Steerable guide wire for balloon dilatation procedure

A guide wire is provided to guide a very small diameter catheter, such as a coronary dilatation catheter used in coronary angioplasty techniques. The guide wire itself is of very small diameter, (under 0.020") yet is steerable and may be visualized fluoroscopically. The major portion of the guide wire is a small diameter flexible rod. The distal region of the rod is tapered. The tapered portion is surrounded by a helically wound spring which is brazed at its proximal and distal ends, to the base and tip, respectively, of the tapered region of the rod. A shorter segment of the spring extends beyond the distal end of the rod and serves as a highly flexible bumper to assure that the distal tip of the guide wire will not cause traumatic injury to the blood vessel. The distal region of the guide can be bent manually by the surgeon to a curved shape which it will tend to assume when relaxed. The distal region is flexible and can bend from the set curve to follow the contour of the blood vessel. The distal end of the wire can be steered by manipulation and rotation of the proximal end of the guide. At least the spring portion of the guide wire is formed from a material having a high degree of radiopacity to facilitate its fluoroscopic observation. Also disclosed is a combination of such a spring guide with a coronary dilatation catheter.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to guide wires for use in small bore blood vessels 
such as those involved in cardiovascular surgical procedures. More 
particularly, the invention concerns a guide which can be steered into and 
along very narrow blood vessels (including naturally narrow vessels as 
well as stenosed vessels) to locate its distal end in a precise position. 
Once so placed, a catheter can be advanced over the guide wire directly to 
the particular site in the patient's cardiovascular system. The invention 
is of particular importance in coronary dilatation techniques where the 
catheter is itself very small in diameter and is difficult to advance and 
place deeply in the patient's cardiovascular system, as is the case when 
trying to reach a coronary artery. 
Before the present invention there was no satisfactory guide wire for use 
with such small diameter catheters. Typically the procedure for advancing 
a dilatation catheter into the coronary artery has been to use a 
relatively stiff, large diameter, conventional coronary angiographic 
catheter as a guide through which the smaller diameter dilatation catheter 
is advanced. In that technique the relatively large diameter guide 
catheter is advanced and manipulated to locate its distal end at the entry 
to the coronary artery. The more slender, flexible dilatation catheter 
then is passed through the guide catheter so that the distal end of the 
dilatation catheter will exit from the guide catheter and, hopefully, will 
enter the entrance to the coronary artery. The technique, which is 
disclosed in U.S. Pat. No. 4,195,637 to Gruntzig, requires that the 
dilatation catheter be pushed through the guide catheter and then into and 
through the coronary artery. Typically it is required to push the 
dilatation catheter so that its balloon passes through or into the mass of 
stenotic material which obstructs the coronary artery. Because of the 
slender, flexible and delicate nature of the coronary dilatation catheter 
such advancement and placement of the dilatation catheter is a delicate, 
difficult procedure calling for a great deal of skill, care and patience. 
While suggestions have been made to use a guide wire to advance such a 
slender catheter as a coronary dilatation catheter, no suitable device was 
known which could serve properly as a guide wire while being small enough 
to permit the relatively small diameter dilatation catheter to be slipped 
over and advanced along the guide wire. Because the guide wire of the type 
of which the present invention is concerned is much smaller than a 
conventional guide wire (of the order of 0.018" diameter as compared to a 
conventional guide wire approximately 0.038" diameter), numerous 
additional difficulties in the construction and use of such a guide wire 
are presented. For example, using a smaller guide wire typically tends to 
result in reduced stiffness and, therefore, is more difficult to control 
and manipulate. A smaller diameter guide wire typically may be expected to 
be more fragile and more susceptible to breakage. Less torque can be 
transmitted along a smaller diameter, more delicate guide wire, 
particularly a guide wire which utilizes conventional construction in 
which substantially the full length of the guide wire is in the form of a 
helically wound spring wire. Additionally, a smaller guide wire is more 
difficult to observe fluoroscopically. That problem is pronounced 
particularly with heavier patients whose additional tissue makes it more 
difficult to observe fluoroscopically the position of the guide wire. It 
may be possible to observe fluoroscopically the position of a smaller 
guide wire in such a patient. 
It is among the general objects of the invention to provide a guide wire 
construction which is of very small diameter, suitable for use with 
catheters intended to be advanced into small bore arteries such as, for 
example, a coronary dilatation balloon catheter, which avoids the 
foregoing, and other difficulties. 
