U.S. patent number 4,848,336 [Application Number 07/227,000] was granted by the patent office on 1989-07-18 for apparatus for laser treatment of body lumens.
Invention is credited to A. Arthur Coster, Kenneth R. Fox.
United States Patent |
4,848,336 |
Fox , et al. |
July 18, 1989 |
Apparatus for laser treatment of body lumens
Abstract
A laser microsurgical method and apparatus are disclosed for
safely treating occluded body lumens with laser energy. The
disclosed method involves the use of pulsed laser energy from an
argon-ion laser to destroy the tissue of luminal occlusions, such
as atheromatous plaque and the like, with substantially no thermal
necrosis of the surrounding tissue. A flexible catheter and
associated laser microsurgical system is also disclosed which
provides for aiming of the fibers to transmit the laser beam at the
distal end of the catheter and rotational positioning of the
catheter to permit coverage of virtually the entire cross-sectional
area of the lumen. A lens system at the distal end of each laser
fiber minimizes beam divergence and directs the beam toward the
central axis of the catheter. A further embodiment of the catheter
of the invention provides an array of laser fibers which are
optically scanned with laser energy to cover the cross-sectional
area of the lumen. The system is designed to minimize the
possibility of damage to or perforation of the surrounding tissue
of the lumen.
Inventors: |
Fox; Kenneth R. (Arlington,
VA), Coster; A. Arthur (Alexandria, VA) |
Family
ID: |
26921063 |
Appl.
No.: |
07/227,000 |
Filed: |
July 29, 1988 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
772697 |
Sep 5, 1985 |
4784132 |
|
|
|
478781 |
Mar 25, 1983 |
4800876 |
|
|
|
329978 |
Dec 11, 1981 |
|
|
|
|
87894 |
Oct 24, 1979 |
|
|
|
|
32844 |
Apr 24, 1979 |
|
|
|
|
Current U.S.
Class: |
606/7 |
Current CPC
Class: |
A61B
18/20 (20130101); A61B 18/245 (20130101); A61B
2017/00154 (20130101); A61B 2017/22051 (20130101); A61B
2018/00636 (20130101) |
Current International
Class: |
A61B
18/20 (20060101); A61B 18/24 (20060101); A61B
17/22 (20060101); A61B 17/00 (20060101); A61B
017/36 () |
Field of
Search: |
;128/4-8,303.1,395-398 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
144764 |
|
Jun 1985 |
|
EP |
|
1900017 |
|
Aug 1970 |
|
DE |
|
2062951 |
|
Sep 1971 |
|
DE |
|
2640406 |
|
Mar 1978 |
|
DE |
|
2740969 |
|
Mar 1979 |
|
DE |
|
84/04879 |
|
Dec 1984 |
|
WO |
|
85/00010 |
|
Jan 1985 |
|
WO |
|
85/02532 |
|
Jun 1985 |
|
WO |
|
Other References
Limbectomies, Keratectomies, and Keratostomies Performed with a
Rapid Pulsed Carbon Dioxide Laser, Beckman et al., American Journal
of Ophthalmogy, vol. 71, No. 6, pp. 1277-1283, Jun. 1981. .
Pulsed Laser Iridotomy Apparatus, The Johns Hopkins University,
Applied Physics Laboratory, Fraser et al., pub. date unknown but
believed to be before 5/8/80. .
American Heart Journal, Laser-Dissolution of Coronary
Atherosclerotic Obstruction, Dec. 1981, Garret Lee et al., pp.
1074-1075. .
Optics and Laser Technology, Fibre Bundle Scanner for Laser
Photocoagulation Treatment, Feb. 1982, Fujii et al., pp. 39-40.
.
Applied Optics, Multispot Laser Photocoagulation System Using a
Fiber Bundle Scanner, vol. 21, No. 19, Oct. 1982, Fujii et al., pp.
3437-3442. .
American Heart Journal, Feasibility of Intravascular Laser
Irradiation for in vivo Visualization and Therapy of
Cardiocirculatory Diseases, Jun. 1982, Lee et al., p. 1076. .
The American Journal of Cardiology, Effects of Carbon Dioxide,
Nd-YAG, and Argon Laser Radiation on Coronary Atheromatous Plaques,
Dec. 1982, Abela et al., pp. 1199-1025. .
The American Journal of Cardiology, Laser Coronary Angioplasty:
Experience with 9 Cadaver Hearts, Dec. 1982, Choy et al., pp.
1209-1211. .
The American Journal of Cardiology, Transluminal Laser Catheter
Angioplasty, Dec. 1982, Choy et al., pp. 1206-1208. .
L.I.A., vol. 32 Icaleo (1982), Interactions Between Material
Processing and Surgery, Myron Wolbarsht, p. 1-5. .
Cardiology Times, 1983, Transluminal Laser Coronary Angioplasty is
Under Evaluation. .
Science, Selective Photothermolysis: Precise Microsurgery by
Selective Absorption of Pulsed Radiation, Apr. 1983, pp. 524-527.
.
Lasers in Surgery & Medicine, Far-Ultraviolet Laser Ablation of
Atherosclerotic Lesions, Linsker et al., 1984, pp. 201-206. .
Journal of Medical Engineering & Technology, Recanalization of
Arteries by Laser Radiation, Gillen et al., 1984, pp. 215-217.
.
Applied Optics, Argon Laser Disintegration of Thrombus and
Atherosclerotic Plaque, Kaminow et al., 1984, pp. 1301-1302. .
Clin. Cardio., Human Coronary Laser Recanalization, Choy et al.,
1984, pp. 377-381. .
Laser Focus/Electro-Optics, Excimer Lasers Offer Promise in
Surgical Applications, 1985, Muller et al., pp. 70-81. .
American Journal of Cardiology, Reduction of Laser-Induced
Pathologic Tissue Injury Using Pulsed Energy Delivery, Deckelbaum
et al., 1985, pp. 662-667. .
PCT International Search Report, 11/25/86. .
Partial European Search Report, EP 86 11 2166, 12/12/86. .
