Balloon dilation probe

Probe-like catheter has a small diameter and can be steered to and passed through narrow stenoses. The probe has a balloon at its distal end which is collapsible to a low profile to enable it to be passed through the stenosis. The probe may include a distal tip which can hold a preset curve. The probe is sufficiently rigid to enable the transmission of torque to the distal end to permit steering of the probe by controllably rotating the proximal end of the probe. In use, a stenosis which cannot be crossed by a more conventional sized dilatation catheter may permit passage of the dilatation probe.

FIELD OF THE INVENTION 
This invention relates to a new and improved catheter for performing 
balloon angioplasty procedures on stenosed blood vessels. 
BACKGROUND OF THE INVENTION 
Balloon angioplasty procedures have been used in recent years with 
increasing success in the treatment of obstructed arteries, such as the 
coronary arteries. The procedure involves advancing a catheter having a 
special balloon at its distal end to the location of the stenosis. The 
balloon portion of the catheter is placed, in its deflated condition, in 
the stenosis and then is inflated under high pressure to compress radially 
and outwardly the biological material such as plaque which forms the 
stenosis. Balloon dilatation systems of this type are illustrated in U.S. 
Pat. Nos. 4,195,637 and 4,323,071. In those situations in which balloon 
angioplasty can be used, its successful use avoids the greater risk of 
complex and expensive bypass surgery. 
Not all arterial stenoses are treatable by balloon angioplasty. Among the 
types of vascular obstructions which have not been treatable with the 
angioplasty technology are those in which the passage through the stenosis 
is so narrow that the balloon angioplasty catheter cannot be inserted into 
the stenosis, even when the balloon is in its collapsed, deflated 
condition. Thus, where the opening in a stenosis was only enough to permit 
passage of a guide wire, but not enough to permit passage of a deflated 
angioplasty balloon, the procedure could not be performed. Until the 
present invention, such conditions disqualified the patient from receiving 
the potential benefits of the angioplasty technique. Instead, such 
conditions required bypass surgery. 
Also among the difficulties encountered in the angioplasty technique has 
been the advancement and placement of the dilatation balloon catheter in 
the intended branch of the arterial tree so that it can be advanced into 
the stenosis to be treated. Difficulties often are encountered in guiding 
the catheter to the obstructed branch or portion of the arterial tree. 
It is among the primary objects of the invention to provide a catheter 
which enables such very narrow stenoses to be treated with the balloon 
angioplasty technique, and in a manner in which the catheter can be guided 
accurately. 
SUMMARY OF THE INVENTION 
The invention involves use of a novel probe. The probe is very small in 
diameter and has a small diameter, thin-wall balloon at its distal 
portion. The probe is constructed and arranged to be advanceable through 
the patient s vascular system and can be controlled and manipulated from 
its proximal end so that it can be steered selectively at forks in the 
vascular system. 
The main body of the probe has a flexible, elongate, hollow main shaft 
adapted to transmit torque without whipping. A smaller diameter balloon 
support wire is attached to and extends from the distal end of the 
flexible hollow shaft. A helical spring is mounted to the distal portion 
of the support wire. The probe balloon is attached at its proximal end to 
the distal portion of the main shaft. An inflation/deflation port is 
formed in the hollow main shaft, distally of the proximal balloon 
connection, to communicate with the interior of the balloon for inflating 
and deflating the balloon. The distal end of the balloon is attached to 
the proximal end of the helical spring. A distal segment of the probe 
which projects beyond the balloon, includes the helical spring and portion 
of the support wire. The support wire is tapered within the helical spring 
to provide progressively increasing flexibility in a distal direction. The 
distal end of the probe is adapted to be bent to a curve and enables the 
probe to be selectively directed and steered by rotating the probe from 
its proximal end. 
The balloon is very thin. The diameter of the collapsed, folded balloon 
portion of the probe is very small and defines a very low profile. 
It is among the objects of the invention to provide a balloon dilatation 
catheter by which an angioplasty procedure can be performed on a stenosed 
blood vessel in which the lumen through the stenosis is too small to 
permit entry of a full size angioplasty catheter. 
Another object of the invention is to provide an angioplasty system which 
can be used to dilatate a stenosis in which the opening is as small as 
about 0.020 inches wide. 
Another object of the invention is to provide a probe having an outer 
diameter approximately the same as the diameter of a guide wire. 
A further object of the invention is to provide a catheter of the type 
described which allows the angioplasty procedure to be performed in cases 
which, before the invention, could not have been performed and would have 
required bypass surgery. 
