Device and method for transecting a coronary artery

The present invention is a device for creating a transection in a coronary artery. Structurally, the present invention includes an inflatable balloon mounted at the distal end of a catheter. A single blade is mounted to project radially from the surface of the balloon and is aligned with the balloon's longitudinal axis. Additionally, a series of radio-opaque markers are distributed on the balloon's surface. Operationally, the balloon is advanced, using the catheter, until it is positioned at the approximate site of the desired transection. An X-ray imaging system is then used to visualize the radio-opaque markers, allowing the balloon and blade to be oriented radially and longitudinally at the location required for the transection. The balloon is then inflated, forcing the blade to incise the artery wall and creating the desired transection. The transection creates a new artery composed partially of the old artery and partially of the surrounding fibrous tissue.

FIELD OF THE INVENTION 
The present invention pertains generally to surgical instruments. More 
particularly, the present invention pertains to invasive surgical devices 
which are useful for the incision of a coronary artery. The present 
invention is particularly, though not exclusively, useful to transect the 
side of a coronary artery which is closest to the heart to effectively 
form a new artery. 
BACKGROUND OF THE INVENTION 
Over the years, the blockage of human arteries has become a leading medical 
concern. This is so because a variety of serious medical complications may 
result from arterial blockages that reduce blood flow through an affected 
artery. More specifically, an arterial blockage may result in damage to 
the tissue that relies on the artery for its blood supply. For example, if 
a blockage occurs in an artery leading to the brain, a stroke may result. 
Similarly, if a blockage occurs in an artery which supplies blood to the 
heart, a heart attack may result. 
Typically, arterial blockages are caused by the build-up of atherosclerotic 
plaque on the inside wall of the artery. These blockages, which are 
commonly called stenoses, may result in a partial, or even complete, 
blockage of the artery. As a result of the dangers associated with these 
arterial blockages, a variety of procedures have been developed to treat 
them. An angioplasty procedure is, perhaps, the most commonly used 
procedure for such treatment. An angioplasty procedure involves the use of 
an inflatable angioplasty balloon to dilate the blocked artery. A typical 
inflatable angioplasty device, for example, is disclosed in U.S. Pat. No. 
4,896,669 which issued to Bhate et al. for an invention entitled "DILATION 
CATHETER." The Bhate et al. angioplasty device includes an inflatable 
angioplasty balloon which is insertable into a peripheral artery of a 
patient for positioning across a stenosis. Once positioned, the 
angioplasty balloon is then inflated to dilate the stenosis within the 
artery thereby improving the blood flow through the artery. 
While angioplasty balloons have been widely accepted for the treatment of 
stenoses, recent studies have indicated that the efficacy of the dilation 
of a stenosis is enhanced by first, or simultaneously, incising the 
material that is creating the stenosis. Not surprisingly then, angioplasty 
balloons have been equipped with cutting edges, or atherotomes. These 
cutting edges are intended to incise the stenosis during the angioplasty 
procedure to facilitate dilation of the stenosis. An example of an 
angioplasty balloon equipped with cutting edges is disclosed in U.S. Pat. 
No. 5,196,024 which issued to Barath for an invention entitled "BALLOON 
CATHETER WITH CUTTING EDGE," and which is assigned to the assignee of the 
present invention. The Barath device includes an inflatable angioplasty 
balloon with a number of atherotomes mounted longitudinally on its 
surface. During the inflation of the Barath balloon, the atherotomes 
induce a series of longitudinal cuts into the stenotic material as the 
balloon expands to dilate the stenosis. As a result of such longitudinal 
cuts, the stenosis is more easily dilated, and the likelihood of damaging 
the artery during dilation is significantly reduced. 