Communication Pursuant to Article 96(2) and Rule 51(2) EPC, Nov. 3,
1988..
|
Primary Examiner: Hindenburg; Max
Attorney, Agent or Firm: Wigman & Cohen
Parent Case Text
This application is a continuation of U.S. patent application Ser.
No. 772,677 filed Sept. 5, 1985 now U.S. Pat. No. 4,784,132 which
is a continuation-in-part of U.S. patent application Ser. No.
478,781, filed Mar. 25, 1983, now U.S Pat. No. 4,800,876, which is
a continuation-in-part of U.S. Patent Application Serial No.
329,978, filed Dec. 11, 1981, now abandoned, which is a
continuation of U.S. patent application Ser. No. 087,894, filed
Oct. 24, 1979, now abandoned, which is a continuation-in-part of
U.S. patent application Ser. No. 032,844, filed Apr. 24, 1979, now
abandoned.
Claims
What we claim is:
1. Apparatus for performing laser surgery in a body lumen having an
obstruction therein comprising:
catheter means for insertion in the body lumen, said catheter means
having a longitudinal axis and proximal and distal ends, fiber
means arranged in said catheter means for transmitting a beam of
laser energy from said proximal end to said distal end of said
catheter means to impinge upon the obstruction in said body
lumen;
laser means arranged adjacent the proximal end of said catheter
means for generating a non-continuous wave, pulsed laser beam
having a predetermined pulse duration, pulse repetition rate, pulse
energy and duty cycle selected to effect damage to the obstruction
with substantially no thermal necrosis of the surrounding tissue of
the body lumen.
2. Apparatus according to claim 1, wherein said fiber means include
a plurality of optical fibers, said laser means comprises an
optical scanning means for scanning said fibers with said beam of
laser energy.
3. Apparatus according to claim 2, wherein the distal ends of some
of said fibers are converged radially inwardly at an angle toward
said longitudinal axis.
4. Apparatus according to claim 3, including an end plate disposed
at the distal end of said catheter means for mounting the distal
ends of said fibers.
5. Apparatus according to claim 2, wherein the distal ends of some
of said fibers are diverged radially outwardly at an angle away
from said longitudinal axis.
6. Apparatus for performing laser surgery in a body lumen having an
obstruction therein comprising:
catheter means for insertion in the body lumen, said catheter means
having a sheath and a longitudinal axis and proximal and distal
ends, at least one fiber means arranged in said catheter means for
transmitting a beam of laser energy from said proximal end to said
distal end to impinge upon the obstruction in said body lumen;
laser means arranged adjacent the proximal end of said catheter
means for generating a non-continuous wave, pulsed laser beam
having a predetermined pulse duration, pulse repetition rate, pulse
energy and duty cycle selected to effect damage to the obstruction
with substantially no thermal necrosis of the surrounding tissue of
the body lumen; and
aiming means arranged within the sheath of said catheter means for
shifting the distal end of said fiber means relative to said sheath
and the longitudinal axis of the catheter means whereby said laser
beam is selectively aimed to impinge upon different points on the
obstruction.
7. Apparatus according to claim 6, including means for rotating
said catheter means about the longitudinal axis thereof.
8. Apparatus according to claim 6, wherein said aiming means
comprises a balloon arranged in said catheter means adjacent said
fiber means and means for incrementally inflating and deflating
said balloon.
9. Apparatus according to claim 6, including a lens system disposed
at the distal end of said fiber means, said lens system comprising
a converging lens converging said beam and a prism for canting said
beam toward the longitudinal axis of said catheter means.
10. Apparatus according to claim 8, wherein said fiber means is
arranged eccentrically in said catheter means, said balloon being
inflatable and deflatable to move said fiber means substantially
radially of said catheter means.
11. Apparatus according to claim 6, including a source of laser
energy, said fiber means comprising a plurality of optical fibers,
an optical scanner means interposed between said laser energy
source and the proximal end of said fiber means for scanning said
fibers with said laser energy.
12. Apparatus according to claim 6, including a circumferential
balloon arranged about the distal end of said catheter means and
means for inflating and deflating said circumferential balloon in
synchronism with the cardiac cycle.
13. Apparatus according to claim 6, further comprising:
means for rotating said catheter about the longitudinal axis
thereof;
a lens system disposed at the distal end of said fiber means, said
lens system comprising a converging lens for converging said laser
beam and a prism for canting said beam toward the longitudinal axis
thereof;
said fiber means being eccentrically arranged in said catheter
means, said aiming means comprising a balloon arranged along said
fiber means; and
means for inflating and deflating said balloon such that said fiber
means is shifted substantially radially of said catheter means.
14. Apparatus for performing laser surgery in a body lumen
comprising:
catheter means for insertion in the body lumen, said catheter means
having a sheath and a longitudinal axis and proximal and distal
ends, at least one fiber means arranged in said catheter means for
transmitting a beam of laser energy from said proximal end to said
distal end to impinge upon an obstruction in the body lumen;
means for rotating said cathetermeans about the longitudinal axis
thereof; and
aiming means arranged within the sheath of said catheter means for
shifting the distal end of said fiber means relative to said sheath
and the longitudinal axis of the catheter means whereby said laser
beam is selectively aimed to impinge upon different points on said
obstruction with substantially no movement of said catheter means
relative to the body lumen, said aiming means comprising a balloon
arranged in said catheter means adjacent said fiber means and means
for incrementally inflating and deflating said balloon.
15. Apparatus according to claim 14, wherein said fiber means is
arranged eccentrically in said catheter means, said balloon being
inflatable and deflatable to move said fiber means substantially
radially of said catheter means.
16. Apparatus according to claim 14, including a source of laser
energy, said fiber means comprising a plurality of optical fibers,
an optical scanner means interposed between said laser energy
source and the proximal end of said fiber means for scanning said
fibers with said laser energy.
