U.S. patent number 3,557,794 [Application Number 04/748,737] was granted by the patent office on 1971-01-26 for arterial dilation device.
Invention is credited to Robert E. Van Patten.
United States Patent |
3,557,794 |
Van Patten |
January 26, 1971 |
ARTERIAL DILATION DEVICE
Abstract
An improved catheter is disclosed in which the length of the
active portion of the instrument is divided longitudinally into
four or more beams, preferably of rectangular cross section. The
beams are constituted of spring steel and are held between two
abutments on the catheter, one of which is adapted to be retracted
toward the other by an actuator wire controlled by a micrometer
screw. The beams are positioned independently of one another and
normally rest snugly about a metal tubing so that when the abutment
is caused to move the compressive force causes the beams to flex
outwardly except at their ends since the tubing prevents any
movement inwardly. The beams therefore execute a smooth flexing
effect and define an enlarged outline which, when contained in a
blood vessel, artery, etc., causes a dilation of that member. When
the pull in the actuator wire is released at the micrometer screw,
the beams spring back into their normal rest position to allow
ready retraction of the catheter. A standard form of strain gage
using the Wheatstone Bridge principle may be applied to the
actuator wire to determine the counterforce exerted by the blood
vessel against the deployment of the dilator.
Inventors: |
Van Patten; Robert E. (Dayton,
OH) |
Assignee: |
|
Family
ID: |
25010705 |
Appl.
No.: |
04/748,737 |
Filed: |
July 30, 1968 |
Current U.S.
Class: |
606/198 |
Current CPC
Class: |
A61M
29/02 (20130101); A61B 2017/22001 (20130101) |
Current International
Class: |
A61M
29/00 (20060101); A61B 17/22 (20060101); A61m
029/00 () |
Field of
Search: |
;128/341,345,348--350,305,304,242--244 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Truluck; Dalton L.
Claims
I claim:
1. A catheter comprising an elongated tubular device having an end
portion adapted to be inserted into a vessel of the body and a base
portion adapted to be grasped by the hand, an actuating wire
extending along the axis of said tubular device from said end to
the base portion and having a rounded terminal member tightly
fitted thereto at the insertable end, a tubing loosely surrounding
said wire and extending between the rounded member and the base
portion of the device, cylindrical ferrules spaced from and
surrounding said actuating wire and tubing at the insertable end of
the device and at the base portion, leaving annular spaces
therebetween, the ferrule at the insertable end being affixed to
said rounded member and movable lengthwise of the tubular device
when a pull is exerted on the actuating wire, the ferrule at the
base portion of the device being stationary with respect to said
portion, and a plurality of flexure beams having their ends
detachably and slidably positioned respectively within the spaces
between the ferrules and the actuating wire, the intermediate
portions of said beams normally resting on said tubing, whereby
when a pull is exerted on said wire, the movable ferrule moves
toward the stationary ferrule and the flexure beams are caused to
bow outwardly from said tubing so as to expand the blood vessel in
which the catheter is inserted.
2. A catheter according to claim 1 and in which said beams are
constituted of rectangularly shaped beams arranged in a circular
outline, said ferrules having slots at their inside surfaces
extending radially outward for slidable receiving the ends of the
beams, said slots being of a shape and size as snugly but
detachably to hold the beams in position.
3. A catheter according to claim 1 and means for measuring the
strain in the actuator wire to determine the counter-force that the
vessel exerts against the deployment of the dilating device.
4. A catheter according to claim 3, said means comprising a
normally balanced Wheatstone Bridge device in which one of the
resistance arms is secured to the actuator wire to partake of the
strain imparted to the wire for measurement by said device.
Description
BACKGROUND OF THE INVENTION
In medical research relating to cardiovascular physiology, it is
occasionally desirable to positively position or stabilize some
device within the lumen of a blood vessel or to dilate the vessel
by mechanical means. Catheters of various sizes are generally
employed for this purpose. For dilating the blood vessels it has
been customary to attach to the catheter, and operated from an
exterior position, an "umbrella" type of mechanism or to employ the
spring force stored in compressed wire fingers. However, several
problems arise in connection with the construction of extremely
small linkage mechanisms when it is considered that catheters of
this type are hardly ever greater than one-eighth of an inch in
diameter and the linkage would necessarily have to fit within the
confines of this diminutive member. In those cases where the
compressive forces are used for causing a dilation effect in the
arterial system, high bending stresses are encountered which demand
close control of the temper in the spring materials. Furthermore,
the retraction of an expanded unit of the finger spring type, once
it had been deployed in a vessel, it was often difficult to
compress it to its normal size from the enlarged condition
preparatory to being withdrawn from the body. Moreover, catheters
of the type mentioned, when in a dilated form, may not always
define a symmetrical body, and therefore it becomes difficult to
center themselves within the artery being dilated. The lop-sided
position of the forward end of the catheter may actually cause
damage to the tissue and, in aggravated cases, sever pain to the
patient.
SUMMARY OF THE INVENTION
One object of the invention is to provide an improved form of
catheter of such diameter as to be useful in human as well as
animal work and will align itself with the axis of the vessel to
ensure positive position.