Still another object of the invention is to provide a dilatation catheter 
which can be manipulated from the proximal end and can be steered with 
control adequate to be selectively guided through a patient's arterial 
tree to a precise intended location.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Among the difficulties which may arise in an angioplasty procedure is that 
the balloon dilatation catheter which has been advanced to the location of 
the arterial stenosis is too large, even with the balloon deflated, to be 
inserted into the stenosis. The present invention provides a slender 
probe-like catheter having a low profile with its balloon collapsed which 
is adapted to be steered to and inserted into such a narrow stenosis. 
As shown in FIG. 1 the dilatation probe 12 is of very slender construction 
having a cross-section approximately equal to that of a small diameter 
guide wire. 
The dilatation probe 12 has a balloon 26 which, when collapsed, defines a 
small cross-sectional configuration so that it can pass through tight 
stenoses. In its collapsed configuration the probe balloon 26 as well as 
the remaining portions of the probe 12 define an outer diameter 
corresponding to that of a small diameter guide wire. As will be described 
in further detail, when a conventional full size dilatation catheter 
cannot be advanced into the lumen of the stenosis, the probe 12 can be 
directed to and passed within the stenosis. The probe balloon 26 then is 
inflated to effect the dilatation. 
The probe 12, illustrated in FIG. 1, is of the order of about 180 
centimeters when used in coronary arteries with a percutaneous femoral 
artery approach. 
The probe 12 has a relatively long proximal segment 28 which is formed from 
narrow, solid wall tubing, such as hypodermic tubing. In the illustrative 
embodiment, the proximal segment 28 may be of the order of 150 centimeters 
long. The proximal segment 28 is rigid torsionally so that it can transmit 
substantially fully to its distal end rotational motion imparted to the 
proximal end. As will be described, the distal tip of the probe can be 
bent to a preset curve. Rotation applied to the probe can be controlled to 
selectively direct and steer the curved distal end of the probe as it is 
advanced. The proximal segment 28 also is flexible and can bend 
longitudinally to follow the curvature of the patient's arterial system. 
Preferably the proximal segment 28 of the probe 12 is sufficiently 
flexible that it can bend to follow the curve of a patient's aortic arch 
which has a radius of the order of between 2.5 to 3.5 inches in an adult. 
As shown more clearly in enlarged FIG. 2, in the preferred embodiment of 
the invention the hollow tubular segment 28 has an outer diameter of 0.018 
inches, a wall thickness of about 0.002 inches and an internal diameter 
passage 30 of 0.014 inches. A conventional fitting 32 is secured to the 
proximal end of segment 28 to facilitate connection with an 
inflation/deflation device, such as a syringe (not shown). 
The probe 12 includes a distal segment 34 which extends from the distal end 
of the proximal segment 28 to the distal end of the probe 12. The distal 
segment 34 includes a narrow diameter elongate support wire 44 which is 
connected to and extends distally of the proximal segment 28. The support 
wire 44 is connected to the proximal tubing 28 by a short transition tube 
36. The transition tube 36 is about one-half inch long and also is formed 
from slender, flexible hypodermic tubing with a smaller diameter than the 
proximal tube 28. In the illustrative embodiment, the transition tube 36 
is formed from hypodermic tubing having an outer diameter of 0.014 inches, 
a wall thickness of 0.003 inches and an inner diameter of 0.008 inches. 
The proximal end of the tubing 36 is received within the distal end of the 
internal passage 30 of the proximal segment 28 and is secured thereto as 
by soldering or brazing. The solid support wire 44 is attached to the 
distal end of the transition tube 36. The wire 44, which in the 
illustrative embodiment is very slender, preferably 0.008 inches diameter, 
is received in the distal end of the passage 38 of the tubing 36 and is 
secured by soldering or brazing. The support wire 44 plugs the distal end 
of the tubing 36. In order to permit the balloon 26 to be inflated and 
deflated, the transition tube 36 is provided with apertures 46 on opposite 
sides of the tube wall to provide communication with the internal passages 
38, 30 of the probe. The apertures 46 may be defined by forming a pair of 
longitudinal slots in the wall of the tubing 36. The support wire 44 
provides support for the probe balloon 26 and also extends distally beyond 
the balloon 26, to form the core of a leader segment 48. The leader 
segment includes a helically wound radiopaque coil spring 50 which is 
attached to the distal end of the core wire 44 in a manner described 
below. 