In general, the use of angioplasty has been found to be an effective means 
for reducing arterial blockage associated with the buildup of 
atherosclerotic plaque. In some cases, however, it has been found that the 
atherosclerotic plaque which forms a particular stenotic segment may be 
too rigid to be effectively dilated. In such cases, traditional 
angioplasty techniques have been found to be largely ineffective and, in 
some cases, even harmful. As a result, a number of differing techniques 
have been developed for the treatment of hardened, or rigid stenotic 
segments. One such technique, which is specifically targeted at the 
coronary arteries, is transection. Transection, as applied to the coronary 
arteries, involves the creation of an elongated incision within the artery 
where the targeted stenosis is located. More specifically, a 
longitudinally oriented incision is created which spans the targeted 
stenosis and is positioned along the wall of the artery which is closest 
to the cardiac muscle. Creation of the incision causes the formation of a 
new arterial segment, with the new segment being composed partially of the 
previously occluded artery, and partially of the fibrous material of the 
heart. The new arterial segment evolves from the blood clot that forms 
when the arterial wall is transectioned. Effectively then, transection 
overcomes the occluding effect of atherosclerotic plaque by allowing the 
occluded artery to expand into the fibrous material of the heart. A 
description of this procedure is provided in "Coronary Artery Incision and 
Dilation" Archives of Surgery, December 1980, Volume 115, Pages 1478-1480, 
by Banning Gray Lary, M.D. 
For the transection procedure to succeed, it is critical that the incision 
be made on the portion of the coronary artery which directly faces the 
heart muscle. This is so because the transection procedure involves 
cutting through the arterial wall, a procedure which would ordinarily 
result in an uncontrolled blood loss and, perhaps, the death of the 
patient. However, if the transection is made on the portion of the artery 
against the heart, the epicardial tissues which cover the heart and the 
coronary arteries prevent the loss of blood, allowing the new artery to 
form. 
Unfortunately, in the context of a transection procedure, currently 
available angioplasty balloons have a particular disadvantage. More 
specifically, practice has shown that it is generally difficult to direct 
the atherotomes of a traditional angioplasty balloon with the accuracy 
required for a successful transection. Instead, when a traditional 
angioplasty balloon is employed, there is an ever present danger that the 
transection will be created in a part of the arterial wall that is not 
adjacent to the heart. Specifically, there is a present inability to 
precisely control the position an angioplasty balloon and cutting edge in 
both a longitudinal and a rotational direction. 
Another disadvantage associated with the use of traditional angioplasty 
balloons for the creation of coronary transections involves the depth of 
the created incision. More specifically, practice has demonstrated that 
effective transection requires that the created incision be deep enough to 
allow the new artery to form. 
Accordingly, it is an object of the present invention to provide a device 
for longitudinally transecting a coronary artery. It is a further object 
of the present invention to provide a device capable of accurately 
locating a transection, in both a longitudinal and a rotational direction, 
within an artery. It is another object of the present invention to provide 
a device capable of producing a transection at a depth favorable to 
arterial formation. It is yet another object of the present invention to 
provide a device for transecting a coronary artery which is relatively 
easy to use, easy to manufacture, and comparatively cost effective. 
SUMMARY OF THE PREFERRED EMBODIMENTS 
The present invention is a device for transecting a coronary artery. 
Structurally, the present invention includes an inflatable balloon mounted 
at the distal end of a flexible catheter. The balloon is preferably of the 
traditional angioplasty type and is connected in fluid communication with 
an inflation lumen which passes through the catheter. A single blade, or 
atherotome, is attached to the surface of the inflatable balloon and 
aligned with the longitudinal axis of the balloon. The blade has an 
elongated cutting edge which extends radially away from the surface of the 
balloon. Thus, when the angioplasty balloon is positioned within a 
coronary artery and inflated, the cutting blade moves radially outward to 
transect the arterial wall. 
A series of radio-opaque markers are attached to the surface of the 
inflatable balloon. The markers are distributed on the balloon using a 
configuration which allows the longitudinal and rotational position of the 
cutting blade to be identified using a standard X-ray imaging system. In 
this way, by viewing the X-ray imaging system while simultaneously 
positioning the device within a patient's coronary artery, the precise 
positioning of the cutting blade required for the successful transection 
may be attained. 
Preferably, the catheter is formed with a guidewire lumen which extends 
through the length of the catheter and through the inflatable balloon. The 
guidewire lumen is dimensioned to receive a guidewire, which may be chosen 
from a wide range of medical guidewire types. 
