Methods of angioplasty treatment of stenotic regions

Dilation catheters for use in administering treatments to relieve stenotic regions within a body lumen are described. In the invention, a novel catheter system having a balloon length of minimal length for treating distal arteries is utilized. In addition, novel methods for treating stenotic areas which are present in tortuous vessels, as well as hardened, or calcified stenotic portions are also described.

BACKGROUND OF THE INVENTION 
The present invention relates generally to the field of catheters. More 
specifically, the present invention relates to dilation catheters for use 
in administering treatments to relieve a stenotic region or to widen a 
constricted blood flow or tubular passage, such as the coronary artery, as 
well as other vessels. 
Percutaneous transluminal coronary angioplasty (PTCA), a procedure for 
treating a patient having a stenosis or constricted blood region in a 
coronary artery, has become a widely accepted therapeutic alternative to 
coronary arterial bypass surgery for many patients. PTCA increases the 
lumen by radial expansion. The main advantage of the PTCA procedure is in 
reducing morbidity and avoiding the immediate post-operative discomforts 
associated with coronary bypass surgery. 
However, the benefits of PTCA are restricted to those lesions accessible to 
the balloon dilation catheter. With standard balloon systems, certain 
lesions are inaccessible due to variations in the patient's anatomy and 
vasculature. Further, seducing side branches, tortuous vessels, and the 
more distal arteries have presented serious difficulties in the PTCA 
procedure because, due to its length, the balloon could not reach the 
stenotic region. 
When considering angioplasty as a method of treating stenotic regions, the 
morphology of the lesion is critical in determining whether the vessel 
will adequately dilate. If the stenosis is comprised primarily of fatty 
deposits, for example, it is possible to compress the stenosis radially 
outwardly, against the adjacent vessel wall, so as to increase the 
cross-sectional area of the vessel, and provide adequate perfusion through 
the vessel. If, however, the artery is hard, or the stenosis has 
calcified, the artery may be dissected if inflated with a standard 
dilation balloon. 
Performing a coronary angioplasty involves the difficulty of inserting a 
balloon catheter into the desired coronary artery. Most balloon catheters 
are too flexible for direct insertion into the patient's coronary artery. 
Accordingly, the standard angioplasty process begins with the insertion of 
a guide wire into the obstructed vessel, under local anesthesia. A guiding 
catheter, or sleeve is then slipped over the wire. The guiding catheter is 
designed to provide a conduit through which a balloon catheter is passed. 
The tip of the guiding catheter is not tapered so as to permit the 
unimpeded passage of the balloon catheter therethrough. 
The lesion may be approached with a guide wire by advancing the catheter 
and guide wire as a unit, or by advancing the guide wire first. Steering 
the tip of the wire is done by the surgeon or by an assistant. If the tip 
is moving in an undesired direction, then slightly withdrawing and 
torquing the guide wire will rotate the tip toward in desired direction. 
Once the wire is positioned, the balloon catheter may be advanced over the 
wire until it crosses the lesion. The balloon advances until it reaches 
the tip, which the surgeon has maintained in a fixed position in the 
distal artery. The cardiologist positions the balloon in the artery, 
expands the balloon, and then allows the balloon to depressurize to permit 
measurement of blood flow across the stenosis. 
The benefits of angioplasty are restricted to lesions accessible to the 
balloon dilation catheter. With currently available balloon systems, (2 mm 
or longer in length) certain lesions are inaccessible due to variations in 
the patient's anatomy and vasculature. Further, seducing side branches, 
tortuous vessels, and the more distal arteries have presented serious 
difficulties in the PTCA procedure because, due to its length, the balloon 
can not effectively seduce these stenotic regions. 
These difficult areas include, (1) the area immediately after the left main 
artery, in which there is a narrowing of the left anterior descending 
artery (LAD), (2) those areas of the heart where acute angled branching 
occurs along a bend in the artery, (3) lesions near the origin of the 
aortic artery and (4) bifurcation lesions. These special and difficult 
situations cannot adequately be treated with long catheters. Seducing such 
tortuous vessels is quite difficult using the standard, longer dilation 
balloons. 
