Note: Descriptions are shown in the official language in which they were submitted.
~ wo 94/17739 2 1 5 ~1 g 7 PCT/US93/12411
ABRASIVE DRIVE SHAFT DEVICE FOR
ROTATTONAL ATHERECTOl\~Y
FIELD OF THE INVENTION
The invention relates to devices and methods for removing tissue from
S body passageways, such as removal of atherosclerotic plaque from arteries,
utilizing a rotary atherectomy device.
BACKGROUND OF THE INVENTION
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 frequentobjective 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 (atheromas) in the intimal layer (under the endothelium) of a
patient's blood vessels. Very 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 thereforeoften are referred to as stenotic lesions or stenoses, the blocking material being
referred to as stenotic material. If left untreated, such stenoses can cause angina,
hypertension, myocardial infarction, strokes and the like.
Several kinds of atherectomy devices have been developed for attempting
to remove some or all of such stenotic material. In one type of device, such as
that shown in U.S. Pat. No. 4,990,134 (issued to Auth), a rotating burr covered
with an abrasive cutting material such as diamond grit (diamond particles or dust)
is carried at the distal end of a flexible drive shaft. The ability of diamond dust
Wo 94/17739 ~ 5~ 2 PcT/uss3/124
covered burrs to remove human soft tissue at high surface speeds (e.g., small
diameter burrs rotated at about 200,000 rpm) has been known for some time and
has been utilized in dentistry since at least the early 1980's to remove soft gum
tissue (see, e.g., "Premier Two Striper~ Gingival Curettage" (Abrasive
Technology, Inc. 1982); "Premier Two Striper~ Crown & Bridge Techniques"
(Abrasive Technology, Inc. 1981); H. Gilmore, et. al, Operative Dentistry (C.V.
Mosby Company 1982, 4th ed.), pp. 64-65, 69, 348-350; R. Tupac, et al., "A
Comparison of Cord Gingival Displacement With the Gingitage Technique,"
Journal of Prosthetic Dentistry, (Nov. 1981, pp.509-515); and Premier Presents
Two Striper~ Dental Diamond Instruments (Abrasive Technology, Inc. 1989).
The burr in the Auth device and in such dental devices is rotated at speeds in the
range of 20,000 to 200,000 rpm or more, which, depending on the diameter of the
burr, can provide surface speeds of the abrasive particles on the burr in the range
of 40 ft/sec. Auth claims that at surface speeds below 40 ft/sec the abrasive burr
will remove hardened atherosclerotic material but will not damage normal elasticsoft tissue of the vessel wall. Auth also admits that at surface speeds above 40ft/sec the abrasive burr will remove both hardened and soft tissue. See, e.g., Pat.
No. 4,990,134 at col. 3, lines 20-23.
Unfortunately, not all atherosclerotic plaques are hardened, calcified
atherosclerotic plaques. Moreover, the mechanical properties of the soft plaquesare very often quite close to the mechanical properties of the soft wall of the
vessel. Thus, one cannot safely rely entirely on the differential cutting properties
of such abrasive burrs to remove atherosclerotic material from an arterial wall,particularly where one is attempting to remove all or almost all of the
atherosclerotic material. See, e.g., Atherectomy~ A Physicians Guide, (StrategicBusiness Development, Inc., 1990), pp. 89, 94-96. Furthermore, in clinical
practice, the Auth burr is virtually always rotated at speeds of at least about
155,000 rpm. At such speeds a diamond dust covered burr with a diameter of
l.5mm achieves a surface speed of 40 ft/sec, the very speed at which the
differential cutting effect becomes limited, at best (i.e., the burr removes both
hard and soft tissue).
~ WO 94/17739 2 I 5 ~1 8 7 PCT/US93/12411
Thus, a significane drawback has been recognized in use of the Auth-type
of burr. Although under some conditions the differential cutting properties of such
burrs are effective to protect healthy tissue, in many circumstances the burr
nevertheless can abrade at least a portion of the healthy tissue, creating a risk of
perforation. This is particularly true at higher rotational speeds. A majority of
atherosclerotic lesions are asymmetrical (i.e., the atherosclerotic plaque is thicker
on one side of the artery than on the other). Moreover, pressure of the burr
against the atherosclerotic plaque is achieved only by the use of a burr having a
diameter slightly larger than the opening through the stenotic passageway. Thus,since the stenotic material will be entirely removed on the thinner side of an
eccentric lesion before it will be removed on the other, thicker side of the lesion,
during removal of the remaining thicker portion of the atherosclerotic plaque the
burr necessarily will be engaging healthy tissue on the side which has been
cleared--indeed, lateral pressure by such healthy tissue against the burr is required
to keep the bulT in contact with the remaining stenotic tissue on the opposite wall
of the passageway. Thus, in clinical practice (balancing safety and residual
stenosis), physicians typically used an undersized burr and are not able to remove
the entire stenosis--e.g., on a patient having a coronary artery with an original
diameter estimated to be 3mm, rarely would a physician use a burr diameter of
more than about 2mm. See, e.g., Atherectomy. A Physicians Guide, (Strategic
Business Development, Inc., 1990), p. 96. These risks are enhanced at high
rotational speeds where the differential cutting phenomenon is significantly
diminished .
Typically, fluoroscopy is utilized to assist the physician in placing the
Auth-type burr in the general location of a stenosis in an artery. This imaging
technique does not provide cross-sectional imaging of the artery and, thus,
significantly limits the ability of the physician to monitor in real-time the actual
removal of stenotic tissue. As a result, the physician's ability to thoroughly
remove the stenotic lesion is limited. Unfortunately, conventional intravascularultrasound imaging equipment, which allows cross-sectional imaging of the
arteries, cannot be used simultaneously with the Auth-type device for two reasons.
First, the Auth burr itself completely occludes the stenotic portion of the artery
wo g~/17739 215 518 7 PCT/US93/12411 ~
; 4
during the procedure and therefore leaves no room for an intravascular ultrasound
catheter to be positioned in the arterial passageway next to the burr. Second, the
Auth-type burr is not sonolucent and therefore will not permit ultrasonic im~ging
from inside of the burr.