The probe balloon 26 is formed by molding high strength polymeric material 
in a manner which provides a thin balloon wall not greater than about 
0.001 inches thickness and, preferably, having a thickness of the order of 
0.0005 inches. The balloon may be manufactured as described in U.S. Pat. 
No. 4,490,421 issued Dec. 25, 1984 and reference is made thereto for 
further details concerning the manufacture of the balloon. 
As shown in enlarged detail in FIG. 3, the balloon includes a main 
cylindrical portion 52. In the illustrative embodiment, the probe balloon 
26 preferably has an outer diameter of 1.3 millimeters. As mentioned 
above, the balloon is formed from a high strength material which will not 
tend to stretch when inflated. The length of the balloon 26 may be of the 
order of 15 millimeters. The balloon is formed to include tapering 
portions 54, 56 at the proximal and distal ends respectively. The distal 
tapering portion 56 merges into a narrowed neck 58 which fits snugly about 
and against the proximal end of the coil spring 50. The distal neck 58 of 
the probe balloon 26 is adhesively attached to the coil spring 50. As will 
be described in further detail, the proximal end of the coil spring is 
soldered securely to the core wire at the region where the distal neck 58 
of the probe balloon 26 is joined. The proximal tapering portion 54 merges 
into a narrowed proximal neck 60. 
In order to communicate the interior of the probe balloon 26 with the 
inflation/deflation passages 30, 38 of the tubing, an extension sleeve 62 
is adhesively attached to the proximal neck 60. The extension sleeve 62 
extends proximally over the support wire 44. The proximal end of the 
extension sleeve 62 preferably is formed from the same material as the 
balloon 26 and is securely and adhesively attached to the outer surface of 
the transition tube 36, where it joins the main tube 28. The extension 
sleeve 62 defines an annular passage 64 about the support wire 44. The 
annular passage 64 provides communication between the apertures 46 and the 
interior of the balloon 26 for inflation and deflation of the balloon. 
As shown in FIG. 3 the leader segment 48 which extends distally of the 
balloon 26 is of increasing flexibility in a distal direction to provide a 
relatively soft, flexible leading tip which reduces the chance of trauma 
or injury to the blood vessel. In the illustrative embodiment the leader 
segment is about 3 centimeters long. The coil spring 50 is soldered, at 
its proximal end to the support wire 44, as indicated at 66. The distal 
end of the support wire 44 also is soldered to the coil spring 50 as 
indicated at 68. Soldered joint 68 and the distal tip 69 of the support 
wire 44 terminate short of the distal tip of the coil spring 50. The 
distal tip 70 of the coil spring 50 may extend about five millimeters 
beyond the soldered joint 68 and defines a highly flexible bumper tip. A 
rounded weld bead 67 is formed at the distal tip of the spring 50. The 
leader segment 48 is of increasing flexibility in a distal direction. The 
support wire 44 is taper ground and, for example, may be ground smoothly 
to a 0.002 inch diameter at its distal tip 69. 
The distal tip 70 of the coil spring 50 includes a flexible and bendable 
stainless steel shaping ribbon 71 which is secured to the distal tip 69 of 
the support wire at one end, and to the distal weld bead 67 at its other 
end. The shaping ribbon is of slender, rectangular cross section, of the 
order of 0.001 inches by 0.002 inches. The shaping ribbon is adapted to be 
bent to a desired curve and to retain that curve when relaxed. The preset 
curve enables the probe 12 to be steered by rotation of the probe from its 
proximal end. The probe can be rotated to direct the prebent distal tip 70 
in selective directions as desired within the patient's blood vessels. 
The probe also is provided with a radiopaque marker band 72 which 
preferably is formed from platinum. The marker band 72 is located 
proximally of the main portion of the balloon 26. In the illustrative 
embodiment it is securely attached to the support wire 44. The marker band 
72 provides a means by which the physician can verify, fluoroscopically, 
the position of the probe balloon 26. 