In accordance with the present invention the guide wire includes a main rod 
or wire of a small diameter which extends substantially the full length of 
the guide wire. The main wire is of uniform diameter except for the distal 
portion which is provided with a progressively narrowing taper. The 
tapered distal portion of the main wire is surrounded by a helically 
coiled spring. In the preferred embodiment the proximal end of the spring 
is secured to the main wire where the wire begins to taper and the distal 
end of the spring is secured to the distal end of the main wire, where the 
taper is most narrow. The distal end of the helical spring extends 
slightly beyond the distal tip of the main wire, for approximately one 
centimeter to define a spring extension. The spring extension tip is 
highly flexible and delicate and may bend and flex easily. It serves as a 
soft, flexible, resilient bumper for the distal tip of the guide wire, 
thereby minimizing the chance of trauma or injury to the blood vessel. The 
main spring and the distal bumper spring are formed from a material having 
a high radiopacity. Although not essential, the main wire also may be 
formed from a material having a high degree of radiopacity. 
A high degree of torque control is provided by the rotationally rigid wire 
which makes up the major portion of the length of the guide wire. The use 
of a rotationally rigid wire over the major length of the guide wire 
assures that most of the torque applied at the proximal end will be 
transmitted fully to the distal region, unlike more conventional guide 
wires in which the torque tends to twist and distort the guide wire. 
The distal region of the guide wire which includes the tapered safety wire 
and surrounding spring may be bent manually by the surgeon to a 
predetermined curve so that the distal portion of the guide will be biased 
toward that curved shape. The curve enables the guide to be advanced 
selectively into various branches at blood vessel bifurcates by 
controlling the rotation of the wire from its proximal end. The 
progressive taper at the distal region of the wire provides for a distal 
region with a main spring which increases in flexibility as it approaches 
the distal tip. Risk of trauma to the blood vessel is minimized by the 
highly flexible short bumper spring extension at the distal tip of the 
device. 
Another aspect of the invention relates to the configuration of the 
dilatation catheter in combination with the small diameter guide wire. The 
catheter is constructed so as to have a main lumen which is dimensioned 
and shaped with respect to the guide wire so that even when the guide wire 
is in place within the main lumen there still is adequate cross-sectional 
flow area in the lumen. Thus the guide wire need not be removed in order 
to administer fluids to the patient or to take pressure measurements or 
the like. 
It is among the objects of the invention to provide a small diameter guide 
wire which provides a high degree of steerable control and which may be 
placed with precision so as to serve as a guide for a catheter. 
Another object of the invention is to provide a small diameter guide wire 
of the type described in which the distal portion may be pre-bent into a 
predetermined curve to facilitate steering of the wire by rotational 
control from the proximal end of the guide wire. 
A further object of the invention is to provide a small diameter guide wire 
in which the distal portion is of increasing flexibility. 
Another object of the invention is to provide a small diameter guide wire 
which has reduced risk of trauma to the inner surface of small bore blood 
vessels. 
A further object of the invention is to provide small diameter guide wire 
having increased fluoroscopic visibility. 
Another object of the invention is to provide a small diameter guide wire 
suitable particularly for use with balloon dilatation coronary catheters. 
Still another object of the invention is to provide an improved combination 
of balloon dilatation catheter and guiding means therefor to advance the 
balloon dilatation catheter. 
A further object of the invention is to provide a guide wire for use with a 
balloon dilatation catheter which facilitates the speed with which a 
vascular or coronary dilatation procedure can be performed. 
Still another object of the invention is to provide a combination 
dilatation catheter and guide wire therefor in which the guide wire need 
not be removed in order to deliver fluids through the catheter or to make 
pressure measurements.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows the guide wire 10 of the present invention in combination with 
a balloon dilatation catheter 12 of the general type described in the 
aforementioned Gruntzig patent. The dilatation catheter 12, particularly 
when it is intended for use in a coronary artery, is relatively slender 
and, for example, may have an outer diameter of the order of 0.050". The 
inner diameters of its lumens, of course, are even smaller and its main 
lumen may be the order of 0.022" diameter at its smallest cross-sectional 
dimension. The dilatation catheter has a dilatation balloon 14 at its 
distal end and a central lumen 16 (See FIG. 3) which is used typically to 
deliver liquids such as radiopaque dyes or anticoagulants and also may be 
used to make pressure measurements. The central lumen 16 opens at an 
outlet 13 at the distal tip. As shown in further detail in FIG. 3 the 
dilatation catheter also is provided with an inflation lumen 17 which is 
smaller and communicates with the interior of the balloon 14 to inflate 
and deflate the balloon. The proximal end of the catheter may be provided 
with a Y-fitting 19 to provide communication at the proximal end of the 
catheter to each of the central lumen 16 and inflation lumen 17. 
