Surgery – Instruments – Blood vessel – duct or teat cutter – scrapper or abrader
Reexamination Certificate
2000-11-22
2003-09-30
Hale, Gloria M. (Department: 3765)
Surgery
Instruments
Blood vessel, duct or teat cutter, scrapper or abrader
C606S180000, C606S170000
Reexamination Certificate
active
06626923
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to atherectomy devices, in general and in particular to brake systems for use in atherectomy devices.
BACKGROUND OF THE INVENTION
Arteriosclerosis is a common vascular disease in which a patient's blood vessels become hardened and blocked by plaque or clots that impede blood flow. Left untreated, this condition is a major contributing factor to the occurrence of high blood pressure, strokes and cardiac arrest.
To treat arteriosclerosis, many invasive and non-invasive techniques have been developed. For example, cardiac bypass surgery is now a commonly performed procedure whereby an occluded cardiac artery is bypassed with a segment of a healthy blood vessel that is obtained from elsewhere in the body. While this procedure is generally successful, it is fairly traumatic because the entire chest cavity must be opened to access the occluded vessel. Therefore, the procedure is not generally performed on elderly or relatively frail patients.
One example of a minimally invasive technique that is being performed on a greater number of patients is to remove the occluding material from a patient's vessel with an atherectomy device. To perform this procedure, a guide catheter is typically inserted into the patient's femoral artery and advanced until the distal end of the guide catheter is located in the patient's ostium. A guide wire is then inserted through the guide catheter and traversed into the coronary arteries and past the occluded material to be treated. Then, as described in U.S. Pat. No. 4,990,134, issued to Auth, an atherectomy catheter having a small abrasive burr is advanced through the guide catheter and over the guide wire to the point of the occlusion. The burr is then rotated at high speed and passed through the occlusion during an ablation phase in order to remove particles that are sufficiently small such that they will not reembolize in the distal vasculature. As the burr removes the occlusion, a larger lumen is created in the vessel and blood flow is restored.
During the atherectomy procedure, after the burr has been routed over the guide wire to the location of the occlusion, the physician activates a rotational source (i.e. gas turbine) coupled to the burr by depressing a foot pedal so that the rotational source spins the ablation burr up to operational speed. In a conventional atherectomy device, a brake system is activated in unison with the rotational source to prevent rotation of the guide wire during the ablation phase of the atherectomy procedure. If the guide wire is not secured, the rotational inertia of the burr may begin to spin the guide wire and advance it downstream of the occlusion.
As shown in
FIGS. 1 and 2A
, a conventional brake system
20
consists of a brake cylinder
22
, having a bore
24
extending therethrough. The cylinder
22
is mounted to a brake assembly bracket
26
. A cylindrical piston
28
having an inner tapering or partially conical bore
30
linearly reciprocates within the bore
24
of the brake cylinder
22
. A wiper ring seal
32
is seated on a front surface
34
of the piston
28
to create a chamber
38
within the bore
24
. A cylindrically shaped brake collet
40
is disposed adjacent to the rear surface of the piston
28
. The brake collet
40
includes an axial bore
46
for allowing the guide wire
42
to extend therethrough.
Referring to
FIG. 2A-2B
, the distal end of brake collet
40
further includes a pair of tapered jaws
44
that begin at approximately the mid point of the brake collet
40
. The tapered jaws
44
have a conical engagement surface
50
that mates with the tapering bore
30
of the piston
28
. The jaws
44
are separated by a slot
52
that extends from the distal end of the brake collet
40
toward the mid-section such that the jaws are hinged at the proximal end but can bend inward toward the exposed guide wire
42
when the jaws are forced into the tapering bore
30
of the piston
28
.
The brake cylinder
22
has a gas inlet
56
that connects the chamber
38
to a source of gas through a gas conduit
58
. Attached to one end of the brake cylinder
22
is a brake bracket
60
. The brake bracket
60
has a centrally located bore
62
to retain the distal end of the brake collet
40
and to retain the brake collet
40
in proper alignment with the piston
28
. Disposed around the brake collet
40
is a return spring
64
which exerts force on the rear face
66
of the piston
28
in order to return the piston
28
to its original location after the brake system
20
is deactivated.
With reference to
FIGS. 1 and 2A
, during the operation of the atherectomy device, the physician rotates the ablation burr via activation of a foot pedal. Depression of the foot pedal allows gas from a gas line
70
to enter manifold
74
having a gas conduit
58
fluidly connected to brake cylinder
22
, and an outlet port
78
leading to the rotation source through tube
80
. Gas entering chamber
38
through gas inlet
56
exerts pressure on the front piston face
68
thereby causing the piston
28
to linearly translate within the bore
24
of the brake cylinder
22
. As the piston
28
moves linearly toward the brake bracket
60
, the inner tapering bore
30
of the piston
28
engages the correspondingly conical engagement surface
50
of the brake collet
40
to urge the jaws
44
radially inward to engage with the guide wire
42
. The jaws
44
of brake collet
40
clamp down onto the guide wire
42
so that the guide wire
42
is prevented from rotating. After the occlusion has been ablated, the physician releases pressure on the foot pedal to deactivate the ablation burr. When the physician releases the foot pedal, the gas is shut off from the chamber
38
allowing the biasing force of the return spring
64
to move the piston
28
linearly back toward the proximal end of the brake cylinder
22
as the gas escapes back through the gas conduit
58
. This disengages the brake collet
40
from the guide wire
42
. To prevent potential rotation of the guide wire, care must be taken to ensure that the driveshaft has stopped rotating before the spring
64
pushes the piston
28
towards the brake cylinder
22
thereby releasing the guide wire.
While the brake system illustrated in
FIGS. 1 and 2A
works well to prevent rotation of the driveshaft during the ablation procedure, the present invention seeks to improve the performance and to simplify the design by eliminating the wiper ring seal
32
.
SUMMARY OF THE INVENTION
The present invention is a brake activator system comprising several linear actuators using a bellows design to decrease the leakage of gas in the brake cylinder and ensure that the guide wire is prevented from rotating during the activation and deactivation of the atherectomy device.
In one embodiment, the brake activator system comprises a housing which includes two coaxially disposed apertures for receiving a guide wire therethrough. At least one bellows is coupled to the linear actuator. A brake collet having a camming surface and a braking surface is engageable with the guide wire. Expansion of the bellows urges the braking surface of the brake collet toward the guide wire to prevent the rotation thereof.
In another embodiment, the linear actuator uses two concentrically arranged bellows to form an annular chamber. Expansion of the chamber linearly translates the rear plate of the linear actuator into engagement with a brake collet. The conical shape of each engagement surface results in the brake collet clamping down on the guide wire and thus preventing its rotation.
In yet another embodiment, the brake activator comprises a housing, a pair of bellows and a pair of brake shoes. One end of each bellows is secured to opposing interior walls of the housing. Brake shoes are attached to the other end of each bellows to form two chambers. Expansion of the chambers linearly translates the brake shoes radially inward into engagement with the guide wire to prevent its rotation.
As will be readily appreciated from the forego
Christensen O'Connor Johnson & Kindness PLLC
Hale Gloria M.
Sci-Med Life Systems, Inc.
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