Surgery – Instruments
Reexamination Certificate
1999-02-04
2001-03-20
Cohen, Lee (Department: 3739)
Surgery
Instruments
C606S128000, C601S004000, C604S022000, C604S035000
Reexamination Certificate
active
06203537
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to medical devices generally, and more particularly to ablation catheters.
BACKGROUND OF THE INVENTION
Angioplasty catheters are widely used for removing plaque from arteries. Some “roto-rooter” angioplasty catheters have rotary blades, which cut away the excess plaque. These catheters may cause damage to the coronary arteries.
An impact lithotripsy catheter is described in U.S. Pat. No. 5,246,447, issued Sep. 21, 1993 in the name of Rosen et al. This catheter includes a mass cap, supported by the windings of helically wound guide, at the distal end of the catheter. Laser pulses are applied through an optical fiber extending axially through the body of the catheter, to vaporize a portion of the mass cap at each pulse. The vaporization, in turn, results in rapid expansion of material at the proximal end of the mass cap, which generates a high velocity, short forward impulse. The impulse is transmitted through the mass cap to the kidney stone or other hard deposit. While effective in fragmenting calciferous and other hard deposits, this type of catheter may not remove soft or fatty deposits.
Acoustic catheters are used for angioplasty, for ablating plaque by sonification of the fluid in the affected artery. Some acoustic ablative catheters have a metal wire extending through the body of the catheter, and have an acoustic generator external to the body, and coupled to the proximal end of the metal wire. These catheters suffer from the problem of standing waves along the length of the wire, and of heating at nodes of the standing wave pattern. This type of acoustic ablation catheter has relatively low efficiency in coupling energy from the acoustic generator to the ablation site, because of heating losses at the nodes of the standing wave. Consequently, it is necessary to apply considerable acoustic power to the proximal end of the catheter, in order to couple enough energy to the catheter to effectively ablate plaque at the proximal end in the presence of the losses. The heating losses at the nodes, with this large acoustic input power, may cause damage to the patient at the locations of the nodes.
U.S. Pat. No. 5,423,797, issued Jun. 13, 1995 in the name of Adrian et al. describes an ablation catheter which includes a rotary-to-axial motion converter at its distal end, driven by a rotating shaft. The motion converter converts the rotary motion of the shaft into axially-directed acoustic pulsations, which are coupled to the surrounding fluid to thereby generate the acoustic energy by which ablation is accomplished. In one embodiment described therein, the motion converter includes an uneven or wavy surface (swash plate) which is rotated by the shaft, and a follower which is free for axial motion, which bears against the wavy surface, and is pushed distally by the protruding portions of the surface. While effective at generating acoustic energy, this type of catheter involves the use of moving parts.
Improved acoustic catheters are desired.
SUMMARY OF THE INVENTION
An ablation catheter according to the invention includes an elongated, flexible body defining a distal end, a proximal end, and a local axis, and a mass cap defining a proximal portion and a distal portion. A resilient mounting arrangement includes a proximal end and a distal end. The proximal end of the resilient mounting arrangement is physically coupled to the distal end of the body of the catheter, and the distal end of the resilient mounting arrangement is physically coupled to the mass cap, for holding the mass cap adjacent to the distal end of the catheter body. The resilient mounting arrangement defines either (one of) (a) transparent and (b) open regions, with the transparent or open regions lying between the distal end of the catheter body and the mass cap. The ablation catheter also includes at least one laser light radiator or source for producing one or more light beam(s). The laser light source is located near the distal end of the catheter body, and is oriented so as to project its light beam parallel to the local axis, through an open or transparent portion of the resilient mounting arrangement, to a proximal portion of the mass cap. In a particularly advantageous embodiment of the invention, the laser beam is focussed on a surface of the mass cap.
In a particularly advantageous embodiment of the invention, the ablation catheter is part of an ablation catheter system in which the mass cap, in conjunction with the resilient mounting arrangement, makes a physically resonant system defining a fundamental resonant frequency. In this catheter system, a laser light source driving arrangement external to the catheter drives the laser light source in such a manner as to generate the laser light in pulses having a repetition rate which is near the fundamental frequency of the oscillatory mechanical system formed by the cap/spring arrangement, or a multiple (sometimes known as a harmonic) of this repetition rate, and for, together with the ablation catheter, forming an ablation catheter system.
In another embodiment of the catheter according to the invention, which may be used in the ablation catheter system, the laser light source(s) comprise semiconductor laser chips, and further comprise an electrical conducting arrangement extending from the semiconductor laser chip(s) to the proximal end of the catheter. Each of the laser light sources may include a laser located outside the body of the catheter, a source of electrical energy coupled to the laser by arrangement lying outside of the catheter body, and an optical fiber light path extending from the laser, through the proximal end of the catheter, through the body of the catheter, and to the distal end of the catheter.
In a particularly advantageous embodiment of the invention, the mass cap further defines an aperture, the body of the catheter defines a lumen extending from a region near the proximal end of the catheter body to the distal end of the catheter body, and the resilient mounting arrangement also defines a path extending from the aperture of the mass cap to the distal end of the lumen of the catheter body. The aperture of the mass cap, the path of the resilient mounting arrangement, and that portion of the lumen of the catheter body near the distal end of the catheter body may be radially centered between the laser light sources. The mass cap and the body of the catheter may further define aspiration/infusion apertures, coupled together for the flow of fluid therebetween and together extending from a region near the proximal end of the catheter body to the distal end of the mass cap.
A more particular embodiment of the ablation catheter according to the invention includes an elongated, flexible body defining a distal end, a proximal end, and a local axis, and a mass cap defining a proximal portion and a distal portion. A resilient mounting arrangement including a proximal end and a distal end. The proximal end of the resilient mounting arrangement is physically coupled to the distal end of the body of the catheter, and the distal end of the resilient mounting arrangement is physically coupled to the mass cap, for holding the mass cap adjacent to the distal end of the catheter body. The resilient mounting arrangement defines at least one of a transparent region and an open region lying between the distal end of the catheter body and the mass cap. A plurality of laser light sources is provided, each of which produces a light beam. Each of the laser light sources is physically coupled to the distal end of the catheter body. Each of the plurality of laser light sources is circumferentially located relative to the local axis, and equally spaced about the local axis relative to others of the laser light sources, and oriented so as to project its light beam parallel to the local axis, through an optically transparent region (including an open region) of the resilient mounting arrangement, to a proximal portion of the mass cap. In a particularly advantageous version of this embodiment, the mass cap in conjunction
Cohen Lee
Meise William H.
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