S In addition, the Auth device has three drawbacks due to the fact that a
separately manufactured abrasive burr must be attached to (or near) the distal end
of the flexible drive shaft:
(1) First, the connection between the burr and the drive shaft is
critical, in that it must be secure against failure. This requirement
therefore adds to the cost of producing the device.
(2) Second, the size of the burr, particularly the di~meter of the
burr, necessarily limits the ability of the device to safely initiate opening ofvery tight stenotic lesions, particularly those located more distally in
branches of major coronary arteries.
(3) Third, since the burr is made from a solid, inflexible metal,
when it is used in tortuous arteries the length of the burr must be kept
relative!y short in order to allow the burr to navigate the bends and curves
of the artery. For a burr of a given diameter, the length of the burr
defines how rapidly the transition from its smallest diameter (close to the
diameter of the drive shaft) to its maximum diameter must occur. A longer
burr may have a more gently sloping profile, while a shorter burr must
have a steeper profile. Thus, the inflexibility of the Auth-type burr requires
the burr to be relatively blunt.
SUMMARY OF THE INVENTION
The invention provides a rotational atherectomy device that eliminates the
three above-described drawbacks associated with the separate manufacturing and
attachment of a burr for the Auth-type device. It also permits use of intravascular
ultrasound imaging to monitor the removal of stenotic tissue as it is being
removed, thus reducing the risk of perforation, particularly at high rotational
speeds where the differential cutting phenomenon is significantly reduced, and
allowing the physician to more completely remove stenotic tissue without
substantially increasing the risk of perforation.
wo 94/17739 1 $S1~ 7 PCT/US93112411
In one embodiment, the device comprises a rotational atherectomy device
having a flexible, preferably multi-stranded, elongated drive shaft. The drive shaft
includes a proximal segment having a generally constant cross-sectional diameter,
a distal segment also having a generally constant cross-sectional diameter, and an
intermediate segment having an enlarged cross-sectional diameter. This
intermediate segment is comprised of two portions, a proximal portion and a distal
portion. Wire turns of the proximal portion of the drive shaft's intermediate
segment have diameters that progressively increase in diameter distally, and wire
turns of the distal portion have diameters that progressively decrease in diameter
distally. Thus, together the proximal and distal portions form an enlarged
diameter intermediate segment of the drive shaft. A thin layer of abrasive
particles is bonded to the wire turns of a portion (preferably the distal portion) of
the intermediate segment of the drive shaft, thereby defining an abrasive segment
of the drive shaft.
In a second embodiment, the wire turns of the enlarged-cli~mete.r
intermediate segment include a gap (preferably formed by a temporary change in
the pitch of the wire turns) which provides a window in the intermesii~te segment
that is relatively transparent to ultrasonic energy (i.e., a "sonolucent window").
An intravascular ultrasound imaging catheter or an ultrasound imaging guide wirecan be inserted through the lumen of the drive shaft to a position (or incorporated
into the drive shaft at a position) where the ultrasonic transducer elements arealigned with the sonolucent window in the intermediate segment of the drive shaft,
permitting ultrasonic imaging of a cross-section of the stenotic area (including the
thickness and composition of the atherosclerotic plaque), and the relative position
of the abrasive burr with respect to the stenotic tissue. As a result, intravascular
ultrasound imaging permits real-time moniloling of the removal of the stenotic
tissue, allowing the physician to more thoroughly remove the atherosclerotic tissue
without substantially increasing the risk of vascular perforation.
In either embodiment, the drive shaft is generally comprised of a flexible
helically wound multistrand wire coil. The abrasive material may be secured to
the turns of the wire of the drive shaft coil by any suitable bonding material. The
bonding material may be applied so as to not bond adjacent turns of the wire of
WO 9~/17739 ' PCT/US93/12411
21~5~87 6
the drive shaft coil to one another, thereby preserving the flexibility of the drive
shaft throughout the abrasive segment. Alternately, the bonding material may be
applied to the turns of the wire of the drive shaft coil so as to not only bond the
abrasive material to the drive shaft but also to bond adjacent turns of the wire of
the drive shaft coil to one another, thereby forming a generally non-flexible
abrasive segment in the drive shaft.
A significant advantage of the device of the invention is that the diameter
of an abrasive segment of the drive shaft may exceed the diameter of the drive
shaft coil itself by an amount as little as the thickness of a circumferential layer of
diamond particles (typically about 10-30~um thick) and the thickness of a layer of
bonding material (which usually does not exceed about 5-lO~m). Thus, the
overall maximum diameter of the abrasive segment, including the thickness of theabrasive coating, may be only as little as about 25-90,um larger than the maximum
diameter of the wire turns of the abrasive segment of the drive shaft itself.
The invention solves the above-identified drawbacks of the Auth device in
that:
(1) the invention does not require a separately manufactured burr to
be attached to the drive shaft;
(2) the overall diameter of the abrasive segment for a given drive
shaft can be made significantly smaller than an abrasive burr for the same
diameter drive shaft, thereby allowing treatment of extremely tight stenotic
lesions, particularly those located more distally in major coronary arteries
or branches of such arteries;
(3) the abrasive segment can be made flexible and can be made
longer (than an Auth-type burr of the same diameter), thus allowing the
abrasive segment to have a very gently sloping profile, permitting, as a
result, treatment of even very tortuous arteries; and
(4) the invention permits use of intravascular ultrasound imaging to
monitor the removal of stenotic tissue as it is being removed, thus reducing
the risk of perforation, particularly at high rotational speeds where the
differential cutting phenomenon is significantly reduced.