17. Apparatus for performing laser surgery in a body lumen
comprising:
catheter means for insertion in the body lumen, said catheter means
having a sheath and a longitudinal axis and proximal and distal
ends, at least one fiber means arranged in said catheter means for
transmitting a beam of laser energy from said proximal end to said
distal end to impinge upon an obstruction in the body lumen;
a lens means disposed at the distal end of said fiber means, said
lens means comprising a converging lens for converging said beam
and a prism for canting said beam toward the longitudinal axis of
said catheter means; and
aiming means arranged within the sheath of said catheter means for
shifting the distal end of said fiber means relative to said sheath
and the longitudinal axis of the catheter means whereby said laser
beam is selectively aimed to impinge upon different points on said
obstruction with substantially no movement of said catheter means
relative to the body lumen.
18. Apparatus for performing laser surgery in a body lumen
comprising:
catheter means for insertion in the body lumen, said catheter means
having a sheath and a longitudinal axis and proximal and distal
ends, at least one fiber means arranged eccentrically in said
catheter means for transmitting a beam of laser energy from said
proximal end to said distal end to impinge upon an obstruction in
the body lumen;
means for rotating said catheter about the longitudinal axis
thereof;
a lens system disposed at the distal end of said fiber means, said
lens system comprising a converging lens for converging said laser
beam and a prism for canting said beam toward the longitudinal axis
thereof;
aiming means comprising a balloon arranged within the sheath of
said catheter means for shifting the distal end of said fiber means
relative to said sheath and the longitudinal axis of the catheter
means; and
means for inflating and deflating said balloon such that said fiber
means is shifted substantially radially of said catheter means
whereby said laser beam is selectively aimed to impinge upon
different points on said obstruction with substantially no movement
of said catheter means relative to the body lumen.
19. Apparatus for performing laser angioplasty by effecting damage
to an obstruction in the vascular system of a human comprising:
a laser means for generating a non-continuous wave, pulsed laser
beam having a predetermined pulse duration, pulse repetition rate,
pulse energy and duty cycle selected to operate substantially at
the threshold of the thermal relaxation time of the irradiated
volume of the obstruction such that damage is effected to the
obstruction with substantially no thermal necrosis of the
surrounding tissue of the vascular system; and
a flexible optical fiber means for transmitting said laser beam
from said laser means through the vascular system to the
obstruction therein.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method of and apparatus for the
laser treatment of occluded body lumens of mammals, especially
humans, and more particularly to the intraluminal use of laser
energy to perforate and/or remove luminal occlusions, such as
thrombi and/or atherosclerotic placques in the cardiovascular
system.
Cardiovascular disease is a major cause of death and morbidity and
manifests a grave concern to both the scientific community and the
lay public. Arteriosclerotic cardiovascular pathophysiology is a
complex of diseases which affects many blood vessels in the body,
the decreased lumen diameter causing tissue ischemia. Other very
common diseases, such as diabetes mellitus, enhance the occlusion
of important blood vessels and ischemia of the organs they supply.
Those diseases, aggravated by such other common abnormalities as
hypertension, and other vascular diseases and cardiovascular
diseases, account for cerebrovascular accidents, myocardial
infarctions, and other devastating illnesses, including loss of
life and limb. Unfortunate individuals affected with
arteriosclerotic cardiovascular disease and the related
vasculopathies often manifest disease in coronary, carotid and
cerebral arteries, in popliteal, tibial and dorsalis pedis arteries
of the lower extremities and in other vessels. Those individuals,
apart from having a shortened life expectancy, and suffering from
sudden death, frequently also suffer from other debilitating
problems including angina, shortness of breath and restricted
activity, claudication or restricted use of the lower extremities,
sometimes with loss of those extremities from disease, and loss of
functions of movement, speech, cerebral interpretation and
cognitive abilities.
Historically, there are few effective means for preventing some of
the foregoing disastrous medical problems. Patients with certain
types of coronary insufficiencies documented by certain coronary
angiographic findings may be helped symptomatically by coronary
artery bypass operations. Other patients sometimes may be benefited
by other types of arterial surgery, for example, various bypass
operations, or endarterectomies, which surgically attempt
recanalization of certain occluded blood vessels or other
operations. Those are generally patients with severe disease, but
yet who meet certain diagnostic criteria and who are healthy enough
to undergo what amounts to major surgery with relatively high
morbidity and mortality rates. The cost is immense for many of
these operations and incumbent hospitalization, including expensive
special equipment which is required, and special training which is
necessary for a team to operate the special surgical equipment. For
example, it is estimated that a single coronary bypass operation
may cost a patient over $50,000 including the hospitalization fees,
and surgical fees. Availability of this special type of surgery for
vascular problems is limited. Long term efficacy of coronary bypass
surgery is as yet unknown, and the appropriate diagnostic and
surgical criteria remain controversial. Because of the severity of
the morphology and nature of the disease, for many patients
treatment has been unavailable and has been beyond the current
scope of surgical intervention. For example, many patients lose
extremities or their lives by virtue of having these inoperable
conditions.
In a different context, problems of lumens of the body,
particularly small lumens, are complicated by occlusive diseases of
other types. As an example in the nervous system, the Aqueduct of
Sylvius, in the ventricular system of the brain, may be blocked in
a child born with congenital hydrocephalus. This condition
necessitates a complicated and often unsuccessful corrective
neurosurgical procedure known as shunting. Considering the
genito-urinary system, for example, fallopian tubes may become
occluded by inflammatory or other disease processes. This may cause
infertility and is a common problem. There is no effective
treatment for this problem at this point in time, and this has
stimulated interest in the "test tube baby" controversy.
One suggested solution to the problem of atherosclerotic
obstructions is a non-operative technique to improve coronary blood
flow known as percutaneous transluminal coronary angioplasty
(PTCA). Generally, PTCA involves introducing a balloon catheter
into the femoral artery or by brachial cutdown and fluorscopic
positioning at the appropriate coronary ostium. Pressure monitoring
is also used to aid in positioning the balloon tip of the catheter
at the stenosis. The balloon is inflated for 3-5 seconds to
mechanically enlarge the stenosis and is then deflated for
measurement of distal coronary pressure. The cycle may be repeated
several times until a satisfactory decrease in pressure gradient is
achieved.