SUMMARY OF THE INVENTION 
The dilation catheters of the present invention overcome many of the 
difficulties associated with ordinary prior art dilation catheters. The 
short length of this balloon lends itself to easy maneuverability, both 
during insertion and inflation. The short balloon directly attached on a 
wire increases its accessibility to distil narrowings. In some arteries, 
for example, the left anterior descending artery, there are many sharp 
bends and curves. Seducing such tortuous vessels can prove quite difficult 
using standard length dilation balloons. The short dilation balloon of the 
present invention advantageously are easier to manipulate through the 
arteries, both during insertion and inflation thereof. Thus, acute bends 
or branches may be crossed or dilated easier, quicker, with less trauma to 
the artery and with a substantial reduction in the risk of dissection. 
In addition, the short balloon does not impede the flow of blood in the 
left main artery while dilating a lesion in LAD. A reduction of blood flow 
in this artery even temporarily is very damaging to the heart. 
Further, when seducing a right coronary artery lesion, the longer balloon 
extends over the guide catheter which prevents inflation. Thus the surgeon 
must remove the guide during inflation and insert it back into the artery 
after deflation. This repetitive maneuver increases the risk of trauma to 
the ostium. The shorter balloon eliminates this risk since it is 
completely out of the guide and in the right coronary artery. 
The shorter balloon is also advantageous in seducing bifurcation lesions. 
This procedure requires the insertion of two balloons simultaneously. Two 
short balloons are easier to manipulate, maneuver, and place during this 
procedure than the long balloon. Again, a longer balloon is more likely to 
obstruct the proximal part of the artery before the bifurcation. 
The present long balloons can not perform all of these functions. The 
outcome of their inherit design limitations are unsuccessful angioplasties 
resulting in patients requiring open heart surgery. 
Further objects, features and other advantages of the present invention 
will become apparent from the ensuing detailed description, when 
considered together with the appended drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings in detail, wherein like reference numerals 
designate like elements throughout the several views thereof, there is 
shown generally at 10, in FIGS. 1-4, a dilation catheter embodying the 
present invention in a preferred form. The catheter 10 comprises a 
dilation balloon 11, having a distal end 12 which is fastened around an 
axially elongate guide wire 13. By attaching the dilation balloon 11 
directly on the wire 13, the catheter 10 is especially adapted for 
insertion into the most distal arteries which are much narrower than the 
main coronary artery. 
Advantageously, the dilation balloon 10 is attached to the wire 13 only at 
the distal end 12, leaving the wire 13 free to move within the catheter 
shaft 15. Preferably, the wire 13 extends the length of the catheter 10, 
and exhibits a small segment, referred to as an advance wire 20, which 
extends beyond the distal end 12 of the dilation balloon 10. The advance 
wire 20 may be of any suitable length, and may be preformed to any desired 
configuration to facilitate insertion of the catheter 10 and passage 
through the body lumen. 
The proximal end 21 of the dilation balloon 10 tapers to a diameter which 
approaches that of the wire 13 to form the shaft 15 of the catheter 10. 
Thus, the catheter shaft 15 is an extension of the dilation balloon 11. 
The catheter shaft 15 provides a path for conducting pressurized fluids 
into and out of the balloon 11 for selective expansion and deflation 
thereof. Preferably, the balloon 11 and shaft 15 of the catheter 10 are 
made of a non-distensible material so that it can only be inflated to 
expand to the constructed size. Further attempts to inflate such 
structures result in an increase in pressure, but no significant increase 
in diameter. 
The dilation catheter 10 illustrated in FIGS. 1-4 is particularly suited 
for performing methods of angioplasty treatment of stenotic regions of 
distal arteries. The balloon 11 of the present invention is materially 
shorter than conventional prior art angioplasty balloons. Such prior art 
catheters have a balloon length of two millimeters or more. In contrast, 
the balloon 11 of the present invention is considerably shorter with a 
length L preferably in the range of one-half (0.5) millimeter to one (1.0) 
millimeter. 
The angioplasty procedures of the invention are performed by surgeons 
employing catheters constructed in accordance with FIGS. 1-4. As noted 
above, these catheters advantageously have balloon lengths L of 
approximately 0.5 millimeter and 1.0 millimeter. In addition, benefits of 
the invention in certain angioplasty procedures will accrue using a 
catheter having a balloon length L of between 1.0 and 1.5 millimeter. 