Wo 9J/17739 SSl 8 7 PCT/US93/12411
BRrEF DESCRIPIION OF THE DRAWINGS
Figure 1 is a partially broken away view of the proximal and distal end
portions of one embodiment of the abrasive drive shaft atherectomy device of theinvention, shown somewhat schematically and in longitu~in~l cross-section;
Figure 2 is an enlarged, broken-away view in longitudinal cross-section of
the abrasive drive shaft of the invention, with abrasive material shown somewhatschematically attached to the turns of the wire of the abrasive segment of the drive
shaft, the abrasive material being attached in such a fashion that adjacent turns of
the wire of the abrasive segment of the drive shaft are not secured to one another;
Figure 3 is a view similar to Figure 2, depicting a bushing supporting the
enlarged diameter wire turns of the intermediate segment of the drive shaft;
Figure 4 depicts the flexible abrasive drive shaft atherectomy device of
Figure 3 inserted into a relatively tortuous artery, illustrating the flexibility of the
intermediate segment of the drive shaft of the device, and the resulting benefit that
the abrasive segment can be made somewhat elongated with a gently sloping
profile;
Figure 5 shows another embodiment similar to Figure 2 with bonding
material not only attaching the abrasive material to the turns of the wire of the
abrasive segment but also securing to one another the adjacent wire turns of theabrasive segment of the drive shaft;
Figure 6 is a modified embodiment similar to Figures 2 and 5 with the
bonding material extending over and bonding together wire turns of the entire
intermediate segment, thus making the entire intermediate segment substantially
inflexible;
Figure 7 depicts a modified embodiment similar to Figure 3 but with the
drive shaft having two helically wound layers, the outer layer termin~ting just
proximal to the intermediate segment of the drive shaft;
Figure 8 depicts another modified embodiment similar to Figure 3 but with
the drive shaft having two helically wound layers, the inner layer having a
generally constant diameter throughout its length, and the outer layer having
enlarged diameter wire turns which define the drive shaft's intermediate segment;
wo 94117739 215 ~ 18 7 PCT/USg3/12411 ~
Figure 9 is a partially broken away view of another embodiment of the
invention, similar to Figure 1, with the addition of an intravascular ultrasoundimaging catheter positioned over the guide wire inside the lumen of the abrasivedrive shaft, the abrasive drive shaft being rotatable over the ultrasound catheter;
Figure 10 is an enlarged view of a portion of the abrasive drive shaft of
Figure 8 (abrasive material not shown), illustrating the gap formed by temporarily
changing the pitch of the wire turns of the intermediate segment of the drive shaft;
Figure 11 is a longitudinal cross sectional view of Figure 10, differing
from Figure 10 in that abrasive material (shown somewhat schematically) is shownattached to the turns of the wire of the abrasive segment of the drive shaft;
Figure 12 is a view similar to Figure 11 depicting a sonolucent bushing
supporting the enlarged diameter wire turns of the intermedi~te segment of the
drive shaft;
Figure 13 shows another embodiment similar to Figure 11 with bonding
material not only attaching the abrasive material to the turns of the wire of the
abrasive segment but also securing to one another the adjacent wire turns of theabrasive segment of the drive shaft;
Figure 14 is an enlarged view of a distal portion of the device of the
invention shown in Figure 9, the ultrasound catheter carrying a multi-element
transducer array;
Figure 15 depicts the distal portion of the abrasive drive shaft atherectomy
device of Figure 9 being advanced across a stenotic segment of an artery;
Figure 16 is a cross-sectional view of Figure 15, taken along line 16-16
thereof;
Figure 17 represents the instantaneous cross-sectional ultrasound image
corresponding to Figure 16;
Figure 18 represents the electronically reconstructed composite cross-
sectional ultrasound image corresponding to Figure 16;
Figure 19 shows an embodiment similar to Figure 14, but with a rotatable
ultrasound catheter carrying two transducer elements oriented 180 from one
another, and with the distal segment of the drive shaft having a smaller di~meter
than the proximal segment and being rotatable directly over the guide wire;
WO 94/17739 ~ PCTrUS93/12411
Figure 20 shows an embodiment similar to Figure 19, but with a single
transducer element ultrasound catheter being secured to the abrasive drive shaftand being rotatable together with the drive shaft;
Figure 21 shows another embodiment similar to Figure 14, but with a
rotating acoustic reflector type of ultrasound catheter; and
Figure 22 shows another embodiment of the invention similar to Figure 14,
but with the drive shaft having two helically wound layers, the outer layer
termin~ting just proximal to the intermediate segment of the drive shaft.
T~EST MODE FOR CARRYTNG OUT T~TE TNVENTTON
Although the drawings illustrate use of the abrasive drive shaft device of
the invention in connection with removal of atherosclerotic plaques in arteries, the
device is usable in other capacities, wherever tissue or obstructions are desired to
be removed from body passageways, cavities, or any organ or organ system of the
body.
Figure 1 illustrates the principal components of one embodiment of the
device. An elongated catheter 20 with a distal end 22 includes a lumen 26. In
this lumen 26 of the catheter 20, a helically wound flexible drive shaft 50 is
disposed.
The drive shaft 50 preferably is multi-stranded. For the sake of clarity the
drawings depict mono-filar or bi-filar drive shafts, in practice multi-filar drive
shafts--particularly bi-filar or tri-filar drive shafts--may be plererled, but the
principles illustrated in the drawings are equally applicable regardless of the
number of wire strands making up the drive shaft. The drive shaft includes a
proximal segment 57 having a generally constant cross-sectional diameter, a distal
segment 59 also preferably having a generally constant cross-sectional diameter, and an intermediate segment 58 having an enlarged cross-sectional diameter. Thisintermediate segment may be considered to have two portions, a proximal portion
58a and a distal portion 58b. To achieve the enlarged ~ meter of the intermediate
segment 58, wire turns of the proximal portion 58a of the drive shaft's
intermediate segment have diameters that progressively increase in diameter
distally, and wire turns of the distal portion 58b have diameters that progressively
wo 94/17739 2 15 5 18 7 ` PCT/US93/12411 ~
decrease in diameter distally. Thus, together the proximal and distal portions 58a
and 58b define an enlarged ~ nçter interm~i~te segment of the drive shaft.
