Self-centering mechanical medical device

#The present invention provides a medical device for use in vascular procedures. The device is particularly useful in the mechanical maceration of a thrombus or the like.

#It is well known that the presence of foreign solid matter within an individual's vascular system can have serious adverse effects on an individual's health, either directly or indirectly. Such solid matter most commonly takes either the form of a thrombus, i.e., gelatinous, free-floating matter within a vascular channel but not adhered to the channel itself, or atheroma, which is most commonly a buildup of plaque or the like on the wall of a vessel. A wide variety of techniques are known for removing or breaking down such matter within the vascular system. Some techniques, known as thrombolytic therapy, utilize pharmaceutical compounds, e.g., urokinase, or streptokinase, to help dissolve such foreign matter.

#Other techniques take a mechanical approach and attempt to dislodge the solid matter from the walls of the vascular system, if necessary, and then remove the solid matter from the vascular system by means of suction or the like. In dislodging plaque from vascular walls, an elongate wire with one or more scraping blades adjacent the distal end is rotated within the vascular channel. By moving the rotating blades axially into contact with the plaque, the blades will tend to dislodge it, permitting the dislodged particulate matter to be withdrawn from the vascular system by means of suction through a catheter or the like. A similar technique may also be used to break a relatively large thrombus into a number of smaller pieces which may then be extracted by aspiration.

#FIG. 1 is a perspective, partially broken away view of a medical device of the invention;

#FIG. 2 is a perspective view in partial cross section of a distal portion of the device of FIG. 1;

#FIG. 3A is a side view of the rotor housing of the device of FIG. 1;

#One preferred embodiment of a medical device of the invention is shown in FIGS. 1-4. This device generally includes an elongate, flexible shaft 10 carried within an elongate, generally tubular casing 20; a rotor 50 affixed to the shaft and carried within a rotor housing 70; and a drive means 100 operatively connected to the shaft for rotating the shaft.

#The shaft 10 is elongate and generally cylindrical in shape and has a distal end 12 and a proximal end 14 (FIG. 7). The shaft is sized to be threaded, along with the rest of the device of the invention, along a vascular path within a patient's vascular system. The shaft will commonly have an outer diameter of between about 0.25 and about 1.5 mm, with a range of about 0.35 to about 0.65 mm being preferred. The length of the shaft can be varied fairly widely, depending upon the general types of locations within a vascular system intended to be accessed with the device. As a general rule, the shaft is desirably between about 50 cm and about 150 cm long, with a range of about 80 cm to about 100 cm providing a device which is useful for a wide variety of applications.

#The shaft is desirably highly flexible so that it may be threaded through a patient's vascular system with ease. The shaft may be made of any of a wide variety of materials well known in the art, such as stainless steel. In one preferred embodiment, however, the shaft is formed of a shape memory alloy, such as a NiTi alloy. The use of such alloys in medical devices is known in the art and need not be discussed in great detail here. One important property of such alloys is that they exhibit superelasticity, i.e., they may be deflected to a much greater extent than most other metals, such as stainless steel before showing any permanent, plastic deformation. This property is explained in some detail in U.S. Pat. No. 4,926,860 (Stice, et al.), the teachings of which are incorporated herein by reference. In the present invention, this permits the shaft 10 to be guided along a tortuous vascular path without introducing a permanent "set" in the wire. Accordingly, when the shaft is guided to the desired location and rotated (as described below), its rotation will be centered almost exclusively about the axis of the shaft.