Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2001-09-14
2004-08-17
Thanh, Loan H. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S103020
Reexamination Certificate
active
06776771
ABSTRACT:
BACKGROUND OF THE INVENTION
During a typical percutaneous transluminal coronary angioplasty (PTCA) procedure, a balloon catheter is transported to a stenotic region in an artery or related body lumen. Normally a balloon for PTCA has an oblong, cylindrical shape with a single chamber that can be inflated to open up the arterial passageway. Once the lumen has been opened up, the balloon is deflated and removed through the same path by which it entered. If an uninflated balloon is to be easily placed inside and transported through an anatomical lumen, such as a curved artery, it must be flexible enough to be able to follow the lumen curvature, while maintaining enough rigidity to avoid bunching up during its passage to the desired endoluminal location. Conventionally, a relatively rigid guide wire can be used to effect balloon placement. Once the balloon has been inflated, its flexibility problem becomes much more profound, as the balloon is now often too rigid to bend in conformance with the lumen wall. Such a balloon will have the tendency to straighten itself upon inflation, thus creating undesirable forces on the inner wall of the lumen.
In some situations, the chance for restenosis of a body lumen that has been dilated can still be great. To avoid the necessity of repeated PTCA procedures, the doctor will implant an endoluminal prosthesis, also known as a stent, into the patient's body lumen adjacent the stenotic region. The stent is intended as a permanent or semi-permanent structure that maintains an open passageway, thereby reducing the chance for restenosis. Typically, the stent is balloon expandable, and is mounted around the balloon, such that both can be inserted simultaneously. If the stent has to be placed into a curved section of the body lumen, it too will take this straightened shape from the expanding single chamber balloon, which could lead to possible puncture or similar damage to the lumen wall. Additionally, the inappropriate fit between stent and lumen wall could allow the stent to loosen and migrate to a different part of the lumen.
Rigid expansion of the balloon can cause other problems to occur as well. For example, during angioplasty, the balloon is inflated to such an extent that the lumen in which the balloon is placed becomes temporarily plugged. While this is not critical for rapid angioplasty or stent deployment procedures, or is not feasible with very small or very high pressure devices (such as in a carotid artery, where the lumen diameter is typically between 2.5 and 4 millimeters), it is of concern for devices used in larger cross-sectional area lumens, such as a patient's leg or aorta, where lumen diameters can be from approximately 8 to 25 millimeters. If the inflated balloon obstructs blood flow for too long (typically for more than a few seconds), permanent damage to downstream organs can occur due to ischemia, which is the cessation of blood flow through the lumen. Accordingly, it is often desirable to keep the patient's blood flowing through the lumen while the balloon is in the inflated state. This is preferable to cycling the balloon between an inflated and deflated state, as such action can place additional stress on an already compromised lumen wall.
Multiple chamber balloons have been introduced into the art to meliorate the difficulty in transporting relatively rigid catheters into body lumens with tortuous paths. For example, U.S. Pat. No. 5,019,042 to Sahota, and U.S. Pat. No. 5,415,635 to Bagaoisan et al. both describe multiple lobed balloon catheters that have one set of lobes that expand more than other sets. Similarly, the introduction of perfusion balloons, so named because of an open channel that extends through or around the balloon to permit continuous flow of blood, has partially solved the ischemia dilemma. Examples of perfusion balloons are described in U.S. Pat. No. 5,613,948 to Avellanet, and U.S. Pat. No. 4,909,252 to Goldberger, both of which include a perfusion channel extending axially through a single-chamber balloon with eccentrically mounted expansion fluid supply. There have additionally been attempts to combine perfusion features with flexible, multiple chamber balloons, as evidenced by some of the aforementioned patents. However, the size of the apertures leading into and out of the perfusion channel is such that blood throughput can be unacceptably low, which limits the amount of time the doctor has to perform the PTCA procedure, as well as create a pressure gradient that could assist in pushing the balloon farther downstream than intended. In addition, the relatively large profile of the uninflated assembly makes transport through small or highly curved body lumens difficult, while the multiple layers found in present balloon catheter construction make for expensive, damage-prone devices.
What is needed is a balloon catheter that can be hinged while inflated to better conform to the shape of the lumen in which it is disposed. What is additionally needed is a flexibly compliant balloon catheter that can mimic the shape of a path formed by a body lumen while the catheter is uninflated, thereby enhancing the ability of the catheter to be inserted into curved, tortuous lumen paths. What is furthermore needed is a balloon catheter of such construction that fabrication difficulties and susceptibility to damage are meliorated. What is also needed is a flexible balloon catheter that can maintain blood perfusion, even when the catheter is in its inflated configuration, and even when disposed in a curved or tortuous part of a body lumen.
SUMMARY OF THE INVENTION
These needs are met by the present invention, whereby a flexible balloon catheter according to the present invention is made of a series of short inflatable chambers in fluid communication with one another through connection to a common core that can transport a pressurized fluid to the chambers. In the context of the present invention, the term “flexible” and its variants is meant to convey that it is easier for the balloon (either expanded or unexpanded) to bend in flexure, or normal to its axial dimension, while traversing a curved body lumen than it would be if the multiple chambers and compliant link/hinge sections herein described were not employed. Similarly, the terms “inflatable”, “expandable” and their variants are used interchangeably throughout this disclosure to describe the ability of the balloon (and its separate chambers) to enlarge in response to the presence of a pressurized fluid. Even upon balloon inflation, the connections between the balloon's numerous short chambers remain compliant enough to follow the natural curvature of the lumen, without other forces than radial pressure against the inner wall of the artery. Balloon insertion through the tortuous paths associated with anatomical lumen becomes much more reliable, thereby significantly reducing the risk for damaging the lumen. Further, when the balloon is used in conjunction with a prosthetic stent, it becomes possible to place a longer stent in such a curved lumen, with the added assurance that after inflation the stent will be deployed following the natural curves of the lumen.
It is therefore an object of the invention that a balloon for angioplasty is made in short sections (or chambers) compliantly linked therebetween in order to improve the flexibility and adaptability in both the deflated as well inflated state such that the tendency of the sectioned balloon to straighten during inflation is reduced, thus improving its insertability into a curved body lumen.
It is a further object of the present invention to vary the length of the compliant links between each of the chambers so that flanges that make up the chamber side walls need not be spaced substantially parallel to its immediate neighbor on an adjacent chamber, thus permitting additional axial room, and hence flexibility, without changing the outer geometry of the inflated balloon assembly.
It is still another object of the present invention to provide a balloon catheter that includes a series of dis
Besselink Petrus Antonious
van Moorlegem Wilfried Franciscus Marcellinus
Dinsmore & Shohl LLP
Thanh Loan H.
Tuborg Engineering
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