A thin, flexible sheath 54 made from polytetrafluoroethylene (i.e.,
TEFLON'19), or a similar low-friction material, may be provided, encasing at least
two relatively short portions of the proximal segment of the drive shaft (one just
proximal to the intermediate segment, and the other at the proximal end of the
drive shaft). If desired, this sheath 54 may be extended to cover subst~nti~lly the
entire portion of the drive shaft 50 proximal to the intermediate segment 58. Ifdesired, the distal segment 59 of the drive shaft 50 may also be coated with a
TEFLON~D sheath (not shown in the drawings). In addition to, or in lieu of, the
outer TEFLON~9 sheath 54, the wire from which the helically wound drive shaft
50 is manufactured may be coated with a very thin layer (e.g., 0.0002-0.0004
inches) of TEFLONG before it is helically wound, resulting in a drive shaft
entirely coated with flexible TEFLON~D. Rotation of such a TEFLON$ coated
drive shaft over a TEFLON'I9 coated guide wire 90 provides a very low friction
TEFLON'I9-TEFLON'~9 interface between the drive shaft and the guide wire and
facilitates the use of higher rotational speeds.
A thin layer of abrasive particles 44 (shown somewhat schematically in the
drawings) is bonded to the wire turns 52 of a portion (preferably at least the distal
portion 58b) of the intermediate segment 58 of the drive shaft 50. The portion of
the drive shaft covered with such abrasive particles 44 is referred to generally as
the abrasive segment 40.
Preferably the abrasive particles are distributed over at least the distal
portion 58a of the intermediate segment 58, and preferably this distal portion 58a
of the intermediate segment 58 has a generally gently sloping profile so that the
abrasive segment 40 engages the stenotic tissue somewhat gradually as the drive
shaft is advanced in the artery. Other distributions of abrasive particles, and other
shapes for the intermediate segment 58, can also be easily provided, as desired for
a particular application. For example, coarser abrasive particles can be bonded on
the more distal wire turns of the abrasive segment 40, and finer (polishing)
abrasive particles can be bonded on the more proximal wire turns of the abrasivesegment 40.
WO 9-117719 187 , PCT/US93/12411
The lumen 56 of the flexible drive shaft 50 is sized to receive a
conventional guide wire 90 having an elongated shaft 92 and a conventional
helically wound distal tip portion 94, terminating in a rounded tip 96. The guide
wire 90 can be provided with a slippery surface coating such as TEFLON~,
S silicone, a combination of silicone over TEFLON~, or similar slippery materials.
A particularly slippery surface can be obtained by uti1i7ing PHOTOLIN~ brand
surface modification commercially available from Bio-Metric Systems, Inc. of
Eden Prairie, Minnesota. The shaft of the guide wire 90 may be made of a shape-
memory alloy, such as nitinol. The fabrication of the guide wire shaft from sucha shape-memory alloy assures that the guide wire will not kink. The use of nitinol
may also be advantageous compared to stainless steel in that nitinol will betterdampen oscillations in the drive shaft.
The proximal segment 57 of the drive shaft 50 is disposed in a flexible
catheter 20. The catheter 20 can be made from conventional catheter materials,
including flexible thermoplastic or silicone materials. For example, the catheter
preferably is made from a slippery material such as TEFLON~. If necessary, the
catheter 20 can be reinforced with an outer layer made of nylon or other similarmaterials having desirable torque transmitting characteristics. Thin wire braiding
along substantially the entire length of the catheter may be also utilized if desired.
The proximal portion of the catheter 20, as shown in the lower half of
Figure 1, is secured to a housing 34. A turbine 35 (or equivalent source for
rotational motion) is secured to a turbine mount 37 slidably received in the
housing 34. Relative longitudinal sliding movement of the turbine mount 37 with
respect to the housing 34 is permitted, and, when it is desired to lock the
longitudinal position of the turbine 35 and turbine mount 37 with respect to thehousing 34, wing nuts 38 can be tightened on threaded bolts 39 (which extend
from the turbine mount 37 through slots 36 in the housing 34).
The turbine 35 is connected by way of turbine link 64 to the flexible drive
shaft 50. A conventional seal 66 may be provided against the outer surface of the
turbine link 64, preventing fluid from escaping from the cavity 65 while permitting
rotational and longitudinal movement of the flexible drive shaft 50 and the turbine
link 64. A side port 67 may be provided to permit infusion of lubricating fluid
Wo 94/17739 ~`l S~ 187 PCT/US93/12411
12
(such as saline or glucose solutions and the like) or radio-opaque contrast solutions
into the cavity 65 and the lumen 26 of the catheter 20. The side port 67 could
also be connected to a vacuum source for aspiration of fluid through the catheter
lumen 26. Means may also be provided for infusing flushing fluid into the lumen
56 of the drive shaft 50 (around the guide wire 90). This may be accomplished,
e.g., by coating the drive shaft with the TEFLON~ sheath 54 only over a
relatively short length of the drive shaft proximal to its intermediate segment 58
and over a relatively short length at the proximal end of the drive shaft.
Alternately, perforations or other suitable openings may be provided in the
TEFLON~ sheath 54. In either case, such flushing fluid is allowed to flow
between the wire turns 52 of the drive shaft 50 and into the lumen 56 of the drive
shaft 50.
Set screw 61 is provided to selectively permit or prevent relative
longitudinal movement of the guide wire 90 with respect to the housing 34. If the
set screw 61 is loosened, the guide wire 90 can be advanced and retracted with
respect to the housing 34 and the catheter 20. Alternately, tightening of set screw
61 against the guide wire 90 will prevent relative longitudinal movement of the
guide wire 90 with respect to the housing 34 and catheter 20. With wing nuts 38
loosened, the turbine 35, turbine link 37 and drive shaft 50 (with its abrasive
segment 40) can be moved longitudinally with respect to the guide wire 90,
housing 34 and catheter 20. A guide wire handle 62 can be secured to the
proximal end portion of the guide wire 90 by set screw 63 to facilitate
manipulation of the guide wire 90.
Although the means for securing the guide wire 90, the turbine mount 37,
and the housing 34 with respect to one another are illustrated in the drawing asbeing accomplished by use of wing nuts 38, and set screw 61, it will be
appreciated that other conventional means or mechanisms (such as cam friction
fittings, and the like) may easily be employed. Such cam friction fittings, etc.,
may also be used to attach the guide wire handle 62 to the guide wire 90.
Moreover, the connection of the proximal end of the catheter 20 to the housing 34
(accomplished here by connector 33) and the side port 67 are shown somewhat
wo 94/17739 ~187 I~CT/U593/12411
schematically -- any of a variety of conventional fittings that are readily
commercially available or adaptable for this purpose may easily be employed.
