1. Field of the Invention
The present invention is directed to expandable abrasive/cutting heads for rotation atherectomy devices.
2. Description of the Related Art
Atherectomy is a non-surgical procedure to open blocked coronary arteries or vein grafts by using a device on the end of a catheter to cut or shave away atherosclerotic plaque (a deposit of fat and other substances that accumulate in the lining of the artery wall). For the purposes of this application, the term “abrading” is used to describe the grinding and/or scraping action of such an atherectomy head.
Atherectomy is performed to restore the flow of oxygen-rich blood to the heart, to relieve chest pain, and to prevent heart attacks. It may be done on patients with chest pain who have not responded to other medical therapy and on certain of those who are candidates for balloon angioplasty (a surgical procedure in which a balloon catheter is used to flatten plaque against an artery wall) or coronary artery bypass graft surgery. It is sometimes performed to remove plaque that has built up after a coronary artery bypass graft surgery.
Atherectomy uses a rotating shaver or other device placed on the end of a catheter to slice away or destroy plaque. At the beginning of the procedure, medications to control blood pressure, dilate the coronary arteries, and prevent blood clots are administered. The patient is awake but sedated. The catheter is inserted into an artery in the groin, leg, or arm, and threaded through the blood vessels into the blocked coronary artery. The cutting head is positioned against the plaque and activated, and the plaque is ground up or suctioned out.
The types of atherectomy are rotational, directional, and transluminal extraction. Rotational atherectomy uses a high speed rotating shaver to grind up plaque. Directional atherectomy was the first type approved, but is no longer commonly used; it scrapes plaque into an opening in one side of the catheter. Transluminal extraction coronary atherectomy uses a device that cuts plaque off vessel walls and vacuums it into a bottle. It is used to clear bypass grafts.
Performed in a cardiac catheterization lab, atherectomy is also called removal of plaque from the coronary arteries. It can be used instead of, or along with, balloon angioplasty. Atherectomy is successful about 95% of the time. Plaque forms again in 20-30% of patients.
Several devices have been disclosed that perform rotational atherectomy. For instance, U.S. Pat. No. 5,360,432, issued on Nov. 1, 1994 to Leonid Shturman, and titled “Abrasive drive shaft device for directional rotational atherectomy” discloses an abrasive drive shaft atherectomy device for removing stenotic tissue from an artery, and is incorporated by reference herein in its entirety. The device includes a rotational atherectomy apparatus having a flexible, elongated drive shaft having a central lumen and a segment, near its distal end, coated with an abrasive material to define an abrasive segment. At sufficiently high rotational speeds, the abrasive segment expands radially, and can sweep out an abrading diameter that is larger than its rest diameter. In this manner, the atherectomy device may remove a blockage that is larger than the catheter itself. Use of an expandable head is an improvement over atherectomy devices that use non-expandable heads; such non-expandable devices typically require removal of particular blockages in stages, with each stage using a differently-sized head.
In the years since the '432 patent, there has been a significant effort to improve the expandable head, with many devices using centrifugal force or other devices to drive portions of the abrasive head radially outward at high rotational speeds.
For all of these devices, the abrasive head includes an abrasive that has a single set of properties. For instance, an abrasive burr may include abrasive particles of a particular size or a particular distribution of sizes. Or, a particular head may have a cutting effect on the blockage, rather than a grinding effect.
There may be some instances when a practitioner requires two different abrading heads for a single blockage. For instance, a particular blockage may have hard plaques, which may be effectively removed by sanding or scraping, as well as soft lesions, which may be effectively removed by slicing or cutting. The cutting head may have different properties than the scraping head.
If a practitioner wants to use a first abrasive, then use a second abrasive having different properties than the first abrasive, the practitioner must remove the device with the first abrasive, then insert the device with the second abrasive. This removal of one catheter and insertion of another catheter is time-consuming, inconvenient, expensive, and requires additional parts that must be manufactured, shipped, inventoried, and maintained with the atherectomy device.
Accordingly, there exists a need for a rotational atherectomy abrading head that can exhibit two different sets of properties. Such a head would reduce the expense, time and burden of using additional heads for the rotational atherectomy device.