In use, the catheter 10 is inserted into the body lumen until the dilation 
balloon 11 is proximate the stenotic area. Following several inflations 
and deflations, the balloon 11 is withdrawn across the lesion. The 
catheter 10 is left in place in the body lumen for a short period of time, 
referred to as the post-dilation observation period, to ensure that the 
lumen will not collapse. If re-occlusion does occur, then the same balloon 
catheter 10, or a different balloon catheter (not shown), can be passed 
across the lesion and the vessel redilated. This is particularly 
significant in dealing with the more distal arteries, to which access is 
often times difficult. 
The short balloon catheter 10 is extremely useful in negotiating the 
numerous areas of the heart where there are many acute angles in tortuous 
vessels and is particularly useful when dilating these same vessels. The 
short balloon 11 readily expands to dilate stenotic areas, but is of such 
a length so as not to impede blood perfusion in the proximal arterial 
branches while the lumen is being dilated. The catheter shaft 15 may be 
straight, or it may be preformed with different shapes and configurations 
to facilitate insertion through the body lumen. 
FIG. 5 illustrates a prior art catheter 24. As noted above, this prior art 
catheter 24 has a balloon 25 whose length is at least 2 millimeters long. 
As shown in FIG. 5, the prior art balloon 25 is shown inflated to dilate a 
stenotic area of the left anterior descending artery 26 immediately 
adjacent the left main artery 27. As shown, because of its length, the 
prior art balloon 25 blocks a portion of the left main artery 27. Reducing 
the blood flow in this artery, even temporarily, will damage the heart. 
FIG. 6 illustrates the short balloon catheter 10 of the invention in an 
inflated state, within the same left anterior descending artery 26. 
Significantly, as illustrated, the short balloon catheter 10 of the 
invention does not obstruct the proximal part of the left main artery, and 
thus it does not impede the flow of blood in this artery. 
FIG. 7 further illustrates the left anterior descending artery 26a which 
contains many sharp bends and curves before the catheter can reach a 
lesion shown at 28. Seducing such tortuous vessels 26a can prove quite 
difficult using prior art length dilation balloons. The short dilation 
balloon catheter 10 is very advantageous since it is more maneuverable and 
easier to manipulate through a tortuous artery 26a, both during insertion 
and inflation. Thus, the acute bends or branches of artery 26a are crossed 
or dilated easier, quicker, with less trauma to the artery and with a 
substantial reduction in the risk of dissection. Also, the short balloon 
catheter 10 does not force the artery 26a to straighten as the balloon is 
inflated, thus reducing the risk of dissection of the artery. 
Angioplasty treatment methods of a stenotic region of the right coronary 
artery is illustrated in FIGS. 8 and 9. As shown in FIG. 8, if the guide 
catheter 30 remains in place, the balloon of prior art catheter 24 will 
partly remain in the sheath or guide catheter 30, during inflation of a 
stenosis 31 of the right coronary artery 32 proximal to the ostium of the 
right coronary artery. As a result, in the prior art method, the surgeon 
must first pull the distal end 34 of the guide catheter 30 out of the 
ostium of the right coronary artery 32 before inflation of the prior art 
catheter balloon catheter 24 and put it back into the artery after 
deflation. This maneuver can cause trauma to the ostium of the right 
coronary artery. In contrast, as shown in FIG. 9, in the treatment method 
of this invention, the balloon 11 of the short catheter 10 is completely 
out of the guide catheter 30. As a result, the guide catheter 30 need not 
be removed from the right coronary artery during inflation of the short 
balloon catheter 10. 
Another improved method of performing angioplastic treatment according to 
the present invention is illustrated in FIG. 10. This Figure illustrates a 
bifurcation lesion 35. During this procedure, the surgeon simultaneously 
inserts two balloon catheters. In the prior art (not shown) the prior art 
balloon catheter with its balloon length of 2 millimeters or longer tends 
to obstruct the proximal portion 36 of the artery before the bifurcation 
into the two arteries 37 and 38. In contrast, two short balloon catheters 
10a and 10b constructed in accordance with FIGS. 1-4 do not, as shown in 
FIG. 10, obstruct the artery 36. Moreover, the shorter balloon catheters 
10a and 10b will be easier for the surgeon to manipulate and position than 
the prior art balloon catheters. 
It will be appreciated that certain structural variations may suggest 
themselves to those skilled in the art. The foregoing detailed description 
is to be clearly understood as given by way of illustration, the spirit 
and scope of this invention being limited solely by the appended claims.