Figures 2-6 illustrate in enlarged, somewhat schematic fashion several
alternate embodiments of the intermediate segment 58 of the drive shaft.
Referring first to Figure 2, abrasive particles 44 are secured to the turns or
windings 52 of the drive shaft's abrasive segment 40 by a bonding material 48.
The bonding material 48 has been applied to the turns of the wire of the drive
shaft 50 in a fashion that effectively secures the abrasive particles 44 to the wire
turns 52 of the drive shaft without securing the wire turns 52 of the drive shaft to
one another. This provides the abrasive segment 40 of the drive shaft 50 with
essentially the same degree of flexibility as the rest of the drive shaft.
The method for attaching the abrasive particles 44 to the surface of a the
drive shaft may employ any of several well known techniques, such as
conventional electroplating, fusion technologies (see, e.g., U.S. Pat. No.
4,018,576), brazing, adhesives and the like. The abrasive particles 44 themselves
may be of any suitable composition, such as diamond powder, fused silica,
titanium nitride, tungsten carbide, aluminum oxide, boron carbide, or other
ceramic materials. Preferably they are comprised of diamond chips (or diamond
dust particles). Abrasive materials of these types have been used in a variety of
medical/dental applications for years and are commercially available. Attachmentof abrasive particles to the wire turns of the drive shaft is also commercially
available from companies such as Abrasive Technologies, Inc. of Westerville,
Ohio.
Figure 3 depicts a bushing 81 supporting the enlarged diameter wire turns
of the intermediate segment 58 of the drive shaft. Such a bushing can be made ofvarious suitable metals or plastics. Preferably it is made of a flexible material,
thereby maintaining lateral flexibility in the intermediate segment 58. Also,
- desirably at least the surface of the bushing lumen 82 is made of (or coated with) a
low friction material (e.g., TEFLON~) to reduce friction between the bushing 81
and the guide wire 90, a particularly important feature when external radial forces
on the intermediate segment are not symmetrical as the device is being used to
remove stenotic tissue (particularly eccentric stenotic lesions in tortuous arteries).
wo 94/17739 ~l S 5 ~ 87 PCT/US93/12411 --
14
Figure 4 illustrates the advantage of the embodiment of Figure 3 when used
in tortuous arteries. In this drawing, the abrasive segment 40 of the drive shaft is
being advanced, over the guide wire 90, across a stenosis 12 in a tortuous artery
10, removing stenotic tissue as it is advanced. The flexibility of the interme~ te
segment 58 (including the bushing 81) allows the device to follow the curves andbends of tortuous arteries. Moreover, since the intermediate segment 58 is
flexible, the abrasive segment 40 can be made relatively longer than traditionalAuth-type rigid burrs of the same diameter, thereby presenting a very gently
sloping profile of the abrasive segment, without sacrificing the ability to travel
through narrow, tortuous arteries. Such a profile allows the abrasive segment 40to engage the stenotic tissue 12 somewhat more gradually than the more blunt
Auth-type burr.
Figure 5 shows a somewhat different embodiment in that bonding material
48 is applied over the entire outer surface of the abrasive segment 40 of the drive
shaft 50, thereby not only bonding the abrasive particles 44 to the wire turns 52 of
the drive shaft 50, but also securing adjacent wire turns 52 of the drive shaft to
one another, creating a relatively rigid abrasive segment 40 in the otherwise
flexible drive shaft 50. In this embodiment the proximal portion 58a of the
intermediate segment 58 remains flexible.
Figure 6 is a modified embodiment similar to Figure 5 with the bonding
material 48 not only attaching the abrasive material 44 to the wire turns 52 of the
abrasive segment 40 of the drive shaft 50 but also securing the wire turns 52 ofthe entire intermediate segment 58 of the drive shaft 50 to one another. Thus,
although the abrasive segment 40 extends through only the distal portion 58a of
the intermediate segment 58, the entire intermediate segment 58 is rendered
substantially inflexible by the bonding material 48.
Although Figures 1-6 illustrate a single layer helically wound drive shaft 50
(which may be mono-filar but preferably is multi-filar), a multi-layer helicallywound drive shaft may also be utilized, as depicted in Figures 7-8. In such a
drive shaft 50 a second, outer coaxial layer (either mono-filar or, preferably,
multi-filar) of helically wound wire is utilized. In the embodiment shown in
Figure 7, the outer layer 55 extends only throughout the proximal segment 57 of
WO 94/17739 ~5 1~7
the drive shaft, terminating just proximal to the intermediate segment 58 of thedrive shaft. The inner layer 52 continues for the full length of the drive shaft,
expanding in diameter to define the intermediate segment 58 of the drive shaft.
In the embodiment shown in Figure 8, the outer layer 55' extends for
substantially the entire length of the drive shaft, expanding in diameter to define
the intermediate segment 58 of the drive shaft. The inner layer 53' preferably
does not expand in diameter in the intermediate segment, but has a substantiallyconstant cross-sectional diameter throughout its length. In this embodiment a
toroidal collar 85 may be provided to support the wire turns of the intermeAi~tesegment 58 of the outer layer 55'. This collar may be made of metal (e.g.,
stainless steel) or, preferably, suitable flexible plastics (e.g., TEFLON~). Since
the collar 85 is effectively encapsulated by the inner and outer wire layers 53' and
55', attachment of the collar to the drive shaft is not critical.
In both of the embodiments of Figures 7 and 8, typically the wire layers
are helically wound in opposite directions so that upon application of torque to the
proximal end of the drive shaft 50 (when the turbine or other rotational power
source is actuated in a predetermined rotational direction) the outer wire layer 55
will tend to radially contract and the inner wire layer 52 will tend to radiallyexpand, the two wire layers thus supporting one another and preventing a decrease
of the inner diameter and an increase of the outer diameter of the drive shaft.
Although for ease of illustration the drawings depict the wire of both layers
of the two-layer drive shaft 50 to be of the same diameter, in practice it may be
desirable to make one of the layers from a wire having a slightly larger diameter
than the other. For example, if one of the layers is made from 0.004" diameter
wire, the other wire may desirably be made from 0.005" diameter wire.