Although the PTCA technique is sometimes effective to improve
coronary blood flow, there are complications which must be weighed
before undertaking the procedure. Such complications which may
occur include arterial spasms, myocardial infarction, thrombotic
occlusion, embolization and dissection, or frank perforation of the
vessel wall.
It has also been suggested that cardiovascular occlusions, as well
as occlusions in other body lumens, might be vaporized by means of
continuous wave (CW) laser energy. U.S. Pat. No. 4,207,874 to Choy,
for example, discloses a flexible conduit which accommodates a
fiberoptic bundle divided into light source, viewing and laser
bundle portions. The flexible conduit is introduced into a vein or
other body lumen and advanced until it contacts an obstruction such
as a thrombus. A laser apparatus optically associated with the
laser fiber bundle is then activated so that the laser energy
vaporizes the obstruction, the remaining particles of which are
then removed by suction.
Other flexible laser endoscopes for use in the therapeutic laser
treatment of body lumens are disclosed in U.S. Pat. Nos. 4,072,147;
4,146,019; 4,170,997; and German Offenlegungsschrift No. 2,640,406.
Such intraluminal laser devices typically are said to function by
thermal vaporization and/or coagulation of the luminal obstruction
mass.
One of the most serious risks inherent in the intraluminal use of
laser radiation, especially in coronary or cerebral blood vessels,
is the possibility of perforation of or thermal damage to the
vessel walls and surrounding tissue. Accordingly, intravascular
recanalization of occluded blood vessels is still an experimental
procedure.
Recently, investigators have reported the use of continuous wave
(CW) argon, neodymium-YAG and carbon dioxide laser sources to
successfully vaporize, coagulate and penetrate atherosclerotic
placque in animals and in sections of coronary arteries taken from
human cadavers. However, the investigators also report perforation
of the vessel walls in many cases, particularly at laser energy
levels which have been increased to a level sufficient to effect
vaporization of the placque.
Such laser energy levels are appropriately characterized as the
"thermal" mode of laser operation which involves causing damage to
tissue by virtue of heat accumulation in the tissue impinged by the
laser radiation. Excessive heat accumulation causes thermal
degradation or thermal necrosis. In other words, the temperature of
the tissue rises, tissue proteins are denatured and ultimately the
tissue is coagulated and "evaporated" or "vaporized." While the
laser thermal energy mode is effective in coagulating and
vaporizing many tissues, including the tissues forming
atherosclerotic placques and stenoses, its use heretofore in
occluded coronary and cerebral blood vessels, for example, is not
sufficiently safe and controllable. Consequently, the problem of
inadvertent damage to or destruction of surrounding vessel tissue
has been a major obstacle in the development of an acceptable
microsurgical technique for laser angioplasty in the human vascular
system.
Apart from the risk of using continuous wave (CW) laser energy in
the human vascular system, the prior art intraluminal laser devices
lack effective mechanisms for "aiming" the laser beam to minimize
the possibility of inadvertent damage to the vessel walls and to
maximize the exposure of a large area of the occlusion, e.g., the
atherosclerotic placque, to the laser energy.
SUMMARY AND OBJECTS OF THE INVENTION
In view of the foregoing limitations and shortcomings of the prior
art intraluminal laser devices, as well as other disadvantages not
specifically mentioned above, it should be apparent that there
still exists a need in the art for a laser microsurgical apparatus
for use in coronary angioplasty which is capable of effecting
recanalization of occluded coronary and cerebral blood vessels at
minimum risk of perforation or thermal necrosis of the vessel
walls. It is, therefore, a primary objective of this invention to
fulfill that need by providing a novel coronary arterial catheter
and associated laser microsurgical system and a method of using the
same whereby the laser energy radiated within the cardiovascular
system is carefully controlled and aimed in such a way as to
effectively destroy or penetrate atherosclerotic placque, yet
minimize the risk of vascular perforation or thermal necrosis of
the surrounding tissue.
More particularly, it is an object of the present invention to
provide an effective method of delivering laser energy in a safe,
substantially non-heat conducting or conduction-free mode by
controlling the pulse width or duration, pulse repetition rate, and
duty cycle of the laser energy within predetermined ranges and by
using optical switching to sequentially direct the laser energy at
selected target areas.
It is another object of the present invention to provide a flexible
catheter adapted to be inserted into a body lumen, such as an
obstructed coronary artery, said catheter having one or more quartz
glass laser fibers which can be "aimed" at a particular target
within a target area comprising substantially the entire
cross-sectional area of the body lumen.
Yet another object of the invention is to provide a laser
microsurgical system connected to the proximal end of a flexible
angiographic catheter for controlling the positioning,
illumination, visualization, firing and analysis functions of the
system.
Still another object of the invention is to provide a flexible
angiographic catheter for use in occluded blood vessels in
combination with laser microsurgical apparatus, said catheter
having one or more laser fibers, each of which is provided with a
lens system which minimizes divergence of the laser beam and
prismatically cants the laser beam toward the center of the blood
vessel to intensify the cutting effect of the beam and to minimize
the possibility of perforation of the vessel walls.
Another object of the invention is to provide a flexible catheter
adapted to be inserted into a body lumen and having a plurality of
laser fibers disposed within the catheter, such fibers being
selectively scanned with laser energy by an optical scanner to
"aim" the laser energy at a particular target area in the overall
cross-sectional area of the body lumen.
Briefly described, the aforementioned objects of the invention are
accomplished according to its apparatus aspects by providing a
flexible catheter having an outside diameter from about 1.2 to
about 5.0 millimeters, which is especially suitable for use in
coronary, cerebral and somewhat larger carotid blood vessels, for
example, to remove occlusions, such as atheromatous placque. Within
the catheter sheath there are provided a plurality of optical
fibers and fluid channels.
In one embodiment of the invention, the optical fibers include a
bundle of laser transmitting fibers eccentrically arranged relative
to the catheter axis and radially movable toward that axis by means
of a balloon positioned within the catheter sheath. Each laser
fiber has a distal lens system which converges and cants the
radiation beam away from the circumference of the catheter and
toward the axis thereof. Alternate embodiments of the catheter
include distal lens systems for the laser fibers which may comprise
one or more diverging lenses for special applications or techniques
to be hereinafter described.