Operation of the present invention begins with insertion the guidewire into 
the artery of a patient and subsequent advancement of the guidewire until 
the distal end of the guidewire is positioned near the site of the 
stenosis targeted by the transection procedure. The extracorporeal end of 
the guidewire is then threaded through the guidewire lumen of the device 
of the present invention. The balloon and catheter of the device are then 
advanced over the guidewire and into the artery of the patient. 
Specifically, the balloon is advanced over the guidewire until it is near 
the stenotic segment that is targeted by the transection procedure. At 
this point, the X-ray imaging system is activated and used to visualize 
the device within the patient's body. Using the X-ray image, and in 
particular, by noting the position and orientation of the radio-opaque 
markers, the device is positioned longitudinally and rotationally to 
orient the blade over the desired location of the transection. The balloon 
is then inflated and the expanding balloon forces the blade to incise the 
wall of the artery creating the desired transection. 
After the initial transection has been completed, the angioplasty balloon 
is deflated and may be re-positioned within the artery to perform yet 
another transection. Using this step-and-repeat manner, a transection 
having a substantial length may be created. Once completed, the 
transection functions as a new artery, with part of the artery being 
composed of the formerly occluded artery and part of the artery being 
composed of the surrounding fibrous tissue, which occurs from the 
maturation of the initial blood clot.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention is a device for transecting a coronary artery. The 
structural components of the present invention are best appreciated by 
initial reference to FIG. 1 where the device of the present invention is 
shown and generally designated 10. In more detail, it may be seen that 
device 10 includes a catheter 12 having a distal end 14 and a proximal end 
16. An inflatable balloon 18 is attached to the distal end 14 of the 
catheter 12. The balloon 18 is preferable of the traditional angioplasty 
type and is connected in fluid communication with an inflation lumen 20 
which passes through the catheter 12. A fluid pump 22 is attached to the 
proximal end 16 of the catheter 12. The fluid pump 22, like the balloon 
18, is attached in fluid communication with the inflation lumen 20. 
Functionally, the connection between the balloon 18, inflation lumen 20 
and fluid pump 22, allows the fluid pump 22 to selectively pass fluid 
through the catheter 12 to selectively inflate the balloon 18. 
Specifically, the fluid pump 22 may be used to cause the balloon 18 to 
move between a first configuration, where the balloon 18 has a reduced 
radius and a second configuration where the balloon 18 has an increased 
radius. 
Continuing with FIG. 1, it may be seen that the present invention includes 
a blade, or atherotome 24. The blade 24 is formed with a sharpened cutting 
edge 26 and a base 28. Blade 24 is longitudinal aligned with balloon 18 
and the base 28 of the blade 24 is attached to the surface of the balloon 
18. Importantly, the blade 24 is dimensioned so that cutting edge 26 
exceeds the surface of the balloon 18 by a distance chosen so that the 
blade 24 may incise the wall of a coronary artery. Generally, the blade 24 
may be fabricated from a range of materials including plastics and 
composites. For the purposes of the present invention, however, it has 
been found especially practical to fabricate the blade 24 from stainless 
steel. 
Preferably, the present invention includes a guidewire, such as the 
guidewire 30 shown in FIG. 1. The guidewire 30 is generally of the type 
generally used for angioplasty type procedures and is insertable through a 
guidewire lumen 32 formed in the catheter 12. 
Finally, the present invention includes a series of radio-opaque markers 
each mounted to the outer surface of the balloon 18. More specifically, 
the present invention includes a distal marker 34, mounted near the distal 
end of the balloon 18, a proximal marker 36 mounted near the proximal end 
of the balloon 18, and an intermediate marker 38 mounted between the 
distal marker 34 and the proximal marker 36. Importantly, the markers 34, 
36 and 38 are made of a material which is opaque to x-rays and are 
separated longitudinally, as just described, as well as radially. The 
longitudinal separation is apparent from examination of FIG. 1 where the 
longitudinal separation between distal marker 34 and intermediate marker 
38 is shown and designated 40. Similarly, the longitudinal separation 
between proximal marker 36 and intermediate marker 38 is shown and 
designated 42. The radial separation between the markers 34, 36 and 38 is 
apparent from examination of FIG. 2 where the radial separation between 
distal marker 34 and proximal marker 36 is shown and designated 44. 
