Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
2000-09-12
2003-01-28
Calvert, John J. (Department: 3765)
Surgery
Instruments
Internal pressure applicator
Reexamination Certificate
active
06511496
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of percutaneous transluminal treatment of stenosed or narrowed arteries in the human vascular system. More particularly, the invention is directed to an embolic protection device for capturing particles dislodged from a stenosis during an interventional procedure performed to improve blood flow through the stenosed artery.
Arteries can become stenotic in a number of ways. Often, a stenosis or lesion forms due to an accumulation of atherosclerotic plaque on the walls of a blood vessel. Atherosclerotic plaque is typically a hard calcified substance, particles of which tend to dislodge during interventional procedures and flow freely in the circulatory system. A stenosis also may form from an accumulation of thrombus material which is typically softer than atherosclerotic plaque, but can nonetheless cause restricted blood flow in the lumen of a vessel. Like atherosclerotic plaque, thrombus material also tends to dislodge during interventional procedures. As used here, the term emboli refers to free flowing particulates whether composed of plaque or thrombus material. Such free flowing emboli are dangerous since they may become lodged in a small blood vessel and occlude or partially occlude the vessel.
Various approaches have been developed to treat a stenotic lesion in the vasculature. Among the most common are balloon angioplasty, laser angioplasty, and atherectomy. Balloon angioplasty is directed towards relieving the constriction in the artery by radially expanding the stenosis against the artery wall, while laser angioplasty and atherectomy attempt to remove the stenosis from the artery.
In a typical balloon angioplasty procedure, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient through the femoral artery by means of a conventional Seldinger technique and advanced within a patient's vascular system until the distal end of the guiding catheter is positioned at a point proximal to the lesion site. 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 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 lesion. Once in position, 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 and expand the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation catheter may be withdrawn from the patient's vasculature. Blood flow is then 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.
The procedures for laser angioplasty and atherectomy are similar to that of balloon angioplasty in that a guiding catheter is introduced into the patient's vasculature through a conventional Seldinger technique and a guide wire is typically advanced through the guiding catheter and across an arterial lesion to a point distal of the lesion. However, in laser angioplasty, a high intensity laser is used to ablate the lesion by superheating and vaporizing the stenotic matter rather than expanding the lesion with a balloon. In atherectomy, a specialized catheter containing rotating cutting blades is used to mechanically cut or abrade the stenosis from the artery wall.
With all of the above procedures, the treated artery wall suffers a degree of trauma and in a small percentage of cases may abruptly collapse or may slowly narrow over a period of time. To prevent either of these conditions, the treatment procedure may be supplemented by implanting within the arterial lumen a prosthetic device known as a stent. A stent is a small tubular metallic structure which is fitted over a catheter balloon and expanded at the lesion site. Stents serve to hold open a weakened blood vessel and prevent the blood vessel from narrowing over time.
Balloon angioplasty, laser angioplasty, atherectomy, and stenting procedures have proven successful and are widely used in the treatment of stenosis of the coronary arteries and have, for many patients, eliminated the need for invasive bypass surgery. However, all of the above procedures tend to create embolic particles which in certain critical arteries, such as the carotid arteries, can create a significant risk of ischemic stroke. For this reason, these beneficial techniques have not been widely used in treating the carotid arteries.
Embolic particles may be created during an angioplasty procedure since stenoses formed from hard calcified plaque tend to crack upon radial expansion. Upon cracking, emboli will be released into a patient's bloodstream. Emboli may be formed during a stent placement procedure as well when the lesion is cracked since the metal struts of the stent may cut into the stenosis shearing off plaque or thrombus material. In laser angioplasty, complete vaporization of the stenosis is the intended goal of the procedure. In practice however, not all particles from the stenosis are vaporized during the laser ablation process and thus some particles enter the bloodstream. During an atherectomy procedure, a constant stream of particles is cut from the stenosis. Typically a suction catheter is used to capture these particles. However, it is often necessary to pull a high vacuum in order to remove all debris created by the cutting process. In some circumstances, it is not possible to pull a high enough vacuum to remove all debris without causing radial collapse of the weakened artery. Thus, some particles will not be drawn into the suction catheter and will flow downstream as emboli.
Numerous embolic filters or traps for deployment distal of a lesion site have been proposed. Some of these devices use a form of woven wire mesh basket to capture emboli. A typical example of the wire mesh basket type of intravascular filter is described in U.S. Pat. No. 4,873,978, entitled “Device and Method for Emboli Retrieval” issued to Ginsburg. Ginsburg discloses a removable vascular filter permanently attached to a guide wire for deployment from a catheter. The filter is comprised of an expandable wire mesh basket employing diamond shaped cells. Upon deployment, the filter expands to contact the walls of the lumen, thereby straining emboli found in the blood flow of the lumen.
A variation of the wire mesh basket approach is described in U.S. Pat. No. 5,152,777, entitled “Device and Method for Providing Protection From Emboli and Preventing Occlusion of Blood Vessels” issued to Goldberg et al. This device consists of a filter having of a plurality of resilient, stainless steel wire arms joined at one end so as to form a conical surface and having rounded tips at their other ends to prevent damage to the vessel walls. Each arm is wound with wire in a form similar to a coil spring. Goldberg proposes that emboli entrained in blood flowing past the spring arms will be caught in the coils of the arms.
Prior art wire mesh filters have several drawbacks. The most significant of which is the relatively large cell size of the mesh. Embolic particles with nominal diameters smaller than 150 microns can still pose a serious risk of occluding or partially occluding fine vasculature. A very fine wire mesh basket may have cells with openings as large as 3000-4000 microns. Thus, wire mesh filters may not be able to trap small embolic particles and therefore may be unsuitable during the treatment of lesions in the carotid arteries where any emboli produced by an interventional procedure have a short flow path to the fine vasculature of the brain.
Other devices for capturing emboli in blood flowing in a patient's va
Huter Benjamin C.
Huter Scott J.
Steadham Christopher L.
Advanced Cardiovascular Systems Inc.
Calvert John J.
Fulwider Patton Lee & Utecht LLP
Hurley Shaun R
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