacuum deposition has a mirror-like surface, is used to form the tube 13.

In the embodiment illustrated in FIGS. 2 and 3, the tape 20 is wound about a mandrel 21 in an overlapping helix. The tape is arranged so that its internal mirror surface 23 is against the outer surface of the mandrel. The tape forms a complete internal surface for the final tube 13. Although there is a slight loss of conductive light to the edges of the tab, such loss is relatively insignificant because of the short length between the laser and the plaque. The outer surface of the tape 26 is covered by an elongated helical spring 27. The spring may be either a metal spring made of metal which is compatible with the body, or of a plastic spring material. The spring 27 is covered by a coating 28 of a plastic resin which is compatible with the body, for example, polytetrafluoroethylene (TM of DuPont) or polyester plastic from xylene (Mylar, TM of Dow). The outer covering may be formed by heat extrusion over the coil or by other coating techniques. It is not necessary that the plastic be heatable to the extent necessary for sterilization as it is intended that the tube 13 is sufficiently inexpensive so that it could be disposed of after each operation rather than re-used.

In another embodiment, shown in FIGS. 4 and 5, the tape 30, which is the same type of tape as in the prior embodiment, is formed about a mandrel 31 in an extrusion. In this case, however, the tape is folded over itself so that its folded-over internal edge 32 is parallel with imaginary axis 33 of the tube. As in the prior embodiment the external surface of the tape is covered by an elongated helical spring 34. The spring, in turn, is covered by a plastic resin material 35 which is compatible with the body.

In both embodiments the internal surface of the tube is highly reflective at the frequency of the laser. It has been estimated that the loss along the tube may be only 10 or 40%, even though the tube is completely bent in a "U" and may extend for 3 or 4 feet. The tube is flexible so that it may be bent and follow the curves of the patient's blood vessels. At the same time it is sufficiently stiff so that the surgeon may insert it and it will, like other types of surgical catheters, follow the blood vessel.

Variations may be made in the present invention within the scope of the subjoined claims. For example, the laser device may be positioned directly at the entrance of the tube 13 rather than having its laser beam conducted to the tube 13 by the prior tube 12.

The mandrel in all embodiments is removed after the tube is formed. For example it may, if coated with a lubricant, be pulled from within the tube. Alternatively, it may be formed of a material which may be dissolved by a liquid solvent or it may be of a low-heat material, such as wax, and may be removed by heating.

Another variation is that the elongated helical spring may be replaced by a tandem series of rings. The rings, like the spring, prevents kinking of the tube. The rings are preferably evenly spaced along the outer wall of the tape and covered by a plastic resin having a smooth outer wall. When the tube is straight, i.e., its axis is a straight line, the plane of each ring is perpendicular to the axis.

As shown in FIGS. 6A and 6B the rings 40 may be formed with loops 41a-41d. The loops are on opposite sides of the ring, i.e., they are spaced 90.degree. apart and extend outwardly from the center of the ring. A plurality of wires 42a-42d, for example, 3 to 8, in the illustrated case four wires, are strung along the tube (only wires 41a, 41b are shown in FIG. 6A). The wires 42a-42d are used to control the direction of movement of the head (internal orifice) of the tube. The wires 42a-42d are fastened to the outermost ring 43, which may be enlarged for easier manipulation, and to the innermost ring 44 at the inner orifice of the tube. When the operator cants ring 43 (cants it relative to the axis) it pulls one or two of the wires and cants the innermost ring 44 in the same direction as the cant of the outermost ring 43. The canting of the innermost ring 44 acts to curve the tube so that it is guided by the operator through the body vessel, for example, through a vein. The wires are guided by, and are not fastened to, the loops 41a-41d. Each wire may be encased within a plastic tube within which it is freely slidable. The wires are covered by a plastic resin covering having a smooth outer wall, but the covering does not bind the wires, but rather permits their movement. Alternatively, instead of individual rings, a helical spring having loops may be used around the tape.