As described in the aforementioned Gruntzig patent, such a catheter 
typically has been guided to the entrance of the coronary artery by a 
relatively large diameter guide catheter having an internal lumen large 
enough to accommodate the outer diameter of the dilatation catheter. Such 
a guide catheter can, at best, only lead the dilatation catheter to the 
entry to a coronary artery because the guide catheter typically is too 
large to make any significant entry into the coronary artery. Because the 
relatively large guide catheter cannot be advanced into and controllably 
manipulated through the coronary arteries, the prior practice has required 
that the dilatation catheter be pushed into and through the coronary 
artery to reach the area to be treated. Because of the relatively small 
diameter and delicate, flexible construction of the dilatation catheter, 
advancement of the catheter into a narrow coronary artery, and 
particularly one which is obstructed, often is quite difficult and takes a 
considerable amount of skill. Sometimes it simply is not possible to reach 
as deeply into the coronary artery as might be desired. 
Also among the difficulties which may be presented with the prior technique 
of using a guide catheter is that because of the difficulty which may be 
encountered by trying to push and advance the balloon dilatation catheter 
through the coronary artery, more surgical time may be used than would be 
desirable. In this regard it is desirable that such dilatation procedures 
be performed as quickly as possible so that the artery is obstructed as 
briefly as possible. 
In accordance with the present invention, a guide wire 10 is advanced 
through the patient's vascular system, its direction being controlled and 
fluoroscopically monitored by the surgeon, until its distal end is at the 
desired location. Because the wire is very small in diameter it does not 
present any substantial obstruction to blood flow in the blood vessel. 
Then, the dilatation catheter 12 is advanced over the guide wire with the 
wire being received in the main lumen 16 of the catheter 12. The guide 
wire thus simply and automatically guides the catheter directly to the 
intended region, without requiring difficult, time consuming 
manipulations. 
As shown in further detail in FIG. 3 the dilatation catheter is formed from 
extruded plastic and has an internal web 15 which separates and defines 
the main and inflation lumens 16, 17. As shown, the inflation lumen 17 is 
smaller than the main lumen 16. Both of the lumens 16, 17 are generally 
D-shaped cross-section. The main lumen 16 extends to the distal tip and 
terminates in opening 13. The inflation lumen 17 leads to the balloon. In 
the illustrative embodiment of the invention, the main lumen has a minimum 
dimension which is just slightly greater than the diameter of the guide 
wire 10. The maximum cross-sectional dimension which, in the illustrative 
embodiment consists of the straight wall portion of the D-shaped lumen 16 
is substantially larger than the cross-section of the guide wire 10. Thus, 
when the guide wire 10 is disposed within the main lumen 16 there will be 
substantial voids through the central lumen 16, on opposite sides of the 
guide wire 10 through which fluids may be administered to the patient and 
through which blood pressure measurements may be taken. Such fluids may be 
administered and pressure measurements may be taken without removing the 
guide wire at all thereby contributing to the reduced time required for 
for procedures in accordance with the invention. By way of example, the 
cross-section of the guide wire 10 preferably is of the order of no more 
than about fifty percent of the cross-sectional area of the main lumen 16. 
FIG. 2 shows the construction of the guide wire in further detail although 
portions are not to scale for ease of explanation and illustration. FIG. 
2A illustrates portions of the guide wire in enlarged, more scaled detail. 
The guide wire 10 typically will be approximately 175 centimeters long so 
that it may be introduced either through the femoral or brachial arteries 
and have ample length to reach the patient's coronary region. The guide 
wire 10 includes a small diameter main wire 18. Main wire 18 can be solid 
or tubular, as long as it is rigid torsionally so that it may transmit 
fully to the distal end a rotational motion imparted to the proximal end. 