In order that the probe may be passed through the lumen of a catheter which 
may guide the probe to the coronary arteries, the probe balloon 26 also 
must be collapsible to a shape and size which can be passed through the 
lumen of that guiding catheter. The invention accomplishes these 
objectives by using the slender, small diameter support wire 44 extending 
through the balloon and by using a balloon with a very thin but high 
strength wall. When the probe 12 is to be inserted through the guiding 
catheter, the balloon 26 first is collapsed by applying suction, such as 
by a syringe, to the fitting 32. The balloon 26 and the extension sleeve 
62 collapse, tending to form radially projecting wings as illustrated in 
FIGS. 3A-1 and 3B-1, respectively. The wings 62W and 26W wrap about the 
support wire 44 when the probe is advanced through the main lumen of the 
guiding catheter. The wings 26W may wrap about the core wire 44 either in 
an S-shaped configuration suggested in FIG. 3A-2 or in a C-shaped 
configuration shown in FIG. 3A-3. In either configuration the overall 
diameter through the collapsed and folded balloon portion of the probe 12 
includes six layers of the balloon material in addition to the diameter of 
the support wire 44. In accordance with the present invention, the balloon 
is formed from a high strength thin material having a wall thickness 
preferably not more than about 0.001". Thus, the aggregate diameter of six 
balloon layers plus the support wire is about 0.014 inches. The probe 
balloon thus is collapsible to a diameter which is about one fourth of its 
inflated diameter and which can pass easily through the main lumen of the 
guiding catheter. 
In use a larger diameter guiding catheter through which the dilatation 
probe 12 can be passed is inserted initially in the patient's arterial 
system usually through the femoral artery and is advanced through the 
aortic arch to locate the distal tip of the guiding catheter at the 
coronary ostium leading to the coronary artery or into the coronary artery 
to be treated. After the larger guiding catheter has been positioned the 
probe 12 is advanced through the larger catheter with its balloon 26 in a 
collapsed configuration illustrated in either of FIGS. 3A-2 or 3A-3. The 
diameter of the probe 12 is about the same as a conventional guide wire. 
The dilatation probe 12 thus can be advanced out of the distal opening of 
the guiding catheter and the balloon 26, in its collapsed configuration, 
can be inserted into and through the stenosis. The dilatation probe 
balloon 26 then may be inflated under pressure to expand forcefully the 
probe balloon 26 to its maximum diameter thereby enlarging the passageway 
through the stenosis. 
A marker band 72 on the probe provides a means by which its position in the 
artery can be verified fluoroscopically. 
When the probe balloon 26 has been inflated to enlarge the opening through 
the stenosis the probe balloon 26 is collapsed by aspirating the probe. 
The probe then may be withdrawn from the patient. 
As described above, one of the features of the probe 12 is the increased 
flexibility of the distal segment 34 of the probe. The proximal segment 
28, as described, is sufficiently flexible so that it can bend relatively 
easily through the aortic arch. The bend from the aorta, into the coronary 
ostium and thereafter through the coronary arteries are sharper and 
shorter radiused. The length of the more flexible distal segment 34 is 
sufficient so that the probe balloon can reach deeply into the arterial 
tree without requiring the stiffer proximal tubing 28 to pass through 
relatively sharp bends, such as the bend from the guide catheter to the 
coronary ostium. The distal segment 34, which consists substantially of 
the thin, flexible support wire 44 is able to make the relatively sharp 
bends with ease. Thus, the only portion of the probe 12 which actually 
enters the coronary artery is that which includes the slender support wire 
44. This support wire is very flexible and is more easily bent to be able 
to negotiate shorter radius bends encountered in the coronary arterial 
tree. 
The probe is highly steerable due in large measure to the solid wall of the 
tubing in the elongate proximal segment 28 of the probe. The tubing is 
substantially torsionally rigid and tends to transmit substantially all of 
its rotation applied at the proximal end to the distal end. Although the 
intermediate segment of the probe, which includes the slender 0.008 inch 
diameter wire is too small a diameter to effectively transmit torque over 
relatively long distances, the distal segment 34 is relatively short, 
preferably about twenty-five centimeters and, therefore, does not have too 
great of an adverse effect on the torque transmission from the proximal 
end of the probe to the distal end. The distal segment preferably is no 
longer than about 25 centimeters, as compared to the solid wall tubular 
proximal segment which is approximately 150 centimeters long. Thus, by 
forming a bend in the distal tip 70 of the leading segment, the direction 
of the probe 12 can be controlled by rotating the probe from the proximal 
end. 
From the foregoing it will be appreciated that the invention provides a 
system and method by which the angioplasty technique for treating arterial 
stenoses can be extended to certain stenoses which previously required 
coronary artery bypass surgery. Moreover, the invention provides a probe 
which can be steered to selectively pass through the branches of a 
patient's arterial tree. 
It should be understood, however, that the foregoing description of the 
invention is intended merely to be illustrative thereof and that other 
modifications and embodiments of the invention will be apparent to those 
skilled in the art without departing from its spirit.