Surgery – Instruments – Cutting – puncturing or piercing
Reexamination Certificate
1999-12-30
2002-12-17
Truong, Kevin T. (Department: 3731)
Surgery
Instruments
Cutting, puncturing or piercing
C604S022000
Reexamination Certificate
active
06494891
ABSTRACT:
BACKGROUND
This invention relates generally to medical devices, and more particularly concerns an improved ultrasound transmission member for use in an ultrasonic catheter for treatment of blockages of hollow anatomical structures.
In typical percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient through the brachial or femoral arteries and is advanced therein until the distal tip thereof is in the ostium of the desired coronary artery. A guide wire and a dilatation catheter having a balloon on the distal end thereof are introduced through the guiding catheter with the guide wire slidably disposed within an inner lumen of the dilatation catheter. The guide wire is first advanced into the patient's coronary vasculature until the distal end thereof crosses the lesion to be dilated and then the dilatation catheter is advanced over the previously introduced guide wire until the dilatation balloon is properly positioned across the lesion. The balloon may then be inflated to treat the lesion. Thereafter, a stent device may be located at the treated lesion, if deemed necessary.
In “ultrasonic” angioplasty, an ultrasonic angioplasty catheter is similarly advanced to an area of vascular blockage, and mechanical vibration at ultrasonic frequencies, generated typically by a piezoceramic transducer, is delivered along an ultrasonic angioplasty transmission member or wire to a distal catheter tip. When the distal catheter tip is abutted against intravascular blockage, the vibration of the distal end of the ultrasonic angioplasty transmission member removes the obstruction by mechanical impact and cavitation. However, such ultrasonic angioplasty transmission members frequently suffer from high-cycle fatigue, which can result in fracturing or breakage of the members during use.
Ultrasonic angioplasty transmission members are commonly connected to an extra-corporeal source of ultrasonic energy, so that it is generally necessary to deliver the ultrasonic energy over a relatively long distance, such as approximately 150 cm, to the intravascular blockage to be treated. Over such a distance, the ultrasonic energy attenuates as it passes along the length of the ultrasonic angioplasty transmission member resulting in a loss of system efficiency. To compensate for the loss, a greater amount of acoustical energy is delivered to the ultrasonic angioplasty transmission member at its proximal end than what actually reaches the treatment site. This delivery of higher levels of acoustic energy can increase fatigue and the chances of fracturing and breakage of the ultrasonic angioplasty transmission member during use. It is therefore desirable to provide an ultrasonic angioplasty transmission member that has a lower loss of the ultrasonic energy transmitted by the member so that lower levels of energy may be applied to the member.
In ultrasonic angioplasty techniques, accurate positioning of the ultrasound transmission member in the vasculature system to be treated requires a highly flexible ultrasonic delivery system with a low profile, especially for coronary ultrasonic angioplasty procedures, so that the catheter can more easily navigate the various vascular passages to be advanced to the occlusion. Nickel-titanium superelastic alloys have been useful in these respects as an ultrasound transmission member. Tapering or narrowing the distal end of an ultrasound transmission member to enhance flexibility of the ultrasound transmission member at its distal end is known from U.S. Pat. No. 5,304,115 (Pflueger et al.). While such tapering or narrowing typically decreases the rigidity and improves the bendability of the ultrasound transmission member, a significant increase in amplitude of the ultrasonic energy occurs at the tapered or narrowed region. Such an increase in amplitude can cause an increased likelihood of fracturing or breakage of the ultrasound transmission member at that point during use.
While it is known to harden ultrasonic angioplasty transmission members to reduce fracturing or breakage, as disclosed in U.S. Pat. No. 5,304,115 (Pflueger et al.), by providing a hard coating or skin, it would be desirable to constrain transverse vibration at narrowed or tapered areas of an ultrasonic angioplasty transmission member to reduce stress and to lessen the chances of fracturing at such areas where amplification of ultrasonic energy can occur, while still allowing longitudinal movement. Additionally, it has been found that providing a hard coating or skin to reduce stress and attempt to prevent fracturing can contribute to attenuation of vibration of the ultrasonic angioplasty transmission member and inhibit longitudinal movement.
Hence those skilled in the art have recognized a need for an ultrasound transmission member providing improved characteristics of strength, fatigue resistance, elasticity, and energy transmission for an ultrasonic delivery system for use in the treatment of intravascular blockages. It is also desirable that measures to reduce fracturing or breakage of such ultrasonic angioplasty transmission members not interfere with properties such as sonic propagation, tensile strength, and flexibility to navigate sharp bends and curves in the vasculature. The present invention fulfills these needs and others.
SUMMARY OF THE INVENTION
Briefly, and in general terms, the present invention is directed to an improved ultrasound transmission member for use in an ultrasonic angioplasty device, the ultrasound transmission member having a proximal end configured to be connected to an ultrasound transducer and a distal end for applying ultrasonic energy to an area of vascular blockage, and the ultrasound transmission member having a distal portion with at least one amplification region of reduced cross-sectional diameter where transverse vibration of ultrasonic energy transmitted by the ultrasound transmission member is amplified, the ultrasound transmission member comprising a constraining member disposed around the amplification region to reduce transverse vibration at the amplification region, to thereby lower stress and reduce fractures of the ultrasound transmission member while allowing longitudinal movement of the ultrasound transmission member.
In another aspect, the invention is directed to an ultrasonic angioplasty catheter device comprising an elongate flexible catheter having a proximal end, a distal end, and at least one lumen extending longitudinally therethrough, the catheter device comprising an ultrasound transmission member extending through aid lumen and having a distal end with a head for applying ultrasonic energy to an occlusive lesion, and a proximal end configured to be connected to an ultrasound generating device, the ultrasound transmission member having a distal portion with at least one amplification region of reduced cross-sectional diameter where transverse vibration of ultrasonic energy transmitted by the ultrasound transmission member is amplified wherein the ultrasound transmission member comprises a constraining member disposed around the amplification region to reduce transverse vibration at the amplification region to thereby lower stress and reduce fractures of the ultrasound transmission member while allowing longitudinal movement of the ultrasound transmission member.
In more detailed aspects, the ultrasound transmission member comprises a first generally cylindrical section of the ultrasound transmission member having a first cross-sectional diameter, and a second generally cylindrical section of the ultrasound transmission member distal to the first section and having a second cross-sectional diameter that is smaller than the first cross-sectional diameter, the amplification region being formed at a proximal portion of the second generally cylindrical section. The ultrasound transmission member further comprises a plurality of generally cylindrical sections, each of the plurality of generally cylindrical sections having
Cornish Wayne E.
Esselstein Robert C.
Fariabi Sepehr
Nita Henry
Advanced Cardiovascular Systems Inc.
Fulwider Patton Lee & Utecht LLP
Truong Kevin T.
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