Unlike conventional guide wires which are formed substantially from 
elongate helical springs and which do not provide good torque transmission 
from the proximal to distal end, the present invention provides a very 
high degree of torque transmission from the proximal to its distal end 
because the rotationally rigid main wire 18 will have relatively little 
twist as its proximal end is rotated. Practically all rotation applied to 
the proximal end will be transmitted quickly to the very distal tip of the 
guide wire. The main wire 18 may be solid, as shown in the drawings, or 
may be in the form of a hollow tube. In either case it is rotationally 
rigid so that the maximum amount of torque applied at the proximal end can 
be transmitted to the distal end. 
The main wire 18 is of uniform diameter except the distal region 20 of the 
main wire is provided with a taper. The distal tapered portion 21 may be 
approximately twenty centimeters long and may be formed by grinding. It is 
important that the taper be regular and uniform without any sharp 
transitions which might form stress concentrations or tendencies to kink 
when the wire is bent in use, as will be described. 
The distal tapered portion 20 of the main wire 18 is surrounded by a 
helically wound spring 22 which is slightly more than twenty centimeters 
long. The proximal end of the spring 22 is secured to the main wire, as by 
brazing at a proximal connection (indicated at 23). The distal end of the 
main spring 22 is secured to the distal end of the tapered portion 20, 
also by a brazed distal connection connection such as suggested at 26. The 
distal tapered portion 21 thus acts as a safety wire for the spring 22. 
Additionally, the uniform tapering configuration of the distal tapered 
portion 20 results in an arrangement by which the distal region has an 
increasing uniform flexibility along the length of the spring. 
The distal tip of the guide wire 10 is formed by an extension 28 of the 
spring 22 which is relatively short and extends approximately one 
centimeter beyond the distal end of the wire 18. The spring extension 28 
is very flexible and has, at its most distal tip, a weld 30 which is 
smoothly rounded off. The spring extension 28 serves as a flexible bumper 
at the leading end of the advancing guide wire, and minimizes the risk of 
trauma or injury to the delicate internal surfaces of the artery. Should 
the distal end of the guide wire 10 be advanced toward a blood vessel 
surface at too sharp an angle or otherwise in a manner which otherwise 
might present some risk of trauma, the bumper spring 28, being highly 
flexible and with a very smooth leading end, tends to soften the contact 
and also tends to guide the spring 22 in a direction which will avoid 
trauma to the blood vessel. 
At least the main spring 22 and bumper spring 28 are formed from a material 
having a high degree of radiopacity. For example, spring material of an 
alloy consisting of approximately 92 percent platinum and 8 percent 
tungsten has been found to provide satisfactory radiopacity while 
providing ductility and good spring flexibility. The spring wire may be 
wound from wire 0.004" diameter. The outer diameter of the main spring 
portion 22 may be of the order of 0.018" diameter. The main wire 18 may be 
of the order of 0.016" diameter. It is desirable to maintain the outer 
diameter of the spring 22 as close to the outer diameter of main wire 18 
as is practically possible and to provide as smooth a transition as is 
practical. Thus, the outer diameter of the spring should not be 
substantially greater, if at all, than the outer diameter of the main wire 
18. Additionally, having the main wire 18 with an outer diameter as close 
to the outer diameter of the main spring is desirable so that the main 
wire 18 may have the maximum torsional rigidity. 
The platinum-tungsten alloy also is quite satisfactory in that the tapered 
distal region can be bent manually by the surgeon and will retain its bent 
configuration when relaxed. This enables the guide wire to be controllably 
steered by rotation of the guide wire to direct the curved distal end 
selectively into various arterial branches. Rotational control of the 
guide wire may be enhanced by bending the proximal end of the wire 18 to 
form somewhat of a handle, as suggested at 25 in FIG. 1. 
FIG. 4 is an illustration of a modified embodiment of the guide wire. In 
this embodiment the proximal portion of the wire is formed from a 
composite including a length of hollow outer hypodermic tubing 40 to which 
the proximal end of the spring 22 is brazed, as at 42. A safety wire 44 
extends through both the hypodermic tubing 40 and into the interior of the 
spring 22 where it is attached to a more distal region of the spring 22, 
at 45. Safety wire 44 is secured at its proximal end by a weld 46 to the 
hypodermic tube. 
In this embodiment the taper of the wire 44 within the spring 22 begins at 
a location, indicated at 48, between the ends of the spring 22. Thus, in 
contrast with the previously described embodiment, this embodiment 
utilizes an arrangement in which that portion of the wire 44 which extends 
from the junction 42 to the region 48 will display a substantially uniform 
degree of flexibility whereas the remaining more distal portion of the 
wire 44, extending from region 48 to connection 45 will display 
progressively increasing flexibility. This alternate configuration is in 
all other respects the same as the previously described embodiment. 