Another object is to provide a catheter of the type mentioned and
in which the member can be mechanically dilated up to at least 2
centimeters without the use of linkage or spring force stored in
compressed wire fingers.
Still another object is to provide an improved catheter in which,
having been dilated, the member can be easily compressed and
withdrawn from the body without the slightest complication.
The final object is to provide a catheter structure which lends
itself to the use of ancillary apparatus which would enable the
doctor to measure the amount of dilation remotely or to measure the
forces related to the dilation.
Other objects and features will be apparent as the following
description and the accompanying drawing are perused in connection
with the improved invention.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 represents a longitudinal section, greatly enlarged of the
improved catheter, portions of which are shown in elevation for
clearness and together with certain ancillary apparatus shown
partly by diagram and partly in elevation;
FIG. 2 is a view similar to FIG. 1 but showing the improved
catheter in expanded form for dilating a blood vessel. All of the
ancillary apparatus are shown in elevation; and
FIG. 3 represents a view taken at about the two lines 3-3 in FIG. 1
and looking in the direction of the arrows.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1 and 2, reference character 1 designates a
length of standard No. 8 X-ray catheter material of about
one-eighth of an inch diameter and constructed usually of surgical
stainless steel. There is a proximal fitting 2 of similar material
at the base portion of the catheter and secured thereto in any
suitable and well known manner, for example, by a proper
metal-to-metal cement. This fitting comprises a collar portion
having a stem 3 which fits snugly within the interior of the
catheter piece 1. The fitting has a central opening 4 for slidably
receiving an actuator wire 5. The latter preferably is constituted
of music wire of special steel, approximately .013 inch diameter
and the purpose of which will be explained hereinafter.
Next to the fitting 2 there is a metal ferrule 6 of about the same
size as the fitting and it is secured to the latter in any suitable
and well known manner. The ferrule is relatively thick and has an
opening 7 (FIG. 3) larger than that of the fitting 2 and this
opening is provided with a plurality of square shaped milled out
slots 8 spaced equidistantly apart. The slots have a bottom surface
which is curved outwardly as indicated at 9 (FIG. 1) for reasons
which will be apparent hereinafter. These slots have a width and
depth of such dimensions as to provide a close slip fit with the
left-hand end of the flexure beams 10. The latter are of
rectangular shape, preferably greater in width than in thickness,
as seen in FIG. 3, and are constituted of stainless spring steel of
highest surgical quality.
At the other or distal end of the catheter, there is a ferrule 11
similar to the member 6 and having an opening 7 (FIG. 3) through
which the right-hand end of the actuator wire 5 passes. This
ferrule, like its left-hand counterpart, is provided with four
slots 8, having bases which are rounded upwardly and outwardly as
indicated at 9; quite similar to those shown and described
hereinbefore. These slots are of such size as to provide a close
slip fit with the right-hand tips of the flexure beams 10. The end
of the catheter which is inserted into the body, blood vessel, or
other body cavity, terminates in a cylindrical member 12 of the
same diametral size as the ferrule 11 but of greater length. This
distal fitting has a hemispherical end 13 and is provided with a
central opening which tightly receives the right-hand end of the
actuator wire 5. The latter is rigidly secured in any suitable
manner to the member so that there is not the slightest movement
therebetween, regardless of the stresses or stains imposed upon the
actuator wire. The member 12 can be made of surgical stainless
steel or of a plastic material such as that sold under the names
"Teflon" or "Nylon." The ferrule 11 is cemented or otherwise
secured to the member 12. A tube composed of a length of hypodermic
needle tubing of surgical stainless steel is employed within the
body of the catheter; this tubing being cut to a length of
approximately 5 mm less than the distance between the inside
surface of the fitting 2 and the cylindrical member 12. The opening
is the tubing is slightly larger than the diameter of the actuator
wire 5 so as to permit a sliding fit. The outside diameter of the
tubing is somewhat less than the distance between the inside
surfaces of the opposite pairs of the beams 10. The purpose of the
tubing will be explained hereinafter.
The dilator assembly is built up as follows: first, the proximal
fitting 1 is installed in the distal end of the standard X-ray
catheter. Next, the actuator wire (.013 diameter) is fed through
the lumen of the catheter. The limiting tube 14 is next slipped
over the actuator wire and the beam ferrules 6, 11 are placed in
position with their curved inside edges 9 facing one another. Next,
the distal fitting 12 is secured to the end of the actuator wire
and held in this position in any suitable and well known manner. It
will be noted that the end view of the distal fitting 12 and the
ferrule 11 is approximately the same as the view of the proximal
fitting 2 and the ferrule 6 as shown by the fact that the viewing
line 3-3 may be applied to both portions.