A flexible optical fiber viewing element with a distal lens system
is provided within the catheter sheath which comprises a plurality
of individual fibers having a glass cladding and extending over a
substantial part of the cross-sectional area of the catheter, for
instance, 50% or more. An illuminating system comprising several
individual plastic clad quartz glass fibers cooperates with the
optical viewing element and is arranged adjacent thereto for
delivering white light from a conventional light source.
Fluid systems within the catheter include an outflow or suction
channel for removal of fluids and debris and two or more inflow
channels for injection of saline, pharmacologic agents, radiopaque
positioning dyes, immuno-specific antibodies and the like. Carbon
dioxide gas channels are also provided for inflation/deflation of
both the laser aiming balloon and a balloon circumferentially
disposed about the catheter adjacent the distal end thereof for
occluding the vascular lumen and for establishing stabilization of
the catheter distal end relative to said lumen.
A laser microsurgical system is operatively connected to the
proximal end of the flexible angiographic catheter and comprises a
proximal optical and fluid coupler for interconnecting the optical
fibers and fluid channels of the catheter to the various system
components, such as the laser apparatus and control, laser fiber
optical scanner, illumination and visualization systems,
positioning systems and fluid systems.
The objects of the invention are accomplished according to its
method aspects by the use of visible light laser energy in the
wavelength range of 351 to 515 nanometers, and, preferably, the
blue-green emission lines at wavelengths of 488 and 514 nanometers
from an argon-ion laser with a peak power output of about 20 watts,
such as a Spectra-Physics 171 Laser. The argon laser apparatus is
operated in the pulsed or non-conducting mode using a pulse width
or duration in the range of from 5 to 200 milliseconds and a pulse
repetition rate of 1 to 50 pulses per second with a duty cycle of
between 5 and 50%. The preferred pulse energy is in the range of
from 150 to 500 millijoules. Spot size for each fiber in the laser
fiber bundle may be from 100 to 500 microns, preferably, the
largest possible spot size in that range compatible with energy
density requirements.
The above parameters of the pulsed laser energy are selected to
effect damage to a luminal obstruction with substantially no
thermal necrosis of the surrounding tissue. A hole is drilled in
the obstruction by heating a given volume of the tissue thereof to
its boiling point and then supplying the heat of vaporization to
that volume to convert it to vapor. Ideally, the total laser energy
needed to vaporize the given volume of the tissue of the
obstruction is delivered in such a short period of time that heat
conduction to the surrounding tissue is negligible. That time
period is defined as the "thermal time constant" or "thermal
relaxation time" for the given volume of tissue. According to the
invention, the pulse characteristics, e.g., pulse width, pulse
repetition rate and energy, are selected to operate in the
conduction-free mode, that is, the laser energy is preferably
delivered just at the threshold of the thermal relaxation time of
the illuminated volume of the obstruction tissue.
Experimental results have indicated that over the range of laser
focal diameters of 50 to 100 microns for an argon-ion laser, the
diameter of the laser drilled hole in arterial placque is
approximately 500 microns, i.e., 5 to 10 times greater than the
laser focal diameter. That phenomenon is believed to be the result
of a combination of strong, small angle scattering and weak
absorption of the placque tissue. The larger area, and consequent
larger volume, of illuminated tissue results in a greater energy
threshold for drilling the placque, that is, a greater thermal
input is necessary because of the scattering of the laser light and
the absorption characteristics of the placque. For the argon-ion
laser, the energy threshold is about 200 millijoules per pulse over
a pulse width of 200 milliseconds or less.
An alternate embodiment of the invention takes advantage of the
foregoing experimental results by locating a plurality of laser
fibers in a flexible catheter in an array with the laser fibers
appropriately spaced to provide substantially complete coverage of
the cross-sectional area of a body lumen or vessel with little or
no overlapping of the drilled laser hole. Thus, "aiming" may be
accomplished by optically scanning the plurality of laser fibers to
impinge laser energy on selected target areas, e.g., a plurality of
target areas, each having a 500 micron diameter, over the entire
cross-sectional area confronting the distal end of the catheter.
Optical scanning of the laser fibers in a predetermined sequence
also permits a greater number of pulses or "shots" to be made in a
given time period without exceeding the energy threshold and
causing thermal necrosis of the surrounding tissue. The laser
fibers disposed adjacent the outermost periphery of the catheter
may also be "skewed" toward the center of the catheter to minimize
the possibility of perforation of the luminal wall.
With the foregoing and other objects, advantages and features of
the invention that will become hereinafter apparent, the nature of
the invention may be more clearly understood by reference to the
following detailed description of the invention, the appended
claims, and to the several views illustrated in the attached
drawings
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a transverse cross-sectional view of a first embodiment
of the flexible catheter of the present invention taken along line
1--1 of FIG. 2;
FIG. 2 is a longitudinal cross-sectional view, partly broken, of
the first embodiment of the catheter of the invention taken along
line 2--2 of FIG. 1;
FIGS. 3A-3D are transverse cross-sectional views similar to FIG. 1
showing the positioning of the laser fiber bundle;
FIG. 4 is a view illustrating the positioning of the distal end of
the catheter in a body lumen adjacent a partial occlusion of the
lumen;
FIG. 5 is a schematic block diagram showing the laser microsurgical
system of the present invention;
FIG. 6 is a transverse cross-sectional view of the distal end of an
alternate embodiment of the flexible catheter of the present
invention, taken along line 7--7 of FIG. 6; and
FIG. 7 is a longitudinal cross-sectional view of the catheter of
FIG. 6 taken along line 7--7 showing skewing of the outermost laser
fibers.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now in detail to the drawings wherein the same parts are
designated by the same reference numerals throughout, there is
illustrated in FIGS. 1 and 2 cross-sectional details of the distal
end of the inventive flexible catheter which is designated
generally by reference numeral 10. In those circumstances wherein a
particular element or aspect of the invention has been described in
greater detail in one or more of the aforementioned copending
related applications, appropriate reference will be made herein to
such application(s).