Moreover, while the drawings depict the wire of the drive shaft 50 to be
generally round in cross-section, it will be appreciated that wires of other shapes,
- such as flattened rectangular, oval, etc., could also be utilized. For example, use
of flattened rectangular wire (typically with rounded corners) will provide eachindividual wire turn of the abrasive segment with more surface for the fixation of
diamond particles to these individual wire turns, allowing one to maintain
relatively small diameters of the proximal and distal segments of the drive shaft.
wo 94/17739 21~ S ~ 8 7 pcTluss3ll24ll ~
16
Such flattened rectangular wire can be of any suitable dimensions. For example,
wire having a cross-sectional height of about 0.002-0.008 inches, and a width ofup to about three to five times the height may be utilized. Stainless steel wire of
this type is commercially available from various sources, including the Wire
Division of MicroDyne Technologies (New Britain, CT).
It will be appreciated that the representations in Figures 2-8 are somewhat
schematic. In many of the views the abrasive particles 44 are shown as being
attached in neat rows centered along the wire turns 52 of the drive shaft 50.
Depending on the method of applying the abrasive particles 44, the particles more
likely will be distributed somewhat randomly over the abrasive segment (or wire
turns) of the drive shaft. Moreover, the relative size of the abrasive particles in
relation to the diameter of the wire of the drive shaft coil may vary from one
application to another. For example, in a typical coronary application (i.e., use in
coronary arteries) round wire having a diameter of about 25-150~m (and
preferably of about 50-125~m) may be wound into a drive shaft 50 having a
proximal segment 57 with an outer diameter of about 0.2-l.Smm (and preferably
about 0.3-1.2mm); the intermediate segment 58 of such a device desirably has a
maximum outer diameter not more than about four times larger than the diameter
of the proximal segment 57 (and preferably not more than about 2-3 times larger
than the diameter of the proximal segment 57). Abrasive particles 44 in the range
of about 5,um to about 30~m (and preferably from about lO~m to about 25~m) are
secured to the wire turns 52 of the drive shaft 50 with a bonding material 48
having a thickness of from about 3~1m to about 15~m. This thickness (3-15,um) ofbonding material represents only the thickness of that portion of the bonding
material which may be located between the particles 44 and the wire turns 52 of
the drive shaft 50. Thus, the "effective thickness" of the abrasive material,
including both the abrasive particles 44 and the bonding material 48, may be in the
range of about 8~m to about 45~m, and preferably in the range of about 15~um to
about 35flm.
Both the single layer and the two-layer multistrand helically wound flexible
drive shafts described above are preferably made from stainless steel wire and can
o 94/17739 ~187 PCT/U593112411
be obtained from commercial sources such as Lake Region Manufacturing Inc.
(Chaska, Minnesota). Other suitable alloys may also be used.
In a procedure, utili7ing the abrasive drive shaft of the invention to
remove stenotic tissue from an artery, a guide wire 90 is first advanced throughS the artery to a position where its distal tip 96 is located distally of the stenosis.
The catheter 20 and the flexible drive shaft 50 with its abrasive segment 40 arethen advanced over the shaft 92 of the guide wire 90 to a position locating the
abrasive segment 40 just proximal to the stenotic lesion 12.
At this point, the flexible drive shaft 50 with its abrasive segment 40 is
rotated at relatively high speed and is advanced distally across the stenosis toinitiate the removal of the stenotic lesion. The speed of rotation typically is in the
range of about 30,000 RPM to about 600,000 RPM, or even more, depending
only on the physical dimensions and capabilities of the turbine/motor and flexible
drive shaft. Typically the procedure will begin with a drive shaft having an
intermediate segment with a maximum cross-sectional diameter larger than the
proximal segment of the drive shaft and larger than the vascular opening throughthe stenosis but smaller than the normal, healthy diameter of the artery. Once the
abrasive segment of the drive shaft has been advanced and retracted through the
stenosis to open the stenosis to a diameter equal to the maximum diameter of theintermediate segment of the drive shaft, the drive shaft and catheter can be
removed and a drive shaft with a larger rli~meter intermediate segment can be
reinserted over the guide wire to continue removing stenotic tissue. In a typical
procedure devices with drive shafts of two or three progressively larger
intermediate (abrasive) segment diameters may be utilized to open the artery to a
diameter close to its original, healthy diameter.
Commercially available angioplasty equipment (e.g., arterial puncture
needles, arterial dilators, sheath introducers and guide catheters) and routine
- angioplasty techniques are used to applop,iately position and manipulate the
abrasive drive shaft device in the above-described interventional procedure. Theabove-described procedure should also utilize conventional fluoroscopic imaging
techniques (with or without radio-opaque contrast solution injections), and the
longitudinal positioning of the device within the artery may be assisted by placing
wo94117739 2155187 PCT/USs3/12411 ~
18
special radio-opaque markings on the elements of the device and/or preferably
components of the device can themselves be manufactured from radio-opaque
materials.
Figures 9-22 illustrate an alternate embodiment of the invention in which an
intravascular ultrasonic im~ging probe (im~ging catheter) 100 is utilized to image,
in real time, the removal of stenotic tissue from the artery (or other body
passageway). In this embodiment (referring now to Figure 9), an ultrasonic
catheter 100 is advanced over the guide wire 90 within the lumen 56 of the
flexible drive shaft 50 to a position locating the catheter's ultrasound transducer
elements 102 in alignment with an opening or gap 84 in the wire turns 52 of the
intermediate segment 58 of the drive shaft 50. The proximal end portion of the
ultrasound imaging catheter 100 may be selectively secured to the housing 34 by a
suitable set screw 69 (or equivalent mech~ni~m), so that the longitudinal position
of the ultrasound imaging catheter with respect to the drive shaft 50 can be
adjusted and then secured. Electrical connection of the ultrasonic imaging catheter
100 to the ultrasound machine (not shown) is made by cable 101. If necesc~ry, a
special port may be provided in the proximal portion of the ultrasound im~ging
catheter 100 for infusing lubricating fluid (such as saline or glucose solutions and
the like) around the guide wire 90.