Similarly, the radial separation between proximal marker 36 and 
intermediate marker 38 is shown and designated 46. 
OPERATION 
Operational deployment of the present invention is best appreciated by 
initial reference to FIGS. 4A and 5A. More specifically, operation of the 
present invention begins with insertion of the distal end of the guidewire 
30 into an artery, such as artery 48. The guidewire 30 is then advanced 
until the distal end of the guidewire 30 is positioned slightly past the 
region 50 where the initial transection is to be performed. Once the 
distal end of the guidewire 30 has been prepositioned, the guidewire's 
proximal, extracorporeal end, is inserted into the guidewire lumen 32. 
Insertion of the guidewire 30 into the guidewire lumen 32 allows the 
device 10 to be advanced over the guidewire 30 and into the artery 48. It 
will be appreciated that during advancement of balloon 18 through the 
artery 48, care must be taken to not unnecessarily incise the wall of 
artery 48 with the blade 24. This can be done in several ways. For one, as 
shown in FIG. 2b, the cutting edge of blade 24 can be protected by the 
collapsed balloon 18. In another way, a sheath catheter (not shown) can be 
used to position the balloon 18 near the stenosis. In either way the 
device 10 is positioned in the artery 48 so that the balloon 18 located 
near the region 50 where the initial transection is to be performed. 
With the initial positioning of the balloon 18 complete, an X-ray imaging 
system 62 is activated to visualize the device 10 within the artery 48. In 
particular, the X-ray imaging system 62 provides a visual indication of 
the relative locations of the distal marker 34, proximal marker 36 and 
intermediate marker 38. Importantly, by examination of the these relative 
locations, the longitudinal and rotational position of the balloon 18 and, 
in particular the cutting edge 26, may be accurately determined. In this 
way, and as shown in FIG. 5A, the balloon 18 is oriented so that the 
cutting edge 26 is directed at the portion of the arterial wall 52 which 
is affixed to the cardiac tissue 54. 
Once the cutting edge 26 has been accurately positioned using the X-ray 
imaging system 62, the fluid pump 22 may be activated to fill the balloon 
18. Filling of the balloon 18, as best appreciated by reference to FIG. 
5B, causes the cutting edge 26 to incise the arterial wall 52. 
Importantly, the incision 56 is positioned in the region of the arterial 
wall 52 which is adjacent to the cardiac tissue 54. In this way, the 
incision 56 and the balloon 18 enlarge the lumen 58 of the arterial vessel 
48 without causing an uncontrolled loss of blood. 
Creation of the incision 56 is followed by activation of the fluid pump 22 
to withdraw fluid from the balloon 18 resulting, of course, in the 
deflation of the balloon 18. Deflation of the balloon 18 withdraws the 
cutting edge 26 of the blade 24 from the arterial wall 52. At this point, 
the device 10 may be withdrawn from the artery 48 completing the 
transection procedure and leaving the artery substantially as shown in Fib 
5c with the incision 56 which eventually heals to enlarge the lumen of the 
artery. Alternatively, and as shown in FIG. 4B, the balloon 18 and cutting 
edge 26 may be repositioned to a region 60 where a subsequent transection 
is to be performed. Once the repositioning has been performed, the X-ray 
imaging system may be reactivated and the longitudinal and rotational 
position of the cutting edge 26 may be accurately selected by reference to 
the relative positions of the distal marker 34, proximal marker 36 and 
intermediate marker 38. The balloon 18 may then be reinflated to effect 
further transection of the arterial wall 52. In many cases, it will be 
desirable to use the previously described method to produce a single 
transection of selectable length. 
While the particular device for transecting a coronary artery as herein 
shown and disclosed in detail is fully capable of obtaining the objects 
and providing the advantages herein before stated, it is to be understood 
that it is merely illustrative of the presently preferred embodiments of 
the invention and that no limitations are intended to the details of 
construction or design herein shown other than as described in the 
appended claims.