Surgery – Diagnostic testing – Flexible catheter guide
Reexamination Certificate
2000-02-16
2002-04-23
Lacyk, John P. (Department: 3736)
Surgery
Diagnostic testing
Flexible catheter guide
C604S523000, C604S530000, C600S435000
Reexamination Certificate
active
06375628
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention generally relates to surgical device design and fabrication and, more particularly, to hollow medical wires used as guidewires, catheters, and the like, and methods of constructing same.
2. Description of the Related Art
In the medical community, the continuing trend of less-invasive and noninvasive surgical techniques is driving the medical industry to explore new materials and processes for fabricating surgical instruments and devices having smaller size and better material properties. Examples of such instruments include angioplasty catheters incorporating balloons to dilate an occluded blood vessel. Other catheters are used to deploy stents or other types of therapeutic devices.
Because of the success and acceptance of procedures which utilize such catheters, new procedures are being developed which require variations and adaptations of previous catheter technology. For example, in the U.S., one of the more common applications for medical catheter technology is the “over-the-wire” balloon angioplasty catheter. In this application, the catheter is comprised of an elongate hollow body which has mounted on its distal end an inflatable therapy balloon. The catheter body in this case is typically constructed from a plastic material and is hollow (e.g., sometimes referred to as “microtubing”), both to supply inflation fluids to the balloon and to allow the catheter device to ride over a thin wire to the site to be treated. Thus, this medical device is referred to as an “over-the-wire” therapy catheter.
The thin wire over which the catheter rides is commonly referred to as a “guidewire,” obviously, because it guides the therapy balloon to the treatment location. Such medical guidewires are typically made from a solid construction, i.e., they are not normally hollow since they do not need to carry fluids to the therapy site. Such medical wires can be adapted to guide other types of therapy devices well, such as stents, atherectomy devices, laser devices, ultrasound devices, drug delivery devices, and the like.
Another type of balloon angioplasty device is referred to as a “single operator” balloon catheter. More common in Europe, this type of device rides along a guidewire with only a short section of the device (i.e., the “single operator”) actually riding completely over with the guidewire.
Another type of therapy balloon device which does not require a guidewire is referred to as a “balloon-on-a-wire” or a “fixed-wire balloon” catheter. The body of the catheter in this case is typically a hollow metallic wire (e.g., a “hypotube”) or plastic wire, providing inflation fluid to the balloon mounted on the distal end. This type of therapy balloon device is less common in the U.S., being used in about less than 5% of the angioplasty procedures which are performed, compared with both over-the-wire and single operator type therapy balloon catheters which are used about 70% and 25% of the time, respectively.
In order to successfully perform the desired therapy using present catheter technology, there are a number of functional requirements which guidewires must exhibit. These are, not in any particular order of importance, as follows: pushability; trackability; torqueability; flexibility; and handleability. To the extent that a medical guidewire (or a guiding catheter or another similar guiding devices) exhibits one or more of these functional characteristics, it is more likely to be successful, both medically and commercially.
Pushability refers to the ability of a medical guidewire to be efficiently and easily pushed through the vasculature of the patient without damage thereto, but also without getting hung up, blocked, kinked, etc. Excessive force should not be necessary. The relative stiffness or rigidity of the material from which the wire is made is a key mechanical feature of the wire, at least with respect to its pushability. That is, the wire must be stiff enough to be successfully and efficiently pushed through the vessels to the treatment site, but not too stiff to cause damage. Likewise, a guidewire that is not sufficiently stiff or rigid will suffer “prolapse.” This condition occurs when the wire bends over on itself or strays down a branching vessel without progressing to its intended site. Thus, a wire that is too limp lacks sufficient strength to have good pushability characteristics, which are important in virtually all guidewire applications.
Trackability, in the case of guidewires, refers to the ability of the wire to have another device, such as a therapy catheter, efficiently pushed over it to a particular location. Thus, this is also an important feature of catheters which must also “track” efficiently over a guidewire. Time is usually of the essence with respect to many noninvasive therapy procedures since the blood flow of the patient may be interrupted partially or wholly, during such therapy. In addition, there are often a number of “exchanges” during such procedures in which one over the wire device is removed and replaced with another—both riding on the same guidewire. Thus, the ability of the guidewire to provide good tracking characteristics is important to the success of the wire. Again, the stiffness of the wire plays an important role in its trackability characteristics. Also, the lubricity of the material from which the wire is made will enhance its trackability by reducing frictional forces.
Torqueability refers to the ability of a medical wire to be accurately turned or rotated. It is often important, in traversing bends or turns, that the wire be rotated into a certain position. Ideally, a guidewire should exhibit 1:1 torqueability characteristics; for example, a one-quarter turn by the physician at the proximal end should result in precisely a one-quarter turn in the wire at the distal end. As one may expect, such ideal torqueability is very difficult to achieve in present medical wire technology.
Flexibility is another important characteristic of medical wires. It relates to the ability of the wire to follow a tortuous path, i.e., winding and bending its way through the tight turns of a patient's vasculature. Small radius turns are found especially in the coronary arteries. Furthermore, diseased blood vessels become even more tortuous. For example, if plastic deformation in the wire results from traversing smaller, tight radius turns, the rigidity of the wire will be reduced. In addition, due to the permanent deformation, the straightness of the material is lost. It is therefore more likely to kink or possibly even break. Moreover, if the distal tip is bent, upon rotation, an injurious effect known as “whipping” occurs as the distal tip of the wire beats against the inner wall of the vessel. Thus, the ability of a guidewire to traverse such tortuous paths without kinking, deformation, or damage to the vessel walls, is very important.
The handleability of medical wire relates to its feel during use. Especially important are reduced functional characteristics, such that the physician can actually “feel” the tip as it is manipulated (including both torquing and pushing) from the proximal end. The therapeutic procedures using such wires require precise accuracy; thus, the movements of the wire must be smooth, controllable, and consistent. This is especially difficult to achieve in consideration of the long lengths of the wires (approximately 100 cm or more), and the fact that large sections remain outside the body while other sections are in the body and more or less hidden from view. Thus, it is important for the wire to be readily handled by the physician without kinking or requiring excessive forces or awkward movements.
It will also be noted that present guidewire technology also faces the challenge of extremely small dimensions. For example, guidewires used in therapeutic procedures performed in peripheral vessels often have an outer diameter of about 0.035 inches to around 0.038 inches. Wires used in connection with the coronary arteries are even smaller, ranging from
Bagaoisan Celso J.
Muni Ketan P.
Zadno-Azizi Gholam-Reza
Knobbe Martens Olson & Bear LLP
Lacyk John P.
Marmor, II Charles A.
Medtronic PercuSurge, Inc.
LandOfFree
Hollow medical wires and methods of constructing same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hollow medical wires and methods of constructing same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hollow medical wires and methods of constructing same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2924607