The ultrasound transducers elements 102 emit ultrasonic waves 103.
Waves 103a emitted by ultrasonic transducers which are acoustically aligned withthe opening or gap 84 will pass through that gap 84, and be reflected by the
sulTounding tissue, thereby providing data for generation of a visual image of such
tissue. Waves 103b emitted by ultrasonic tr~n~ducers which are aligned across
from the wire turns 52 of the abrasive drive shaft 50 will be reflected by the wire.
As illustrated in Figures 10 and 11, this gap 84 in the wire turns 52 of the
drive shaft's intermediate segment 52 may be formed by providing the wire turns
52 of a short portion (typically about one turn) of the intermecli~te segment 58with a pitch L2 that is larger than the pitch Ll of the wire turns of the intermediate
segment 58 just proximal and distal to this short portion. This temporary changein pitch forms a gap 84 (having a width "W") between adjacent bi-filar turns of
the drive shaft coil. Although the drawings depict the temporary transition from
Wo 94/17739 . ~ PCT/US93/12411
19
pitch Ll to pitch L2 in the center of the intermediate segment 58 of the drive shaft
50, it may be located at any convenient portion of the drive shaft--locating it close
to or in the abrasive segment 40 provides what is likely to be the most useful
image (i.e., at the point where stenotic tissue is being removed). Moreover, if the
gap 84 (and consequently the ultrasound transducers 102 of the ultrasound catheter
100) is located at the point of greatest ~ meter of the intermediate segment 58 of
the drive shaft 50, the physician will be able to monitor the thickness of the
stenotic tissue at this point of maximum di~meter, and will be able to more
accurately determine whether additional stenotic tissue can be removed without
substantially increasing the risk of perforation of the artery wall.
For clarity, the abrasive material bonded to the turns of the drive shaft 50
is not shown in Figure 10 -- Figure 11 is a longitudinal cross sectional view ofFigure 10 differing from Figure 10 in that abrasive material (shown somewhat
schematically) is depicted on the turns of the wire of the abrasive segment of the
drive shaft. Notice that the larger pitch L2 need extend for only about one turn of
the wire to create the desired gap.
Figures 12 and 13 illustrate additional embodiments of a drive shaft with an
ultrasonic window or gap in the intermediate segment of the drive shaft. In Figure
12 the intermediate segment 58 is provided with a bushing 81' (similar to Figure3). The bushing 81' of Figures 12, 14-16, 19, 21 and 22 differs from the bushing81 of Figure 3 in that it is sonolucent (i.e., relatively transparent to ultrasound
waves, minimally reflecting or attenuating ultrasonic energy). Materials such assilicone, latex as well as certain plastics (e.g., polyethylene) are suitable for such a
sonolucent bushing 81'. Desirably at least the surface of the bushing lumen 82' is
made of (or coated with) a low friction, sonolucent material to reduce friction
against the outer surface of the ultrasonic catheter 100 as the drive shaft 50 and
bushing 81' rotate around the ultrasound catheter.
In Figure 12 the bonding material 48 (which attaches the abrasive particles
44 to the wire turns 52 of the abrasive segment 40) is applied so as not to bondadjacent wire turns 52 to one another, thus preserving (to the extent permitted by
the flexibility of the bushing 81') the flexibility of the abrasive segment 40. In
Figure 13 the bonding material 48 is applied continuously over the abrasive
wo 94/17739 215 518 7 PCT/USg3/12411 ~
segment 40 to secure adjacent wire turns 52 to one another, thus making the
abrasive segment 40 generally inflexible.
As illustrated in Figure 14, an intravascular ultrasound imaging catheter
100 may be advanced over the guide wire 90 through the lumen 56 of the abrasive
drive shaft 50 to a position where the transducer elements 102 (depicted
schematically) of the ultrasound catheter 100 become acoustically aligned with the
ultrasound window or gap 84 in the wire turns 52 of the intermediate segment 58
of the abrasive drive shaft 50 for use in ultrasonic imaging during the removal of
the stenotic tissue. In this position the ultrasound catheter 100 will permit im~ging
of the relative cross-sectional position of the abrasive segment 40 of the drive shaft
50 with respect to the stenotic tissue, and imaging of the stenotic tissue as it is
being removed.
Figures 15-18 illustrate both the utility of this imaging technique and the
cross-sectional ultrasonic image of the artery through the gap or sonolucent
window 84 between wire turns 52 of the abrasive segment. Figure 15 shows, in
longitudinal cross section, an artery 10 with an eccentric atherosclerotic lesion 12
partially obstructing blood flow in an artery 10. The abrasive drive shaft device
of the invention together with the ultrasonic imaging catheter 100 has been
partially advanced across the stenosis and has removed the proximal portion of an
inner layer of atherosclerotic plaque 12. The ultrasound imaging elements 102 ofthe intravascular ultrasound im~ging catheter 100 have been longitu-1in~lly aligned
with the ultrasonic window 84 in the intermediate segment 58 of the abrasive drive
shaft 50. Figure 16 shows in transverse cross-section the alignment of these
components.
Ultrasonic waves 103a, generated by the ultrasonic transducer elements 102
positioned across from the ultrasonic window 84, pass through the ultrasonic
window 84 and are reflected by surrounding tissues (atherosclerotic tissue 12 and
the wall of the artery 10). The ultrasonic waves 103b generated by the ultrasound
transducers 102 positioned across from the metallic wire turns 52 are totally
reflected by those wire turns 52, producing a bright line 52' of ultrasound echoes
on the instantaneous cross-sectional ultrasound image depicted in Figure 17.
Wo 94/17739 5~0;~ PCT/US93/124
21
Figure 17 illustrates the expected instantaneous cross-sectional ultrasound
image generated by the intravascular ultrasound imaging catheter 100. As
discussed above, ultrasonic waves 103a, generated by the ultrasonic transducer
elements 102 positioned across from the ultrasonic window 84, pass through the
ultrasonic window 84 and are reflected by atherosclerotic tissue 12 and the wall of
the artery 10, producing cross-sectional ultrasonic images of the plaque 12' and of
the wall of the artery 10'. At the same time, the ultrasonic waves 103b which
encounter the wire turns 52 of the abrasive drive shaft S0 will be completely
reflected from the metallic wire and will produce only a bright line 52' of strong
ultrasonic echoes corresponding to the surface of these metallic wires 52 with
"black" shadow 109 outward of this bright line of echoes 52'.