The catheter 10 comprises a plastic sheath 12 which may be a
non-toxic polyvinylchloride (PVC) or other suitable non-toxic
plastic material. The outside diameter of the catheter 10 for use
in the laser coronary angioplasty techniques described herein is
from about 1.2 to about 5.0 millimeters, but may be larger in
diameter for use in other, larger body lumens.
Disposed within the catheter sheath about the central axis 14
thereof are a plurality of elements extending longitudinally of the
catheter and, for convenience of illustration, are shown in FIGS. 1
and 3A-3D as being somewhat loosely disposed in spaced relation to
one another. In the actual construction of the catheter, the
elements are in closer proximity to one another than shown in the
drawings to provide a somewhat greater packing density consistent
with the requirement for shifting the laser fiber bundle relative
to the catheter axis in the manner described hereinafter.
A laser fiber bundle 16 is arranged eccentrically of the catheter
axis 14 and, in a preferred form, comprises four quartz glass laser
fibers 18a-18d for transmitting the laser energy, each fiber having
a core diameter of from 50 to 200 microns. Laser fibers 18a-18d are
embedded in a laminated sheath or cladding 20 of non-toxic
polyethylene or PVC. As shown in FIG. 1, the four laser fibers are
preferably orthogonally arranged with the axes of two of the fibers
18a and 18c disposed on a radial plane through the catheter axis
14.
An elongate balloon 22 is bonded or otherwise affixed to the
circumference of the laser fiber bundle 16 at the portion thereof
proximate the catheter sheath 12 and extends parallel to the axis
of the laser fiber bundle as shown in FIG. 2. Inflation of the
balloon 22 exerts a radially inward force on the laser bundle 16
tending to urge the same toward the catheter axis 14 and thereby
"aiming" the laser energy as more fully described hereinafter in
connection with FIGS. 3A-3D.
Arranged at the lowermost portion of the catheter, as viewed in
FIG. 1, is a visualization optical element 24 which is of generally
conventional construction. Optical viewing element 24 is generally
crescent-shaped in cross-section and comprises a plurality of 5,000
to 10,000 individual glass fibers 26, each having a hexagonal
cross-section to improve the packing factor The fibers 26 each have
a flat-to-flat dimension of about 4 microns and are packed tightly
together and fused only at their proximal and distal ends to
preserve flexibility. The bundle of fibers is ensheathed in a glass
cladding 28 and a lens system 30 (FIG. 2) of known configuration,
i.e., two plano-convex lenses, is fused to the distal end of the
viewing element 24 for providing wide angle visualization within
the body lumen. See also related U.S. patent application Ser. No.
329,978.
Illumination of the surgical area is provided by three fused quartz
glass fibers 32, 34, 36 of about 50 microns diameter which are clad
with a PVC sheath 38 As shown in FIG. 1, the illuminating fibers
are preferably arranged substantially diametrically for most
effective illumination of the central portion of the body
lumen.
The fluid systems of the catheter, in addition to the laser fiber
aiming balloon 22, include a suction channel 40 and two inflow
channels 42, 44. The suction channel 40 is used for debris removal
and for suctioning fluids from the intraluminal region at the
distal end of the catheter Inflow channels 42, 44 are employed for
injecting fluids such as saline, pharmacologic agents, radiopaque
positioning dyes and immuno-specific antibodies, among others.
A conventional circumferential balloon 43 is arranged about the
catheter 10 adjacent the distal end thereof as shown in FIG. 4.
Inflation of balloon 43 occludes flow in the lumen L and
establishes a fixed, stabilized position of the distal end of the
catheter 10. Such balloons and the methods and apparatus for
inflating and deflating the same are well-known in the art and,
therefore, need not be described in greater detail herein.
As shown in FIG. 2, at the distal end of each laser fiber 18a-18d,
there is epoxied a converging lens 46 for focusing the laser energy
beam and preventing undesirable divergence toward the luminal wall
and a prism 48 for bending or "canting" the eccentric laser beam
from each fiber toward the center of the lumen. Total divergence
angle of the preferred 100-500 micron diameter spot for each fiber
is preferably no greater than 5.degree.. Preferably, the optical
axes of the prismatically canted laser beams are maintained in
parallel relationship to prevent spot "overlap" and beam
divergence.
In certain circumstances, it may be desirable to insert a catheter
with a laser fiber bundle having a diverging lens system at the end
of each laser fiber. For instance, if the distal end of the
catheter directly abuts an occlusion of atheromatous placque, a
greater laser impact area could be achieved with a diverging lens
arrangement. After destruction of the first few millimeters of the
placque is accomplished the catheter would normally be replaced by
a catheter having the converging lens system shown in FIG. 2
With reference now to FIGS. 3A-3D, FIG. 3A corresponds
substantially to FIG. 1 and shows the balloon 22 in its deflated
condition with the laser fiber bundle in its most eccentric radial
position in relation to the central axis 14 of the catheter. As the
balloon 22 is gradually inflated, the laser fiber bundle is
incrementally urged substantially radially toward the axis 14 until
it reaches a position of minimum eccentricity as shown in FIG.
3B.
FIGS. 3C and 3D illustrate the same conditions of
inflation/deflation of balloon 22 as shown in FIGS. 3A and 3B,
respectively, except that the catheter 10 has been rotated exactly
180.degree.. It will be understood by those skilled in the art that
by the appropriate selection of angle of rotation of the catheter
and incremental inflation/deflation of balloon 22, the four 200
micron spots from the laser fibers 18a-18d can be positioned to
impinge at any target area over virtually the entire
cross-sectional area of the body lumen being treated.
