Patent Application
20050149083
The present invention relates to medical devices, more particularly, devices and methods for removing tissue from a body lumen, such as removal of atherosclerotic plaque from arteries, utilizing a rotational atherectomy device.
A terminal guide for a helically wound drive shaft for use in a rotational atherectomy device. The terminal guide is atraumatic to prevent perforation of the arterial wall or the embedding of the device into the arterial wall. The terminal guide may be pre-machined, cast, molded or formed in any manner that maintains the required dimensions and tolerances. The terminal guide may be fabricated from any biocompatible material and coated or formed with radiopaque material to more accurately position the rotational atherectomy device without going past the distal end of the pre-positioned guide wire.
An object and advantage of the present invention is to provide an atraumatic terminal guide for the drive shaft of a rotating atherectomy device.
Another object and advantage of the present invention is to provide an atraumatic terminal guide for a rotating atherectomy device that minimizes or eliminates the possibility that the device's drive shaft is advanced past the distal end of the pre-positioned guide wire.
Another object and advantage of the present invention is to provide an atraumatic terminal guide for a rotating atherectomy device that minimizes or eliminates the unwanted eccentric motion of the drive shaft distal end.
Yet another object and advantage of the present invention is to provide an atraumatic terminal guide for a rotating atherectomy device that reduces surface erosion of the guide wire as a consequence of unwanted eccentric motion of the drive shaft and frictional welding of the drive shaft to the guide wire, while increasing the useful life of both the drive shaft and the guide wire.
The foregoing objects and advantages of the invention will become apparent to those skilled in the art when the following detailed description of the invention is read in conjunction with the accompanying drawings and claims. Throughout the drawings, like numerals refer to similar or identical parts.
A variety of techniques and instruments have been developed for use in the removal or repair of tissue in arteries and similar body passageways. A frequent objective of such techniques and instruments is the removal of atherosclerotic plaques in a patient's arteries. Atherosclerosis is characterized by the buildup of fatty deposits in a patient's blood vessels. Often, over time, what initially is deposited as relatively soft, cholesterol-rich atheromatous material hardens into a calcified atherosclerotic plaque. Such atheromas restrict the flow of blood, and therefore often are referred to as stenotic lesions or stenoses, with the blocking material referred to as stenotic material.
Orbital atherectomy procedures have become common for removing such stenotic material. Such procedures are used most frequently to initiate the opening of calcified lesions in coronary arteries.
Several kinds of rotational atherectomy devices have been developed for removal of stenotic materials. In one type of device, such as that disclosed in U.S. Pat. No. 4,990,134 (Auth), a nickel-plated burr covered with an abrasive cutting material such as diamond particles is carried at the distal end of a flexible drive shaft. The burr rotates at high speeds (typically in the range of about 80,000-200,000 rpm) while it is advanced across the stenosis. As the burr is removing stenotic material, however, it also blocks blood flow. Further, once the burr has advanced across the stenosis, the artery will have been opened to a diameter equal to or only slightly larger than the maximum outer diameter of the burr. Moreover, fluoroscopy is typically utilized to assist the physician in placing the nickel-plated Auth-type burr in the general location of a stenosis in an artery. However, since the nickel-plated burr is not radiopaque, the ability of the physician to monitor, in real time, the actual removal of stenotic tissue is significantly hampered. In addition, this has an adverse effect on the ability of the physician to manage the risk of perforating the arterial wall while ensuring that the stenotic tissue is completely removed.
Moreover, the Auth-type burr uses a multi-step, electrochemical deposition process to plate the nickel on the distal tip of the burr. A secondary process requires hand work to remove any sharp edges and to drill a center shaft through the deposited nickel, leaving the distal tip with a profile resembling that of a drill bit with a hole through the center. The difficulties with the known process are that it is costly, time-consuming and it is extremely difficult to control. The results of the uncontrolled hand fluting of the distal tip is that it creates potential for misalignment of the central bore through the burr with the guide wire. This creates undesirable eccentric motion of the distal end which, in turn, may create surface erosion of the guide wire as the drive shaft rubs against it, friction welding of the drive shaft to the guide wire and, ultimately premature failure of the drive shaft and/or the guide wire may ensue. Finally, because the distal ends of the Auth-type burr have a fluted profile, during the procedure the rotating flutes are capable of either embedding into or perforating the arterial wall of the drive shaft is deployed beyond the end of the guide wire.
