Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
2000-04-28
2004-03-16
Milano, Michael J. (Department: 3731)
Surgery
Instruments
Internal pressure applicator
Reexamination Certificate
active
06706053
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to filtering devices and systems which can be used when an interventional procedure is being performed in a stenosed or occluded region of a blood vessel to capture embolic material that may be created and released into the bloodstream during the procedure. More precisely, the present invention is directed to filtering devices that include a superelastic metal that is alloyed with a ternary element to obtain a desired hysteresis curve that maximizes performance of the filtering devices.
The embolic filtering devices and systems of the present invention are particularly useful when performing balloon angioplasty, stenting procedures, laser angioplasty or atherectomy in critical vessels, particularly in vessels such as the carotid arteries, where the release of embolic debris into the bloodstream can occlude the flow of oxygenated blood to the brain or other vital organs, which can cause devastating consequences to the patient. While the embolic protection devices and systems of the present invention are particularly useful in carotid procedures, the inventions can be used in conjunction with any vascular interventional procedure in which there is an embolic risk.
A variety of non-surgical interventional procedures have been developed over the years for opening stenosed or occluded blood vessels in a patient caused by the build up of plaque or other substances on the wall of the blood vessel. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter. In typical carotid percutaneous transluminal angioplasty (PTA) procedures, a guiding catheter or sheath is percutaneously introduced into the cardiovascular system of a patient through the femoral artery and advanced through the vasculature until the distal end of the guiding catheter is in the common carotid artery. A guide wire and a dilatation catheter having a balloon on the distal end are introduced through the guiding catheter with the guide wire sliding within the dilatation catheter. The guide wire is first advanced out of the guiding catheter into the patient's carotid vasculature and is directed across the arterial lesion. The dilatation catheter is subsequently advanced over the previously advanced guide wire until the dilatation balloon is properly positioned across the arterial lesion. Once in position across the lesion, the expandable balloon is inflated to a predetermined size with a radiopaque liquid at relatively high pressures to radially compress the atherosclerotic plaque of the lesion against the inside of the artery wall, thereby dilating the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation catheter can be withdrawn from the patient's vasculature and the blood flow resumed through the dilated artery. As should be appreciated by those skilled in the art, while the above-described procedure is typical, it is not the only method used in angioplasty.
Another procedure is laser angioplasty which uses a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which cutting blades are rotated to shave the deposited plaque from the arterial wall. A vacuum catheter is usually used to capture the shaved plaque or thrombus from the blood stream during this procedure.
In the procedures of the kind discussed above, abrupt reclosure or restenosis of the artery may occur over time, which may then require another angioplasty procedure, a surgical bypass operation, or some other method of repairing or strengthening the stenosed area. To reduce the likelihood of the occurrence of abrupt reclosure and to strengthen the area, a physician can implant an intravascular prosthesis, commonly known as a stent, for maintaining vascular patency inside the artery across the lesion. The stent is crimped tightly onto the balloon portion of a catheter and transported in its delivery diameter through the patient's vasculature. At the deployment site, the stent is expanded to a larger diameter, often by inflating the balloon portion of the catheter.
Prior art stents typically fall into two general categories of construction. The first type of stent is expandable upon application of a controlled force, as described above, through the inflation of the balloon portion of a dilatation catheter which, upon inflation of the balloon or other expansion means, expands the compressed stent to a larger diameter to be left in place within the artery at the target site.
The second type of stent is a self-expanding stent formed from, for example, shape memory or superelastic alloys including nickel-titanum (NiTi) alloys, which automatically expand from a collapsed state when the stent is advanced out of the distal end of the delivery catheter into the body lumen. Such stents manufactured from expandable heat sensitive materials allow for phase transformations of the material to occur, resulting in the expansion and contraction of the stent.
The above non-surgical, interventional procedures when successful avoid the necessity of major surgical operations. However, there is one common problem associated with all of these non-surgical procedures. Namely, the potential release of embolic debris into the bloodstream can occlude the distal vasculature and cause significant health problems for the patient. In one example, during deployment of a stent, it is possible that the metal struts of the stent cut into the stenosis and shear off pieces of plaque which become embolic debris that travel downstream and lodge somewhere in the patient's vascular system. In another example, pieces of plaque can sometimes dislodge from the stenosis during a balloon angioplasty procedure and become released into the bloodstream. In yet another example, while complete vaporization of plaque is the intended goal during a laser angioplasty procedure, quite often particles are not fully vaporized and thus enter the bloodstream. Likewise, not all of the emboli created during an atherectomy procedure are drawn into the vacuum catheter and, as a result, enter the bloodstream as well.
When any of the above-described procedures are performed in the carotid or like arteries, the release of emboli into the circulatory system can be extremely dangerous and sometimes fatal to the patient. Debris that is carried by the bloodstream to distal vessels of the brain can cause these cerebral vessels to occlude, resulting in a stroke, and in some cases, death. Therefore, although cerebral percutaneous transluminal angioplasty has been performed in the past, the number of procedures performed has been limited due to the justifiable fear of causing an embolic stroke.
Medical devices have been developed in an effort to resolve the problem created when debris or fragments enter the circulatory system following vessel treatment using any one of the above-identified procedures. One approach which has had some limited success is the placement of a filter or trap downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. Again, there have been problems associated with such filtering systems, particularly during the expansion and collapse of the filter within the body vessel. If the filtering device does not have a suitable mechanism for closing the filter, there is a possibility that trapped embolic debris can backflow through the inlet opening of the filter and enter the bloodstream as the filtering system is collapsed and removed from the patient. The backflow is caused by the act of collapsing the filter device, which then squeezes trapped embolic material through the opening of the filter and back into the bloodstream.
Many of the prior art filters that can be expanded within a blood vessel are attached to the distal end of a guide wire or guide wire-like tubing. The guide wire or guide wire-like tubing allows the filtering device to b
Boylan John F.
Huter Scott J.
Advanced Cardiovascular Systems Inc.
Fulwider Patton Lee & Utecht LLP
Ho (Jackie ) Tan-Uyen T.
Milano Michael J.
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