In use, the surgeon may bend the distal region of the guide wire so that it 
will be biased toward and will assume somewhat of a curve when relaxed. 
When advanced through the patient's artery the degree of resilience at the 
distal region of the wire is such that the wire will straighten and follow 
the path of the artery quite easily. The progressively increased 
flexibility resulting from the continuous taper at the distal region of 
the device enhances the ability of the guide wire to flex from the 
pre-bent biased curve and follow the path of the blood vessel. 
The relatively high degree of radiopacity of the distal region of the wire 
enhances the fluoroscopic imaging of the wire as it is advanced through 
the patient's artery. As indicated above, this is particularly important 
when the patient is somewhat obese which tends to make fluoroscopic 
observation of a slender guide wire quite difficult, and sometimes 
impossible with conventional guide wires. 
When the distal end of the pre-bent, biased guide is at an arterial fork, 
the surgeon can steer it into one branch or the other selectively by 
rotation of the guide wire by manipulating it from the proximal end. As 
described, the solid wire configuration which extends over the major 
proportion of the guide provides for a high degree of torque transmission 
and rapid response at the distal end. As a result, the advancement of the 
guide wire can be observed with clarity and its direction steered quickly 
and responsively, all of which tends to reduce the amount of time that the 
operation takes. 
The procedure for using the guide wire and dilatation catheter in 
accordance with the present invention involves initial placement and 
location of a conventional guide catheter so that its distal end is 
adjacent to the coronary ostium, the entry to the coronary artery. The 
dilatation catheter is prepared with the guide wire in place, extending 
through the main lumen 16 so that about two centimeters of the distal tip 
of the guide wire project distally beyond the outlet 13 of the dilatation 
catheter. This assembly of dilatation catheter and guide wire then is 
pushed through the guide catheter into the coronary artery, with the guide 
wire being used to manipulate the dilatation catheter selectively into 
deeper and smaller coronary arteries. In this regard it should be noted 
that the simultaneous advancement of the dilatation catheter and guide 
wire is performed with the distal portion of the guide wire projecting 
distally beyond the outlet 13 of the dilatation catheter. The projecting 
end of the guide wire tends to bias toward the curved configuration which 
the surgeon will have preset as he desires. As the stenosis is approached 
it may be desirable to advance the guide wire independently of the 
dilatation catheter to locate the guide wire with a high degree of 
precision with respect to the stenosis. The guide wire is advanced to that 
site by a combination of pushing and rotation or steering of its proximal 
end. Once the guide wire is in place across the stenosis the dilatation 
catheter then may be advanced over the guide wire to a point where the 
balloon is positioned within the obstruction. This can be verified 
fluoroscopically because of the highly radiopaque characteristic of the 
spring and also by injecting radiopaque dye through the main lumen 16. 
Additionally, verification may be determined by monitoring the drop in 
arterial pressure through the lumen 16 as the balloon is advanced across 
the stenosis. 
The dilatation catheter typically is provided with radiopaque rings 32 
which also facilitate fluoroscopic monitoring of its progress and 
position. When the balloon dilatation catheter has been advanced so that 
the balloon is located as desired, the balloon then may be inflated as 
described in the Gruntzig patent to dilate the stenosis and expand the 
vascular lumen. During the procedure liquids such as radiopaque dyes, 
heparin may be administered to the patient or pressure monitoring readings 
can be taken without removing the guide wire. 
Thus, I have described an improved system for guiding vascular catheters 
(and particularly dilatation catheters) to a predetermined site in the 
patient's vascular system. The invention results in a highly controllable 
and steerable guide having a high degree of radiopacity to facilitate 
fluoroscopic observation even with obese patients. Moreover, these 
advantages have been achieved in a guide wire which reduces the chance of 
traumatic injury to the delicate interior of the arteries. Notwithstanding 
its small diameter and delicate nature the distal end can be pre-formed to 
a predetermined biased curve yet it will not develope stress points or 
tend to kink. The invention enables dilatation procedures to be performed 
more radidly with reduced time during which the dilatation catheter 
resides in the blood vessel. 
It should be understood, however, that the foregoing description of the 
invention is intended merely to be illustrative thereof and that other 
embodiments and modifications of the invention may be apparent to those 
skilled in the art without departing from its spirit.