The rotation of the drive shaft 50 and, hence, the ultrasonic window around
the ultrasonic catheter 100, allows electronic reconstruction of a complete cross-
sectional ultrasonic image of the artery shown on Figure 18. This reconstructed
ultrasonic image shows the depth of the atherosclerotic lesion 12", the walls of the
artery 10" and, in general, the location of the abrasive drive shaft with respect to
stenotic tissue and the wall of the artery. Viewing the ultrasound image,
therefore, permits accurate selection of the diameter of the abrasive segment 40for maximum removal of atherosclerotic tissue from within the artery, for
continuous monitoring of the stenotic lesion removal throughout the procedure and
thus allows removal of more of the stenotic lesion without significantly increasing
the risk of perforation.
Two variations of the procedural techniques for utili7ing the abrasive drive
shaft device of the invention are as follows.
When, after injecting radiographic contrast into the stenotic artery (and
imaging the stenosis fluoroscopically), a physician is still not sure whether the
abrasive drive shaft atherectomy device of the invention is suitable for treatment of
- a stenosis, then, prior to advancing the abrasive drive shaft 50 across the stenosis
12, physician may advance the intravascular ultrasonic imaging catheter 100 overthe guide wire 90 ahead of the abrasive drive shaft to "scout" the area of the
stenosis. This enables the physician to further evaluate whether the device of the
invention is likely to be effective in removing the stenotic tissue, to further assess
2~ S5~ 87
WO 94/17739 .; PCT/US93/12411
22
the severity of the lesion in the artery, to better determine whether the lesion is
calcified, whether it is eccentric or symmetrical, and to better determine the
ap~ropliate rli~meter of the abrasive drive shaft (i.e., the diameter of the
intermediate segment of the drive shaft) which should be utilized to initiate the
opening of the stenosis. At this time the entire strategy for the opening of thestenosis can be determined, including such things as which diameter abrasive drive
shafts should be used, and in what sequence, to remove as much of the stenosis as
possible, as efficiently as possible, and as safely as possible.
When, on the other hand (after injecting the radiographic contrast into the
stenotic artery), the physician has determined that the stenotic lesion is of the type
that can be successfully treated with the device of the invention, then the physician
can advance the ultrasonic catheter 100 and the abrasive drive shaft 50 into theartery as a unit, stopping just proximal to the stenosis. The ultrasound catheter
100 can then be advanced to image the area to be treated, and then withdrawn to
its position in the intermecli~te segment 58 of the drive shaft 50, and the entire unit
can then be advanced to commence the stenosis removal procedure.
The above-described procedures for utili7ing the device of the invention are
only illustrative of the use of the invention, and a number of other procedural
techniques may be utilized, as the physician deems app-opliate.
Figure 19 depicts a modified embodiment of the invention where, instead
of an array of ultrasound transducers, the ultrasound c~theter 100' is provided with
two transducers 102', the ultrasound catheter being rotatable within the drive shaft
50 to produce the desired image. Typically the speed of rotation of the
intravascular ultrasound imaging catheter 100' will be somewhat less than the
speed of rotation of the drive shaft, and separate means is therefore provided
proximally for rotating this ultrasound catheter.
Figure 20 depicts another variation where a single ultrasonic transducer
element 102" is provided on the ultrasound im~ging catheter 100", and the catheter
itself is attached to and rotates together with the drive shaft. The sonolucent
bushing 81" in this embodiment is secured directly to both the wire turns 52 of the
intermediate segment 58 of the drive shaft and the distal portion of the ultrasound
imaging catheter 100", and thus does not actually function as a bushing, but
~ivo 9~/17739 ~$$,~ PCT/US93/1~411
supports the wire turns 52 of the intermediate segment 58. In this embodiment the
ultrasonic transducer element is located in direct acoustic alignment with the gap
in the wire turns of the drive shaft. Since the drive shaft may be rotated at speeds
higher than may be desired for purposes of ultrasound imaging, in operation the
speed of the drive shaft 50 may be periodically reduced to a lower speed selected
for operation of the intravascular ultrasonic transducer 102".
Figure 21 depicts yet another embodiment utili7ing an intravascular
ultrasound imaging catheter 100"' having a rotating acoustic reflector (acousticmirror) 104 which radially redirects ultrasound imaging waves 103 (and returningecho waves) emitted (and received) by the non-rotating ultrasonic transducer 105.
(An intravascular ultrasonic imaging probe utilizing an ultrasonic transducer and
an acoustic reflector which are rotatable together as a unit inside the drive shaft
may also be utilized.) The ultrasound imaging catheter 100"' is positioned
longitudinally within the drive shaft 50 so that the acoustic reflector 104 is aligned
with at least a portion of the gap or window 84 in the intermediate segment 58 of
the drive shaft.
The above-described intravascular ultrasound imaging devices are generally
commercially available, e.g., from Cardiovascular Imaging Systems, Inc.
(Sunnyvale, California), Boston Scientific Corp. (Watertown, Massachusetts),
Endosonics, Inc. (Pleasanton, California), and Intertherapy, Inc. (Santa Ana,
California). To the extent that ultrasonic imaging guide wires become
commercially available, they could easily be used in lieu of the conventional guide
wire and intravascular ultrasound imaging catheter depicted in the drawings.
Figure 22 illustrates yet a further variation of the device of the invention.
This embodiment combines the two-layer drive shaft depicted in Figure 7 with theintravascular ultrasound imaging techniques described above. Although the
particular intravascular ultrasound imaging catheter 100 illustrated in this drawing
- is the array-type, any of the other types described above could also be utilized.
While a preferred embodiment of the present invention has been described,
it should be understood that various changes, adaptations and modifications may be
made therein without departing from the spirit of the invention and the scope ofthe appended claims.