Referring now to FIG. 4, the distal end of the catheter 10 is shown
fixed in position in a lumen L adjacent a partial occlusion X. The
uppermost pair of diverging dotted lines represents a laser energy
beam B from laser fiber 18a when said fiber is positioned on a
vertical plane at a location of greatest eccentricity from the
catheter axis. Beam B has a total divergence angle 50 of 5.degree.;
however, because the beam has been prismatically canted by the lens
system 46, 48 shown in FIG. 2, the diverging beam does not impinge
on the wall of the lumen L, but rather is directed toward the
central portion of the lumen L. Likewise, the lowermost pair of
diverging dotted lines in FIG. 4 represents a laser energy beam B'
from laser fiber 18a when said fiber is positioned exactly
180.degree. from the position at which beam B was generated. Beam
B' also has a total divergence angle 52 of 5.degree. as shown in
FIG. 4.
It should be apparent from the foregoing description of FIGS. 3A-3D
and FIG. 4 that the laser energy beams transmitted by the laser
fiber bundle 16 of the catheter are not only capable of being
"aimed" at virtually any target area within the lumen, but are
converged and canted so as to minimize the possibility of laser
beam impingement on the lumen walls.
Positioning of the distal end of the catheter 10 is aided by known
radiographic visualization procedures. For this purpose, it is
advantageous to mark the periphery of the distal end of the
catheter with a plurality of radiopaque strips 54, 56, 58 of
predetermined size and positioned for determining both the
rotational and axial positions of the catheter within a coronary
artery, for example
The laser microsurgical system 60 of the invention is shown
schematically in FIG. 5 The system 60 includes a laser source 62
which is preferably an argon-ion laser, such as a Spectra-Physics
171 Laser for generating a pulsed laser beam. The output of laser
source 62 is a pulsed laser beam 64 which is inputted to a
multi-fiber optical scanner 66 of a known type, for example, of the
type described by Fujii et al in Applied Optics, Vol. 21, No. 19,
pp. 3437-3442, Oct. 1, 1982. Scanner 66 is used to scan the four
laser fibers 18a-18d of the laser fiber bundle 16 with pulsed laser
beam 64.
Control of pulse width or duration, pulse repetition rate,
wavelength, length of exposure, intensity and firing is provided by
a laser control 68 associated with the laser source 62. Firing of
the laser 62 is accomplished by closing a firing switch 69 which
may be, for example, a foot pedal switch
The proximal end of the optical visualization element 24 supplies
an optical image to a viewing microscope 70 which has a built-in
eyepiece shutter mechanism 72. The shutter 72 is responsive to
activation of the laser source 62 to prevent back-scatter of laser
energy which could damage the surgeon's eyes.
The optical image from optical element 24 is also supplied to an
image analyzer 74 controlled by microprocessor 76 both of which are
used to analyze the visual images transmitted from the intraluminal
region at the distal end of the catheter and to aid in longitudinal
positioning of the catheter distal end, "aiming" of the laser fiber
or fibers at the appropriate target in the intraluminal region and
timing of the laser firing signal in relation to the cardiac cycle.
A suitable microprocessor and image analyzer is a Videoplan
Computerized Image Analyzer available from Carl Zeiss, Inc., 444
Fifth Avenue, New York, New York 10018.
A conventional cathode ray tube video display 78 and video recorder
80 are connected to the image analyzer for real time observation
and recording, if desired, of the microsurgical procedure.
An illumination source 82 is connected to the proximal ends of
optical fibers 32, 34, 36 for delivery of white light thereto. The
light is provided by mercury or xenon high pressure arc lamps
within quartz enclosures; however, other types of light sources may
be used. A vacuum unit 84 and fluids input unit 86 are connected to
the suction channel 40 and fluid inflow lines 42, 44,
respectively
For inflation and deflation of the aiming balloon 22 and
circumferential balloon 43, a fluid pressure source 88, such as
pressurized carbon dioxide, is connected through respective
electrically-operable solenoid valves 90, 92 to the pneumatic tubes
94, 96 supplying the aiming balloon 22 and the circumferential
balloon 43, respectively
The proximal end of the catheter 10 is mounted in an axial and
rotational drive mechanism 98 which rotates the catheter about its
axis and moves the same axially in response to mechanical or
electrical signals from a micromanipulator 100 which, in turn,
receives command signals from the microprocessor 76. Suitable
micropositioners are well-known in the art and are available from
numerous sources, such as Klinger Scientific Corporation, 110-120
Jamaica Avenue, Richmond Hill, New York 11148. See also related
application, Ser. No. 329,978.
It is also advantageous to synchronize the occlusion of the
coronary artery with the balloon 43 and the firing of the laser 62
with the cardiac cycle. Generally, it is desirable to inflate the
catheter balloon 43 during the filling phase of the cardiac cycle
and deflate the balloon during the pumping phase of the cardiac
cycle. In that way, blood flow is occluded under minimal pressure
conditions in the coronary artery. For this purpose, a conventional
counterpulsator 102 may be used which senses ventricular output
with an aortic catheter independently of the catheter 10 of the
invention. One suitable counterpulsator is known as System 82 and
is manufactured by Datascope Corporation, 580 Winters Avenue,
Paramus, New Jersey 07652. See also related application, Ser. No.
329,978.
An alternative or second embodiment of the catheter of the
invention is shown in FIG. 6 and identified with reference numeral
110. The catheter 110 comprises a plastic sheath 112 similar to the
sheath 12 of the FIG. 1 or first embodiment of the invention, the
outside diameter of which is preferably from about 1.2 to about 5.0
millimeters for use in the described laser coronary angioplasty
techniques. The FIG. 6 embodiment illustrates a catheter having an
outside diameter of about 1.5 millileters which diameter is
essentially defined by the arrangement of the laser fiber array
disposed within the sheath 112 as explained in greater detail
hereinafter.
A plurality of elements similar to those illustrated in FIGS. 1 and
2 are arranged to extend longitudinally within the sheath 112 about
the longitudinal axis 114 thereof and, like the showing of FIG. 1,
are somewhat loosely disposed in relation to one another, although
in actual practice the elements are packed in closer proximity,
preferably in a fixed relationship to one another and to the sheath
112.
