Guide wire brake

Details Guide wire brake Guide wire brake

2000-07-24

2003-01-07

Jacyna, J. Casimer (Department: 3751)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C606S159000, C606S167000, C606S180000

Reexamination Certificate

active

06503227

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to medical devices used to differentially ablate or cut deposits from within a patient's vasculature, and in particular to guide wire braking mechanisms for such medical devices.
BACKGROUND OF THE INVENTION
A variety of techniques and instruments have been developed for removing health-threatening deposits in a patient's arteries and similar body passageways. Such deposits may be caused by a number of diseases such as arteriosclerosis, a condition characterized by the buildup of deposits (atheromas) in the intimal layer of a patient's blood vessels. If the atheroma has hardened into a calcified atherosclerotic plaque, removal of the deposit can be particularly difficult. Deposits in the vasculature can restrict the flow of blood to vital organs, such as the heart or brain, and can cause angina, hypertension, myocardial infarction, strokes, and the like.
Several kinds of atherectomy devices have been developed for removing such deposits. One such device that is particularly suited to removing calcified atherosclerotic plaque, is an ablative rotational atherectomy device, such as that disclosed in U.S. Pat. No. 4,990,134 by Auth. Auth teaches using a small burr covered, or partially covered, with an abrasive cutting material, such as diamond grit. The burr is attached to the distal end of a flexible, rotatable drive shaft. A rotational atherectomy device practicing the Auth invention is sold by the assignee of the present invention under the trademark Rotablator® and is described below.
The Rotablator® ablative device
10
, depicted in
FIG. 1
, utilizes a guide wire
26
that is inserted through the patient's body approximately to the location of the deposit that is to be treated. A hollow, flexible drive shaft
22
having an ablative burr
24
at its distal end is then inserted over the guide wire
26
, and advanced to a location just proximal to the deposit. The drive shaft
22
is covered with a lumen or catheter
20
along most of its length to minimize the impact to surrounding tissue when the drive shaft
22
is rotatably engaged. The drive shaft
22
is connected to a compressed-air driven drive assembly
16
having a turbine (not shown) that can rotate the drive shaft
22
at relatively high rotational speeds, typically in the range of, e.g., about 150,000 to about 190,000 rpm. The drive assembly
16
is slidably mounted in an advancer housing
12
on a track
32
, allowing a surgeon using the device
10
to move the drive assembly
16
transversely, and hence move the drive shaft
22
and burr
24
forward and backward to ablate the atheroma. When the turbine is engaged, that is, when compressed air is being supplied to the drive assembly
16
, a guide wire brake
50
normally clamps onto the guide wire
26
, preventing the guide wire
26
from rotating or moving laterally while the drive shaft
22
is rotating.
A prior-art guide wire brake
50
for an ablative rotational atherectomy device is shown in FIG.
2
A. This prior art guide wire brake
50
comprises a brake collet
52
axially supported in a brake cylinder
56
containing a free piston
54
with a lip seal
55
. The guide wire
26
runs axially through the collet
52
, cylinder
56
, and piston
54
. As seen most clearly in
FIG. 2B
, the brake collet
52
is an elongate member having an upper portion
41
disposed opposite an identical lower portion
42
. The upper and lower portions
41
,
42
are separated by a narrow gap
47
along most of the length of the brake collet
52
. The brake collet
52
has a tubular back portion
45
and a head portion
46
wherein the head portion
46
upper and lower portions
41
,
42
generally form a pair of abutting truncated cones that are coaxial with the back portion
45
. The gap
47
separating the upper portion
41
from the lower portion
42
extends entirely through the head portion and most of the way through the back portion
45
, wherein interior flat faces
49
on the upper and lower portions
41
,
42
are disposed on either side of the gap
47
. A narrow strip of the back portion
45
connects the upper portion
41
to the lower portion
42
, elastically biasing the upper portion
41
and lower portion
42
in an “unclamped” position wherein the gap is wider than the diameter of the guide wire
26
.
As shown in
FIG. 2A
, the piston
54
has a collet engagement orifice
48
that slidably engages the head portion
46
of the collet
52
at the gapped end. Because the head portion
46
is conically tapered, urging the collet engagement orifice
48
axial against the head portion
46
will deflect the upper and lower portions
41
,
42
of the collet
52
toward each other, into a closed or clamped position. A spring
53
fits over the brake collet
52
and biases the piston
54
away from the collet
52
. During ablation, the compressed air that powers the drive assembly
16
enters the Rotablator®
10
via a manifold
59
having a first outlet port
61
fluidly connected to the brake cylinder
56
, and a second outlet port
62
leading to the drive assembly
16
through tube
30
. When compressed air is provided to the drive assembly
16
it is supplied in parallel to the brake cylinder
56
. The piston
54
is thereby urged distally toward the brake collet
52
, causing the collet engagement orifice
48
to elastically compress the head portion
46
around the guide wire
26
when the turbine is engaged.
Under certain circumstances, it is desirable to override the guide wire brake
50
and release the guide wire
26
even when the turbine and the drive shaft
22
are rotating. For example, it is sometimes desirable to engage the turbine when the drive shaft
22
is advanced over the guide wire
26
to the target position within an artery, or when the drive shaft
22
is being removed from the artery. Sometimes it is also useful to override the guide wire brake to permit advancement or retraction of the guide wire
26
within the rotating drive shaft
22
. The Rotablator® provides a “dynaglide” mode wherein the guide wire
26
is enclamped when turbine is operated at a lower velocity in order to facilitate such drive shaft insertion and removal. For these and other situations, a bypass valve
57
is provided between the manifold
59
and the brake cylinder
56
, whereby the first manifold outlet
61
to the brake cylinder
56
may be closed. This allows the pressurized gas to drive the turbine without engaging the guide wire brake
50
.
An alternative guide wire brake for an atherectomy device is disclosed in U.S. Pat. No. 5,779,722 to Shturman et al., wherein a mechanical guide wire brake is coupled to a mechanical turbine brake. Shturman et al. teaches a mechanical system wherein translation of the turbine along its track, (which is generally performed to move the burr back and forth over the atheroma), has a range of positions that will engage a turbine brake, and a further range that will then release the guide wire brake. A separate override clamp may be secured to the device to release the guide wire brake without engaging the turbine brake. While the device disclosed by Shturman et al. provides an alternate method of ensuring the guide wire brake is engaged when the turbine is operated, the device has the disadvantages of being relatively complicated to build and to operate. In addition, it is possible that the override clamp could be inadvertently left in place, whereby the guide wire could undesirably be free to move.
It is desirable to provide a guide wire brake assembly that ensures that automatically resets any brake override or bypass mechanisms when the drive assembly is engaged. It is further desirable to have a guide wire brake that engages more quickly or earlier than the turbine when the compressed air supply is switched on, and disengages more slowly or later than the turbine, when the compressed air supply is switched off. It is further desirable to provide a guide wire brake that is mechanically simple and easy to operate.
SUMMARY OF THE INVENTION
A novel guide wir

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