U.S. Pat. No. 5,314,438 (Shturman) discloses another atherectomy device having a drive shaft with a section of the drive shaft having an enlarged diameter, at least a segment of this enlarged diameter being covered with an abrasive material to define an abrasive segment of the drive shaft. When rotated at high speeds, the abrasive segment is capable of removing stenotic tissue from an artery. While this atherectomy device possesses several advantages over the Auth device due to its flexibility, it also is capable of only opening an artery to a diameter about equal to the diameter of the enlarged diameter section of the drive shaft. In addition, though this device permits use of intravascular ultrasound imaging to monitor the removal of stenotic tissue, thus reducing the risk of perforation of the tissue removing surface during the procedure, the device may remain susceptible to the problem of perforation due to the advancement of the device beyond the end of the guide wire which may result in perforation.
U.S. Pat. No. 6,494,890 (Shturman) discloses an atherectomy device having a drive shaft with a section of the drive shaft having an eccentric enlarged diameter, at least a segment of this enlarged eccentric diameter being covered with an abrasive material. When rotated at high speeds and placed within an artery against stenotic tissue, the eccentric nature of the enlarged diameter section cause the section to rotate in such a fashion as to open the stenotic lesion to a diameter substantially larger than the outer diameter of the enlarged diameter section. This device does permit use of intravascular ultrasound imagine to monitor the removal of stenotic tissue, thus reducing the risk of perforation of the tissue removing surface during the procedure. However, the device may remain susceptible to the problem of perforation due to the difficulties in monitoring the advancement of the device beyond the end of the guide wire which may result in perforation.
With reference to the Figures, the present inventive design incorporates a radiopaque atraumatic terminal guide at the distal end of the drive shaft. Specifically, with reference to
The handle 10 generally contains a turbine (or similar rotational drive mechanism) for rotating the drive shaft 12 at high speeds. The handle and turbine typically may be connected to a power source, such as compressed air delivered through a tube 22. A pair of fiber optic cables 24 may also be provided for monitoring the speed of rotation of the turbine and drive shaft 12. The handle also desirably includes a control knob 26 for advancing and retracting the turbine and drive shaft 12 with respect to the catheter 16 and the body of the handle 10.
The enlarged diameter section 14 may be concentric or eccentric in profile.
Continuing with reference to
Turning to
With reference to the Figures, the inventive drive shaft terminal guide will now be described. The terminal guide 15 (
The terminal guide 15 has a central orifice 60 therethrough sufficient in diameter to allow the guide wire 18 to pass through. The central orifice 60 has a proximal edge 62 and a distal edge 64. Referring now to
An interface 66 is formed between the guide wire 18 and the central orifice 60 of the terminal guide when the drive shaft 12 is deployed over the pre-positioned guide wire 18. In addition to the precision manufacturing of the terminal guide 15, further reduction of the possibility that the drive shaft 12, or the central orifice 60, will erode the guide wire 18 or become frictionally welded to the drive shaft 12 or central orifice 60 is obtained by introduction of a lubricating, cooling fluid flow within the interface 66. The fluid, typically saline or other biocompatible solution, may be introduced through a fluid supply line 20, as seen in
The terminal guide 15 greatly reduces loading on the guide wire 18 from the drive shaft 12. As the drive shaft 12 rotates, a force is developed substantially normal to the axis of the guide wire 18. The present invention distributes the load from this force into the terminal guide 15 instead of onto the drive shaft 12. In conjunction with the lubricated bearing effect of lubricating, cooling fluid flowing within the interface 66, this substantially eliminates any gouging of the guide wire.
The terminal guide 15 may further be manufactured using radiopaque material either embedded throughout the terminal guide 15 or bands of radiopaque material may be interspersed along the terminal guide 15 to facilitate locating the terminal guide during the atherectomy procedure and to reduce or eliminate the possibility that the distal end 13 of the drive shaft 12 is advanced beyond the distal end 19 of the guide wire 18. Alternatively, the terminal guide may be coated with a radiopaque material. The radiopaque material thus reduces the possibility that healthy arterial tissue will be damaged or that the arterial wall will be perforated.
The terminal guide 15 requires relatively high precision dimensional tolerances to prevent misalignment of the distal end 13 of the drive shaft 12 with respect to the pre-positioned guide wire 18. The impact of such misalignment is typically an unwanted eccentric motion which, in turn, may produce frictional surface erosion of the guide wire 18, frictional welding of the drive shaft 12 to the guide wire 18, and ultimately may produce premature failure of the drive shaft 12 and/or the guide wire 18. The required precision to prevent such misalignment in the present invention is preferably obtained by machining, casting, molding or otherwise precision forming by methods well known in the art so that the terminal guide precisely fits the distal end 13 of the drive shaft 12.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar to or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety to the extent allowed by applicable law and regulations. In case of conflict, the present specification, including definitions, will control.
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.