When the ferrules are pressed in place or otherwise secured to the
proximal and distal fittings, the flexure beams 10 are next fitted
into the beam pockets in each fitting formed by the milled out
slots referred to hereinbefore. These beams are held within the
slots solely by friction since the slots have been cut snugly to
receive the ends of the beams, Suitable dimensions for the beams,
of which there are four, and made of spring steel, are .010 inch
(.025 mm.) in thickness and .020 inch to .030 inch (.508 mm. to
.562 mm.) in width. The four beams have a length that they can be
gently flexed and inserted into the beam pocket in each ferrule.
This completes the basic assembly.
At the operator end of the catheter, the amount of deployment of
the beams 10 may be controlled by attaching to the end of the
actuator wire 5 an enlarged member or lug 15 of rectangular cross
section which is attached freely to slide within a rectangular
opening 16. The latter is formed in a circular web element 17,
secured at its periphery to the interior surface of the base
portion of the catheter designated at 1. The purpose of the member
15, slidably contained within the web member 17, is to prevent
rotation of the actuator wire while it is being pulled or released
to dilate or compress the beams 10. In order to apply a pulling or
releasing effort to the wire, and particularly in view of the
diminutiveness of the wire, it may be desirable to attach a second
enlarged member 18 to the wire and of circular configuration. This
member carries fine threads on its periphery. An apertured drum 19,
threaded along its bore and having a micrometer scale 20 engages
the threads of the enlargement 18 and is caused to press lightly
against the square or cut end of the base portion of the catheter
when being operated. By rotating the drum in one direction or the
other, according to the scale on the drum, a pulling or releasing
effect can be applied to the actuator wire for purposes explained
hereinafter. An indexing pointer 21 is secured as by screw 22 to
the catheter in order to show the amount of rotation and,
therefore, the amount of longitudinal movement of the actuator
wire.
To operate the device within a blood vessel, the actuator wire is
pulled by turning the micrometer drum 19 so that the distal fitting
11 approaches the proximal fitting 2, thus decreasing the distance
between the assembly 11, 12 and assembly 2, 6. The pull on the wire
subjects the flexure beams to a coaxial compressive stress. The
limiting tube 14 prevents the beams from flexing inwardly and
limits the amount of shortening possible between the movable
ferrule 11 and the stationary ferrule 6. Since the slender beams
are restrained from flexing inwardly they will, under the axial
compressive stress, bow outwardly, as seen in FIG. 2 to provide a
structure which dilates the vessel to the degree desired. This
bulging effect or dilation is indicated in FIG. 2 and can be as
much as 2 centimeters or more. The deployed diameter may of course
be controlled by varying the dimensions of the assembly. It will be
noted that the lack of a rigid (i.e. soldered) connection at each
beam end and the curved ferrule contour (indicated at 9) and the
close slip fit of the fitting assemblies allow both sliding and
bending to occur at the beam surfaces, thereby relieving the high
bending stresses which could be incurred with a rigid joint. It is
also apparent that the 2:1 or 3:1 width/thickness ratio of the
beams also prevents the torsional bending and lateral displacements
which might be encountered with beams of circular cross section.
The amount of deployment of the beams 10 may be readily determined
by the final micrometer setting at the dial 20 which previously had
been calibrated.
In order to compress the beams 10 to their original position of
resting against the periphery of the tubing 14, it is merely
necessary to turn the micrometer head in the direction opposite
from that when obtaining dilation. The ferrule 11, together with
its terminating head 12, will then move to the right under the urge
of the spring effect left in the beams so that the latter will
again compress to coincide over their entire length with their
original position preparatory to retraction from the vessel.
In applications in which it is desirable to measure the
counter-force exerted by the blood vessel against the deployment of
the dilator, a sensitive strain gage of any suitable and well known
type can be applied to the actuator wire when the beams 10 are
under dilation. A Wheatstone Bridge arrangement indicated generally
at 23 may be used to advantage in which one of the resistance arms
is constituted of a short metal strip indicated broadly at 24,
cemented or otherwise firmly attached to the wire 5 (not shown but
merely indicated), so as to react to the strain in the latter. The
bridge is balanced in the absence of any strain in the resistance
strip so that the galvanometer 25 can be calibrated in terms of
strain units when the micrometer head 19 is turned to cause the
beams to bow outwardly as explained hereinbefore. There is a direct
relationship between the strain at which the wire is subjected and
the counter-force exerted by the vessel and this strain produces a
change in resistance of the arm 24 of the bridge. Consequently the
meter 25 will, assuming that it had been balanced in the absence of
any strain in the wire 5, now provide a visual determination of the
magnitude of the counter-force. This information is also of
invaluable assistance to the operator in determining the tonicity
or elasticity of the arterial walls.
From the foregoing, it is apparent that I have disclosed an
improved catheter which provides a considerable degree of dilation
and uses no linkages of any kind. There are no solid connections at
the point where the flexure beams are held in position within the
slots at the ferrules 6, 11, and there are no high bending stresses
are involved demanding close control or temper in the spring
materials. Finally, the automatic compression of the dilated beams,
when the pulling pressure is relieved at the micrometer head and
provided solely by the spring condition of the beams, is of great
benefit when it is desired to withdraw the catheter from the body,
particularly in the case of arteries and blood vessels of small
size.
* * * * *