The catheter 110 has a similar arrangement of optical viewing
element 124, illumination fibers 132, 134, 136, suction channel 140
and inflow channels 142, 144 as the first embodiment of the
invention. However, in contrast to the laser fiber bundle 16 of the
first embodiment of the invention, individually clad laser fibers
118 of the second embodiment are disposed about the catheter axis
114 in a predetermined, parallel array designed to provide
impingement of laser energy on substantially the entire
cross-sectional area of an obstruction confronted by the catheter
110 with little or no overlapping of laser impingement.
Inasmuch as experiments have indicated that drilled holes with an
argon-ion laser have a diameter of about 500 microns regardless of
laser focal diameter, an array of seven (7) 50 to 200 micron
diameter fibers 118 in the arrangement shown in FIG. 6 will provide
laser energy coverage of virtually the entire cross-sectional area
of a luminal obstruction confronting the catheter 110, particularly
in the central region thereof as shown by the dashed line areas 116
of laser impingement. Advantageously, the largest areas 120 not
included in the total laser impingement area are located at the
outermost periphery of the catheter adjacent the vessel walls where
laser energy impingement is least desirable, and, in fact, may be
detrimental.
In view of the above teachings, various arrangements of laser
fibers for different diameter catheters will be apparent to those
skilled in the art. For example, the same seven (7) fiber array may
be used for a 1.2 millimeter diameter catheter by arranging the
centers of the laser fibers at a 400 micron spacing rather than the
500 micron spacing shown in FIG. 6. While a certain amount of laser
impingement overlap will result from that arrangement, by
appropriate scanning of the laser fibers with laser energy any
overheating of the tissue can be avoided.
Generally speaking, a laser fiber disposed on the axis 114 of the
catheter is preferred, but is not essential. Thus, although a 1.2
millimeter diameter catheter is preferably provided with an array
of 5 to 7 laser fibers, an array of four (4) laser fibers
equiangularly spaced may be provided with their impingement areas
in targential relationship. While such an arrangement would not
provide laser impingement in the central region of an obstruction
confronting the catheter, destruction of the obstruction
surrounding the central region will eliminate support of such
central region and ultimately cause it to gravitate to a laser
impingement area where it will be destroyed.
In larger diameter catheters, a larger number of laser fibers are
preferably employed. For instance, a 5.0 millimeter diameter
catheter encompasses an area 100 times greater than the 500 micron
diameter area impinged by a single laser fiber. Therefore, an array
of 80 to 100 laser fibers would be required to cover the entire
area confronted by a 5.0 millimeter diameter catheter.
The laser microsurgical system 60 shown schematically in FIG. 5 may
also be used with the second embodiment of the catheter 110 of the
invention shown in FIG. 6. Advantageously, the multi-fiber optical
scanner 66 may be programmed to scan each of the laser fibers 118
with pulsed laser energy in a preselected sequence. The scanning
sequence is preferably selected to operate in the conduction-free
or non-heat conducting mode. In that way, the possibility of
overheating and the consequent thermal necrosis of a given
impingement area is avoided, while at the same time the number of
pulses of laser energy that can be delivered to the impingement
area in a given time period is maximized.
Although the laser fibers 118 of the second embodiment of the
invention are described above as extending parallel to the catheter
axis 114, as shown in FIG. 7, the distal ends of the outermost
laser fibers may also be inclined or skewed inwardly toward the
catheter axis by an angular amount identified by reference numeral
122. The amount of skewing may amount to between 5.degree. and
45.degree.. Preferably, the distal ends of the laser fibers 118 are
inserted or molded into an end plate 126 fixed to the sheath 112.
The end plate 126 may also receive the other longitudinally
extending elements of the catheter, such as the viewing element
124, illumination fibers 132, 134, 136 and fluid channels 140, 142,
144.
The above-described skewing of the peripheral laser fibers
advantageously causes the outermost laser energy beams to converge
toward the axis of the body lumen or vessel and thereby provide
further protection against the possibility of perforation of the
luminal wall. Such skewing, however, reduces the total area of
laser illumination of a given diameter of catheter and arrangement
of laser fibers and results in varying degrees of laser beam
overlap depending on the distance between the obstruction and the
distal end of the catheter.
It would be possible to skew the distal ends of some of the
interiorly disposed laser fibers of an array having fiber groups
disposed at varying radial distances from the axis of the catheter.
Such skewing may cause the axes of the fibers to diverge or
converge with the catheter axis so as to achieve overlapping of
laser impingement if desired or to "aim" at areas not impinged by
the laser beam or blind spots caused by the positioning of other
elements in the catheter, such as the elements 124, 132, 134, 136,
142, 144, etc.
According to the method of the present invention, laser energy is
not supplied as continuous wave (CW) laser energy in the thermal
mode to vaporize atheromatous occlusions as in the prior art, but
rather as pulses of 5-200 millisecond duration at a pulse
repetition rate of 1-50 pulses per second and a duty cycle of
between 5 and 50%. The pulse energy is from 150 to 500 millijoules.
The laser source 62 is an argonion laser delivering 20 watts peak
power at wavelengths of about 488 and 514 nanometers and a
preferred spot size of about 100-500 microns diameter. Pulsing of
the laser source in the ranges described above has been
advantageously found to be both safe and effective; safe from the
standpoint that the vessel walls will neither be perforated nor
subjected to thermal necrosis, and effective from the standpoint
that the laser energy is sufficiently great to effect vaporization
of the occlusion.
The selection of specific values for the pulse duration, pulse
repetition rate, pulse energy parameters within the aforesaid
ranges to effect destruction of an occlusion without thermal
necrosis is dependent to a large extent on the thermal time
constant and absorption characteristics of particular type or
material of the occlusion, e.g., fibrin, cholesterol, calcium,
collagen, low-density lipoproteins and the like. Based on the
teachings herein, however, one skilled in the art can readily
select a suitable value for each pulse parameter to effect
conduction-free operation, i.e., destruction of the tissue of the
occlusion with substantially no thermal necrosis of the surrounding
tissue.
Although only preferred embodiments are specifically illustrated
and described herein, it will be appreciated that many
modifications and variations of the present invention are possible
in light of the above teachings and within the purview of the
appended claims without departing from the spirit and intended
scope of the invention.
* * * * *